Traditionally, the wetting of a solid surface by the drop of an emulsion has been thought to be mediated by the formation of a liquid bridge that connects the drop and the surface. In the current work, we experimentally show the spreading of a drop on a surface follows a different, new mechanism. Experiments were conducted for liquid-liquid systems, wherein drops of higher density (glycerol)...
In a crowded space, a long chain molecule can be phase-separated into a condensed state, redistributing the surrounding crowders. Here we discuss how crowding influences the spatial organization of a ring polymer, consisting of two “arms," in a cylindrical space. In a parameter space of biological relevance, the distributions of monomers and crowders follow a simple relationship: the sum of...
The internal structure of porous materials and membranes plays a critical role in their mechanical and biochemical properties, especially if they are targeted for cell growth in tissue healing and regeneration applications. Collagenous membranes are a class of proteinaceous materials that has been targeted for cell scaffolding studies because collagen is a structural protein found in many...
MacSANS is a new small angle neutron scattering (SANS) beamline currently under construction at the McMaster Nuclear Reactor, a 5 MW research reactor based at McMaster University in Hamilton, Ontario. This beamline is designed to study a broad range of nanostructured materials, including biological membranes, polymers, superconductors, and novel magnets. In particular, MacSANS will allow...
We study the structure of novel polymers for proton and anion exchange membranes through a combination of experiment and simulations. X-ray and neutron scattering experiments reveal microphase separation and intermolecular order, and interpretation is validated by molecular dynamics (MD) simulations. These studies help us understand the conductivity and swelling of the materials, and inform...
Living cells are composed of a complex mixture of macromolecules. To regulate their activity, cells partition these molecules into specialized compartments called organelles. Typically, membranes form a selective barrier between organelles and the cytoplasm, allowing each compartment to maintain a distinct biochemical composition that is tailored to its function. However, cells also contain a...
Ideally, we would like to have first-principles simulations capable of quantitatively accurate predictions for any block copolymer system. Usually, our choice of model involves balancing the complexity needed to faithfully represent an actual experimental system and the simplicity required to make the simulation tractable. Fortunately, block copolymer phase behavior is believed to become...
Biomaterial fabrics have numerous biomedical applications ranging from drug delivery to tissue engineering. A variety of approaches are available for generating biomaterial fibers from various precursor polymer solutions. Approaches such as wet-spinning, electrospinning, and extrusion have been exploited in the past to generate extremely long fibers ranging in diameter from tens of nanometers...
Collagen is the protein building block of most mammalian tissues such as tendon, arteries, skin and bone. In its triple helical form, collagen assembles into fibrils with tensile properties comparable to the strongest man-made polymer materials. Structural characterization of collagen fibrils using X-ray scattering and electron microscopy led to a picture where long triple helices form a...
The extracellular matrix (ECM), a complex network of proteins including collagen (COL) and fibronectin (FN) couples a cell with its environment and directly regulates the cell’s fate via physical and biochemical signals. Although the ECM was often considered a static structure providing cohesion and mechanical integrity to tissues, it has recently been shown that (i) the nano-structure, (ii)...
Amphiphilic secondary structures are ubiquitous in native proteins, where they serve a wide variety of functions from specific binding ligands to structural elements in supramolecular assemblies. This talk describes the use of amphiphilic coiled-coil motifs in modular protein polymers as a strategy to achieve electrochemical gelation capabilities. Our de novo electrogelation protein is a...
Hydrophobins are low molecular weight (5-20 kDa) self-assembling proteins secreted by fungi that accumulate at hydrophobic-hydrophilic interfaces and are extremely surface-active. Hydrophobins can also undergo a structural rearrangement and oligomerize to form rodlets, which are an insoluble functional amyloid that coats fungal spores to act as a water repellent, facilitate dispersal into the...
Monte Carlo simulations are used to study the conformational properties of a folded semiflexible polymer confined to a long channel. We measure the variation in the conformational free energy with respect to the end-to-end distance of the polymer, and from these functions we extract the free energy of the hairpin fold as well as the entropic force arising from interactions between the portions...
Natural and engineered proteins have recently been discovered with a unique ability to reversibly switch between entirely different 3-dimensional structures, with accompanying major changes in their secondary structure contents, hydrophobic sidechain packing and overall shape. The major conformational changes in these shape-shifting proteins are triggered by, for example, ligand binding,...
Water is the most important solvent in biological systems. Yet majority of its properties are poorly reproduced by the most commonly used models. An ideal water model needs to accurately capture both structure and dynamics over a wide range of thermodynamic conditions.
To create such a model we attempted both coarse grained1 and atomistic parametrizations. Our experience shows the...
Introduction: The three-dimensional (3D) culture of neural cells in extracellular matrix (ECM) gels holds promise for modeling neurodegenerative diseases. However, air-liquid interfacial tension and evaporation can result in inconsistent 3D cultures at low volumes. Thick-layer hydrogels can counter these factors, but large diffusion distances, high cost, and incompatibility with standard...
The production of functional skin equivalents derived from human cells holds promise for reconstruction of severe wounds and for modeling various skin pathologies. Although epidermal cells have the capacity to self-organize and form stratified structures in culture, it is often difficult to integrate these structures with dermal components. In recent years, cellular bioprinting has emerged as...
The collagen fibrils are the main building block of connective tissues in mammals where they fulfill both structural and mechanical roles. The structure of a fibril is based on collagen molecules that self-assemble into micro-fibrils and sub-fibrils stabilized by hydrogen bonds and covalent crosslinks. The non-integer staggering of collagen molecules results in a characteristic D-band pattern...
Many biologically motivated problems naturally call for the investigation and comparison of molecular variants, such as determining the mechanisms of specificity in biomolecular interactions or the mechanisms of molecular evolution. We consider a generalized ensemble algorithm for coarse-grained simulations of biomolecules which allows the thermodynamic behavior of two or more sequences to be...
We explore a variety of thermodynamically stable molecular configurations of collagen fibrils. Using a liquid crystal model of radial fibril structure with a double-twist director field, we show that two dimensionless parameters, the ratio of saddle-splay to twist elastic constants $ k_{24}/K_{22}$ and the ratio of surface tension to chiral strength $\tilde{\gamma} \equiv \gamma/(K_{22}q)$,...
Sixty years ago, Canadian Physicist Bertram Brockhouse pioneered inelastic neutron scattering. His invention, the triple axis spectrometer, enabled direct measurements of phonons, magnons, and other collective elementary excitations in materials. In more recent times the practice of inelastic neutron scattering has been revolutionized by pulsed neutron time-of-flight spectroscopy, enabled in...
Creative, collaborative effort to advance a respectful and caring community can make a big difference to students, staff and faculty in physics departments, improving their ability to thrive. Data on demography and the climate for inclusion at MIT show the effects of inclusive leadership based on community, culture and values. This short talk will provide both data and tips on how you can...
Gaining insight into the astrophysical processes that govern nucleosynthesis in stellar scenarios requires a detailed understanding of the involved nuclear reactions. Radiative capture cross sections at typical temperatures of environments like novae, X-ray burst or supernovae are in many cases vanishingly small, thus making the reaction rates extremely challenging to access...
Sic1 is a disordered kinase inhibitor, which must be phosphorylated on at least six sites to allow its recognition by the WD40 binding domain of the Cdc4 protein in the yeast cell cycle. The highly-cooperative, switch-like dependence on the number of phosphorylated sites on Sic1 cannot be accounted for by traditional thermodynamic models of cooperativity. We used single-molecule fluorescence...
Standard Model processes are at the core of the physics programme of the ATLAS Experiment. In this talk, a review of recent measurements is presented: the production cross-sections of vector bosons in association with jets; the mass of the $W$ boson; processes yielding jets of hadrons in the final state; strong and electroweak production modes of the top quark and its properties; the...
Ionospheric physics is rich with anomalies that are typically taking place on short temporal and/or spatial scales. Finding suitable explanations for these anomalies is one thing that keeps the field alive, as they lead to new discoveries into the rich ways by which the ionosphe couples with the atmosphere and magnetosphere, particularly when there are large departures of the system from...
We identify the light-cone-like structures present following quenches in spin-chains as quantum caustics. These are discrete versions of the singularities classified by catastrophe theory. From this identification follows: local universality
We create and control intense transient waveforms by compressing in space and time optical pulses down to a single half-cycle, nearly 1 femtosecond (1 fs = $10^{-15}$ s) in duration. By measuring the optical waveform using an in-situ attosecond (1 as = $10^{-18}$ s) technique we confirm the pulse reshaping. We use the intense transient as a source for generating isolated attosecond pulses...
Imagine a quantum system placed within a thermal gas, which is itself composed of many quantum systems e.g. atoms/molecules. As the constituents of the environment scatter off of the system, it is natural to expect that the system will reach a thermal equilibrium with its environment. Moreover one may expect that the ultimate thermalization of the system is largely independent of the coupling...
Attosecond Physics explores ways to follow and control matter with unprecedented temporal resolution (1 attosecond= 10-18 s.). Strong laser fields used to apply forces on the sub-cycle timescale, together with the availability of tabletop attosecond soft x-ray pulses, now open avenues for time-resolving ultrafast dynamics on the unexplored attosecond timescale [1, 2]. In this first attosecond...
We present first results from a comprehensive three-dimensional model of magnetosphereionosphere coupling. The model describes plasma flow produced by global scale (Volland-Stern) convection electric fields that are coupled with a physical model of the ionosphere. The initial
magnetospheric plasma density is specified using the Global Core Plasma Model (GCPM), while initial density and...
The goal of this project is to make progress in quantum gravity by studying gravity in quantum mechanical systems at atomic scales. We compare approaches to the generation of gravitational waves and gravitons from quantum mechanical systems such as the ammonia molecule. The approach is guided by the strong analogy between classical electromagnetism and classical general relativity. We evaluate...
In asymptotic giant branch (AGB) stars, 22Ne plays an important role in several nucleosynthesis processes, with its production competing with the synthesis of 19F through the so called ‘poisoning reaction’, and the following transfer into 25Mg acting as one of the main neutron sources for the s-process, affecting the reaction rates of numerous isotopes.
In this contribution, we present a...
The PIENU experiment at TRIUMF aims to make a high-precision measurement of the $ \pi \rightarrow e \nu $ branching ratio: $ R_{\pi} = \frac{\Gamma\left(\pi \rightarrow e \nu \hspace{1 mm} + \hspace{1 mm} \pi \rightarrow e \nu \gamma \right)}{\Gamma\left(\pi \rightarrow \mu \nu \hspace{1 mm} + \hspace{1 mm} \pi \rightarrow \mu \nu \gamma \right)}. $ Measurement of $R_{\pi}$ provides a...
Many hypotheses have been posed about the reasons why there are fewer women than men identified as physicists, although most have not been rigorously tested (and some could not be in an ethical way.) Over time these hypotheses have shifted in nature. I will use the Halpern, Wai and Saw (2005) psycho-bio-social framework for analyzing gender differences to review recent findings that shed light...
The retina, with its neural tissue, also acts as a window on the brain. Alzheimer’s disease is currently only definitively diagnosed after death from an analysis of deposits of amyloid beta (plaques) in the brain. Retinal function has been reported to be directly affected by the disease and neurotoxic effects of amyloid beta have been demonstrated in the retina. We were one of the first groups...
Alzheimer’s disease (AD) is a neurodegenerative disease characterized by dementia and memory loss for which no cure or prevention is available. Amyloid toxicity is a result of the non-specific interaction of toxic amyloid oligomers with the plasma membrane.
We studied amyloid aggregation and interaction of amyloid beta (1-42) peptide with lipid membrane using atomic force microscopy (AFM),...
A striking example of quantum behaviour in the nucleus are the nuclear shells, analogous to the electron shell system in atomic physics, at well-known magic numbers of protons/neutrons. Nuclear shells can evolve with changing proton and neutron count as shown in the emergence of the N = 32 shell closure. This changing nuclear structure can directly affect nuclear properties like masses...
When a charged particle moves in a plane perpendicular to a constant magnetic field (z-direction) the discrete energy levels are called Landau levels. The energies resemble those of the harmonic oscillator with $\omega$ the cyclotron frequency $\omega_c$. The energies are highly degenerate, with the degeneracy being independent of the energy. We now add a linear electric field parallel to the...
NEWS-G (New Experiments With Spheres-Gas) is a direct dark matter detection experiment using Spherical Proportional Counters (SPCs). SPCs are gaseous detectors, where different gases can be use to optimise sensitivity for different dark matter masses. First results using Neon in the prototype SEDINE at Laboratoire Sousterrain de Modane (LSM) were presented at the 2017 CAP Congress.
I will...
Counting photobleach steps lets us infer the number of oligomeric subunits of fluorescently-labelled protein complexes. While ad hoc step-counting algorithms are adequate for low noise imaging with small numbers of steps, noise increases with the number of fluorophores and introduces bias when the intensity trace is filtered to reduce noise. We present a principled Bayesian approach with a...
Half-lives of $N=82$ nuclei below doubly-magic $^{132}$Sn are key input parameters for calculations of any astrophysical $r$-process scenario and play an important role in the formation and shape of the second $r$-process abundance peak. In the past, shell-model calculations of neutron-rich nuclei near the $N=82$ neutron shell closure that are not yet experimentally accessible have been...
CubeSats are increasingly popular among the space physics commuinty, as an afordable means of deploying large numbers of instruments in space, thus providing better monitoring and coverage of space environment. Needle probes consisting of thin cylindrical probes of length ranging from a few to several centimeters, have been used on a number of cubeSats, because of the relative simplicity with...
New Experiments With Spheres-Gas (NEWS-G) is a dark matter direct-detection experiment using spherical proportional counters (SPCs) with light noble gases. First results obtained with a SPC prototype operated with Ne gas at the Laboratoire Souterrain de Modane (LSM) have already placed NEWS-G as a leader in the search for low-mass WIMPs. The forthcoming next phase of the experiment consists of...
The initialization and control of the quantum states of excitons in semiconductor quantum dots (QDs) may be achieved using coherent optical pulses, making these systems of interest for solid state approaches to quantum simulators [1] and single photon sources [2]. Quantum state control via adiabatic rapid passage (ARP), which is insensitive to variations in the QD parameters (dipole moment,...
This presentation will discuss Hydro-Quebec’s historical records and observations of geomagnetic disturbance. We will show how data/forecasts are used and integrated in control room operation. A real event will be presented in detail. Looking at the future, we will illustrate some gaps and research needs. The main idea of the presentation is that electricity provides relevant feedbacks to...
Phase-locked, few cycle pulses of THz light are powerful tools for both probing and controlling charge carriers in condensed matter. Used as time-resolved spectroscopic probes, meV scale excitations can be monitored with sub-picosecond temporal resolution. In this talk, I discuss recent multi-THz measurements on organometallic metal halide perovskites revealing exciton energetics, screening...
TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) is located at the Isotope Separator and Accelerator (ISAC) facility, Vancouver. Titan is a multiple ion trap system capable of performing high-precision mass measurements and in-trap decay spectroscopy. In particular TITAN has specialised in fast Penning trap mass spectrometry of short-lived exotic nuclei using its Measurement Penning...
Computed Tomography (CT) is considered a mature technology as it did not change significantly since the advent of multislice devices (2000s) and helical acquisitions (1990s). However, innovations in CT are still happening. After a brief history of CT, the evolution of this imaging modality during the last few years will be reviewed from technological, social and medical perspectives. On the...
