Low-frequency resistance noise study across the metal-insulator transition in VO2 Nanobeams and thin films
Adhikari, Dasharath (United States)
Vanadium dioxide (VO2) exhibits a sharp metal-insulator transition (MIT) at a critical temperature(Tc) ~ 330 K. The significance of a Peierls-type instability or a Mott-Hubbard-type transition near Tc has been a topic of discussion for many years. We present results from resistance noise spectroscopy study of MIT in VO2 thin films and Nanobeams. The power spectral density (PSD) of the fluctuations near Tc show a completely different feature. In thin films, the PSD increases by orders of magnitude and have a peak near Tc. It also deviates from typical 1/f behavior near Tc. The scenario is quite different in the case of Nano-beams. The probability density function (PDF) of the fluctuation is non-Gaussian in nature in thin films near Tc whereas the fluctuations are Gaussian at all temperatures in single crystal nanobeams. Our results suggest that the transition likely occurs as a single domain phenomenon in nanobeams whereas the nucleation and propagation of multiple domains of opposite phase are significant near Tc in thin films. The influence of the coexistence of phases on electrical transport will be discussed based on our analysis of the 1/f behavior, PSD, PDF and the second spectrum of noise.
Effect of microstructures on luminescence kinetics in Ce: YAG transparent ceramics
Agarwal, Sahil (United States)
Luminescence quenching with temperature is frequently observed in materials. It is well known that photoluminescence (PL) emission decays with increasing temperature in all systems. In this work, the luminescence properties of two differently fabricated Ce: YAG transparent ceramics and single crystal have been studied using photoluminescence (PL) and thermoluminescence (TL) and the dependence of the luminescence kinetics on microstructure has been investigated. Here we show that the temperature dependence of PL in transparent ceramics has unique behavior and strong dependence on the microstructure and presence of defect centers. Both grain boundaries and defect clusters provide a large number of traps that strongly affect PL kinetics. Thermally stimulated luminescence and positron annihilation spectroscopy revealed the nature and characteristics of these traps. The high PL intensity persistent at high temperatures in transparent ceramics may open up possibilities for new applications.
Dynamical phase-mixing near metal-insulator transition in CuIr2S4 thiospinel crystals
Ali, Ahmed (United States)
CuIr2S4 is a strongly correlated material that shows a metal-insulator transition (MIT) at a critical temperature (Tc) ∼230 K. It is an important system to study the interplay of electronic, orbital, structural as well as magnetic degrees of freedom since it manifests simultaneous charge-ordering and spin-dimerization during the MIT. The power spectral density (PSD) increases by orders of magnitude and deviates from a typical 1/f behavior near Tc and is attributed to the formation of domains of the opposite phase. Significant non-Gaussianity observed in second spectrum and PDF of the fluctuations as well as the deviation of α from the expected value of ∼1 near Tc, all indicating the increase in charge carrier scattering events near the transition region. An abrupt conductivity change with a threshold nature can be triggered electrically from the insulating phase and the PSD analysis of the measured fluctuations suggest a significant role of the domains.
Quantification of vascular parameters in a rat model of tumor angiogenesis with contrast-enhanced micro-CT imaging
Ayala-Dominguez, Lizbeth Rossana (Mexico)
Contrast-enhanced micro-computed tomography (CE micro-CT) allows to capture the spatial and temporal heterogeneity of tumor angiogenesis in preclinical studies. However, CE micro-CT is not widely used since modern scanners are required. The aim of this work was to evaluate the potential of single energy (SE), dual energy (DE) and dynamic contrast-enhanced (DCE) micro-CT imaging protocols to quantify vascular parameters in a rat model of tumor angiogenesis. The settings for image acquisition (kilovoltage, current, additional filtration, and number of projections) and contrast medium administration (type of contrast agent, dose, and injection rate) were optimized. The enhancement (ΔHU) and relative blood volume (rBV) were quantified for the abdominal aorta, muscle, and tumor regions (core, periphery, and the complete tumor). Results of rBV obtained with SE, DE, and DCE protocols were similar. ΔHU and rBV in tumor periphery were higher than in muscle and tumor core. These results agree with the histopathologic evaluation of the tumors, since a necrotic core and a vascularized periphery were observed. In conclusion, the imaging protocols developed in this work were capable of quantifying the angiogenic status of a rat model of tumor angiogenesis. The novelty of this work is that the imaging protocols were implemented in a microCT system that was not originally designed for quantitative imaging, demonstrating the potential of quantitative CE micro-CT imaging in preclinical research.
Line Identification in the Herschel SPIRE Spectral Feature Catalogue
Benson, Christopher (Canada)
The Hershcel Space Observatory completed four years of observations exploring the far-infrared (FIR) and submillimeter (sub-mm) universe in April 2013 with the depletion of its liquid cryogens. The Spectral and Photometric Imaging REceiver (SPIRE) was one of three focal plane instruments on board Herschel, consisting of both an imaging photometric camera and an imaging Fourier Transform Spectrometer (FTS). The SPIRE FTS provided a wealth of molecular species and fine structure lines covering a frequency band of 447–1546 GHz which recently has become even more accessible to scientists through the SPIRE Automated Feature Extraction Catalogue (SAFECAT, https://www.cosmos.esa.int/web/herschel/ spire-spectral-feature-catalogue), the result of an automated spectral feature extraction algorithm developed for use with SPIRE data [1]. SAFECAT provides frequency, signal to noise, and radial velocity measurements of all prominent spectral features in all high-resolution SPIRE FTS observations. The scope of this work is to use the information provided in the Feature Finder (FF) catalogue to identify the molecular or atomic species corresponding to the catalogue features, and intelligently discover complementary features in the SPIRE FTS spectra that may be of lower signal to noise and have been missed by the SPIRE spectral FF routine. Spectral features measured by the FF are compared against a template list of 306 atomic or molecular lines that are commonly found in astronomical sources at far-infrared wavelengths. This information provided by the line identification routine allows us to look for lines that may have been missed by the initial pass of the FF routine. We present our automated routine’s discovery of 95 spectral features that were not previously included in SAFECAT, specifically identified within SPIRE calibration targets, and compare them to previous line identification performed by Hopwood et al. [3] for these sources. Our analysis attempts to provide a large-scale automated identification of the 167,525 lines contained in SAFECAT. We also estimate that our analysis could add more spectral lines to SAFECAT on the order of ∼ 1000 when applied to the full SPIRE observation archive.
Variable Temperature NMR investigation of lithium ion transport in a highly conducting solid polymer electrolyte
Bhattacharyya, Sahana (United States)
Reports of high ionic conductivity and expanded electrochemical window of aqueous electrolytes enabled by very high salt concentration (~ 20m)1,2 and the “salt-in-polymer” concept3 have inspired this investigation of a solid PEO-salt-water system. The dissolved salt (LiTFSI) concentration approaches its solubility limit and in combination with water association succeeds in inhibiting crystallization of the PEO matrix leading to higher conductivity. Room temperature ionic conductivity in these solid-like polymer electrolytes is sufficiently high (2 mS-cm-1 ) for battery application. Ion transport characterization has been done by NMR pulsed field gradient diffusion measurements at a wide range of temperature for 7Li and 19F as the cation and anion, respectively4 . Results show that the degree of salt ion dissociation in these electrolytes is sufficiently high. The lithium transport number (proportional to the fraction of current carried by the Li ions) exceeds 0.6 for the whole temperature range, which is unusually high for polymer electrolytes.
Engineering Topological Quantum Dots in Graphene
NanoribbonsButler, Paul (United States)
The recently established on-surface synthesis methodology has allowed us to engineer atomically precise Graphene Nanoribbons (GNRs). This unprecedented control over atomic geometry allows us to explore topological states in GNRs. We interconnected GNR segments of different topological character to conceive heterostructures hosting topologically protected interface states at the Fermi level. We synthesized structures consisting of Armchair Graphene Nanoribbons (AGNRs) of N = 7 and N = 9 atoms in width to produce these localized states. Neighboring states hybridize to give bonding and antibonding combinations. The emergent quantum dots are characterized using Scanning Tunneling Microscopy and Spectroscopy. Our research provides the preliminary tools for engineering both isolated states and bands. It is predicted that the energy gap can be precisely tuned over an order of magnitude in topological GNR quantum dots and periodic heterostructures—making GNRs a promising candidate for use in future nanoscale electronic applications.
