Events List for the Academic Year
Event Time:
Tuesday, July 18, 2023 | 10:00 am - 11:00 am
Event Location:
Hennings Building - Room 318
Add to Calendar
2023-07-18T10:00:00
2023-07-18T11:00:00
Ligo is Quantum
Event Information:
Since Bohr set out his interpretation of Quantum Mechanics which
separated small quantum systems from classical measuring systems, the question
as to whether or not there was a physical division between the quantum and the
classical. Is there some criterion which divides the world into quantum bits
and classical bits? Experiments are not answering the question. In particular
I will argue that the 40Kg mirrors of Ligo have already been shown to be
quantum by showing that that the quantum noise of Ligo arises from an
interference of non-commuting aspects of the laser light used to measure the
gravitational wave effect on the mirrors, and interference which would not be
there if the mirrors were classical objects.
Event Location:
Hennings Building - Room 318
Event Time:
Monday, July 17, 2023 | 3:00 pm - 4:00 pm
Event Location:
HENN 318
Add to Calendar
2023-07-17T15:00:00
2023-07-17T16:00:00
Improving the performance of GSpyNetTree during LIGO-Virgo observing run 4
Event Information:
Astro Colloquia for Summer 2023
* Summer undergraduate student talk will be ~20-30 minutes including Q&A
Event Location:
HENN 318
Event Time:
Monday, July 10, 2023 | 9:00 am - 11:00 am
Event Location:
https://ubc.zoom.us/j/66513543864?pwd=RXVQSFRFNTZINmMrZ3RJUXhHNHJXQT09
Add to Calendar
2023-07-10T09:00:00
2023-07-10T11:00:00
Longitudinal Relaxation Dynamics in White Matter: Experiments in NMR and MRI
Event Information:
MRI-based assessments of the human brain are critical for research, diagnosis and treatment of neurological disorders. Future clinical practice will demand accurate and consistent quantitative methodology alongside today’s qualitative image evaluations. Consequently, MRI research focuses on developing physical understanding of prevalent techniques and establishing new methods for efficient quantitative analysis. The brain’s complex structure complicates this goal. Myelin, a lipid-rich tissue aiding in signal transmission along axons in white matter, creates useful image contrast but also complicates the interpretation of measurements using canonical models. In this dissertation, we conduct experiments using solid-state NMR and in vivo MRI to examine assumptions in current MRI methods leading to potential quantitive errors. We propose improvements to these methods and an adaptation to an existing model.
A straightforward yet effective view of white matter is to separate proton populations into two pools, aqueous and non-aqueous, between which protons, and therefore magnetization, can exchange. This transfer can significantly affect the measured longitudinal relaxation (T1) depending on the preparation of each pool. First, we study the impact of adiabatic inversion pulses applied to white matter through NMR experiments on ex vivo brain samples and then compare these results to analogous in vivo experiments. We demonstrate that, contrary to common assumption, the non-aqueous pool is not saturated by typical adiabatic inversion pulses, although the aqueous pool is fully inverted, which results in bi-exponential longitudinal recovery. We compare this relaxation to that following hard and selective pulses, which are understood to result in mono- and bi-exponential recovery, respectively. Next, we perform NMR experiments on ex vivo brain samples using hard and selective pulses to initiate magnetization transfer demonstrating similar T1 biasing effects during Look-Locker and Variable Flip Angle sequences. We evaluate sources of systematic error pertinent to MRI applications. Finally, we modify the canonical Bloch-McConnell equations describing two-pool relaxation to incorporate fractional-order derivatives. We examine a numerical solution and provide an approximate analytical solution, which we use to model inversion recovery in heterogenous model systems, ex vivo, and in vivo brain. An additional fit parameter is introduced which may be used as a new contrast source.