SuperCDMS SNOLAB is a dark matter experiment currently under
construction and slated for installation in SNOLAB in 2019. SuperCDMS
SNOLAB will use cryogenic silicon and germanium detectors to search
for nuclear recoils produced by dark matter particles interacting in
the detectors. These nuclear recoils will produce both phonon
excitations and ionization (electron/hole pairs) in the...
In 2024 the Large Hadron Collider at CERN will enter its High Luminosity phase, which will see its instantaneous luminosity reach seven times its design value and will produce pp collisions at 14 TeV with an average of 200 interactions per bunch crossing.
These challenging conditions are beyond the ATLAS design and require an upgrade of the ATLAS tracking system. The ATLAS new Inner Tracker...
Bursts of enhanced electron density in the ionospheric D-region due to photoionization by X-ray radiation from solar X-ray flares leads to a fadeout of short wave signals, potentially causing a loss of high frequency radio communication in affected regions. D-region absorption is typically monitored using riometer instruments which typically operate at 30 MHz. There are well established...
Shape coexistence is associated with nuclear deformations at low excitation energies and has been a topic of extensive research in nuclear physics over the past 60 years. Shape coexistence is driven by two opposing forces. One is the stabilizing effect of closed shells causing the nucleus to have a spherical shape, while the other is the residual interaction between proton and neutrons, the...
The ability to directly probe ultrafast phenomena on the nanoscale is essential to our understanding of excitation dynamics on surfaces and in nanomaterials. Recently, a new ultrafast scanning tunneling microscope (STM) technique that couples terahertz (THz) pulses to the scanning probe tip of an STM was demonstrated (THz-STM), showing photoexcitation dynamics of a single InAs nanodot with...
The neutron-rich Cadmium isotopes around the well-known magic numbers at $Z=50$ and $N=82$ are prime candidates to study the evolving shell structure observed in exotic nuclei. Additionally, the extra binding energy observed around the nearby doubly-magic $^{132}$Sn has direct correlations in astrophysical models, leading to the second r-process abundance peak at $A\approx130$ and the...
In this study, we begin by presenting an overview of the methodology behind existing empirical ionospheric electron density models, including the E-CHAIM and International Reference Ionosphere (IRI). Several limitations have been identified in the methodology used to parameterize the IRI (Themens et al., 2014, 2016, and 2017a), particularly in its application at high latitudes. Using these...
As part of the 2018 Congress for the Canadian Association of Physicists (CAP), the Division of Physics in Medicine and Biology (DPMB) is hosting a "DPMB 101" session. The purpose is to present "primer" talks that provide an overview of salient topics broadly relevant to the meeting. The intended audience is expected to be diverse, ranging from the relative novice (e.g., a curious undergraduate...
The High-Energy Light-Ion eXperiment (HELIX) is designed to measure the
fluxes of light cosmic-ray nuclei at energies of a few GeV per nucleon.
The primary goal is to study the evolution of the ratio of Be-10
to Be-9 between 0.2 GeV/n and 3 GeV/n. The former is a radioactive 'clock
isotope' while the latter is stable, so the ratio contains information about
how far and through what the cosmic...
Research into organo-halide perovskites has flourished due to their unprecedented success as an absorbing layer in solution processed solar cells. Theoretical studies have shown these materials exhibit intriguing optical properties such as large spin-orbit coupling, photo-induced magnetization, and spin-dependent optical Stark effect, leading to potential spintronic applications. However; very...
High precision measurements of the $\mathcal{F}t$ values for superallowed Fermi beta transitions between $J^\pi = 0^+$ and isospin $T=1$ isobaric analogue states allow for stringent tests of the electroweak interaction described by the Standard Model. These transitions provide an experimental probe of the Conserved-Vector-Current hypothesis, the most precise determination of the up-down...
The nature of the dark matter thought to make up most of the matter in the universe is unknown. It may consist of new particles from beyond the standard model. For close to two decades, the DAMA experiment has claimed to have detected such particles. This claim is controversial, in particular because there is no accepted model for the background radioactivity in DAMA. One major unknown is the...
Charge radius is an important bulk property of the nucleus for investigating nuclear structure. The nuclei lying close to the boundaries of the nuclear chart (the drip lines) have revealed new features like halo and skin. Another new phenomenon that has emerged in the neutron-rich region is the changing or vanishing of magic numbers [1,2]. The knowledge of proton radii is crucial for...
Solar cells based on CH3NH3PbI3 (MAPI) have reached efficiencies comparable to the best polycrystalline silicon solar cells in just 9 short years [1]. Despite the unparalleled increase in efficiency, the fundamental photo physical properties in this archetypical perovskite material system are not yet well understood. In order to further optimize device performance, it is essential to...
It is well-known that the atmosphere in the polar regions of this planet is considerably different from the more temperate regions due to a variety of factors including the planetary rotation, the magnetic field and the fact that the extreme polar regions undergo an annual cycle of light and darkness which overwhelms the 24-hour cycle that characterises the lower latitudes.
For the last...
We report direct spectroscopic evidence of correlations between monopoles in a quantum spin ice. A hierarchy of unequally spaced magnetic excitations has been observed via low energy inelastic neutron spectroscopy in Pr2Sn2O7, resembling the confinement of spin defects in low-dimensional quantum magnets.[1],[2] Using a simple linear potential model to fit the excitations, we have estimated...
The QWeak collaboration completed a two year long, high precision measurement of the parity violating asymmetry in the elastic scattering of 1.1 GeV, longitudinally polarized electrons from protons. At low momentum transfer the measured asymmetry is directly related to the Weak charge of the proton $Q^p_W = 1 - 4 sin^2 \theta_W$. The Standard Model makes a firm prediction for the size of the...
We find the explicit form of two-point functions for the conformal energy momentum operators as well as conformal spin-one operators on the near horizon of a near extremal Kerr black hole. We introduce the appropriate boundary actions for the spin-two and the vector fields near the horizon of near extremal Kerr black hole. We find the two-point function for the conformal energy-momentum...
Many biological processes in cells are complex yet sparsely characterized. Constructing physical models of such systems then often requires making many assumptions based on guesswork. Instead of ignoring or guessing unknown details in complex processes we have derived universal balance relations to rigorously characterize stochastic fluctuations in incompletely specified systems. Specifying...
One of the more intriguing solutions of General Relativity is the C-metric, which can be interpreted as describing the spacetime of an accelerating black hole. Little is known about the thermodynamics of these objects. Here I present a consistent formulation of the thermodynamics of accelerated black holes, resolving inconsistencies and discrepancies that have appeared in previous...
Observations of aerosol scattering and absorption offer valuable information about aerosol composition. We apply a simulation of the Ultraviolet Aerosol Index (UVAI), a method of detecting aerosol absorption from satellite observations, to interpret UVAI values observed by the Ozone Monitoring Instrument (OMI) over 2005–2015 to understand global trends in aerosol composition. We conduct our...
The proton radius puzzle is the difference between the radius of the proton as measured with electron scattering and atomic hydrogen spectroscopy, and that measured in muonic hydrogen. In 2010, the CREMA Collaboration published their measurement of the proton radius $R_p=0.8409(4)$ fm, which was made by studying the Lamb shift in muonic hydrogen. Although ten times more precise than the...
Chiral interactions in magnetic materials are unique in their ability to stabilize static magnetic solitons, known as skyrmions. At surfaces and interfaces, the chiral interaction results in novel magnetic surface states [1]. These surface twists help to further stabilize skyrmions in thin films [2], together with the influence of epitaxy induced magnetocrystalline anisotropy. These...
The development of drug resistance is a serious problem that reduces therapeutic susceptibility and complicates the treatment of infectious disease and cancer. To explore non-genetic causes of spontaneous drug resistance in rapidly proliferating cell populations, we constructed a set of synthetic transcriptional regulatory networks in yeast Saccharomyces cerevisiae to control the expression of...
This talk will present the current status of the PICO dark matter experimental program. The PICO detectors are based on the bubble chamber technology and record potential interactions of WIMPs in the target fluid through phase transitions induced by the energy depositions of recoiling nuclei. The technique is complementary to other dark matter search methods and has lead to several...
Accurate characterization of the ionosphere in response to thunderstorms has important implications for the effective use of high frequency (HF) communications in civilian and military operations, to include emergency services, amateur radio, aviation, and over-the-horizon radar. This study investigates changes in the structure of the ionosphere due to strong convective activity and cloud...
More than half of the energy produced worldwide is currently lost as heat and recovering even a fraction of that would be beneficial for global climate change. Toward this aim, thermoelectric materials can recover waste heat and convert it to useful energy. However, thermoelectrics are not widely commercially applied due to high cost and low efficiency. The search for new high-performance...
The Super Cryogenic Dark Matter Search experiment (SuperCDMS) seeks direct evidence of Weakly Interacting Massive Particle (WIMP) dark matter through interactions with cryogenic germanium crystals. Particle interactions in the germanium produce phonons and electron-hole pairs. The CDMS low ionization threshold experiment (CDMSlite) is an operating mode of SuperCDMS that applies a high...
Fog reduces visibility, causing delays in transportation by land, sea and air. It is also a safety hazard that results in accidents and sometimes even death. Like cloud droplets, fog droplets form on cloud condensation nuclei, existing aerosol particles in the atmosphere that have the ability to activate into droplets. As such, fog droplets provide a unique, in situ method of studying the...
We present a no-hair theorem for spherical black holes in scalar-tensor gravity. Contrary to the existing theorems, which are all proved in the Einstein conformal frame, this proof is performed entirely in the Jordan frame. The theorem is limited to spherical symmetry (instead of axisymmetry), but it holds for non-constant Brans-Dicke coupling.
[Based on V. Faraoni, Phys. Rev. D 95, 124013 (2017)]
The precise measurement of the 1S-2S transition in atomic hydrogen via 2-photon spectroscopy determines the value of the Rydberg and constrains our knowledge of the fundamental constants. The prospect of such a measurement in antihydrogen to test CPT motivated the construction two decades ago of the CERN AD and its initial program . The ALPHA collaboration has now measured this transition in...
Human aging leads to the stochastic accumulation of damage. We model an aging population using a stochastic network model. Individuals are modeled as a network of interacting nodes, representing health attributes. Nodes in the network stochastically damage and repair, with rates dependent on the state of their neighbors. Damaged nodes represent health deficits. Overall damage in the network is...
High entropy materials are a group of materials that can be potentially used in extreme temperature applications and have interesting properties such as hardness, toughness, and corrosion resistance. In particular, high entropy oxides have attracted attention due to intriguing properties such as colossal permittivity and superionic conductivity. Since high entropy oxides are achieved from...
Dendrites are often excitable structures involved in the signal processing of almost all neurons.
We find that when an active dendrite has a greater intrinsic variability and a longer refractory period
than the soma, it will determine spike times for weak inputs but be entrained by somatic spikes for
strong inputs. This produces an input-dependent gating of dendritic noise. As a result,...
Brans-Dicke gravity, enriched by the possibility of an arbitrary potential V (ϕ) for the Brans-Dicke scalar field, and in the presence of conformally invariant matter admits a 1-parameter symmetry group. We explore the use of these symmetries as a solution-generating technique using known solutions as seeds. We apply this technique to generate, as examples, new spatially homogeneous and...
The Super Cryogenic Dark Matter Search (SuperCDMS) uses cryogenic semiconductor detectors to search for Weakly Interacting Massive Particles (WIMPs), a well-motivated class of candidate particles for the dark matter that constitutes 27% of the energy density of the universe. The CDMS Low Ionization Threshold Experiment (CDMSlite) probes the low mass WIMP region (<10 GeV/c2) by...
Motivated by the recent experimental realizations of pyrochlore thin films, I will explore in this talk some of the promising facets offered by the slab geometry. Thin films are a natural platform to study the confinement of spin-liquid gauge fields and the evolution from three to two dimensional spin textures. In spin ice films for example, monopole excitations may crystallize on the...
The weight of antimatter is a crucial missing measurement in our picture of the natural world. It is important in two ways: 1. The predominance of matter created in the Big Bang demands some form of mismatch in properties between matter and antimatter. Many experiments have sensitively compared their charge, magnetic moment, nuclear bonding and decay behaviour, yet no significant mismatch has...
In the context of black hole chemistry, we study the thermodynamics of asymptotically de Sitter black holes with conformal scalar hair in Einstein gravity. The hair parameter allows us to reach thermodynamic equilibrium between the event horizon and the cosmological horizon. We find that the system of the black hole and the de Sitter space surrounding it undergo a phase transition that...
The existence of a non-zero neutron electric dipole moment (nEDM) would violate parity and time-reversal symmetry. Extensions to the Standard Model predict the nEDM to be $10^{-26}$ -- $10^{-28}$ e-cm. The current best upper limit set by Sussex/RAL/ILL nEDM experiment is $3.0 \times 10^{-26}$ e-cm. The nEDM experiment at TRIUMF is aiming at the $10^{-27}$ e-cm sensitivity level. We are...
The proposed ionising influence of cosmic rays on atmospheric aerosols, clouds and atmospheric electrical properties has resulted in several attempts to obtain convincing correlations. Several theoretical studies on such possible indirect influence is still poorly understood while the observational evidence remains controversial and incomplete. This study examines the...
The recent announcements of the first ever detections of gravitational waves from colliding black holes and neutron stars have launched a new era of gravitational wave astrophysics. Gravitational waves were predicted by Einstein a hundred years earlier. I will describe the science, technology, and human story behind these discoveries that provide a completely new window into some of the most...
$B\to K^*\nu\bar \nu$ is an excellent venue to test various model predictions for $B\to K^*$ transition form factors. Here we compare predictions for the differential branching ratio, as well as the longitudinal polarization fraction obtained from AdS/QCD holographic light-front wavefunction and QCD sum rules.
Studies on scattering of longitudinally and transversely incident beam of electrons by hollow cylindrical potential and coaxial cylindrical potentials have shown the presence of quasi bound “whispering” modes [1,2]. The realization of Levinson’s theorem [3,4] has been studied for some scattering potentials and results are widely available.
Roberts and Valluri [5] presented a geometric...
We have recently determined a correlation between the acoustic response, state of charge and state of health of closed system electrochemical energy storage systems. Because a closed cell is a mass redistribution reactor, and in a standard cell the volume is effectively fixed, the distribution of density within a battery must change as a function of state of charge and, along with density, the...
Advances in medical imaging and demands for better diagnoses brought up the idea to combine complementary image modalities with the aim to provide better image quality and more information. Many combined PET/MRI scanners designed for truly simultaneous operation are still in the developing stage. One of the main interferences between PET and MRI arises from the different material magnetic...
Owing to their relative simplicity, Langmuir probes are the instrument of choice to infer the density and temperature in space and laboratory plasma experiments. The interpretation of probe characteristics, that is, the collected current as a function of bias voltage, is practically always based on theoretical models amenable to analytic solutions, and capable of producing fast solutions under...
If you are planning to apply for a faculty position, or for a promotion, or if you are up for tenure, you will likely have to submit your teaching dossier (also known as teaching portfolio) in addition to your CV and research statement. This one-hour workshop will get you started on preparing your dossier. You will learn what information it should include, how to collect and organize evidence...
On 12 September 2014 the IMF turned very strongly northward for a prolonged period of time, reaching up to 28 nT at some point. Clauer et al (JGR, Space Physics, 121, 5422, 2016) showed from RISR-N Incoherent Scatter Radar (ISR) data at Resolute Bay that the convection on the sunward side of the polar cap was very strong and sunward during this exceptional event, with a convection electric...
