Choose timezone
Your profile timezone:
Powered by Indico
v3.3.5
Help us make Indico better by taking this survey! Aidez-nous à améliorer Indico en répondant à ce sondage !
Results of the 2016 CAP Best Student Paper Competition (Divisions and CAP overall, oral and poster)
Congratulations! If you haven't received your prize confirmation letter at the Recognition Gala, June 16, please contact Danielle at capmgr@uottawa.ca.
Click on the "Timetable" on the left to view the Congress program.
The 2016 CAP Congress is being hosted by the University of Ottawa (Ottawa, ON), June 13-17, 2016. This Congress is an opportunity to showcase and celebrate the achievements of physicists in Canada and abroad. Mark your calendars and bookmark the main Congress web site (http://www.cap.ca/en/congress/2016 ) for easy access to updates and program information.
Félicitations! Si vous n'avez pas reçu votre lettre de confirmation de prix au Gala de reconnaissance du 16 juin, veuillez communiquer avec Danielle au capmgr@uottawa.ca
Cliquez sur "Timetable" à gauche pour voir la programmation du Congrès.
Le Congrès 2016 de l'ACP se tiendra à l'Université d'Ottawa (Ottawa, ON) du 13 au 17 juin 2016 (des réunions de l'IPP, l'IPCN et du conseil de l'ACP auront lieu le dimanche 12 juin). Au cours de cet événement nous pourrons profiter des présentations et des réalisations de physiciens et physiciennes du Canada et d'ailleurs, et les célébrer. Inscrivez la date du congrès à votre agenda et créez un signet de l'adresse du site web du congrès http://www.cap.ca/fr/congres/2016) pour accéder facilement aux mises à jour et au contenu de la programmation.
30 min presentation + 5 min questions
20 min presentation + 5 min questions
30 min presentation + 5 min questions
20 min presentation + 5 min questions
30 min presentation + 15 min questions
Monte Carlo simulations have been ubiquitous in efforts to simulate and characterize properties of matter and materials since the advent of computers themselves. In the last decade, condensed matter physicists have turned simulation technology to the study of a new set of phenomena, loosely termed as "emergent", with correlations not manifested in traditional correlation functions. Motivated by this, a new set of tools was recently developed that allows one to probe emergent phenomena in Monte Carlo simulations through their entanglement entropy - a concept borrowed from quantum information theory. Remarkably, since certain scaling terms in the entanglement entropy are universal, this provides a powerful general method to characterize phases and phase transitions in a wide variety of physical theories. Thus, Monte Carlo simulations are beginning to play a central role for physicists who increasingly rely on information quantities to study correlations not only in condensed matter systems and quantum devices, but even in quantum fields and theories of quantum gravity.
NEMA (National Electrical Manufacturers Association) Standard Measurements are used for evaluating the performance of the positron emission tomography scanners used in animal imaging. There are various measurements, including spatial resolution, scatter fraction, sensitivity, and image quality.
In this study the effects of varying the testing procedures of the NEMA NU4-2008 standard for measuring sensitivity and image quality for a small animal PET scanner were examined. In the current NEMA NU4 2008 standard, the sensitivity is measured by stepping a Na-22 point source through the field of view of the scanner along the central Z axis. In some scanners it is not possible to automate the collection of this data, making it very tedious, if not impossible, to acquire the necessary data. As an alternative method, we explore using a long uniform line source extended beyond the field of view in the axial direction and validated this method by comparing our results with those obtained from the standard method. Two line sources were imaged, the first a 70-cm long plastic tube filled with 6 MBq of F-18 (NEMA line source for clinical scanners) and the second a standard 20-cm long Ge-68 sealed line source (0.90 MBq). Point source data were sorted and analysed following the NEMA NU4-2008 method to calculate sensitivity profiles to be plotted as a function of axial distance relative to the center of the field of view. Line source data were analyzed in a manner analogous to the NEMA NU2-2001 method for calculating sensitivity for clinical PET systems. The results from the F-18 and Ge-68 are in good agreement with those from a Na-22 point source (0.93 MBq) using the NEMA standard methods. The difference in absolute sensitivity between Na-22 and the line sources are 0.90% for F-18 and 1.7% for Ge-68 line source. These results represent the equivalence of the sensitivity measurements using a line source or a point source.
Though an extensive amount of literature documents the improved learning gains made by interactive teaching compared to traditional lecture delivery, results vary widely between courses[1]. Part of the problem is that different instructors aim for active learning through widely varying (and sometimes conflicting) approaches[2]. In addition, even the most well-verified and effective teaching approach will fail without student buy in. I propose a simple framework that can help you identify effective active learning instructional strategies and how to implement them successfully. Results (both positive and less than positive) from a large first-year physics course will be discussed.
[1] one example among 100s: Freeman et al., Proceedings of the National Academy of Sciences 111, 8410 (2014). For a contrasting view, Andrews et al., CBE-Life Sciences Education 10, 394-405 (2011)
[2] Turpen and Finkelstein, Physical Review Special Topics-Physics Education Research 5, 020101 (2009)
This is a moderated panel discussion and Q&A (with NSERC reps, physicists and industry partners) on NSERC funding opportunities available to support researcher-industry partnerships. Learn how to get started, the challenges/rewards and tips for a successful partnership.
Panelists will be named as they are confirmed.
Over the past few decades, systematic research has shown that many physics students express essentially the same (incorrect) ideas both before and after instruction. It is frequently assumed that these ideas can be identified by research and then addressed through “interactive” teaching approaches such as hands-on activities and small-group collaborative work. In many classrooms, incorrect ideas are elicited, their inadequacy is exposed, and students are guided in reconciling their prior knowledge with the formal concepts of the discipline. Variations of this strategy have proven fruitful in science instruction at all levels from elementary through graduate school. However, this summary greatly over-simplifies the use of students’ ideas as the basis for effective instructional strategies. Examining what students have actually learned after using research-based curriculum is essential for improving the curriculum and validating its effectiveness.
