Contents
Acknowledgements3
Keynote Speaker4 Title ...... 4 Abstract ...... 4 Biography ...... 5
Timetable6 Tuesday, July 21st ...... 6 Wednesday, July 22nd ...... 7
List of Abstracts – Talks8 Tuesday ...... 8 Oral Session 1 ...... 8 Oral Session 2 ...... 8 Wednesday ...... 9 Oral Session 3 ...... 9 Oral Session 4 ...... 9
List of Abstracts – Posters 29 Wednesday ...... 29 Poster Session 1 ...... 29 Poster Session 2 ...... 31
2 Acknowledgements
The Oak Ridge Postdoctoral Association (ORPA) and research committee would like to thank lab leadership, all volunteers, administrative assistants, Information Technology Services Division, and the ORNL community as a whole for their continued support of our annual Research Symposium. This event would not be possible without your continued commitment!
We are honored to have Dr. Tresa M. Pollock this year’s keynote speaker.
Our special thanks go to Moody Altamimi and Lynn Kszos for their guidance and support for the Postdoctoral Program and ORPA over this past year. We would further like to thank Dionne Harper, Laurie Varma, and Cydne Albers for their contribution to the success of this event.
Organizing Committee
Moody Altamimi Anne Berres Gemechis Degaga Lu Han Sara Isbill Syed Islam Lynn Kszos Phil Lotshaw Claire Marvinney Peter Mouche Marie Romendenne Tyler Spano Miguel Toro-Gonzalez
ORPEX20 (left to right): Sara Isbill, Tyler Spano, Miguel Toro-Gonzalez, Natasha Ghezawi, Gemechis Degaga, Lu Han, James Kammert, Lynn Kszos, Peter Mouche, Syed Islam, Claire Marvinney
3 Keynote Speaker
Tresa M. Pollock, Ph.D. Materials Department University of California Santa Barbara
Title
Development of the TriBeam Tomography Platform and Acquisition of Multimodal 3D Materials Data
Abstract
The development of high fidelity material property and life prediction models often requires three-dimensional information on the distribution of phases, interfaces, grains or extrinsic defects. Such high-resolution chemical, crystallographic and morphological data requires multiple detectors and presents unique image and data challenges. The development of the TriBeam platform to gather multimodal materials data will be described. An overview of the ceramic, metallic and composite material datasets gathered to date will be given. New insights gained from the 3D datasets on structure development during additive manufacturing, crack initiation during fatigue and shock loading of polycrystalline alloys will be given. Finally, the challenges for integrating experimental voxelized data with models for prediction of mechanical properties will be addressed.
4 Biography
Tresa Pollock is the Alcoa Distinguished Professor of Materials and Associate Dean of Engineering at the University of Cali- fornia, Santa Barbara. Pollock’s research focuses on the mechanical and environmen- tal performance of materials in extreme environments, unique high temperature ma- terials processing paths, ultrafast laser- material interactions, alloy design and 3-D materials characterization. Pollock gradu- ated with a B.S. from Purdue University in 1984, and a Ph.D. from MIT in 1989. She Tresa Pollock, Ph.D. was employed at General Electric Aircraft Engines from 1989 to 1991, where she con- ducted research and development on high temperature alloys for aircraft turbine engines and co-developed the single crystal alloy Ren (now in service). Pollock was a professor in the Department of Materials Science and Engineering at Carnegie Mellon University from 1991 to 1999 and the University of Michigan from 2000 - 2010. Her recent research has focused on development of new femtosecond laser-aided 3-D tomography techniques, damage detection and modeling by resonant ultrasound spectroscopy, thermal barrier coatings systems, new intermetallic-containing cobalt-base materials, nickel base alloys for turbine engines, lightweight magnesium alloys, Heusler-based thermoelectrics and bulk nanolaminates. Professor Pollock was elected to the U.S. National Academy of Engineering in 2005, the German Academy of Sciences Leopoldina in 2015, and is a DOD Vannevar Bush Fellow and Fellow of TMS and ASM International. She serves as Editor in Chief of the Metallurgical and Materials Transactions family of journals and was the 2005-2006 President of The Minerals, Metals and Materials Society.
5 Timetable
WR: Welcome Remarks, KS: Keynote Speaker, OS: Oral Session PS: Poster Session, CR:Closing Remarks
Tuesday, July 21st
Event Sara Isbill, [email protected]; Miguel Toro Gonzalez, [email protected] contact Location Online via Teams (oral presentations and keynote) and iSeeVC (posters) Dr. Michelle Buchanan, 12:45–1:00 Welcome Remarks and WR ORNL Deputy for Science and pm Speaker Introduction Technology 1:00–2:00 KS Keynote Speaker Dr. Tressa Pollock pm 2:00–2:10 Break pm Jiadeng Zhu, Syed Z. Islam, 2:10–3:20 Xiangru Kong, Sudhajit Misra, OS Oral Session 1 pm Hanns Gietl, Richard Michi, Matthew Hall 3:20–3:30 Break pm Kubra Yeter Aydeniz, Caroline 3:30–4:40 Gorham, Byungkwon Park, Bill Kay, OS Oral Session 2 pm Paul Eller, Justin Gage Lietz, Shilpa Marti
6 WR: Welcome Remarks, KS: Keynote Speaker, OS: Oral Session PS: Poster Session, CR:Closing Remarks
Wednesday, July 22nd
Event Sara Isbill, [email protected]; Miguel Toro Gonzalez, [email protected] contact Location Online via Teams (oral presentations and keynote) and iSeeVC (posters) 10:00–11:30 PS Poster Session 1 Presenters am 11:30–12:15 Lunch Break pm 12:15–1:45 PS Poster Session 2 Presenters pm 1:45–2:00 Break / switch from iSeeVC to Teams pm Sudarshan Srinivasan, Devon Drey, 2:00–3:10 Alex Chien, Daniel Kneller, Bo OS Oral Session 3 pm Jiang, Peng Shuai, Ashleigh Kimberlin 3:10–3:20 Break pm Gemechis Degaga, Nicholas Dove, 3:20–4:20 OS Oral Session 4 Erin Creel, Debasis Banik, pm Elizabeth Neumann, Michelle Pitts Dr. Moody Altamimi, 4:20–4:30 CR Closing Remarks Director, Office of Research pm Excellence
7 List of Abstracts – Talks
Tuesday
>>Timetable
Oral Session 1
Time Presenter Title 2:10-2:20 Jiadeng Zhu Advanced Fibers Enabled Better Batteries for Next-Generation Elec- tric Vehicles 2:20-2:30 Syed Islam Separation and Recovery of Critical Materials from Electronic Waste 2:30-2:40 Xiangru Kong Light-induced chiral edge states in two-dimensional stable ferromag- netic semiconductors 2:40-2:50 Sudhajit Misra Back-surface Etching Leads to Efficiency Limiting Detrimental Effects in Cadmium Telluride Thin Film Solar Cells 2:50-3:00 Hanns Gietl Tungsten based refractory material composite for fusion applications - theoretical evaluation 3:00-3:10 Richard Michi Advances in the Development of Cast and Additively Manufactured High-temperature Aluminum Alloys 3:10-3:20 Matthew Hall Development of SOLSTISE: A Supersonic Gas Jet Target for Solenoidal Spectrometers
Oral Session 2
Time Presenter Title 3:30-3:40 Kubra Aydeniz Scattering in the Ising Model Using Quantum Lanczos Algorithm 3:40-3:50 Caroline Gorham Topological-Order in Condensed Matter (Complex & Quaternion Symmetries): A Novel Perspective on Frustrated Crystals & Glassy Dynamics & the ’Ideal Glass Transition’ as a 1st Order Critical Point 3:50-4:00 Byungkwon Park Examination of Semi-Analytical Solution Methods in the Coarse Operator of Parareal Algorithm for Power System Simulation 4:00-4:10 Bill Kay Neuromorphic Computing and Graph Algorithms 4:10-4:20 Paul Eller Scalable Non-blocking Krylov Solvers for Extreme-scale Computing 4:20-4:30 Justin Lietz NTCL: A GPU Accelerated Tensor Contraction Library for Nuclear Physics 4:30-4:40 Shilpa Marti Evaluation platform for sub modules in MMC systems through Power Electronics Hardware-in-the-loop (PE-HIL)
8 Wednesday
>>Timetable Oral Session 3
Time Presenter Title 2:10-2:20 Sudarshan Srinivasan COVID-19 Fake Text Generation 2:20-2:30 Devon Drey Investigation of Disorder in Ho2T i2−x Zrx O7: Pyrochlore to Defec- tive Fluorite Chemical Series 2:30-2:40 Alex Chien Fast ion conduction induced by anion disorder in Li-deficient Argy- rodite 2:40-2:50 Daniel Kneller Room temperature X-ray crystallography of SARS-CoV-2 Main Protease unveils structural plasticity of the active site cavity and reactivity of the catalytic cysteine 2:50-3:00 Bo Jiang Modeling of local atomic structure in disordered and nanostructured materials 3:00-3:10 Peng Shuai Determination of Ground State Feedings in β-decay using Modular Total Absorption Spectrometer 3:10-3:20 Ashleigh Kimberlin Progress in n.c.a. Lu-177 Production at ORNL
Oral Session 4
Time Presenter Title 3:20-3:30 Gemechis Degaga Deep Learning Generative Method for Engineering New Proteins 3:30-3:40 Nicholas Dove Ecological and genomic responses of soil and plant microbiomes to wildfire: linking fundamental community assembly processes to soil quality and plant health 3:40-3:50 Erin Creel Roll-to-Roll Slot-Die Coating of Concentrated Electrocatalyst Layer Inks for PEM Fuel Cells 3:50-4:00 Debasis Banik Mechanobiology of T cell receptors and chimeric antigen receptors: a head-to-head comparison study 4:00-4:10 Elizabeth Neumann Deciphering Host Immune Responses to Staphylococcus aureus Infection by Combining Imaging Mass Spectrometry and CODEX Multiplexed Immunofluorescence 4:10-4:20 Michelle Pitts Autoantibody responses to apolipoprotein A-I are not diet or sex- linked in C57BL/6 mice
9 Tuesday
Oral Session 1
Advanced Fibers Enabled Better Batteries for Next-Generation Elec- tric Vehicles
J. Zhu
ORNL
Due to the continuously increasing demand for world energy consumption, the general goal for rechargeable battery development is to increase the energy densities. Among various candidates, lithium-sulfur (Li-S) battery is a promising one in this regard not only because both sulfur and lithium have high theoretical capacities but sulfur is low cost and environmentally friendly. Moreover, lithium metal has a low negative potential. Nevertheless, the commercialization of Li-S batteries has been hindered by several issues, such as the insulating nature of sulfur and its intermediates, polysulfide shuttle effects, safety concerns of the lithium metal electrode, etc. Intensive efforts have been taken to solve these problems by developing novel sulfur host materials, solid-state electrolytes, advanced separators and interlayers, and binders, etc., during the past decade. It should be noted that fibrous materials have played extremely important roles in the abovementioned solutions due to their substantial surface-to-volume ratio, flexibility in surface functionalities, large porosity, and good mechanical properties. In this presentation, how to design and synthesize integrated architecture based on those novel fibrous materials to achieve high-performance Li-S batteries will be discussed in detail: from the traditional liquid system to full solid-state cells.
Separation and Recovery of Critical Materials from Electronic Waste
S. Islam
ORNL
In recent years, rare earth elements (REEs) such as Nd, Pr, and Dy have drawn tremendous attention due to their substantially increasing use in the form of permanent magnets in hybrid and electric vehicles, wind turbines, mobile phones, tablets, personal computers, and a wide range of devices with electric motors. To provide a domestic source for REEs, we have developed a supported membrane solvent extraction (MSX) process for the recovery of REEs from scrap permanent magnets. The separation results show that the REE recovery of >97% with a purity of >99.5 wt.% can be achieved from a wide range of high-volume scrap magnet feedstocks. The results demonstrated that MSX is a robust, scalable, economically viable and sustainable, and environmentally friendly process for the recovery of REEs from various types of scrap magnet sources.
10 Light-induced chiral edge states in two-dimensional stable ferromag- netic semiconductors
X. Kong
ORNL
Topological materials are fertile ground for investigating topological phases of matter and topo- logical phase transitions. In particular, the quest for novel topological phases in 2D materials is attracting fast growing attention. Here, using Floquet-Bloch theory, we propose to realize chiral topological phases in 2D hexagonal F eX2(X = Cl, Br, I) monolayers under irradiation of circularly polarized light. Such 2D F eX2 monolayers are predicted to be dynamical stable, and exhibit both ferromagnetic and semiconducting properties. To capture the full topological physics of the magnetic semiconductor under periodic driving, we adopt ab initio Wannier-based tight-binding methods for the Floquet-Bloch bands, with the light-induced band gap closings and openings being obtained as the light field strength increases. Interestingly, the topological transitions with branches of chiral edge states changing from zero to one and from one to two by tuning the light amplitude are obtained, showing that the topological Floquet phase of high Chern number can be induced in the present Floquet-Bloch systems.
Back-surface Etching Leads to Efficiency Limiting Detrimental Ef- fects in Cadmium Telluride Thin Film Solar Cells
S. Misra
ORNL
Cadmium telluride (CdTe) has emerged as a leading thin-film photovoltaic (TFPV) technology, with manufacturing cost being cheaper than silicon. However, CdTe TFPV has much scope for improvement with record device efficiency (22.1%) lagging far from its theoretical efficiency (>30%). Grain boundaries (GBs) are the most prominent structural defects in these thin-films and undergo significant changes during device fabrication. Traditionally, bromine-etching is used to create an ohmic contact with CdTe after chlorine passivation of these GBs. The current understanding of these effects considers individual GBs to be homogeneous in their properties. Using electron energy loss spectroscopy (EELS), we show that the back-surface etching of CdTe leads to inhomogeneity within the GBs and reverses the passivating effect of chlorine treatment. After etching, elemental Te is observed as deep as 1µm from the back-surface of CdTe. Additionally, two-dimensional device simulations of this effect show that, contrary to current understanding, back-surface etching leads to additional carrier recombination within the CdTe layer. This leads to losses in open-circuit voltage and limits device efficiency. Instead, depositing a Te or ZnTe layer at the back-surface of CdTe preserves the GB stoichiometry. Therefore, avoiding chemical etching processes is a better pathway towards achieving higher efficiency for next-generation CdTe thin-film photovoltaics.
11 Tungsten based refractory material composite for fusion applications - theoretical evaluation
H. Gietl
ORNL
On the path to a fusion power plant, the development of advanced materials for plasma facing components is one of the key challenges. Parts of the divertor which will experience high heat loads up to 20MW/m2 are of great interest. Tungsten can survive these heat fluxes and also satisfies other requirements, but its inherent brittleness below the ductile-to-brittle transition temperature and irradiation-induced embrittlement during operation currently limit its use. By adopting a composite structure, the shortcomings of tungsten can be overcome extending the design window. Besides previously studied tungsten fibre reinforced tungsten (Wf /W ), a silicon carbide fibre reinforced tungsten (SiCf /W ) is of interest in this study as SiC fibres are highly resistant to neutron irradiation. The objective of this study is to design the composites microstructures based on composite theory considering irradiation effects and thermochemical compatibility. This analysis found that the fibre volume fraction is a key parameter; e.g. as the fibre volume fraction increases in SiCf /W the tensile strength and toughness increases but the thermal conductivity decreases. The theoretical evaluation of the composites in different states conclude that these composites maintain reasonable properties even after high temperature annealing and/or neutron irradiation which is not the case for current grades of W alloys.
Advances in the Development of Cast and Additively Manufactured High-temperature Aluminum Alloys
R. Michi
ORNL
Commercial aluminum alloys that may be used in the 250-400◦C temperature range have long been sought as potential replacements for steels, Ti alloys, and Ni-based superalloys, with significant implications for the energy and transportation sectors (e.g., increased engine operating temperature and efficiency, lightweighting, cost reduction). In this presentation I will summarize my PhD research on conventionally cast high-temperature aluminum alloys and relate this to my nascent research on additively manufactured alloys here at ORNL. The cast alloys studied during my PhD are based on dilute Al-Sc-Zr aluminum alloys strengthened by coherent, L12-structure Al3(Sc1−x Zrx ) nanoprecipitates. To lower the alloy cost, I developed a Zr-based, Sc-free alloy with similar aging behavior and coarsening resistance to the most advanced Sc-containing alloys developed to date. I will discuss this alloy0s precipitation behavior, the temporal evolution of L12-nanoprecipitates as measured by atom-probe tomography, and the creep properties at 275- 375◦C. I will then discuss how features of additively manufactured aluminum alloys, including microstructural refinement and extended solubility of solute elements, can be leveraged to improve their high-temperature properties.
12 Development of SOLSTISE: A Supersonic Gas Jet Target for Solenoidal Spectrometers
M. Hall
ORNL
The SOLenoid and Supersonic Target in Structure Experiments (SOLSTISE) is a gas jet target currently under development at Oak Ridge National Laboratory, designed for use inside the solenoidal spectrometer SOLARIS at the Facility for Rare Isotope Beams. Experiments utilizing solid targets often have increased backgrounds from unwanted reactions on contaminants and suffer from worsened energy resolution due to energy loss straggling in the target material. In addition, the kinematic compression introduced when measuring transfer reactions in inverse kinematics with traditional silicon detector setups amplifies these issues. SOLSTISE and SOLARIS offer a unique solution to both problems, making their combination the ideal setup for many potential measurements of reactions on exotic nuclei. Rapid part fabrication via additive manufacturing has allowed SOLSTISE to be designed to minimize particle shadowing from the gas piping infrastructure while reducing background pressures, and nitrogen jet densities up to 5x1018 atoms/cm2 have been demonstrated. Current designs and simulation data will be presented.