I highlight how the problem of obtaining correspondence rules for SU3 Wigner function differs from that of the SU2 problem. I show how these rules are easily obtained for the Q-functions but how the transition from Q to Wigner functions for SU3 brings about novel features not present in SU2. A path to solution will be proposed.
Plasma flow patterns at northward-oriented IMF are not well defined. For example, near noon sunward flows (reverse flows) often deviate from the midnight-noon meridian and the amount of deviation can be as large as several hours of magnetic local time. Over the last several years, significant data on reverse flows have been accumulated in the Canadian sector of Arctic where three PolarDARN...
Accurate, quantitative measurements of radiation fields are essential prerequisites for the safe and effective use of ionizing radiation in diagnostic and therapeutic medical applications. Common examples of radiation detectors include: ionization chambers, thermoluminescent dosimeters (TLDs), films and various electronic devices. Semiconductor dosimeters such as p/n type silicon diodes and...
In a recent paper, we have shown that dynamical spin effects are important to describe pion observables within holographic light-front QCD. The relative importance of such effects was freely chosen to fit the data. We now show that these dynamical spin effects can actually be theoretically constrained if we dare to extrapolate the use of an exact QCD relation away from the chiral limit....
Stable isotope abundances vary in nature due to differences in zero-point energies of the binding site of a molecule upon isotopic substitution. This causes isotopes of an element to participate in reactions with different rates resulting in a redistribution of the isotopes in a system. Although the range in relative isotopic abundance of copper in natural materials is narrow, < 1.0%,...
In a magnetically confined fusion reactor, the density and the temperature profiles are highly peaked at the core of the reactor and the fusion reactions occur mostly at the center. Unlike the fission reactors with the fuel bundle inserted in the reactor core, the fusion fuels have to be continuously injected from the outside to maintain the desired density in the reactor. The primary...
We have proposed, in a previous CAP conference, an erfc potential that can be integrated in a symmetric metric to define the space-time surrounding a static symmetric massive object. The geometry described by this metric provides a unique representation of a static symmetric stellar system that is continuous over all the coordinate ranges. No discontinuities and no singularities, coordinate or...
We compute masses of light quarkonium and strangeonium $0^{+-}$ hybrids using Gaussian sum-rules. Correlation functions account for condensates up to dimension-six and are calculated at leading-order in $\alpha_s$. Our analysis indicates that the resonance signal strength in this channel is distributed over a wide range, inconsistent with a single narrow resonance. A single wide resonance...
The European Space Agency’s trio of Swarm were launched in November 2013 to measure the environment around Earth using a suite of instruments. Each satellite is equipped with two Langmuir probes that run in parallel and have different coatings. One is gold plated and the other has a titanium nitrate coating. This configuration on each satellite provides an opportunity to study if and how...
One of the Grand Challenges for humanity in the 21st Century is sustainable energy generation and storage. This translates to major opportunities for AFM to help addressed relevant materials issues if ultrafast time resolution in the localized measurement of electronic properties can be achieved. In this presentation, I will give an overview of our recent successes at characterizing surface...
Cellular reprogramming is a source of induced pluripotent stem cells, but this process remains incompletely understood. The current theory of equipotency during reprogramming, in which all cells are equally inducible, argues that clone size distributions arise only from stochasticity in the system. However, large variability is seen in experiments. Our null, stochastic model, does not agree...
In this work, we consider the Korteweg-de Vries equation and its variants which are third order nonlinear partial differential equations. It originates from many physical phenomena, for example, the flow of liquids containing gas bubbles, in the study of the propagation of waves in an elastic tube filled with a viscous fluid and also for the description of shallow water waves on viscous fluid....
Colloids are small particles with diameters that lie within the nanoscopic and microscopic domains. Recently, research has focused on deformable or soft colloidal particles, such as microgels and star polymers, which show fascinating behaviour such as jamming and glass formation in dense dispersions. I will describe a new type of soft colloidal particle, phytoglycogen, which is produced in the...
Fluid turbulence has been called the “last unsolved problem of classical physics” and the measurement of this phenomenon presents a formidable challenge. Turbulent systems are highly sensitive to perturbations, and so a non-invasive technique is needed to probe their properties. Turbulence is also difficult to fully characterize, particularly in the case of anisotropic turbulence. Magnetic...
Precision low-energy experiments in electroweak electron-proton interactions are a vital complement to direct tests of the Standard Model. They also give information about the structure of the proton. In parity-violating electron-proton scattering, recent results reported by the Qweak collaboration, and the proposed Møller experiment at Jefferson Lab, have the potential to give constraints on...
In this presentation, I will present the many-body interactions in solids studies by high resolution ARPES. High-resolution angle-resolved photoemission spectroscopy studies of Fe (1 1 0)；Ni(110) and other 3d single crystals have been conducted to clarify the role of many-body interactions acting on the quasi-particles at the Fermi level at low temperatures.
Proton therapy is gaining popularity as a tumor irradiation method due to the superior dose distribution offered by heavy charged particles. The subject of range and dose verification has been approached from several angles and fields.
Upon interaction with low-energy protons, certain nuclei undergo fusion-evaporation reactions. The resulting reaction products emit a cascade of...
In the strong light-matter coupling regime, energy is reversibly exchanged between the electromagnetic field and the polarization field. A microscopic description of this regime is usually presented in terms of hybrid light-matter quasiparticles called polaritons. These quasiparticles have a number of fascinating properties such as an ability to undergo Bose-Einstein condensation at high...
Most departments rely on student evaluations of teaching (SET) when trying to determine an instructor's teaching effectiveness. Some even focus on a single number, the "overall mark" given by students. How can we do better? We want to know which methods you use and why, and if you are satisfied with the information they provide. We especially want to hear from you if you are using Peer...
There has been an exciting recent development in auroral research associated with the discovery of a new subauroral phenomenon called STEVE (Strong Thermal Emission Velocity Enhancement). Although STEVE has been documented by amateur night sky watchers for decades, it is a new upper atmosphere phenomenon. Observed first by amateur auroral photographers, STEVE appears as a narrow luminous...
Since the first demonstration of atomic resolution in ultra-high vacuum more than twenty years ago, frequency modulation-based noncontact atomic force microscopy (FM-NC-AFM) has significantly matured and is now routinely applied to study problems that benefit from high-resolution surface imaging. In FM-NC-AFM, control of the tip’s vertical position is accomplished by detecting a shift in the...
The Canadian Light Source (CLS) located in Saskatoon on the campus of the University of Saskatchewan has been in operation since 2005. Upon completion of the Phase III beamlines in 2019, the total number of end-station will be over 25, leaving space for only one last beamline. In light of the growing demand for synchrotron light and the advances in accelerator physics in the past 20 years...
Plastic scintillation detectors (PSD) are excellent candidates for in-vivo dosimetry due to their small size, sensitivity and potential for real time readout. One challenge associated with PSD dosimetry is the contamination of the scintillation signal with Cerenkov radiation and fluorescence. An implicit assumption made with PSDs is that the spectral components of the scintillator and fiber...
A prototype clinical study is being developed to assess pre-adult patients with hemophilic arthropathy. Patients with this condition experience pain in ankle, knee, wrist, or elbow joints due to joint bleeds. Typical ultrasound exams involve probe to skin contact to generate an image, which places a moderate to high level of pain on the effected joint. To overcome the physical touch of an...
Light incident on nanoscale metal-insulator-metal (MIM) plasmonic gratings generates surface plasmon polaritons (SPPs) which resonate and propagate within the grating structure. A variation in the SPP resonant wavelength is achieved by gradually increasing the width of the MIM grooves symmetrically about a central groove to create a graded grating, which leads to a gradient in the effective...
Three-pulse multidimensional coherent spectroscopy allows for isolation of zero-, one- and two-quantum pathways for separate and coupled, as well as their homogeneous and inhomogeneous linewidths [1]. Excitons and biexcitons are examined in semiconductor quantum wells to determine the lineshapes and quantum pathways associated with the optical excitation. These result are compared and...
We know that the Standard Model of Particle Physics is incomplete - for example, we still do not understand the nature of dark matter, matter- antimatter asymmetry or hierarchy of the three generations of elementary particles. There is a wide spectrum of experiments searching for new particles beyond the Standard Model (BSM), broadly defined by three domains - Energy, Cosmic and Precision...
After four years in orbit, the Swarm Electric Field Instruments have contributed to dozens of scientific studies on topics that include the electrodynamics of auroral arcs, supersonic flow channels associated with region 1/2 currents and sub-auroral ion drifts, polar cap patch dynamics, Poynting flux, and magnetosphere-ionosphere coupling via Alfven waves. This talk will overview capabilities...
When orbitals are already occupied by one electron, the addition of a second charge to that position in space entails overcoming the Coulomb repulsion between the charges. This on-site Coulomb repulsion is often characterized by the so-called Hubbard U: the energy difference between the doubly negative and charge neutral state. As charges move from site to site in a material they must...
We present recent results from a preliminary inter-satellite comparison of ionospheric flow measurements from the European Space Agency Swarm mission. Swarm consists of three identical satellites in near-polar circular orbits in the topside F region ionosphere. Each spacecraft carries a set of two orthogonal thermal ion imagers designed to measure full ion flow vectors twice per second. The...
TRansmit Array Spatial Encoding (TRASE) is a Magnetic Resonance Imaging (MRI) method which uses phase gradients of the $B_1$ field – rather than magnitude gradients of the $B_0$ field – to achieve spatial encoding. The potential benefits and limitations of this technique are still being explored in both conventional and low-field magnets. This work designs a highly homogeneous, low-field...
MacSANS is a new small angle neutron scattering (SANS) beamline currently under construction at the McMaster Nuclear Reactor, a 5 MW research reactor based at McMaster University in Hamilton, Ontario. This beamline is designed to study a broad range of materials, including biological membranes, polymers, superconductors, and novel magnets, by probing structure and magnetism on length scales...
Traditional point sources of neutrons produce free neutrons in isotropic directions and with kinetic energy in the MeV energy domain. These neutrons are too fast for many applications as the probability of interaction between neutrons and surrounding matter is often higher at low neutron energies. Therefore, to optimize interaction between neutrons and its environment, these neutrons are...
Revealing the local electronic properties of surfaces and their link to structural properties is an important problem for topological crystalline insulators (TCI) in which metallic surface states are protected by crystal symmetry. As a first step toward this goal, we have studied the epitaxial growth of SnTe films and characterized their structural and electronic properties by molecular beam...
Recent studies have suggested that structured laboratory activities may not be the most effective way of teaching content and concepts to first year physics majors. We examine and extend that investigation to a high-enrollment Introductory Physics for the Life Sciences course. Using a varied laboratory curriculum, we correlate quiz marks, exam marks, and student attitudinal data to determine...
Many extensions to the Standard Model predict new particles at the TeV scale which decay to pairs of electro-weak gauge bosons. The ATLAS detector is one the most sensitive probes for these scenarios because it studies the LHC collisions which have unprecedented center of mass energies and luminosity. In conjunction with new experimental techniques for identifying the hadronic decays of weak...
Electroless copper films are used in printed circuit board industry to establish a conductive layer on insulating substrates. These films may have failures (voids, blisters) related to stress and/or hydrogen co-deposition in Cu films. Typical methods to determine amount of hydrogen are destructive and indirect. We have developed a time-resolved method to measure amount of hydrogen released...
We describe a monolithic thin-film buckling process used to fabricate arrays of high-finesse, tunable, curved-mirror Fabry-Perot cavities on a chip. Arrays of small-mode-volume cavities exhibit good uniformity and nearly reflectance-limited finesse. The process has been adapted to a variety of thin film material combinations, for operation throughout the visible and near-infrared regions. ...
The GlueX experiment is located in the recently constructed experimental Hall D at Jefferson Lab (JLab), and provides a unique capability to search for hybrid mesons in high-energy photoproduction, utilizing a 9 GeV linearly polarized photon beam. Commissioning of the Hall D beamline and GlueX detector was recently completed and the data collected in the spring of 2017 officially began the...
It is now 100 years since Planck received a Nobel Prize for describing blackbody radiation. It is 75 years since McKellar found a background temperature of molecules in space and 55 years from the recognized discovery of the cosmic microwave background. Measurements of the spectrum, and the the anisotropy of the intensity and polarization patterns of the CMB have told us about thermal...
Physics is an empirical science. Therefore, learning physics must include learning how to design and conduct experiments, analyze and interpret data, and revise models and apparatus. Physics lab courses at the introductory and upper-division levels are one of only a few opportunities for students to engage in these authentic physics practices. For many students, instructional labs are the only...
The recent discovery of the Higgs boson (h) is an affirmation of the
Standard Model (SM) of particle physics and concludes several decades of
experimental searches. However, the experimental investigation of its
properties has just begun. Current measurements of h properties permit
the fraction of h decays to Beyond-Standard-Model (BSM) particles to be
as high as approximately 30%. These...
Percolation is a geometric condition that occurs naturally in the growth of two-dimensional (2D) films (and in many other contexts). Atoms that are deposited on a substrate aggregate to form isolated islands whose size bounds the range of correlated behavior, or correlation length, of the system. At greater deposition the islands coalesce, and at a critical fractional coverage of the...
The way that water wets a surface can be controlled by manipulating surface energies and/or surface topography. Although these factors can be controlled very well on the lab scale for certain kinds of materials, it is very challenging to achieve good control on compositionally heterogeneous surfaces such as stainless steel. Here, we show that mildly alkaline electrolytes can be used to...
As first discussed by U. Fano in the 1940’s, the statistical fluctuation of the number of e-/ion pairs produced in an ionizing interaction is known to be sub-Poissonian, the dispersion being reduced by the so-called “Fano Factor”. Despite this knowledge, the Poisson distribution is commonly used to model the quantization of ionizing processes while the effect of the reduced dispersion is...
Advances in THz generation have enabled a wide range of new scientific tools that probe previously inaccessible dynamics in materials. In the area of scanning tunneling microscopy the capability of generating large amplitude THz pulses have enabled practical ultrafast scanning tunneling microscopy experiments. In a THz-coupled scanning tunneling microscope (THz-STM), THz pulses couple to the...
Quantum chromodynamics (QCD), the fundamental theory of the strong interaction, tells us that when quarks are close together (high energy) the interaction is feeble but when they are far apart (low energy) the strong force is intense. Currently, QCD can accurately describe the high energy regime, but calculations are difficult in the non-perturbative, low energy regime. At Jefferson Lab...
While quantum properties of light promise much-needed enhancements to metrology, further development of quantum light sources are needed to readily harness energy-time correlations for applications in imaging and spectroscopy. Spectrally broadband photon pairs, generated from the process of spontaneous parametric down-conversion (SPDC), require tight energy-time anti-correlations in order to...
The molybdenum oxide bronzes are a family of low-dimensional materials exhibiting interesting behavior including superconductivity, charge-density wave states, and metal-insulator transitions. After considerable study, there is still no firm consensus regarding a theory to explain their unique features. We have synthesized single crystals of blue bronzes A0.3MoO3 (A=K, Rb) and purple bronzes...
I will explain how observations of the cosmic microwave background constrain theories of the early universe. I will then present some cosmological models whose predictions are in agreement with current observations, and explain how future observations may be able to differentiate between these models.
