Physics Commons^™

Glacial-Interglacial And Millennial-Scale Changes In Nitrous Oxide Emissions Pathways And Source Regions, J. A. Menking, J. E. Lee, E. J. Brook, J. Schmitt, L. Soussaintjean, H. Fischer, J. Kaiser, A. Rice

Physics Faculty Publications and Presentations

During the transition from the Last Glacial Maximum (LGM) to the Holocene, the atmospheric N2O mole fraction increased by 80 nmol mol−1. Using ice core measurements of N2O isotopomer ratios, we show that this increase was driven by increases in both nitrification and denitrification, with the relative partitioning between both production pathways depending on the assumed isotopic end‐member source signatures. Similarly, we also attribute a 35 nmol mol−1 N2O mole fraction increase during the Heinrich Stadial 4/Dansgaard Oeschger 8 (HS4/DO8) millennial‐scale event to increases in both N2O production pathways. In contrast, the 25 nmol mol−1 N2O mole fraction decrease during …

Dripdrop: Systems Engineering For Hemodynamic Modeling, Ceana Chrissylee Palacio

Theses and Dissertations

Simulation modeling has become an essential tool for optimizing complex systems, especially in healthcare, where it plays a significant role in advancing decision-making and improving patient outcomes. One critical area benefiting from simulation is the study of cardiovascular diseases, where fluid dynamics modeling aids in understanding hemodynamics, the flow of blood through the body. Accurate hemodynamic simulations help personalize treatment plans, minimize risks, and reduce the need for invasive procedures.

This thesis explores the intersection of systems engineering and biomedical fluid dynamics modeling, aiming to bridge the gap between simulation and clinical practice. The research introduces a framework for enhanced …

Physics Embedded Neural Network: A Novel Data-Free Numerical Method For Solving Computational Physics Problems, Pawan Gaire

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

A novel approach for solving partial differential equations (PDEs) using neural networks for scientific computing is introduced. The proposed approach, referred to as physics-embedded neural network (PENN), features a unique architecture that incorporates the PDE and boundary conditions information directly within the final fully-connected layer of the feed-forward neural network (NN). The key aspect of PENN is the parallel numerical embedding of a differential equation associated with physical problems within the activation function of the network’s final layer. This integration leads to a new class of computational solvers competitive with classical methods like the Finite Element Method (FEM) and capable …

A Study Of Ultrafast, Intense-Field Photodynamics In Carbon Dioxide, Carbon Disulfide, And Select Substituted Benzenes, Joshua Edwin Beck

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

The study of the photodynamics of molecules in ultrashort pulses of intense radiation continues to be of interest. Electric field strengths in such pulses can approach or exceed the typical electric field strengths binding the electrons to the nuclear framework (ke/a²₀ ≈ 5 × 10⁹ V/cm). The resulting excitation, ionization, and dissociation of molecular targets is of interest in many areas including attosecond science, femtochemistry, atmospheric science, high harmonic generation, and many other fields.

This dissertation investigates the photoionization and photofragmentation behavior of carbon dioxide, carbon disulfide, and the substituted benzenes nitrobenzene, aniline, as …

Analyzing Meteor Shower Radiants, Elise Springman

Celebrating Scholarship and Creativity Day (2018-)

Meteor shower origin points, or radiants, are a widely studied topic in astrophysics as they give a lot of context to the meteor shower itself as well as provide a way study broader space. Specifically, when it comes to annual showers, these radiant points are compared with previous years to create a broader database about the shower and check accuracy of instruments. This project is ongoing with several places tracking these annual showers and comparing data to give a more detailed history of each shower. Here at CSBSJU, meteor showers were analyzed using an AllSky camera, and a few additional …

Thin-Film Optical Filters For Selective Transmission And Black-Body Reflection In Pyroelectric Energy Systems., Cedric Cruz Silva

Electronic Theses and Dissertations

Essential to pyroelectric energy systems is the ability for a pyroelectric material to achieve high temperatures rapidly. In pursuit of augmenting this process, several thin-film optical filters were designed for transmitting laser excitation in the near-infrared region, while simultaneously reflecting black-body radiation for pyroelectric materials. Designs include a classical Fabry-Perot structure with gold and tantalum pentoxide, an induced transmittance filter with silica, hafnia, and gold, and an indium-tin-oxide filter with silica, alumina, and ITO. Performance varies depending on the design. The Fabry-Perot filter experimentally showed a maximum transmittance of 42% at 1.04 μm and an infrared reflectance of 98%. The …