13 Tuesday
Oral Session 2
Scattering in the Ising Model Using Quantum Lanczos Algorithm
K. Aydeniz
ORNL
Time evolution and scattering simulation in phenomenological models are of great interest for testing and validating the potential for near-term quantum computers to simulate field theories. Here, we simulate one-particle propagation and two-particle scattering in the one-dimensional transverse Ising model for Ns = 3 and Ns = 4 spatial sites with periodic boundary conditions on a quantum computer. We use the symmetry of the system and the quantum Lanczos algorithm as tools to obtain all eigenstates and eigenenergies of the system. These lead to computation of the one and two-particle transition probability amplitudes, the particle number for each spatial site, and the transverse magnetization by simulating the time evolution of the system. The quantum circuits were executed on 5-qubit superconducting hardware. The experimental results with readout error mitigation are in very good agreement compared to the values obtained from exact diagonalization.
14 Topological-Order in Condensed Matter (Complex & Quaternion Sym- metries): A Novel Perspective on Frustrated Crystals, Glassy Dynam- ics & the ’Ideal Glass Transition’ as a 1st Order Critical Point
C. Gorham
ORNL
Complex order parameters have been a cornerstone of condensed matter in the 20th century, most notably for their role in understanding superfluids. When these ordered systems exist in “restricted dimensions” 2D/1D, a rich spectra of ground states are possible in the vicinity of a quantum critical point (e.g., superfluid-to-Mott insulator quantum phase transition). These ordered phases in ’restricted dimensions’ have features of topological-order, similar to the family of quantum Hall effects that may arise when electronic matter is confined to thin-films. My most recent research initiatives have focused on generalizing these concepts to systems with inherent quaternionic symmetries, in which four-dimensional quaternionic order parameters may be utilized to characterize symmetry breaking. Beyond the family of as yet not well-studied 4D QHEs, I have applied such an ordering model in which the quaternion plane is considered as a ’restricted dimension’ to describe solidification of crystalline and glassy materials in three-dimensions. A 1st order crystal-to-glass (order/disorder) phase transition has been identified, making use of a ’Montonen-Olive duality’ between the important degrees of freedom are condensed atomic particles and topological defects (disclinations and third homotopy group). This field theoretic approach provides a novel perspective on the ’ideal glass transition’ as a higher-dimensional analogue to the 2D/1D superfluid-to-Mott insulator quantum phase transition – which is driven by tuning a non-thermal frustration parameter, and results due to characteristic softening of a ’Higgs’ type mode that corresponds to amplitude fluctuations of the complex/quaternion order parameter. The existence of Frank-Kasper crystalline solids, which are geometrically frustrated by a major skeleton of disclination defects (and a lattice of third homotopy group defects), are anticipated within this approach. The first-order nature of the finite temperature crystal-to-glass transition (’ideal glass transition’) is a consequence of the discrete change of the topology of crystalline and non-crystalline ground state manifolds.
15 Examination of Semi-Analytical Solution Methods in the Coarse Op- erator of Parareal Algorithm for Power System Simulation
B. Park
ORNL
With continuing advances in high-performance parallel computing platforms, parallel algorithms have become a powerful tool to develop faster than real-time power system dynamic simulations. In particular, it has been demonstrated in recent years that parallel-in-time (Parareal) algorithm has the potential to achieve such an ambitious goal. To fully utilize Parareal algorithm and improve its performance, it is crucial to appropriately select the coarse operator of Parareal algorithm which is reasonably accurate and fast. This work examines semi-analytical solution (SAS) methods in the coarse operator of Parareal algorithm and explores advantages of SAS methods to the standard numerical predictor-corrector methods. Two promising time-power series-based SAS methods are considered; Adomian method and Homotopy analysis method with windowing approach for improving the convergence. Numerical performance case studies on 10-generator 39-bus system and 327-generator 2383-bus system are performed for these coarse operators over different disturbances, evaluating the number of Parareal iterations, computational time and also stability of convergence. Simulation studies indicate all coarse operators tested with different scenarios have converged to the same corresponding true solution (if they are converged) and SASs provide comparable computational speed, while allowing more stably converging to the true solution in many cases.
Neuromorphic Computing and Graph Algorithms
B. Kay
ORNL
Neuromorphic computing is poised to become a promising computing paradigm in the post Moore’s law era due to its extremely low power usage and inherent parallelism. Traditionally speaking, a majority of the use cases for neuromorphic systems have been in the field of machine learning. In order to expand their usability, it is imperative that neuromorphic systems be used for non- machine learning tasks as well. The structural aspects of neuromorphic systems (i.e., neurons and synapses) are similar to those of graphs (i.e., nodes and edges), However, it is not obvious how graph algorithms would translate to their neuromorphic counterparts. In this work, we propose a preprocessing technique that introduces fractional offsets on the synaptic delays of neuromorphic graphs in order to break ties. This technique, in turn, enables two graph algorithms: longest short- est path extraction and minimum spanning trees.
16 Scalable Non-blocking Krylov Solvers for Extreme-scale Computing
P. Eller
ORNL
Krylov solvers are key kernels in many large-scale science and engineering applications for solving sparse linear systems. Extreme-scale systems have many factors that increase communication costs and cause performance variation across cores that can reduce performance at scale. Many Krylov solvers require frequent blocking allreduce collective operations that can limit performance at scale due to the increasing cost of this collective as the node count increases and the cost of synchronizing all processes. This work investigates non-blocking Krylov solver variations designed to reduce communication costs by overlapping communication and computation using non-blocking allreduces. These variations can allow us to hide most of the allreduce cost and avoiding synchronizing all processes to produce better performance at scale. Performance analysis tools and performance models are developed to provide deeper insight into the performance barriers encountered by these algorithms, show how they relate to observed performance, and guide further optimizations. Detailed experiments at scale for both test problems and real-world applications on multiple supercomputers help provide a more thorough understanding of the performance and robustness of these solvers and how we can use them to efficiently solve linear systems at scale in practice.
NTCL: A GPU Accelerated Tensor Contraction Library for Nuclear Physics
J. Lietz
ORNL
The Nuclear Tensor Contraction Library (NTCL) is a numerical library being designed to tackle the unique numerical challenges presented by nuclear physics calculations. The tensor contractions required to solve the Coupled Cluster (CC) equations contain sparsity structures and patterns that can be exploited depending on physics inputs of the target system. These sparsity patterns result in reductions in storage requirements, but lead to equations that are often no longer suited for use in many existing numerical libraries, especially for use on leadership class supercomputers. Of particular interest is when large tensor contractions become split into hundreds of thousands of smaller tensor contractions which can suffer from overhead issues on GPU. While this library focuses on patterns that show up in the calculation of properties of nuclei, the framework is general enough for use in any domain which requires massively parallel tensor contractions. Progress and numerical results of the NTCL will be discussed.
17 Evaluation platform for sub modules in MMC systems through Power Electronics Hardware-in-the-loop (PE-HIL)
S. Marti
ORNL
Modular Multilevel Converters (MMC) are used in high voltage direct-current transmission (HVDC) to integrate renewable energy into the main grid. MMC consists of several sub-modules (SM) and a complicated controller. Though there are several MMC projects worldwide, with the increase in renewable energy, there is a high demand for the innovations of SM’s in terms of architecture, devices, and controllers. This demand calls in for a need for an evaluation platform to design, develop, and test the integration of new SM’s in MMC with the grid in real-time. A digital real-time simulator can simulate the MMC quickly and accurately. However, we need an evaluation platform where we can validate the new SM architectures in hardware with the rest of the MMC in real-time simulation to analyze the system’s interaction. Evaluating one SM in external with the rest of the MMC system in simulation poses a problem as we need to provide an arm current source for the SM to operate accurately. This research focuses on developing an evaluation platform through power electronics hardware-in-the-loop (PE-HIL), where we can design, develop and test an individual proposed SM in hardware with the rest of the MMC system simulated in real-time simulation. An arm current source for SM is generated through a current amplifier.
18 Wednesday
Oral Session 3
COVID-19 Fake Text Generation
S. Srinivasan
ORNL
Currently the coronavirus pandemic causing the disease COVID-19 is ravaging the entire world. Along with the disease itself, we are seeing a slew of misinformation being propagated online. Misinformation comes in many forms and one of those is those generated by bots. In order to combat this, we need to understand how it is generated. As part of an ongoing effort combat COVID-19 related misinformation, we show that using off the shelf coding libraries, relatively low amount of coding and compute time, and the amount of readily available coronavirus related text data, we can create a bot that can generate convincing summaries about the pandemic given an input. The ease of creating such a bot is a serious cause of concern as it helps propagate fake text and misinformation online which can lead to serious harm.
Investigation of Disorder in Ho2Ti2−x Zrx O7: Pyrochlore to Defective Fluorite Chemical Series
D. Drey
ORNL
Pyrochlore oxides (A2B2O7) are interesting for not only their wide variety of properties, such as ionic conduction and radiation tolerance, but also for their complex defect formation and disordering mechanisms that give rise to their properties. We have used neutron total scattering at the Spallation Neutron Source (ORNL) to study in detail structural aspects of the disordering of pyrochlore which involves randomization of both cation and anion sublattices. By means of diffraction and pair distribution function analysis of a Ho2Ti2−x Zrx O7 (x = 0.0-2.0) solid solution series, the disordering mechanism was studied simultaneously over multiple length scales with novel insight into the local atomic arrangements. With increasing Zr-content, the series exhibits an order-disorder transformation from pyrochlore (space group: Fd-3m) on average to defect fluorite (Fm-3m) across a narrow compositional range (x = 1.0-1.5), while the local atomic arrangement changes gradually to a weberite-type structure (C2221) over the whole compositional range. This distinct disordering scheme can be explained by the movement of a 48f oxygen to a vacant 8a site, creating 7-coordinated Zr sites that produce local weberite-type building blocks. These building blocks accumulate until a critical Zr-content (x∼1.2) is reached which triggers the appearance of long-range structural defect fluorite.
19 Fast ion conduction induced by anion disorder in Li-deficient Argy- rodite
A. Chien
ORNL
Ionic conductivity is an important factor to gauge the performance of a solid electrolyte for applica- tion of all-solid-state Li-ion batteries (ASSLIBs). Recently, Li-deficient Argyrodite (Li5.3PS4.3ClBr0.7) has been demonstrated as a promising solid electrolyte with an ionic conductivity of 24 mS/cm. However, a clear understanding on the structure-property correlation in Li-deficient Argyrodite re- mains unanswered. Here, we conduct a systematic study on Li-deficient Argyrodite (Li6−x PS5−x ClBrx , x = 0, 0.3, 0.5, 0.7, and 0.8) using electrochemical impedance spectroscopy (EIS), neutron powder diffraction (NPD), and pair distribution function (PDF). We found that the increased anion-site disorder between S2− and Cl−/Br− at 4d site is the primary cause for the enhancement of ionic conductivity. Rietveld refinements on the NPD data of Li6−x PS5−x ClBrx reveal that on top of 48h and 24g, Li+ can also occupy 16e, which connects 48h sites to form a three-dimensional ion transport pathway via face-shared tetrahedra. Globally, fast ion conduction is therefore achieved through concerted ion motion among 48h and 16e sites. Locally, the jumping distance between Li-ion cages, as probed by PDF, becomes more randomly distributed when more Br− is incorporated into the structure. This change suggests disorder in anion framework, which is also beneficial to improving the Li-ion conduction.
20 Room temperature X-ray crystallography of SARS-CoV-2 Main Pro- tease unveils structural plasticity of the active site cavity and reactiv- ity of the catalytic cysteine
D. Kneller
ORNL
The COVID-19 pandemic is an ongoing public health and economic emergency. With no current FDA approved treatments against the SARS-CoV-2 virus, the viral main protease (3CL Mpro ) enzyme has emerged as one of the most promising drug targets. Structure-guided drug discovery and design of 3CL Mpro inhibitors requires accurate starting models derived from experimental data. Here, results from the rapid mobilization efforts of ORNL’s COVID-19 structural biology team are presented as a series of 3CL Mpro room temperature protein X-ray crystallography structures. X-ray crystallography, typically performed at cryogenic temperature, derives the coordinates of heavy atoms in the protein three-dimensional structure. Near-physiological temperature structures reveal conformational flexibility of the active site cavity and a rare peroxysulfenic acid oxidation state for the catalytic cysteine to be identified. These structures provide important functional information about the enzyme and give insights for further drug design. Structures were made immediately accessible to the scientific community and already being utilized for computational drug discovery and design efforts. X-ray crystallography is a powerful technique yet fails to identify biologically important hydrogen atoms. Neutron crystallography is the ultimate technique for direct determination of hydrogen positions. Thus, strides towards growing large crystals required for neutron diffraction experiments are discussed.
21 Modeling of local atomic structure in disordered and nanostructured materials
B. Jiang
ORNL
Pair distribution functions (PDF) obtained from total scattering (high energy synchrotron X-ray and Neutron scattering) can reveal both the local and intermediate range structure of crystalline, disordered and nanostructured materials. As we all know that conventional reciprocal space diffraction only probes the average long-range structure of the Bragg planes, and information from EXAFS and XANES is limited to no more than third coordination shell, PDF can reveal both local distortions and measure the structural coherence up to several tens of Angstrom. With optimized sample environments PDFs can also be collected under in situ mechanical and electrical fields. A combination of multiple approaches using PDFgui (graphical interface built on the PDFfit2 engine), RMCProfile (Reverse Monte Carlo software), TOPAS v6 (combined reciprocal and real space neutron PDF data) and DISCUS (simulate disordered/nano crystal structures) were performed throughout this work. The experimental total scattering PDF activity will be closely supported by density functional theory (DFT) calculations to investigate the electronic structure under simulated electrical and mechanical fields. PDF modeling can give realistic starting models for DFT relaxations of large supercell models. Conversely, DFT relaxations can aid the fitting of experimental PDFs.
Determination of Ground State Feedings in β-decay using Modular Total Absorption Spectrometer
P. Shuai
ORNL
Determination of the branching ratio of ground state feeding in β-decay of fission products is of large interest in the research of reactor antineutrino anomaly and decay heat calculations. Ground state branches are important or even dominant in a number of such decays. However, the determination of ground state feeding probabilities encounters large systematic uncertainties due to the difficulty to precisely simulate the response function of low-energy electrons. Modular Total Absorption Spectrometer (MTAS), which is approximately one ton of NaI(Tl) hexagonal modules covering almost 4π solid angle, is a versatile spectrometer to detect the β-decay particles including gammas, electrons and beta-delayed neutrons with high efficiency. MTAS has capability to determine not only the β-decay branching ratios of exited states free from Pandemonium effect, but also the ground state feeding which is lack of coincidence gammas. In this talk, we use 88Rb and 88Kr decay as examples to demonstrate the ability of MTAS to determine the absolute ground state feeding branching with improved precision. We also discuss various possible sources that contribute to the systematic uncertainties in MTAS experiments.
22 Progress in n.c.a. Lu-177 Production at ORNL
A. Kimberlin
ORNL
177Lu is rapidly becoming an important radioisotope for a variety of medical uses, including bone targeted palliation therapy and treatment of gastroenteropancreatic neuroendocrine tumors. Production of 177Lu must be done in such a manner as to minimize the amount of 177mLu, whose long half-life makes it unsuitable for radiation therapy. The production of carrier-free 177Lu, or 177Lu without the metastable product, can be achieved by irradiating highly enriched 176Yb via the (n,β-) reaction. The High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory is one of the few reactors that can achieve a high enough neutron flux to perform this reaction effectively. Removal of the 177Lu radioisotope from the bulk 176Yb must be performed to achieve a high enough specific activity for radiotherapy use and for the 176Yb to be recycled. Several different methods are being explored to perform this separation, including extraction chromatography and cation exchange chromatography. These can be used in conjunction with a High-Pressure Ion Chromatography (HPIC) system to achieve the best separation in the smallest amount of time. All these separation techniques will eventually be transferred to a hot cell for carrier-free 177Lu production.
23 Wednesday
Oral Session 4
Deep Learning Generative Method for Engineering New Proteins
G. Degaga
ORNL
Molecular level understanding of the structure and function of proteins is a key part of modern biosciences research. A major engineering challenge is to design new proteins in a controlled way for particularly targeted localized properties, folds, expressions, and functions. Here, we developed sequence based Deep Convolutional Generative Adversarial Networks (DC-GANs) to design targeted protein secondary structures. We encode our protein sequences with physicochemical and structural-statistical features associated to each residue. The effectiveness and accuracy of our models are confirmed by molecular dynamics and physical laboratory synthesis and evaluation using circular dichroism spectroscopy.