Throughout Run II ATLAS has maintained an extensive, varied program of searches for physics beyond the Standard Model. Searches for supersymmetry cover strong and electroweak production as well as R-parity violating scenarios, while Exotic analyses search for heavy bosons, dark matter mediators, exotic Higgs production, and much more. This talk will show highlights of the Run II search results...
Undergraduate students are typically introduced to advanced optical instrumentation during their senior physics and chemistry courses. Experiments available from educational companies typically use low end optics in customized formats, beneficial for younger students eager to explore the physical and chemical phenomena under study. However, these setups prevent senior students from learning...
Exclusive meson electroproduction at different squared four-momenta of the exchanged virtual photon, $Q^2$, and at different four-momentum transfers, $t$ and $u$, can be used to probe QCD's transition from hadronic degrees of freedom at long distance scale to quark-gluon degrees of freedom at short distance scale. Backward-angle meson electroproduction was previously ignored, but is...
Single photons play an important role in several quantum technologies, acting as flying qubits to transfer quantum information for both computing and communication applications. In many cases, it is acceptable for these single photons to be produced randomly, as long as they are accompanied by heralding signals announcing their creation. Such heralded single photons sources are straightforward...
The intent of this project was to compare the electrical outputs of two types of solar cells under different treatments in a high altitude and low atmosphere environment. Four cells were compared: a standard photovoltaic (PV) cell, a Gallium Antimonide (GaSb) thermophotovoltaic (TPV) cell sensitive to infrared radiation, and another pair of PV and TPV cells under Fresnel lenses treatment...
It is well established that the near singularity dynamics of a Bianchi IX spacetime can be characterized as a series of transitions between Kasner solutions (BKL map). The majority of results obtained in this limit rely on an (intrinsic) geometric time variable (f(g)). This time variable is not suitable to determine the intermediate regime dynamics of Bianchi IX with matter. We study Bianchi...
A trace gas detection device has applications in environmental monitoring and healthcare. Authors will present the working principle of a trace gas sensor operating at room temperature, which was developed using the intracavity absorption spectroscopy method. In the system, a gas cell based on hollow core photonic crystal fiber (PCF) was used as an intracavity cell. The experiments were...
Roll-annealed (RA) copper foils are commonly used in the printed circuit industry as flexible conductive base materials. The RA process produces foils with the crystallites aligned in particular directions. RA foils used in applications have either {100}<001> “cube” texture, or a mixture of {112}<111> “copper”, {123}<634> “s” and “cube” textures. Manufacturing circuits requires the...
A common complaint from students in undergraduate physics laboratories is that they spend too much time propagating uncertainties and not enough time understanding the physics. We have worked with students at Queen's University to develop QExpy, a python package designed to facilitate undergraduate physics laboratories, while easing students into learning to program in python. The open source...
The Solenoidal Large Intensity Device (SoLID) is a new detector planned for installation at Jefferson Lab's (JLab) Hall A, as part of the 12 GeV era of JLab physics. This detector will have a large acceptance, and be capable of operating at high luminosity, enabling multiple new experiments probing the inner structure of nucleons. We have received funding from CFI and Fedoruk Institute to...
The strong interactions between Rydberg atoms provides an exciting platform for quantum nonlinear optics. Rydberg blockade (where a cloud of many atoms is unable to support more than a single excitation due to dipole interactions) combined with electromagnetically induced transparency (EIT) (where on-resonant absorption is suppressed due to the presence of a second coupling field) has been...
The structure and properties of perovskite substrates have attracted substantial interest due to material’s popularity as a substrate for complex oxide epitaxy [1,2]. Strontium titanate (SrTiO3) is among the most popular perovskites, with film quality dependent on the structure of the substrate at the beginning of the growth process. Here, we examined the surface structure of SrTiO3 (100)...
Double-beta (ββ) decay measurements are a class of nuclear studies with the objective of detecting the neutrinoless (0ν) decay variants. $^{96}$Zr is of particular interest as a ββ decay candidate as it has one of the shortest ββ decay half-lives and largest Q-values. A geochemical measurement of its ββ decay half-life was previously performed by measuring an isotopic anomaly of the $^{96}$Mo...
The cosmological constant problem is described as one of the greatest crises of modern physics. The conventional problem is posed in the framework of quantum fields on a fixed background and their semiclassical backreaction on gravity. In this talk, expanding on a recent proposal, I will argue that this problem does not arise in a fully non-perturbative gravity-matter framework. I will show...
Development of Utility Friendly Safe Olivine Based ESS in Esstalion Technologies.
K. Zaghiba, Y. Asakawa, J. C. Daigle, M. Yasudab, and S. Uesaka*b
§ Esstalion Technologies Incorporated, 1804 Lionel-Boulet Blvd., Varennes, Quebec, Canada, J3X 1S1
a) Center of Excellence I Transportation Electrification and Energy Storage (CETEES), Hydro-Québec, 1800 Lionel-Boulet Blvd., Varennes,...
One way to motivate students to learn physics is to use examples of daily life where it applies, and sports are a good example. Ice hockey is particularly rich in the variety of physics elements it contains, from the biomechanics of skating, to shooting and puck aerodynamics, to player collisions. With the help of physics and statistics, I will tackle fun questions like Can a hockey puck...
Miniaturized biosensors are essential components of continuous health monitoring systems, which are expected to significantly impact human health management. Biosensors integrate biorecognition elements with transducers to detect the presence, absence, and quantity of biologically-relevant elements. Nanoscale materials play a critical role in enhancing the sensitivity and specificity of these...
The use of enriched liquid Xe-136 (LXe) offers significant advantages to search for double beta decay processes. A discovery of the neutrinoless mode (0vbb) would reveal new properties of neutrinos including first measurement of its mass scale, evidence that they are their own antiparticles, and a first observation of lepton number violation.
The Enriched Xenon Observatory (EXO) employs a...
The Martian atmosphere exhibits more dynamical variability than the terrestrial atmosphere with large amplitude tides and gravity waves in addition to the seasonal dust storms. To date, there have not been dedicated wind measurements from orbit around Mars and there is some evidence that the winds do not match expectations from models. As with the terrestrial atmosphere, airglow is one means...
Superpositions of macroscopically distinct quantum states, introduced in Schrödinger's famous Gedankenexperiment, are an epitome of quantum ``strangeness" and a natural tool for determining the validity limits of quantum physics. The optical incarnation of Schrödinger's cat – the superposition of two opposite-amplitude coherent states – is also the backbone of quantum information processing in...
The Belle II electron-positron collider experiment at the KEK laboratory in Japan is undergoing detector commissioning this year, with first data taking using the full detector planned for early 2019. I will present the physics goals and current status of the project with a summary of recent activities relating to detector construction and the commissioning of the SuperKEKB accelerator. I will...
Molybdenum disulfide was produced in an exfoliated state by combining molybdic acid with an excess of thiourea at 500°C under nitrogen. Nanocomposites of the conducting polymer polyaniline (PANI) and exfoliated MoS2 were then synthesized. The nanocomposites with varying percentage by weight of exfoliated MoS2 were characterized using powder X-Ray diffraction, electrical conductivity...
This talk will look at cost effective and environmentally friendly surface treatments to improve the corrosion resistance of SS 316. Mechanically polished samples were treated by heating in deionized water, a hydrogen peroxide solution, electropolishing and heat treating in an oven. Cyclic voltammetry and optical microscopy were used to measure corrosion on the samples in a 0.9% NaCl solution....
Antimicrobial Peptides (AMPs) are small chains of between 10 and 50 amino acids with the ability to kill pathogens such as bacteria, fungus, viruses, and even cancer cells. AMPs are one of many mechanisms that living organism have developed to protect themselves from pathogenic microorganisms. Most research in AMPs is focused on understanding the mechanism or mechanisms that AMPs use to kill...
Gauge theories are fundamental to our understanding of interactions between the elementary constituents of matter as mediated by gauge bosons. However, computing the real-time dynamics in gauge theories is a notorious challenge for classical computational methods. In the spirit of Feynman's vision of a quantum simulator, this has recently stimulated theoretical effort to devise schemes for...
Nitinol (nickel-titanium) alloys have a unique property, superelasticity, which allows the manufacture of minimally invasive self-expanding stents. Nitinol is approximately composed of 50% nickel, which is known to be toxic. Therefore, corrosion resistance is key to the good biocompatibility of this material, especially considering the aggressive environment of the body. We tested the effects...
Tuning positive electrode materials in lithium-ion cells provides a promising means for lowering cost of materials while maintaining safety and energy density standards. Due to the rising cost of cobalt, it is important to find less expensive alternatives. Here we present results from first-principles computations within the formalism of density functional theory examining changes in...
The nEXO Collaboration is developing a proposal for a 5-tonne experiment with initial neutrinoless double-beta decay sensitivity approaching to $10^{28}$ years. The nEXO detector will be a homogeneous liquid xenon (enriched to 90% in $^{136}$Xe) time projection chamber inspired by the highly successful EXO-200 detector. Energy resolution, event topology, and event localization in the large...
We study the potential for using CsI(Tl) pulse shape discrimination in order to improve particle identification at high energy electron-positron collider experiments such as the Belle II experiment. Using neutron and proton testbeam data collected at the TRIUMF Proton Irradiation Facility we analyze the scintillation pulse shape differences between photon and hadron energy deposits and...
I will present my perspective on using physlets and physclips in introductory physics courses. The physclips have been developed at the School of Physics, University of South Wales, Australia, along with other multimedia resources. The physclips were downloaded from open sources such as: http://www.compadre.org/physlets/ or were available as PhET simulations in textbooks' online resources....
The Waves Michelson Interferometer (WaMI) is designed to make wind measurements of the atomic oxygen green line (557.7 nm) emission, a molecular oxygen line at 1264 nm, and a hydroxyl line at 1315 nm. These emissions provide a capability for probing the dynamics of the middle atmospheres of the terrestrial planets. The special feature of the design of this instrument is that the back mirror is...
Our current knowledge of particle physics is best described by the standard model (SM). Despite this, astronomical observations of dark matter made over the past few decades mean that the SM must be incomplete. New models are now motivating the possibility of dark matter being governed by the an extended $SU(3)$ gauge theory resembling Quantum Chromodynamics (QCD) for the strong force. This...
The hydrogen atom has played a fundamental role in the development of our understanding of the universe and of quantum mechanics. This makes antihydrogen a natural candidate for testing symmetries between matter and antimatter. The goal of the ALPHA (Antihydrogen Laser PHysics Apparatus) collaboration is to synthesize, trap, and study antihydrogen atoms. ALPHA has made significant progress...
Bacterial pathogens can be differentiated via an elemental analysis technique known as laser-induced breakdown spectroscopy (LIBS). This technique can be of use in the rapid identification of bacterial pathogens, for which there is a high demand, particularly in a clinical setting. The identification of bacteria with LIBS must therefore be possible with the types and numbers of bacterial cells...
A portion of upper main-sequence stars, called chemically peculiar (CP) stars, show significant abundance anomalies mainly due to atomic diffusion of chemical elements within the stellar atmospheres of these stars. Slowly rotating CP stars may have hydrodynamically stable atmospheres where a competition between the gravitational and radiative forces launches the mechanism of atomic diffusion...
Problem solving is a major stumbling block in the introductory physics courses in both STEM and life science programs. Our students have been provided with an optional tool to supplement and reinforce lecture and in-class tutorial instruction. A series of video tutorials were created to address curriculum topics covered in first year physics courses. The tutorials target the topics that are...
Lithium ion batteries are used in consumer electronics, electric vehicles and grid energy storage.1 New positive electrode materials like LiNi1-x-yMnxCoyO2 (NMC) are required to increase energy density, lower cost and increase lifetime. Conventional NMC has large secondary particles (10 - 15 µm) made of agglomerates of small grains (~ 200 - 500 nm) and is thus called polycrystalline NMC.2 ...
Periodic wrinkling of a rigid capping layer on a deformable substrate is a ubiquitous example of pattern formation in nature. Many experiments have studied wrinkle formation during the compression of thin rigid films on relatively thick pre-strained elastic substrates. The resulting wrinkling wavelength and amplitude can be predicted by minimizing the bending energy of the rigid film and the...
ChromaStar is a responsive physical model star and exo-planet life zone equipped with a suite of virtual astronomical instruments. It runs in a web-browser on any commonplace personal computing device and allows for PER-based methods and lab assignments when teaching astronomy from the High School to the upper University level. Advanced students can access the code through the browser’s...
To further progress the adoption of electric vehicles and other high power energy storage applications, it is desirable to develop lithium-ion cell chemistries that offer longer lifetimes at high temperatures and cell voltages, without significantly increasing the cost. The introduction of sacrificial electrolyte additives on the order of a few weight percent is a practical method to form...
The best trapped-ion atomic clocks today are accurate to better than one part in $10^{18}$ [1]. To improve their accuracy even further, we must consider small perturbations of the clock frequency due to collisions between the clock ion and background gas atoms. Our group has recently developed a simple analytic formulation [2] to evaluate the collisional frequency shift (CFS) based on a...
At the large hadron collider, most Z bosons are produced in a qqZ vertex, sometimes in association with jets produced via the strong interaction. A more rare production mode for Z bosons is through a triple gauge coupling via a process called vector boson fusion (VBF). This VBF Z process is similar in nature to VBF Higgs production, which is of great interest and is being studied by large...
Two high resolution and high signal to noise ratio spectra of HD176232 have been analyzed to study the chemical abundances in atmosphere of this star using the ZEEMAN2 code. These spectra were recently obtained with the spectropolarimeter ESPaDOnS at the Canada-France-Hawaii telescope (CFHT) in the frame of the project VeSElkA. The project’s objective is the search for signatures of vertical...
G protein coupled receptors (GPCRs) are a superfamily of membrane receptors known for high signal transduction efficiencies. One of the key aspects of the GPCR signaling mechanism is the coupling interaction between the receptor and the G protein in response to external stimuli. We examined the pre-stimulus receptor-G protein coupling state by single-particle tracking (SPT) of M$_2$ muscarinic...
Vanadium oxide (VO2) thin films have been studied extensively because of their thermochromic properties, i.e. reversible optical change as a function of temperature. These reversible optical changes, also accompanied by electrical changes make these films interesting from application point of view. Many applications such as smart windows, sensing devices, variable reflectance mirrors and many...
We think that black holes are ordinary quantum systems with a finite number of microstates, when we view them from the outside.
A pair of black holes can then be entangled with each other. A special entangled state of this kind can be described by a geometry similar to the maximally extended Schwarzschild black hole. This geometry is a non-traversable wormhole.
We will discuss how to make...
Second harmonic generation (SHG) is a non-linear optical process where two photons from the pump wave interacting with a non-linear material are combined to generate a new photon, with twice the frequency of the initial ones. The use of organic crystals for SHG is appealing, as the nonlinear coefficients of these crystals are much greater than those of standard inorganic materials, especially...
Laser-induced breakdown spectroscopy (LIBS) is an elemental analysis technique in which a high powered laser is used to create a plasma on the surface of a sample. The light emitted from this plasma through a de-excitation process is then collected and used to spectrally analyze the sample. Two techniques that can improve the signal-to-noise ratio of LIBS spectra are dual-pulse LIBS, which...
In order to adequately understand the effects that energetic particle precipitation bears on radio wave absorption, we have analysed cosmic noise absorption (CNA) measured by the imaging riometer at Kilpisjarvi, Finland (IRIS) during 1996-2011. We analysed periods of co-rotating interaction regions(CIR) occurring as a result of the interaction of high speed solar wind streams emanating from...
