Events List for the Academic Year
Event Time:
Thursday, July 2, 2020 | 4:00 pm - 5:00 pm
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2020-07-02T16:00:00
2020-07-02T17:00:00
Stellar UV Light & the Origins of Life's Building Blocks
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Event Time:
Monday, June 29, 2020 | 3:00 pm - 4:00 pm
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2020-06-29T15:00:00
2020-06-29T16:00:00
Stellar Populations and the Structural Evolution of Galaxies
Event Information:
It is well established that galaxies are divided into those that are star-forming and those that have stopped forming stars long ago. The cessation of star formation in galaxies ("quenching") correlates strongly with galaxy structural properties, but the physical reasons remain disputed. I will discuss issues of correlation and causation, and highlight evidence from integral-field-unit surveys, hydrodynamical simulations and machine learning that point to multiple evolutionary pathways along which galaxies both grow and die.
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Event Time:
Thursday, June 25, 2020 | 4:00 pm - 5:00 pm
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2020-06-25T16:00:00
2020-06-25T17:00:00
Waves in volcanic and glacial conduits
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Geological fluid mechanics is a strange brand of physics: research problems often involve spatial scales that we can see and interact with directly, but dynamics that are 'hidden' in the sense that they involve timescales outside the human experience or initial and boundary conditions that are challenging to constrain. In this talk I will discuss a particular outstanding problem in volcano and glacier science: inferring the geometry of and fluid motion within conduit and crack structures beneath the surface of the Earth. In particular, I will discuss the phenomenology of fluid resonance in elastic-walled tubes and cracks containing stratified and bubbly fluids. I will first discuss seismic observations at Kilauea volcano, Hawaii, that are well explained by resonance in a coupled conduit-crack system. By studying long period ground surface displacements collected by seismometers around the volcanic vent, we learn about the shallow volcanic plumbing system structure and the properties of the bubbly magma within it. I will then talk about a more recent application of these ideas to glaciers, where the fluid and solid are different (water and ice compared to magma and rock), but the physical processes and basic science questions are similar.
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Event Time:
Monday, June 22, 2020 | 3:00 pm - 4:00 pm
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2020-06-22T15:00:00
2020-06-22T16:00:00
Mass ejection, compact objects, and electromagnetic transients
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Mass ejection is involved in the generation of many types of electromagnetic transient, often in the presence of at least one compact stellar object. A variety of processes can cause mass to become unbound from a gravitational field, including neutrino emission or absorption, magnetic stresses, angular momentum transport, or nuclear processes. In this talk I will discuss two astrophysical situations in which non-trivial mass ejection from the vicinity of a compact object should occur: the accretion disk formed in a neutron star merger, and failed supernovae that make black holes.
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Event Time:
Monday, June 22, 2020 | 8:30 am - 10:30 am
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2020-06-22T08:30:00
2020-06-22T10:30:00
“A linear Paul trap for barium tagging of neutrinoless double beta decay in nEXO”
Event Information:
Departmental Doctoral Oral Examination
Abstract:
nEXO is the next-generation Enriched Xenon Observatory searching for neutrinoless double beta decay (0νββ) in ¹³⁶Xe. If observed, 0νββ will validate neutrino to be its own anti-particle and determine the absolute mass scale of the neutrinos. nEXO's sensitivity is limited by the background level. Barium tagging is the ultimate background rejection method using the coincidence detection of ¹³⁶Ba as the daughter nucleus.
A linear Paul trap (LPT) is needed for the barium tagging concept in nEXO or a future gaseous experiment. The theory of an ideal LPT were studied from the first principles to obtain semi-analytical solutions of the trapped ions and to validate a simulation method. Then simulations were done to optimize the design of a realistic LPT. A setup of the designed LPT was manufactured. Meanwhile, prototypes of key components of the LPT were built for the experimental developments. A prototype of the LPT's quadrupole mass filter (QMF) achieved mass resolving power m/Δm≈140, exceeding the requirement. A 3D printed prototype of the ion cooler demonstrated successful ion cooling, trapping and ejection. Based on the progress with the prototypes, improvements were made to the LPT design and have been included in the final setup. The final LPT will be installed between an RF funnel and a multi-reflection time-of-flight mass spectrometer for detailed study of barium ion extraction and identification from gaseous or liquid xenon.