Rotation Errors Due To Field Quantization For Simultaneously Driven Atoms, Hunter Lindemann

Graduate Theses and Dissertations

If we want to physically implement qubits by using two level atoms within a cavity, then certain single-qubit gates (such as the X-gate) can be performed by bathing the atoms in an electromagnetic field from a laser. If the average photon count n̄ of the field greatly exceeds the number of N qubits, then the slight fluctuations of the field's phase and amplitude are mostly negligible. However, such a strong field might require more energy than what is desirable for the setup. If a weaker field is used in which phase and amplitude fluctuations might be noticeable, then the …

Geometric Algebra For Field Theory In Curved Spacetime, Kevin Rhine

All Graduate Reports and Creative Projects, Fall 2023 to Present

Physics seeks to understand the universe by uncovering the fundamental laws that govern matter, energy, space, and time. At its heart lies the challenge of unification: finding a mathematical framework that consistently describes these interactions across all scales, from the subatomic to the cosmological.

This thesis explores geometric algebra, a mathematical language that unifies algebra and geometry, as a tool for advancing this understanding. By extending this framework to curved spacetimes, where gravity influences the structure of space and time, we investigate its ability to describe physical phenomena such as electromagnetism and general relativity. A notable contribution includes the geometric …

Jwst Reveals The Diversity Of Nuclear Obscuring Dust In Nearby Agn: Nuclear Isolation Of Miri/Mrs Data Cubes And Continuum Spectral Fitting, Omaira González-Martín, Daniel J. Díaz-González, Mariela Martínez-Paredes, Almudena Alonso-Herrero, Enrique López-Rodríguez, Begoña García-Lorenzo, Cristina Ramos Almeida, Ismael García-Bernete, Donaji Esparza-Arredondo, Sebastian F. Hoenig, Santiago García-Burillo, Chris Packham, Nancy A. Levenson, Alvaro Labiano, Miguel Pereira-Santaella, Francoise Combes, Anelise Audibert, Erin K.S. Hicks, Lulu Zhang, Enrica Bellocchi, Richard I. Davies, Laura Hermosa Muñoz, Masatoshi Imanishi, Claudio Ricci, Marko Stalevski

Faculty Publications

We investigate the capabilities of the mid-infrared instrument (MIRI) of JWST to advance our knowledge of active galactic nucleus (AGN) dust using the spectral fitting technique on an AGN collection of 21 nearby (z < 0.05) AGN (7 type-1 and 14 type-2) observations obtained with the medium resolution spectroscopy (MRS) mode. This collection includes publicly available AGN and data from the collaboration of Galactic Activity, Torus, and Outflow Survey (GATOS). We developed a tool named MRSPSFisol that decomposes MRS cubes into point-like and extended contributions. We found statistically good fits for 12 targets with current AGN dust models. The model that provides good fits (χ²/dof< 2) for these 12 targets assumes a combination of clumpy and smooth distribution of dust in a flare-disc geometry where the dust grain size is a free parameter. Still, two and one AGN statistically prefer the disc + wind and the classical clumpy torus model, respectively. However, the currently available models fail to reproduce 40 per cent of the targets, likely due to the extreme silicate features not well reproduced by the models and signatures of water-ice and aliphatic hydrocarbon absorption features in most targets. New models exploring, for instance, new chemistry, are needed to explain the complexity of AGN dust continuum emission observed by JWST.

Charge And Spin Transport In Nanowires With Spin-Orbit Coupling, Ryan Perrin

All Dissertations

Nanowires exhibiting Fermi-level pinning have strong radial electron confinement and thus can be modeled as a two-dimensional electron gas wrapped around the core. In III-V semiconductor structures, two forms of spin-orbit coupling are generated by breaking inversion symmetries in the crystal (Dresselhaus) and the overall structure of the nanowires (Rashba). The first goal of this thesis is to understand the single-particle energy spectrum in nanowires with variable cross sections and the quantum oscillations that can be driven in them by the application of a magnetic field parallel to the axis of the wire. To this end, the eigenfunctions and eigenvalues …

The Role Of The Neutral Wind In Observations Of High-Latitude Ionospheric Energy Transfer, Andrew M. Pepper

