PHYS PHEST 2022

Event Schedule

Lunch

12:10 - 1:10 pm Pizza Lunch

Presentations

(Each presentation is 12 minutes, plus 3 minutes for questions)
1:10 Opening Remarks – Eric Poisson
1:15 Zarin Ahmed
1:30 Yasmeen El-Rayyes
1:45 Benjamin Morling
2:00 Sangeet-Pal Pannu
2:15 Marie Pinto
2:30 Nicholas Van Heijst (PhD)
2:45 Closing remarks – Eric Poisson
5:00 CORN ROAST – Riverside Park PHYS PHEST winners announced!

Abstracts

Development work for The Detector Array for Energy Measurement of Neutrons (DAEMON)
Zarin Ahmed, MSc Candidate
Advisor: Paul Garrett

As one moves away from stable isotopes and deeper into the neutron-rich region, the likelihood of \(\beta \)-delayed neutron (\(\beta n\)) emission decay increases. The ability to understand the neutron emission probabilities and the neutron energy spectrum can reveal highly sensitive detail of the nuclear structure that a conventional \(\beta \)-decay study using only \(\gamma\)-ray detection cannot. We propose to build the Detector Array for Energy Measurements of Neutrons (DAEMON) that will employ the time-of-flight technique to enable high-resolution energy measurements of the neutrons emitted following \(\beta n\) emission. The initial trials testing the rudimentary geometries of EJ200 plastic scintillators and various electronic parameters of silicon photomultiplier (SiPM) arrays for the foundation of DAEMON will be presented. Upon successful comparison of tests with gamma sources with simulations data, the DAEMON prototype will be tested with the monoenergetic neutron beam at the University of Kentucky Accelerator Laboratory. Used in conjunction with the GRIFFIN Decay Station at TRIUMF in Vancouver, BC, DAEMON will establish a frontier for \(\beta n\) studies currently non-existent at the facility and therefore initiating a road to strong international collaborations. From shaping the abundance curve of the astrophysical rapid neutron capture process, as well as controlling the neutron induced fission in nuclear reactions, the building of a neutron detector will address a broad arena of physics.

Changes to the Stiffness and Compressibility of Soft Phytoglycogen Nanoparticles Through Acid Hydrolysis
Yasmeen El-Rayyes, MSc Candidate
Advisor: John Dutcher

Phytoglycogen (PG) is a glucose-based polymer that is naturally produced by sweet corn in the form of compact nanoparticles with an underlying dendritic architecture. Their deformability and porous structure combined with their non-toxicity and digestibility make them ideal for applications in personal care, nutrition, and biomedicine. PG nanoparticles can be modified using chemical procedures such as acid hydrolysis, which reduces both the size and density of the particles. We used atomic force microscopy (AFM) force spectroscopy to collect high resolution maps of the Young’s modulus E of acid hydrolyzed PG nanoparticles in water, and we compared these results to those obtained on native PG nanoparticles. Acid hydrolysis produced distinctive changes to the particle morphology and significant decreases in E. These measurements highlight the tunability of the physical properties of PG nanoparticles using simple chemical modifications.

Dynamical Self-Consistent Field Theory Simulation of Phytoglycogen Nanoparticles
Benjamin Morling, MSc Candidate
Advisors: John Dutcher, Robert Wickham

Phytoglycogen (PG) is a naturally occurring, highly branched, glucose dendrimer that is extracted from sweet corn as soft, compact nanoparticles. We use dynamical self-consistent field theory (dSCFT) to simulate the dynamical evolution of a PG nanoparticle solubilized in water. We evolve the 11-generation dendrimer using an efficient, stable operator decomposition of the dendrimer into its branches. By varying the strength of the interactions between the PG nanoparticle and water, we are able to tune the size and the degree of hydration of the nanoparticle to be in agreement with the values measured using small angle neutron scattering (SANS). We show that our model is capable of reproducing the unique 'hairy' morphology of PG nanoparticles as inferred from rheology, SANS, and atomic force microscopy measurements.