24 Ecological and genomic responses of soil and plant microbiomes to wildfire: linking fundamental community assembly processes to soil quality and plant health
N. Dove
ORNL
While wildfire is ubiquitous across many terrestrial ecosystems, there is a relative scarcity of fire-related microbial ecology research. Here, we report work from two projects that evaluate the effect of fire on the soil and plant microbiome: To assess the impact of fire on the soil microbiome, we used biogeochemical, amplicon, and metagenomic analyses from soils collected in burned mixed-conifer forests of the Sierra Nevada (California, USA). Using a chronosequence-based study design, we assessed the long-term (44 y) impacts of high-severity fire on soil microbial community composition and genomic functional potential. To assess the impact of fire on the plant microbiome, we sampled aspen (Populus tremuloides) saplings less than three months after a high-intensity prescribed burn from areas varying in burn severity in central Utah, USA. We used amplicon sequencing of the bulk soil, rhizosphere, and endospheric microbiomes and used statistical models to determine changes in microbiome colonization patterns. From our work on the soil microbiome, we show that high-severity mega-fires can result in multidecadal changes to the soil microbial community structure and genetic potential which are associated with large changes in carbon and nitrogen cycle process rates. Additionally, we extracted 206 metagenome assembled genomes (MAGs) from soils at these sites and characterized these MAGs as early- or late-successional colonizers. Early-successional colonizers were enriched in genes encoding for proteasomes, which degrade non-functional proteins. This suggests that these bacteria are well-adapted to stressful post-fire soil environments. Work from our second study shows that wildfire-induced changes to the soil microbiome leads to altered plant endosphere colonization patterns, particularly increased vertical transmission of microbes from surviving plant rhizomes during clonal suckering in aspen. By incorporating both plant and soil microbiome responses to fire, it is our goal to holistically understand the impact of fire on the microbial community and uncover links among soils, plants, and microbes in post-fire landscapes.
25 Roll-to-Roll Slot-Die Coating of Concentrated Electrocatalyst Layer Inks for PEM Fuel Cells
E. Creel
ORNL
Roll-to-roll (R2R) slot-die coating of polymer electrolyte fuel cell (PEFC) catalyst layers represents a scalable deposition method for producing multiple square meters of catalyst-coated gas diffusion layers (GDLs) per minute. We establish the ability to use a concentrated catalyst ink (12 wt.%) for 2 R2R slot-die coating while maintaining the 0.1 mgP t /cm DOE Pt loading target, demonstrating a viable pathway for meeting the ultimate DOE Hydrogen Fuel Cells Technologies Office (HFTO) cost target of $30/kW net . The increase in solids loading of the slurry lowers the thermal energy and capital expenditure (CapEx) budget of the coating process by decreasing the amount of time, energy, and floorspace required for drying the coating. The high water content in the dispersion media system decreases the environmental and human health impacts of slurry drying by replacing low-molecular-weight alcohols with water. We use in-situ PEFC performance testing to compare catalyst layers produced by this method with lab-scale spray-coated catalyst layers. We also compare the PEFC performance of catalyst layers deposited with different slot-die coating parameters.
Mechanobiology of T cell receptors and chimeric antigen receptors: a head-to-head comparison study
D. Banik
Vanderbilt
T lymphocytes (T-cells) are the building blocks of adaptive immune system. Recently, chimeric antigen receptor (CAR) T-cell therapy has been used to treat specific types of leukemia patients. This study provides a direct comparison of the mechanobiology of chimeric antigen receptor (CAR) and T-cell receptor (TCR) activation at both the single cell and single molecule levels. In single cell activation studies with optical tweezers triggering through force on pMHC coated beads we find that while CAR cells require slightly lower antigen concentration for triggering they require higher mechanical force than αβ TCR cells for activation. Importantly, CAR triggering is more immediate and sustained, consistent with its known responsiveness as a CAR T-cell therapy. Based on single molecule measurements of beads coated with DNA bound pMHC, we observe differences in the catch bond profile, conformational transition magnitude and probability of transitioning between CAR and αβ TCR bonds with pMHC. We propose that the conventional conformational transition of the αβ TCR is absent in CAR T-cells and a lower probability conformational transition in pMHC may be underpinning the CAR response. We expect our study will be beneficial for the engineering and design of more advanced CAR based therapies.
26 Deciphering Host Immune Responses to Staphylococcus aureus In- fection by Combining Imaging Mass Spectrometry and CODEX Mul- tiplexed Immunofluorescence
E. Neumann
Vanderbilt
Infected mammalian tissue consists of dynamic, chemical exchanges between the host immune system and invading pathogens. To explore this interface, we combine imaging mass spectrometry (IMS) with codetection by indexing (CODEX) multiplexed immunofluorescence (IF) to visualize hundreds of metabolites and create metabolic profiles of different functional regions and cell types. In brief, we section murine kidneys infected by Staphylococcus aureus and perform IMS on one section and CODEX IF on the serial section. Overall, we putatively identified over one hundred lipids species, including phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins. Many of these lipid species localize to functional substructures within the kidney, such as tubules and glomeruli, as well as abscess architecture. For correlation with CODEX, we have optimized methods for staining 7 immune-related markers, such as CD11 and Ly6g, which label dendritic cells and neutrophils, respectively. Using these methods, we visualized these immune cells and measured their density in the tissue. Further, we also successfully conjugated six markers to CODEX oligonucleotide tags, allowing us to image distal tubules, proximal tubules, glomeruli, and S. aureus. In total, we obtained CODEX IF images of 15 different antigens, providing coverage of both immune and functional cell types. Future work will incorporate additional infection time points.
27 Autoantibody responses to apolipoprotein A-I are not diet or sex- linked in C57BL/6 mice
M. Pitts
UTK
Long thought of as a disease of overconsumption and metabolic imbalance, but not necessarily one impacted by immune processes, atherosclerosis is only now beginning to be understood in all its complexity. The disease process likely begins early in life and involves interplay between many processes, including generation of antibodies targeting self-proteins like apolipoprotein A-I (ApoA-I). In this study, we modeled autoimmune targeting of ApoA-I using anti- ApoA-I immunization and followed male and female C57BL/6 mice on control or Western diets over nine months, tracking their anti-ApoA-I responses and total circulating antibody subclasses. Surprisingly, we found that anti- ApoA-I autoantibodies were not related to diet, sex, or even dyslipidemia. Additionally, these responses were largely targeted toward a discrete sequence upstream of the lecithin- cholesterol acyltransferase (LCAT) domain of ApoA-I, the immunogenic epitope reported in humans. Lastly, when IgG subclasses in mice consuming Western diet were analyzed, we observed suppression of increases in IgG2b and IgG2c in males, but not females, indicating roles for diet and sex in Th1-Th2 balance. This demonstrates the distinct need for inclusion of both sexes in studies of anti-self antibodies in cardiovascular disease development and suggests that further study of immunogenic epitopes in ApoA-I is warranted.
28 List of Abstracts – Posters
Wednesday
>>Timetable
Poster Session 1
NO. Presenter Title 1 Shree Acharya Tuning electronic structure and stability of ABX3 perovskites by A-site composition: A First-principles study 2 Muneer Alshowkan Trusted-Node Quantum Key Distribution on an Electrical Grid 3 Kadir Amasyali Genetic Algorithm for Demand Response: A Stackelberg Game Ap- proach 4 Ahmadullah Ansari Neutron crystal structure of the wild-type Staphylococcus Nuclease 5 Sumit Bahl Damage mechanisms under monotonic and cyclic deformation of cast Al-Cu-Mn-Zr alloys 6 Zhenghong Bao Intelligent nonprecious metal-doped SrT iO3 catalysts for CH4 com- bustion 7 Tommy Boykin Spray-deposited metal-chalcogenide photodiodes for low cost infrared imagers 8 Zach Brubaker High-temperature stability of monofilament carbon fibers probed with Raman spectroscopy 9 Hui Cai Nonequilibrium Synthesis of Mismatched 1T’ Transition Metal Dichalco- genide Alloys for 2D Topological Insulators 10 Dana Carper A constructed community approach to understand bacterial community assembly in Populus 11 Daniel Claudino A hardware-agnostic framework for hybrid classical-quantum chemistry simulations 12 Luc Dessieux Development toward mapping oligo-crystals with single crystals using neutron transmission 13 Derek Dwyer Understanding the Thermal Decomposition of Cured Epoxy Resin using Pyrolysis GC-MS 14 Jordan Easter Reducing Emissions in Heavy Duty Transportation through Novel Com- bustion Modes and Modern After-treatment 15 Jeffrey Einkauf Photoisomerization Behavior of Pyridine-Functionalized Diiminoguani- dinium Isomers Towards Molecular Switching for Anion Separations 16 Justin Felder Investigating the Magnetism of the Honeycomb Arsenate KCo2(AsO4)(HAsO4) 17 Rui Feng Order-disorder transition behaviors in lightweight high-entropy alloys
29 18 Zhuozhi Ge STM/S study of surface-related states and atomic defects on Ba(F e, Co)2As2 19 Antigoni Georgiadou Emulating The Cosmic Large-Scale Structure 20 Kakali Ghoshai Administration of epoxyeicosatrienoic acid analogs (EET-A) can restore insulin sensitivity in Cyp2c44 (-/-) mice 21 Ian Greenquist A Metallic Fuel Performance Benchmark Problem Based on the IFR-1 Experiment 22 Mary Healy RAPID Analytical Technique for the isotopic analysis of fission and actinide elements 23 Igor Gussev Atomic-scale disordering in weberite-type complex oxides 24 Matthew Heath CENNS-750: A Ton-Scale Liquid Argon Detector for CEvNS at the SNS 25 Sara Isbill Investigating the defect-induced changes in the electronic and vibra- tional properties of graphitic materials using density functional theory 26 Vasudevan Iyer Near-field Imaging of Circular Dichroism in Plasmonic Nanospirals 27 Mihee Ji High-performance Vertical Ga2O3 Schottky Barrier Diodes for Power Device Applications 28 Xiao Jiang Mechanistic Understanding of Propane Oxidative Dehydrogenation over Hexagonal Boron Nitride-based Catalysts 29 Min-Tsung Kao CFD Modeling Supports Developing the Target Segment Conceptual Design for the Second Target Station 30 Omer Karakoc Mechanical Properties and Microstructure of Laser Chemical Vapor Deposition of SiC Fibers 31 M. Arif Khan Physicochemical modeling of dissolution and stability of poorly soluble and unstable drugs loading into multilayer soluble polymeric films 32 Shruti Kulkarni Development of Large-Scale Neuromorphic Computing Framework 33 Mohit Kumar Resilience Structural Design Patterns Modeling 34 Vineet Kumar Thermal Loading Analysis of the Ring Injection Dump 35 Pontus Laurell Dynamics, Entanglement, and the Classical Point in the Transverse- Field XXZ Chain 36 Travis Lawrence Characterizing a tripartite plant - fungus - bacteria symbiosis 37 Lu Lin Anions Tune the Self-Assembled Structure of Ionic Oligomers at Buried Liquid/Liquid Interfaces: Implications for Designing Molecular Devices 38 Majbah Uddin Multimodal Transportation Flows of Crude Oil in the United States
30 Wednesday
>>Timetable
Poster Session 2
NO. Presenter Title 1 David Lingerfelt Electronic excitations and their impact on point defect diffusion in graphene 2 Chenze Liu In-situ characterization of the mechanism of laser induced crystallization from amorphous precursors within a TEM 3 Phillip Lotshaw Solving Optimization Problems with Quantum Computers 4 yuandong liu Dynamic traffic queue-end identification using location-based crowd- sourced Waze user reports 5 Isaac Lyngaas SAM++: Porting SAM to performance portable C++ 6 Xiaohan Ma Polymer upcycling by 2D visible-light-driven photocatalyst loaded with single atoms 7 Sreshtha Majumdar Three-way Catalyst Reactivity of Novel High-performance Fuel Blends for SI Engine Emissions Control 8 Bryan Maldonado Machine learning-based predictive control of misfire events in spark- ignition engines 9 Keyou Mao In-situ Micromechanical Testing of Neutron Irradiated Alloys 10 Claire Marvinney Position-Dependent Response of a Large-Area Superconducting Nanowire Single Photon Detector 11 Peter Metz Structural signatures of defects in organic framework materials 12 Narayan Mohanta Magnetic Switching in Weyl Semimetal-Superconductor Heterostruc- tures 13 Jisue Moon Role of hydride and hydroxyl groups in Acetylene Semi-hydrogenation over Ceria 14 Daniel Moreno Carbon Utilization: Electrochemical Approach Using Novel Catalyst and System Integration 15 Daniel Morrall Tungsten nanofuzz 16 Jessica Moore Microbial community reassembly following species gains and losses 17 Debangshu Mukherjee Lattice strain metrology in catalyst nanoparticles through 4D-STEM 18 Thien Nguyen Enabling Exascale Quantum Circuit Simulation for XACC with ExaTN 19 Cory Parker Understanding Corrosion Mechanisms of Ni-Cr Alloys Exposed to Molten Fluoride Salts 20 Krishna Pitike Predicting the phase stability of high entropy oxides 21 Uvinduni Premadasa One for all: Imaging complex biological systems using a multimodal nonlinear optical microscope 22 Eric Johnston Genome-resolved metagenomics enables fine-resolution assessment of peatland microbial communities and methanogen processes
31 23 Marie Romedenne Effect of water vapor and composition on oxidation lifetime of alloys 625 and HR120 foils between 650 and 800 ◦C. 24 Tomas Rush Friend or Foe? Deciphering microbial communication that influences community structure and function. 25 Allen Scheie Witnessing Entanglement in KCuF3 using Neutron Scattering 26 Shivakant Shukla High temperature cyclic loading behavior of novel Fe-Ni-Cr alloy 27 Tyler Spano High temperature calcination products of UO2F2 28 Jared Streich Genome Wide Association Time-Series Studies to find Temporal Cli- mate Adaptation in Poplar Trees. 29 Yali Sun Deciphering the functions of PtLecRLKs in Plant-Microbe Interaction 30 Calvin Thomas Effects of Hydrocarbon Structure on Adsorption Energetics on BEA Zeolite 31 Juha Tlihonen Quantum Monte Carlo Forces for Heavier Ions: A Benchmark Study 32 Miguel Toro-Gonzalez Tailoring the surface chemistry and encapsulation of therapeutic agents in lanthanide vanadate and poly(lactic-co-glycolic acid) nanoparticles for nanomedicine 33 Majbah Uddin Movements of Municipal Solid Waste in the United States 34 Michael Vergara RNA-based countermeasure against the CRISPR/Cas9 gene-editing tool 35 Jia Wang Genomic-scale modeling of the interaction among the bacteria isolated from Populus deltoides 36 Zak Webb On the universality of the variational quantum eigensolver framework 37 Haowen Xu Visual Analytics for Exploring Highway Traffic Dynamics using Inte- grated Sensor Data 38 Yiling Yu Strain Evolution and Grain Boundary formation in the Coalescence of Two-Dimensional Crystals 39 Jie Zhang Engineering Colossal Linear Magnetoresistance in High Mobility SrNbO3 Thin Films
32 Poster Session 1
Tuning electronic structure and stability of ABX3 perovskites by A- site composition: A First-principles study
S. Acharya
ORNL
Hybrid organic-inorganic halide perovskites have emerged as absorber materials in high efficiency photovoltaics. The enhanced efficiency can be understood in terms of band gap which controls the optical adsorption. However, the volatile organic cation on the A-site presents challenges to attain impactful long-term stability. In this study, we explore how mixing A-site bearing CsPbI3 and RbPbI3 perovskites with the volatile A-site cations of the MAPbI3 and FAPbI3 perovskites can be used to enhance the stability of these materials while maintaining their favorable electronic properties. Here we employ a mix of electronic structure calculations with Monte Carlo simulations and machine learning to provide a framework through which these materials can be quickly optimized for optoelectronic applications.
Trusted-Node Quantum Key Distribution on an Electrical Grid
M. Alshowkan
ORNL
In March 2020, in collaboration with Los Alamos national laboratory, Qubitekk, Inc. and the Electric Power Board (EPB), we successfully demonstrated a trusted-node quantum key distribution (QKD) system on a dedicated communications network in Chattanooga, TN. The network demonstrated the generation of quantum-secure secret keys between EPB’s operations center and several electrical utility substations. Demonstrating the use of QKD performance in a real-world scenario helps validate the practical use of this technology for protecting critical energy delivery infrastructure. Our trusted-node QKD approach allows for interoperability between different QKD systems, the addition of ‘users’ to the quantum communications network, and crucially – the distance over which QKD can be performed to be extended. We discuss the key management layer in detail, specifically the processing of disparate QKD system key material and the so-called ‘hop-by-hop’ key distribution mechanisms allowing seamless interoperability. This approach extends the physical distance over which systems can communicate, covering larger territory than a single system operating on its own. We present data collected from a real electrical substation environment and the distribution of network keys. We show QKD provides a novel solution for distribution of secure keys used for authentication and encryption of power grid command and control communications.
33 Genetic Algorithm for Demand Response: A Stackelberg Game Ap- proach
K. Amasyali
ORNL
Demand response (DR) has gained a significant recent interest due to its potential for mitigating many power system problems. Game theory is a very effective tool to be utilized in DR management. In this paper, the DR between a distribution system operator (DSO) and load aggregators (LAs) is designed as a Stackelberg game, where the DSO acts as the leader and LAs are regarded as the followers. Due to the limitations of the centralized solution approaches, a genetic algorithm- based decentralized approach is pro-posed. To demonstrate the proposed approach, a case study concerning a day-ahead optimization for a real-time pricing market with a single DSO and three LAs is designed and optimized. The proposed approach is able to shift the demand peaks and prove that it has a great potential to be used for the Stackelberg game between a DSO and multiple LAs to fully exploit the potential of DR.
