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Articles 1 - 30 of 3975

Full-Text Articles in Physical Sciences and Mathematics

Maximising Social Welfare In Selfish Multi-Modal Routing Using Strategic Information Design For Quantal Response Travelers, Sainath Sanga Aug 2022

Maximising Social Welfare In Selfish Multi-Modal Routing Using Strategic Information Design For Quantal Response Travelers, Sainath Sanga

Masters Theses

"Traditional selfish routing literature quantifies inefficiency in transportation systems with single-attribute costs using price-of-anarchy (PoA), and provides various technical approaches (e.g. marginal cost pricing) to improve PoA of the overall network. Unfortunately, practical transportation systems have dynamic, multi-attribute costs and the state-of-the-art technical approaches proposed in the literature are infeasible for practical deployment. In this paper, we offer a paradigm shift to selfish routing via characterizing idiosyncratic, multiattribute costs at boundedly-rational travelers, as well as improving network efficiency using strategic information design. Specifically, we model the interaction between the system and travelers as a Stackelberg game, where travelers adopt multi-attribute …


Using Coherence And Interference To Study The Few Body Dynamics In Simple Atomic Collisions Systems, Sujan Bastola Aug 2022

Using Coherence And Interference To Study The Few Body Dynamics In Simple Atomic Collisions Systems, Sujan Bastola

Doctoral Dissertations

"Atomic Collision experiments are best suited to sensitively test the few-body dynamics of simple systems. The few-body dynamics, in turn, can be sensitively affected by interference effects. However, an important requirement to observe interference effects in atomic scattering experiments is that the incoming projectile beam must be coherent. The coherence properties of the incoming projectile can be controlled by the geometry of the collimating slit placed before the target. We performed a kinematically complete experiment where a 75 keV proton beam is crossed with a molecular hydrogen beam to study the dissociative capture process. The motivation for this project was …


Social Media Analytics With Applications In Disaster Management And Covid-19 Events, Md Yasin Kabir Aug 2022

Social Media Analytics With Applications In Disaster Management And Covid-19 Events, Md Yasin Kabir

Doctoral Dissertations

"Social media such as Twitter offers a tremendous amount of data throughout an event or a disastrous situation. Leveraging social media data during a disaster is beneficial for effective and efficient disaster management. Information extraction, trend identification, and determining public reactions might help in the future disaster or even avert such an event. However, during a disaster situation, a robust system is required that can be deployed faster and process relevant information with satisfactory performance in real-time. This work outlines the research contributions toward developing such an effective system for disaster management, where it is paramount to develop automated machine-enabled …


Secured Information Dissemination And Misbehavior Detection In Vanets, Ayan Roy Aug 2022

Secured Information Dissemination And Misbehavior Detection In Vanets, Ayan Roy

Doctoral Dissertations

"In a connected vehicle environment, the vehicles in a region can form a distributed network (Vehicular Ad-hoc Network or VANETs) where they can share traffic-related information such as congestion or no-congestion with other vehicles within its proximity, or with a centralized entity via. the roadside units (RSUs). However, false or fabricated information injected by an attacker (or a malicious vehicle) within the network can disrupt the decision-making process of surrounding vehicles or any traffic-monitoring system. Since in VANETs the size of the distributed network constituting the vehicles can be small, it is not difficult for an attacker to propagate an …


Survivor Bond Models For Securitizing Longevity Risk, Priscilla Mansah Codjoe Aug 2022

Survivor Bond Models For Securitizing Longevity Risk, Priscilla Mansah Codjoe

Doctoral Dissertations

"Longevity risk is the risk that a reference population’s mortality rates deviate from what is projected from prior life tables. This is due to discoveries in biological sciences, improved public health measures, and nutrition, which have dramatically increased life expectancy. Longevity risk raises life insurers’ liability, increasing product costs and reserves. Securitization through longevity derivatives is a way of dealing with this risk.