Examining lattice mode vibrations of calcite using spectroscopic techniques
Campbell, Stephen (Canada)
The physical, electrical, and thermal properties of a material can often be explained by considering the atomic composition and lattice arrangement. Vibrational spectroscopic techniques offer a non-destructive way to examine material structure, even in cases where the material is poorly crystalline. Fourier Transform Infrared (FTIR) spectroscopy, a type of vibrational spectroscopy, has been effective in identifying crystallinity differences in calcite by examining changes to the local (intra-unit cell) vibrational modes between samples of varying crystallinity [1, 2]. Combined studies involving X-ray diffraction showed that the vibrational peak changes are due to structural differences caused by lattice strain, microstrain fluctuations, and small crystalline domains while highlighting that FTIR alone was not able to distinguish the underlying cause [3]. Lower energy lattice vibrational modes (inter-unit cell) have yet to be studied in this way. This work examines changes in relative peak intensities of the lattice modes as a function of disorder and correlates these changes with local vibrational mode changes for the same samples. Our ultimate goal is to use these correlations to understand how lattice vibrational modes change with different types of structural disorder to bridge the knowledge gap between perfectly crystalline and amorphous materials.\
The effect of a sheared flow on magnetic islands in plasmas with non-axisymetric geometry
Cancino Escobar, Maria Stefany (Mexico)
The stability of a magnetic island in a toroidal magnetic confinement device depends on various factors besides the usual tearing-mode stability parameter Δ′ , determined by the local current profile.The presence of a sheared flow in the vicinity of the rational surface that supports the island is one of the factors that affects its stability since it can give rise to a polarization current around the island position. The contribution of the polarization current to the stability has been computed for a tokamak geometry. Here, we consider the case of magnetic islands with a shear flow in a stellarator which has a non- axisymmetric magnetic geometry. The main difference is a contribu- tion to the polarization current from the toroidal electrostatic oscil- lation. A correction due to the global toroidal magnetic geometry is also present. It is found that the regime where the stability is affected corresponds to the large island width relative to the ion gyroradius. Thus, the contribution is relevant for low-temperature regimes. In that case, the polarization current is destabilizing for frequencies larger than the ion diamagnetic frequency. Our results imply that the sheared flow can produce a growth of the magnetic island in a cold plasma but it can become narrower as the temperature rises.\
Differential Cross Sections for A <= 3 Nuclei in e’p Coincidence
Castellanos, Jonathan (United States)
The coincident e’p experiment (E12-14-011) for A ≤ 3 nuclei was performed at Jefferson Lab in Hall A to investigate Short-Range Correlations (SRC). SRCs are mainly due to the tensor force of the nucleon-nucleon (NN) interaction and dominate in the high missing momentum region above the nuclear fermi momentum as has been observed in electron nucleon knock out reaction data on nuclei heavier than A = 3. Preliminary first results of the analysis for deuterium, 3He and Tritium will be presented.
Hydrogen adsorption in MOF5: QLDFT calculations
Cerutti Torres, Joeluis (Cuba)
The study of the adsorption properties of nanomaterials, in particular their abilities to take in molecular hydrogen have attracted a lot of attention in recent years. In particular, the need for the design of efficient lightweight hydrogen storage devices have triggered a large number of theoretical and experimental investigations on the hydrogen uptake of a variety of nanostructured materials [1]. MOFs are nanoporous materials which constitute promising candidates for renewable energy applications, specifically for hydrogen storage [2]. Quantum liquid density functional theory (QL-DFT) [3] is a model that can be used for computing the density profile of guest species adsorbed in porous materials under the influence of an external potential at given thermodynamic conditions. QL-DFT translates the main equations of electronic DFT to a different problem, i.e., the problem of many interacting bosons at finite temperatures. Therefore, Bose Einstein (or Maxwell Boltzmann for high temperatures) instead of Fermi Dirac statistic is used. Also, electronic structure of MOFs and of the Hydrogen molecules are not taken into account explicitly, but they are masked in the guest-host interaction potentials. In this work, QL-DFT calculations are performed for the determination of the Hydrogen adsorbed density in MOF-5 (Fig.1), at varying thermodynamic conditions. Limitations and immediate perspectives for the modelling of adsorption phenomena in these media are also discussed.
Bucky-Si-Bucky sandwiched nanostructured composite anode with high capacity and cyclability
Chiluwal, Shailendra (United States)
Silicon anodes have been of great interest due to their higher theoretical capacity (4200 mAh/g) compared to traditional graphite electrodes (~372 mAh/g). Although Si has a higher capacity, its full potential has not yet been realized due to pulverization of Si anode upon lithiation. Conventionally, Si anodes are made by casting a slurry consisting of Si powder, conductive carbon additives, and a binder on a Cu foil. In such anodes, pulverization of Si particles leads to film delamination from Cu foil ensuing in battery failure. To overcome this challenge, we developed a new sandwich-structured anode by encapsulating ~100 nm Si nanoparticles in between two porous carbon nanotube buckypapers. The buckypaper is a conductive porous structure, which can incorporate active material better than Cu foil facilitating increased mass loading. More importantly, this sandwich-structured anode provides improved electrical contact even under repeated pulverization of Si nanoparticles leading to higher cyclability. We were able to achieve capacities as high as ~700-1200 mAh/g with a stable performance for >100 cycles.
Closing the Gender Gap in Engineering and Physics: The Role of High School Physics
Corrigan, Eamonn (Canada)
The past few decades have seen many advances towards gender parity in the fields of Science, Technology, Engineering, and Mathematics. But while biology, chemistry, and mathematics have all achieved >= 40% female enrollment in undergraduate programs, there remains a significant dearth of women in physics and engineering. Both disciplines have plateaued at ~20% female enrollment since the mid-nineties, despite a growing interest in education research, an increased focus on student engagement, and female mentorship programs. This talk will share data, recently obtained from the Ontario Ministry of Education, which clearly show that high school physics, not the university classroom, corresponds with the largest drop in student enrollment and interest. We will then explore the many factors which lead to this loss of talent and discuss a set of in class interventions designed to mitigate these effects.
Detecting a Second, Unknown Reactor with Antineutrinos for Mid-Field Nonproliferation Monitoring
Danielson, Daine (United States)
In reactor antineutrino monitoring, one must discriminate known background reactor fluxes from reactor signals under investigation. To quantify this discrimination, we find the confidence to reject the (null) hypothesis of a single proximal reactor, by exploiting directional antineutrino signals in the presence of a second, unknown reactor. In particular, we simulate the inverse beta decay (IBD) response of a detector filled with a 1 kT fiducial mass of Gadolinium doped liquid scintillator in mineral oil. We base the detector geometry on that of WATCHMAN, an upcoming antineutrino monitoring experiment soon to be deployed at the Boulby mine in the United Kingdom whose design and deployment will be detailed in a forthcoming white paper. From this simulation, we construct an analytical model of the IBD event distribution for the case of one 4 GWt ± 2% reactor 25 km away from the detector site, and for the case of an additional, unknown, 35 MWt reactor 3 to 5 km away. The effects of natural-background rejection cuts are approximated. Applying the model, we predict 3σ confidence to detect the presence of an unknown reactor within five weeks, for standoffs of 3 km or nearer. For more distant unknown reactor standoffs, the 3σ detection time increases significantly. The relative significance of directional sensitivity also increases, however, providing up to an eight week speedup to detect an unknown reactor at a 5 km standoff in the opposite direction from the known reactor.
An Environmental Test Stand for Large Area Testing of SiPMs for nEXO
Darroch, Lucas (Canada)
nEXO is a next generation time projection chamber searching for neutrinoless double-beta decay in 5 tonnes of liquid xenon enriched in the isotope Xe-136. Interactions within LXe produce anti-correlated scintillation and ionization signals, which will be used to reconstruct the energy and position of each event. Silicon photomultipliers (SiPMs) have been identified as the devices to detect the vacuum ultraviolet scintillation light for nEXO. SiPMs are silicon devices ~ 1 cm^2 with single photon sensitivity, and have a quantum efficiency of ~ 15% at 175 nm. A baseline characterization of the many SiPMs that will be distributed among the nEXO collaboration is necessary: the detector will employ tiles of SiPMs, organized into staves, yielding a photo-coverage area of ~ 4.5 m^2. The development of integrated SiPM tiles is advanced within the collaboration, requiring precise testing in conditions similar to their deployment. I will present on the status and plans of an environmental test stand for measuring ~ 150 cm^2 of SiPMs at 168K with quick turnaround between tile deployment, facilitating both a high-rate of baseline SiPM characterization, and precision testing of integrated tiles.