In atomic physics, the many-body problem is computationally challenging. When theory is well understood, accurate calculations can predict results that may be difficult to measure experimentally. For heavy elements or highly ionized systems, relativistic and quantum electrodynamic effects, not to mention nuclear effects, are less well understood and computation can assess the limitation of theory when results are compared with those from experiment.
This talk will describe how an honours degree in mathematics and chemistry from the University of British Columbia led to research in computational atomic physics.
Chairholder Catherine Mavriplis will give an overview of the activities of the NSERC / Pratt & Whitney Canada Chair for Women in Science and Engineering for Ontario. As the Chair approaches the end of its term, we'll look back at the impact it has had in several areas including interdisciplinary research in Communications, Education, Sociology and History. Since the Chair program launch, over 5000 people have been engaged in direct programming through 75 events, over 70 Canadian companies have been contacted, 15 Ontario universities have coordinated outreach efforts, a strong online following has been developed (900 Twitter and over 100 LinkedIn followers, 1400 monthly web visitors), and the Chairholder has made 10 media appearances. Learn how you can get involved in this and other regional and national activities.
Antihydrogen is the simplest pure anti-atomic system and an excellent candidate to test the symmetry between matter and antimatter. In particular, a precise comparison of the spectrum of anytihydrogen with that of hydrogen would be an excellent test of Charge-Parity-Time symmetry. The ALPHA antihydrogen experiment is able to produce and confine antihydrogen atoms in an Ioffe-Pritchard type magnetic neutral atom trap. Once confined, resonant transitions (eg. positron spin resonance transitions, 1S - 2S transitions) in the anti-atoms can be excited. In order to determine the resonant frequencies, the magnetic field seen by the antihydrogen atoms must be measured. This presents a significant challenge because the nature of the ALPHA apparatus effectively eliminates the possibility to insert magnetic probes into the antihydrogen trapping volume. Furthermore, because of the highly inhomogeneous nature of the magnetic trapping fields, external probes will not be able to measure the relevant magnetic fields.
To solve this problem ALPHA developed an in situ magnetometry technique based on the cyclotron resonance of an electron plasma in a Penning trap. This technique can measure the local field seen by the antihydrogen atoms and therefore determine the resonant frequency of the desired transition. With this technique ALPHA was able to perform the first ever resonant interaction with antihydrogen atoms by exciting the positron spin flip transition. This talk will present our in situ magnetometry technique, the methods used to excite and identify positron spin flip transitions in antihydrogen, and future spectroscopic measurements being pursued by ALPHA.
Panelists: Svetlana Barkanova (Acadia University), Melanie Campbell (University of Waterloo), Charlotte Froese Fischer (NIST), Adriana Predoi-Cross (University of Lethbridge), and Michael Steinitz (St. Francis Xavier University).
Panelists: Svetlana Barkanova (Acadia University), Melanie Campbell (University of Waterloo), Charlotte Froese Fischer (NIST), Adriana Predoi-Cross (University of Lethbridge), and Michael Steinitz (St. Francis Xavier University).
C. Haley1, D. Degenstein2, R. Cooney3, and A. Bourassa2
1 Honeywell Aerospace
2 University of Saskatchewan
3 Canadian Space Agency
The Canadian Atmospheric Tomography System (CATS) is a UV/visible/near-IR spectrometer designed to measure limb-scattered sunlight to derive vertically-resolved concentrations of O3, NO2, and BrO and aerosol extinction from the Upper Troposphere through the Stratosphere. CATS is a follow-on to the Optical Spectrograph and Infrared Imager System (OSIRIS) instrument currently in operation on the Odin satellite. In addition to monitoring the stratosphere and extending the long time-series provided by OSIRIS, CATS will focus on the study of fine scale phenomena in the Upper Troposphere/Lower Stratosphere (UTLS) region. To accomplish this new goal, the current CATS design incorporates the following modifications over OSIRIS:
1) Increased spectral range, focussed on an improved aerosol product.
2) Better spectral resolution, aimed at improved NO2 and BrO data products.
3) Improved vertical resolution and sampling, important for measurements in the UTLS region.
4) Better horizontal (along-track) sampling, to allow a tomographic retrieval approach to be used.
The current status of the CATS instrument design and development will be reviewed, highlighting the changes from the OSIRIS instrument design, the main outstanding technical risks, and the current development activities. Mission implementation options on either a dedicated microsatellite or as a payload on a small satellite will also be presented.
Bio
Neil Rowlands obtained his B.Sc (Engineering Physics) from the University of Alberta in 1985 and his Ph.D. (Astronomy) from Cornell University in 1991. At Cornell, he participated in the construction and use of infrared instrumentation for the Kuiper Airborne Observatory and the 5m Hale telescope at Mt. Palomar. After post-doctoral fellowships at the Université de Montréal, and at the Canada Centre for Remote Sensing where he worked with infrared instrumentation, he joined CAL Corporation (Ottawa, ON), now Honeywell Aerospace, as an electro-optical engineer. Since 1995 he has been developing space-borne scientific instrumentation for the space physics, atmospheric sciences and astronomy communities. He is currently a Staff Scientist at Honeywell in Ottawa. He has been working on the Canadian contribution to the James Webb Space Telescope (JWST) project, the Fine Guidance Sensor (FGS/NIRISS), since 1997.
Lasing in the nitrogen molecular ion
Mathew Britton, Patrick Laferriere, Ladan Arissian, Michael Spanner and P. B. Corkum
Joint Attosecond Science Laboratory, National Research Council and University of Ottawa, Ottawa, Canada
Intense light-matter interaction beyond a unimolecular limit faces unique challenges. In this regime, light and matter both have a non-negligible effect on each other. It is in this complex environment that lasing has been discovered on a nitrogen molecular ion transition [1].
We investigate the gain dynamics in nitrogen ions created from a neutral gas by an intense ultrashort laser pulse. To isolate the phenomenon, we use a one atmosphere pure-nitrogen 200 µm thick gas jet in a vacuum chamber. The gain is initiated by an 800 nm pump pulse with intensity in the range of 2-4 x10^14 W/cm^2 and pulse duration of 27 fs. A weak second harmonic probe pulse monitors the time dependence of the gain on the B (v=0) to X (v=0) transition.