All Dissertations

Joule heating results from the collisional interaction between ions and neutrals and serves as a crucial mechanism for energy transfer between Earth's magnetosphere and ionosphere-thermosphere system, particularly at high latitudes. This dissertation investigates the modulation of Joule heating by altitude-resolved neutral winds, electric fields, and conductivity variations through multi-instrument observational analysis and modeling that incorporates both in-situ and ground-based sources to measure the main drivers of ion-neutral coupling. The observations presented consistently demonstrate a dual regulatory effect of the neutral wind on energy deposition that varies systematically with both geomagnetic activity level and proximity to auroral boundaries. In regions characterized …

Search For A Diffuse Flux Of Photons With Energies Above Tens Of Pev At The Pierre Auger Observatory, A. Abdul Halim, P. P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, B. Fick, K. Nguyen, D. Nitz, Et Al.

Michigan Tech Publications

Diffuse photons of energy above 0.1 PeV, produced through the interactions between cosmic rays and either interstellar matter or background radiation fields, are powerful tracers of the distribution of cosmic rays in the Galaxy. Furthermore, the measurement of a diffuse photon flux would be an important probe to test models of super-heavy dark matter decaying into gamma-rays. In this work, we search for a diffuse photon flux in the energy range between 50 PeV and 200 PeV using data from the Pierre Auger Observatory. For the first time, we combine the air-shower measurements from a 2 km2 surface array consisting …

New Mathematical Approaches To Ultra-Cold Atoms, Joanna Ruhl

Graduate Doctoral Dissertations

This dissertation addresses three main themes: cold atoms, integrability, and number theory. In this dissertation we present novel approaches to four models, each of which touches on at least two of the three themes. At the intersection of cold atoms and integrability, we present a Lagrange bracket formalism that allows for exact computation of initial quantum fluctuations of soliton breathers which previously could only be estimated numerically, and the advance in software tools developed in Python to facilitate studies of two-dimensional disc breathers. At the intersection of integrability and number theory, we present a propagator for the Newman-Moore, or triangular …

Conservation Laws For Asymptotically Perfect Fluid Spacetimes, Lyle Arnett Jr.

All Graduate Theses and Dissertations, Fall 2023 to Present

In physics, conservation laws, like those for energy or momentum, are powerful tools that help us understand how systems evolve and interact. In general relativity, where spacetime itself is curved by matter and energy, defining such conservation laws becomes especially subtle and complex. Traditional methods rely on idealized conditions like empty space or special symmetries, which limit their usefulness in more realistic, dynamic settings such as an expanding universe.

This dissertation explores a modern mathematical framework, developed by Iyer and Wald, that allows conservation laws to be derived directly from the equations governing spacetime. Using this approach, I examine not …

Predicting Healthcare Service Quality Based On A Kalman-Optimized Bi-Lstm-Inspired Deep Learning Model, Mohammed K. Al-Khafaji, Eman S. Al-Shamery

Karbala International Journal of Modern Science

Health is one of the most important aspects of human well-being, and access to high-quality healthcare is essential for a good quality of life. Providing top-level health services at all times is crucial. However, the research in healthcare poses significant challenges due to the diversity and variations of medical practices across different hospitals. This paper aims to tackle the challenge of data missing and scattering during data collection. Then, the quality of services (QoS) offered by healthcare facilities will be analyzed and predicted from the patient's perspective. The model begins preprocessing data by data cleaning, handling missing values, and scattering …

Dust And Metals In Distant Galaxies, Fatima Elkhatib

Theses and Dissertations

Interstellar dust causes reddening and dimming of light from background objects. To analyze how different the dust in distant galaxies is compared to dust in nearby galaxies, we look at multiple background quasars and try to fit their spectra with various models for known galaxies that have differing dust grain populations combined with a quasar spectrum template. Through fitting these models, we found that dust in most of the foreground galaxies we analyzed is similar to the SMC bar, a relatively thin area selected from the Small Magellanic Cloud (SMC). However, we note that all the objects we studied did …

Photometric Redshifts Of Galaxies In Quasar Fields, Ananthavishnu Santhigiri Unni

Theses and Dissertations

Understanding the gas in and around galaxies is crucial for understanding galaxy evolution. Absorption lines detected in the spectra of background quasars offer a powerful tool to study the gas in and around the intervening galaxies. As a part of an effort to understand how the gas interacts with the stellar component of galaxies, our team previously obtained imaging and spectroscopic observations for a large sample of galaxies using the Hubble Space Telescope (HST), the Very Large Telescope (VLT), and the Atacama Large Millimeter Array (ALMA). This sample includes thousands of galaxies, including many without spectroscopic data. The overall goal …

