Digital Commons Network^™

Relativistic And Recoil Corrections To Vacuum Polarization In Muonic Systems: Three-Photon Exchange, Gauge Invariance, And Numerical Values, Gregory S. Adkins, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

For an accurate theoretical description of muonic bound systems, it is crucial to consistently treat relativistic and recoil corrections to vacuum polarization. The one-loop vacuum-polarization effect is by far the dominant quantum electrodynamic (QED) energy correction for bound muons, being of order α(Zα)2mr, where α is the fine-structure constant, Z is the nuclear charge number, and mr is the reduced mass. Gauge invariance of the relativistic and recoil corrections to vacuum polarization of order α(Zα)4mr is investigated with respect to nonretarded and standard, renormalized variants of Coulomb gauge. The invariance is shown after including three-photon exchange diagrams. Our derivation is …

Separation Of Various Higher-Order Effects In The Ionization Of Helium By Proton Impact, S. Majumdar, S. Bastola, A. Hasan, R. Lomsadze, Michael Schulz

Physics Faculty Research & Creative Works

We have measured fully differential cross sections (FDCSs) for ionization of helium by 75 keV proton impact. Data were analyzed for electrons ejected into the scattering plane at projectile energy losses well below and above the matching velocity and for scattering angles ranging between 0.1 and 0.5 mrad. Earlier, we observed clear signatures of the post collision interaction (PCI) at the matching velocity; however, in the current data these signatures are completely absent at small energy losses and residues remain at large energy losses. At small energy losses the FDCSs are dominated by non-PCI higher-order effects.

Design, Fabrication, And Spectroscopy Of Photocatalytic Materials In Visible Spectrum, Yamuna Paudel

Dissertations, Theses, and Capstone Projects

Heterogeneous photocatalysis has attracted research interest in sustainable energy technologies. However, achieving high photocatalytic efficiency from visible light-absorbing semiconductors is challenging due to their weak absorption, transport losses, and low activity. While multilayer approaches have been developed to enhance the surface reactivity and stability independent of electronic factors, a comprehensive framework for optimizing light-matter interactions has not yet been established. Here, we introduce a photonic strategy using semiconductor metasurfaces, which is highly effective in enhancing the photocatalytic activity of GaAs, a high-performance semiconductor with a near-infrared bandgap. Our engineered pillar arrays with heights of ~150 nm exhibit Mie resonances near …

Interplay Of Magnetic Impurities And Superconductivity In Topological Materials, Didier Ndengeyintwali

Dissertations, Theses, and Capstone Projects

The interplay of superconductivity and magnetism has been a long-standing topic of interest since the discovery of superconductivity. In recent years it has been shown that topological superconductivity, which has promising applications such as in topological quantum computing, could result from such interplay. Motivated by the later results I study the effect of magnetic impurities in superconducting doped topological insulators, such as Iron based topological superconductors. I show that topological character of parent materials could lead to modifications in the structure of magnetic impurity induced in-gap states. Moreover, the superconductivity induced interaction between magnetic impurities in doped topological insulator would …

Electromagnetic Theory And Applications, 2nd Edition, Nicholas Madamopoulos, George Kliros

Open Educational Resources

This book intends to provide both the fundamentals of Electromagnetics but also some practical applications of the concepts covered. Having taught electromagnetics for several years, the authors feel that many times the field of electromagnetics comes as “old” and often times students do not appreciate the concepts and their importance in everyday applications. The authors intend to accompany the EM concepts with life applications. Hence, students may see the direct impact of the knowledge they acquire through the study of the field of electromagnetics and better appreciate the field.