Neutron crystal structure of the wild-type Staphylococcus Nuclease
A. Ansari
ORNL
Staphylococcal nuclease (SNASE) is a well-studied, protein model system that has been used to understand the fundamental properties that are central to protein stability and dynamics, as well as the ionization state of charged residues. SNASE is a ∼16 kDa globular protein, hundreds of variants of which have been biophysically and computationally characterized. To date, the position of hydrogen atoms on these SNASE protein structures have been predicted by chemical and geometrical knowledge, since the available crystal structures do not directly reveal the position of hydrogens atoms. To address this problem, and to further investigate the nature of hydration and polar interactions in the hydrophobic core of the SNASE, we have determined a 2.5 resolution neutron structure of the protein with a substrate analogue bound using the IMAGINE beamline at HFIR. This has enabled explicit determination of the exchangeable H positions on the protein and of the associated water molecules at a proton level of detail. The nearly complete atomic structure of SNASE includes the 226 well-refined positions of exchangeable deuterium atoms on the protein and 58 D2O molecules. The structure has enabled the protonation states of charged residues, buried water molecule orientation to be directly determined, and for the delineation of crucial H-bonding networks that are considered to be central to the folding and stability of this protein archetype.
34 Damage mechanisms under monotonic and cyclic deformation of cast Al-Cu-Mn-Zr alloys
S. Bahl
ORNL
Cast aluminum alloys are high temperature structural materials widely used in automotive en- gines. Al-Cu-Mn-Zr (ACMZ) is a new class of affordable cast aluminum alloys designed to have ◦ microstructural stability up to 350 C(∼ 0.7Tm homologous temperature). This work describes damage mechanisms leading to fracture under monotonic tensile and low cycle fatigue deformation of ACMZ alloys. The brittle intermetallic grain boundary θ (Al2Cu) particles present in the alloy microstructure, fracture under monotonic loading to produce an array of microcracks that coalesce together and result in complete fracture. The lower levels of applied stress and strain in fatigue are insufficient to fracture θ particles. In this case, large near-surface pores that create high strain concentration in the Al matrix are favored sites for fatigue crack initiation. These results explain experimental observations that a reduction in θ phase fraction of the microstructure by lowering the alloy’s Cu content improves ductility but does not influence fatigue life.
Intelligent nonprecious metal-doped SrTiO3 catalysts for CH4 com- bustion
Z. Bao
ORNL
The intelligent behavior of a catalyst initially refers to the repeated movement of precious metals in and out of perovskite oxides between a solid solution and metallic nanoparticles. Strontium titanate (SrTiO3, STO) is an extensively investigated perovskite in various applications due to its optical, electrical and chemical properties. 10 mol% of metal (Cu and/or Ni) doped SrTiO3 nanoparticles were prepared by hydrothermal synthesis as reported previously. The synthesized catalysts were evaluated for methane catalytic combustion after various treatments. The sample without treatment has a higher activity than the O2-treated one, suggesting the presence of some nickel oxide on the STO surface. The sample with O2 treatment does not show low temperature activity, suggesting the metal oxide goes into the STO lattice. The sample after ◦ H2 treatment shows low temperature activity (400 – 500 C) for both Ni doped STO and Cu doped STO, indicating the formation of metallic clusters on the surface. However, at higher ◦ reaction temperature range (> 600 C), it shows similar activity with the O2 treated case, which infers the metallic clusters are re-oxidized and incorporated into the STO lattice. Cycling tests of nd the H2-treated sample show similar activity to the O2-treated sample while performing a 2 H2 treatment, the sample shows the lower temperature activity again, suggesting intelligent behavior of the doped STO.
35 Spray-deposited metal-chalcogenide photodiodes for low cost infrared imagers
T. Boykin
IGEN Program
Low cost, light-weight, low-power, large-format, room-temperature, mid-wave infrared (MWIR) detectors are needed for reduced-scale aircraft. An opportunity, suggested by direct-read X- radiography systems, is the use of thin-film transistor (TFT) array as readout integrated circuit (ROIC) for low-cost sensors deposited directly and unpatterned onto this ROIC. TFTs have already been thoroughly optimized for power, weight, large-format, and cost by the flat panel display industry. We present experimental investigation of aqueous-spray-deposited, mid-wave-IR, metal- chalcogenide heterojunction CdS/PbS photodiodes for this application. Measured responsivity, detectivity D*, and photoresponse spectra are reported.
High-temperature stability of monofilament carbon fibers probed with Raman spectroscopy
Z. Brubaker
ORNL
We investigated the microsctructure of high-performance T700, IM10-GP, and IM10-GS carbon fibers exposed to distinct heat treatments using scanning electron microscopy and Raman spec- troscopy. The fibers were heated (a) to 1,500 ◦C under a moderate vacuum of 10−4 to 10−5 bar and held for up to 60 min or (b) up to 750 ◦C for 5 min in air. The fibers heated in air narrowed slightly and showed changes in the Raman spectra that likely resulted from a re-oxidation step and strain relief. The fibers heated under vacuum narrowed significantly, which was likely the result of trace gases oxidizing the fiber surfaces. Fibers with diameters close to 4 µm degraded anisotropically, which we speculate is due to the different heat transfer properties of the fiber skin and fiber core. The extracted Raman parameters of fibers heated in vacuum indicate an increased degree of graphitization.
36 Nonequilibrium Synthesis of Mismatched 1T’ Transition Metal Dichalco- genide Alloys for 2D Topological Insulators
H. Cai
ORNL
Transition metal dichalcogenides (TMDC) are an emerging class of quantum materials because they are 2D topological insulators in the 1T’ phase and Weyl semimetals in the Td phase. To optimize the properties of these materials, synthetic methods to tune their Fermi level and bulk gap opening are necessary. This can be realized by synthesizing alloys with a wide range of adjustable compositions. Mismatched alloys, such as MoS2−x Tex , are alloys formed by elements far away from each other in the periodic table. Due to the large mismatch in atomic radius and electronegativity, a small addition of the alloying element can induce dramatic modifications in the electronic structure of the material. However, such immiscible alloys are hard to synthesize as bulk crystals by conventional crystal growth methods, especially in metastable phases such as the 1T’ phase. Here, we report the bottom-up synthesis of mismatched alloys of 2D MoS2−x Tex in the 1T’ phase by chemical vapor deposition through non-equilibrium methods. We introduce K+ during the synthesis to grow the 1T’ phase, followed by fast cooling to stabilize this phase to room temperature. With this approach, MoS2−x Tex alloys can be grown on various substrates including mica, sapphire and gold. The 1T’ structure of the flakes are confirmed by Raman spectroscopy and scanning transmission electron microscopy. Our results open new opportunities in tailoring the structure and properties of quantum materials by alloying mismatched elements through non-equilibrium synthesis.
37 A constructed community approach to understand bacterial commu- nity assembly in Populus
D. Carper
ORNL
Field grown Populus harbor a diverse consortium of microbes. To gain insight into the functional role of these microbial members on the Populus host, we isolated over 3,200 strain bacterial strains. Our prior studies used this collection with individual strains and very reduced community (< 10 members) assays to evaluate questions pertaining to plant – microbe interactions. However, communities with additional complexity are needed if we hope to address boarder community-based questions, such as the rules governing community assembly and the relationship between diversity and function. To this end, we created a constructed community approach that distinguishes the genetic diversity of genome sequenced strains using Illumina 16S rRNA sequencing. We are using this approach to inoculate germ-free Populus trichocarpa with bacterial communities to determine how host plant genetics and nutrients interact to shape the associated community. To create the constructed community, we used a program called DISCo-microbe, which constructed a community distinguishable within the 16S rRNA region that spans substantial genetic diversity. The resultant community of 150 members was used to inoculate P. trichocarpa plants subsequently exposed to differing environmental conditions for 3 weeks (control (C), warm temperatures (W), cold temperature (CT), low nitrogen (LN) and warm temperature and low nitrogen (WLN)). Sequencing of the inoculum identified 145 out of 150 bacterial members. Tissue type (root, stem and leaves) and environmental condition structured the community using weighted UniFrac metrics (tissue: 25.7%, environment: 14.4%). The most abundant member across environmental conditions was a Rhodanobacter strain, whose genome encodes rhizosphere fitness traits suggesting a mechanism for its high rate of colonization. A few strains were found across all treatments and all tissues, including Rahnella aquatilis, a strain with demonstrated nitrogen fixing ability. Further investigation into the data is needed to understand the colonization patterns and potentially beneficial capabilities of the strains.
38 A hardware-agnostic framework for hybrid classical-quantum chem- istry simulations
D. Claudino
ORNL
One of the most immediate applications of quantum computing are simulations aiming at the investigation and characterization of quantum many-body systems. Chemistry at the molecular level, i.e., quantum chemistry is seen as one of the areas that will greatly benefit from successful undertakings from such quantum computations. However, the quantum processors of present, also known as Noisy Intermediate-Scale Quantum (NISQ) are not expected to be fully mature in the short term, and realistic endeavors in this emerging fieldare heavily reliant on the harmonious interplay between quantum computers and classical counterparts. With the radically different quantum hardware architectures and programming languages currently available, efforts toward unifying these tools are highly valuable.In this spirit, the eXtreme ACCelerator (XACC) is an established framework that enables quantum-classical computing in a hardware-agnostic fashion as well as allows access to simulator backends. We will present recent developments in XACC that will enable leveraging large-scale high-performance computing (HPC) clusters in conjunction with quantum hardware from established vendors (IBM, Rigetti, D-Wave, IonQ, and others) targeting quantum chemical simulations, with focus on flexible algorithmic development.
39 Development toward mapping oligo-crystals with single crystals using neutron transmission
L. Dessie
ORNL
The mapping of grains and their orientation is used to investigate the correlation between polycrystalline materials properties and their microstructure. Techniques such as scanning electron microscopy electron backscatter diffraction (SEM-EBSD), and X-ray diffraction (XRD) imaging are often used for grain orientation mapping. Both techniques are limited by their penetration depth, sub-micrometers (SEM-EBSD), and micrometers (XRD imaging). Neutrons higher penetration depth provides outstanding structural features for studying bulk samples. The transmission spectra of single crystal or oligo-crystal samples are characterized by dips at wavelengths, where Bragg’s law is being fulfilled for unique crystal orientations, which can be used to resolve the orientation of the crystals and assess the microstructure at the local grain level. In this presentation, I will discuss efforts to map oligo-crystal with single crystal using the Sinpol application. Sinpol is a collection of routines for calculation of the attenuation of neutron beam by crystalline specimens. The total cross section is calculated as a function of neutron energy, crystal structure, temperature, and crystal orientation. The contribution of Bragg (elastic coherent) scattering to the total cross section is evaluated within secondary extinction theory using both the crystal’s mosaic spread value and its orientation with respect to the neutron beam direction as parameters. The Sinpol simulations can be used in an iterative way to determine a single crystal orientation and offer a potential tool to discriminate between multiple single crystals in oligo-crystalline samples.
40 Understanding the Thermal Decomposition of Cured Epoxy Resin using Pyrolysis GC-MS
D. Dwyer
ORNL
Epoxy resins are a three-dimensional amorphous polymer network. Deriving their name from the epoxy functional group present in the prepolymer material, the chemistry that results in their formation is well known. Curing of the epoxy resin occurs when a hardening agent, normally a primary or secondary amine, is added. The hardener then reacts with the epoxy group resulting in ring opening and bond formation. Although this chemistry is relatively simple, the types of three- dimensional structures that form can vary drastically because of the availability of many different epoxy prepolymers and hardeners. Because of the diversity of precursor materials, the properties of cured epoxy resins are highly tunable, resulting in their use in protective coatings, reinforced resins, electrical applications, bonding, adhesives, and much more. Significant research has been performed not only on the development of these epoxy resin materials but also on their properties, structure, and chemical characterization including thermal decomposition. Understanding the thermal decomposition pathways of these epoxy resins is extremely important in understanding the failure modes of these materials when used in extreme conditions such as in space applications. Such understanding can allow for improvements in the properties of these materials. Here, a multifunctional high temperature microfurnace, used for evolved gas analysis mass spectrometry (MS) and in combination with thermal desorption/pyrolysis gas chromatography MS, were used to better understand the influence of heating parameters on thermal decomposition rates and products for epoxy resins under both an inert and oxidative atmosphere.
41 Reducing Emissions in Heavy Duty Transportation through Novel Combustion Modes and Modern After-treatment
J. Easter
ORNL
Highway vehicles account for roughly half of US anthropogenic NOx emissions, with heavy-duty trucks comprising the largest transportation related source. As a result, regulatory agencies have proposed new regulations targeting heavy-duty engines to reduce NOx emissions. Aftertreatment systems used by diesel engines for compliance with current regulations may struggle to meet these proposed standards. This is largely due to low exhaust temperatures present under light load conditions that prevent the effective use of the Selective Catalytic Reduction (SCR) catalyst. One promising option for reaching stringent NOx emission regulations is to operate the engine at a low temperature combustion (LTC) mode while the engine is at a problematic light load condition. Conventional diesel combustion (CDC) could still be used outside of this operating condition through mode-switching. LTC combustion has been proven effective at reducing tailpipe NOx levels. However, this strategy results in elevated levels of hydrocarbon and CO emissions. Luckily, these emission constituents may be oxidized using a conventional diesel oxidation catalyst (DOC). In this work, we will use a single-cylinder diesel research engine equipped with advanced emissions characterization diagnostics. This research will investigate impacts of CDC/LTC mode-switching coupled with a DOC on enabling improved combined emissions without reducing fuel efficiency.
Photoisomerization Behavior of Pyridine-Functionalized Diiminoguani- dinium Isomers Towards Molecular Switching for Anion Separations
J. Einkauf
ORNL
The principle of photoswitching can be applied to molecular recognition as a means to potentially unlock efficient recyclable separations of oxoanions using a simple stimulus such as light and a dynamic photoreceptor. In order to realize this goal, however, many challenges must be overcome to satisfy the economic and environmental necessities of such a process. It is critical initially to understand the photoisomerization behavior of the dynamic receptor and the resulting effect on binding of a target anion species. To this end, a set of pyridine-functionalized diiminoguinidinium isomers (PyDIG) have been chosen as candidates for photoswitched separation cycling, due to their rigid and planar structure along with their unique hydrogen-bonding motifs. The photoisomerization efficiency with UV-Visible light and thermal relaxation of these PyDIG isomers are reported. These initial results establish the groundwork for future studies investigating efficient photoswitched binding-release separation cycle behavior of the PyDIG family of receptors.
42 Investigating the Magnetism of the Honeycomb Arsenate KCo2(AsO4)(HAsO4)
J. Felder
ORNL
Materials with triangular and honeycomb lattices are of interest as potential quantum materials due to the possibility of magnetic geometric frustration. Combining the triangular lattice of known structure types with ions with desirable electronic and magnetic configurations could induce exotic ground states, such as a quantum spin liquid. We have identified the distorted honeycomb compound KCo2(AsO4)(HAsO4) as a potential quantum spin liquid candidate. In this talk I will discuss our ongoing investigations into characterizing the properties of KCo2(AsO4)(HAsO4), including the hydrothermal synthesis of polycrystalline samples, X-ray diffraction measurements, magnetic susceptibility measurements, neutron diffraction measurements, and DFT calculations. Magnetic susceptibility measurements suggest a transition to a magnetically ordered state below 16 K. The ferromagnetic-like character in the magnetic susceptibility below the transition suggests that the material is not a simple antiferromagnet. DFT calculations suggest a zig-zag antiferromagnetic order within the [ab] -plane. Neutron diffraction measurements at POWGEN reveal a magnetic ordering below ∼20 K, and refinement of the magnetic structure is ongoing.
Order-disorder transition behaviors in lightweight high-entropy al- loys
R. Feng
ORNL
The much larger compositional space afforded by high-entropy alloys (HEAs) compared to traditional alloys, opens new opportunities to develop high-performance materials. Here the CALculation of PHAse Diagrams (CALPHAD)-based high-throughput computational method (HTCM) is used to screen lightweight HEAs in the Al-Cr-Fe-Mn-Ti system that contain nanoscale L21 precipitates within the body-centered-cubic (BCC) matrix for cost-effective high-temperature applications. The order-disorder transition behaviors and their effects on the microstructures and mechanical properties of these newly-designed lightweight high-entropy alloys (LWHEAs) are understood by in-situ neutron scattering and advanced microcopies, ab-initio molecular dynamics (AIMD), and Monte-Carlo (MC) simulations. The fundamental understanding of the order-disorder transition behaviors of these LWHEAs explains the different microstructural and mechanical responses among them, which provides insights into the discovery of advanced precipitation-strengthened structural materials by the HEA concept.
43 STM/S study of surface-related states and atomic defects on Ba(Fe,Co)2As2
Z. Ge
ORNL
Surface defects, including domain walls and individual atomic defects, can dramatically modify the properties of iron-based superconductors. However, the nature of domain walls and atomic defects on the surface of in-situ cleaved iron-based superconductors has yet to be identified. Here, we systematically investigated the surface defects on low-temperature cleaved parent and doped BaFe2As2 superconductors by scanning tunneling microscopy/spectroscopy (STM/S). STM imaging reveals two types of domain walls on parent and Ni/Co doped BaFe2As2, one as dark trench with missing atoms and the other as straightly aligned bright blobs. Two types of point defects are also identified, one intrinsically from growth or cleaving and the other induced by scanning of the STM tip. Tunneling spectroscopy shows similar surface states at about -200 meV on domain walls and the intrinsic point defects, while on the tip-induced defects there is only one peak at about -120 meV.
Emulating The Cosmic Large-Scale Structure
A. Georgiadou
ORNL
Wide-field sky surveys capture the large-scale distribution of galaxies, while scientists use simulations to capture theory and compare to observations. But, though modern cosmological simulations of dark matter consistently reach the required level of precision, the effect of baryonic physics on cosmological scales is expected to be a source of a much more severe systematic error. To solve the discrepancy between what theorists can model well and what we see, we need to either approximate the baryonic physics and/or accelerate computations by using the most powerful supercomputers. I will present work done to address this challenge by developing statistical frameworks to emulate the large-scale structure of the Universe. I will also include current work on porting cosmological simulation codes to next generation supercomputers.