Event Location:
via Zoom
Event Time:
Thursday, June 18, 2020 | 4:00 pm - 5:00 pm
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2020-06-18T16:00:00
2020-06-18T17:00:00
Art, Outreach and Pattern Formation
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For the past several years, I have been experimenting with the boundary between art and science. The scientific field of pattern formation has developed a distinct aesthetic sensibility, informed by mathematics and physics, but inherently visual and dynamic. This aesthetic is an essential motivation for my work. This talk will describe my experiences with the "application" of pattern formation to making, exhibiting and discussing art. My experience shows that unmodified scientific images can be well received as art and generate wide-ranging conversations across traditionally separate disciplines. The art world offers an interesting venue for science outreach activities, as well as being a lot of fun to explore.
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Event Time:
Wednesday, June 17, 2020 | 12:00 pm - 3:00 pm
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2020-06-17T12:00:01
2020-06-17T15:00:00
Medical Physics Virtual Retreat
Event Information:
EVENT POSTPONED BY ONE WEEK TO JUNE 17, START TIME NOW NOON!
Please register for the event.
Preliminary Agenda:
12:00 - Welcome (Stefan Reinsberg)
Invited Speakers: four alumni of our program who are now practicing in industry, hospitals, and academy:
12:10-12:30 Dr. John Lucido (Mayo Clinic) - Clinical Therapy
12:30-12:50 Dr. Sandra Meyers (UC San Diego) - Academia / Clinical
12:50-13:10 Dr. Erin MacMillan (Philips Healthcare) - Industry
13:10-13:30 Dr. Henry Chen (MD Anderson) - Clinical Imaging
13:30-13:40 Break
Three-Minute-Research Competition1):
13:40-14:10 Competition Part A
Mohammad Salmanpour
Hybrid Machine Learning Methods for Robust Identification of Parkinson’s Disease Subtypes
Caleb Sample
Saving Saliva: accounting for parotid gland inhomogeneity in external beam radiotherapy treatment planning
Maryam Shirmohammad
Development of a Novel Raman Enhancement Technique for Breath Analysis for Lung Cancer Detection
Sarah Morris
Validating novel MRI techniques for measuring white matter microstructure
Yansong Zhu
Partial volume correction for brain PET imaging
Emilie Carpentier
Accurately modeling pan and tilt beam motion to assess the dosimetry of dynamic tumour tracking treatments on the Vero4DRT linear accelerator
Maryam Rostamzadeh
How to Hit a Moving Target
Jackie Yik
Comparison and Relationship of MRI biomarkers and serum neurofilaments in multiple sclerosis
Michelle Lam
Inhomogeneous Magnetization Transfer in Myelin and Intra-/Extra-cellular Water
14:10-14:30 Fun facts 2) presented by Shannon Kolind
14:30-14:50 Competition Part B
Connor Bevington
PET image quality can be improved through an iterative, MRI-assisted denoising algorithm
Justin Poon
Cardiac synchronized volumetric modulated arc therapy
Alexander Hart
Activity Optimization of FDG PET
Cassandra Miller
Beta and Alpha Imaging with 177Lu and 225Ac for Tumour Dosimetry
Swantje Moehle
Detector based quality assurance for eye plaque brachytherapy.
Lorna Tu
Faster myelin water imaging data analysis
Barry Bohnet
Optimization of Sparse GRASE MRI for Prostate Cancer
Helena Koniar
Assessing the Dosimetry and Biodistribution of Actinium-225 for Targeted Alpha Therapy
Aria Malhotra
Predict and Prevent Skin Reactions from Radiation
Competition & Fun facts results
Concluding remarks
1) Cash (!) prizes will be handed out for the winners of the three minute thesis competition! Judging criteria can be found here.