Physics for Modern Technology is a newly established, very applied bachelor's degree in physics and instrumentation at Kwantlen Polytechnic University, a teaching-led university in Greater Vancouver.
Modelled after similar programs running successfully in Europe, this program is aimed at students who wish to work in high tech industry after graduation. Although progression to graduate...
A plane polarized electromagnetic (EM) wave that propagates through a plasma, (anti-)parallel to a magnetic field, experiences a gradual rotation of its plane of polarization called Faraday rotation (FR). Automatic Dependent Surveillance Broadcast (ADS-B) signals are linearly plane polarized and therefore are susceptible to FR as they traverse the ionospheric plasma, where they encounter a...
The Michelson Interferometer for Airglow Dynamics Imaging (MIADI) is a field widened Michelson interferometer which provides images of wind using Doppler shifts in interference fringes from terrestrial airglow emissions. Although it is thermally compensated by using different glasses, some residual temperature dependence remains. Close examination of the interference fringes using a fixed...
In a real-world situation, a battery is not cycled continuously until death nor stored endlessly at top of charge. Test conditions should mimic real-world situations to better understand different failure mechanisms occurring within cells of the same build and electrolyte. Three complimentary tests are proposed to probe cycle-dependent and time-dependent aging under a spectrum of voltage and...
Metallic Li is considered as the promising anodes for next generation Li-metal batteries including Li-S, Li-air and all solid-state batteries. However, it is still a crucial problem of Li dendrite growth and large volume change during the stripping/plating process. In our study, the advanced atomic/molecular layer deposition (ALD/MLD) is used to deposit protective coatings on Li metal with...
Instability of GaAs and AlGaAs in an aqueous environment increases drastically following illumination with photons of energy exceeding bandgap of these materials. We have investigated the dynamics of photon-induced dissolution of GaAs/AlGaAs nano-heterostructures in deionized water (DI H2O) and ammonium hydroxide (NH4OH) environments by employing inductively coupled plasma mass spectrometry...
In the quest for high performance materials for energy storage, a comprehensive toolbox of characterization techniques - both experimental and theoretical - is an absolute necessity. In recent years, many techniques have been increasingly focussed on combining observations of material structure, composition, and dynamics to develop a complete picture on how various material properties affect...
Sometimes lithium-ion cells show a very insidious type of failure where they display close to 100% of their capacity for about 1000 charge-discharge cycles and then lose most of their capacity in only 100 cycles or so with very little warning to the user. This is called “rollover failure”. Experimental observations show that the likelihood of rollover failure increases with upper cutoff...
Lithium Ion Batteries are widely used in a large variety of consumer products. With the rise in use in electric vehicles, increasing the energy density of LIBs is a priority. One way of accomplishing this is to increase the charge cutoff potential. However, this results in significant deterioration of the LIBs caused by side reactions between the electrolyte and the electrode. A possible...
Carbon-based nanomaterials are key components in energy storage devices. Their functions can be tailored by adjusting or developing new synthesis pathways. In this study, two living radical polymerization techniques, an electrochemically-aided atom transfer radical polymerization (e-ATRP) and reversible addition chain transfer polymerization (RAFT), were applied for grafting of carbon...
Dissociative excitation of adenine (C5H5N5) into excited atomic fragments has been studied in the electron impact energy range from threshold to 400 eV. A crossed beam system coupled to a vacuum ultraviolet (VUV) monochromator is used to study emissions in the wavelength range from 90 to 200 nm. The beam of adenine vapor from a stainless steel oven is crossed at right angles by the electron...
Nickle-rich LiNixMnyCozO2 (x + y +z = 1) (NMC) (Ni content higher than 60% of the total transition metals) is one of the most promising positive electrode materials for lithium-ion cells due to its high specific capacity of up to 220 mAh/g. Conventional NMC materials such as LiNi0.4Mn0.4Co0.2O2, LiNi0.5Mn0.3Co0.2O2, LiNi0.6Mn0.2Co0.2O2 etc. have more than 20% Co among the transition metal...
Improving the cost, lifetime, and energy density of lithium-ion cells is critical in the transition away from fossil fuels for energy production and transportation. Increasing the operational voltage of a lithium ion cell is one way to increase energy density and decrease cost. However, traditional solvents used in lithium-ion electrolytes are not stable at these potentials, causing what are...
Normal Li-ion cells with a positive electrode and a negative electrode normally have a voltage near 4.0 V. There are many surprising things about lithium-ion cells. One of these is that unwanted chemical reactions between one charged electrode (say the positive) and the electrolyte can create reaction products that migrate to the other electrode (say the negative) and affect it dramatically...
Michael Bauera, Eric Logana, Lauren Thompsonb, J.R. Dahna,b
aDepartment of Physics and Atmospheric Science, Dalhousie University, Halifax B3H 3J5, Canada
bDepartment of Chemistry, Dalhousie University, Halifax B3H 4R2, Canada
Li-ion cells contain liquid electrolyte that degrades over the course of their lifetime. High...
Lithium-ion cells are complex electrochemical system and various physical properties can be measured, giving valuable insights into their behavior, state-of-health, degradation mechanisms, etc.. However, many such insights remain unexploited because of the difficulty of relating the raw data to the variables of interest. This is a setting well suited to Machine Learning. This talk will take as...
The widespread adoption of electric vehicles over gas-powered transport is essential to our sustainable future. Consequently, the lithium-ion batteries used for electric cars are receiving more and more attention. Lithium-ion cells with LiNi0.8Co0.15Al0.05O2 (NCA) positive electrodes have been observed to lose capacity during their lifetime as a result of impedance growth.1,2 Understanding the...
Improving the energy density, cost and lifetime of current lithium-ion batteries is vital for the electric vehicle industry and for grid energy storage. It is known that the composition of the electrolyte solution in lithium-ion batteries can dramatically affect their performance. For that reason, it is common to add a small amount of additives to the electrolyte solution to limit impedance...
Quasi-2D materials are composed of stacks of atomically thin layers. While individual monolayers have unique thermal and electronic properties on their own, quasi-2D materials introduce an array of new characteristics, such as anisotropic transport properties and thickness-dependent properties, which have important applications in optoelectronics and thermoelectrics. Our group is particularly...
More than half of the energy produced worldwide is currently lost as waste heat and recovering a
fraction of the lost energy would have an enormous impact on global climate change. In this sense, thermoelectric materials can convert waste heat to useful electricity. However, because of their
low efficiency, high cost, and use of scarce resources, thermoelectric materials are not...
Pyrrole and furan, two aromatic five-membered ring molecules, have been the subject of extensive ab initio and experimental studies. We have taken Fourier transform far-infrared spectra of these molecules at the Canadian Light Source. Two fully-entangled vibrational bands of furan, n8 and n21 at ~ 870 and 873 cm-1, that are present in the spectra show some perturbations and interact with each...
Fourier Transform Infrared (FTIR) spectroscopic techniques are well established for their ability to identify mixtures of compounds and polymorphs in solid materials. These spectra can be recorded using either optical or acoustic detectors. Transmission FTIR spectroscopy (FTIR-TR) has been used in the past to access crystallinity differences in archaeological and lab-produced calcium carbonate...
Thermoelectric materials can be used to construct solid-state devices that convert excess heat into electrical power. Because roughly half of all energy generated is lost as waste heat, efficient thermoelectric devices represent an opportunity to significantly reduce global energy production. However, predicting whether a material will exhibit efficient thermoelectric conversion is a highly...
With the aid of different polymer materials, intermolecular interactions, energy levels, and optical absorption spectra of polymers and fullerenes can be adjusted so as to enhance the efficiencies of heterogeneous organic solar cells. It is known that computational simulations such as density functional theory (DFT) can play an important role in identifying polymers with favourable properties...
A number of recent calculations and experiments have identified that strain and finite size effects are important contributions that influence the stability of the magnetic textures in MnSi thin films. Both of these effects play an important role in MnSi films grown on Si substrates and have an important influence on the magnetic phase diagram. However, there continues to exist controversy...
The broken inversion symmetry in non-centrosymmetric magnetics produces a chiral interaction responsible for the formation of stable nanoscale magnetic solitons in these materials, known as skyrmions. The inverse tetragonal Heusler alloys possess a D2d point group symmetry that gives rise to antiskyrmions, recently discovered in Mn1.4PtSn [1]. We are investigating the related family of...
Liquid electrolytes are essential to all battery systems, yet little is known of the changes that occur during the lifetime of a cell. It is certain that dramatic changes to the electrolyte of a Li-ion cell occur during operation because sometimes cells opened at the end of life appear “dry” (i.e. no liquid remaining) even though they were filled with substantial liquid electrolyte upon...
Graphite is used as the negative electrode in most Lithium-ion battery chemistries. As demand for Li-ion batteries grows, so does demand for graphite. To help satisfy demand Elcora has acquired a vein graphite mine in Sri Lanka. This talk will discuss the journey graphite takes from the mine to a commercial cell.
Several topics will be discussed. For example:
• Graphite mining...
TiFe is one of the good candidates for the solid-state hydrogen storage. Despite having fast kinetics and fairly good capacity, it’s first hydrogenation is difficult. In this study, we investigated the effect of addition of lanthanum on the hydrogen storage properties of TiFe alloy. As the melting point of lanthanum is much lower than the ones of the other two elements, synthesis by casting...
As lithium ion battery technology expands into more demanding applications such as electric vehicles, attention has shifted away from the conventional LiCoO2 positive electrode material. Instead, nickel-rich materials such as LiNi1-x-yMnxCoyO2 (NMC) and LiNi1-x-yCoxAlyO2 (NCA) have become attractive due to their lower cost, increased lifetime and increased safety.
Coprecipitation is a common...
Redox flow batteries (RFBs), as large scale stationary energy storage systems, have attracted a lot of attention recently as a leading technology to enable integration of renewable energy with the power grid and thereby reduce CO2 emissions caused by the excessive use of fossil fuels. Most work on these systems are primarily based on metal complexes in aqueous electrolytes (limited potential...
Radiative transition probabilities in atoms are normally calculated from
nonrelativistic wave functions and the electric dipole transition operator.
The theory of relativistic corrections to nonrelativistic energies is
well established in terms of the Breit interaction, but the same is not
true for relativistic corrections to transition probabilities.
Our objectives are first, to start from...
Le dioxyde de vanadium (VO2) est un matériau thermochrome de la famille des oxydes de métaux de transition (OMT) qui présente un intérêt scientifique et industriel majeur. En effet, les couches minces de VO2 sont des semi-conducteurs transparents dans la région infrarouge (IR) à température ambiante et passent à un état métallique hautement réfléchissant autour de la température de transition...
Surface wettability describes the behavior of liquids on substrates and their ability to remain in contact with it. Quantification of wettability is often reduced to a measurement of the contact angle that a liquid droplet makes on the surface. Although this practice has become ubiquitous in the literature, a growing number of researchers have voiced concerns that static contact angles alone...
A spray is a dynamic collection of drops dispersed in a gas. Various experimental techniques have been developed to study these parameters. MRI is a new promising technique to study sprays: it does not require optical transparency, unlike most other techniques, and its non-invasive nature does not interfere with sample. Studying sprays with MRI has its own challenges. One of them is related to...
Experimental generation and detection of the entanglement is at the heart of, most if not all, the quantum computational tasks. In general, to determine whether a given state is entangled or not is an open and exigent problem in quantum mechanics. Here we give an experimental implementation of the scheme for tripartite entanglement detection on spin ensemble using NMR. This protocol not only...
We propose three new heuristic derivations of the Planck scale which are based on basic principles or phenomena of relativistic gravity and quantum physics. The Planck scale quantities obtained are within one order of magnitude of the “standard” ones. The phenomena contemplated are the pair creation of causal bubbles so small that they can be treated as particles, the scattering of a matter...
The installation of a Cryogenic Underground Test facility (CUTE) is currently ongoing at SNOLAB. The facility includes a cryogen-free dilution refrigerator which is installed within a drywell at the center of a water tank, and shielded with several layers of low radioactivity lead and ultra-pure copper. CUTE will be used for performance tests, characterization measurements, background tests,...
SNO+ is a multipurpose neutrino physics experiment adapting the Sudbury Neutrino Observatory (SNO) detector located 2 kilometers underground in the SNOLAB facility in Sudbury, Canada. A sensitive technique to assay 210Pb in water was developed by SNO+. For the lower energy measurements of interest to SNO+, radon daughter radioisotopes, especially 210Po and 210Bi supported by 210Pb, are...
The implications of the anarchy principle on CP violation in the lepton sector are investigated. A systematic method is introduced to compute the probability density functions for the CP-violating rephasing invariants of the PMNS matrix from the Haar measure relevant to the anarchy principle. Contrary to the CKM matrix which is hierarchical, it is shown that the Haar measure, and hence the...
My research is part of an effort by the broader subatomic physics community to understand the fundamental characteristics of particles and their interactions. Currently, the Standard Model of particle physics encompasses the knowledge in this field, developed over the last 60 years. As modern technologies and improved experimental techniques develop, measurements become more precise and may...
The IceCube Neutrino Observatory is a cubic-km Cherenkov detector of instrumented ice, designed with the primary goal of detecting very high energy neutrino events beyond the TeV scale from astrophysical sources. Detection of few-GeV atmospheric neutrinos is made possible by the DeepCore infill array. The relatively small amount of recorded event information at these energies introduces...
Integrity of digital security is crucial for maintaining the secrecy of banking data, personal information, company trade secrets, governmental records, and more. A perfectly implemented quantum cryptographic scheme, such as quantum key distribution (QKD), would be impossible to break. Freespace QKD systems commonly rely on polarization encoded single-photons. However, the optics required to...
The migration patterns of fish have been shown to be reflected in the elemental composition of certain bone-like structures (otoliths) within the fish. These follow a radial growth pattern with characteristic ring structures forming annually, giving a method for aging the fish. Elemental analysis of the salts present in the otolith can then be used with locational data to give a mapping of the...
Laser-induced breakdown spectroscopy (LIBS) is a rapid elemental analysis technique that has been used for the detection and identification of bacterial pathogens. There is a high demand for real-time identification of bacteria and the capabilities of LIBS for this are promising. Optimizing the bacterial mounting techniques prior to LIBS analysis in a clinical setting is currently underway....
Nonlinear optical microscopy is a novel technique used for imaging biological structures in tissues. The technique uses nonlinear optical processes such as second and third harmonic generation (SHG and THG, respectively), for producing image contrast. Imaging of biological tissues with SHG and THG signals has several advantages over traditional microscopy methods that rely on single-photon...
Most small single-domain proteins spontaneously organize into essentially unique three-dimensional structures determined by their amino acid sequence. While much has been learned about this folding process from experiment and theory, open questions remain. Here we use an intermediate-level coarse-grained model with 7 atoms per amino acid to explore the interplay of two factors in the folding...
We have previously demonstrated that the mechanical properties of collagen fibrils extracted from tendons are non- uniform along their length at the micrometre scale. We want to investigate how this non- uniformity affects fibril deformation as they are stretched or compressed. We build a platform compatible with an atomic force microscope (AFM) to strain a thin elastic sheet onto which...
The response of an organic photodiode to fields of 300 kVp photon beams was measured while varying the bias applied to the diode. A heterojunction photodiode was fabricated by spin coating a blend of P3HT and PCBM on a glass substrate. The bottom contact was ITO and the top contact aluminum. The photodiode was irradiated with an Xstrahl 300 orthovoltage x-ray unit (Xstrahl Ltd., Surrey, UK)....