To enhance the pricing of life contingent products, we present an additive type mortality model in the style of the Lee-Carter. This model incorporates policyholder covariates. By using counting processes and martingale machinery, we obtain close form …


Semiparametric Estimation With Clustered Right Censored Data Via Multivariate Gaussian Random Fields, Fathima Zahra Sainul Abdeen Aug 2022

Semiparametric Estimation With Clustered Right Censored Data Via Multivariate Gaussian Random Fields, Fathima Zahra Sainul Abdeen

Doctoral Dissertations

Consider a fixed number of clustered areas identified by their geographical coordinate that are monitored for the occurrences of an event such as pandemic, epidemic, migration to name a few. Data collected on units at all areas include time varying covariates and other environmental factors that may affect event occurrences. The event times in every area can be independent. They can also be correlated with correlation between two units induced by an unobservable frailty. In both cases, the collected data is considered pairwise to account for spatial correlation between all pair of areas. The pairwise right censored data is probit-transformed …


Hydroclimate Variability In Central America During The Holocene Inferred From Lacustrine Sediments In Lake Izabal, Eastern Guatemala, Edward Fernando Duarte Aug 2022

Hydroclimate Variability In Central America During The Holocene Inferred From Lacustrine Sediments In Lake Izabal, Eastern Guatemala, Edward Fernando Duarte

Doctoral Dissertations

"Holocene hydroclimate reconstructions have contributed to our understanding of the mechanisms controlling precipitation in Central America. Recent hydroclimate proxy records from the region, however, have revealed considerable spatiotemporal complexity in precipitation variability. This complexity is hypothesized to result from the interaction between multiple oceanic-atmospheric processes that converge in the region. This project analyzed three sediment cores from Lake Izabal, eastern lowland Guatemala, with the goal of understanding changes in precipitation, lake productivity, and lake water chemistry during the Holocene. Our proxy results indicate that precipitation in the region increased from the early to the middle Holocene, when Lake Izabal became …


Temporal Lidar Scanning In Quantifying Cumulative Rockfall Volume And Hazard Assessment: A Case Study At Southwestern Saudi Arabia, Abdullah A. Alotaibi, Norbert H. Maerz, Kenneth J. Boyko, Ahmed M. Youssef, Biswajeet Pradhan Aug 2022

Temporal Lidar Scanning In Quantifying Cumulative Rockfall Volume And Hazard Assessment: A Case Study At Southwestern Saudi Arabia, Abdullah A. Alotaibi, Norbert H. Maerz, Kenneth J. Boyko, Ahmed M. Youssef, Biswajeet Pradhan

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Rockfalls and unstable slopes pose a serious threat to people and property along roads/highways in the southwestern mountainous regions of Saudi Arabia. In this study, the application of terrestrial light detection and ranging (LiDAR) technology was applied aiming to propose a strategy to analyze and accurately depict the detection of rockfall changes, calculation of rockfall volume, and evaluate rockfall hazards along the Habs Road, Jazan Region, Saudi Arabia. A series of temporal LiDAR scans were acquired at three selected sites. Our results show that these three sites have different degrees of hazard due to their geological differences. The mean volume …


Equilibrium And Dynamic Surface Tension Behavior In Colloidal Unimolecular Polymers (Cup), Ashish Zore, Peng Geng, Michael R. Van De Mark Jun 2022

Equilibrium And Dynamic Surface Tension Behavior In Colloidal Unimolecular Polymers (Cup), Ashish Zore, Peng Geng, Michael R. Van De Mark

Chemistry Faculty Research & Creative Works

Studies of the interfacial behavior of pure aqueous nanoparticles have been limited due tothe difficulty of making contaminant-free nanoparticles while also providing narrow size distribu-tion. Colloidal unimolecular polymers (CUPs) are a new type of single-chain nanoparticle with a particle size ranging from 3 to 9 nm, which can be produced free of surfactants and volatile organic contents (VOCs). CUP particles of different sizes and surface charges were made. The surface tension behavior of these CUP particles in water was studied using a maximum bubble pressure tensiometer. The equilibrium surface tension decreased with increasing concentration and the number of charges present …