Dynamical tunneling in the quantum kicked top
Davis, Jack (Canada)
The quantum kicked top is a fundamental model used to study the emergence of classically chaotic behaviour in periodically driven systems arising from a quantum mechanical origin. Experimentally realized as a many-body ensemble of interacting qubits, the kicked top has allowed insight into how nonlinear features in the classical picture, such as a mixed phase space and bifurcation dynamics, influence underlying quantum characteristics including entanglement generation, tunneling, and thermalization. This work explores the strictly quantum mechanical phenomenon of dynamical tunnelling of spin coherent states between classically stable regions of phase space separated by a chaotic sea. Using analytical and numerical methods we explore the non-trivial relationship between the frequency of dynamical tunneling and the amount of chaos present, even in the deep quantum regime.
Maintenance and troubleshooting of the SNO+ detector
Depatie, Matthew (Canada)
The SNO+ neutrino detector, located 2km underground, is re-using much of original hardware from the Sudbury Neutrino Observatory (SNO). The 12m acrylic vessel (AV) is surrounded by approximately 9500 photomultiplier tubes (PMTs), high voltage and data readout electronics remain all the original hardware. Various improvements have been made to the triggering system, allowing the detector to readout the expected higher event rate for both the water and the liquid scintillator phases of the experiment. However, during the lifetime of SNO, a number of PMTs broke down requiring removal and repairs. The original electronics system was designed in 1995, using commercial parts for logic, memory and analog-to-digital conversions (ADCs) as well as some custom-built integrated circuits. Due to its age, continuous maintenance is required for stable operation. This presentation will cover these maintenance and repair efforts as well as discussing some unique problems and the troubleshooting required and show the success by the achievement of very high lifetime.
An Introduction to Density Functional Theory
Dumre, Bishal Babu (United States)
Density Functional Theory (DFT) is a simulation algorithm based on quantum mechanics which solves Schrodinger Wave Equation; Hφ=Eφ, where H is Hamiltonian, E is energy of the physical system of particles under consideration and φ is the wave function of the system. It is used to explain bulk properties such as crystal structure, hardness, absorptivity, reflectivity, band gap, etc. of any condensed material system using quantum information of its constituent atoms and molecules. As electrons are one of the major ingredients of any atom, they play a vital role in the determination of a particular property of any material. So, the properties of a many-electron system can be understood by using functionals, i.e. function of another function. In the case of solid, energy is the function of space dependent electron density that boils down a problem from 3N dimensions to 3 dimensions thereby reducing computational time where N is the no. of individual particles, i.e. electrons. Hence the name density functional theory comes from the use of functionals of the electron density.
Harnessing advanced classical computing techniques including distributed computing with tensor networks and machine learning for discovery in theoretical quantum physics
Edwards, Marcus (Canada)
In 1982, Feynman famously described the exponential scaling issue that is faced by any classical computing method that attempts to simulate a quantum system. This is not only a challenge for simulators, but also for theorists who study quantum many-body system dynamics. For example, exploring multi-qubit entanglement is important for a fundamental understanding of quantum mechanics as well as for building large scale quantum computers. A growing list of analogues between classical computing and quantum computing are being discovered in areas including machine learning [3, 4] and tensor networks [5]. We explore how distributed computing systems can be used to combine simulation approaches based on these analogues and enable more resource-optimized simulations. We contribute a framework for expressively implementing distributed quantum systems simulations in code. Our framework executes simulations using resources traditionally used for distributed cloud machine learning and data processing. We show how it can be used to analyze the performance of different simulation approaches and automatically suggest the best approaches to use for particular problems.
Morphokinematic Structure of the Planetary Nebula NGC 2346
Espinoza, Leonardo (Mexico)
We present a morphokinematic study of the Planetary Nebula (PN) NGC 2346 based on astronomical observations taken in the National Astronomical Observatory of Sierra de San Pedro Mártir (Mexico). Using the Manchester Echelle Spectrograph (MEZCAL) with the 2.1 m telescope, and a Hα+ [NII]λλ6548,6583 filter, we obtained and processed 15 different Position-Velocity maps. Combining the spectra with an HST image, and using the software SHAPE (Steffen et al. 2011, IEEE Trans. Vis. Comput. Graphics, 17, 454), we have reconstructed a 3D model of NGC 3242. We found that NGC 2346 is an opened bipolar shape of 0.76 pc with an apparent toroid in its center of 0.19 pc in diameter, inclined 20 degrees with respect to the plane of the sky (we used a distance of 1282 pc estimated from the GAIA data). The expansion velocity of the toroid is 11km/s, whereas the lobes expand at 23 km/s. The systemic velocity is VHEL=26km/s (VLSR=9 km/s). Finally, with all these data, we estimated the kinematics age of NGC 2346 as approximately 17,000 yrs. This work was supported by PAPIIT-DGAPA-UNAM IN107914.
WifiKID – Contact-free phonon detection in massive cryogenic absorbers
Germond, Richard (Canada)
Future rare event searches require detectors with large masses, low thresholds, and good energy resolution. Cryogenic semiconductor absorbers provide reasonably large target masses, but require a sensor to measure the energy deposited in a particle interaction. Kinetic inductance detectors (KIDs) are superconducting sensors that are mostly used for millimeter wavelength astronomy. Recently KIDs have gained interest in particle physics applications. The main advantage of KIDs is the ease with which they can be multiplexed in the frequency domain and read-out with a single cable. This work describes a novel read-out technique, in which a single KID on a large silicon absorber is inductively coupled to the feed-line (without any physical connection between the absorber and read-out line). This presentation showcases the design of the prototype device, and the measurement of the athermal phonon signal generated by particle interactions.
Disseminate contemporary science … For what?
Gomez Ortega, Marcos Ramón (Mexico)
Science is a fundamental tool for the advancement of humanity, but what is the perception of the general public towards science? This is the challenge we have as scientific disseminators, to build an increasingly better society, to change the perception that we have science, in Mexico we have this challenge and we are working from the youngest, that the future is formed by people with different ways of seeing science. Topics such as: particle physics, medicine and astronomy have concepts that we land on so that the public is interested and can identify their scope. We are clear that we all have contact with science and technology, but something is missing in the subconscious of people who have no interest in knowing how that technology reaches their hands, that is where the science disseminators act, to catch the individual to be able to changing your vision about science is what we want to achieve. In these years we have done a study on how scientific issues have an impact on the citizen if we present it to him in a different way, it is the key to be able to change the way of seeing science. We have identified that the apathy of the public towards science has to do with its understanding, the question is: Why do not you understand it? We are sure that something is failing in our educational system, science is being put aside and it is not important element in basic education, is where we have much to do, change the education system is another challenge, although this requires the support of the government and institutions that are dedicated to education. We are at CAM2019 because we want to share these experiences and how we can begin to change the way society perceives science.
Transport properties and thermoelectric effects in gated silicene superlattices
Guzmán Ortiz, Eric Jovani (Mexico)
Low-dimensional thermoelectricity opens the possibility of improving the performance and the efficiency of thermoelectric devices by redistributing the electron density of states through the reduction of dimensionality. In this work, we explore this possibility in silicene by reducing its dimensionality through the periodic arrangement of gated electrodes, the socalled gated silicene superlattices. Silicene electrons were described quantum relativistically. The transmission, conductance, and thermoelectric properties were obtained with the transfer matrix method, the Landauer-Büttiker formalism, and the Cutler-Mott formula, respectively. We find that the redistribution of the density of states together with the intrinsic characteristics of silicene, the local bandgap and the large spin-orbit coupling, contribute to the enhancement of the thermoelectric properties. In particular, the Seebeck coefficient and the power factor reach values of a few mV/K and nW/K2 . These findings in conjunction with the low thermal conductivity of silicene indicate that silicene-based nanostructures could be the basis of more efficient thermoelectric devices.
Point-Particle Catalysis
Hayman, Peter (Canada)
In certain situations, a heavy compact object can serve to catalyze otherwise forbidden low-energy processes. A particularly clean example in particle physics is the nucleus-induced neutrino-less conversion of muons into electrons, mu + N -> e + N (forbidden by kinematics in the absence of the nucleus). This process is possible but highly improbable in the Standard Model, so it can act as a very sensitive probe of new physics. While several new experiments search for evidence of this phenomenon, I will explore the theoretical side here and show how this type of reaction is naturally contained in the simplest point-particle effective field theory (PPEFT) for two species of light particle. A PPEFT exploits the hierarchy of scales between the size of a nucleus and the long wavelength of the interacting light particles to efficiently parameterize the influence of short-distance physics on low-energy observables. Concretely, I will show how scattering crosssections are simply controlled by a total of three length scales characteristic of the heavy compact object, which together contain all information about the high-energy physics involved, including any flavour-changing interactions. I will further note the connection between these length-scales and the various length-scales that characterize the influence of nuclei on atomic energy levels. Finally, I will briefly touch on how this relates to nuclei with internal degrees of freedom, and nuclear transfer reactions.