Analysis of Low Energy Spin States of 100Ru via Angular Correlations
Sangeet-Pal Pannu, MSc Candidate
Advisor: Paul Garrett

A recent nuclear structure investigation has outlined that a set of long-established spherical-vibrational nuclei fails to meet their guidelines as spherical vibrators and, instead, they may present a previously considered extremely rare nuclear phenomenon, the so-called shape coexistence. The Ru isotopes (98Ru and 100Ru) are the last remaining spherical vibrator candidates, but studies hint at the failing of the vibrator requirements also in this case. No conclusion, however, has been made due to their many low-spin levels being poorly characterized. These states are crucial to elucidating the shape-coexistence vs. vibrational nature. To uncover the true nature of the 100Ru structure, a 99Ru(n, gamma)100Ru reaction using a detector setup from the Institut Laue-Langevin in Grenoble, France, was completed in 2021. Using this dataset, the low-level spin characterization will be cleared up by implementing the experimental technique of gamma-gamma angular correlations to provide definitive spin assignments. This experimental technique is routinely exploited by the Canadian nuclear-structure collaboration for a singular kind of gamma-ray detector. However, the ILL facility's detector configuration houses two different kinds of gamma-ray detectors, making the method not implicitly applicable. The goal of my master's is to implement the gamma-gamma angular-correlation analysis for the ILL data and characterize the low-level spin assignments to clarify the nature of the 100Ru isotope.

Biosynthetic production of isotopically labeled retinal in Eschericia coli and reconstitution into microbial rhodopsins for biophysical analysis
Mario Pinto, MSc Candidate
Advisor: Leonid Brown

Microbial rhodopsins are light-sensing proteins which serve as tools for optogenetics. Optogenetics integrates these proteins into animal tissues to generate a biological response upon exposure to light. To apply microbial rhodopsins to optogenetics, their atomic structure and functions must be well understood. In the core of rhodopsins there is a chromophore binding site which contains retinal. Retinal is a Vitamin A aldehyde and 20-carbon chromophore which undergoes isomerization when exposed to light. The isomerization of retinal influences steric changes in the rhodopsin and helical shifts which lead to activation of the protein. Using E. coli transformed with the DNA for retinal precursors, β-carotene and β-carotene dioxygenase, retinal can be biosynthetically grown in a minimal media and extracted using an organic solvent, n-octane, by hydrophobic separation. This procedure is effective at producing 0.22 mg of retinal per litre of media, a significant improvement on the previously produced 0.1 mg. Using this protocol, I aim to develop retinal uniformly labeled with isotopic 13C which is required for investigation by advanced spectroscopic techniques, such as nuclear magnetic resonance (NMR) spectroscopy. Incorporating this retinal into novel microbial rhodopsins allows us to determine the structure of retinal and measure distances in and around the chromophore binding site. This information is important as it provides specific atomic data on how retinal’s isomerization influences the steric changes which occur in the helices of the rhodopsins and ultimately result in initiation of the rhodopsin’s biological function.

Improving the Water Solubility of Hydrophobic Compounds Using Phytoglycogen Nanoparticles
Nicholas van Heijst, PhD Candidate
Advisor: John Dutcher

In the pharmaceutical field, many newly synthesized drug formulations suffer from poor water solubility which hinders their bioavailability for applications within the human body. Developing technologies to improve their solubility and bioavailability is therefore a major challenge for the industry. In recent years, nanotechnology has been proposed as a potential solution. Phytoglycogen (PG) is a compact, highly branched polysaccharide nanoparticle which is extracted from the kernels of sweet corn. Importantly, PG is naturally occurring, non-toxic and even digestible, which makes it ideally suited for applications in human health and nutrition. Recently, we have developed a technique to use PG as a solubilizing agent for two physiologically relevant, hydrophobic carotenoids: astaxanthin (ASX) and \(\beta\)-carotene (\(\beta\)C). Preliminary results demonstrate that formulations of these compounds with PG can be easily dispersed in water with the aqueous dispersions stable for long periods of time. We use techniques such as Ultra-Violet visible spectroscopy (UV-vis), Dynamic Light Scattering (DLS), Surface Plasmon Resonance imaging (SPRi) and Nuclear Magnetic Resonance (NMR) to explore the nature of the PG-ASX and PG-\(\beta\)C interactions. Remarkably, we find that the solubility of ASX can be enhanced by a factor of 107 through association with PG, demonstrating that PG is a safe and effective solubilizing agent for insoluble carotenoids.