Event Location:
https://ubc.zoom.us/j/66513543864?pwd=RXVQSFRFNTZINmMrZ3RJUXhHNHJXQT09
Event Time:
Friday, July 7, 2023 | 9:00 am - 5:00 pm
Event Location:
HENN Rooms 200 and 201
Add to Calendar
2023-07-07T09:00:00
2023-07-07T17:00:00
Frontiers in Biophysics Conference 2023
Event Information:
Frontiers in Biophysics (FiB) 2023 is an annual one-day conference in the Pacific Northwest covering all areas of quantitative biology and biophysics. FiB is a unique environment that brings together a wide variety of scientific disciplines and individuals from all experience levels to learn, present, and discuss biophysics research for the day, followed by a social event in the evening! If you are interested in attending FiB 2023 and wish to learn more about the program – or are interested in submitting an application to present a poster and/or 10-minute oral presentation – please follow the link below to this year’s website (https://fib2023.math.ubc.ca).
Event Location:
HENN Rooms 200 and 201
Event Time:
Monday, June 19, 2023 | 11:00 am - 2:00 pm
Event Location:
HENN 318
Add to Calendar
2023-06-19T11:00:00
2023-06-19T14:00:00
The GALEX-Gaia-EDR3 Catalogue of Single and Binary White Dwarfs
Event Information:
Abstract:
Abstract: We present a catalogue of white dwarf candidates constructed from the GALEX and Gaia EDR3 catalogues.
The catalogue contains 319,846 candidate white dwarf binary systems and 124,261 candidate single white dwarfs. Where available the catalogue is augmented with photometry from Pan-STARRS DR1, SDSS DR12 and classifications from StarHorse. We fit photometric data with modeled white dwarf cooling sequences to derive mass, age and effective temperature of the white dwarf as well as mass estimates for the companion. We test our classifications against StarHorse, the Gentile-Fusilo Gaia EDR3 catalogue, and white-dwarf-main-sequence binaries identified in SDSS DR12. This catalogue provides a unique probe of the binarity of white dwarfs as well as the abundance of white-dwarf giant binaries and large mass-ratio stellar binaries which are difficult to probe otherwise.
Event Location:
HENN 318
Event Time:
Thursday, June 15, 2023 | 9:00 am - 11:00 am
Event Location:
Hennings 318
Add to Calendar
2023-06-15T09:00:00
2023-06-15T11:00:00
A journey into computational protein design: Novel simulation methods development, physical origins of disease mutants, and therapeutic design for neurodegenerative diseases and COVID19
Event Information:
My research aims to advance the development pipeline of protein and peptide therapeutics from a biophysical perspective, and covers a spectrum of contributions from methodologies to applications. For methodology contributions, I have developed an unbiased molecular dynamics (MD) simulation tool, Reservoir REMD, and integrated it into GROMACS. It has been benchmarked and shown to give the same results for different initial conformations, even when starting the simulation from a kinetically trapped initial state. Res-REMD and other enhanced MD were used to calculate the dimer binding free energy of SOD1 to study how disease-associated mutations affect the binding. The results reveal that while the A4V mutation decreases the binding affinity, the D101N mutation does not. These findings challenge the hypothesis that dimer dissociation initiates the SOD1 misfolding that is known to contribute to ALS disease progression. For application-related contributions, I applied enhanced MD and free energy calculations to guide the design of vaccine immunogens for neurodegenerative diseases and mutation-robust therapeutics for COVID19. For neurodegenerative diseases, we designed flexible cyclic peptide immunogens to mimic the toxic oligomers such as tau in Alzheimer's disease or alpha-synuclein in Parkinson's disease. This approach, called "Glycindel scaffolding", can be extended to other protein misfolding diseases. For COVID19, we hypothesized that a conserved region on the spike S2 region could be scaffolded to become a mutation-robust vaccine. Through free energy calculations, I predicted that the S2 region could be exposed under unglycosylated conditions, and that the S2 region would be stable in the pre-fusion state. With this information, I used Rosetta to scaffold this S2 region, and predicted several constructs that have been successfully expressed and functional in wet-lab experiments. I also engineered ACE2-based decoys, the human receptor for SARS-CoV-2, as mutation-robust protein binders for spike RBD. Several engineered ACE2 decoys have been successfully expressed, showcasing the power of integrating machine-learning tools into protein design.