We observe a peak gain of approximately 2 over a distance of about 200 µm and we measure gain as a function of nitrogen concentration, density, and intensity of the pump and probe. While the gain is present immediately (i.e. within the duration of the 27 femtosecond pump pulse) we observe two time-scales of decay: population inversion decay and rotational wave packet decay.
[1] see for example, G. Point, Y. Liu, Y. Brelet, S. Mitryukovskiy, P. Ding, A. Houard, and A. Mysyrowicz, “Lasing of ambient air with microjoule pulse energy pumped by a multi-terawatt infrared femtosecond laser”, OPTICS LETTERS, 29, 1725, (2014)
Atomic frequency comb, an atomic ensemble with comb shaped optical transition, is useful for multimode photonic quantum memory where a photon is absorbed collectively over the teeth of the comb resulting in a multipartite entangled state. The teeth of the comb constitute the individual subsystems participating in the entanglement. Since each tooth of the comb consists of a macroscopic number of atoms (typically several thousand), the atomic frequency comb (AFC) system presents an entirely different class of entangled state, which we call the colossal entangled state, i.e., multipartite entanglement between macroscopic systems.
In this work we propose an experimentally realizable witness and entanglement measure for the colossal entanglement in the AFC systems which is the entanglement between the teeth of the AFC. The witness is achieved in two steps. First we determine the minimum number of teeth coherently absorbing the photon, i.e., the coherence depth, from the signal to noise ratio of the light coming out of the AFC system. We argue that coherence depth is synonymous to entanglement depth, i.e., the minimum number of provably entangled systems, for the case when exactly one photon is present in the system. However, higher photon number component in the photonic states can cause differences between the coherence depth and the entanglement depth. We rectify this problem by estimating the probabilities P0 of no photon and P1 of having exactly one photon in the AFC system and using the bound on P1 for a given P0 and entanglement depth derived in [Hass et al. 2014]. Our method requires no prior knowledge of the number of teeth and is scalable. Furthermore, the method uses only macroscopic quantities to estimate the entanglement in the system, hence, is a suitable choice for the experimental demonstration of genuine multipartite entanglement. We have numerical and experimental results to support our entanglement witness.
Attaining an isolated attosecond pulse via high harmonic generation requires a temporal gate that can act within one half cycle of the driving field. Here, we use the interplay of nonlinear optics and spatio-temporal coupling to synthesize a half-cycle pulse. The half cycle pulse is centered at 1.8 microns, the idler of an optical parametric amplifier, and is intense enough to generate isolated attosecond pulses, tuneable over an octave in the extreme ultraviolet. I will also discuss this tool to study attosecond dynamics in the condensed phase.
An experimental lifetime of exceptional accuracy [9.573(4)(5) (stat)(sys)] has been reported by Lapierre et al. [1] for the $2p$ $^2P_{3/2}$ state of Ar$^{13+}$. This result is in good agreement with theory [2] when neglecting the effect of the anomalous magnetic moment (AMM), namely 9.582(2) ms, whereas the lifetime with the AMM correction is 9.538(2) ms, well outside the experimental error bar.
The theory method used by Tupisyn et al. started with the non-relativistic operator for the line strength of the $2p$ $^2P_{1/2}$ - $^2P_{3/2}$ transition and applied relativistic perturbation theory to the calculation of the lifetime as the inverse of the transition probability between these two fine-structure levels.
The General Relativistic Atomic Structure Package (GRASP2K) [3] is different. It relies on a variational method for determining wave functions for the initial and final states and then a matrix element for a transition operator which, in the Gordon form, can determine the lifetime both with and without the AMM correction, using the observed transition energy. Our lifetimes, 9.5804(16) ms and 9.536(16) ms, respectively are in excellent agreement with the Tupystin et al. values. In GRASP2K calculations, a check on the accuracy of the wave function is the prediction of the transition energy and this is the basis for our error estimate. Thus the discrepancy with experiment for Ar$^{13+}$ remains unresolved.
Data will be presented for other ions of the isoelectronic sequence. For K$^{14+}$ a measured value [4] is closer to the value with the AMM correction but the uncertainty in the experimental lifetime is so large that it includes both values.
REFERENCES
[1] A. Lapierre et al., Phys, Rev. Letters, 95, 183001 (2005)
[2] I.I. Tupitsyn et al., Phys. Rev. A, 72, 062503 (2005)
[3] P. Jonsson et al., Comp. Phys. Commun., 184, 2197 (2013)
[4] E. Trabert et al., Phys. REv. A, **64"", 034501 (2001)
Conventional imaging systems are limited in their optical resolution by diffraction. Thus, super-resolution techniques are required to overcome this limit. Many super-resolution techniques, such as structured illumination (SIM) [1,2], have been developed. However, these techniques often take advantage of linear optical processes and only a few techniques applicable to nonlinear optical processes exist [3, 4]. Here, we propose a scheme similar traditional SIM compatible with coherent nonlinear processes such as second- and third-harmonic generation and predict a resolution improvement of up to ~4 fold.
In traditional SIM the resolution is doubled by capturing and utilizing spatial frequencies that would otherwise not be received by the imaging system [1]. This may be further enhanced if the saturable absorption of the fluorescent molecules can be utilized to collect even higher harmonics of the spatial frequencies [5]. Since coherent imaging systems are linear with respect to the electric field, the concepts of structured illumination may be generalized to nonlinear widefield microscopy modalities where field amplitudes instead of field intensities are measured [6]. We show that this is possible through the use of second-harmonic and third-harmonic widefield microscopy and show a resolution improvement of three- and four-fold, respectively. Our results suggest that a spatial resolution smaller than 100 nm may be achievable.