Power-Beaming: Wireless Energy Transfer Using Lasers, Spencer L. Barnett

ATU Scholars Symposium

The objective of the project is to implement a wireless energy transfer system utilizing laser technology. This system involves modulating the laser’s beam profile and spatial distribution through precise optical manipulation. The energy transmitted by the laser is captured by a photovoltaic array, commonly referred to as a solar panel, which is engineered to convert incident photons into direct current (DC) electrical power. The current challenge is to develop a reliable wireless energy transfer mechanism capable of operating over extended distances, thereby overcoming the constraints imposed by wired connections, particularly in environments where wiring is impractical, such as in space. …

Light As A Lasso: The Design And Construction Of An Optical Trap, Joseph E. Temple

ATU Scholars Symposium

The goal of our work is the design and construction of an optical trap, also known as an "optical tweezer," using equipment commonly available to the undergraduate physics laboratory. Such devices allow us to observe and manipulate micron-scale (on the order of one-thousandth of a millimeter) objects in 3-dimensional space using only light.

The system consists primarily of five components: a laser, two mirrors to collimate (make parallel to the optical table) the beam, two lenses forming a beam expander, two more lenses granting control over the trapping plane, and a microscope objective to focus the beam. Thus far we …

Analyzing Quantum Mechanical Properties Of Electrons Via The Anomalous Zeeman Effect To Verify The Bohr Magneton, Gunner W. Hodges, Anthony J. Mclain

ATU Scholars Symposium

At the turn of the 19th century, scientists were gradually realizing that nature did not behave as it had been thought for centuries. Many thought the concrete laws governing nature were soon to be completed. As we now know, their deterministic optimism was far from reality. Electromagnetic theory predicted that the spectral line emissions from a bulb would split into three distinct bands in the presence of a uniform magnetic field. This behavior was proven in what is known as the Normal Zeeman Effect. What was not expected though was the host of extraneous bands that accompanied the predicted triplet …

Computational Modeling Of Poly-Peptide Chains, Nathan F. Surles, Kaitlin A. Edwards

ATU Scholars Symposium

Investigations of the structural properties of polypeptides are essential for understanding their conformational behavior, stability, and potential biological interactions. In this study, we employed computational techniques to determine the optimized structures of two model polypeptides: tri-glycine and di-tryptophan.

Charge-To-Mass Ratio Of The Electron, Joseph E. Temple, Zachary D. Jimerson

ATU Scholars Symposium

We measured the charge-to-mass ratio (q/m) of the electron via a method similar to that used by J.J. Thomson in 1897. Our calculated value is q/m = (1.752 +/- 0.046) x 10^11 C/kg, which agrees with the textbook value of 1.759 x 10^11 C/kg within an error of 0.36%. This confirms the viability and accuracy of Thomson's approach for determining the electron's q/m ratio. Observed uncertainties are attributed to variations in the magnetic field within the Helmholtz coil apparatus and fluctuations in current over time.

An Analysis On The Time Effectiveness Of Speeding While Driving A Vehicle, Joy Skaggs

ATU Scholars Symposium

Speeding is responsible for roughly a third of all crashes, often coming at a deadly cost. The National Highway Traffic Safety Administration reports many negative consequences, such as a greater likelihood of loss of vehicle control, reduced protection equipment effectiveness, increased stopping distance, crash severity, and fuel consumption (National Highway Traffic Safety Administration, n.d.). Yet despite these costs, drivers continue to speed. In fact, in our fast paced world, speeding is so normalized that it’s uncommon to encounter a driver following the speed limit. Hawaiian psychology professor Leon James explains it best: people have twisted their definitions of speeding to …

Implications Of The Cosmic Calibration Tension Beyond ��₀ And The Synergy Between Early- And Late-Time New Physics, V. Poulin, Tristan L. Smith, R. Calderón, T. Simon

Physics & Astronomy Faculty Works

The cosmic calibration tension is a >5⁢�� discrepancy between the cosmological distance ladder built from baryonic acoustic oscillations calibrated by the Planck/Λ cold dark matter (Λ⁢CDM) sound horizon (��_��) and type Ia supernovae calibrated instead with the SH0ES absolute magnitude, assuming the distance-duality relationship holds. In this work, we emphasize the consequences of this tension beyond the value of the Hubble constant ��₀ and the implications for physics beyond Λ⁢CDM. Of utmost importance, it implies a larger physical matter density ��ₘ≡Ωₘ⁢ℎ², as both the fractional matter density Ωₘ and ℎ ≡��₀⁡/100 km/s/Mpc are well constrained from late-time data. …