44 Administration of epoxyeicosatrienoic acid analogs (EET-A) can re- store insulin sensitivity in Cyp2c44 (-/-) mice
K. Ghoshal
Vanderbilt
Aims/hypothesis Insulin resistance is linked with type 2 diabetes and substantially impairs glucose and lipid metabolism. We previously established that global deletion of Cyp2c44, a major epoxyeicosatrienoic acid (EET) producing enzyme, leads to insulin resistance in mice and impaired hepatic insulin signaling. We hypothesized that restoration of insulin signaling in the absence of Cyp2c44 can be achieved by EET analogs treatment. Methods Wild-type and Cyp2c44 (-/-) mice were given the EET analog EET-A (10mg/kg/day in water) or water alone for four weeks. Insulin sensitivity was assessed in wild-type and Cyp2c44 (-/-) mice prior and after EET-A treatment using glucose (GTT) tolerance test. In addition, all mice were given an IVC insulin (5U) injection. Fifteen minutes after, the mice were sacrificed, and liver were harvested for analysis of insulin mediated Akt activation. Insulin signaling was also analyzed in cultured primary hepatocytes from wild-type and Cyp2c44 (-/-) mice treated with insulin (100nm) with or without EET-A (1µM). Gluconeogenic and glycogenic gene expression were also studied in liver by quantitative PCR. Results GTT data suggest a potential restoration of insulin action in Cyp2c44 (-/-) mice after treatment with EET-A for four weeks compared to mice prior treatment. EET-A treatment enhanced insulin-mediated signaling in Cyp2c44 (-/-) mice as demonstrated by increased Akt phosphorylation at S473. In agreement with this finding, we observed Akt-mediated inactivation of downstream Foxo1 and GSK3β as demonstrated by phosphorylation of S256 and S9 of Foxo1 and GSK3β, respectively. Activation of insulin-mediated signaling was detected in liver as well as in cultured hepatocytes from Cyp2c44 (-/-) mice treated with EET-A. The expression of gluconeogenic genes are upregulated in Cyp2c44 (-/-) as compared to WT, which got restored after EET-A treatment. Conclusion Our result indicates that administration of EET analogs can restore insulin signaling in Cyp2c44 (-/-) mice. Therefore, EET analogs may act as a novel therapeutic target in diabetes research.
45 A Metallic Fuel Performance Benchmark Problem Based on the IFR-1 Experiment
I. Greenquist
ORNL
Metallic nuclear fuels are an active area of research and development for use in advanced reactors. Robust, accurate metallic fuel performance models are necessary for the design, safety analysis, and licensing of such reactors. However, metallic fuel performance models require additional development; they are not as mature as ceramic fuel performance models. Oak Ridge National Laboratory (ORNL) has developed a benchmark problem based on the Integral Fast Reactor (IFR)-1 experiment to better gauge the accuracy of existing models, identify high-priority models for development, and quantify the improvements made by future model development. This work included collection of all relevant information on the IFR-1 experiment and used it to develop the benchmark problem. The problem was simulated using the fuel performance code BISON, and the results were compared to post-irradiation examination data from the IFR-1 experiment. A sensitivity analysis was performed on the BISON model to determine the benchmark problem’s sensitivity to uncertainty in the input parameters. The results suggest that BISON’s mechanical models require additional development. Plastic deformation was underpredicted in the cladding, and axial swelling was overpredicted in the fuel. These problems may be related. Furthermore, there was a bias in the temperature which may have been a result of uncertainty in the input parameters rather than an issue with the fuel performance models.
RAPID Analytical Technique for the isotopic analysis of fission and actinide elements
M. Healy
ORNL
Nuclear weapons testing, nuclear fuel cycle operations and medical isotope production produce significant quantities of materials containing trace elemental impurities of non-natural isotopic abundance. Precise and timely quantification of these trace impurities, specifically isotopic abun- dance of fission elements, is key; and to achieve this, fission elements must be elementally separated from isobaric and poly-atomic interferences and ideally, the bulk nuclear matrix. An automated separation–direct analysis scheme has been developed to determine both the concentration and isotopic composition of a suite of elements down to the low picogram level in a complex silicon- based matrix. RAPID (Rapid Analysis of Post-Irradiation Debris) consists of a high-pressure ion chromatography system directly coupled to an inductively coupled plasma mass spectrometer. The RAPID method achieves matrix exclusion and direct online analysis of the elementally separated components, yielding precise isotopic compositions for up to 40 elements in less than one hour per sample.
46 Atomic-scale disordering in weberite-type complex oxides
I. Gussev
UTK
Complex oxide materials, such as pyrochlores and weberite-type oxides are promising candidates for a number of energy-related applications. Due to their enhanced structural stability under harsh operating conditions, they have been proposed as photocatalyst materials in photoelectrochemical cells, matrices for encapsulating nuclear waste, and solid electrolytes for fuel cells. These oxides have been shown to disorder under extreme environments, but despite intensive studies, there is only a limited understanding of their atomic-scale behavior. Neutron total scattering experiments performed at the SNS have been used to study disorder across the RE3TaO7 series. Pair distribution function analysis and Rietveld refinement showed that the nature of the disorder in these materials is more complex than previously thought. While fully ordered Pr3TaO7, Tb3TaO7, and Ho3TaO7 compounds are characterized by an orthorhombic (Ccmm and C2221) structure across all length scales, the disordering of Ho3TaO7, Tm3TaO7 and Yb3TaO7 compositions to long-range defect fluorite (Fm-3m) is not representative of the short-range structure. Interestingly, the local atomic configuration in the disordered materials adopts a similar arrangement found in the ordered compositions. Thus, chemically induced disorder proceeds through rearrangements of sub- nanometer structural domains. The resulting heterogeneous nature of disorder in weberite-type materials appears to be a more general phenomenon as it was also found in other complex oxides for different disordering mechanisms.
CENNS-750: A Ton-Scale Liquid Argon Detector for CEvNS at the SNS
M. Heath
ORNL
First proposed 50 years ago, coherent elastic neutrino-nucleus scattering (CEvNS) allows for a broad collection of fundamental physics studies and has potential applications to nuclear reactor monitoring. Although CEvNS is the dominant neutrino interaction for low energy neutrinos, it remained undetected until 2017 due to the difficult technical requirements: large de- tectors with low thresholds, strong background suppression, and an intense neutrino source. The COHERENT experiment at the SNS has now detected the CEvNS process with two different nuclei: CsI and Ar. Following these first light measurements, COHERENT is planning for next-generation pre- cision CEvNS measurements. To that end, a 750 kg liquid argon (LAr) scintillation detector, CENNS-750, has been designed to deploy at the SNS. This larger detector is expected to see around 20 times more CEvNS events per year than the currently operating LAr detector as well as be sensitive to inelastic charged-current and neutral-current neutrino scattering events and accelerator-produced dark matter. The current status of CENNS-750 will be presented.
47 Investigating the defect-induced changes in the electronic and vi- brational properties of graphitic materials using density functional theory
S. Isbill
ORNL
Owing to their high strength-to-weight ratio, carbon fibers have been used as a steel replacement to improve fuel efficiency in the aeronautical and automotive industries. As a consumer product, understanding the impact of structural defects on the mechanical properties of carbon fibers and how the formation and evolution of defects can be monitored noninvasively is important. Spectroscopic techniques, such as Raman spectroscopy, can be used for this purpose. Although Raman spectroscopy can confirm the presence and describe the nature of defects in some cases, it is an inferential technique, especially in the limit where selection rules break down. In this work, we present a computational investigation of different types of defects in graphite and graphene as analogues for basic structure units of carbon fiber. Using the highly scalable density functional theory code RMGDFT deployed on Summit, the world’s most powerful and smartest scientific supercomputer, we calculated the changes in electronic and vibrational properties caused by two common defects as a first step toward building a more complete understanding of the observable spectral changes induced by specific types of defects in carbon fibers and the overall effect on material strength.
Near-field Imaging of Circular Dichroism in Plasmonic Nanospirals
V. Iyer
ORNL
Optical nonlinearities are playing an increasingly important role in photonics and quantum optical technologies. Nanoplasmonic media can enhance the efficiency of nonlinear processes such as second harmonic generation and supercontinuum generation. Moreover, plasmonic nanostructures allow sub-diffraction manipulation of light, essential for integrated plasmonic technologies. The Archimedean spiral is an asymmetric plasmonic structure that exhibits multiple resonances across a broad spectrum, as evidenced by far-field optical properties and finite-difference, time-domain (FDTD) simulations. Near-field optical characterization with nanometer scale resolution has been used to reveal the different plasmonic modes and their coupling to linearly polarized light, but no previous reports have explored the full polarization state of the cathodoluminescence in order to explore the interactions of circularly polarized light with plasmonic nanospirals. Because nanospirals couple efficiently to circularly polarized light, they have been used to drastically improve properties such as photoluminescence in two-dimensional MoS2. Here, we utilize the newly installed system at CNMS capable of polarization-resolved cathodoluminescence, to uncover near-field interactions with circularly polarized light and relate the handedness of the light to the handedness of the spiral. The detailed understanding of the angular momentum interactions paves the way for improved plasmonic devices based on asymmetric structures.
48 High-performance Vertical Ga2O3 Schottky Barrier Diodes for Power Device Applications
M. Ji
ORNL
Ultra-wide-bandgap gallium oxide (Ga2O3) materials have attracted considerable attention for next-generation power device applications because of their potential advantages of large bandgap (4.6-4.9 eV), superior theoretical breakdown electric field (8 MV/cm), exceptional Baliga’s figure of Merit (BFOM) of >3000 as well as its superior chemical and thermal stability. Recently, β-Ga2O3- based electronic devices such as metal-oxide-semiconductor fieldeffect transistors (MOSFET), fin-array field-effect transistors (FinFETs), and Schottky barrier diodes (SBDs) show excellent device performances with high breakdown voltages, high power operation, and low conduction losses. In high-power applications, large-size devices are needed to provide high forward current while sustaining high breakdown voltages. However, the realization of high-performance Ga2O3- based Schottky barrier diodes has been hampered by high threading dislocation densities in the active region. In this study, we demonstrated high-performance large-size vertical Ga2O3 Schottky barrier diodes with various device sizes on a Si-doped n-type drift layer grown by hydride vapor phase epitaxy (HVPE) on bulk Sn-doped (001) n-type β-Ga2O3 substrate. The devices show high breakdown voltage, low turn-on voltage, and low specific on-state resistance.
49 Mechanistic Understanding of Propane Oxidative Dehydrogenation over Hexagonal Boron Nitride-based Catalysts
X. Jiang
ORNL
Hexagonal boron nitride (h-BN) has recently emerged as an outstanding catalyst for selective oxidative dehydrogenation of propane (ODHP) to propylene (C3H6) with negligible carbon oxides (COx ) formation. Yet, the mechanisms on h-BN are still elusive. A recent work reveals the signifi- cant influence of gas-phase radical chemistry in ODHP. However, there is a lack of experimental evidence; nor has the work focused on the effect of redox VOx and non-redox h-BN interaction on activity and mechanisms. In this work, we successfully revealed the reaction mechanisms over h-BN-based catalysts via combined synchrotron radiation vacuum ultraviolet photoionization mass spectroscopy (SVUV-PIMS) and density functional theory (DFT) calculations. h-BN presents ◦ high selectivity toward C2-C3 olefin production (75%-94%) within 500-600 C, along with C3H8 conversion from 0.3 to 38.2%. We have revealed gas-phase radical mechanisms with the evidenced formation of methyl radicals on both h-BN and BOx /SiO2 catalysts using SVUV-PIMS, a powerful tool to detect gas-phase radicals. Combined with characterization results and DFT calculations, we propose that the reaction proceeds on the BOx moiety over h-BN, and C3H6 is mainly generated through C-H cleavage of C3H8;C1 and C2 products are formed by both surface-mediated pathway and gas-phase reactions involving secondary reactions of methyl and propyl radicals, whereas the surface pathway predominates on h-BN. To improve the low-temperature reactivity of h-BN, VOx was introduced into h-BN (coverage: 0-1 monolayer). V addition can reduce the apparent activation energy (Ea) of C3H8, resulting in enhanced C3H8 conversion. Meanwhile, C3H6 selectivity is well-retained. SVUV-PIMS results indicate similar reaction mechanisms as h-BN. But differently, VOx /h-BN presents more produced NO, suggesting its important role in promoting C3H8 conversion via NO-mediated ODHP in gas phase. In situ XAS results confirm the presence of partially reduced V4+, implying the contribution of redox sites in the observed enhancement in C3H8 conversion.
50 CFD Modeling Supports Developing the Target Segment Conceptual Design for the Second Target Station
M. Kao
ORNL
The second target station (STS) at Spallation Neutron Source (SNS) is designed to operate with a compact solid rotating target, which can withstand high proton beam load (700 kW, 15 Hz) in the tungsten and can produce the world’s highest peak brightness neutron source. The tungsten is hipped with tantalum clad to minimize corrosion. Advanced CFD Models were developed in STAR-CCM+, and multiple cooling channel arrangements were studied to improve heat transfer performance for different proton beam profiles, including normal, off-center, peaked, and diffuse proton beams. The consequences of internal by-pass flows through the potential gap due to manufacturing were also evaluated. Initial evaluations were also conducted for a new open target design in which the side walls for each target segment are removed. The open target design is less prone to fabrication error, easier balancing for disk rotation, and can reduce probability for water leaks. CFD analysis indicates the requirements of flow separators for efficient cooling of the front head of the target.
51 Mechanical Properties and Microstructure of Laser Chemical Vapor Deposition of SiC Fibers
O. Karakoc
ORNL
The effects of chemical compositions and annealing treatment on microstructural evolution, surface morphology and mechanical properties of laser-driven chemically vapor deposited (LCVD) Si71C29 wt.% and Si77C23 wt.% fibers have been investigated for accident tolerant nuclear fuel cladding technologies. Their mechanical, chemical, physical and microstructural characteristics have been assessed along with a range of analytical tools. Results reveal that TEM, SEM and Raman spectroscopy observations are in good agreement that LCVD-derived SiC fibers possess composite microstructure; SiC fiber undergoes crystalline to amorphous transition from center to edge of fiber cross-section. Measured tensile strengths were within the range of 0.9-2.5 GPa range which are among highest reported thus far for SiC fiber commercial alternatives. Tensile strength and surface roughness of LCVD-derived fiber are greatly affected by small percentage of free silicon excess. Free Si excess greatly improved tensile strength of fiber from 1.75 to 2.5 GPa. Outer surface of high purity Si71C29 wt.% are roughened and clustered formation, whereas Si77C23 wt.% has smooth and handleable outer surface. Raman spectroscopy and TEM displays that LCVD-derived SiC has 3C crystal structure with no measurable oxygen and carbon within the microstructure. Annealing treatment at 1200 ◦C for 24 h reduced tensile strength of both fibers while resulting in more homogenous microstructure. Overall, LCVD process promises to afford chemically pure, oxygen and carbon free, ultra strong SiC fibers with small diameters and tailorable surface morphology. The current work establishes fundamental understanding on properties LCVD-derived SiC fibers and a significant step towards understanding microstructure-property relationships relative to market requirements.
52 Physicochemical modeling of dissolution and stability of poorly sol- uble and unstable drugs loading into multilayer soluble polymeric films
M. Khan
Kentucky
Biopharmaceutical Classification System (BCS) Class-II and IV drugs have low aqueous solubility and bioavailability. To overcome the limitations, soluble polymeric drug dispersion films is emerging as a feasible technique, which can side-step and replace current legacy-based process design in the pharmaceutical industries. It also provides the opportunity for a multilayer film-based formulation for a highly scalable and rapidly implementable process with predictive physicochemical modeling. A modeling framework for the design and parameter optimization (polymer diffusivity, solubility, active and barrier layer thickness, area, mass transfer coefficients and relative rate constants) during the formulation of hydrophobic drug-loaded soluble polymeric films was implemented in terms of dosage, release rate and storage stability (self-life) involving dissolution and stability for targeted design requirements in terms of thickness, geometry, order, composition and number of layers. Unsteady-state Fickian diffusion describes both dissolution and stability modeling. During dissolution, the relative rate of water intrusion and polymer erosion from surface coupled with drug diffusion primarily govern the observed release rates, expected for different release mechanisms (immediate/slow). For stability, barrier polymer layer is modeled by diffusion of water/oxygen along with mass transfer (partition) in the surface and interface to achieve < 1% impurity formation within 12 months.
53 Development of Large-Scale Neuromorphic Computing Framework
S. Kulkarni
ORNL
Today’s exponential growth in data and the need to process it efficiently has led to a search for alternate computing paradigms. Neuromorphic computing takes inspiration from biology, where the data is represented in binary spikes, and physical substrate does not suffer from the memory- processor communication bottleneck, leading to a low-power and massively parallel computer. Several research groups and companies that have demonstrated efficient spike-based algorithms and hardware platforms, thus, demonstrating tremendous potential of neuromorphic computing in processing data efficiently compared to existing approaches. However, a prime gap that exists is the ability to scale up these algorithms and platforms, such that a neuromorphic computer can be deployed as an accelerator in high-performance computing (HPC) systems. Having a fast and scalable neuromorphic simulator is a crucial step towards developing and testing these algorithms, and their eventual deployment on neuromorphic hardware platforms. There are several neuromorphic simulators such as Brian, Nengo, NEST, BindsNET, etc., which allow various degrees of scalability and flexibility to run different models of spiking neural networks. As part of this project, we evaluate each of these simulators for their scalability, speed, and flexibility, by creating a suite of test cases in the TENNLab neuromorphic framework. The front-end framework is used to create network architectures to study problems ranging from bio-inspired networks to deep neural networks for machine learning applications. We will further apply the framework to develop algorithms suitable for neuromorphic platform deployment and that can be trained on the hardware and in an online manner. We will also extend these algorithms to HPC problems, such as solving graph algorithms and evolutionary algorithms, hence, demonstrating an end-to-end neuromorphic computer.