References:
We study field and radiation attributes of photonic nano-resonators composed of alternating metal and dielectric layers, known as hyperbolic metamaterials (HMMs). HMMs offer the ability to confine light in ultra-small volumes and enhance its interaction with matter, thereby increasing the spontaneous emission rates of nearby photon emitters through the Purcell effect. It has been suggested that one of the first applications of HMM nanophotonics is in the domain of single photon sources for use in quantum cryptography and quantum plasmonics. Here we describe the physics of HMM nano-resonators in terms of open cavity resonant modes known as quasinormal modes (QNMs). Using an analytical expansion of the photon Green function in terms of QNMs, we introduce a modelling technique that is orders of magnitude faster that direct dipole solutions of Maxwell's equations and offers considerable insight into the HMM coupling effects. We show how coupling to HMM nano-resonators can substantially increase spontaneous emission rates of quantum emitters by an order of magnitude more than pure metal resonators. However, in contrast to recent claims, we also show that most of this emission increase is lost to Ohmic heating. We demonstrate that, counter-intuitively, less metal present in the HMM resonator results in larger non-radiative losses. Using our semi-analytical QNM theory, we describe how this increase in photon quenching originates from an increased overlap between the metal and dielectric, which allows fields to leak or tunnel into the lossy metallic regions. We thus conclude that HMM nano-resonators likely make poor single photon sources, and that pure metallic resonators are preferred for single photon applications.
Vortex beams form a class of beams carrying orbital angular momentum (OAM). A single photon carries lħ OAM where l represents the OAM state and a beam with non-zero OAM state has a zero intensity at its centre and a helical phase wavefront.
Vortex beams have gained interest for their applications in optical manipulation, optical communication and quantum information [1-3]. In particular, they can enhance communication security by improving the quantum key distribution (QKD) procedure [4]. The original proposal uses the photon polarization degree of freedom, resulting in each photon carrying a single bit. Since OAM states are unbounded and mutually orthogonal, using instead the OAM degree of freedom as a basis enables far greater channel capacity. As QKD requires superpositions of states, this improved version of QKD requires superpositions of different OAM values.
There are many ways to generate vortex beams with bulk optics, such as spiral phase plates, spatial light modulators, q-plates and cylindrical lens mode converters [5-8]. However, an integrated photonic approach has advantages over bulk optics because of its scalability, stability and small size. It turns out that ring resonators with lateral grating elements, called angular gratings, radiates a vortex above the structure when on resonance [9,10]. To generate a superposition of vortex beams, we expand this idea to a single ring with two sets of gratings, one on the inside wall and one on the outside. We then show with simulations that, after post-selecting on one of the circular polarizations, we can generate OAM superposition states based on the number of grating elements for each grating.
Cd$_2$Re$_2$O$_7$ is a pyrochlore superconductor with a transition temperature (T$_C$) near 2 K. The results of Raman scattering and far-infrared reflectance measurements will be presented. The temperature dependence of optical phonons has been investigated above and below T$_C$ via IR spectroscopy, and as a function of Oxygen and Cadmium isotope substitution in the normal state via Raman scattering. The dominant presence of lattice vibrational modes in the optical spectra suggests that electron-phonon interaction plays an important role in the normal and superconducting state properties.
The InGaN/GaN material system is a promising candidate for the growth of highly efficient solar cells. With direct nanowire growth on silicon, superior light trapping properties at low costs are possible. With the introduction of quantum well superlattices, intermediate states well below the bandgap of GaN enable the absorption of lower energy photons that would otherwise pass through the structure. In this work, we investigate the potential of InGaN/GaN nanowire heterostructures as candidates for novel solar cell designs on silicon via a combination of optical/electrical characterization and computer-aided device simulation.
The InGaN/GaN nanowire heterostructures were grown via radio frequency plasma-assisted molecular beam epitaxy (MBE) on Si (111) [1]. Nanowires were grown as axially oriented p-i-n junctions with p-GaN and n-GaN regions as the emitter and base, respectively. Ten InGaN/GaN QD/s form the intrinsic region.
The device is modelled as a bulk structure with ten quantum wells as the nanowire dimensions approach 100 nm. The large diameter of the QDs (~50 nm) permits the treatment of the quantum dots as quantum wells, since confinement is primarily along the growth axis. Confined states are solved via the Schrödinger equation for ten coupled quantum wells using Crosslight Apsys for various coupling regimes.
Current-voltage measurements, photoluminescence and electroluminescence spectroscopy of the nanowire solar cells were performed. External quantum efficiency (EQE) was measured as a function of increasing beam intensity and wavelength. The presence of non-negligible current generated at wavelengths below the bandgap of GaN, suggest photons are sequentially absorbed in the InGaN QDs and into the GaN conduction band for collection. This fulfills one of the requirements of an intermediate band solar cell. Future directions and design possibilities are discussed.
Correlation is used to analyze the daily returns of pairs of unrelated stocks with similar ticker symbols. By encoding the relationship between two Chinese ticker symbols by three digits, we found that, in contrast to the developed Western markets, comovement of stocks with similar ticker symbols is relatively common in the Taiwanese market. When the last two characters are identical, comovement influences the daily return of ~40% of stock pairs. These results suggest that investor confusion has a important role to play in the return of stocks in developing markets.
The anti-de Sitter/conformal field theory correspondence and the membrane paradigm have illuminated many aspects of string and field theory, giving key insights into what a quantum theory of gravity might look like, while also providing tools to study a wide range of strongly coupled systems. In essence, these ideas are a statement of the holographic principle: a fundamental observation about our universe which states that all of the information contained in a bulk region of space-time can be encoded on the boundary of that region. However, these approaches are generally restricted to situations where knowledge of the boundary of space or the entire future history of the universe is required. From a practical point of view this is unsatisfactory. As local observers, we are not generally able to access these types of boundaries.
In an attempt to address these issues we use `gravitational screens' as quasi-local observers. A gravitational screen is a two dimensional space-like hypersurface surrounding an arbitrary region of space-time. Projecting Einstein's equations onto the screen results in the equations of non-equilibrium thermodynamics for a viscous fluid, which encode all of the information present inside the screen in terms of the holographic fluid on the surface, without being restricted to the event horizon of a black hole or to spatial infinity. In this project we study the dynamics and equations of state for screens in various space-times. Of particular interest are screens/geometries which have fluids obeying the second law of thermodynamics, since it is not obvious that an arbitrarily chosen screen will behave physically. We determine the properties of the fluids that arise from different background geometries, discuss their interpretation, and clarify the relationship between the gravitational degrees of freedom in the bulk, and the thermodynamic degrees of freedom on the screen.