2) To lighten the mood amongst the staunchly serious bunch of Medical Physicists (not sure what the group noun is, a force of Medical Physicists?), we will play a game of “Match the fun fact to the fun Medical Physicist”.
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Event Time:
Tuesday, June 16, 2020 | 2:00 pm - 5:00 pm
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2020-06-16T14:00:00
2020-06-16T17:00:00
“Exploring Myelin Water Imaging: from Application to Atlas to Algorithm”
Event Information:
Departmental Doctoral Oral Examination
Abstract:
Myelin water imaging (MWI) is a quantitative magnetic resonance (MR) method that specifically measures the myelin content in the central nervous system. MWI operates on the principle that the MR signal of water trapped between myelin bilayers can be extracted from the total MR signal based on a characteristic short T2 relaxation time. The ratio of myelin water signal relative to the total signal is termed myelin water fraction (MWF), used as a quantitative biomarker for myelin. This thesis explores three aspects of MWI: application, atlas, and algorithm.
Firstly, the MWI was applied to study cervical spondylotic myelopathy (CSM), which is a common spinal cord neurodegenerative disease. The function of the spinal cord conduction was assessed by an electrophysiologic technique called somatosensory evoked potentials (SSEP). Significant MWF reduction was observed in those CSM patients with functional deficits (e.g. delayed SSEP latency). A linear correlation between the MWF and the SSEP latency was discovered in CSM.
Secondly, the MWI atlases, which represent the MWI normative references of the normal myelin distribution in the brain and spinal cord, were created by coregistering and averaging the MWI images acquired from many healthy volunteers. These resulting atlases were utilized to demonstrate areas of demyelination in individuals with pathological conditions such as multiple sclerosis. The MWI atlases have been uploaded on the Internet and made publicly available.
Thirdly, the current MWI data analysis, based on the non-negative least squares (NNLS) method, was accelerated by implementing the neural network (NN) algorithm. A NN model was trained by the ground truth labels produced by the commonly used NNLS method. The trained NN model achieved to yield a whole-brain MWF map in 33 seconds, which is 150 faster than the NNLS method.
Finally, a novel T2 data analysis method, namely the spectrum analysis for multiple exponentials via experimental condition oriented simulation (SAME-ECOS), was proposed. SAME-ECOS is a simulation-derived solver that tailored for different MR experimental conditions. When dealing with the MWI data, it is found that SAME-ECOS largely surpassed the NNLS method in terms of calculation accuracy and speed.
Event Location:
via Zoom
Event Time:
Monday, June 15, 2020 | 3:00 pm - 4:00 pm
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2020-06-15T15:00:00
2020-06-15T16:00:00
Messages from THOR about Galactic magnetism
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The HI/OH/Recombination line (THOR) survey of the Milky Way is a comprehensive survey of neutral atomic, molecular and ionized gas in the inner Galaxy. THOR provides higher angular resolution and a much wider bandwidth (JVLA L-band) than similar Galactic plane surveys. These are important assets to explore the crowded inner Milky Way. THOR provides us with images of HI, OH, and hydrogen radio recombination lines, as well as the 1-2 GHz continuum with spectral index and linear polarization. Linear polarization as a function of frequency allows us to measure Faraday rotation, the most effective tool for exploring magnetic fields in the Milky Way over a wide range of scales. I will introduce the technique called Faraday Rotation Measure Synthesis, with emphasis on new science that is made possible by this technique. THOR has revealed to us a region of very strong Faraday rotation in the Sagittarius arm of the Milky Way. I will present an update on this work, as well as some new results related to the Galactic Magnetic field on scales of a kpc or less.
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Event Time:
Thursday, June 11, 2020 | 4:00 pm - 5:00 pm
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2020-06-11T16:00:00
2020-06-11T17:00:00
Show and Tell (episode III)
Event Information:
Hear what some members of our Department have been doing during lockdown.