A Position-time Reconstruction Algorithm for SNO+
Hu, Jie (Canada)
SNO+ is a multi-purpose neutrino experiment aiming to study unknown properties of neutrinos. The main physics goal of SNO+ is to explore whether neutrinos are Majorana-type particles by searching for neutrinoless double beta decay of 130Te. The experiment is divided into three phases: the water phase, the scintillator phase and the tellurium-loaded scintillator phase. The detector was filled with ultrapure water and took water phase physics data from May 2017 to October 2018. It is currently being filled with liquid scintillator. A partially filled detector will be run for about two weeks for understanding the backgrounds of the liquid scintillator. The detector is planned to be fully filled for the scintillator phase by the end of this year. After the scintillator phase, 0.5% tellurium by mass will be loaded into the liquid scintillator. To analyze the SNO+ data, an event position-time reconstruction algorithm has been developed. This algorithm utilizes simplified photon path calculations and can be adjusted to different SNO+ phases. The algorithm has been tested with calibration data during the water phase as well as with Monte Carlos simulations for different phases. By testing the algorithm with 16N calibration source data in the water phase, a 30 cm position resolution is reached. Simulations of electron events in the scintillator phase show a 6 cm position resolution. The algorithm is also tuned for the partially filled detector and will be tested on the partial-fill phase data.
Radon Assay
Hussain, Syed Muhammad Adil (Canada)
The SNO+ experiment makes use of much of the detector hardware used for the previous SNO experiment, but uses scintillator as its main target. One of the main concerns for these rare event experiments is the presence of background, which could mask the signals of interest. This presentation will focus on Rn222, on of the most common backgrounds due to its excessive prevalence in the mine environment. Radon can interact in a similar way like neutrinos and cause the physics data to become obscure. The detector is housed in a large cavity that is filled with ultrapure water in order to avoid contamination. The Radon Assay is a technique that was developed for the SNO experiment to keep track of the radon content within the cavity to avoid any sources of contamination into the acrylic vessel. The Assay system itself has a very low background which makes the radon counting very reliable. Assays are performed biweekly at different positions of the cavity to keep frequent checks on the radon levels. During a radon assay, radon is trapped with a ZnS coated locus cell for a period of time and known amount of fluid flow. This lucas cell can then be connected to a PMTs, which detects the decayed alphas that are used to calculate the number of radon atoms in the cavity. This technique is a crucial part of measuring and monitoring the low background for the experiment and validate the authenticity of the results.
Propagation of E-M waves in stratified media described by an amplitude and phase approach
Jimenez Romero, Hector Alejandro (Mexico)
This talk is intended to show the utility of the amplitude and phase representation method in the analytical solving of electromagnetic wave propagation in stratified dielectric media. The strength of this treatment lies on the possibility of decoupling the Ermakov equations that arise in the study of this type of phenomena through the use of invariant quantities that posses a rich physical meaning. In addition to obtaining quantities such as reflectance and transmittance, a detailed description of the total electromagnetic field at each point of the space is also obtained. To illustrate the application of the proposed treatment a dielectric and homogeneous etalon of arbitrary thickness is studied in this terms. Analytical and numerical results are verified to be completely equivalent to those reported in the classic literature on the subject. As a next step, the central homogeneous medium in the etalon is replaced by a non homogeneous one, dependent on four parameters and that allows the modeling of different systems as well as the phenomena associated with discontinuities in the refractive index and its derivatives. Each of these results are compared with previously performed numerical studies, finding perfect matches.
A multimodal interferometry technique for detection and classification of tissue interfaces
Kaiyum, Rohith (Canada)
Advanced medical imaging modalities such as X-ray and Computed tomography (CT) are common in oral care however, X-ray lacks the temporal and spatial resolution needed for early diagnosis. While CT cannot be used in real time surgical treatment procedures. To provide an alternative to such hospital-restricted imaging methods, we introduce a high-resolution optical sensing technique into the patient care plan that will allow for the detection of pre-diseased, inflamed and aging tissue. Optical coherence tomography (OCT) is a non-invasive interferometry technique that allows measurement of the structural integrity and connectivity at the interfaces of soft and hard tissue to be examined as a pre-diagnostic biomarker of oral disease. Based on scattering and refractive index variances, an OCT is developed to identify and classify tissue interfaces, abnormalities at the micron scale, both lateral and axial spatial resolution. Our research seeks to classify various tissue interfaces though well-controlled tissue mimicking optical phantom studies and in vivo characterizations. The discrimination of optical scattering variances between different are being examined through OCT to assess efficacy in its ability to discern pathological lesions from healthy tissue in periodontal multilayer tissue interfaces. We look to compare these model systems with in vivo characterizations of bone structures through small layers of epithelial cells of the gum. In future investigations, we aim to incorporate near-infrared spectroscopic (NIRS) imaging, which allows for complimentary investigation into the microenvironment of oral tissue in situ by observing changes in oxy-/deoxy-hemoglobin absorption and local gradient of pH in inflamed tissues. We aim to spatially co-register data sets from both OCT and NIRS that can be mapped to assess structural-functional correlations of the target tissue and its biochemical microenvironment. Our multi-modal technique presents new opportunities with clinically amenable optical techniques for exploring structure-function relationships towards early detection of biomarkers linked to topical degenerative diseases.
Investigating the synergistic relationship between Aluminum and ionizing radiation using CGL1 and MCF10A cell lines
Kennedy, Konnor (Canada)
Aluminum is the third most plentiful metal in the earth’s crust and is commonly used in a variety of fashions in day to day life. It is found in anti-perspirants, cookware and drinking water. Miners were made to inhale aluminum powder in Northern Ontario in the past. Humans are also exposed to ionizing radiation occupationally in mining (radon daughter products) as well as through diagnostic imaging and radiation therapy procedures. The potential synergistic relationship between these two variables has been understudied in the past and would provide insight into public carcinogenic risk due to combined exposure from a molecular perspective. This study is to examine if there is an additive relationship between aluminum and ionizing radiation, and whether this union will produce findings suggestive of tumorigenic/carcinogenic changes between two different cell models. This study utilizes the CGL1 (HeLa x normal fibroblast) human hybrid cell line, a model system to examine neoplastic changes. The MCF10A cell line, a non-tumorigenic mammary epithelial line is also utilized. Aluminum Chloride (which is used in anti-perspirants) at a concentration of 300µM was added to cellular media. Cell proliferative assays on both lines were conducted (Aluminum vs Non-Aluminum) up to 8 days of exposure, followed by a survival (colonogenic) assay at radiation dosages of 0, 0.5, 1, 2, 4, 8 and 12 Gy respectively, with up to 30 days of aluminum exposure. DNA damage was quantified by means of γH2AX immunofluorescence, flow cytometry assays at radiation doses of 0, 1, 4 and 8 Gy up to 30 days of aluminum exposure at a variety of intermediate time-points. This study has shown that concentrations of 300µM of Aluminum Chloride did not significantly affect CGL1 cell survival curves, or the DNA DSB repair response. Cellular growth showed some subtle irregularities but were not significant. In the near future, gene expression will be evaluated with supporting qPCR assays on both cell lines. The MCF cell line will also be evaluated and quantified using the same methods as the CGL1 cell line.
SNO+ Calibration with the 16N Source
Khaghani, Pouya (Canada)
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 130Te loaded into the liquid scintillator. In addition, SNO+ aims to measure low energy solar neutrinos, reactor anti-neutrinos, geo-neutrinos as well as the neutrinos from a supernova event. The detector has been filled with ultra-pure water and been taking water data since May 2017 in preparation for the scintillator phase. During its water commissioning phase, SNO+ made accurate measurements of solar neutrinos above 5 MeV, and also performed an extensive search for invisible modes of nucleon decay with significant improvement over existing limits. Additionally, an extensive calibration has been performed using various deployed and embedded sources during the water phase. The primary calibration source in the water phase was the de-excitation of 16O from the decay of 16N. The 16N calibration data is used to tune the global efficiency of the detector, verify the energy and position reconstructions, and identify the systematics and position bias and resolution. The locally produced 16N gas is transported to the detector and injected into a suspended decay chamber all the while undergoing β decays. Decays within the source chamber are detected and tagged through a dedicated PMT and plastic scintillator enclosure. The 16O decay product is in excited state and emits 6.1 MeV γs that can easily penetrate through the container and make Cherenkov rings in water through Compton scattering. The source can be positioned along three axes using the side ropes system and the umbilical retrieval mechanism. This presentation will describe the 16N calibration system in detail, and furthermore discuss some of the calibration results and analysis.