54 Resilience Structural Design Patterns Modeling
M. Kumar
ORNL
Resilience in extreme-scale high-performance computing (HPC) systems is a critical challenge. With each new supercomputer generation, component counts in-crease, component reliability decreases, hardware complexity increases and software complexity increases. Recent reports about serious reliability problems also include unexpected issues, such as bad solder, dirty power, and early wear-out. Resilience design patterns offer a new, structured hardware and software design approach for improving resilience. Prior work focused on (1) identifying and formalizing the resilience de-sign patterns in production HPC systems and recent resilience technologies, (2) developing a proof-of-concept prototype for demonstrating the resilience design pattern concept using a fault-tolerant generalized minimal residual method (FT-GMRES) linear solver with portable resilience, (3) creating new, outcome-based metrics for HPC resilience, and (4) developing initial performance and reliability models for resilience design patterns. Recent work extends it in initial performance and reliability models for resilience design patterns by (1) focusing on the Rollback and N-modular Redundancy structural patterns, (2) providing more detailed models that include flowcharts and state diagrams, and (3) offering trade-off models for combining these two patterns for practical resilience solutions.
Thermal Loading Analysis of the Ring Injection Dump
V. Kumar
ORNL
The Ring Injection dump (RID) is one of the three beam dumps in the SNS facility and accepts a fraction of the beam from the ring that is not trapped in the ring during injection. Thermo-fluid modeling of the RID components was performed during the initial design using the software ANSYS CFX in order to characterize the power rating for the RID. From the calculations, the power rating was lowered to 150 kW at 1.3 GeV beam energy, due to concerns regarding the heating of the concrete structure. In lieu of the proton power upgrade of SNS, there was a need to update the calculations focusing on the shielding, and benchmark the model using thermocouple data, installed in the concrete structure. A three stage process was adopted in the latest analysis. Firstly, the old steady state calculations were validated and extended with the latest MCNP source term calculations. Secondly, a transient calculation was performed for the last fourteen years, and sensitivity analyses of key parameters were carried out to benchmark the model with good accuracy. Lastly, an idealized transient cycle analysis was conducted with realistic duty factors to predict the temperature distribution at higher beam powers.
55 Dynamics, Entanglement, and the Classical Point in the Transverse- Field XXZ Chain
P. Laurell
ORNL
We study dynamical and entanglement properties of the S = 1/2 transverse-field XXZ quantum spin chain at T = 0 using the density matrix renormalization group (DMRG). This spin Hamiltonian is relevant to e.g. Cs2CoCl4. As the field strength increases, the spin system passes through two quantum critical points of different universality classes, as well as a classical point. Consequently, the entanglement can be tuned by simply changing the magnetic field. Using DMRG we study the entanglement entropy, as well as entanglement witnesses that can be probed experimentally using inelastic neutron scattering. We contrast the behavior of different entanglement measures, and discuss the feasibility of experimental entanglement quantification in anisotropic spin chain materials.
56 Characterizing a tripartite plant – fungus – bacteria symbiosis
T. Lawrence
ORNL
Ecosystems dominated by the peat moss Sphagnum occupy just 3% of the Earth’s land surface yet store approximately 25% of the planet’s soil carbon as dead recalcitrant organic matter. Sphagnum species are key members of peatland ecosystems where they can account for up to 40% of total ecosystem productivity and together with associated N2-fixing bacteria provide critical nitrogen input to peatlands. Associations between Sphagnum and phototrophic microorganisms were reported more than a century ago describing the presence of cyanobacteria within the dead hyaline cells of Sphagnum. Cyanobacteria associated with Sphagnum fix nitrogen at higher rates than non-Sphagnum associated cyanobacteria, and when in symbiosis N-fixation can occur at low pH. Additionally, SEM imaging has shown a potential role of fungi in the Sphagnum-cyanobacteria symbiosis, revealing that fungal hyphae can envelop cyanobacteria within hyaline cells. Despite the importance of this symbiosis to ecosystem productivity, we lack a basic understanding of how the symbiosis forms, which metabolites are exchanged, and what role, if any, fungi may play in this tripartite interaction. To address these questions, we used cross-feeding studies and spatially resolved metabolic profiling to determine which metabolites are acquired, competed for, or uniquely exchanged among a constructed Sphagnum, cyanobacterium, and fungus symbiosis. Exometabolite profiling from the cross-feeding study identified 278 unique metabolites with 148 being utilized by at least one tripartite member and only six consumed by all three members. Sphagnum and the cyanobacterium only overlap in the utilization of 6 metabolites suggesting little competition between them. Contrastingly, the fungal member utilized 25 and 20 metabolites in common with the cyanobacterium and Sphagnum respectively. Interestingly, the fungal member utilized 41 unique metabolites, the most of any member, followed by the cyanobacterium utilizing 37 and Sphagnum utilizing 13 unique metabolites. Additionally, we were able to identify several metabolites possibly underlying carbon exchange between Sphagnum and the cyanobacterium and the transfer of xanthosine from the cyanbacterium to Sphagnum as a possible source of fixed nitrogen. Furthermore, we identified several sulfur compounds transferred from the fungus and Sphagnum to the cyanobacterium suggesting a potential role of sulfur in this symbiosis.
57 Anions Tune the Self-Assembled Structure of Ionic Oligomers at Buried Liquid/Liquid Interfaces: Implications for Designing Molec- ular Devices
L. Lin
ORNL
Functional oil/aqueous interfaces stabilized by amphiphiles play a crucial role in a range of fields, from phase transfer catalysis, nanomaterial synthesis, and neuromorphic computing, to chemical separations and nuclear waste remediation. Mechanistic understanding of these functions requires direct interrogation of interfacial structures and interactions, which necessitates techniques that are sensitive to the molecular composition and conformation at interfaces. For decades, surface specific vibrational sum frequency generation (vSFG) spectroscopy has been used to study interfacial structures and dynamics but probing these buried interfaces has remained elusive. In the present work, we use vSFG to investigate the self-assembly of an ionic oligomer at buried hexadecane/aqueous interfaces. The oligomer consists of an oligodimethylsiloxane (ODMS) tail covalently attached to a positively charged headgroup that readily adsorbs and self-assembles at the oil/aqueous interface. The presence of salts in the aqueous phase changes the conformation of the tails and is dependent on both anion concentration and identity. For aqueous phases containing low concentrations (100 or 250 mM) of NaCl or NaH2PO4, the ODMS tails exhibit strong vSFG responses, indicating loose packing of the oligomers, whereas at high salt concentrations (500 mM or 1 M), the vSFG intensity precipitously decreases owing to the formation of densely packed oligomer in-terfaces facilitated by charge screening. Remarkably, at aqueous NaSCN interfaces, vSFG signals nearly independent of the ionic strength are observed, indicating a key role for ion pairing and anion surface activity in assembly. Further analysis demonstrates the existence of electrical double layers at oil/aqueous containing NaCl and NaH2PO4 at low ionic strengths, whereas for aqueous NaSCN and concentrated NaCl and NaH2PO4 solutions, ion pairing between the anions and the headgroups is observed. These subtle interfacial interactions, and the balancing act of surface activity and oligomer structure, represent key mechanistic principles needed to tune interfaces for a range of applica-tions and have implications for the design of functional devices.
58 Multimodal Transportation Flows of Crude Oil in the United States
M. Uddin
ORNL
Crude oil is the lifeblood of the modern U.S. economy and helps meet the largest share of the national energy demand. The U.S. has top ten reserves and is the top global producer of crude oil; it imports and exports a huge amount as well. Crude oils are transported from domestic production locations, and ports-of-entry for imports, to refineries. These refineries convert crude oil into petroleum products (e.g., gasoline and diesel) and a component of non-fuel products. Even though the majority of crude oil is transported via pipeline, a significant amount is also transported using other modes, such as water, rail, and truck. To assist the U.S. Department of Transportation (USDOT) decision-makers to understand how and how much crude oil is moved inside the country, this study uses public data to generate multimodal flow estimates at the state and regional levels. Particularly, the study develops a methodology to incorporate data from the Energy Information Administration, the U.S. Army Corps of Engineers, and other sources to generate an origin-destination-mode flow matrix. In addition to USDOT uses, these estimates could be used by other government agencies, as an example, to assess impacts on energy commodity supplies due to natural or man-made disasters.
59 Poster Session 2
Electronic excitations and their impact on point defect diffusion in graphene
D. Lingerfelt
ORNL
The convergent electron beams used in the scanning transmission electron microscopy (STEM) can not only be employed for purposes of imaging, but also for inducing local chemical transformations. Specifically, STEM has been used recently to build atomically precise heterostructures from substitutional silicon defects in graphene, but the mechanisms underlying the defect diffusion processes initiated by focused electron beam are poorly understood. In this presentation, I will introduce our newly developed first principles method for predicting electronic response of materials to point source electric fields emanated by the charged particles comprising the beam, and detail its use to reveal defect-centered excited states of silicon-doped graphene nanostructures. The effect of electron beam-induced excitation to these defect-centered states on the reactivity of the silicon defect will also be explored.
In-situ characterization of the mechanism of laser induced crystalliza- tion from amorphous precursors within a TEM
C. Liu
UTK
Non-equilibrium synthesis and processing enables a wide variety of materials systems with tuned properties. Here we report how a prototype setup allows laser illumination to be coupled into a (scanning) transmission electron microscope (TEM) for real-time observations of non-equilibrium synthesis. Crystallization of amorphous precursors can be accomplished at elevated temperatures by the general process known as crystallization by particle attachment. Characterization of these “building blocks” by high-resolution electron microscopy, as well as first principles modelling, is used to infer valuable information on the time scales and kinetics of the growth processes of these nanomaterials. Graphene and other 2D crystalline layers grown by chemical vapor deposition are utilized as platforms for synthesis, which yielded different microstructures and different kinetics. Electron energy loss spectroscopy (EELS) is utilized to understand the electronic properties and composition of synthetic 2D crystals and their heterostructures in the TEM. In addition, post-growth ADF-Z-STEM measurements permit the characterization of crystal phases, defects and grain boundaries at the atomic scale. These nanoscale measurements to understand the growth mechanisms of crystalline 2D films from amorphous precursors should enable more rapid advancement of laser processing at the macroscale. Work supported by U.S. DOE, Office of Science, BES-MSED and conducted at the CNMS.
60 Solving Optimization Problems with Quantum Computers
P. Lotshaw
ORNL
Quantum computers can theoretically solve difficult computational problems that would greatly impact the DOE missions of scientific discovery and energy security. However, modern quantum computers suffer from limited sizes and uncontrolled noise that limit their performance, making it is unclear how they will provide a useful quantum advantage in the near future. My research is developing near-term applications for quantum computers to solve optimization problems that have an advantage over standard methods. One goal is to look for difficult optimization problems that are relatively easy to solve with a quantum computer, by analyzing the relationship between problem structure and quantum circuit complexity. A second goal is to assist experimentalists in developing a better type of trapped-ion quantum computer for solving optimization problems. For both goals we use modeling and simulation of quantum computer performance to understand errors and how they might be overcome. These efforts will assist in developing modern quantum computers to solve useful and complex problems that are impractical to solve with standard computers.
Dynamic traffic queue-end identification using location-based crowd- sourced Waze user reports
Y. Liu
ORNL
Traffic congestion caused by accidents may spread rapidly upstream and create large speed differentials at the end of queue (EOQ), which could lead to secondary crashes. Previous studies generally use roadside sensor data to detect the end of queue. This study explores the possibilities of crowdsourced location-based data, specifically Waze user reports. It presents a dynamic clustering algorithm and a threshold selection module to connect the location-based reports in real-time and identify the spatial-temporal extent of congestion as well as the end of queue. The proposed method was tested with 34 traffic congestion cases in the Knoxville, Tennessee area. It is demonstrated that the algorithm can effectively detect traffic congestion and identify the end of queue in real-time. The Waze report-based detection is compared to the detection based on roadside sensor data. The results are promising: The EOQ identification time of Waze is similar to the EOQ detection time of traffic sensor data, with only 1.1 minutes difference on average. In addition, Waze reporting frequency is comparable to the reporting frequency of roadside sensor data, suggesting Waze is a valuable complementary source for end of queue detection where no traffic sensors are installed.
61 SAM++: Porting SAM to performance portable C++
I. Lyngaas
ORNL
The process of porting SAM (the system for atmospheric modeling), the cloud resolving model used in the E3SM-MMF (Energy Exascale Earth System Model - Multiscale Modeling Framework), from Fortran code to performant C + + code using a parallel programming is described in detail. In particular, we explain our approach for employing efficient testing of code correctness using an interfacing procedure that uses a F ortran/C + + interoperable framework. Through this porting process, we are able to successfully replicate SAM using a single code base that can execute on various hardware architectures. The implementation of this ported code using GPUs was found to outperform the current implementation of SAM. Beyond this performance improvement, the ported code provides a framework that is compiler independent and more easily extended to future computing architectures.
Polymer upcycling by 2D visible-light-driven photocatalyst loaded with single atoms
X. Ma
ORNL-GO Student
As industry boosts in the recent decades, plastic waste is gradually becoming a severe problem. Most polymers in plastics are hard to degrade like polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), etc. Photocatalyst working under visible light offers a greener and less energy-consuming way to deal with the problem compared with the currently used pyrolysis method and makes more efficient use of sunlight compared with UV-driven ones. Moreover, the idea of upcycling was proposed to call on researchers to add more value to the produced chemicals after degradation. However, to achieve high performance, noble metals are frequently used as cocatalysts, which hinders the industrialization of photocatalytic upcycling by its intrinsic high price. Downsizing cocatalyst from nanoparticles to single atoms has been proposed to tackle this problem. In this poster, I proposed a detailed plan bringing the concepts of single-atom cocatalyst and 2D visible-light-driven photocatalyst together to realize the high-performance photocatalytic upcycling of plastics.
62 Three-way Catalyst Reactivity of Novel High-performance Fuel Blends for SI Engine Emissions Control
S. Majumdar
ORNL
As part of the Department of Energy “Co-optimization of Fuels and Engines” initiative, advanced engines along with high-performance fuels are being developed to reduce petroleum consumption. Above the critical light-off temperature, three-way catalysts (TWC) in the aftertreatment system of light-duty vehicles with SI engines operating under stoichiometric conditions efficiently meet the emissions regulations for deleterious pollutants such as nitrogen oxides (NOx), non-methane organic gases (NMOG) and carbon monoxide (CO). However, during cold-start (below TWC light-off temperature), the regulated pollutants may escape from the vehicle exhaust. To achieve commercialization of advanced engines operating on high-performance fuels, cold-start compliance is imperative to meet the stringent emissions regulations. In the current study, a commercial dual- zone TWC has been hydrothermally aged and fuel light- off measurements have been conducted as per industry-laid guidelines. As real-world fuels are multi- component blends, we examined the fuel chemistry effects of 10-30% (vol.) blends of selected high- performance fuels in a surrogate blendstock for oxygenate blending (BOB) on TWC light-off temperatures. A LabVIEW-controlled synthetic engine exhaust flow reactor system has been used to investigate the light- off behavior of the fuel blends on the TWC yielding very interesting results. We have also investigated the impact of aromatic hydrocarbons on the light-off of the overall fuel blend. In addition, results from TWC light-off measurements of pure blendstocks under conditions relevant to multimode SI-ACI engine exhausts will also be presented.
63 Machine learning-based predictive control of misfire events in spark- ignition engines
B. Maldonado
ORNL
Spark-ignition (SI) internal combustion engines dominate the current light-duty vehicle market. Consequently, increasing the efficiency of SI engines can substantially improve the fuel economy and reduce the impact of the transportation sector on climate change. In certain highly efficient conditions, however, the air-fuel charge presents ignition problems causing sporadic misfires. Nonetheless, predictive control strategies that anticipate such events can ensure complete com- bustion and improve engine efficiency. This DOE EERE funded study uses machine learning (ML) for unsupervised prediction of misfires given experimental engine data. In addition, the Markovian property of the dynamic system under study guarantees that only present information is sufficient to determine the probability of having a misfire in future cycles. Therefore, a cycle-to-cycle predictive control algorithm is presented that utilizes full information of the system at a particular cycle and the ML-based predictor to determine the prediction interval for the combustion event in the following cycle. In order to avoid misfires, the controller injects extra fuel inside the combustion chamber whenever the prediction interval assigns a nonzero probability to future misfire events. A physics-based control-oriented model was used to test the closed-loop performance, highlighting the potential of predictive control for increasing the efficiency of modern SI engines.