Event Location:
Hennings 318
Event Time:
Monday, June 12, 2023 | 11:00 am - 12:00 pm
Event Location:
Henn 318
Add to Calendar
2023-06-12T11:00:00
2023-06-12T12:00:00
Experimentally studying general relativity and black-hole physics with gravitational-wave observations
Event Information:
TALK RECORDING AVAILABLE AT: https://drive.google.com/file/d/1VU0khsZv5zqt4ZX04xZCkKzTpluNTdwg/view?usp=sharing
Abstract:
Since 2015, around 100 binary black-hole mergers have been detected by laser interferometer gravitational-wave detectors. Recently, the LIGO-VIRGO-KAGRA collaboration has started the O4 operation, with newly improved sensitivity thanks to quantum metrology techniques like frequency-dependent squeezing. Gravitational-wave observations allows us to make precision tests of general relativity, and confirm interesting predictions of general relativity in the strong-gravity regime. I will give an overview of such studies, and then focus on the oscillations of black holes.
Event Location:
Henn 318
Event Time:
Monday, June 12, 2023 | 10:00 am - 1:00 pm
Event Location:
https://ubc.zoom.us/j/61540621166?pwd=UGZDVkpiUTVmdEY5Qmtva2REVzVrQT09
Add to Calendar
2023-06-12T10:00:00
2023-06-12T13:00:00
Electron-phonon coupling in insulators beyond the Migdal limit
Event Information:
Motivated by the success of the momentum average (MA) approximation for the single-polaron and bipolaron cases, in this thesis we pursue the first generalization of this technique to the case of weakly-doped insulators beyond the Migdal limit. In search of a suitable starting point, we investigate the ground states of a variety of model Hamiltonians, inspired by real materials such as the rare-earth nickelates, polyacetylene, barium bismuthates, and buckminsterfullerene.
The ground state of the 2D nickelate sheet is found to exhibit cuprate-like orbital polarization unimpeded by weak to moderate electron-phonon coupling, lending further support to the proposal for Ni 3d^7 like superconductivity in nickelate thin films and heterostructures. Investigating polyacetylene leads to the development of a semi-analytical technique that can be used to account for zero-point lattice energy in determining the equilibrium geometry of any crystal. The study of a simplified, one-dimensional model of buckminsterfullerene results in the first generalization of MA to a system with two polaron clouds, and a phonon-driven mechanism for exciton dissociation that could be responsible for photocurrent generation in these strongly polar materials.
Because both the nickelates and polyacetylene turn out to be too complex as starting points for MA generalization, we focus on a simplified, s-p chain model of the barium bismuthates. We ultimately succeed in generalizing MA for this band insulator -- the first application of its kind. We compare the results to those from determinant quantum Monte Carlo to establish the accuracy of the MA results, obtained at lower computational cost.
Finally, we share in the development of the first open-sourced Python package implementing automatic MA equation generation via the GGCE method, which allows MA-style methods to be easily used by non-experts -- and is expected to expand to provide access to more existing MA methods in the future.
Event Location:
https://ubc.zoom.us/j/61540621166?pwd=UGZDVkpiUTVmdEY5Qmtva2REVzVrQT09
Event Time:
Thursday, June 8, 2023 | 11:00 am - 2:00 pm
Event Location:
HENN 302
Add to Calendar
2023-06-08T11:00:00
2023-06-08T14:00:00
Studies of Evolved Stellar Populations (From Giants to Remnants)
Event Information:
Abstract:
Superconducting transition-edge sensors (TES) carried by X-ray telescopes are powerful tools for the study of neutron stars, black holes and accreting white dwarfs. Our goal is to develop a low-computational-cost technique that optimizes energy and time resolution. TES exhibit a non-linear response with photon energy. Therefore, at low energies we focus on the current-pulse height whereas at high energies we consider the current-pulse width, to retrieve energy and arrival time of X-ray photons. For energies between 0.1 keV and 30 keV and with a sampling rate of 195 kHz, we obtain an energy resolution between 1.32 eV and 2.98 eV.
Measuring distances is crucial in astronomy. Using 2MASS near-infrared photometry and Gaia Data Release 2, we identify carbon stars in the Large Magellanic Clouds (LMC), Small Magellanic Cloud (SMC) and the Milky Way (MW). Carbon stars in the LMC/SMC appear as a distinct horizontal feature in the near-infrared colour-magnitude diagram. We derive the carbon-star luminosity function (CSLF) within a specific colour range. The CSLF will be key in measuring distances to galaxies at 50-60 Mpc and hence estimating a value of the Hubble Constant, thanks to the next generation of telescopes (JWST, ELT, TMT, GMT ).