Coree Laule "The Daily Muffin: Life of a Quarantined Bunny"
Raelyn Sullivan "Timelapse photography"
Adam Dong "Adam's thrifty guide to high-performance PC hardware for physicists"
Perrin Waldock "A magic trick"
Natalie Ho "The limits of figure skating"
Carolin Hofer "The art of living a happy life"
Jess McIver "What I learned during #ShutdownSTEM"
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Event Time:
Monday, June 8, 2020 | 3:00 pm - 3:30 pm
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2020-06-08T15:00:00
2020-06-08T15:30:00
Carbon stars as standard candles: The luminosity function of carbon stars in the Magellanic Clouds
Event Information:
Our goal is to derive a carbon-star luminosity function that will eventually be used to determine distances to galaxies at 50–60 Mpc and hence yield a value of the Hubble constant. Cool N-type carbon stars exhibit redder near-infrared colours than oxygen-rich stars. Using Two Micron All Sky Survey near-infrared photometry and the Gaia Data Release 2, we identify carbon stars in the Magellanic Clouds (MC) and the Milky Way (MW). Carbon stars in the MC appear as a distinct horizontal feature in the near-infrared colour–magnitude diagram. We build a colour selection and derive the luminosity function of the colour-selected carbon stars. We find the median absolute magnitude and dispersion, in the J band, for the Large and the Small Magellanic Clouds (LMC/SMC) to be, respectively, (M_J=−6.284+/-0.004 and sigma=0.352+/-0.005) and (M_J=−6.160+/-0.015 and sigma=0.365+/-0.014). The difference between the MCs may be explained by the lower metallicity of the SMC, but in any case it provides limits on the type of galaxy whose distance can be determined with this technique. To account for metallicity effects, we developed a composite magnitude, named C, for which the error-weighted mean C magnitude of the MC are equal. Thanks to the next generation of telescopes (JWST, ELT, and TMT), carbon stars could be detected in MC-type galaxies at distances out to 50–60 Mpc. The final goal is to eventually try and improve the measurement of the Hubble constant while exploring the current tensions related to its value.
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Event Time:
Thursday, June 4, 2020 | 4:00 pm - 5:00 pm
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2020-06-04T16:00:00
2020-06-04T17:00:00
Hacking Science: Hack Weeks as a Model for Education and Collaboration in Data-Intensive Research
Event Information:
Across many scientific disciplines, including physics and astronomy, methods for recording, storing and analyzing data are rapidly increasing in complexity. Skillfully using data science tools that manage this complexity requires training in new programming languages and frameworks, as well as immersion in new modes of interaction that foster data sharing, collaborative software development and exchange across disciplines. Learning these skills from traditional university curricula can be challenging because most courses are not designed to evolve on time scales that can keep pace with rapidly shifting data science methods. In this talk I will introduce the concept of a hack week as a novel and effective model offering opportunities for networking and community building, education in state-of-the-art data science methods and immersion in collaborative project work. I will present some examples of how hack weeks have been implemented across a number of scientific disciplines, including astronomy, show results from both hack projects and evaluation efforts, and share some practical advice for implementation, with a focus on fostering welcoming and positive spaces for a diverse group of participants throughout these events.
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Event Time:
Thursday, June 4, 2020 | 2:00 pm - 3:00 pm
Event Location:
Zoom Meeting ID: 918 1320 7475
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2020-06-04T14:00:00
2020-06-04T15:00:00
CM seminar : Cavity-mediated spin readout in an industrial silicon transistor
Event Information:
Abstract: Spin-based quantum bits in silicon are an exciting platform for processing of quantum information. Silicon materials host some of the most coherent quantum two-level systems ever measured [1], and qubits can be manipulated and measured accurately in devices that resemble classical transistors [2]. An often-overlooked aspect of quantum devices is the problem of reading out many qubits on a single chip, which is important not just to extract information about the quantum states on the chip, but in the future, to correct errors that occur when qubits are manipulated. In this seminar I will discuss the first projective measurement of coupled spins bound to dopant atoms in the channel of an industrially fabricated transistor. This was performed by inducing a spin-dependent motion of a hole spin from one impurity to another using the transistor’s gate electrode [3], and detecting the motion with the aid of a miniature cryogenic radio-frequency cavity [4]. Strategies for reaching and exceeding the Heisenberg limit of measurement accuracy using similar techniques will be discussed.