Observation Of The Galactic Center Pevatron Beyond 100 Tev With Hawc, A. Albert, R. Alfaro, C. Alvarez, A. Andrés, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, A. Bernal, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, S. Coutiño De León, E. De La Fuente, C. De Leon, D. Depaoli, N. Di Lalla, R. Diaz Hernandez, B. L. Dingus, M. A. Duvernois, J. C. Diaz-Velez, K. Engel, T. Ergin, C. Espinoza, K. L. Fan, K. Fang, N. Fraija, S. Fraija, J. A. Garcia-Gonzalez, F. Garfias, H. Goksu, M. M. Gonzalez, J. A. Goodman, S. Groetsch, J. P. Harding, S. Hernandez-Cadena, I. Herzog, J. Hinton, D. Huang, F. Hueyotl-Zahuantitla, T. B. Humensky, P. Huntemeyer, A. Iriarte, S. Kaufmann, D. Kieda, A. Lara, W. H. Lee, J. Lee, H. Leon Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martinez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Montes, J. A. Morales-Soto, E. Moreno, M. Mostafa, M. Najafi, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, L. Olivera-Nieto, N. Omodei, M. Osorio-Archila, Y. Perez Araujo, E. G. Perez-Perez, C. D. Rho, D. Rosa-Gonzalez, E. Ruiz-Velasco, H. Salazar, D. Salazar-Gallegos, A. Sandoval, M. Schneider, G. Schwefer, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Urena-Mena, E. Valera, Xiaojie Wang, Z. Wang, I. J. Watson, E. Willox, H. Wu, S. Yu, S. Yun-Carcamo, H. Zhou

Physics Faculty Research & Creative Works

We report an observation of ultrahigh-energy (UHE) gamma rays from the Galactic center (GC) region, using 7 yr of data collected by the High-Altitude Water Cherenkov (HAWC) Observatory. The HAWC data are best described as a point-like source (HAWC J1746-2856) with a power-law spectrum ( d N / d E = ϕ E / 26 TeV γ ), where γ = −2.88 ± 0.15stat − 0.1sys and ϕ = 1.5 x 10⁻¹⁵ (TeV cm² s)⁻¹ ± 0.3 stat − 0.13 sys + 0.08 sys extending from 6 to 114 TeV. We find no evidence of a spectral …

Stability And Dynamics Of Nonlinear Excitations In A Two-Dimensional Droplet-Bearing Environment, G. Bougas, G. C. Katsimiga, P. G. Kevrekidis, S. I. Mistakidis

Physics Faculty Research & Creative Works

We unravel stationary states in the form of dark soliton stripes, bubbles, and kinks embedded in a two-dimensional droplet-bearing setting emulated by an extended Gross-Pitaevskii approach. The existence of these configurations is corroborated through an effectively reduced potential picture demonstrating their concrete parametric regions of existence. The excitation spectra of such configurations are analyzed within the Bogoliubov-de Gennes framework exposing the destabilization of dark soliton stripes and bubbles, while confirming the stability of droplets, and importantly unveiling spectral stability of the kink against transverse excitations. Additionally, a variational approach is constructed providing access to the transverse stability analysis of the …

Multiply Differential Study Of Vibrational Dissociative Capture In P+ D2 Collisions, S. Majumdar, A. Hasan, S. Bastola, B. R. Lamichhane, R. Lomsadze, Michael Schulz

Physics Faculty Research & Creative Works

We have measured multiple differential cross sections for dissociative capture in collisions of 75-keV protons with D2. Data were analyzed for kinetic energy releases (KERs) ranging from 0 to 2 eV, where the dissociation is primarily caused by excitation of the nuclear motion to a vibrational continuum state. Pronounced signatures of two-center interference effects were observed. The data were compared to previously published cross sections for dissociative capture in p+H2 collisions, for which we reported a scattering angle dependent phase shift in the interference term. The D2 data reveal qualitative differences in the interference structure to the H2 case. Some …

Investigating Temperature And Emissivity Separation Techniques Through The Use Of A Spectral Emissivity Database, Mitchell A. Manzardo

Theses and Dissertations

This study evaluates two temperature and emissivity separation techniques using data from an ABB MR304 FTIR and a Telops Mid-Wave Hyper-Cam on carbon-based samples heated by a high-energy laser. The established Linear Spectral Emissivity Constraint (LSEC) and Gray Body Emissivity (GBE) methods, as well as a new Robust Ratio Linear Fitting (RRF) method are assessed for their applicability in controlled lab environments. A spectral emissivity database aids in analyzing method performance. The RRF method shows promise but has limitations, particularly with low-temperature data and complex Hyper-Cam data. Despite these challenges, the RRF method offers potential for further refinement.