We identify faint galactic white dwarfs thanks to their colours, in the Canada-France-Hawai‘i Telescope (CFHT) Large Area U-band Deep Survey (CLAUDS). The U-band and optical photometry allows us to fit for the physical properties of the white dwarfs, such as surface temperature, surface gravity, age, mass, and distance. We find a main mass peak consistent with halo and globular-cluster populations. Finally we derive a typical age of the MW stellar halo from our deep field white-dwarf catalogue.
Event Location:
HENN 302
Event Time:
Thursday, June 1, 2023 | 1:00 pm - 4:00 pm
Event Location:
HENN 302
Add to Calendar
2023-06-01T13:00:00
2023-06-01T16:00:00
A Detection of Cosmological 21 cm Emission from CHIME in Cross-correlation with the eBOSS Lyman-alpha Forest
Event Information:
Abstract:
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a radio telescope that we built to map the large-scale structure of the Universe between redshifts $0.8<z<2.5$, when dark energy is expected to begin the transition from a decelerating to an accelerating phase in its expansion. It was designed to perform an intensity mapping survey using the 21 cm line of neutral hydrogen, a novel method that has the potential to enable enormous surveys of the distant Universe, but also significant observational challenges to overcome.
I will describe how CHIME operates, and highlight some of my contributions to its data acquisition system and calibration effort, culminating in a detection of cosmological 21 cm emission in cross-correlation with measurements of the Lyman-alpha forest, at an average redshift $\bar{z} = 2.3$. Data collected by CHIME over 88 days in the 400-500~MHz frequency band ($1.8 < z < 2.5$) were formed into maps of the sky and high-pass delay filtered to suppress the foreground power. Line-of-sight spectra to the eBOSS background quasar locations were extracted from the CHIME maps and combined with the Lyman-alpha forest flux transmission spectra to estimate the 21 cm-Lyman-alpha cross-correlation function. Fitting a simulations-derived template to this measurement results in a $9\sigma$ detection significance.
Event Location:
HENN 302
Event Time:
Thursday, May 25, 2023 | 3:00 pm - 5:00 pm
Event Location:
https://ubc.zoom.us/j/68991164698?pwd=dzFGNVdPbSt4QldsVHNlWnJLL2ZWQT09 Passcode: 815209
Add to Calendar
2023-05-25T15:00:00
2023-05-25T17:00:00
Title: Boundaries, Braneworlds, and Black Holes: Applications of the AdS/BCFT Correspondence
Event Information:
Abstract: The AdS/CFT correspondence is a far-reaching equivalence between theories of quantum gravity in spacetimes with negative cosmological constant, such as anti-de Sitter (AdS) space, and lower-dimensional, non-gravitational quantum systems, such as conformal field theories (CFTs). In this thesis, we will use a version of AdS/CFT applicable to boundary conformal field theories (BCFTs) to investigate the physics of supersymmetric gauge theories, and to develop holographic models for cosmology and black hole physics. We make frequent use of an ansatz for holographic BCFT wherein AdS spacetime ends on a surface called an end-of-the-world (ETW) brane, and of the Ryu-Takayanagi (RT) formula for holographic entanglement entropy. We first study the $U(N)$ $\mathcal{N} = 4$ supersymmetric Yang-Mills (SYM) theory on a half space, with boundary conditions preserving scale invariance and half of the original supersymmetry. We calculate a conjectured RG-monotone called boundary $F$ for the most general such boundary conditions using the RT formula. In some cases, we perform an exact calculation using supersymmetric localization, and find exact agreement for the leading large $N$ term as a function of the ’t Hooft coupling $\lambda$. Next, we introduce a toy model for cosmological physics in the framework of AdS/CFT, wherein a 4D cosmology resides on an ETW brane propagating behind the horizon in a black hole microstate. We study the time-dependent physics of the behind-the-horizon region in such microstates, finding that it can often be probed by the time-dependence of entanglement entropy for sufficiently large CFT subsystems. We investigate the plausibility of obtaining localized 4D gravity on the ETW brane in both effective and microscopic versions of this model.