Lead is an interesting target material for a supernova detector. The neutron excess in lead nuclei leads to Pauli-blocking of the charged-current $\overline{\nu_e}$ interaction, and the high atomic number of lead Coulomb enhances $\nu_e$ over $\overline{\nu_e}$ giving a large $\nu_e$ CC neutrino interaction cross-section. This leaves a lead-based SN detector dominantly sensitive to $\nu_e$ through CC channels and to a lesser extent to $\nu_x$ through NC channels. Therefore, such a detector complements the dominantly $\overline{\nu_e}$ sensitivity of current water Cherenkov and liquid scintillator detectors worldwide. Supernova neutrinos, which undergo CC or NC interactions with the lead nuclei, eject one or two neutrons; so instrumenting lead with neutron detectors can be a cost efficient approach to robust supernova detector. The HALO detector at SNOLAB, running since May 2012, was designed to be a high live-time, low-maintenance, and low-cost dedicated supernova detector. HALO consists of a core of 79 tonnes of lead instrumented with 376 m of $^3{\rm He}$ neutron detectors and surrounded by a layer of water shielding. The measurement of the ratio of two detected neutrons to one neutron has been shown to provide a measure of the temperature of the neutrinos, due to the distinct thresholds for one and two neutron emission in neutrino-lead interactions. Since October 2015 HALO has been a part of the network of SN neutrino sensitive detectors participating in the Supernova Early Warning System (SNEWS). The decommissioning of the OPERA detector at LNGS has potentially made available 1.3 kilo-tonnes of lead for future experiments. Efforts are currently underway to explore neutron detection technologies that could be used to instrument this sixteen-fold increase in mass for a more sensitive version of HALO at LNGS. The status of HALO at SNOLAB and plans for HALO at LNGS are reported.
Despite considerable technical progress in recent years, DNA sequencing is still a time and resource consuming procedure. Finding inexpensive, easy, and reliable alternative DNA sequencing strategies is a tall task. As recently demonstrated on biological pores, a promising approach to this challenge is the use of nanopores to characterize single strands of DNA. The advantages of nanopore technology for the characterization of DNA are manifold. The ability to directly interrogate single molecules electrically in the nanopore makes this approach very competitive over conventional DNA sequencing techniques, by sample preparation, reducing cost, and enabling point-of-need sequencing. However before solid-state nanopore devices can also be used to sequence DNA some challenges need to be overcome. The transport dynamics of DNA through solid-state nanopores have been intensively studied for a few years but the control of motion and speed proves to be very difficult on solid-state devices. In this poster, branched DNA molecules specifically designed to measure intra-molecular translocation velocities of DNA polymers through solid-state nanopores fabricated by controlled breakdown (CBD) will be described. Finally, preliminary results of the building blocks of these branched DNA molecules will be presented. The ultimate goal is to develop a better understanding of the kinetics of DNA transport in these pores, which is one of the crucial steps towards implementing solid-state nanopore based DNA sequencing.
The last decade has seen significant advancements in nanofluidic devices to study transport processes at the single-molecule level. In particular, exciting results have been obtained through the study of passage of nucleic acids through solid-state nanopores (ssNP). ssNP are nanometer-sized holes in thin dielectric membranes, which have emerged as a versatile tool to investigate a wide range of phenomena involving DNA and proteins. Controlled breakdown (CBD) is a technique for fabricating such ssNP involving sustained high electric fields that was recently developed by our group as a low-cost, high-yield alternative to traditional focused ion-beam/TEM drilling methods. We have characterized the ability of CBD to create pores in substrates of increasing complexity. Devices incorporating different materials and advanced functionalization represent a crucial step toward refining the capabilities of ssNP as single-molecule sensors of electrophoretically-driven biomolecules, and increasing their range of potential applications. To this end, we demonstrate pore fabrication by CBD through multilayer dielectric membranes equipped with an embedded metal electrode. A thin gold layer was deposited on 10/30 nm SiNx membranes by thermal evaporation, followed by the addition of a second dielectric (HfO2) to both sides using atomic layer deposition. After pore fabrication, conductance-based models are used to extract an effective nanopore diameter, which can be compared to values obtained from TEM imaging and by using passing, voltage-driven DNA as a molecular-sized ruler through its effect on ionic current. Applied to these membranes, the CBD process resulted in structures consisting of a nanopore surrounded by a concentric area of removed metal 100s of nm in diameter. By using laser-excited Ca2+ fluorescent dyes, the ability of these structures to act as zero-mode waveguides, attenuating the fluorescence signal away from the pore and enabling high-contrast optical detection of single-molecules, can be characterized.
Nanopores have proven to be useful single-molecule sensing tools in the past two decades. One of the many promising applications of these electrical nano-sensors is to act as molecular counting devices with single-molecule sensitivity, essentially determining concentrations of specific molecular species. To achieve this, it is essential to develop a better understanding of the nanopore capture process and the factors affecting the reliability and accuracy of such nano-devices.
This poster will present our investigation of the mechanisms controlling the nanopore capture process and the factors affecting its reliability for nanopores specifically fabricated using the recently developed controlled dielectric breakdown (CBD) technique. Using 50bp dsDNA to translocate through the nano-sensors, the energy barrier and system resolution limit of pores of different sizes are studied and are used to determine what parameters are optimal for efficiently counting this type of molecule.
Patients who receive targeted radionuclide therapy (TRT) for cancer treatment suffer from damaging unwanted healthy body tissues and may receive unexpected dose to healthy organs as an inadvertent consequence of their treatment. In particular, they risk significant dose to critical and secondary organs, e.g. bone marrow, gonads, uterus etc., which may cause long- or short- term damage for entire life. The unintended dose to organs varies widely depending on the types and energy of the emitted radiation and their decay scheme. Royal University Hospital at University of Saskatchewan recently started Yitrium-90 (Yt-90) treatment available for the liver patients in a drug name TheraSphere. Several other radionuclide treatments, e.g. Radium-223, Strontium-89 will be available in coming months. Till now, MIRD principle is the only methodology that is being widely used for TRT dosimetry and there is no commercial program available that can be fitted over wide varieties of radionuclide treatments. Medical Imaging team at Royal hospital is currently building a customized virtual treatment planning system that is capable to combine personalized CT images to advanced particle transport framework. This presentation showcases design features and initial results of this planning system.