Il s’agit de concevoir et de fabriquer un laser à l’état solide aux dimensions réduites pouvant émettre dans un seul mode aux hautes puissances. Nous fabriquons nos miroirs lasers polarisants en déposant sur un miroir laser commercial une couche anisotrope servant de lame quart d'onde par la méthode de déposition par incidence oblique. Le matériau utilisé est le dioxyde de titane. Une...
Okanagan College capitalizes on its long-standing relationship with the Dominion Radio Astrophysical Observatory, bringing students to the facility every semester. These field trips expose students to cutting-edge research, and reinforces the concepts learned in their classes. The realization that world-class research is being performed in the local community engages students tremendously. ...
In a colloid-polymer mixture, non-adsorbing polymer controls the magnitude as well as the range of the interaction between the colloidal particles. In such a system, a network forming gel phase can be observed due to the adsorption of polymer on micrometer-sized colloidal particles. With tunable interactions, such systems could also be used for qualitative studies of phase transition...
Nonspecific interactions of macromolecules in the cell interior lead to a phenomenon known as macromolecular crowding. Interactions between a molecule of interest and the many molecules in the cell interior can modify its characteristics. For example, crowding can cause changes in biomolecules including protein structure, enzyme kinetics and protein-protein interactions. The effect of crowding...
The dynamics of polymer chains in confined environment are relevant in understanding diffusion of macro-molecules in real systems such as biological cells. Macromolecular diffusion in cytoplasm exhibits a sharp reduction in diffusivity with increasing molecular weight; a sieving mechanism has been suggested for the same. We present pulsed field gradient NMR experimental studies of the...
An exciting frontier in quantum information science is the realization of complex many-body systems whose interactions are designed quanta by quanta. Hybrid nanophotonic system with cold atoms has emerged as the paradigmatic platform for engineering long-range spin models from the bottom up with unprecedented complexities. Here, we develop a toolbox for realizing fully programmable complex...
Many biologically motivated problems naturally call for the investigation and comparison of molecular variants, such as determining the mechanisms of specificity in biomolecular interactions or the mechanisms of molecular evolution. We consider a generalized ensemble algorithm for coarse-grained simulations of biomolecules which allows the thermodynamic behavior of two or more sequences to be...
We report on our implementation of online lab sections of PHYS 1100, a one-semester, algebra based course with separate classroom and lab components at Kwantlen Polytechnic University. Since January 2017, we have offered online as well as on-campus lab sections, which students take in conjunction with a class, which itself is available on-campus, online, or partially online. The online lab...
This investigation reports on the 2016 Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the Galactic Center (GC). Two new transients were identified within the Galactic Center, Swift J174540.7-290015 (Transient 15) and Swift J174540.2-290037 (Transient 37). Having observed the GC for 10 years and detected no prior outburst, it can be concluded that the time between outburst...
High resolution and high signal to noise spectra of two HgMn stars, HD53929 and HD63975, were analysed in the frame of Project VeSElkA (Vertical Stratification of Element Abundances) to search for vertical stratification of element abundances in their stellar atmospheres. These stars show signatures of a slow axial rotation and most probably possess hydrodynamically stable stellar atmospheres,...
The results of analysing of the chemical abundance in stellar atmosphere of Sirius are presented as a part of the project VeSElkA that aims to search for evidence of vertical stratification of elements’ abundance in chemically peculiar (CP) stars. Using the high resolution and high signal to noise spectra obtained with the spectropolarimeter NARVAL, we have analysed hundreds of line profiles...
Dispersion relations, often called Kramers-Kronig relations, exploit analyticity to reconstruct the real part of a scattering amplitude from its imaginary (or absorptive part), which is often easier to measure and or to compute. I will present a generalization which reconstructs complete four-point correlators in any conformal field theory, starting with only very limited information about...
X-ray computed tomography (CT) imaging is an integral part of small animal research. It is not only used for diagnosis of disease and monitoring of disease progression, but also for targeting of radiation therapy of cancer in image-guided small animal irradiators. CT imaging in small animals, known as microCT imaging, differs from clinical CT imaging in a number of aspects. Since smaller...
We have studied chimera and chimera-like states in populations of photochemically coupled Belousov-Zhabotinsky (BZ) oscillators. Simple chimeras and chimera states with multiple and traveling phase clusters, phase-slip behavior, and chimera-like states with phase waves are described. Simulations with a realistic model of the discrete BZ system of populations of homogeneous and heterogeneous...
The Large Hadron Collider (LHC) at CERN will be upgraded to a new machine, the High Luminosity LHC, staring up in 2026 with seven times the current luminosity. The ATLAS experiment will then collect 3000 fb-1 of proton collisions at 14 TeV centre-of-mass energy. This large data set will increase the discovery reach and allow higher precision in many measurements. The ATLAS detector needs...
As the world becomes ever more connected, activities such as online banking, shopping and personal data storage will become increasingly popular. The security of these services is essential since private information is involved. Cryptography that rely on computational complexity have not been proven to be secure. Quantum key Distribution (QKD) uses the physical phenomena prevalent in the...
Antihydrogen and hydrogen are simple atomic systems which provide an ideal platform to study differences between antimatter and matter; current theories predict that the universe should be composed of equal quantities of matter and antimatter but cosmological observations place the ratio of the two near 10^-4. The ALPHA (Antihydrogen Laser PHysics Apparatus) collaboration at CERN studies the...
Dynamic Magnetic Resonance Imaging (MRI) acquisitions – e.g. the acquisition of Dynamic Contrast Enhanced MRI for the determination of pharmacokinetic model parameters – are challenging due to their requirement for simultaneous spatial and temporal resolution. This is in particular true for applications of DCE-MRI in areas such as prostate cancer, where the dynamics can be rapid (on the order...
We consider the decay due to tunnelling of metastable Skyrmions that exist in the false vacuum. The possible mass term for the pions explicitly breaks the chiral symmetry. The only phenomenological constraint on the mass term is that the resultant pion mass be small. This allows for the possibility of local minima of the potential, which could give rise to metastable, so-called false vacuum...
Icicles are an ideal test-case for understanding the free-boundary shape of "wet" ice growth. Icicles observed in nature and the laboratory often exhibit ribs or ripples with a wavelength close to 1cm around their circumference. Previous experiments on laboratory-grown icicles have shown that the existence of these ripples depends on the presence of (very small) concentrations of impurities in...
Radon-222 and its daughters are a primary background within SNO+, a large liquid scintillator detector located deep underground at SNOLAB, designed to detect rare neutrino interactions. Therefore it is crucial to determine the remaining trace amounts contributing to the experiment's background signal carefully.
A cryogenic radon trapping system is used to monitor the backgrounds observed in...
The $AdS_4$ spacetime is of much interest to physicists, because of its relevance to the AdS/CFT duality. Very little is known
about how to extract quantum correlations from the AdS vacuum, a procedure called entanglement harvesting.
Using a new and general theorem, we calculate the entanglement harvested by a pair of Unruh-DeWitt detectors coupled to a conformal scalar vacuum of $AdS_4$, in...
The total energy of acoustic emission (AE) events in externally stressed materials diverges when approaching macroscopic failure. Avalanche models explain this accelerated seismic release (ASR) as the approach to a critical point that coincides with ultimate failure. However, not all empirical mechanical processes are critical at failure. As a case study, we show how the soft uniaxial...
SNO+ is a multi-purpose scintillator based neutrino experiment located 2 km underground at SNOLAB, Sudbury, Ontario. SNO+ reuses the Sudbury Neutrino Observatory (SNO) detector, consisting of a 12 m diameter acrylic vessel that will be filled with 780 tonnes of ultra-pure organic liquid scintillator. The primary goal of the experiment is a search for neutrino-less double beta decay with...
abstract: In the first part of the talk, I will discuss a new agent-based model of wealth distribution in a society which incorporates spatial information. The key feature of the model is formation of wealth "hot-spots", region in space where wealth is concentrated. The continuum limit of this model leads an interesting integral equation.
In the second part of the talk, I discuss how a...
The helium atom with its nucleus and two electrons provides a prime example of the quantum mechanical three-body problem. It is often used in text books to provide an example of simple approximation methods for atomic structure calculations. However, variational solutions to the three-body Schrodinger equation that are essentially exact for all practical purposes are possible, and they provide...
Purpose: A novel system of algorithms has been developed that allows for automated planning of conformally collimated radiotherapy plans for the treatment of multiple brain metastases with various prescription doses. This study uses simulated annealing to optimize the collimation to subsets of targets at specified incident radiation angles, along with modulation of dose, to achieve...
Astronomers have observed, through observations of galaxy rotation curves and luminous mass, that our understanding of the dynamics at the scale of galaxies is incomplete; they were the first to challenge the standard model and notice there’s something missing or lacking in our understanding. A possible solution to their observation was adding invisible mass which came to be called dark...
The stability of asymptotically AdS$_{d+1}$ spacetime under arbitrarily small perturbations of a minimally coupled scalar field has been examined via dual lines of inquiry. The first, undertaken by Bizon and Rostworowski in 2011, was concerned with numerical solutions to the fully nonlinear system. This and subsequent work led to the determination that AdS was generically unstable to Gaussian...
After twenty years of working in Radiation Therapy productization, this talk looks at numerous research projects that were attempted translations to commercial and clinical use, with examples of failures, successes and many projects in between. Some common characteristics of successful projects can be identified, and a process for cultivating products is shown. Examples from a career working...
The AdS/CFT correspondence provides an equivalence between a gravity theory in some bulk anti-deSitter spacetime and a conformal field theory (CFT) in one fewer dimensions on the boundary. A superconductor that can be described by a gravity theory through this correspondence is referred to as a 'holographic superconductor'. Gradient flow equations will evolve any given initial field...
NEWS-G (New Experiments With Spheres-Gas) is a rare event search experiment using Spherical Proportional Counters (SPCs). Primarily designed for the direct detection of dark matter, this technology also has appealing features for Coherent Neutrino-Nucleus Scattering (CE$\nu$NS) studies using nuclear power plants as a neutrino source.
For both applications, an important property of the gas to...
In many cases the leaves and petals of plants form curved two-dimensional surfaces. The development of the curvature of those surfaces (ripples, warps, deformations, etc.) can be described by a time dependent Riemannian geometry. Since many biological and chemical systems evolve according to reaction-diffusion equations, the the geometrical description of growth naturally leads to curvature...
We have shown that collagen fibrils have a preferred equilibrium fibril radius. However, the radial distribution of fibrils in tissues is typically polydisperse. Tendon fibrils in particular can exhibit a bimodal distribution of radii within the same tissue. This suggests non-equilibrium effects are important in fibril formation. To investigate these effects, we applied 2d coarsening dynamics...
A strong foundation in upper-level electrodynamics is necessary to learning Atomic, Molecular and Optical (AMO) Physics. But the combination of two features: students having to learn many key concepts, as well as to master the use of mathematical techniques in order to understand the applications, makes this course challenging both for the student and the instructor.
I have re-developed...
After briefly tracing the history of my involvement in weak interactions studies at TRIUMF, I will present the prospect for future major advances and opportunities which are available to the younger generation of Canadian physicists. Throughout this talk, neutrinos will take a special role as a unique but elusive tool which has and will continue to shed critical information of the working of...
This talk presents a study that qualitatively investigated how young women in Ontario experience barriers in their high school physics education. The basis of the research is the long-standing issue of underrepresentation of women in physics in Canada and around the world. The study asked questions aimed at better understanding this issue: What barriers do young women in high school physics...
Over the last several years, there has been a growing interest in ultrafast, intense-laser driven processes in solids. Recent high harmonic generation (HHG) experiments in dielectrics [1] and in semiconductors [2] have revealed ways to transfer attosecond technology from atomic gases to solids. This has given birth to attosecond condensed matter physics. Further, experiments on intense laser...
Image Guided Radiation Therapy (IGRT) technologies aim to improve the accuracy of the delivery of radiation with the hopes of decreasing damage to healthy tissues and sensitive organs. Synergetic MRI-Radiation therapy machines are a developing technology that can provide improved tumour tracking during treatment to help accommodate for patient motion or unaccounted for bodily changes over the...
A decade ago, Yves Couder in Paris discovered that droplets walking on a vibrating fluid bath exhibit several features previously thought to be exclusive to the microscopic, quantum realm. These walking droplets propel themselves by virtue of a resonant interaction with their own wavefield, and so represent the first macroscopic realization of a pilot-wave system of the form proposed for...
Solar neutrinos are an irreducible background for the SNO+ double beta decay experiment. Neutrino interactions in the SNO+ detector produce directional Cherenkov light which, if separated from the dominant scintillation light, would allow for neutrino direction reconstruction and elimination of solar neutrino signals. Other liquid scintillator detectors can also benefit from direction...
The study of isolated systems has been vastly successful in the context of vanishing cosmological constant, Λ=0. However, there is no physically useful notion of asymptotics for the universe we inhabit with Λ>0. The full non-linear framework is still under development, but some interesting results at the linearized level have been obtained. I will focus on the conceptual subtleties that arise...
The Super Cryogenic Dark Matter Search (SuperCDMS) experiment is in the process of incorporating improvements in several aspects, such as experiment location, detectors, and readout electronics. With these improvements, the focus of the new phase of the experiment at SNOLAB will be Weakly Interacting Massive Particles (WIMPs) in the mass range below ~10 GeV/c2. In order to better...
PICO is a bubble chamber experiment for the direct detection of dark matter, and currently holds the world-leading limits in the spin-dependant WIMP (dark matter particle candidate) interaction sector. In order to search for low mass WIMPs (~ GeV scale), scattering on light target nuclei - especially protons - would substantially improve the sensitivity reach of PICO.
In this talk I will...
Many physics professors and departments are concerned about the number of students who complete their degree programs, and the often much larger number of students who leave. This has been an ongoing concern in physics, other sciences, and engineering for several decades, especially for female students and students from underrepresented racial and ethnic groups. What can physics professors,...
Aftershocks are ubiquitous in nature. They are the manifestation of relaxation phenomena observed in various physical systems. In one prominent example, they typically occur after large earthquakes. They also occur in other natural or experimental systems, for example, in solar flares, in fracture experiments on porous materials and acoustic emissions, after stock market crashes, in internet...
Recent experiments with the highly magnetic atoms [dysprosium][1] and [erbium][2] have revealed the formation of a novel form of ultra-dilute stable droplets in dipolar Bose-Einstein condensates (BEC). This surprising result has been explained by the stabilization given by quantum fluctuations.
We will discuss the effects of these beyond-mean-field corrections of a dipolar BEC in [three...
My laboratory is focused on developing a deep understanding of chronic lung disease using novel imaging methods, in patient-based research. The overarching goal of my team’s research is to discover, validate and clinically translate magnetic resonance imaging (MRI) biomarkers while generating the evidence to support the clinical use of lung MRI to change asthma and COPD patient outcomes.
I...
I will discuss recent work constructing Taub-NUT/Bolt solutions in general higher curvature theories of gravity. A broad class of theories known as generalized quasi-topological gravities (that include general relativity as a special case) allow for results non-perturbative in the higher curvature couplings, and we see a number of interesting differences compared to general relativity. General...
In general relativity producing a regular bounce entails violation of Null Energy Condition for a dynamical source in the model. That generically indicates existence of ghosts or other instabilities. However, in cuscuton modification of gravity, the correspondence between a background bounce and violation of Null Energy Condition for dynamical sources is broken. Cuscuton is an Infra Red...