Last, we consider a doubly-holographic model of a radiating black hole, and apply the RT formula to analyze the time-dependence of the fine-grained entropy of its radiation. We obtain an analogue of the Page curve consistent with unitarity due to a phase transition between RT surfaces, after which the radiation system encodes part of the black hole interior.
Event Location:
https://ubc.zoom.us/j/68991164698?pwd=dzFGNVdPbSt4QldsVHNlWnJLL2ZWQT09 Passcode: 815209
Event Time:
Wednesday, May 17, 2023 | 12:00 pm - 3:00 pm
Event Location:
https://ubc.zoom.us/j/62625300003?pwd=RTBNckgzbDk0aXhRR3NyUUEyaGV4UT09
Add to Calendar
2023-05-17T12:00:00
2023-05-17T15:00:00
Refinement of the First r-process Abundance Peak Via High-Precision Mass Measurements
Event Information:
Abstract: Since the 1960's a general understanding of the creation of the chemical elements in the universe has existed. However, in recent decades this understanding has undergone refinement in describing the exact astrophysical mechanisms which result in the synthesis of isotopes, particularly those heavier (i.e. more protons) than iron.
After the first detection of a binary neutron star merger and it's subsequent kilonova in 2017, efforts into understanding the rapid neutron capture process (r-process) were redoubled in the form of both experimental and theoretical work. In particular, work has been performed investigating nuclei at the so-called waiting points of the r-process which result in the formation of the r-process abundance peaks. To this end, the underlying nuclear properties of the involved isotopes, specifically high-precision mass measurements of these nuclei are crucial in understanding the competition between neutron capture, photodissociation, and beta decay. At TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN), the Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS) provides experimental access to this property for short lived radioactive isotopes with low production rates in an environment with high backgrounds. A novel technique used at TITAN's MR-TOF-MS for reducing background contamination, mass-selective re-trapping, was established. Mass measurement results using the TITAN MR-TOF-MS and their subsequent effect on the formation of the first r-process peak is presented. Additionally, the technique of mass-selective re-trapping is investigated in detail, and recent upgrades to the technique are discussed.
Event Location:
https://ubc.zoom.us/j/62625300003?pwd=RTBNckgzbDk0aXhRR3NyUUEyaGV4UT09
Event Time:
Wednesday, May 10, 2023 | 1:00 pm - 4:00 pm
Event Location:
Centre for Brain Health room 3402A or https://ubc.zoom.us/j/63777759360?pwd=SmFXcG84UWFJc3c0Z2Q4d2NMVHNCQT09 Passcode: 921391
Add to Calendar
2023-05-10T13:00:00
2023-05-10T16:00:00
Development of advanced denoising and analysis algorithms for applications in hybrid PET/MRI brain imaging
Event Information:
Hybrid PET/MRI scanners are becoming more common in research and clinical settings, in particular for their ability to simultaneously acquire unique functional and structural information to probe the healthy and diseased brain. Data from both modalities need to be thoroughly processed to enhance signal-to-noise ratios (SNR), and the development and optimization of analysis algorithms is required to extract meaningful physiological quantities for medical research applications. This work provides significant contributions to these fields through the development, testing, and validation of four algorithms. PET data are intrinsically noisy due to the Poisson nature of positron emission events and the relatively low fraction of events detected by scanners, so we first improve upon an existing PET denoising algorithm to overcome limitations in quantitative accuracy in precision.
This proves important in task-based PET imaging, where tasks presented to a subject during scanning result in a small temporal signal change that is difficult to distinguish from noise. The developed PET denoising algorithm is thus coupled with an advanced PET detection algorithm which provides a significant improvement in the detection sensitivity of task-induced signal changes. Motivated by the success of existing PET denoising algorithms, we then develop an MRI denoising algorithm for low SNR functional MRI data, which demonstrates significant improvements in quantitative accuracy and precision of downstream modeling metrics.