Some changes in pigeon bone associated with the dietary intake of nickel recovery slag as a grit source
Lapointe, Michel (Canada)
Slag from nickel smelting operations in the Sudbury basin in Ontario has become ubiquitous. This material rich in heavy metals such as iron, upon ingestion has the potential to effect physical, radiological, chemical, mechanical, and structural changes in biological systems. In this work, we analyze the effects of slag ingestion through diet, on several quantitative and qualitative parameters of the tibio-tarsal bones in pigeons (Columba livia domestica). The specimens were divided into a control group provided a “normal” diet of clean limestone, and an experimental group fed slag-based grit, both for a period of one year. Their tibio-tarsal bones were then harvested for analysis. Quantitative analytical methods included measurement of caliper-based cortical bone thickness of the tibia, conventional density measurements, bone mineral density measurements using Dual Energy X-ray Absorptiometry, calcium and iron concentration measurements using mass spectrometry, and the determination of Young’s Moduli and ultimate breaking strength (both in compression) using a universal testing machine. A Welch’s t test (single tail) was used to compare means of the seven quantitative parameters between control and experimental samples, and in six parameters, a statistically significant difference was found (p ≤ .05). Microscopy, both optical and electron – coupled with energy dispersive spectroscopy (EDS) was also carried out for both sample groups. Microscopy and EDS analysis revealed structural differences in bone between the two groups. We conclude that slag ingestion through diet in the species examined, is associated with measurable changes in physical, radiological, mechanical, chemical, and structural properties of the tibio-tarsal bones.
Bubble Growth In Superheated C3F8 Bubble Chambers
Le Blanc, Alexandre (Canada)
Being able to distinguish an event from background is key in any rare event search experiment. PICO is a dark matter search experiment that utilizes bubble chambers and the acoustics of bubbles to discriminate events. This presentation will cover the work of my thesis and the potential for further research. I investigated the possibility of using the growth of a bubble as a discriminative tool amongst particles that can nucleate bubbles. Groups outside of particle physics have shown that temperature disturbances of varying magnitude affect the growth of a bubble. These temperature disturbances can be related to the energy that exceeds the nucleation threshold within the nucleation region. This can, in theory, be used to distinguish single bubbles caused by alpha particles and low energy nuclear recoils due to the differences in deposited energy. Unfortunately, the temperature disturbances alone do not reproduce the observed data from PICO. Nonetheless, the result obtained opens the possibility to energy deposition calorimetry if the early stage of the bubble’s growth can be observed.
Modeling evolution in a Long Time Evolution Experiment with E. Coli
Leon Valido, Dario Alejandro (Cuba)
We propose a model for the distribution of fitness effects (DFE) in the Long-Term Evolution Experiment (LTEE) with E. Coli bacteria. We designed an algorithm that makes use of the model in order to reproduce the evolutionary dynamics of the experiment. The algorithm enables us to simulate mutations under controlled conditions. The results of the simulations for the mean fitness and the mean number of mutations in clones are compared with the experimental data. Simulations allow us to study some phenomena such as fixation and drift, clonal interference, epistasis and phenotypic variability.
The spatially resolved properties of galactic winds: Characterization and modern techniques of study
Lopez-Coba, Carlos (Mexico)
The use of the new observation techniques in Astronomy, such as the Integral field spectroscopy has bring a new way of study the structural components of the Universe, in particular of the galaxies. The collective effect of Supernova explosions in the nucleus of galaxies, as well the nuclear activity of the supermasive black holes of galaxies, can produce galactic winds of kiloparsec scales that are realized to the interstellar medium or in the galactic halos. These galactic winds, or outflows, are phenomena that occurs in galaxies at different epochs of the universe. The effect of galactic winds over the host galaxies can determine the subsequent evolution of the host galaxies. In some cases, outflows can kill or paralyze the star formation of a hole galaxy due to the large amount of energy injected. In this talk I present the study and characterization of the outflows over a sample of > 1000 galaxies in the local Universe (redshift < 0.01). In this work I present a new methodology for searching outflows in normal star forming galaxies. We confirm that outflows are produced in the central regions of galaxies, particularly within a region of 1 effective radii. Clear Biconical structure of ionized gas outflows from the nuclear regions as well filamentary structures of gas produced by outflows are revealed with this technique. By using different spectrographs of higher spatial and spectral resolution, more detailed structures of the outflows are revealed. I will present how the spatial resolution affect the study and identification of outflows. The spatially resolved properties of these outflows are revealed upto scale of hundred of parsec. Different properties of the outflows, such as kinematic, ionization source, and mass released are presented. At the end I present the expected fraction of galaxies hosting outflows in the Local Universe.
VERITAS Observations of Fast Radio Bursts
Lundy, Matthew (Canada)
Fast radio bursts (FRBs) are energetic, structured, millisecond flashes of radio emission of extragalactic origin. The current source of these flashes is unknown, however, the high luminosity and short duration of these transients suggest a high-energy astrophysical process. Many theories predict simultaneous optical and gamma-ray emission from these systems on short timescales. VERITAS’s ability to simultaneously monitor both of these bands makes it an ideal instrument for the follow-up of these radio transients. Additionally, the recent expansion of the class of repeating FRBs has allowed for targeted follow-up. In this talk, we will present the current capabilities of the VERITAS FRB observing program as well as recent results.Oral Presentation
Shape Coexistence I Neutron Deficient Mercury Isotopes
MacLean, Andrew (Canada)
Neutron deficient nuclei near Z=82 exhibit one of the most extensive manifestations of shape coexistence across the nuclear chart. In the even-even mercury isotopes, 182−188Hg, Coulomb excitation experiments have provided a sensitive probe to determine the E2 matrix elements, giving information on the nature of the deformation for nuclear states. For transitions of J π → J π with J 6= 0, the determination of B(E2; Ji → Jf ) values also depend on the E2/M1 mixing ratios. One of the best methods to extract the mixing ratios is through γ − γ angular correlation measurements following EC/β decay where a very high sensitivity can be achieved. We have recently adopted this technique for the GRIFFIN γray spectrometer, located at the ISAC facility at TRIUMF, and have applied it to measurements of the EC/β decay of 188−200mTl to 188−200Hg. Included in this measurement was the PACES array, used for the detection of conversion electrons to determine E0 transition strengths. The extraction of E0 components of mixed transitions are of utmost importance as they may be enhanced if there are significant mixings between the shape-coexisting configurations. By combining measurements of mixing ratios, conversion electron intensities and lifetimes a direct measurement of the mixing between the shape coexisting structures can be made. Results on angular correlation measurements and E0 transition strengths for 188Hg will be presented.
Array of strain induced quantum dots in graphene
Mahmud, Md Tareq (United States)
Local Gaussian-shaped deformations induce strain fields that are represented by scalar and vector potentials in a continuum model description of electron dynamics in graphene. The ubiquitous strain changes the charge distribution in a very peculiar way, introducing a sublattice symmetry breaking, as has been reported in the literature. This feature can be exploited to design specific charge profiles by combining several deformations. Naturally, a combination of two or more is expected to introduce interference effects that can enhance charge accumulation in specific regions. We have investigated the effects of two overlapping deformations with different separations on the local density of states (LDOS). We showed that the overlap term can enhance the LDOS leading to stronger charge confinement in certain regions. Motivated by the work of Mason et. al (2018) we have extended these studies to a closed pack structure with a unit cell of 3 distinct deformations. This arrangement can be extended by symmetry to a lattice superstructure, thus creating a periodic array of confined charge regions, i.e, quantum dots. This array can be tailored by appropriately choosing the parameters of the deformations and their distances. The total charge distribution in these systems is similar to those observed in twisted bilayer systems, known as ‘Moire patterns’. We discuss optimal tuning of deformations to control the physical properties of these graphene devices.