The proposed virtual planning system consists of series of 2-D DICOM images of the patient captured by CT scanner. The 2-D data set are transformed to 3-D object (composed of thousands of voxels (volume of the pixels) that is readable to a particle transport framework. This framework is capable for dose modeling to specific organs. Initially, this system will be used in planning Yt-90 for liver-treatment and Strontium-90 for treatment of bone. In the long run, the system will be upgraded for treatment of alpha emitters with substantial improvements in particle transport data framework. This customized user friendly tool can be used by the clinicians in parallel to existing commercial planning system in order to cross-validate diagnosis and treatment plan for individual patient.
The initial design is completed and been tested for several radionuclides. The presentation will include the results and future challenges.
The magnitude and the temperature dependence of the superconducting order parameter $\Delta(T)$ of
single-crystals of Cd$_2$Re$_2$O$_7$ ($T_c$ = 1.02~K) was measured using point-contact
spectroscopy. In order to fit the conductance spectra and to extract the order parameter
at different temperatures we generalized
the Blonder-Tinkham-Klapwijk theory by including the self-energy of the quasiparticles into the Bogoliubov equations.
This modification enabled excellent fits of the conductance spectra.
$\Delta (T)$ increases steeply below the superconducting transition temperature of 1.02 K
and levels off below $\sim$0.8 K
at a value of 0.22(1) meV, $\approx $40 \% larger than the BCS value.
Our results indicate the presence of a strong electron-phonon interaction and an enhanced quasiparticle damping
and may be related to a possible phase transition within the superconducting region at $\sim$0.8 K.
After efficiency, lifetime is the second most important parameter for molecular photovoltaic devices. In organic solar cells (OPVs), heterojunctions play a defining in device stability. They also control the major processes: charge separation relies on effective organic/organic interfaces; charge transport is critically determined by the structure of the thin film, controlled by the organic/inorganic interfaces with substrates; and charge extraction can only occur at high quality inorganic/organic interfaces at the electrodes.
This contribution reviews the current state of the art with regards to interfacial stability of electrode/active layer interfaces to understand the performance of OPVs. From examples relating to interfacial chemical reactions, interfacial morphological changes, and interfacial electronic level modification, a comprehensive picture of the role of the organic-electrode interfaces in device stability can be formed. Beginning with a brief overview of general degradation in organic devices, including definitions and measurement approaches, this contribution then focuses on two key interfaces within the device architecture. The first is the bottom contact (substrate) interface, where chemical reactions and dewetting are the two main mechanisms of device degradation. The second is the top contact interface, which is prone to oxidation, interdiffusion, blistering and delamination, and inhomogeneous loss of performance (dark spots). For both bottom and top contact interface degradation, various approaches to overcoming device instabilities are given, with special attention to the various interlayers that have been introduced for improved stability. Examples are given where degradation mechanisms are used advantageously to produce novel devices and surprising solutions to device degradation.
This presentation will summarise a body of work emanating from our research group over the past five years. It focuses on correlating the properties of excitons with the complex solid-state microstructure in macromolecular semiconductors. In general, the optical properties of polymeric semiconductors are governed fundamentally by the interplay of electronic interactions occurring within a given polymer chain and those occurring between chains that constitute crystalline motifs. The competition between through-bond (intrachain) and through-space (interchain) electronic coupling determines two-dimensional spatial extent of excitons. The balance of these competing interactions depends very sensitively on solid-state microstructure of the polymer film (e.g. polycrystalline, semicrystalline with amorphous domains, etc.) Via analysis of absorption and photoluminescence spectral lineshapes, we have developed a protocol by which the spatial coherence of excitons, the degree to which the disordered landscape is correlated, and the interplay of intra- and interchain excitonic coupling in disordered polymeric semiconductors can be predicted when processing thin films within devices. I will outline novel ultrafast optical probes developed to probe in more detail the spectral correlations arising from excitonic properties of this class of materials.
Have stars that end up as isolated white dwarfs lost their initial angular momentum as suggested by the relatively long rotation periods measured at their surfaces through spectroscopy? Could it be instead that a large fraction of that angular momentum is bound in a fast rotating core, hidden from direct observations, as proposed by some theories favouring a weak rotational coupling between the radiative core and the convective envelope in the previous red giant phase of stellar evolution? To answer these questions, we need to map the internal rotation pro?files of representative white dwarfs.
In the last few years, we have devised a way to exploit the signature that rotation imprints on the pulsation properties of white dwarfs in order to carry out such a mapping. The technique is particularly useful for pulsating white dwarfs of the so-called GW Vir type, for which the mapping can be done over essentially the full mass of the star, thus allowing a determination of the total angular momentum.
Est-ce que les ?étoiles qui terminent leur vie stellaire sous la forme de naines blanches isol?ées ont perdu l'essentiel de leur moment cinétique comme semblent le sugg?érer les mesures de périodes de rotation de leurs couches superficielles obtenues par spectroscopie? Se pourrait-t-il, au contraire, qu'une grande fraction du moment cinétique initial soit contenue dans les r?égions internes inacessibles ?à l'observation directe comme le proposent certaines th?éories de transfert (inefficace) de moment cinétique entre le noyau radiatif et l'enveloppe convective dans la phase ?évolutive des g?éantes rouges qui pr?écède celle des naines blanches? Pour répondre ?à ces questions, il est nécessaire de cartographier le pro?fil de rotation interne de naines blanches représentatives.
Au cours des récentes années, nous avons d?éeloppé une méthode pour exploiter la signature de la rotation sur les propri?étés de pulsation des naines blanches et de déterminer ainsi ce profil de rotation interne. La technique est particulièrement utile pour les ?étoiles pulsantes de type GW Vir, pour lesquelles essentiellement toute la masse peut être ?échantillonnée, ce qui permet de calculer le moment cinétique total.