Techno-Economic Feasibility Analysis Of A Fully Mobile Radiation Oncology System Using Monte Carlo Simulation, Alex T. Price, Casey I. Canfield, Geoffrey D. Hugo, James A. Kavanaugh, Lauren E. Henke, Eric Laugeman, Pamela Samson, Clair Reynolds-Kueny, Elizabeth A. Cudney May 2022

Techno-Economic Feasibility Analysis Of A Fully Mobile Radiation Oncology System Using Monte Carlo Simulation, Alex T. Price, Casey I. Canfield, Geoffrey D. Hugo, James A. Kavanaugh, Lauren E. Henke, Eric Laugeman, Pamela Samson, Clair Reynolds-Kueny, Elizabeth A. Cudney

Engineering Management and Systems Engineering Faculty Research & Creative Works

PURPOSEDisparities in radiation oncology (RO) can be attributed to geographic location, socioeconomic status, race, sex, and other societal factors. One potential solution is to implement a fully mobile (FM) RO system to bring radiotherapy to rural areas and reduce barriers to access. We use Monte Carlo simulation to quantify techno-economic feasibility with uncertainty, using two rural Missouri scenarios.METHODSRecently, a semimobile RO system has been developed by building an o-ring linear accelerator (linac) into a mobile coach that is used for temporary care, months at a time. Transitioning to a more FM-RO system, which changes location within a given day, presents …


Defining The Collapse Point In Colloidal Unimolecular Polymer (Cup) Formation, Ashish Zore, Peng Geng, Yuwei Zhang, Michael R. Van De Mark May 2022

Defining The Collapse Point In Colloidal Unimolecular Polymer (Cup) Formation, Ashish Zore, Peng Geng, Yuwei Zhang, Michael R. Van De Mark

Chemistry Faculty Research & Creative Works

Colloidal unimolecular polymer (CUP) particles were made using polymers with different ratios of hydrophobic and hydrophilic monomers via a self-organization process known as water reduction. The water-reduction process and the collapse of the polymer chain to form a CUP were tracked using viscosity measurements as a function of composition. A vibration viscometer, which allowed for viscosity measurement as the water was being added during the water-reduction process, was utilized. The protocol was optimized and tested for factors such as temperature control, loss of material, measurement stability while stirring, and changes in the solution volume with the addition of water. The …


Stability For Generalized Caputo Proportional Fractional Delay Integro-Differential Equations, Martin Bohner, Snezhana Hristova Mar 2022

Stability For Generalized Caputo Proportional Fractional Delay Integro-Differential Equations, Martin Bohner, Snezhana Hristova

Mathematics and Statistics Faculty Research & Creative Works

A scalar nonlinear integro-differential equation with time-variable and bounded delays and generalized Caputo proportional fractional derivative is considered. The main goal of this paper is to study the stability properties of the zero solution. Results are given concerning stability, exponential stability, asymptotic stability, and boundedness of solutions. The investigations are based on an application of a quadratic Lyapunov function, its generalized Caputo proportional derivative, and a modification of the Razumikhin approach. Some auxiliary properties of the generalized Caputo proportional derivative are proved. Five illustrative examples are included.


Potassic Volcanism Induced By Mantle Upwelling Through A Slab Window: Evidence From Shear Wave Splitting Analyses In Central Java, Fansheng Kong, Stephen S. Gao, Kelly H. Liu, Jiabiao Li Mar 2022

Potassic Volcanism Induced By Mantle Upwelling Through A Slab Window: Evidence From Shear Wave Splitting Analyses In Central Java, Fansheng Kong, Stephen S. Gao, Kelly H. Liu, Jiabiao Li