Generation And Implementation Of Mixed Radiation From Laser Interactions On A Liquid Target, Benjamin M. Knight

Theses and Dissertations

The simultaneous generation of different forms of radiation from the same source is highly desirable but technically challenging. We present the generation of D-D fusion neutrons and >MeV-energy x-rays from extreme intensity (∼ 10¹⁹ W/cm² ), high repetition-rate (1 kHz) laser pulses on a thin liquid target. Total neutron fluxes of ∼ 105 neutrons/s and x-ray exposure rates up to ∼ 200 R/hr at 74 cm are measured. Evidence of D-D fusion is verified with a measurement suite including three independent neutron detection systems: an EJ-309 organic scintillator, a ³He proportional counter, and a set of 36 …

Collisional And Spatial Characterization Of Electron Broadening In Rubidium Vapor, Jordan C. Mindrup

Theses and Dissertations

Stark broadening of the 4²D → 12²F transition of rubidium is examined in a rubidium vapor cell with modulated double pump-probe spectroscopy at helium pressures of 0.001 Torr, 3.0 Torr, and 30.0 Torr. A pressure dependent critical rubidium number density was observed after which the presence of electrons becomes dominant. It is observed that after the rubidium density threshold, a linear relationship is seen between rubidium number density and the Stark broadened width of the line shapes, with a slope of 0.079 ± 0.002, 0.18 ± 0.01, and 0.9 ± 0.1 for helium pressures of 0.001 …

Twisted Spatiotemporal Optical Vortex Beams In Dispersive Media, Milo W. Hyde Iv

Faculty Publications

We derive a closed-form expression for the mutual coherence function (MCF) of a twisted spatiotemporal optical vortex (STOV) beam after propagating a distance in a linear dispersive medium. A twisted STOV beam is a partially coherent optical field that possesses a coherent STOV and a stochastic twist coupling its space and time dimensions. These beams belong to a special class of space–time-coupled light fields that carry transverse (to the direction of propagation) orbital angular momentum, making them potentially useful in numerous applications including quantum optics, optical manipulation, and optical communications. After presenting the derivation, we validate our new general MCF …

Structural, Electronic And Magnetic Properties Of Vanadium Doped Transition Metal Dichalcogenides (Tmds), Qudsia Ashraf

Dissertations, Theses, and Capstone Projects

Magnetic semiconductors are a prerequisite for spintronic devices but their ferromagnetism disappears at room-temperature hindering application in room temperature electronic devices. Enormous research has been conducted on the room-temperature ferromagnetic order in monolayer form of bulk van der Waals materials but the few layer system has not been extensively explored.

Doping is an effective approach to modulate the structural, electronic and magnetic properties of two-dimensional (2D) Transition metal dichalcogenides (TMDs) and expand their application. The effect of vanadium dopant on structural, electronic and magnetic properties of Tungsten Diselenide (WSe₂) was studied by X-ray Photoelectron Spectroscopy (XPS), Atomic Force …

Design And Characterization Of De Novo Photoactivated Charge Separating Proteins, Paul M. Molinaro

Dissertations, Theses, and Capstone Projects

Light activate charge separation can provide high energy electrons for a variety of chemical processes. Reaction center proteins serve as a scaffold for small molecules that serve as “hopping” sites for electrons. Previous reaction center designs are four helix bundles that bind at minimum two metalloporphyrin’s: a zinc porphyrin serves as a light activated electron donor, mimicking chlorophyl, and a heme molecule serving as the acceptor. The efficiency of these designs is hampered by the enhanced relaxation of the singlet excited state of zinc porphyrin molecules due to spin-orbit coupling with the paramagnetic heme acceptor. The optimal design would contain …

Shear Viscosity Of Quasi One-Dimensional Bec Tubes And Entanglement Negativity Conditions, Camilla Polvara

Dissertations, Theses, and Capstone Projects

Shear Viscosity of Quasi One-dimensional BEC Tubes

We consider layered Bose-Einstein condensates interacting via contact intra-condensate interacions and dipolar inter-condensate potentials, both of which dominate intercondensate tunneling (which we neglect for simplicity). For this system, we compute the normal modes, we study its localization properties by numerically computing the inverse participation ratio, and we compute the inter-tube shear viscosity.