Violation of an augmented set of Leggett-Garg inequalities using a non-invasive continuous in time velocity measurement
Majidy, Shayan (Canada)
Macroscopic realism (MR) is the view that a system may possess definite properties at any time independent of past or future measurements, and may be tested experimentally using the LeggettGarg inequalities (LGIs). In this work we advance the study of LGIs in two ways using experiments carried out on a nuclear magnetic resonance spectrometer. Firstly, we addresses the fact that the LGIs are only necessary conditions for MR but not sufficient ones. We implement a recently-proposed test of necessary and sufficient conditions for MR which consists of a combination of the original four three-time LGIs augmented with a set of twelve two-time LGIs. We explore different regimes in which the two- and three-time LGIs may each be satisfied or violated. Secondly, we implement a recent proposal for a measurement protocol which determines the temporal correlation functions in an approximately non-invasive manner. It employs a measurement of the velocity of a dichotomic variable Q, continuous in time, from which a possible sign change of Q may be determined in a single measurement of an ancilla coupled to the velocity. This protocol involves a significantly different set of assumptions to the traditional ideal negative measurement protocol and a comparison with the latter is carried out.
Development of an in-Xe-gas Laser Ablation ion source for the Ba-tagging technique for nEXO
Medina Peregrina, Melissa (Canada)
The new Enriched Xenon Observatory (nEXO) is an international collaboration searching for neutrinoless double beta (0νββ) decay in the isotope 136Xe. An observation of this event would imply lepton number violation and confirm that the neutrino is, its own antiparticle. The experiments plans to deploy 5 tonnes of enriched Xe-136 in a liquid-Xe time-projection chamber. nEXO is one of the most sensitive proposed 0νββ decay experiments with a projected half life sensitivity of close to 1028 years. In order to increase nEXO’s sensitivity and to verify a potential signal as double-beta decay events, the collaboration has been pursuing the development of a Ba-tagging technique in which it is possible to identify the 136Xe decay daughter, 136Ba. When a candidate 0νββ event is detected, the decay volume is searched for the presence of the Ba daughter. If a Ba atom is found, the event can be identified as a double beta decay of 136Xe and backgrounds that do not produce Ba, can be discarded. The nEXO collaboration is investigating different approaches to tackle the challenge of extracting and identifying single Ba+ ions produced in the detector from double beta decays. This technique is intended as a future upgrade to the detector once a successful tagging scheme has been demonstrated. In Canada, we are working on a method to extract ions from liquid Xe into a gaseous environment and subsequently into vacuum for final identification of the Ba ion. The group at McGill University is developing a laser ablation ion source to be operated in gaseous Xe. The source will provide large numbers of ions, to study and optimize the ion extraction process. The current status, the set up configuration, analysis of the laser transmission efficiency, spatial resolution measurements as well as future plans for this ion source, will be presented.
Superparamagnetic Fe304 Nanaoparticles and their potential for hyperthermia treatment for cancer
Meneses Brassea, Bianca Paola (United States)
The heating efficiency of Fe3O4 nanoparticles of different sizes synthesized using supercritical conditions of liquids, under different applied magnetic field intensities and frequencies, was investigated through experimental measurements of specific absorption rate (SAR). The synthesis conditions have been varied in order to obtain different sizes and shapes of Fe3O4 nanoparticles and to examine their effect on the SAR values. The morphology and crystal structure characterization of three samples revealed cubic-like shapes with average sizes of 63, 128, and 91 nm and formation of FCC Fe3O4 phase structure. The magnetic properties were characterized using magnetization dependent of magnetic field and temperature up to 3 T and 400 K respectively. The samples exhibit superparamagnetic-like behavior at room temperature with saturation magnetization Ms of 108, 74, and 77 emu/g and blocking temperatures TB of 320, 235, and 192 K, respectively. SAR values at 400 Oe and 304 kHz were measured using D5 hyperthermia system to be 126, 33, and 73 W/g for sizes of 63, 91, and 128 nm, respectively. The results yield efficient heating and the nanoparticles perfect feasibility for magnetic hyperthermia treatment of cancer.
Measurement of Electron Beam Polarization Through Tau Forward-Backward Polarization Asymmetry
Miller, Caleb (Canada)
Presently the Belle II experiment at SuperKEKB in Japan is colliding e +e − beams at ∼10GeV of energy. These beams currently have no spin polarization, but if SuperKEKB and Belle II were to be upgraded to make use of longitudinally polarized electron beams a significant number of electroweak precision measurements could be made. The use of polarized beams has been used in the past by the SLC to make the single most precise measurement of the weak mixing angle. Moreover, electroweak parameters have not been precisely measured at 10 GeV of energy before.This makes for a compelling case to implement a polarized beam at SuperKEKB. In addition to the technical difficulties in creating a polarized beam for collisions, it is difficult to know the exact amount of polarization that remains at the moment of collision. This uncertainty can become a leading systematic uncertainty limiting the precision of physics measurements. The beam polarization can be measured with sub-percent precision by making use of the relationship between beam polarization and the forward-backward asymmetry in the polarization of tau leptons produced in the e +e − collisions. By measuring the asymmetry, a precise value for the beam polarization at the e +e − interaction point can be determined. In this talk I will show results from applying this analysis method to KK Monte Carlo events and discuss the feasibility of applying the analysis technique as a measurement tool of beam polarization for a potential upgrade of polarized electron beams to SuperKEKB/Belle II.
Effective field theory analysis of the τ − → π −π 0ντ decays
Miranda Hernández, Jesús Alejandro (Mexico)
We perform an effective field theory analysis of the τ − → π −π 0ντ decays, that includes the most general interactions between Standard Model fields up to dimension six, assuming left-handed neutrinos. This approach corresponds to the low-energy limit of the SMEFT, which is the EFT of the SM in absence of New Physics up to few TeV. We constrain as much as possible the necessary Standard Model hadronic input using chiral symmetry, dispersion relations, data and asymptotic QCD properties. As a result, we set precise (competitive with low-energy and LHC measurements) bounds on (non-standard) charged current tensor interactions, finding a very small preference for their presence, according to Belle data. Belle-II near future measurements can thus be very useful in either confirming or further restricting new physics tensor current contributions to these decays.
Newton’s Second Something or Other
Norris, P James (United States)
Newton’s second law, “The change in an object’s momentum is equal to the net force acting on the object.”, cannot serve as a law because it does not allow one to make falsifiable predictions regarding the motion of an object under the influence of a non-zero net force. The ceteris paribus version of the statement commonly offered as Newton’s second law, “(If the object’s mass is constant, then) the net force on a body equals the body’s mass times its acceleration.”, is, in fact, our fundamental mechanism for quantifying an object’s mass. Thus, Newton’s second law is not a law.
Ground state properties of the Modulated XY chain in the Transverse magnetic field
Pandey, Toplal (Canada)
We present an exact theoretical study of the quantum phase transitions and symmetry breaking in the modulated spin -1/2 XY chain in transverse field. Energy spectrum and spontaneous magnetisations (mz) are briefly reviewed by using such standard analytical methods as Jordan Winger Transformation (JWT) and Bogoliubov transformation (BT). JWT and BT allow us to express local order parameters (LROs) and non-local order parameters (SOPs) in terms of Majorana string operators. We compute those parameters at zero temperature by treating them as Toeplitz matrices. We locate such non-vanishing order parameters in the different sectors of the phase diagram. The calculated LROs and SOPs demonstrate their quantitative accuracy and agree with the available analytical results for the model in some limiting cases. As a complementary description we calculate winding number which distinguishes the different phases.
A Neutrino Disappearance Search for Sterile Neutrinos with the CAPTAIN-Mills Detector at the Los Alamos Neutron Science Center
Rahman, Hasan Rejoanur (United States)
MiniBooNE (Mini Booster Neutrino Experiment) and LSND (Liquid Scintillator Neutrino Detector) have shown compelling evidence for sterile neutrinos at ∆m 2 ∼1 eV2 in short baseline neutrino oscillations experiments. In these experiments, a pure muon neutrino beam is used to search for electron neutrino appearance, i.e., νµ disappears in νe, but muon neutrino disappearance searches have shown no anomalies. The CAPTAIN-Mills experiment uses a 10-ton liquid argon scintillation detector to leverage the enhanced cross section from coherent elastic neutrino-nucleus scattering (CEνNS) to measure muon neutrino disappearance at the Lujan Center at the Los Alamos Neutron Science Center. Lujan is a 100-kW stopped pion source that nominally delivers a 290-ns wide, 800-MeV proton beam onto a tungsten target at 20 Hz, but the beam width can be significantly narrowed to 30 ns. Fast pulsing is critical for isolating the monoenergetic muon neutrino from the other neutrino flavors and neutron backgrounds. Description of the CAPTAINMills detector, the Lujan neutrino source, the expected sensitivities for sterile neutrinos will be presented along with the results obtained from the summer 2018 neutrino test run and a December engineering run.