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

To delineate the mantle flow fields in the vicinity of a previously proposed slab window and the possible roles that they may play in the formation of potassic volcanism in Central Java, we conduct shear wave splitting analyses using both local S and teleseismic XKS waves (including SKS, SKKS, and PKS) recorded by 121 onshore stations and two ocean bottom seismometers (OBSs). The XKS fast orientations from the OBSs are trench normal and in accord with previous subslab anisotropy measurements. In the eastern part of Central Java, the XKS and local S fast orientations from the onshore stations are mostly …


Continental Break-Up Under A Convergent Setting: Insights From P Wave Radial Anisotropy Tomography Of The Woodlark Rift In Papua New Guinea, Youqiang Yu, Frederik Tilmann, Dapeng Zhao, Stephen S. Gao, Kelly H. Liu Mar 2022

Continental Break-Up Under A Convergent Setting: Insights From P Wave Radial Anisotropy Tomography Of The Woodlark Rift In Papua New Guinea, Youqiang Yu, Frederik Tilmann, Dapeng Zhao, Stephen S. Gao, Kelly H. Liu

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

To explore the dynamic mechanism of continental rifting within a convergent setting, we determine the first P wave radial anisotropic tomography beneath the Woodlark rift in southeastern Papua New Guinea, which develops within the obliquely colliding zone between the Australian and southwest Pacific plates. The rift zone is depicted as localized low-velocity anomalies with positive radial anisotropy, which rules out a dominant role of active mantle upwelling in promoting the rift development and favors passive rifting with decompression melting as main processes. Downwelling slab relics in the upper mantle bounding the rift zone are revealed based on observed high-velocity anomalies …


Oscillation Of Noncanonical Second-Order Advanced Differential Equations Via Canonical Transform, Martin Bohner, Kumar S. Vidhyaa, Ethiraju Thandapani Mar 2022

Oscillation Of Noncanonical Second-Order Advanced Differential Equations Via Canonical Transform, Martin Bohner, Kumar S. Vidhyaa, Ethiraju Thandapani

Mathematics and Statistics Faculty Research & Creative Works

In this paper, we develop a new technique to deduce oscillation of a second-order noncanonical advanced differential equation by using established criteria for second-order canonical advanced differential equations. We illustrate our results by presenting two examples.


Fully Differential Investigation Of Two-Center Interference In Dissociative Capture In P + H₂ Collisions, S. Bastola, M. Dhital, B. Lamichhane, A. Silvus, R. Lomsadze, J. Davis, A. Hasan, A. Igarashi, Michael Schulz Mar 2022

Fully Differential Investigation Of Two-Center Interference In Dissociative Capture In P + H₂ Collisions, S. Bastola, M. Dhital, B. Lamichhane, A. Silvus, R. Lomsadze, J. Davis, A. Hasan, A. Igarashi, Michael Schulz

Physics Faculty Research & Creative Works

We have measured and calculated fully differential cross sections for vibrational dissociation following capture in 75-keV p + H2 collisions. For a molecular orientation perpendicular to the projectile beam axis and parallel to the transverse momentum transfer we observe a pronounced interference structure. The positions of the interference extrema suggest that the interference term is afflicted with a phase shift which depends on the projectile scattering angle. However, no significant dependence on the kinetic-energy release was observed. Considerable discrepancies between our calculations and experimental data were found.


Guiding Of Kev Ions Between Two Insulating Parallel Plates, Robert D. Dubois, K. Tőkési, E. Giglio Mar 2022

Guiding Of Kev Ions Between Two Insulating Parallel Plates, Robert D. Dubois, K. Tőkési, E. Giglio

Physics Faculty Research & Creative Works

Experimental data are presented for low-energy singly charged ion transport between two insulating parallel plates. Using a beam intensity of approximately 20 pA, measurements of the incoming and transmitted beams provide quantitative temporal information about the charge deposited on the plates and the guiding probability. Using a smaller beam intensity (~ 1 pA) plate charging and discharging properties were studied as a function of time. These data imply that both the charge deposition and decay along the surface and through the bulk need to be modeled as acting independently. A further reduction of beam intensity to ~ 25 fA allowed …