Entanglement Negativity Conditions

This project explores bounds on entanglement negativity using operator inequalities, building on the results of [1]. We are looking for a way to quantify entanglement, as an alternative to calculating the full negativity, which would otherwise require the …

Precision Measurement Of The Absolute Energy Of The 2s3s 1S0 State In Neutral 9Be, K. J. Ahrendsen, T. Karani, W. D. Williams

Physics: Faculty Publications

We report on the absolute energy of the 2⁢��⁢3⁢��⁢1⁢��0 state in neutral 9Be. In doing so, we measure the transition frequencies of the 2⁢��2⁢1⁢��0→ 2⁢��⁢2⁢��⁢1⁢��∘1 and 2⁢��⁢2⁢��⁢1⁢��∘1→ 2⁢��⁢3⁢��⁢1⁢��0 transitions, also determining the absolute energy of the 2⁢��⁢2⁢��⁢1⁢��∘1 state. The results are obtained from a home-built hollow cathode discharge lamp using saturated absorption spectroscopy with laser frequencies referenced to a frequency comb. The transition frequencies are determined to be 1276080080⁢(50) and 363105650⁢(130) MHz for the 2⁢��2⁢1⁢��0→ 2⁢��⁢2⁢��⁢1⁢��∘1 and 2⁢��⁢2⁢��⁢1⁢��∘1→ 2⁢��⁢3⁢��⁢1⁢��0 transitions, respectively. The absolute energies are determined to be 42565.4498⁢(17) and 54677.350⁢(5) cm−1 for the 2⁢��⁢2⁢��⁢1⁢��∘1 and 2⁢��⁢3⁢��⁢1⁢��0 states, respectively. The …

Spatial Planning Offshore Wind Energy Farms In California For Mediating Fisheries And Wildlife Conservation Impacts, Crow White, Yi-Hui Wang, Ryan K. Walter, Benjamin Ruttenberg, Danny Han, Eli Newman, Ethan R. Deyle, Sucharita Gopal, Les Kaufman

Physics

Achieving a blue economy will require reconciling the value of emerging ocean uses with their impacts on the seascape and sectors with historical access to marine resources and areas. To meet this challenge, we developed an analytical framework for conducting marine spatial planning through tradeoff analysis, and applied it to prospective offshore wind energy development in the ∼974 km2 Morro Bay, California, USA Wind Energy Area (WEA). We generated spatial data layers estimating MW power production and impacts on fisheries value and marine wildlife conservation (seabird and cetacean populations) from wind farm development. We then quantified each sector's response to …

Strain And Substrate-Induced Electronic Properties Of Novel Mixed Anion-Based 2d Schx2 (X = I/Br) Semiconductors, Ashima Rawat, Ravindra Pandey

Michigan Tech Publications

Exploration of compounds featuring multiple anions beyond the single-oxide ion, such as oxyhalides and oxyhydrides, offers an avenue for developing materials with the prospect of novel functionality. In this paper, we present the results for a mixed anion layered material, ScHX2 (X: Br, I) based on density functional theory. The result predicted the ScHX2 (X: Br, I) monolayers to be stable and semiconducting. Notably, the electronic and mechanical properties of the ScHX2 monolayers are comparable to well-established 2D materials like graphene and MoS2, rendering them highly suitable for electronic devices. Additionally, these monolayers exhibit an ability to adjust their band …

Imaging Photoinduced Dynamics In Gas-Phase Molecules Using Ultrafast Electron And X-Ray Diffraction, Sri Bhavya Muvva

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

Investigating the ultrafast structural changes in photoexcited molecules provides essential information on their governing reaction mechanisms and product formation. Time-resolved electron and X-ray diffraction are crucial techniques for capturing the structural information of photoexcited molecules on femtosecond timescales. This thesis presents the investigations of photochemical reactions in gas-phase molecules using ultrafast electron and X-ray diffraction experiments.