1. Saeedi et al, Science, 2013, 342, pg. 830
2. Muhonen et al, Nature Nanotech, 2014, 9, pg. 986, Veldhorst et al, Nature Nanotech, 2014, 9, pg. 981.
3. Van der Heijden et al, Nano Letters 2014, 14, pg. 1492, Van der Heijden et al, Science Advances, 2018, 4, eaat9199.
4. Petersson, Nano Letters, 2010, 10, pg. 2789.
Event Location:
Zoom Meeting ID: 918 1320 7475
Event Time:
Thursday, June 4, 2020 | 9:00 am - 11:00 am
Event Location:
(Virtual Defence)
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2020-06-04T09:00:00
2020-06-04T11:00:00
"Correlated Phenomena Studied by ARPES: From 3d to 4f Systems”
Event Information:
Final PhD Oral Examination
Abstract:
The physics of strongly correlated materials is at the heart of current condensed matter research. The inclusion of interactions in these materials between electron themselves or with other excitations intertwines various degrees of freedom (orbital, spin, charge and lattice), leading to a number of novel phenomena like Mott-Hubbard and charge-transfer insulators, high-temperature superconductivity and mixed-valence and Kondo physics. This thesis focuses on the study of two classes of correlated materials: copper-oxide high-temperature superconductors, whose correlated physics is driven by the localized nature of the half-filled Cu 3d-orbitals, and the rare-earth hexaborides, which are characterized by the strongly correlated 4f-shell.
Recently, it has been shown that the interplay between different mechanisms underlying the formation of the superconducting condensate in the hole-doped bi-layer Bi2Sr2CaCu2O8+d can be addressed in the time domain by means of time- and angle-resolved photoemission spectroscopy (TR-ARPES). Using this technique, the primary role of phase coherence has been established. By exploiting the same dynamical experimental approach, we show that such scenario also describes the ultrafast collapse of superconductivity in the single-layer compound Bi2Sr2CuO6+d. Moreover, by performing a comprehensive study on different doping levels of both single- and bi-layer compounds, we provide new insights on the temperature evolution of the nodal quasiparticle spectral weight.
The second part of the thesis focuses on electron-doped cuprates, addressing the putative relation between the spectroscopically observed pseudogap and the robust antiferromagnetic order. Employing TR-ARPES as a tool to perform a detailed temperature dependent investigation allows us to explicitly link the momentum-resolved pseudogap spectral features to the evolution of the short-range spin-fluctuations in the optimally-doped Nd2-xCe2CuO4.
Lastly, we make use of chemical substitution to investigate the mixed valent character of the rare-earth hexaboride SmxLa1-xB6 series. Our combined ARPES and x-ray absorption measurements reveal a departure from a monotonic evolution of the Sm valence as a function of x and the possible emergence of a mixed-valent impurity regime.
Event Location:
(Virtual Defence)
Event Time:
Monday, June 1, 2020 | 3:00 pm - 3:30 pm
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2020-06-01T15:00:00
2020-06-01T15:30:00
Galaxy cluster mass estimation with deep learning and hydrodynamical simulations
Event Information:
We evaluate the ability of Convolutional Neural Networks (CNNs) to predict
galaxy cluster masses in the BAHAMAS hydrodynamical simulations. We train
four separate single-channel networks using: stellar mass, soft X-ray
flux, bolometric X-ray flux, and the Compton y parameter as observational
tracers, respectively. Our training set consists of ~6400 synthetic
cluster images generated from the simulation, while an additional ~1600
images form a test set. We also train a "multi-channel" CNN by combining
the four observational tracers. The cluster masses predicted from these
networks are evaluated using the average fractional difference between
predicted cluster mass and true cluster mass. The resulting predictions
are especially precise for halo masses in the range
10^13.25 to 10^14.5 MSun, where all five networks
produce mean mass biases of order ~1% with a scatter on the mean bias of
~0.5%. The network trained with Compton y parameter maps yields the most
precise predictions. We interpret the network's behaviour using two
diagnostic tests to determine which features are used to predict cluster
mass. The CNN trained with stellar mass images detect galaxies (not
surprisingly), while CNNs trained with gas-based tracers utilise the shape
of the signal to estimate cluster mass.