64 En-situ Micromechanical Testing of Neutron Irradiated Alloys
K. Mao
ORNL
Iron-chromium-aluminum (FeCrAl) alloys have been selected as one of the candidate accident tolerant fuels (ATFs) claddings to replace Zirconium-based alloys of the current fleet of light water reactors (LWRs). FeCrAl alloys have several advantages such as reasonable irradiation resistance, superior oxidation and corrosion tolerance, as well as good processing and weldability. As a body-centered-cubic (bcc) type alloy, the activation of dislocation slip to which plane is not well defined and the localized strain burst is driven by screw dislocations. After irradiation, a combination of dislocation channeling and strain bursts are affected by irradiation-induced defects. Prior tensile studies of FeCrAl alloys have demonstrated irradiation-induced hardening behavior, but the detailed analysis on the dislocation structure after deformation and the chemical composition have not been fully performed. Due to all these complexities, this study aims to understand the role of irradiation-induced defects on the mechanical response and deformation mechanisms in the FeCrAl alloy system. This work focuses on a FeCrAl alloy of Fe-13.0Cr-5.3Al-2.0-Mo-0.1Si- 0.05Y (wt%). The specimen was irradiated in the Oak Ridge National Lab (ORNL) High Flux Isotope Reactor (HFIR) at ∼282◦C to a dose of ∼7 dpa. Tescan MIRA3 GMH with an electron backscatter diffraction (EBSD) system (Oxford Instruments) was used for scanning electron microscopy (SEM) imaging and transmission Kikuchi diffraction (tKD). A MZ.Sb (Kammrath and Weiss Tech., Germany) miniature 5 kN tensile frame was used for SEM in-situ microtensile test at room temperature with a strain rate of ∼ 10−3s−1. A FEI (now Thermo Fisher Scientific) Versa 3D dual-beam SEM/focused ion beam (FIB) was used to extract FIB lift-outs from both specimens before and after micromechanical testing for transmission electron microscopy (TEM) characterization. Dislocations and loops were imaged by the JEOL JEM-2100F field emission gun scanning transmission electron microscope (FEG-STEM). Chemical composition was mapped by the dispersive X-ray spectroscopy (EDS) in a FEI Talos F200X FEG-STEM.
65 Position-Dependent Response of a Large-Area Superconducting Nanowire Single Photon Detector
C. Marvinney
ORNL-IC Postdoctoral Fellow
Superconducting nanowire single photon detectors (SNSPDs) are a state-of-the-art device for detecting single photons in the field of quantum optics. Typical devices have a small active area, however, large-active-area devices are in demand for the emerging fields of single photon microscopy and free-space quantum communication. For a fiber-coupled, large-area SNSPD, we demonstrate that there is position dependence to the signal readout pulse, with slower rise times originating from the front of the nanowire and faster rise times originating from the back. These results are consistent with a simple model of microwave propagation along the length of the nanowire forming pulse echoes which vary with the origin position of the pulse. This effect is present for both bright counts and dark counts, which allows us to infer that dark counts arise uniformly across the length of the nanowire. Currently, milliKelvin scanning confocal SNSPD experiments are being developed in order to characterize the readout waveform with near-diffraction limited resolution. Combining the preliminary measurements reported here with the planned microscopic device characterization will provide a potential new approach for filtering dark counts or for spectrally resolved single photon detection when diffraction gratings are incorporated with SNSPDs.
Structural signatures of defects in organic framework materials
P. Metz
ORNL
While many metal organic framework (MOF) materials are amenable to crystallization, single crystal diffraction experiments are not always feasible nor universally applicable to MOF use cases (e.g. sorption, sensing, catalysis, etc.) where powders are most commonly employed. In principle, access to high-quality synchrotron X-ray and neutron total scattering data enables nuanced studies of MOF materials in operational conditions, and of local deviations from the average structure. In practice, total scattering analysis of imperfect MOF powders is a significant challenge. We present computed and experimental total scattering data indicating the sensitivity of X-ray and neutron scattering data to common MOF defects including point defects, layer disorder, and static position disorder. Examples include investigations of defective zeolitic imidazolate framework (ZIF-8) specimens, and the UiO-66-derived RE-DOBDC MOF (Re = Y, Eu, Tb, Yb, DOBDC = 2,5 dihydroxyterepthalic acid).
66 Magnetic Switching in Weyl Semimetal-Superconductor Heterostruc- tures
N. Mohanta
ORNL
We present a new switching mechanism that utilizes the proximity coupling between the surface spin texture of a Weyl semimetal and a superconductor, in a Weyl semimetal/superconductor/Weyl semimetal trilayer heterostructure. We show that the superconductivity in the middle layer can be fully suppressed by the surface spin texture of the Weyl semimetals in the presence of an external magnetic field, but it can be recovered again by only changing the field direction. The restoration of the middle-layer superconductivity indicates a sharp transition to a low-resistance state. This sharp switching effect, realizable using a Weyl semimetal because of its strong spin-momentum locking and surface spin polarization, is a promising avenue for novel superconducting spin-valve applications.
Role of hydride and hydroxyl groups in Acetylene Semi-hydrogenation over Ceria
J. Moon
ORNL
Ceria has been used as a hydrogenation catalyst especially in selective alkyne hydrogenation, but the reaction mechanism remains unclear. In this study, in situ inelastic neutron scattering (IR) and Infrared spectroscopy (DRIFT) have been used to show the catalytic role of cerium hydride (Ce-H) and hydroxyl (OH) groups in acetylene hydrogenation over ceria surface with different degree of reduction. For oxygen treated surface, the bridged-OH group is the reactive H species to add into acetylene to release the produced ethylene. A self-hydrogenation route of acetylene is also possible on the oxidized surface. Over the H2-treated surface, the hydride is more reactive when it coexists with OH species and can lead to strongly di − σ − bonded species that could deactivate the catalyst. A moderately reduced ceria surface (prior to the formation bulk hydride) appears to be selective for acetylene hydrogenation without leaving noticeable surface bound species. The results from this study not only demonstrates that hydride is actively involved in the hydrogenation reaction over ceria but also provides design insights for active, selective and stable ceria-based catalysts via the control of the density of oxygen vacancies.
67 Carbon Utilization: Electrochemical Approach Using Novel Catalyst and System Integration
D. Moreno
UTK
The environmental footprint from power generation can be mitigated by capturing emitted carbon dioxide (CO2) and converting it to value-added fuel sources. A multitude of different fuels can be produced from CO2 depending on the chemical reaction catalysts. Typically, these pathways can be developed electrochemically, or through hydrogenation. In recent years the electrochemical reduction of CO2 has grown exponentially, as it has shown potential to decrease atmospheric pollution and provide an additional means of on-demand electricity storage. Formic acid (FA) in particular has industrial applications such as in fuel cells or as a hydrogen storage medium, and requires a lower thermodynamic energy input than any other fuel produced for electrochemical CO2 reduction. However, product selectivity remains a challenge for conventional electrocatalysts, making FA production efficiencies above 50% difficult. To address the challenge of catalytic selectivity, UK CAER employs enzymatic catalysts to facilitate the FA production and minimize unwanted byproducts. Our process couples the catalyst with a charge mediator which is necessary to shuttle electrons, and an electrolyte pH buffer to prevent the catalyst from degrading. Presently, production efficiencies have approached 60% at a rate of over 10 mM FA/hour. System design considerations (flow rate, bulk volume) will also be discussed.
Tungsten nanofuzz
D. Morrall
ORNL
Understanding the plasma-material interactions in tungsten is a key area of research for future fusion reactors. The divertor of a tokamak will be subjected to extremely high heat loads and irradiation as it comes into contact with the otherwise magnetically contained plasma in order to remove waste products. Researchers have previously noticed a surface feature in tungsten after exposure to He plasma under certain conditions (between 1000 – 1600K). This surface feature is actually a large number of nanosized (4-50 nm diameter), tree branch-like structures known as nanofuzz. This nanofuzz drives scientific research into answering the question of how the performance of a fusion reactor is affected. In order to answer this large scientific question, it is broken into several other scientific questions such as: What exact conditions cause the formation of nanofuzz? How does this effect plasma stability? Is there a possibility of plasma contamination or retained tritium? In this short talk I will present current and ongoing research that attempts to answer some of these questions.
68 Microbial community reassembly following species gains and losses
J. Moore
ORNL
Species gains and losses in ecological communities are inevitable given on-going global changes. Microbial species gains and losses could change community structure and function due to extensive microbial interaction networks. Dominant and rare microbes may be differentially sensitive to species gains and losses because of their degree of specialization within interaction networks. We simulated microbial community reassembly following dominant or rare species removals in a mock forest soil microbial community. We hypothesized that alteration of dominant species would have a larger impact than rare species on community structure. Our simulations suggested that removing a rare species that was typically rare caused no change in dominant member relative abundance, and about one-third of the rare microbiome shifted relative abundance. However, removal of a rare species that was sometimes dominant, implying the species has traits conferring a competitive advantage, increased abundance of 80% of the dominant species altered relative abundance of nearly half the rare microbiome. In sum, microbial community structure was more sensitive to changes in rare members than dominant members. Our ability to predict microbial community structure is important to predicting functions mediated by microbes under changing environmental conditions.
Lattice strain metrology in catalyst nanoparticles through 4D-STEM
D. Mukherjee
ORNL
Platinum group metal nanoparticles are commonly used as electrocatalysts. Among the multiple approaches available for tuning catalyst performance, lattice strain is regarded as one of the most promising. However, bulk strain measurement techniques like X-Ray diffraction do not work at nanoparticle length scales, while ADF-STEM (Annular Dark Field - Scanning Transmission Electron Microscopy) strain measurement techniques can give erroneous results owing to microscope and particle instabilities. Here we demonstrate the use of 4D-STEM to measure strain in such systems. In 4D-STEM, two-dimensional electron diffraction patterns are captured for a two-dimensional scanning field of view, thus giving rise to a four-dimensional dataset. For these experiments, the electron beam size was made to be larger than the unit cell sizes of the particles – this thus results in diffraction patterns where the lattice spots do not overlap. The lattice spots in every diffraction pattern are then subsequently located to calculate the unit cell parameters for every scan position, allowing us to measure the lattice parameter evolution across the entire field of view, from which strain can be calculated. However, 4D-STEM datasets are significantly larger than conventional electron microscopy datasets and requires robust data analysis routines. Python based software developed for strain analysis from 4D-STEM datasets will also be discussed.
69 Enabling Exascale Quantum Circuit Simulation for XACC with Ex- aTN
T. Nguyen
ORNL
As the experimentally-realizable quantum program size scale, there is a pressing need for scalable and flexible classical simulators capable of extracting expectation values from large quantum circuits to validate experimental results. Thanks to not having the exponential memory scaling limitation like its state vector based counterpart, tensor network theory provides a promising foundation for large-scale quantum circuit simulation. In this work, we develop a new back-end for TNQVM, which is the quantum circuit simulator of the eXtreme-scale ACCelerator (XACC) framework, based on the ExaTN tensor processing library. We can represent quantum circuits both exactly as fully-connected linear tensor networks or approximately as matrix product state tensors, which further enhances the versatility and scalability of the implementation. Thanks to ExaTN’s built-in state-of-the-art tensor contraction optimizers, an optimal numerical computation strategy is derived for each quantum circuit instance, hence fully harnesses the available classical computing resources. The combination of XACC programming front-end and ExaTN numerical back-end has created an end-to-end virtual quantum development environment that can scale from laptops to future exascale platforms. We demonstrate the utility of our newly-developed TNQVM- ExaTN quantum circuit simulator through the seminal quantum circuit sampling examples, which demonstrated quantum supremacy in recent experiments.
Understanding Corrosion Mechanisms of Ni-Cr Alloys Exposed to Molten Fluoride Salts
C. Parker
ORNL
Generation IV nuclear reactor designs include molten salt reactors (MSRs) due to their greater passive safety features when compared to previous generation reactors. In these reactors, molten fluoride, and less commonly chloride, salts are either fuel bearing or simply heat transfer fluids. Controversy exists over the mechanisms of corrosion experienced by Fe-Ni-Cr and Ni-Cr structural alloys, especially surrounding current testing methodology. Static molten FLiNaK salt testing performed at 700 ◦C for 500h of model Fe-16wt.%Ni-16%Cr and Ni-16%Cr alloy coupons in molybdenum capsules were performed, with some capsules including a quartz galvanic separator between sample and capsule wall. The next phase of testing will include flowing FLiBe thermal convection loop experiments with a thermal gradient between 550-650 ◦C with in situ electro- chemical measurements to study corrosion of the Fe-Ni-Cr alloys in a more dynamic environment. Electrochemical measurements will track metallic impurity content in the salt, allowing for correla- tion of material loss to corrosion measurements made after exposure. This research was supported by the U.S. Department of Energy, Office of Nuclear Energy, Molten Salt Reactor Campaign and the U.S. Nuclear Regulatory Commission.
70 Predicting the phase stability of high entropy oxides
K. Pitike
ORNL
High entropy, multicomponent systems are interesting due to the role that cation disorder may play in defining their mechanical, magnetic, reversible energy storage properties, etc. Within the class of high entropy oxides; rocksalt, fluorite, spinel and perovskite phases have all been recently synthesized. Complementing these endeavors, the current work explores a method for calculating the stability of high entropy oxides – compounds in which one cation-site is randomly and equally occupied by five chemical species – through a collaborative computational and experimental efforts. We construct a nearest neighbor (NN) model from enthalpies of mixing of end member oxides and binary oxide mixtures – in their respective potential stable phases – estimated through DFT calculations. The candidates for the high entropy oxides are predicted from the configurational landscapes of the five component oxides, estimated through Monte Carlo simulations using the NN model. Our approach allows us to evaluate potential impurity phases thereby making realistic predictions of novel multicomponent oxides that can be synthesized.
One for all: Imaging complex biological systems using a multimodal nonlinear optical microscope
U. Premadasa
ORNL
Biosystems are influenced by environmental factors and the complex interactions among their participating organisms. Characterizing these systems requires the ability to correlate spatial and temporal organization with local environmental conditions at relevant scales. Therefore, the development of bio-imaging techniques to visualize the spatial distribution of molecular species and their complex structures becomes essential in linking molecular-scale information to macroscopic biological phenomena. The combination of different imaging modalities in a single platform offers the advantage of obtaining and correlating information that is not available using only a single modality. The integration of coherent anti-stokes Raman scattering (CARS), two photon fluorescence (TPF), second harmonic generation (SHG), and sum frequency generation (SFG) modalities in the same platform yields spatially co-registered images which reports on different chemical and structural aspects of biosystems, spanning from pollen grains to bacterial cells. The combination of femtosecond light sources with a total internal reflection (TIR) excitation geometry provides sufficiently strong laser fields to drive higher-order nonlinear optical processes over large excitation areas without damaging the sample, while providing complete images in a single exposure. Our results highlight the importance of leveraging complimentary imaging strategies to differentiate spatially and temporally evolving processes in these complex biological systems.
71 Genome-resolved metagenomics enables fine-resolution assessment of peatland microbial communities and methanogen processes
E. Johnston
ORNL
The Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment - where modified open-top chambers ∼13 m in diameter are used to simulate increased temperatures ◦ (+0, 2.25, 4.5, 6.75 and 9 C) and elevated CO2 in a carbon-rich peatland ecosystem in northern Minnesota - is expected to lead to various alterations in peatland microbial communities and their biogeochemical processes. However, connecting microbial traits to measured processes is often challenging in environmental systems due to their high diversity and complex functional attributes. In this effort, peat communities representing 1, 2, and 4 years after onset of experimental warming were assessed with deep shotgun metagenomic sequencing. Through a combination of sequence assembly and binning techniques, we have recovered ∼450 unique microbial genomes representing up to 90% of DNA sequences from intermediate and deep peat layers, allowing for a unique opportunity to advance beyond the more traditionally applied method of assigning function to small DNA fragments. Our findings demonstrate that individual MAGs are shown to exhibit strong depth- dependent abundance and gene content profiles, consistent with past studies and known physical and chemical gradients in the peat profiles. Through a novel multi-omics approach, we are linking transcriptional profiles of dominant methanogen populations to metabolites involved in distinct methanogenesis pathways and CH4 emission rates. Through a series of microcosm experiments, we are also investigating peat methanogens capable of a novel mode of methanogenesis using methoxylated aromatic compounds (MACs). Our findings indicate that MAC methanogenesis is an important, understudied process in terrestrial environments given that peat organic material is rich in MAC substrates and that peatlands are expected to be a major CH4 source with ongoing climate warming. Future efforts will be able to leverage these microbial community data to track changes in MAG abundance with treatments and, in collaboration with other SPRUCE site investigators employing other ‘omics methods and detailed biochemical analyses, to model microbial physiological responses in situ.
72 Effect of water vapor and composition on oxidation lifetime of alloys 625 and HR120 foils between 650 and 800◦C.
M. Romedenne
ORNL
Fe-based alloys are typically employed in heat exchanger components for combined heat and power generation systems. However, operating temperatures above 650◦C are desired to improve efficiency of these applications requiring the use of Ni-based alloys (e.g. alloy 625), which typically form a protective Cr2O3 scale. The ability to maintain formation of a protective Cr2O3 scale depends on an interplay of different processes (loss in wall thickness, subsurface Cr depletion, Cr2O3 volatilization). Foil specimens of Fe- and Ni-based alloys were oxidized in dry and wet air for up to 30,000 h at 650, 700 and 800◦C. Recuperator foils exposed for up to 100,000 h at about 650◦C in real engine conditions were also analyzed. The impact of composition, temperature and gas flow rates on Cr depletion and loss of wall thickness of the foils will be discussed with an oxidation kinetics model and coupled thermodynamic-kinetic diffusion calculations.
Friend or Foe? Deciphering microbial communication that influences community structure and function.