Photoexcitation of conjugated diene molecules with ultraviolet (UV) laser pulses can lead to different reaction mechanisms, depending on their double bonds’ positions and molecular rigidity. Chapter 2 of this dissertation discusses the femtosecond time-resolved UV-induced excited-state structural dynamics of cis,cis-1,3-cyclooctadiene, an eight-membered cyclic conjugated …

Value Creation In A Pedagogically-Focused Faculty Online Learning Community, Fred Goldberg, Edward Price, Mo Basir, Lawrence Escalada, Steve Maier, Steven Sahyun, Tamara D. Snyder, Liang Zeng

Physics & Astronomy Faculty Publications

Faculty online learning communities (FOLCs) can help faculty effectively adopt and persist in using research-based curricula. This paper documents faculty perspectives on the value they gained from participating in a multi-year FOLC designed to help them implement an inquiry-based physical science curriculum. Personal value narratives were collected from 11 volunteer FOLC participants. In the narratives, participants responded to prompts regarding their initial reasons for participation, activities they engaged in, and values they gained, as well as how participation impacted their profession, social connections, professional practice, and ability to influence their world as teachers. Qualitative analysis shows that the values faculty …

Toi–757 B: An Eccentric Transiting Mini–Neptune On A 17.5–D Orbit, A Alqasim, N Grieves, N M. Rosário, D Gandolfi, J H. Livingston, S Sousa, K A. Collins, J K. Teske, M Fridlund, Ryan J. Oelkers

Physics & Astronomy Faculty Publications

We report the spectroscopic confirmation and fundamental properties of TOI 757 b, a mini Neptune on a 17.5 d orbit transiting a bright star (⁠ mag) discovered by the TESS mission. We acquired high precision radial velocity measurements with the HARPS, ESPRESSO, and PFS spectrographs to confirm the planet detection and determine its mass. We also acquired space borne transit photometry with the CHEOPS space telescope to place stronger constraints on the planet radius, supported with ground based LCOGT photometry. WASP and KELT photometry were used to help constrain the stellar rotation period. We also determined the fundamental parameters of …

Tev Analysis Of A Source-Rich Region With The Hawc Observatory: Is Hess J1809-193 A Potential Hadronic Pevatron?, A. Albert, R. Alfaro, C. Alvarez, J. C. Arteaga-Velázquez, D. Avila Rojas, R. Babu, E. Belmont-Moreno, A. Bernal, M. Breuhaus, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, J. Cotzomi, E. De La Fuente, D. Depaoli, N. Di Lalla, R. Diaz Hernandez, B. L. Dingus, M. A. Duvernois, C. Espinova, K. L. Fan, K. Fang, B. Fick, N. Fraija, J. A. Garcia-Gonzalez, F. Garfias, A. Gonzalez Munoz, M. M. Gonzalez, J. A. Goodman, S. Groetsch, J. P. Harding, S. Hernandez-Cadena, I. Herzog, D. Huang, F. Hueyotl-Zahuantitla, P. Huntemeyer, A. Iriarte, V. Joshi, S. Kaufmann, A. Lara, J. Lee, H. Leon Vargas, A. L. Longinotti, G. Luis-Raya, K. Malone, J. Martines-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Montes, J. A. Morales-Soto, E. Moreno, M. Mostafa, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, M. Osorio, Y. Perez Araujo, E. G. Perez-Perez, C. D. Rho, D. Rosa-Gonzalez, E. Ruiz-Velasco, H. Salazar, A. Sandoval, M. Schneider, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Urena-Mena, E. Varela, Xiaojie Wang, I. J. Watson, E. Willox, S. Yun-Carcamo, H. Zhou