In recent scattering experiments [1,2], high-intensity, short-duration, electromagnetic pulses were scattered off dielectric liquids such as water and carbon tetrachloride. The observed pattern of the scattered light led the authors to propose a theory, based on single-particle, classical electromagnetic scattering, that there was magnetic dipole radiation generated. They called this...
The PICO40L bubble chamber is a threshold detector filled with C$_3$F$_8$ located at SNOLAB and design to perform direct dark matter searches. During the construction of this detector, a very careful screening of the materials allowed the selection of materials containing low amount of neutron emitting isotopes. By using GEANT4, GDML and McCAD, a simulation of the expected neutron background...
The fifth edition of the Canadian Conference for Undergraduate Women in Physics (CUWiP) series was held at Queen's University on 12-14 January 2018. A conference report for this 2018 edition will be presented. The second part of this talk will report on the evolution of a partnership between CAP and the US American Physical Society (APS) as part of the organization of this conference series.
Neuronal systems have become emblematic of nonequilibrium biological systems with complex behaviour. Owing to observations of apparently scale-free cascades of causal activity (avalanches) in neural cultures, it has become a popular hypothesis that neural systems operate close to a nonequilibrium phase transition. That neural systems should operate at a critical point is supported by theory,...
One of the recently developed approaches capable of describing both bound and scattering states in light nuclei simultaneously is the No-Core Shell Model with Continuum (NCSMC). This technique represents a state-of-the-art $ab \; initio$ approach and combines the No-Core Shell Model (NCSM) description of short-range correlations with the clustering and scattering properties of the Resonating...
Cryogenics is a mature yet growing industry and cryogenic liquids are in increasing demand as global industrialisation continues to expand, especially with the increase in liquid natural gas projects, which is providing mutually beneficial advances in cryogenic equipment. In this paper we discuss the use of cryogenic liquids as an energy storage vector, which has implications on the energy...
The traditional battery configuration incorporates a negative electrode, or anode, which acts as a host insertion material for alkali metal ions. This host anode is necessary due to the unstable metal plating chemistry, especially for lithium, in known electrolyte media. In this talk, I will discuss our recent efforts to develop the anode-free battery, or a full-cell battery configuration...
Despite almost 90 years of study the physiological role of vitamin E is still muddied by controversy. Research, both fundamental and clinical, has generated conflicting and contradictory results throughout literature.
Deficiency in α-tocopherol (aToc), the physiological relevant form of vitamin E, has been show to lead to a multitude of conditions including infertility and neuromuscular...
Non-perturbative techniques are needed to study strongly coupled systems. One powerful approach is the n-particle irreducible effective action. The technique provides a systematic expansion for which the truncation occurs at the level of the action. However, renormalisation using a standard counterterm approach is not well understood. At the 2PI level one must introduce multiple counterterms,...
Neutrino oscillation measurement entered a precision era. In summer 2017, T2K
disfavoured CP conserving phase of δcp=0,π at 2σ level. CP asymmetry in neutrino
and anti-neutrino νμ->νe appearances can be as large as 20% depending on the CP
phase δcp, which is within the reach of new projects, HyperK and DUNE. HyperK
aims at statistical error of ~3% for the asymmetry. It is essential to...
The Canadian Light Source is the country’s national synchrotron research facility. At its core is the largest particle accelerator in Canada – a 174m circumference storage ring, housed in a building the size of a football stadium. As is usual for facilities of this type, we have hosted thousands of researchers from all over the country and around the world. What is somewhat less usual is that...
The past few years have seen the rapid maturation of quantum information processors, particularly in the category of superconducting microwave circuits. With claims from leading companies that they will commercialize quantum processors in the next five years, we must wonder what quantum technologies should be developed in tandem to fully utilize these processors. For example, we are all...
There are a number of opportunities to increase Li-ion battery energy density. At the negative electrode, Si alloys can store much more lithium than graphite, which is currently in use. As a result, utilizing Si alloys in Li-ion cells has been shown to increase energy density by about 20%. However, there are many challenges for the utilization of Si alloys in practical Li-ion batteries. ...
RfaH is a compact two-domain multi-functional protein from the bacteria $Escherichia\ coli\ (E. coli)$. Its C-terminal domain (CTD) has been shown experimentally to be able to undergo a complete conformational change from an $\alpha$-helix bundle to a $\beta$-barrel structure. The $\alpha$-helix bundle to $\beta$-barrel fold switch accounts for the observed dual role of RfaH, whereby it...
The CHY technique for computing scattering amplitudes has been used in a large variety of theories ranging from Einstein gravity to the Chiral Lagrangian. Many of these theories have in common that they are effective field theories (EFTs) of spontaneously broken symmetries. In this talk I will review recent results relating these effective field theories including the recent formula for the...
Friction reducing, two-dimensional dry lubricants, such as graphene, boron nitride, and molybdenum disulphide, have been shown to have a number of interesting frictional characteristics, such as a dependence on the number of layers, an exceptional dependence on the surface adhesion properties of the underlying substrate, and environmental stability. We explored the frictional properties of...
High-precision measurements of the $ft$ values for superallowed Fermi beta decays between 0$^+$ isobaric analogue states have provided invaluable probes of the Standard Model (SM) description of the electroweak interaction. These measurements confirm the CVC hypothesis to 1.2 parts in 10$^4$, set the tightest experimental limits on the existence of scalar currents in the electroweak...
Thanks to recycling and diversion initiatives over the last decade, the number of tires finding their way to landfills has been greatly reduced. The majority of rubber produced from recycled tires is in the form of crumb, which is most often created by mechanical grinding resulting in particle diameters between 1 and 5 millimeters. Because of the energy required to break and reform the...
The ATLAS detector has been in an intense period of data-taking since the start of Run 2 in 2015. With 86 fb-1 collected so far, the prospects for discovering dark matter at the LHC have never been higher. WIMP dark matter may be produced in proton-proton collisions, yielding an excess of collision events with a large amount of invisible missing transverse momentum (ETmiss); such a process...
The sky on a clear night is one of the most fascinating natural sights, providing multiple (and free!) promotion opportunities for physics. The talk will describe the recent astronomy-related outreach activities at the Grenfell Campus if the Memorial University of Newfoundland, leading to more than doubling enrollments in our physics courses, as well as several methods ensuring that the...
Thin polymeric films have numerous technological applications and their stability has garnered intense interest. The stability and flow of a thin, viscous film is sensitive to the boundary conditions as the film thickness approaches the nanoscale. Here we probe a liquid-liquid boundary condition: a stepped polymer film is placed above a different, immiscible polymer film. The ensemble is...
Carleton University has a long history of involvement in detector design, testing, and construction for experiments at CERN including the original ATLAS detector at the LHC (Forward Calorimeter) and the New Small Wheel to be installed during LS1 (sTGC). In the past four years, we have developed the necessary capabilities and infrastructure to participate in the inner tracker upgrade needed for...
Some nuclei far from the valley of stability have been found to have ground state properties that are different than those naively expected from the nuclear shell model. The term `island of inversion' is used to refer to regions of the nuclear landscape in which deformed intruder configurations dominate nuclear ground states over the normal spherical shell model ones. The nuclear structure of...
A measurement is presented of the triple-differential cross section for the Drell--Yan process $Z/{{\gamma }^{*}}\to {{\ell }^{+}}{{\ell }^{-}}$, where ${{l}^{+}}{{l}^{-}}$ is an electron or a muon. The analysis uses$pp\ $collision data at a centre-of-mass energy of $\sqrt{s}=8$TeV collected by the ATLAS detector at the LHC in 2012. The measurement is performed for invariant masses of the...
Extensive effort in the hunt for particle dark matter continues to explore WIMP-nucleon cross sections for the typical weak-scale masses below $10^5$GeV$/c^2$. Extension of the canonical WIMP exclusion limit to superheavy masses becomes an inaccurate description when the cross section rises high enough for relic particles to scatter multiple times within the depth of a detector. These...
Using the well-known Autler-Townes effect, we have implemented a novel quantum memory in our laboratory in a medium of laser-cooled rubidium atoms. This new method relies on the absorption of the signal over a wide spectral region, making it inherently broadband and well-suited to quantum memory applications. This Autler-Townes splitting (ATS) protocol facilitates dynamical control of coherent...
The residual nucleon-nucleon interaction plays a crucial role in nuclear structure physics. In spherical even-even nuclei the quadrupole interaction leads to characteristic low-lying 2+ states of proton-neutron mixed symmetry character, decaying via M1 transitions to the proton-neutron symmetric states. We have calculated the associated M1 transition strengths in the $^{52}$Ti nucleus within...
An in-situ technique for monitoring the pressure evolution of volumetrically constrained Li-ion pouch cells has previously been introduced by Louli et al.[1] When constrained, changes in cell volume cause a pressure response that is measured. A reversible pressure change is observed due to the reversible electrode volume expansion and contraction during charge and discharge of the cell.[1] ...
Searching for information online has been an integral part of our lives for quite some time now. But many instructors - and students - will consider googling information to solve an assignment as cheating, perhaps thinking only of assignments that aim at lower levels of learning. How can we integrate online search in tutorials in a meaningful way, to make problem solving more authentic and...
Precision calculations in de Sitter space (such as of inflationary predictions for primordial fluctuations) are often plagued by infrared problems and issues of secular time dependence. Similar issues about the breakdown of perturbation theory seem also to arise for information loss in black holes. This talk briefly summarizes how related problems can arise in other areas of physics, and how...
In most polyelectrolyte translocation studies, regardless of the shape of the pore and the strength of the driving force, the polymer chain has to go through three basic steps: (i) diffusion; (ii) capture; (iii) threading. The capture process remains rather ill-understood because it cannot easily be visualized or inferred from the blockage current measured across the nanopore. To estimate the...
There is a continual push to improve the energy density of lithium-ion batteries, but this is becoming increasingly difficult as it is believed that many of the best electrode materials have been found and optimized. In order to achieve higher energy densities to meet future storage demands it may be necessary to move “beyond lithium-ion”.
Recent research efforts have focused on reviving the...
Hadronic interaction uncertainty is a shared systematic uncertainty between many neutrino experiments. The reduction of this uncertainty would mean a furthering of the physics goals for these experiments. Hadronic interactions from the T2K and NuMI beamline can be separated into primary and secondary interactions. Primary hadronic interactions occur when high energy protons interact with a...
We examine a way to deal with alternative student conceptions about force and motion in a university introductory physics course. The course combines Reflective Writing, an activity that engages students in textual material metacognitively, and Labatorials, an in-class active learning intervention. The analysis is based on both pre- and post- interview statements, to give a picture of the...
Surface Enhanced Raman Spectroscopy (SERS) is a powerful tool for detecting chemicals, including rhodamine 6G (R6G), at the molecular level. The authors have developed a plasmonic structure by depositing gold nanorods (GNRs, aspect ratio: 6.4) on a tapered optical fiber via optical tweezing. A 1064 nm laser was coupled to the un-tapered end of the tapered fiber for tweezing. The tweezing...
As a facility for users from around the world, TRIUMF takes very seriously its commitment to providing researchers' the best possible experience at the lab. Recently a new 'Visitor Liaison' group has been established that enhances user support and engagement, and a new User Newsletter is being launched to provide users with up to date information about laboratory experimental services. This...
Rapid development of nanofabrication has stimulated the growth of the field of nonlinear photonics. Nonlinear photonic devices are finding their applications in more and more areas, including (but not limited to) classical and quantum communications. The material platforms used for nonlinear photonics on-a-chip range from transparent dielectrics with a relatively weak nonlinearity to...
The development of charge-storage materials for use in redox flow batteries (RFBs) requires possession of a diverse property set that will lead to high capacities, voltages, and lifetimes for large-scale stationary storage application. High capacities require high solubilities in all states of charge. High voltages stem from large differences in redox potentials. Long lifetimes require...
After 22 years of teaching first-year university introductory physics, this past year marks the foreseeable end to this aspect of my academic career with my move to become a Graduate Studies Dean and AVP Research. This milestone provides opportunity to reflect upon this journey, and hope to provide some useful insight to others of you who remain intimately embroiled in the challenge of being...
Higgs portal dark matter models assume a coupling between dark matter and baryonic matter through Higgs exchange. These models are constrained in the low mass sector through limits on the branching ratio into invisible Higgs decays. Higgs portal models are also increasingly tested in the high-mass sector through direct search experiments. I review the current status of the Higgs portal models...
A substantial amount of the evidence-based pedagogies developed for lower level physics classrooms can be adapted to senior undergraduate and even graduate level classes. In this talk I will describe the use of in-class worksheets to foster deeper understanding and content proficiency in senior level electromagnetism, senior level special relativity, and graduate level classical mechanics...
In this talk I will discuss a recently proposed model of "Dark Baryon Superfluid" dark matter. This scenario begins with a unified model of dark-genesis and baryogenesis, involving strongly interacting dark quarks, and utilizing the gravitational anomaly of chiral gauge theories. In these models, both the visible and dark baryon asymmetries are generated by the gravitational anomaly induced by...
Light is our best medium for sending information over long distances—it moves at nature’s speed limit, and doesn’t degrade for hundreds of kilometers. As quantum technologies become more prevalent, we will strive to transmit quantum information, and for this, we will require high quality sources of quantum light.
Sources of quantum light based on nonlinear optical processes, which mediate...
Li-ion batteries that can charge rapidly without sacrificing lifetime are crucial for the further development of electric vehicles (EVs) and for better customer acceptance. Measuring transport properties such as ionic conductivity and viscosity are simple and effective techniques for screening electrolyte suitability for fast charge applications. The use of low-viscosity esters as co-solvents...
Redox flow batteries, which utilize solutions of active materials (anolyte and catholyte) rather than the solid state electrodes found in conventional batteries, are highly promising for stationary energy storage applications. Whereas most redox flow cells are based on metallic active species in aqueous media, we have been working on developing flow batteries based on solutions of redox active...
When assessing student performance, some educators choose to discard the worst tests written by the student. The mean of the remaining tests is taken as opposed to the mean of all tests written. Naturally, this process will result in some expected grade inflation. In our paper we provide a model for the expected grade inflation in the case when the student’s test-writing ability changes over...
We theoretically investigate and experimentally demonstrate polarization modulation of a beam of light interacting with a nanometer-thin layer of vanadium dioxide (VO2), a phase change material. As the material undergoes a phase transition from insulator to metal, large variations in refractive indices impart unequal phase shifts on s- and p-components of the electric field of light, thereby...
In conjunction with a new interdisciplinary, experiential science course for non-science majors, we have developed the Augustana Interdisciplinary Scientific Literacy Evaluation (AISLE) to measure gains in scientific skills and attitudes. This presentation will outline the context of AISLE, its development criteria, calibration data, and upcoming analyses.
Redox flow batteries are a promising solution for large-scale energy storage. Many flow batteries have been successfully commercialized; however, these systems typically involve the use of expensive metallic redox couples such as vanadium, iron-vanadium and iron-chromium, which exceed the US Department of Energy’s cost target of $100 kWh-1.
One approach to reducing systems costs involves...
We use QCD Laplace sum-rule to explore meson-hybrid mixing in vector heavy quarkonium. Our cross-correlator calculation supplements perturbation theory with non-perturbative corrections proportional to the four-dimensional and six-dimensional gluon condensates and the six-dimensional quark condensate. After forming the Laplace sum-rule we use experimentally determined hadronic masses to build...