Finally, we propose a pattern analysis extension of an existing joint PET/MRI analysis algorithm to identify disease-related alterations to simultaneously acquired multimodal data. We identify immediate applications of each algorithm in novel medical research studies, and proof-of-concept testing on human data is performed when available.
Event Location:
Centre for Brain Health room 3402A or https://ubc.zoom.us/j/63777759360?pwd=SmFXcG84UWFJc3c0Z2Q4d2NMVHNCQT09 Passcode: 921391
Event Time:
Thursday, April 27, 2023 | 4:00 pm - 5:00 pm
Event Location:
Henn 318
Add to Calendar
2023-04-27T16:00:00
2023-04-27T17:00:00
Effective field theory of black hole perturbations with timelike scalar profile
Event Information:
TALK RECORDING AVAILABLE AT: https://drive.google.com/file/d/1rCjcB4RkIckHq3anhXzzsKDS8QRsNW4n/view?usp=share_link
Abstract:
Many dark energy (DE) models are based on a scalar field with timelike gradient. In this talk we begin with a review of the systematic construction of the effective field theory (EFT) describing perturbations around the Minkowski background with a timelike scalar profile and its extension to cosmological backgrounds, i.e. the ghost condensation and the EFT of inflation/DE. If one hopes to learn something about the EFT of DE from black holes (BHs) then one needs to consider BH solutions with timelike scalar profiles. We thus extend the EFT to arbitrary backgrounds. Finally, as an application of the general EFT, we study odd-parity perturbations around a spherically
symmetric, static black hole background with a timelike scalar field responsible for DE and compute quasi-normal mode frequencies.
References:
https://arxiv.org/abs/2204.00228;
https://arxiv.org/abs/2208.02943;
Event Location:
Henn 318
Event Time:
Thursday, April 20, 2023 | 11:00 am - 12:00 pm
Event Location:
HEBB Building, Room 116
Add to Calendar
2023-04-20T11:00:00
2023-04-20T12:00:00
Searches for new physics with noble liquids at SNOLAB
Event Information:
Abstract:
The Standard Model of Particle Physics, which so successfully predicts interactions of elementary particles down to the smallest scales observed, is known to be an incomplete theory. In this talk, two types of searches for physics beyond the Standard Model will be discussed, both with noble liquids as the detection medium. First, I will present the latest results from experiments looking for dark matter interactions with liquid argon targets: the DEAP-3600 experiment located at SNOLAB, 2 km underground in Sudbury, Ontario, and plans toward the next-generation experiments DarkSide-20k and ARGO. Then, I will talk about the nEXO experiment, also planned to be located at SNOLAB, that will look for neutrinoless double beta decay in liquid xenon to determine whether neutrinos could be their own antiparticles. Finally, I will show developments in single-photon detection technology enabling nEXO and ARGO, with potential applications outside the field.
Bio:
See Simon's homepage here and faculty webpage here.
Event Location:
HEBB Building, Room 116
Event Time:
Thursday, April 13, 2023 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
Add to Calendar
2023-04-13T16:00:00
2023-04-13T17:00:00
That Spin 0 Boson Changed Everything
Event Information:
Abstract:
The Higgs Boson discovery in 2012 required us to think differently about planning for the future of Particle Physics, twice, now, since that summer 11 years ago. While the decades-long confirmation of the Standard Model itself is an historic episode – as a guide to the future, it’s not as helpful as one would like. Because it’s complete! I will describe Particle Physics planning in the US, review the features of the Standard Model that make it superb, point out why it’s frustrating, and describe hints that continue to motivate us for the coming decades.
Bio:
Raymond Brock is an experimental elementary particle physicist and University Distinguished Professor at Michigan State University (MSU). He received his B.S. in Electrical Engineering from Iowa State University in 1972. After a year in industry he returned to the university, receiving an M.S. in Physics and Philosophy of Science from Northern Illinois University and his Ph.D. in Physics from Carnegie-Mellon University in 1980. After two years as a postdoctoral researcher at the Fermi National Accelerator Laboratory he joined the MSU Department of Physics and Astronomy in 1982. In 2011 he was named University Distinguished Professor.