2012 brought the first reports of a new member of the 2D material family: a hexagonal honeycomb of Si atoms deposited on the Ag(111) surface called “silicene”[1]. The characteristics and stability of freestanding silicene had previously been theoretically explored [2], and there was a strong push to determine if the epitaxial sheets possessed the promising qualities of their hypothetical freestanding counterparts. Initially, ARPES experiments were thought to indicate that epitaxial silicene had a gapped Dirac cone in its electronic structure [1], as would be expected of freestanding silicene with a broken inversion symmetry. This enticing result, however, would be later overturned through a combination of experimental and theoretical techniques [3-5], and it would eventually be concluded that the epitaxial silicene sheet was in fact metallic with a strong cohesion to the underlying Ag(111) face. However, this conclusion would prove controversial [6,7], as the ambiguity of the ARPES data left some room for interpretation as to whether specific electronic features belonged to the epitaxial Si, the Ag substrate, or represented a hybridization between the two.
Soft X-ray emission and absorption spectroscopy (XES and XAS) are synchrotron-based experimental techniques for directly probing the (element-specific) partial density of electronic states (PDOS) in the valence and conduction bands of a material. When performed at the Si L2,3 emission and Si 2p absorption edges, XES and XAS allowed us to unambiguously show that the Si valence and conduction states were continuous across the Fermi energy; i.e. that the silicene overlayer was indeed metallic [3]. However, for the material to be of use, it must be isolated from the substrate. One suggested way of achieving these characteristics is to produce a multilayer of silicene on the Ag(111) surface. However, other reports insist that bilayers and multilayers are inherently unstable, collapsing into bulk Si nanocrystals shortly after the monolayer deposition is complete [8].
Our DFT calculations [9] predict a stable, AA-stacked silicene bilayer on Ag(111) that corresponds nicely to the scanning tunnelling microscopy (STM) bilayer observations. Unfortunately, these same DFT calculations predict a similar electronic structure as that of the monolayers, namely metallic and bound to the Ag(111). However, our XES and XAS measurements indicate a transition to bulk, sp3-hybridized Si beginning shortly after the completion of a monolayer, supporting the low-energy electron microscopy study that first suggested the nucleation of the silicene sheets to bulk crystals [9]. Finally, we will discuss our recent study in which we explore how Silicene oxidizes [10].
References:
[1] P. Vogt, P. De Padova, C. Quaresima, J. Avila, E. Frantzeskakis, M.C. Asesnsio, A. Resta, B. Ealet and G. Le Lay. Phys. Rev. Lett. 108, 155501 (2012).
[2] S. Cahangirov, M. Topsakal, E. Aktürk, H. Şahin and S. Ciraci. Phys. Rev. Lett. 102, 236804 (2009).
[3] N.W. Johnson, P. Vogt, A. Resta, P. De Padova, I. Perez, D. Muir, E. Z. Kurmaev, G. Le Lay and A. Moewes. Adv. Funct. Mater. 24, 5253 (2014)
[4] S. Cahangirov, M. Audiffred, P. Tang, A. Iacomino, W. Duan, G. Merino and A. Rubio. Phys. Rev. B 88, 035432 (2013).
[5] D. Tsoutsou, E. Xenogiannopoulou, E. Golias, P. Tsipas and A. Dimoulas. Appl. Phys. Lett. 103, 231604 (2013).
[6] S. Huang, W. Kang and L. Yang. Appl. Phys. Lett. 102, 133106 (2013).
[7] J. Avila, P. De Padova, S. Cho, I. Colambo, S. Lorcy, C. Quaresima, P. Vogt, A. Resta, G. Le Lay, M. C. Asensio. J. Phys.: Condens. Matter 25, 262001 (2013).
[8] P. De Padova, P. Vogt, A. Resta, J. Avila, I. Razado-Colambo, C. Quaresima, C. Ottaviani, B. Olivieri, T. Bruhn, T. Hirahara, T. Shirai, S. Hasegawa, M. C. Asensio and G. Le Lay. Appl. Phys. Lett. 102, 163106 (2013).
[9] N.W. Johnson, D. Muir, E.Z. Kurmaev, and A. Moewes, Adv. Funct. Mat. 25, 4083(2015).
[10] N.W. Johnson, D. Muir, A. Moewes, Sci. Rep. 6, 22510 (2016).
Fluorescence of single dipole emitters near a dielectric interface are studied. A 15 nm thick layer of polystyrene lightly doped with Rhodamine 6G was spin-cast onto cleaned glass and PMMA coated glass slides. Flourescence lifetime was found to increase by a factor of three as the PMMA spacer layer thickness was increased. This lifetime increase is accounted for by a change in the ensemble averaged distribution of the dipole orientation from isotropic to perpendicular to the interface as the spacer layer thickness increases. This reorientation occurs proceeds takes place over a 200nm range (from 100 to 300nm) of buffer layer thicknesses. The ability to tune dipole orientation and hence charge injection into 2D materials.
Under current admission conditions for the Faculty of Science at the University of Ottawa, students entering our faculty need to have equivalents of two advanced math courses (Advanced Functions, and Calculus and Vectors), as well as two of the three 4U science courses (Chemistry, Biology and Physics). At present time, roughly 30% of all admitted students are missing one of them, and it is invariably a physics course. Altogether, they make up more than half (nearly 350 in fall of 2015) of the students taking introductory life-science physics course (PHY1321).
To address this issue within the program’s current credit constraints, we created a course known as PHY1331, in which students are offered an extra 80 minutes lecture time every week to be spent on basic mechanics concepts.
Over the last ten years, this approach has been used with some success, when measured by the grade gaps between two groups of students at the start of the semester and at the end. In the fall of 2015, the online component of the course has been offered to students as a way to foster their familiarity with fundamental concepts of mechanics.
It was offered as an option rewarded with extra credit against the final exam.
By scoring the maximum points, students would be able to lower their final exam weight by 25%. Roughly 50 students participated in this exercise.