Over the last decade, machine learning (ML) methods have become increasingly important in medical imaging. In addition to more traditional classification tasks, ML is now being used in many other applications including object search and segmentation, image registration and even image reconstruction. Recent advances in deep learning have accelerated this trend and it is now possible to achieve...
This is a test abstract so can learn Indico programming.
An exciting frontier in quantum information science is the creation and manipulation of quantum systems that are built and controlled quanta-by-quanta. In this context, there is active research worldwide to achieve lithographic quantum optical circuits, for which atoms are trapped in nanoscopic dielectric structures and wired by photons propagating through complex circuit elements. I will...
Two-dimensional (2D) van der Waals (vdW) heterostructures have attracted great attention in the past five years. By stacking different 2D materials to bond via the vdW force, these artificial heterostructures provide new material phase space for exploration. In this work we focus on one aspect of the 2D vdW material: the Moiré pattern. In visual arts, Moiré pattern is an optical perception of...
Why are there so few women in some disciplines of sciences and engineering (SG)? What can we do to change the numbers? How can we improve the inclusion and well-being of female students in these disciplines? Why should we care? In this presentation, we will explore these questions.
Through her life, from a young child to an adult on the labor market, a woman encounters some barriers that may...
The overarching goal of my research is to improve methods for non-invasively mapping the spatial and temporal patterns of electrophysiological activity that underlies human brain function and dysfunction. My team at the Biosignal Lab studies brain electrophysiology with magneto- and electro-encephalography (M/EEG). These technologies provide spatially and temporally rich data about the...
The planned luminosity increase of the LHC will allow the precise measurement of Higgs boson properties and extend the search for new physics phenomena beyond the standard model. To maintain excellent detection and background rejection capability in the forward region of the ATLAS detector, part of the muon detection system is scheduled to be upgraded during the LHC long shutdown period of...
Neutrons converted to low energies of several hundreds of neV are referred to as ultra-cold neutrons (UCN). Their unique storage properties and resulting long observation times make them an ideal tool to study fundamental properties. Results obtained from measurements of the neutron lifetime and experiments searching for a neutron electric dipole moment (EDM) have profound consequences for the...
Dalhousie University was established in 1818 through an act of the Nova Scotia Legislature. Proper function of the College, however, did not commence until 1838 and it ceased again in 1848 when the College reverted to a high school. A reorganization of Dalhousie took place in 1863 when an Act of the Legislature incorporated Dalhousie as a University. In 1877 the Dalhousie board appointed J.J....
Millimeter-thick charge-coupled devices (CCDs) are outstanding particle detectors. Although initially developed for near-infrared astronomy, the low pixel noise also makes them the most sensitive detectors to signals from ionizing radiation. By virtue of their very low energy threshold, and their unique capabilities for background characterization based on their high spatial resolution, CCDs...
Global-scale distances for Quantum Key Distribution (QKD) can be achieved by utilizing an orbiting satellite acting as an intermediate node between two or more ground stations as has been recently demonstrated with the Chinese satellite Micius and there are further missions to follow from various countries including Canada (QEYSSat). Each of these missions have different methods to implement...
The exchange-hole dipole moment (XDM) method is a density-functional model of London dispersion based upon second-order perturbation theory. The XDM dispersion coefficients are non-empirical and depend directly on the electron density and related properties. XDM offers simultaneous high accuracy for a diverse range of systems due to the variation of the calculated atomic dispersion...
Recently methods to measure axon diameter distributions using magnetic resonance imaging (MRI) diffusion spectroscopy have been developed. Most early methods used single diffusion encoding sequences such as pulsed gradient spin echo and are thus sensitive to axons of diameters larger than 5 μm. We previously simulated oscillating gradient (OG) spin echo sequences to study smaller axons which...
The Cryogenic Underground Test (CUTE) facility is under construction at SNOLAB, aiming to test the performance of the cryogenic detectors of the Super Cryogenic Dark Matter Search (SuperCDMS) experiment.
The ‘Ultra Quiet Technique’ (UQT®) is applied to reduce the vibration transmission from an advanced dry dilution refrigerator (CryoConcept, France) that allows operating the cryogenic...
There are more women entering STEM disciplines than ever before. However, despite huge improvement in pedagogy over the last twenty years, both physics and engineering continue to have persistent and entrenched gender divides; only about 20% of Canadian undergraduate and graduate students in both physics and engineering are women. The reasons why relatively few women enter physics and...
Seventy years ago, the McGill University 100-MeV synchro-cyclotron was under construction. During its almost 40 years of operations, many discoveries were made and a large number of doctoral students were educated. The long-term influence of the cyclotron lab on the landscape of Canadian subatomic physics was considerable and is arguably greater than that of Rutherford, an earlier engine of...
The TRIUMF Ultracold Advanced Neutron (TUCAN) collaboration uses a neutron source based on superfluid helium to produce ultracold neutrons. Superfluids are usually thought of as having infinite thermal conductivity. But at the operating temperature and heat flux for our source, the transport of heat in the superfluid is expected to be limited by quantum vortices. In the two-fluid model, the...
The search for a permanent electric dipole moment (EDM) of the free neutron is a high precision measurement. Its outcome has high impact on subatomic physics since it’s linked to violation of CP symmetry, and to the Baryon Asymmetry of the Universe.
The TUCAN collaboration (TRIUMF UltraCold Advanced Neutron source) aims to build a world leading facility for the production of Ultracold...
Since the nineteenth century, biochemists and physiologists from all around the world tried to elucitade the pathways of intermediary metabolism of living organisms as for instance, in higher plants:
« One cannot emphasize too strongly that in the plant the synthesis of all organic substances must revert to the initial mechanism involved in the synthesis of carbohydrates, so that the...
Lithium-ion batteries used in smart phones last several years. However, they must last at least a decade in electric vehicles and many decades in electrical energy storage systems. In this lecture I will explain why Li-ion batteries eventually fail and introduce simple methods we have invented to rank lithium-ion cell lifetime in experiments that only take a few weeks. These simple methods...
Li-ion batteries that can charge rapidly without sacrificing lifetime are crucial for the further development of electric vehicles (EVs) and for better customer acceptance. Measuring transport properties such as ionic conductivity and viscosity are simple and effective techniques for screening electrolyte suitability for fast charge applications. The use of low-viscosity esters as co-solvents...
Today roughly 60% of the energy humans produce is lost as waste heat. Thermoelectrics (TE) can convert this heat source into useful electrical power, and thus have the potential to impact our energy future. The key challenge is to increase the TE conversion efficiency, which depends on the TE material properties. The past decade has seen remarkable progress in TE materials, but that have...
We discuss applications of a versatile, auto-locking laser system consisting of an external cavity diode laser and waveguide amplifier. The diode laser, which is capable of being vacuum-sealed, can be frequency stabilized with reference to atomic, molecular, and solid state spectra using a digital controller that relies either on a pattern-matching algorithm or on first or third derivative...
Intrinsically disordered proteins (IDPs) are proteins lacking hydrophobic but are enriched in polar, charged, and aromatic amino acids. IDPs do not fold into a unique structure in isolation and often remain disordered in performing biological function. Recently, some IDPs have been discovered to undergo reversible liquid-liquid phase separation (LLPS) in aqueous solution, forming membraneless...
Rechargeable lithium-ion batteries play an important role in the transition away from non-renewable sources of energy. Due to the long lifetime demanded of sustainable technologies, high accuracy, high precision testing is needed to enable reliable predictions of the lifetime of batteries within a short period of time. Novonix is a company spun out of Dr. Jeff Dahn’s lab at Dalhousie...
We examine the electrophoresis of charged spherical particles in microfluidic devices made of alternating wells and narrow channels, including a system previously used to separate long DNA molecules. Our computer simulations predict that such systems can be used to separate spherical particles of different sizes that share the same free-solution mobility. Interestingly, the electrophoretic...
20 min presentation + 5 min questions
Diffusion plays a critical role in many biological processes, but also in a wide range of experimental devices such as gel electrophoresis and sieving. The well-known Ogston model predicts that the diffusivity of a migrating particle through a random network of fibers (e.g., a gel matrix) is proportional to the fractional volume available to the migrating particle in the given medium. As such,...
Intermediate band (IB) materials are a novel class of materials that, like semiconductors, have a band gap but also have an extra set of allowed electronic levels entirely contained within the semiconductor band gap, allowing sub-gap photon absorption. Solar cells made from such materials have the potential to radically improve photovoltaic efficiencies, similar to triple-junction cells. IB...
Nitrous oxide is of interest for atmospheric composition studies. Spectroscopic remote sensing studies rely on the availability of accurate sets of line parameters for molecular atmospheric constituents. In this study we have extended the set of line parameters for nitrous oxide obtained using the speed-dependent Voigt line profile with a weak line mixing component. We have used five room...
Single photon absorption and decay is the process where an atom emits or absorbs a single photon whose energy is equal to the energy difference between atomic energy levels. In two photon processes, an atom emits or absorbs two photons whose energies sum to the energy difference between atomic energy levels. The study of two photon processes has multiple applications in several fields of...
The IceCube Neutrino Observatory, located deep underground at the geographic South Pole, is the largest neutrino detector in the world. The experiment uses over 5,000 photo-sensors to monitor a volume of one cubic kilometer of pristine ice, recording the Cherenkov light emitted by neutrino interaction products. By studying these signals, IceCube has demonstrated the existence of astrophysical...
Cavity spintronics (also known as spin cavitronics) is a newly developing, interdisciplinary field that brings together microwave and optical communities with researchers in spintronics and magnetism. The field started around 2014 when it was found that ferromagnets in cavities hybridize with both microwaves and light by light-matter interaction [1]. Since then, the emergence of cavity...
Over the years, Second Harmonic Generation (SHG) microscopy has emerged as an effective tool in biology. Like in two-photon excited fluorescence (2P), this type of laser scanning microscopy is characterized by an intrinsic 3D sub-micron resolution that is robust upon light scattering and which allows for higher image depth when compared to confocal microscopy. SHG is a nonlinear optical...
In the presence of strong electronic repulsion, a half-filled-band material can be insulating, instead of metallic as one would have expected from standard solid-state physics. Such a material is a Mott insulator. The first-order transition from metal to Mott insulator as a function of interaction strength in two-dimensions is well described by cluster generalizations of dynamical mean-field...
The use of quantum mechanical signals in communication opens up the opportunity to build new communication systems that accomplishes tasks that communication with classical signals structures cannot achieve. Prominent examples are Quantum Key Distribution Protocols, which allows the generation of secret keys without computational assumptions of adversaries. Over the past decade, protocols have...
Designing and assembling highly complex quantum systems from their individual constituents provide an important milestone in quantum information science and quantum many-body physics. Cavity QED provides a means for efficient light-matter quantum interfaces, where the internal states of individual atoms can encode the information of the material system, whereas the cavity vacuum can act as the...
In 2015, the US nuclear science advisory committee (NSAC) in its long range planning exercise strongly recommended the construction of a high-energy high-luminosity electron ion collider (EIC). It was recognized that the EIC, with its polarized electron and light ion beams, and unpolarized heavy ion beams, would be a unique facility to help us study the role of gluons in QCD and answer some of...
The PICO collaboration aims at direct detection of dark matter using superheated liquid detectors, or bubble chambers. Several generations of PICO detector have operated at SNOLAB, setting world-leading limits on the WIMP-proton spin-dependent coupling. PICO-40L is the next iteration of the PICO detector, and has been substantially redesigned since its predecessor, PICO-60. The main...
We successfully demonstrate Surface Enhanced-Stimulated Raman Scattering (SE-SRS) using Oxonica (now Cabot securities) nanoparticles for particle concentrations as low as 10 picomolar using peak power densities that are three-to-four orders of magnitude smaller than that required for conventional SRS. These reduced incident powers are possible because the laser field is significantly enhanced...
We numerically study plasmonic and photonic mode properties of arrays of strip-like metallic nanoantenna on Vanadium dioxide (VO2) substrate. VO2 features a semiconductor to metal phase change characteristic below and above a critical temperature that leads to an abrupt change in the particle’s optical properties. These VO2 optical variations lead to alter this martial from a relatively...
The Super Cryogenic Dark Matter Search (SuperCDMS) experiment has used data taken at the Soudan Underground Mine between 2011-2015 to search for nuclear recoils near 1 keV. Nuclear recoils at this energy constrain the possibility of low-mass Weakly Interacting Massive Particles (WIMPs). The Soudan SuperCDMS detectors produced a world-leading limit on the cross section of spin-independent...
Osteocytes, the most abundant cells present in bone, regulate bone mass by chemical signaling through the lacunar-canalicular network (LCN). Bone diseases such as Hypophosphatemic Rickets cause painful bone twisting in children, and progress on understanding this disease is slow. The structural and mechanical properties of the LCN are difficult to understand since the LCN is embedded in bone,...
Quantum spin liquids (QSL) are exotic phases of matter that host fractionalized excitations. It is difficult for local probes to characterize QSL, whereas quantum entanglement can serve as a powerful diagnostic tool due to its non-locality. The kagome antiferromagnetic Heisenberg model is one of the most studied and experimentally relevant models for QSL, but its solution remains under debate....
This presentation is a continuation of spectroscopic results presented last year. We have completed our investigation of 27 spectra of carbon monoxide and of carbon monoxide mixed with air recorded over a range of temperatures at the former Fourier transform spectrometer located at Kitt Peak, Arizona. The spectra were analyzed using the speed-dependent Voigt and speed dependent Rautian...
The study of the beta-decay properties in the very neutron-rich region is required for a better understanding of the elemental abundances of heavy elements in the Universe. An important decay mechanism in this region includes beta-delayed neutron emissions when the Q-beta value is larger than the neutron separation energy. Thus, by improving the knowledge about these decays we can better...
A wide variety of experiments to directly search for dark matter/atom scattering are being pursued. To search for low-mass dark matter, detectors are exploiting recent advances in calorimeter technology and are pushing the physical limits of ionization calorimetry with single photon or electron detection. SuperCDMS SNOLAB and other upcoming experiments will be using these technologies to...
In this contribution, I will discuss the measurements using synchrotron radiation that led to the discovery of a remarkably well preserved skin layer of a hadrosaur from the Grand Prairie region. This is first ever observation of preserved epidermal skin layers in a large dinosaur. I will also present a direct comparison between these structures and those from an extant avian specimen, giving...
With a 6 km water equivalent overburden in the Canadian Shield, SNO+
plans to make a competitive measurement of neutrinoless double beta
decay in Tellurium doped liquid organic scintillator. Additionally,
the detector has the capacity to make measurements of reactor,
supernova, solar and geoneutrinos. Since December 2016, the detector
is taking data as a water Cherenkov detector to set limits...
How can you learn about the early moments of the universe? How can you discover evidence for new sub-atomic particles? We usually think of ever-more exotic telescopes, or of ever-larger particle accelerators. I will talk about the third leg of the stool: precision measurement. We will see that the humble two-atom molecule should be thought of as an ultrahigh-electric-field laboratory.
In the context of black hole chemistry, We study the thermodynamics of asymptotically de Sitter Black holes with conformal scalar hair in Einstein gravity. The hair parameter allows us to reach thermodynamic equilibrium between the event horizon and the cosmological horizon. We find that these hairy black holes undergo a new phase transition that resembles the phase transtions of denatured proteins.