He is a Fellow of the American Physical Society and a recipient of the two Michigan State University all-university awards for research and teaching. He is an avid baseball fan and has coached baseball for many years at the high school level in Michigan.
Event Location:
HENN 201
Event Time:
Thursday, April 13, 2023 | 10:00 am - 11:00 am
Event Location:
AMPL 311
Add to Calendar
2023-04-13T10:00:00
2023-04-13T11:00:00
Ground State Solitons in Kitaev Spin Chains
Event Information:
Abstract: The bond-dependent Ising interaction present in the Kitaev model has recently attracted considerable attention. The attention has mostly focused on the two-dimensional honeycomb lattice version of the Kitaev model where several materials has been identified as potential realizations. However, one can also imagine realizing simpler one-dimensional Kitaev spin chains that still has a surprisingly rich structure. One example is the ferromagnetic material CoNb2O6 which shows signatures of bond dependent interactions. It is usually assumed that for the Kitaev spin chains the presence of a magnetic field does not lead to any interesting new physics. However, recently we have identified an unusual chiral soliton phase in antiferromagnetic Kitaev chains, appearing when the field is applied in specific directions. The phase is centered around a special point where a two-fold degenerate ground-state can be exactly found. In this talk I will present some of the interesting physics related to the soliton phase for both integer and half-integer spin and discuss a simple variational
picture of the soliton phase.
Speaker Bio: Erik Sorensen is originally from AArhus Denmark. He got his Ph. D. at the University of California, Santa Cruz in Physics in 1992. After UCSC, he spent two years (1992-94) as a postdoc at UBC in the physics department . From British Columbia he moved to Bloomington, Indiana for a second postdoc (1994-96) in the condensed matter theory group. From December 1996 till the fall of 2001, Professor Sorensen worked as a professeur at the Université Paul Sabatier in Toulouse and in the fall of 2001, he joined the department of physics and astronomy at McMaster University. In general, he work in the area of strongly correlated systems, often on low-dimensional models of frustrated magnets and electronic and superconducting systems, often using state of the art computational methods.
Event Location:
AMPL 311
Event Time:
Wednesday, April 12, 2023 | 1:00 pm - 3:00 pm
Event Location:
https://ubc.zoom.us/j/62482228932?pwd=a3RIU0xFY0wrSFYrYzNFbzc2ZXZ0dz09 Passcode: 199086
Add to Calendar
2023-04-12T13:00:00
2023-04-12T15:00:00
MARKERLESS DYNAMIC TUMOR TRACKING USING DIAPHRAGM AS A SOFT-TISSUE ANATOMICAL SURROGATE FOR LIVER TUMORS
Event Information:
Liver cancer is the sixth most common cancer worldwide and radiation therapy has been a non-surgical alternative for treating patients with advanced liver cancer. Dynamic tumor tracking (DTT) has been developed to treat intra-fractionally moving liver tumors with radiation therapy. However, one of the most challenging aspects of DTT is detecting the internal tumor position, which usually relies on implanted markers as a surrogate for tumor position. This thesis addresses two questions: 1) The uncertainty in marker-based DTT by using in-vivo EPID images, and 2) The feasibility of eliminating implanted markers by using soft tissue surrogates for the liver target.
The first part of the thesis investigates the uncertainty in marker based DTT for Stereotactic Ablative Body Radiotherapy (SABR) treatments of the liver. The study utilized in-vivo EPID images to assess the target localization uncertainty for DTT. Phantom and patient EPID images were acquired during non-coplanar 3DCRT-DTT delivered on a Vero4DRT linac, and the absolute differences between the measured center of mass
(COM) of the markers relative to the aperture-center were reported in pan, tilt, and 2D-vector directions at the isocenter plane. The study found that marker based DTT uncertainty could be evaluated in-vivo on a field-by-field basis using EPID images, which can contribute to PTV margin calculations for DTT.