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Event Time:
Thursday, May 28, 2020 | 4:00 pm - 5:00 pm
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2020-05-28T16:00:00
2020-05-28T17:00:00
Improbable Research and the Ig Nobel Prizes
Event Information:
Marc Abrahams has been editor of the Journal of Irreproducible Results and its successor the Annals of Improbable Research, as well as the force behind the annual Ig Nobel Prize celebration. He will take us through some examples of research topics that are amusing and at the same time enlightening, demonstrating that the most important phrase in science is "that's funny!"
For more information see www.improbable.com
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Event Time:
Thursday, May 28, 2020 | 2:00 pm - 3:00 pm
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2020-05-28T14:00:00
2020-05-28T15:00:00
The BeEST Experiment: A Search for keV-Scale Neutrinos in the EC Decay of 7Be with Superconducting Quantum Sensors
Event Information:
The search for sterile neutrinos is among the brightest possibilities in our quest for understanding the microscopic nature of dark matter in our universe. Sterile neutrinos - unlike the active neutrinos in the SM - do not interact with normal matter as they move through space, and as such must be observed via their mass-generated effects that result from momentum conservation with SM particles. One way to observe these momentum recoil effects experimentally is through high-precision measurements of electron-capture (EC) nuclear decay, where the final state only contains the neutrino and a recoiling atom. This approach a powerful method for BSM neutrino mass searches since it relies only on the existence of a heavy neutrino admixture to the active neutrinos, which is a generic feature of neutrino mass mechanisms, and not on the model-dependent details of their interactions. In this talk, I will discuss our first measurements in the Beryllium EC STJ (BeEST) experimental program, which uses the decay-momentum reconstruction technique to precisely measure the 7Li recoil spectrum following the EC decay of 7Be implanted into sensitive superconducting tunnel junction (STJ) radiation detectors.
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Event Time:
Wednesday, May 27, 2020 | 2:00 pm - 4:00 pm
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2020-05-27T14:00:00
2020-05-27T16:00:00
“Leveraging the Light-Matter Interaction in Angle-Resolved Photoemission Spectroscopy”
Event Information:
Departmental Oral Examination
Abstract:
The light-matter interaction is central to the photoemission process, with an ultraviolet photon providing the necessary impulse required to eject those electrons which we collect in an effort to understand the electronic structure of matter. As such, the selection rules associated with this interaction impose strict constraints on those electronic orbits to which the technique is sensitive. Photoemission-based techniques then present an opportunity to access information beyond spectroscopic characterization of a material’s level structure; an orbital description of the underlying wavefunctions is viable under consideration of the photoemission mechanism. We present here a numerical scheme within which such information about the photoemission experiment can be garnered, with specific application to several experiments on candidate materials. In particular, this methodology allows for new insights in the problem of the Fe-based superconductors. These materials are an ideal platform to apply this methodology. The low energy electronic structure is characterized by a large number of closely spaced, moderately correlated states. Their phenomenology is dictated by a delicate balance of several interactions with similar energy scales, the competition and cooperation amongst which pose a considerable challenge for both theory and experiment. The kinetic Hamiltonian, in addition to interactions involving Coulomb and Hund’s coupling, as well as nematic order and spin-orbit coupling are all closely related to the orbital structure of the electronic states. The unique sensitivity to both spin and orbital degrees of freedom which photoemission provides therefore allow for a comprehensive exploration of such energy scales in these compounds. Taking advantage of this senstivity, we have mapped the momentum and enegy dependence of spin-orbit entanglement in candidate materials FeSe and LiFeAs.