T. Rush
ORNL
Lipochitooligosaccharides (LCOs) are signaling molecules involved in plant growth, development, and colonization with symbiotic microbes like rhizobia bacteria and mycorrhizal fungi. Recently, LCOs were found to be ubiquitously produced by most fungi, including human and plant pathogens. This discovery has changed our perspective on the potential roles of LCOs. The objective of our project is to determine if LCOs are used as a vetting process between microbes within the rhizosphere soil. Our hypothesis is that microbes associated with plants (endophytes, symbiotic, or pathogenic) will deter non-plant associated microbes away from the rhizosphere by using communication signals such as LCOs. To test this hypothesis, the impacts of exogenous LCOs on the fungal behavior of the opportunistic human pathogen, Aspergillus fumigatus, and the fungal-symbiont, Laccaria bicolor were assessed. We investigated the fungal changes through physiological, metabolomic, and transcriptomic profile analyses. Our results indicate that LCOs act as putative biotic stress factors on A. fumigatus. Conversely, LCOs act as a beneficial element in Laccaria bicolor. Thus, this study suggests that besides symbiosis establishment with plants, LCOs could play a different role in fungi, which is the regulation of their competitive behavior with nearby fungi within the microbiome. Those results expand our knowledge on how microbial interaction occurs to protect human health and the environment through a multi-disciplinary network within the ORNL system.
73 Witnessing Entanglement in KCuF3 using Neutron Scattering
A. Scheie
ORNL
Many-body quantum entanglement is foundational to quantum condensed matter, but it is very difficult to measure in solid state systems. Here we present a study of different entanglement witnesses used to directly extract quantum entanglement from inelastic neutron scattering data. As a test case, we use inelastic scattering on 1D Heisenberg spin chain KCuF3, which is known to exhibit quantum critical behavior, to extract quantum fisher information, two-tangle, and one-tangle. Comparing these results to an idealized experiment with theoretical simulations, we find that the experimental quantum fisher information matches the theoretical values. This demonstrates that neutron scattering is a practical way of quantifying entanglement in real spin systems.
High temperature cyclic loading behavior of novel Fe-Ni-Cr alloy
S. Shukla
ORNL
Increase in the operating temperature of the internal combustion engine has the capacity to increase the fuel efficiency of the passenger vehicle. Hence, there is an ever-growing demand for development of materials that can not only be operational at projected temperatures but also be economically sustainable. In this regard, the current study investigates high-temperature fatigue properties of novel Fe-Ni-Cr based superalloy. The wrought alloy was subjected to high cyclic fatigue testing at 800 and 900 ◦C and the microstructure before and after the fatigue testing was analyzed via SEM and TEM. An increase in the γ’ size of the after high-temperature fatigue testing was observed, which followed the LSW theory of Ostwald ripening. Additionally, potential crack initiation sites (such as precipitate free zones, oxides) were also evaluated via fractography and EDS analysis. The research was sponsored by U.S. DOE, Office of Fossil Energy, Office of Energy Efficiency and Renewable Energy.
74 High temperature calcination products of UO2F2
T. Spano
ORNL
Uranyl fluoride (UO2F2) is the hydration product of UF6, an important intermediate in the nuclear fuel cycle. To examine the thermal stability of UO2F2, samples were calcined for 1 hour at a range of temperatures and monitored for chemical and structural transformations using a variety of analytical techniques. After cooling to room temperature, powder X-ray diffraction and Raman spectroscopy were implemented to examine bulk structural and vibrational spectroscopic changes in UO2F2 calcination products, respectively. Bulk and point elemental analyses were conducted using energy dispersive X-ray spectroscopy coupled to a scanning electron microscope (SEM-EDS) which was also employed to examine differences in sample morphology as a function of firing temperature. Lastly, high-sensitivity ion ratios were determined via nanoscale secondary ion mass spectrometry (nanoSIMS). Preliminary results suggest that samples prepared at lower temperatures do not undergo complete fluorine loss as evidenced in chemical analyses from SEM-EDS and NanoSIMS. This observation is confirmed by the presence of characteristic Raman shifts that are consistent with UO2F2 environments. Genome Wide Association Time-Series Studies to find Temporal Cli- mate Adaptation in Poplar Trees
J. Streich
ORNL
We created a time-series aware association approach called GWATS (Genome Wide Association Time-series Studies) to detect climate adaptive alleles. GWATS involves running a GWAS analysis using time-series phenotype data, in this case for each day of the year. BioClim has been an ideal data series for species distribution modeling and finding adaptive alleles but lacks a true seasonal component and leaves most of each seasonal period unexamined. Instead, from raw monthly climate data, we interpolated 365 daily values of 71 climate/environment layers in the 490 locations where the 970 Populus trichocarpa individuals of our GWAS population were sourced. GWAS was performed for each climate variable on each of 365 days using ∼10M genome-wide SNPs. Geographically isolated alleles tend to coincide with adaptive alleles making them difficult to distinguish from false positives. However, true positive p-values become distinct from false positives by using a Fourier Transform to analyze co-variate variation and output similarity matrix calculations across the time-series. Further, using a machine learning algorithm called iRF (iterative Random Forest) we can filter complex climate phenotypes into epistatic interactions across multiple suites of alleles ranging as high as seven or more orders of epistasis. Using GWAtS we detected hundreds of candidate climate adaptive loci for Solar Radiation Stress, Precipitation Stress, Temperature Stress, Drought Stress and many more.
75 Deciphering the functions of PtLecRLKs in Plant-Microbe Interac- tion
Y. Sun
ORNL
Plant-Microbe Interactions (PMI) are critical environmental factors that affect the global agro- economies. Identifying the key players mediating different PMIs and then utilizing them to maximize host fitness have been a crucial research topic for plant biologists. Plant lectin receptor- like kinases (LecRLKs) are believed to play essential roles in mediating plant-microbe interactions. Through genetic mapping, resequencing and molecular validation, we have demonstrated that a G-type LecRLK mediates the symbiotic interaction between Populus and Laccaria bicolor. Via genome-wide association mapping and transcriptomics analysis on Populus trichocarpa-Sphaerulina musiva interaction system, we have discovered a G-type LecRLK conferring host resistance, and an L-type LecRLK associated with the host susceptibility to the invasive fungi. To have a broader understanding and application of these LecRLKs, we are trying to clarify the ligands these LecRLKs recognize through lectin-binding assays using purified PtLecRLK proteins and fungal cell wall fractions to detect their binding specificity. Second, we aim to unravel the molecular mechanisms they employ to regulate host-microbe interactions through first constructing a Populus yeast two-hybrid cDNA library to identify target proteins of these PtLecRLKs and then analyze the transcriptome profile of Populus tissue incubated with these fungi to identify the key regulators in these pant-microbe interactions.
76 Effects of Hydrocarbon Structure on Adsorption Energetics on BEA Zeolite
C. Thomas
ORNL
Despite continual advances in the field of low temperature oxidation catalysts, cold-start emissions of hydrocarbons remain a significant challenge for automotive vehicles. Hydrocarbon traps have proven to be a promising technology for mitigating the effect of low temperature hydrocarbon emissions. They work by adsorbing hydrocarbons at low temperatures, when the catalyst is inactive for hydrocarbon oxidation, and releasing them at higher temperatures, once the catalyst becomes active. These traps are zeolite based, usually SSZ-13, ZSM-5, or BEA, and often they are ion exchanged with Pd. Previous work has shown that these traps can be effective for mitigating the impact of cold-start emissions. However, work to date has not examined the effect of different functional groups on the storage behavior of the hydrocarbon traps. In this work, the isothermal storage behavior of different hydrocarbons on a model BEA zeolite hydrocarbon trap is investigated. The hydrocarbons used are ethanol, m-xylene, 1-octene, iso-octane, and n-octane. These hydrocarbons represent some of the most prevalent types of hydrocarbons in gasoline while maintaining a constant carbon number of 8 with the exception of ethanol, which is included because of its prevalence in gasoline and exhaust. This allows us to determine the energetics of adsorption and how those energetics change based on hydrocarbon structure. These insights will be invaluable for future modelling efforts on hydrocarbon traps.
Quantum Monte Carlo Forces for Heavier Ions: A Benchmark Study
J. Tlihonen
ORNL
Computation of forces has been an essential challenge with continuum Quantum Monte Carlo methods for the past two decades. Reliable forces make for a central physical observable, but also an accurate and efficient means for relaxation of complicated atomic structures. The main challenges for QMC force estimators are their formally infinite variance and inclusion of explicit and implicit derivatives, the Pulay terms. Well-established techniques have been and are being developed to mitigate these problems. However, their nature and limitations have been largely unexplored, regarding heavier elements and the inevitable compromises of large-scale simulations. Here we present how various systematic errors and statistical performances of QMC forces scale with the effective valence charge. We use well-established, Pulay-corrected, zero- variance estimators for Variational and Diffusion Monte Carlo simulations, including a tail- regression estimator to control the infinite variance problem. We compute QMC forces in selected dimers, including transition metal oxides, and discuss, e.g., consistency of the forces with experiments and the potential energy surface. Furthermore, we consider the intrinsic variances of the QMC forces and their scaling with Zeff, enabling cost analysis and projections to larger applications.
77 Tailoring the surface chemistry and encapsulation of therapeutic agents in lanthanide vanadate and poly(lactic-co-glycolic acid) nanoparticles for nanomedicine
M. Toro-Gonzalez
ORNL
Nanoparticles are promising platforms to deliver diagnostic and therapeutic agents because they can be designed to specifically target cancerous tissue and minimize leakage of their payload into surrounding healthy tissue. There is much interest in developing nanoparticles for targeted alpha therapy to minimize the relocation of radionuclides from the target site, one of the major challenges when using radioimmunoconjugates. We have shown that lanthanide vanadate nanoparticles can be developed with a high encapsulation of 223Ra and high retention of its decay daughters, 211Pb and 211 223 223 Bi. Tailoring the synthesis of La( Ra)VO4 nanoparticles resulted in a Ra radiochemical yield 223 > 90%, whereas the leakage of decay daughters was < 1% in PBS. La( Ra)VO4 nanoparticles were modified with different stabilizing agents having carboxylic or phosphate groups to enhance their stability and for further functionalization. Nanoparticles can also be designed for multi- modal therapy and imaging by combining radionuclides, toxic chemotherapeutic drugs, and fluorophores within them. Poly(lactic-co-glycolic acid) nanoparticles were assessed as multi-modal platforms by encapsulating fluorescein and surrogate metal salts. It has been observed that the encapsulation of both organic and inorganic compounds can be enhanced by tailoring their synthesis parameters. Organic and inorganic nanoparticles are promising and versatile multi-modal platforms for nanomedicine applications.
Movements of Municipal Solid Waste in the United States
M. Uddin
ORNL
Municipal solid waste (MSW), commonly known as garbage or trash, is generally produced from homes, schools, hospitals, and businesses, and consists of everyday items that we use and then throw away (e.g., containers, packaging, furniture, clothing, and newspapers). According to the Environmental Protection Agency, a total of 268 million tons of MSW was generated across the nation in 2017. MSW is typically disposed of in landfills and, to a lesser extent, processed in waste-to-energy and resource recovery facilities. Oftentimes, the MSW is transported from origin counties to destination facilities over many miles and across multiple states. Due to its volume and potential environmental impacts (e.g., spills, leakage, and contamination), it is important for policy analysts, planners, and decision-makers in the state and regional agencies to understand how, and how much, MSW is transported across the country. To this end, this study develops and applies a methodology to generate a county-to-county MSW flow matrix using available state solid waste management reports and datasets, as well as integrating other supplemental information. The generated flow estimates could be used by federal, state, and local agencies to better manage MSW, which could in turn help achieve environmental sustainability.
78 RNA-based countermeasure against the CRISPR/Cas9 gene-editing tool
M. Vergara
ORNL
The simplicity and flexibility of CRISPR/Cas offers unprecedented opportunities to rewrite genomes. However, access to this technology introduces risks like unintended or unwanted genomic alterations that may not be detected until after their effects are irreversible. Intentional Cas9 based genome engineering can also lead to undesirable off-target effect, unexpected on-target effects and cellular toxicity that may constrain its utility. A means of safely and reversibly controlling the activity of CRISPR tools, understanding and mitigating the risks associated with rapidly developing CRISPR/Cas technologies in mission relevant crops and microbes is of interest to the DOE. The current technology for limiting CRISPR/Cas9 genome editing is predominantly based on anti-Cas9 proteins. However, their utility in genome engineering application is limited. Therefore, a need exists for the development of a readily applicable and adoptable method for Cas9 inactivation. As part of this project, we have developed an RNA based CRISPR countermeasure that adopts the target sequence flexibility of CRISPR/Cas9 to self-target and self-destruct. We have incorporated this countermeasure into prokaryotic and eukaryotic genomes and developed a fluorescence-based assay to report on Cas9 activity. Additional work is underway to further elucidate the efficacy of Cas9 inactivation using transcriptomic and proteomic profiling.
79 Genomic-scale modeling of the interaction among the bacteria iso- lated from Populus deltoides
J. Wang
ORNL
Microbial communities are commonly colonizing throughout plant rhizosphere and endosphere, and they are responsible for a wide range of plant-microbe and microbe-microbe interactive processes. The investigations focusing on the plant-associated microbial communities have clarified the selective effects by the plant hosts to their rhizospheric and endospheric-inhabiting microbial members. However, how the microbial members contribute to shape the microbial community is still not well assessed. The computational systematic analysis can give mechanistic insights by network reconstruction which is able to represent interspecies metabolic interactions. In this study, 10 bacterial strains isolated from Populus deltoides rhizosphere and endosphere were constructed in a synthetic microbial community. The Kbase platform was applied to reconstruct the community-level model and elucidate the main metabolic processes involved in shaping the microbial communities. Whole-genome sequences of individual microbes were merged into a compartmentalized metabolic model with boundaries among individual strains. Flux balance analysis was used to explain the metabolic profile in microbial community and depict the interactions among individual microorganisms through metabolic exchanges. The disclosure of interactive mechanisms among plant-associated microorganisms will broaden the fundamental insights into the strategies about how to engineer a microbial community which will provide potential to increase plant growth and disease resistance.
On the universality of the variational quantum eigensolver frame- work
Z. Webb
ORNL
Hybrid quantum algorithms are a framework in which a quantum process parameterized by classical values is run on a given input. The output of the quantum algorithm is then run through a classical optimizer circuit, which updates the parameters of the quantum circuit. This process is repeated until some limiting behavior of the quantum circuit is achieved, and the framework output some function of the measure quantum output. In this work we show that if the parameterized quantum circuit is sufficiently general, then a specific type of hybrid quantum algorithm known as variational quantum eigensolvers are as powerful as a general quantum computer. In particular, we show how to encode the evolution of a general quantum circuit in the optimal values of a particular variational quantum eigensolver circuit. Moreover, we also show that the classical optimizing circuit is guaranteed to find this optimal set of parameters.
80 Visual Analytics for Exploring Highway Traffic Dynamics using Inte- grated Sensor Data
H. Xu
ORNL
The successful management of urban transportation systems becomes a complex effort that requires the replication and visualization of the interconnected traffic dynamics occurring at different spatial scales that describes both regional mobility patterns and lane-level behaviors. A solid understanding of these dynamics can effectively inform transportation planners about the traffic demand and performance of roadway systems, as well as help them develop realistic and sustainable traffic solutions. In this paper, we envision a web-based situational awareness tool for emulating historical and real-time traffic flows in large urban areas. Relying on mobility data acquired from a network of discrete sensors, the tool is optimized to (1) construct continuous traffic flow and interpolate vehicle positions alone the freeways using general-purpose graphics processing units, (2) visualize smooth vehicle movements in a web map using a Bézier curve-based representation of trajectories and client-side GPU-accelerated technologies, and (3) help users visually explore the emulated traffic dynamics and their interconnections from the microscale to regional scale using a combination of linked geo-visualizations. Based on the level of detail techniques, an innovative geo-visualization is devised to visually connect the lane-level traffic conditions and directions at the mesoscale using an animated strips-network with a modified kernel density map that color-code the magnitude of vehicle congestion and density at the regional scale. A case study is provided to demonstrate the emulation of interconnected traffic dynamics in Chattanooga, Tennessee, by visualizing how traffic conditions and mobility patterns at both mesoscale and regional scale respond to the occurrence of traffic incidents at the microscopic scale.
Strain Evolution and Grain Boundary formation in the Coalescence of Two-Dimensional Crystals
Y. Yu
ORNL
The evolution and role of strain around grain boundaries (GBs) in two-dimensional (2D) monolayer crystal coalescence during chemical vapor deposition (CVD) growth are studied. The polarization resolved second harmonic generation and Raman mapping are used to characterize the strain. Atomic resolution STEM imaging is used to characterize the GB atomic structures. Reactive, force field molecular dynamic simulations are implemented to reveal the atomistic mechanisms of GB formation at different twist angles. It is found that the strain development and GBs formation are determined by misorientation angles of the merging crystals. The mechanism is consistent with established GB energy and dislocation migration theory developed for 3D crystals, but manifested itself in 2D crystals. Our findings suggest that tailoring strain during 2D crystal growth could enable tuning the GBs properties.
81 Engineering Colossal Linear Magnetoresistance in High Mobility SrNbO3 Thin Films
J. Zhang
ORNL
The change of electrical resistance in response to a magnetic field, i.e. magnetoresistance, is an uncommon property, especially to non-magnetic materials. The famous colossal magnetoresistance (CMR) in the manganite perovskites originates from spin-dependent electron delocalization. However, in highly mobile metallic systems with a carefully chosen Hall angle, electrons follow “guiding center” trajectories, giving rise to similar macroscopic behavior. Informed by this guiding center model, we engineer CMR in high-mobility nonmagnetic perovskite thin films. As electrons feel disorder before being scattered, distortion of the current path mixes Hall resistivity into longitudinal resistivity, creating a non-saturating linear magnetoresistance. We show that by tuning the relative strength between the Fermi energy and disorder potential, the tangent of the Hall angle can be brought to unity, serving as the key ingredient to induce extremely large non-saturating MR.
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