The second part of the thesis focuses on investigating the feasibility of using soft tissue surrogates for liver tumors during markerless dynamic tumor tracking (MDTT) radiotherapy. The study aimed to demonstrate the pre-clinical feasibility of MDTT using the diaphragm as an anatomical motion surrogate for liver radiotherapy. KV X-ray images from phantom and ten patients undergoing liver radiotherapy were used to analyze the relative motions of the diaphragm and gold markers. The study found that the diaphragm positions correlated well with markers'
positions and could be used as a reliable surrogate for motion management. The study also utilized the Brainlab Vero4DRT linac MDTT module, originally designed for lung tracking, and applied it in a novel way to demonstrate the effectiveness of using the diaphragm as a surrogate for liver tumor motion management during MDTT radiotherapy.
Event Location:
https://ubc.zoom.us/j/62482228932?pwd=a3RIU0xFY0wrSFYrYzNFbzc2ZXZ0dz09 Passcode: 199086
Event Time:
Thursday, April 6, 2023 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
Add to Calendar
2023-04-06T16:00:00
2023-04-06T17:00:00
Hunting for quantum butterflies
Event Information:
Abstract:
Unpredictability manifests itself in very different ways at the classical and the quantum level. This has led to long-standing open questions, including the connection between chaos theory and quantum mechanics. Recent advances in quantum computing have made it possible to study foundational questions about the quantum-classical boundary in an experimental setting. This talk will discuss our explorations of chaos and quantum-classical correspondence in the context of quantum information science, and the surprising connections between the quantum and classical world.
Bio:
Shohini Ghose wanted to be an explorer like Rakesh Sharma, the first Indian to go to space. She hasn’t made it to space yet, but she did become an explorer of the quantum world as a Professor of physics and computer science and NSERC Chair for Women in Science and Engineering at Wilfrid Laurier University. Her research is in the field of quantum information science, and she and her colleagues were the first to observe signatures of chaos in quantum entanglement. Shohini aims to create an inclusive scientific community in Canada as the Director of the Laurier Centre for Women in Science (WinS). She is a TED Senior Fellow and in 2017 she was selected to the College of the Royal Society of Canada. Her TED talks and other online videos have received over 5 million views, and her recent article on quantum computing was featured in the Harvard Business Review's Year in Tech 2022. In 2021, she was appointed to the Scientific Board of the UNESCO International Basic Science Program. She still dreams of going to space.
Learn More:
View Shohini's faculty webpage here
See Shohini's Ted Talk, "A beginner's guide to quantum computing" here
See Shohini's public lecture (video) on "The quantum revolution", hosted by the Perimeter Institute here
Read an interview with Shohini on "The future of quantum computing" (Bosch) here
Event Location:
HENN 201
Event Time:
Thursday, April 6, 2023 | 10:00 am - 11:00 am
Event Location:
AMPL 311 or watch online
Add to Calendar
2023-04-06T10:00:00
2023-04-06T11:00:00
The Chemistry of Quantum Materials
Event Information:
Abstract: Quantum materials are hoped to change technology in various aspects. However, most of the desired applications are hindered by the lack of suitable materials. In my group we are using concepts from chemistry to understand, predict and synthesize new quantum materials. In this talk, I will show how simple concepts, such as measuring bond distances, allow us to make predictions about electronic structures of materials, which we can then use to find new quantum materials. I will also show how we can use chemical exfoliation, a synthesis method that is much more used in energy science to create 2D nanosheets, to synthesize novel 2D quantum materials. Examples are 2D magnets and superconductors, for which our synthesis method allows for large-scale productions of inks to print electronics.
Speaker Bio: Dr. Leslie M. Schoop received her Diploma in Chemistry from Johannes Gutenberg University (2010) and PhD in Chemistry from Princeton University (2015). She then went on to work as a Minerva fast-track fellow under Professor Bettina Lotsch at the Max Planck Institute for Solid State Research (2015-2017). Dr. Schoop joined the Princeton University Department of Chemistry Faculty in 2017 and was tenured in 2022. In 2019 she won the Beckman Young Investigator award and became a Moore foundation EPiQS Materials Synthesis Investigator. In 2020 she was awareded the Packard fellowship for science and engineering and in 2021 the Sloan fellowship in Chemistry and the DOD Office of Naval Research Young Investigator award. In 2022 you was awarded the NSF CAREER award. The Schoop Lab is working at the interface of chemistry and physics, using chemical principles to find new materials with exotic physical properties.
Event Location:
AMPL 311 or watch online