Long-Range Interactions For Hydrogen Atoms In Excited D States, Chandra M. Adhikari, Ulrich D. Jentschura Mar 2022

Long-Range Interactions For Hydrogen Atoms In Excited D States, Chandra M. Adhikari, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

Pressure shifts inside an atomic beam are among the more theoretically challenging effects in high-precision measurements of atomic transitions. A crucial element in their theoretical analysis is the understanding of long-range interatomic interactions inside the beam. For excited reference states, the presence of quasi-degenerate states leads to additional challenges, due to the necessity to diagonalize large matrices in the quasi-degenerate hyperfine manifolds. Here, we focus on the interactions of hydrogen atoms in reference states composed of an excited nD state (atom A), and in the metastable 2S state (atom B). We devote special attention to the cases n = 3 …


Magic Wavelengths For 1s-Ns And 2s-Ns Transitions In Hydrogenlike Systems, Chandra M. Adhikari, Jonathan C. Canales, Thusitha P.W. Arthanayaka, Ulrich D. Jentschura Mar 2022

Magic Wavelengths For 1s-Ns And 2s-Ns Transitions In Hydrogenlike Systems, Chandra M. Adhikari, Jonathan C. Canales, Thusitha P.W. Arthanayaka, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We study the magic wavelength for two-photon 1S-nS transitions in a hydrogen and deuterium atom, as well as 2S-nS transitions, where the lower level is the metastable 2S state. At the magic wavelength, the dynamic Stark shifts of the ground and the excited state of the transition coincide, so that the transition frequency is independent of the intensity of the trapping laser field. Experimentally feasible magic wavelengths of transitions with small slopes in the atomic polarizabilities are determined; these are the most stable magic wavelengths against variations of the laser frequency. We provide data for the magic wavelengths for the …


Perceptions Of Violations By Artificial And Human Actors Across Moral Foundations, Timothy Maninger, Daniel Burton Shank Mar 2022

Perceptions Of Violations By Artificial And Human Actors Across Moral Foundations, Timothy Maninger, Daniel Burton Shank

Psychological Science Faculty Research & Creative Works

Artificial agents such as robots, chatbots, and artificial intelligence systems can be the perpetrators of a range of moral violations traditionally limited to human actors. This paper explores how people perceive the same moral violations differently for artificial agent and human perpetrators by addressing three research questions: How wrong are moral foundation violations by artificial agents compared to human perpetrators? Which moral foundations do artificial agents violate compared to human perpetrators? What leads to increased blame for moral foundation violations by artificial agents compared to human perpetrators? We adapt 18 human-perpetrated moral violation scenarios that differ by the moral foundation …


Computational Study On The Microscopic Adsorption Characteristics Of Linear Alkylbenzene Sulfonates With Different Chain Lengths On Anthracite Surface, Xuanlai Chen, Guochao Yan, Guang Xu, Xianglin Yang, Jinfa Dong, Zidong Liang, Shuai Wei Feb 2022

Computational Study On The Microscopic Adsorption Characteristics Of Linear Alkylbenzene Sulfonates With Different Chain Lengths On Anthracite Surface, Xuanlai Chen, Guochao Yan, Guang Xu, Xianglin Yang, Jinfa Dong, Zidong Liang, Shuai Wei

Mining Engineering Faculty Research & Creative Works

In order to explore the influence of different lengths of hydrophobic carbon chains on the diffusion characteristics of surfactants on the surface of anthracite, six linear alkyl benzene sulfonates with different hydrophobic carbon chain lengths were selected (mC, m = 8, 10, 12, 14, 16, 18; m represents the numbers of carbon atoms in the hydrophobic carbon chain), and molecular dynamics (MD) simulations were adopted. Models of surfactant-anthracite, surfactant-graphite layer, and water-surfactant-anthracite were constructed. After analyzing a series of properties such as adsorption energy, diffusion coefficient, radial distribution function (RDF), and hydrophobic tail order parameters, it was found that 12C …