Despite the remarkable surface sensitivity which limits access to the crystal bulk in photoemission, there is a strong inclination to assert a correspondence between the bulk electronic structure, and that measured experimentally. Such
a connection is by no means guaranteed, and is frequently the cause of misinterpretation. We explore the surface issue in detail, and discover an interference mechanism which provides justification for the unanticipated success of valenceband photoemission in quasi two-dimensional materials. The surface issue is of specific relevance to the Fe-superconductors, where certain orbitals exhibit significant dispersion perpendicular to the surface. We examine the canonical Fesuperconductor LiFeAs, wherein a confluence of three-dimensional dispersion, spin-orbit coupling, and surface states have conspired to preclude identification of the low-energy electronic structure. We combine detailed photon-energy dependent measurements with results from a slab-projected model to unambiguously identify the three-dimensional Fermi surface of this material.
Event Location:
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Event Time:
Monday, May 25, 2020 | 3:00 pm - 4:00 pm
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2020-05-25T15:00:00
2020-05-25T16:00:00
Science Highlights from the Zwicky Transient Facility
Event Information:
The Zwicky Transient Facility (ZTF) began its time-domain survey at Palomar Observatory in 2018. Thanks to its 47 square degree field of view and fast readout time, ZTF has since accumulated hundreds to thousands of epochs across the Northern Hemisphere sky, enabling searches for rare and fast evolving transients, variable stars, and solar system objects. I will describe the design and performance of ZTF and detail the surveys it has conducted. I will present science highlights from the first two years of the survey, including observations of young supernovae and discoveries of rare classes of compact binaries and asteroids. I will discuss plans for the second phase of ZTF, expected to begin this fall as well as implications for time-domain science with the Vera C. Rubin Observatory.
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Event Time:
Monday, May 25, 2020 | 9:00 am - 12:00 pm
Event Location:
Virtual Defence
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2020-05-25T09:00:00
2020-05-25T12:00:00
"Brain Network Pattern Analysis with Positron Emission Tomography Data: Application to Parkinson’s Disease”
Event Information:
Final PhD Oral Examination
Abstract:
Positron Emission Tomography (PET) is commonly used to investigate changes within the brain due to aging and disease. Because our brain works as an integrated system where multiple brain regions work together to perform complex tasks, net- work pattern analyses (a subset of machine-learning methods) were often found to provide complementary, more sensitive and more robust information compared to traditional univariate analyses, especially in the field of Magnetic Resonance Imaging (MRI). However, network pattern analysis has not been commonly used to study neurotransmitter changes using PET data. In addition, the emerging of multi-tracer imaging studies highlights the needs to develop novel joint analysis methods to ex- tract and combine complementary information from each imaging dataset to obtain a complete picture of the complex brain states. This thesis would be one of the first applications of such methods in the PET field.
Parkinsons disease (PD) is the second most common neurodegenerative disor- der with a long prodromal stage, and non-motor symptoms occur alongside or even before motor symptoms. Initially deemed to affect predominantly the dopamin- ergic system, PD is now deemed associated with alterations in several other non- dopaminergic neurotransmitter systems. Such changes, specific to PD, are some- times difficult to detect, especially in prodromal and early stages of the disease; the interactions between different disease-related mechanisms also remain largely unclear. In addition, the disease origin is unknown and there is current no effective cure for PD.
In this thesis work, we 1) explored spatial connectivity changes in the serotoner- gic system that are sensitive for detecting subtle changes in the prodromal and early disease stages and provide new insights into the mechanism of PD; 2) introduced Dynamic Mode Decomposition to extract spatio-temporal patterns of dopaminergic denervation for modeling disease progression; 3) introduced a novel joint pattern analysis approach to extract complementary information in the dopaminergic and serotonergic systems and their relationships with treatment response and treatment-induced complications. These novel methods not only lead to new understanding of PD, but also provided more sensitive tools for the analysis of PET data in a variety of clinical applications.
Event Location:
Virtual Defence