In the presentation, the participants’ results on three identical tests will be compared with the results of non-participants, as well as with the scores of the students from PHY1321. The correlations and effectiveness of the proposed approach will be discussed, together with the specifics of the online course component’s structure. The conclusions and the resulting modifications for the future mandatory, blended course of this type will also be presented.
In this session we will discuss recent developments related to the P.Phys. designation and a review of the ongoing efforts to improve the P.Phys. model. We will focus on professional development programs typically in place for other professional designations and potential improvements in this area for P.Phys.
Dans cette séance, nous allons discuter des développements récents liés à la désignation phys. et un examen des efforts continus pour améliorer le modèle de phys. Nous allons nous concentrer sur les programmes de perfectionnement professionnel généralement en place pour d'autres désignations professionnelles et les améliorations possibles dans ce domaine pour la désignation phys.
MC – Richard Bourgeois-Doyle from NRC
Basic and applied physics and standards
Dr. Nelson Rowell
NRC Photometry and Spectrophotometry
Chemical physics
Dr. Albert Stolow
Canada Research Chair in Molecular Photonics, University of Ottawa
Astrophysics
Dr. Gregory Fahlman
NRC General Manager, NRC Herzberg
Biological physics
Dr. Linda Johnston
NRC Nanoscale Measurement
Physics for industrial applications
Dr. Sylvain Charbonneau
Associate Vice-President, Research, University of Ottawa
Scattering amplitudes of massless particles have proven to be very interesting mathematical objects. While clearly defined in terms of Feynman diagrams, these seemingly complicated functions of several complex variables become shockingly simple after miraculous cancellations. In this talk I will explain how Riemann surfaces, cluster algebras and the positive Grassmannian are some of the mathematical ideas responsible for this surprising behavior of standard quantum field theory S-matrices.
Canada occupies 25% of the Arctic and, of our three ocean coasts, the Arctic Ocean’s is by far the longest while being the least known. The strategic and economic importance of the North for Canadians and the world cannot be minimized. More than 100 000 people live in the north, a majority of whom are First Nations and Inuit. In view of the importance of the Polar Regions to Canadians, our government decided a year ago to create its own national polar agency, Polar Knowledge Canada (POLAR), with a goal of reconciling our knowledge base of the Arctic with the challenges we face. The objective of this presentation is enlighten my fellow physicists to the challenges and opportunities that comes from polar research.
There are presently some significant gaps in our polar knowledge which much be filled to safeguard the region and its people, as well as Canadians in general. The Arctic suffers from a phenomenon of Polar Amplification of its climate temperature as compared to pre-industrial times. While in the south we must adapt to a present 0.8°C rise, in the north, this value is more like an additional 6°C. For example, no fewer than five of the global climate change tipping points, locations where a small perturbation to the climatic stable state triggers a transition to an alternate climatic state, are located within our national boundaries or are tributary to the Canadian Arctic. In Earth System Science, a tipping point occurs when a small perturbation to a global climatic stable state, triggers a disproportionate transition to an alternate climatic state. Challenges to our Canadian sovereignty is of usual occurrence there, as marked by the frequent presence of foreign vessels. Our people, north of the 70th parallel, must burn costly, low-efficiency diesel to power and heat their communities, resulting in high economic and environmental impacts that constrain both their livelihood and quality of life. Sadly, Canada does not have the requisite 25% of the world’s polar-interested scientists to fill the knowledge gaps inhibiting solutions from being implemented. Photonics as a prime role to play in the Arctic. POLAR must work with international and national partners to achieve its national mission.
Neutrino oscillation shows that different flavours of neutrinos, νe, νμ, and ντ, mix like quarks. Thus CP violation is expected due to the complex phase in the mixing matrix as is in the quark case. Since the observables of CP violation, namely difference between neutrino and anti-neutrino oscillations, is proportional to the three mixing angles, sinθ12, sinθ23 and sinθ13, all the three angles need to be large enough for the CP violation to be accessible. Since the discovery of the first neutrino oscillation in 1998, all these three mixing angles have been observed to be surprisingly large. The last angle sinθ13 was observed by T2K long baseline neutrino and Daya Bay/Reno reactor neutrino experiments. Because the T2K observable is also sensitive to CP violation, the comparison between T2K and reactor experiments shows a hint of potentially large effect due to CP violation phase. If the CP violation in neutrino oscillation is indeed large, it could naturally explain the matter vs. anti-matter asymmetry of the universe. An extension of T2K is being proposed to discover this leptonic CP violation in the decade. In this talk, I will present the status and prospect of the CP violation measurement in neutrino oscillation.
The Twin Higgs model seeks to address the little hierarchy problem by making the Higgs a pseudo-Goldstone of a global $SU(4)$ symmetry that is spontaneously broken to $SU(3)$. Gauge and Yukawa couplings, which explicitly break $SU(4)$, enjoy a discrete $\mathbb{Z}_2$ symmetry that accidentally maintains $SU(4)$ at the quadratic level and therefore keeps the Higgs light. Contrary to most beyond the Standard Model theories, the quadratically divergent corrections to the Higgs mass are cancelled by a mirror sector, which is uncharged under the Standard Model groups. However, the Twin Higgs with an exact $\mathbb{Z}_2$ symmetry leads to equal vevs in the Standard Model and mirror sectors, which is phenomenologically unviable. An explicit $\mathbb{Z}_2$ breaking potential must then be introduced and tuned against the $SU(4)$ breaking terms to produce a hierarchy of vevs between the two sectors. This leads to a moderate but non-negligible tuning. We propose a model to alleviate this tuning, without the need for an explicit $\mathbb{Z}_2$ breaking sector. The model consists of two $SU(4)$ fundamental Higgses, one whose vacuum preserves $\mathbb{Z}_2$ and one whose vacuum breaks it. As the interactions between the two Higgses are turned on, the $\mathbb{Z}_2$ breaking is transmitted from the broken to the unbroken sector and a small hierarchy of vevs is naturally produced. The presence of an effective tadpole and feedback between the two Higgses lead to a sizable improvement of the tuning. The resulting Higgs boson is naturally very Standard Model like.