Physics Faculty Research & Creative Works

HESS J1809-193 is an unidentified TeV source, first detected by the High Energy Stereoscopic System (H.E.S.S.) collaboration. The emission originates in a source-rich region that includes several supernova remnants (SNRs) and pulsars including SNR G11.1+0.1, SNR G11.0-0.0, and the young radio pulsar PSR J1809-1917. Originally classified as a pulsar wind nebula candidate, recent studies show the peak of the TeV region overlapping with a system of molecular clouds. This resulted in the revision of the original leptonic scenario to look for alternate hadronic scenarios. Marked as a potential PeVatron candidate, this region has been studied extensively by H.E.S.S. due to …

Performance Of The Hawc Observatory And Tev Gamma-Ray Measurements Of The Crab Nebula With Improved Extensive Air Shower Reconstruction Algorithms, A. Albert, R. Alfaro, C. Alvarez, A. Andrés, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, A. Bernal, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, F. Carreón, S. Casanova, U. Cotti, J. Cotzomi, S. Coutiño De León, E. De La Fuente, C. De Leon, D. Depaoli, N. Di Lalla, R. Diaz Hernandez, B. L. Dingus, M. A. Duvernois, K. Engel, T. Ergin, C. Espinoza, K. L. Fan, K. Fang, N. Fraija, S. Fraija, J. A. Garcia-Gonzalez, F. Garfias, H. Goksu, M. M. Gonzalez, J. A. Goodman, S. Groetsch, J. P. Harding, S. Hernandez-Cadena, I. Herzog, J. Hinton, D. Huang, F. Hueyotl-Zahuantitla, P. Huntemeyer, A. Iriarte, S. Kaufmann, A. Lara, J. Lee, H. Leon Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, J. Martinez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Montes, E. Moreno, M. Mostafa, L. Nellen, M. U. Nisa, R. Noriega-Papaqui, L. Olivera-Nieto, N. Omodei, M. Osorio-Archila, Y. Perez Araujo, E. G. Perez-Perez, C. D. Rho, D. Rosa-Gonzalez, E. Ruiz-Velasco, H. Salazar, D. Salazar-Gallegos, A. Sandoval, M. Schneider, G. Schwefer, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Urena-Mena, E. Varela, Xiaojie Wang, I. J. Watson, K. Whitaker, E. Willox, H. Wu, S. Yu, S. Yun-Carcamo, H. Zhou

Physics Faculty Research & Creative Works

The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, located on the side of the Sierra Negra volcano in Mexico, has been fully operational since 2015. The HAWC collaboration has recently significantly improved their extensive air shower reconstruction algorithms, which has notably advanced the observatory performance. The energy resolution for primary gamma rays with energies below 1 TeV was improved by including a noise-suppression algorithm. Corrections have also been made to systematic errors in direction fitting related to the detector and shower plane inclinations, O ( 0 .° 1 ) biases in highly inclined showers, and enhancements to the core reconstruction. The …

Reexamination Of Vacuum-Polarization Corrections To The Self-Energy In Muonic Bound Systems, B. Ohayon, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

In muonic bound systems, the dominant radiative correction is due to vacuum polarization. Yet, for the interpretation of precision experiments, self-energy effects are also important. In turn, additional vacuum-polarization loops perturb the self-energy. Here we show that combined self-energy vacuum-polarization effects can perturb the bound-state self-energy at the percent level in one-muon bound systems with nuclear charges Z=1-6. We also update previous treatments of the corrections for muonic hydrogen, muonic deuterium, and muonic helium bound systems.