Z’ and Higgs Boson Production Associated with a Top Quark Pair in the B-L Model at e+ e- Colliders
Ramírez Sánchez, Francisco (Mexico)
We study the production sensitivity of Higgs bosons ℎ and H, in relation to the possible existence of Z’ boson and a top quark pair at the energy scales that will be reached in the near future at projected e + e − linear colliders. We focus on the resonance and no-resonance effects of the annihilation processes e + e − → (γ, Z, Z’) → ttℎ, H. Furthermore, we develop and present novel analytical formulas to assess the total cross section involved in the production of Higgs bosons. We fnd that the possibility of performing precision measurements for the Higgs bosons ℎ and H and for the Z’ boson is very promising at future e + e − linear colliders.
Probing Emergent Excitations in Pr2Hf2O7 with Thermal Conductivity
Reid, Jennifer (Canada)
Pr2Hf2O7 (PHO) is a quantum spin ice candidate with a non-Kramers doublet ground state that displays evidence of dynamic spin ice behaviour [1][2]. We report thermal conductivity measurements of single crystal samples of PHO as a function of temperature between 50 mK and 50 K and magnetic field up to 12 T. A combination of high magnetic field measurements and measurements of different sized samples are used to identify the lattice contribution. We interpret our results considering current theoretical predictions for exotic excitations in quantum spin liquids, such as emergent photons, magnetic monopoles and visons [3].
SNO+ and Supernovae
Rigan, Michal (Canada)
SNO+ is an upgrade of the Nobel prize winning Sudbury Neutrino Observatory experiment. It is a kilo-tonne scale liquid scintillator detector that will study neutrinos. The detector consists of a 12 m diameter acrylic sphere that will be filled with approximately 800 tonnes of liquid scintillator which will float in a water bath. This volume is monitored by about 9728 photomultiplier tubes (PMTs), which are very sensitive light detectors. Liquid scintillator is an organic liquid that gives off light when charged particles pass through it. SNO+ will detect neutrinos when they interact with electrons and nuclei in the detector to produce charged particles which, in turn, create light as they pass through the scintillator. This flash of light is then detected by the PMT array. When a star undergoes a type II supernova explosion, more than 99% of its gravitational binding energy is released as neutrinos. The neutrino flux is so large, in fact, that even a supernova at galactic distances should produce a large number of events in SNO+. A measurement by SNO+ of the neutrino flux from a galactic supernova would yield extremely useful information about neutrino physics, stellar physics, cosmology, and more. The talk focuses on the available detection channels that could be used by SNO+ to detect a supernova, with expected number of events and details some of the plans for the Supernova burst trigger with the final goal of integration with the SNEWS collaboration.
Thermal Resistance Scaling of Silicon Phononic Crystals
Robillard, Alexander (Canada)
Phononic crystals are excellent candidates for the control of heat transport by lattice vibrations, in particular due to their tailored periodic structures. This control may come in the form of phononic band gaps or band flattening, and can lead to significant changes in transport coefficients. This behaviour makes silicon phononic crystals potentially excellent materials for thermoelectric applications. Phononic crystals have additional application potential in the fields of noise control, ultrasound imaging and telecommunication, among others. In this work, bottom-up designed phononic crystals made from silicon nanowires and nanoparticles are simulated using Reverse Non-Equilibrium Molecular Dynamics (RNEMD). The thermal resistances of phononic crystals with various lengths are calculated using the results of this method, and the length scaling of the resistance will be compared with those of nanowires with similar length and number of atoms. The suppression of thermal transport of the phononic crystals is shown to be significantly greater than that of even porous bulk silicon, indicating nanoscale effects in the phononic crystal. This is likely due to a reduction of ballistic transport in phononic crystals compared to equivalent scale silicon nanowires.
In-situ laser sensitization of ZnO nanorods for emerging solar cells
Rodríguez Martínez, Yerila (Cuba)
Since the inception of the development of emerging solar technologies, the application of simples and scalable techniques have been a challenge for their production and commercialization. The present work proposes an in-situ, low cost, easy to implement and scalable method with interesting applications for emerging solar cells. The technique, including a Nd:YAG pulsed laser, was used in previous work as energy source to activate a ZnO seed layer before the growth of ZnO nanorods (seeding process) [2]. In this case, applying the laser to ZnO nanorods previously submerged in an aqueous precursor solution, CdS nanoparticles were obtained covering the nanorods surface [3]. Different laser parameters like fluence and number of shots were changed and it was possible to obtain structures with different morphologies. In particular, SEM images shown a whole and in depth covering of ZnO nanorods with a highly homogeneous film of CdS nanoparticles for around 40 mJ/cm2 and 2 laser shots, and structures like CdS nanorods for laser fluence values around and higher than 60 mJ/cm2 . Passivation of characteristic surface defects in ZnO material after CdS growth, was also observed.
A Supernova Calibration Source for SNO+
Rumleskie, Janet (Canada)
Only one supernova neutrino burst has ever been detected, and the detection of additional neutrinos from galactic core-collapse supernovae are expected to provide insight on the supernova explosion mechanism. One candidate for detecting supernova neutrinos is SNO+, a multipurpose ultra-low background particle detector. Within SNO+, a galactic supernova neutrino burst is expected to generate an unprecedented rate. Thus, it is necessary to stress-test and optimize the SNO+ data acquisition and electronics so that a supernova signal can be reliably read out. For this purpose, a Supernova Calibration Source is under development to mimic the light expected from supernova neutrino interactions [1]. Using one-dimensional simulated supernova neutrino datasets [2, 3], light profiles representing neutrino interactions are calculated and realised using a laser diode light source delivered into the detector via fibre optics and a deployed light diffuser. Here I focus on the software conversion of neutrino datasets to light profiles, which define the light intensity and timing in the calibration source.
Preliminary Synthesis of Ruthenium Doped Oxyfluorides and Exploration of Polar and Magnetic Layered Oxides
Shah, Michael (United States)
Layered perovskites are structures of anionic perovskite blocks interleaved with metal cations and their rich chemistry makes them amenable to ion-exchange and exfoliation reactions. These perovskites and other layered oxides are materials used in diverse applications such as superconductors, semiconductors, ferroelectrics and photovoltaics. Late transition metal oxides are particularly interesting due to their correlated electronic properties and in the case of layered oxides they can be ion-exchanged and layered to create new structures. This study sought to create ruthenium-doped layered oxyfluoride perovskites due to ruthenium’s dn electrons which may give rise to metallic phases and can also be exfoliated. Likewise, the study sought to synthesize and explore other oxides which give rise to polar, optical and metallic properties. Samples were characterized using X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy to give information about phase and chemical compositions. Both ruthenium-doped perovskite and polar oxide samples were created via a solid-state route. Perovskite precursor phases were produced via a heating process and conditions for intercalation of RbF were optimized and could be intercalated with moderate success to form the layered structure. Phase pure samples of RbLaNb0.9Ru0.1TiO6F and Li7BiO6 were synthesized and explorations into the properties will be conducted.
Interpretation of the LHCb Pc(4312) signal
Silva Castro, Jorge Antonio (Mexico)
We study the nature of the new signal reported by LHCb in the J/ψ p spectrum. Based on the S-matrix principles, we perform a minimum-bias analysis of the underlying reaction amplitude, focusing on the analytic properties that can be related to the microscopic origin of the Pc(4312)+ peak. By exploring several amplitude parameterizations, we find evidence for the attractive effect of the Σ+ c D¯ 0 channel, that is not strong enough, however, to form a bound state.
Thermodynamics of Black Holes in de Sitter Spacetimes
Simovic, Fil (Canada)
Motivated by the inherent difficulties that arise when studying black holes thermodynamics in de Sitter spacetimes, we consider the embedding of such black holes in a finite radius isothermal cavity which acts as an equilibrating mechanism. We examine the phase structure of these black holes in the presence of both Maxwell and Born-Infeld gauge fields. In the presence of Maxwell fields, we find a novel pressure-dependent phase transition in a compact region of phase space that does not appear in asymptotically anti-de Sitter black holes. When the theory is extended to Born-Infeld fields, the non-linearities of the theory lead to the presence of reentrant phase transitions both in the canonical and grand canonical ensembles, whose existence and character are determined by the maximal electric field strength of the theory. We further demonstrate the presence of a new reentrant phase transition from radiation, to an intermediate size black hole, and back to radiation.