Measuring Small Currents At Fast Speeds Using A 2nd Generation Electrometer, Donna Metcalf

Physics Capstone Projects

This project presents the development of a second-generation electrometer designed to measure extremely low currents with improved speed and sensitivity. Based on the foundational architecture developed by Vladimir Zavylov, this iteration focuses on enhancing performance through optimized circuit components, modular configuration, and a custom-designed, battery- powered power supply that enables high-voltage floating measurements. The work encompasses the complete design cycle—creating a full schematic, developing a tailored power delivery system, assembling printed circuit boards (PCBs), constructing wiring harnesses, and integrating components into a protective housing.

Lunar Secondary Crater Identification Through Semi-Automated Data Aggregation: The Beginnings Of The Pipeline, Annalyse Dickinson

Physics and Astronomy Honors Papers

Based on the number of primary craters on a surface, one can determine the age of that surface, but secondary craters contaminate that count. No single characteristic can distinguish primaries from secondaries with certainty; a feature that is present in one collection of secondaries can be absent in another due to the multitude of processes involved in their formation and degradation. We aim to develop a pipeline that will classify craters based on characteristics that have been used to differentiate secondaries on the Moon, including elevation profiles, degradation state, radar circular polarization ratio, rock abundance, and spatial clustering. We utilize …

Computational Analysis Of Proton Conductivity Factors In Grotthuss-Style Mechanisms, Brock Dyer

Physics and Astronomy Honors Papers

The mechanism and fundamental molecular properties involved in proton conduction are discussed. Four calculable properties are presented: the proton affinity, binding energy (between protonated and neutral forms), intramolecular tautomerization barrier, and proton hopping barrier. An overview of the computational methods used in this thesis, including an introduction to the many-body Schrödinger equation and Density Functional Theory, as well as a look at Plane-Wave Density Functional Theory and Gaussian-Type Orbital Density Functional Theory are presented. 4,5-dimethyl-[1,2,3]-triazole is used as a model system, with 10 variations being generated with varying amounts and positions of fluorine substitution on the methyl groups. Preliminary calculations …

Understanding The Mechanism Of Bent Dna Amplifying Sensors Using All-Atom Molecular Dynamics Simulations, Kaitlin Bullard, Deborah Okyere, Shelbi J> Foster, Asmaa Ali Sadoon, Jiali Li, Jingyi Chen, Yong Wang

Physics Faculty Publications and Presentations

Bent DNA amplifying sensors were recently developed to amplify and quantify the interactions of DNA with various salts and molecules. However, a thorough quantitative understanding of their mechanism is missing. Here, using all-atom molecular dynamics (MD) simulations, we investigate the behavior and dynamics of sharply bent DNA molecules in the absence and presence of Mg2+ ions at different concentrations. The simulations show that Mg2+ ions reduce the fluctuations of DNA strands, enhance base-pairing, and stabilize bent DNA molecules. The computational results are further verified by both melting curve experiments and ensemble FRET measurements, highlighting the mechanical instability and sensitivity of …

Young Professionals, Zachary Gibson

Journal Articles

Like many of us, I have attended numerous panels, seminars, and workshops geared toward helping young professionals and students. The more senior professionals are gathered for us to question and tap them for wisdom and anecdotes. One such question that inevitably comes up in one form or another is, “How did you get to where you are?” A thinly veiled question intending to ask how can one get to the same or similar position. The response often begins with a soft chuckle and a “well … ” Their answers are caveated by “my path was not the typical path.”

Using The Epic Algorithm For Radio Astronomy, Samuel D. Michaud

Research & Creative Achievement Day

The EPIC (E-field Parallel Imaging Correlator) algorithm is a direct imaging correlator for radio interferometer arrays. Bypassing the expensive processing step of cross correlation and immediately computing a spatial fast Fourier transform allows it to generate extremely high framerate radio images. EPIC serves to efficiently process signals from a very high count of radio antennas in an array with parallel computing, scaling as Nlog(N). This research project investigates the advantages and limitations of using EPIC for astronomy. This was done by stress testing both the user interface and back-end database through SQL commands to validate the output data it processed …