A Micromagnetic Study Of Skyrmions In Thin-Film Multilayered Ferromagnetic Materials, Nicholas J. Dubicki

Dissertations

Magnetic skyrmions are topologically protected, localized, nanoscale spin textures in non-centrosymmetric thin ferromagnetic materials and heterostructures. At present they are of great interest to physicists for potential applications in information technology due to their particle-like properties and stability. In a system of multiple thin ferromagnetic layers, the stray field interaction was typically treated with various simplifications and approximations. It is shown that extensive analysis of the micromagnetic equations leads to an exact representation of the stray field interaction energy in the form of layer interaction kernels, a so-called 'finite thickness' representation. This formulation reveals the competition between perpendicular magnetic anisotropy …

Microwave Catalysis-Enabled Membrane Processes For Microbial Inactivation, Fangzhou Liu

Dissertations

The COVID-19 pandemic has highlighted the urgent need for advanced technologies to combat virus transmission. Traditional membrane filtration technologies primarily serve as physical barriers, capturing pollutants but failing to inactivate microbial agents such as bacteria and viruses. These membranes typically target larger particles but are ineffective against sub-micrometer viral particles. Thus, there's a critical demand for membrane filtration processes that combine robust filtration with antifouling and reaction -enabled functions for efficient pathogen disinfection. This research explores a novel microwave-assisted membrane filtration process incorporating catalytic reactions to enhance microbial disinfection and prevent membrane fouling, offering a groundbreaking solution to global challenges …

Numerical Techniques For Improving Simulations Of Tropical Cyclones, Yassine Tissaoui

Dissertations

The increasing frequency and intensity of tropical cyclones (TCs) due to climate change pose significant challenges for forecasting and mitigating their impacts. Despite advancements, accurately predicting TC rapid intensification (RI) remains a challenge. Large eddy simulation (LES) allows for explicitly resolving the large eddies involved in TC turbulence, thus providing an avenue for studying the mechanisms behind their intensification and RI. LES of a full tropical cyclone is very computationally expensive and its accuracy will depend on both explicit and implicit dissipation within an atmospheric model. This dissertation presents two novel numerical methodologies with the potential to improve the efficiency …

Mg3sb2-Based Materials For Mid-Temperature Thermoelectric Application, Veera Prabhu K

Theses and Dissertations

Recently, there has been growing research in the scientific community regarding the conversion of heat flux into electricity, which has proven effective in mitigating energy crises. Solid-state thermoelectric (TE) devices use the Seebeck effect to efficiently convert waste heat into electricity. Traditional materials contain toxic, rare, and expensive elements like Lead, Tellurium, and Germanium that restrict large-scale production, commercialization, and practical utilization.

Recently, Mg3Sb2-based materials have been attractive due to their remarkable characteristics, including abundance, affordability, and environmental friendliness. Furthermore,n-type Mg3Sb2-based materials exhibit high TE performance because of their high band degeneracy in the conduction band minimum (CBM), and low …

Emergence Of Extreme Events In Nonlinear Oscillators Due To Parametric And External Excitations, Kaviya B

Theses and Dissertations

This comprehensive PhD thesis immerses itself in the intricate world of dynamical systems, aiming to understand, characterize, and develop innovative mitigation strategies for rare and extreme events occurring within diverse nonlinear oscillatory models. The term "events" spans a broad array of occurrences within defined systems, with "rare events" standing out as infrequent outliers or deviations from the norm.

Rare events span various disciplines such as oceanography, climate studies, biology, economics, ecology, encompassing phenomena like rogue waves, floods, cyclones, earthquakes, and financial crises. Recognized for their potential to cause substantial harm to both society and the environment, these events are widely …

Antioxidant, Photoprotective, And Cytotoxic Activities Of Tristaniopsis Merguensis Leaf Fractions With Molecular Docking Study Of Potential Fraction, Boima Situmeang, Respati Tri Swasono, Tri Joko Raharjo

Karbala International Journal of Modern Science

Through experimental along with molecular docking techniques of potential fraction, this study intended to evaluate the essential phytochemical elements of Tristaniopsis merguensis leaflets as well as potential antioxidant, photoprotective, along with cytotoxic activities. The DPPH and ABTS tests were used to evaluate the antioxidant efficacy of the n-hexane (HPF), ethyl acetate (EPF), and methanol (MPF) fractions. Using an in-vitro solar protection factor (SPF) assessment, the photoprotective ability of T. merguensis components against UV damage was examined. Subsequently, invitro cytotoxic research were carried out against MCF-7 cell line (breast cancer line) assay. This was followed by molecular docking stimulation testing against …