Investigating Excited State and Ground State Dynamics of Provitamin D analogs in DPPC lipid Bilayers
Sofferman, Danielle (United States)
Ultrafast photochemical transformations of 7-Dehydrocholesterol (DHC, Provitamin D3), DHC-Acetate and Ergosterol (Ergo, Provitamin D2) to previtamin D3, D3-acetate and D2 occurs upon a ring-opening reaction in the excited state where a cyclohexadiene (CHD) chromophore embedded within the molecules opens to form a hexatriene previtamin D species. The initial ring opening of isolated CHD in the excited state occurs on a sub-picosecond time scale, whereas conformer relaxation on the ground state happens on the time scale of picoseconds. In order to capture the dynamics of the molecule, ultrafast techniques such as transient absorption is used. Here we are studying excited state ring openings and ground state relaxation dynamics of DHC and its analogs in liposomes as a simple model for biologically relevant skin membranes. The excited state of DHC has been studied extensively in isotropic solvents where the molecule ring opens to form a previtamin D species with decay dynamics that are best modeled as a biexponential containing a fast 500fs and slow 1-2ps component. On the ground state conformer relaxation occurs within 6ps to form a stable previtamin D3 species. However, in the cell membrane the molecule is hypothesized to be locked in an unstable previtamin D3 conformation that thermally relaxes down to form Vitamin D3. When DHC is incorporated into the lipid bilayer, the longest time constant observed in solution is significantly slowed down to 11ps and 25ps in the excited and ground state respectively. To understand excited and ground state dynamics that takes place in biological membranes, we investigate structural influences such as hydrogen bonding and van der waals interactions between the molecule and its environment by extending our studies to incorporate DHC analogs, DHC-Acetate and Ergosterol into the bilayer and in isotropic solvents.
Integration and Evaluation of Coding in a First Year Integrated Physics and Calculus Courses
Steffler, Matt (Canada)
It has been recognized that computational skills are essential for the modern physicist, whether as a third “branch” of physics alongside experimental and theoretical, or as a toolset that is fundamental to the work of both theorists and experimentalists. In recognition of this, both the American Association of Physics Teachers and the American Physical Society have issued calls for computational instruction to be included at an appropriate level in undergraduate physics curricula. We selected two consecutive first year integrated physics and calculus courses aimed at physical science majors to create situations where students were learning physics and computing together. Python coding, via the Jupyter Notebooks system, was introduced in a carefully scaffolded system in several of the courses’ laboratory exercises, and was assigned to students in a Modeling Theory case-study assignment in each course. We analyze students’ coding proficiency, both perceived (through surveys and discussions) and actual (through coding achievement on the assignments) and evaluate whether students’ familiarity, comfort, and skill in computational physics have been elevated through these exposure.
Normal mode analysis of random-matrix spectral fluctuations
Torres Vargas, Gamaliel (Mexico)
Spectra of ordered eigenvalues of finite random matrices are studied as time series. In particular, by applying the singular value decomposition (SVD) to spectra of standard Gaussian ensembles from random-matrix theory (RMT), and also to nonstandard random-matrix ensembles such as the beta-Hermite ensemble and the sparse matrix ensemble, a decomposition of each spectrum, in trend and fluctuation normal modes (which can be considered as a generalization of the periodic modes in the Fourier analysis), is achieved. In this way, an unambiguous characterization of the spectral correlations, based on the behavior of the fluctuation modes, which can be scale invariant and follow a power law, or exhibit a crossover between those two limits, is obtained in a direct way without performing the technical step known as unfolding, avoiding the introduction of possible artifacts. Additionally, we perform a data-adaptive unfolding of the spectra in order to calculate traditional spectral fluctuation measures such as nearest-neighbor spacing distribution (NNSD), Σ2 , δ3 and δn statistics, and compare these results with those obtained previously. Finally, recent results obtained for random network spectra are presented.
KvN Mechanics for the time-dependent frequency harmonic oscillator
Urzua, Alejandro (Mexico)
The use of Koopman-von Neumann formulation of mechanics is a turnaround for solve problems where time dependence of parameters is explicitly given. Using Ermakov-Lewis invariants and the Operational Dynamical Modelling, we shown that dynamics from classical and quantum mechanical systems can be inferred, arriving at the conclusion that the mathematical structure governing is the same in both scenarios when a time-dependent frequency harmonic oscillator is analyzed.
Hydrogels films with CNTs for biosensing applications
Vilchis Leon, Paloma (Mexico)
Hydrogels have been probe to be an amazing material, we present and hydrogel that we formulated with a mix of carbopol 940 and PVA, the selection of this material is because they present a high level of compatibility with biological enviroment. Multiwalled CNT that we obtained from Nanotechnology Lab of the Iberoamericana University, after the functionalization of the CNT, were mixed with the Carbopol and PVA Solution to obtained a film of Hydrogel with CNT. For the characterization, we use Raman Spectroscopy, determine %Swelling. The purpose of this method is utilized the film as a biosensor for bacteria detection or as a drug delivery devices. Also, we could introduce this film in a microfluidic device to probe that can be use a biosensor.
Dynamics, structure and self-assembly of colloidal mixtures
Villanueva-Valencia, Jose Ramon (Mexico)
1) First, the physical properties of multicomponent anisotropic colloidal dispersions are still far from being fully understood. This is mainly due to the fact that dealing with nonspherical particles and highly directional interactions is, from both experimental and theoretical points of view, a complicated task. Then, we will show an experimental and computer simulation study on the hydrodynamic correlations among colloidal particles. We are interested in the short- and long-time dynamics in anisotropic colloidal mixtures under confinement by parallel glass walls. 2) Second, the drug delivery through therapeutic monoclonal (mAb) antibodies in the bloodstream represents a challenge task because these macromolecules deal with capillarity and with an increase in the viscosity due to the particle aggregation by means of the active sites of mAb. This is a problem of interest in the pharmaceutical industry and such phenomenon can be understood through the internal (amino acid) dynamics inside the protein and how it contributes to the global dynamics of them. 3) Third, the Critical Casimir force (CCF) is a long-ranged interaction between colloidal particles dispersed in binary solvent which is generated when the solvent is close to its demixing temperature. Since many years ago, it has been shown that this solvent mediated interaction can lead to particle flocculation. Furthermore, recently it has been demonstrated that this critical density fluctuation is particle size-sensitive, and thus it can be used as an efficient way to purify nanoparticles by sizes for small nanoparticles. We then investigate the effects of size and concentration on this particle size separation method, which has become a route to generate new materials with specific optical, mechanical and thermodynamical properties.
Acid/Base Extraction of Tellurium from SNO+ Scintillator
Walton, Stephanie (Canada)
SNO+ is a kilo-tonne scale detector used to study neutrinos. The detector volume is currently filled with Ultra Pure Water (UPW) contained in a 12 meter diameter acrylic sphere, which will soon be replaced with Tellurium (Te) loaded liquid scintillator. The detector volume is viewed by approximately 9500 photomulitpiler tubes (PMTs) to monitor scintillator events. Scintillator is being purified in the SNOLAB underground facilities to replace the UPW. The required plants to produce the tellurium isotope that will be loaded into the scintillator are under commissioning and expected to be ready by the end of the year. Additional processing will be required at the end of the experiment to remove the tellurium from the scintillator as it is drained from the acrylic sphere. The tellurium extraction must be done in a way that is both effective and possible given the underground conditions. Benchtop testing and optimization of the removal process is ongoing and will be discussed in the presentation after a short introduction to the experiment and tellurium processes.
The effect of chemically and thermally Reduced Graphene Oxide on the electronic conductivity of LiFePO4 composites
Yasharahla, Sharah (United States)
Research has shown that adding reduced graphene oxide(RGO) to Lithium Iron Phosphate(LFP) batteries can improve conductivity and performance. This improvement has been demonstrated with LFP/RGO composites delivering an initial discharge capacity of 158mAhg-1 at 0.1C, which is comparable to pristine LFP capacity of 170 mAhg-1. Our research is focused on exploring the addition of low weight percentages (2 – 8wt%) of reduced graphene oxide to LFP cathodes. Initial results for discharge capacity show slightly larger specific capacity in batteries where 4wt% of reduced graphene oxide is added to LFP cathode material. In contrast, batteries with 2wt% of graphene added to the LFP cathode material had similar specific capacities in comparison with batteries made with pristine cathode material. Initial conductivity values show a substantial increase from 10^(-2) to 10^(5) S/cm