Prediction Of Soil Water Content And Electrical Conductivity Using Random Forest Methods With Uav Multispectral And Ground-Coupled Geophysical Data, Yunyi Guan, Katherine R. Grote, Joel Schott, Kelsi Leverett Feb 2022

Prediction Of Soil Water Content And Electrical Conductivity Using Random Forest Methods With Uav Multispectral And Ground-Coupled Geophysical Data, Yunyi Guan, Katherine R. Grote, Joel Schott, Kelsi Leverett

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The volumetric water content (VWC) of soil is a critical parameter in agriculture, as VWC strongly influences crop yield, provides nutrients to plants, and maintains the microbes that are needed for the biological health of the soil. Measuring VWC is difficult, as it is spatially and tempo-rally heterogeneous, and most agricultural producers use point measurements that cannot fully capture this parameter. Electrical conductivity (EC) is another soil parameter that is useful in agricul-ture, since it can be used to indicate soil salinity, soil texture, and plant nutrient availability. Soil EC is also very heterogeneous; measuring EC using conventional soil sampling …


Noninvasive Detection, Tracking, And Characterization Of Aerogel Implants Using Diagnostic Ultrasound, Sagar Ghimire, Martina Rodriguez Sala, Swetha Chandrasekaran, Grigorios Raptopoulos, Marcus Worsley, Patrina Paraskevopoulou, Nicholas Leventis, Firouzeh Sabri Feb 2022

Noninvasive Detection, Tracking, And Characterization Of Aerogel Implants Using Diagnostic Ultrasound, Sagar Ghimire, Martina Rodriguez Sala, Swetha Chandrasekaran, Grigorios Raptopoulos, Marcus Worsley, Patrina Paraskevopoulou, Nicholas Leventis, Firouzeh Sabri

Chemistry Faculty Research & Creative Works

Medical implants are routinely tracked and monitored using different techniques, such as MRI, X‐ray, and ultrasound. Due to the need for ionizing radiation, the two former methods pose a significant risk to tissue. Ultrasound imaging, however, is non‐invasive and presents no known risk to human tissue. Aerogels are an emerging material with great potential in biomedical implants. While qualitative observation of ultrasound images by experts can already provide a lot of infor-mation about the implants and the surrounding structures, this paper describes the development and study of two simple B‐Mode image analysis techniques based on attenuation measurements and echogenicity comparisons, …


Special Issue: Microbiota-Gut-Brain Axis, Mark Obrenovich, Prakash Reddy Feb 2022

Special Issue: Microbiota-Gut-Brain Axis, Mark Obrenovich, Prakash Reddy

Chemistry Faculty Research & Creative Works

No abstract provided.


Metallic Networks And Hydrogen Compensation In Highly Nonstoichiometric Amorphous In₂O₃₋ₓ, Julia E. Medvedeva, E. Caputa-Hatley, I. Zhuravlev Feb 2022

Metallic Networks And Hydrogen Compensation In Highly Nonstoichiometric Amorphous In₂O₃₋ₓ, Julia E. Medvedeva, E. Caputa-Hatley, I. Zhuravlev

Physics Faculty Research & Creative Works

The unique response of amorphous ionic oxides to changes in oxygen stoichiometry is investigated using computationally intensive ab initio molecular dynamics simulations, comprehensive structural analysis, and hybrid density-functional calculations for the oxygen defect formation energy and electronic properties of amorphous In2O3-x with x = 0-0.185. In marked contrast to nonstoichiometric crystalline nanocomposites with clusters of metallic inclusions inside an insulating matrix, the lack of oxygen in amorphous indium oxide is distributed between a large fraction of undercoordinated In atoms, leading to an extended shallow state for x < 0.037, a variety of weakly and strongly localized states for 0.074 < x < 0.148, and a percolation-like network of single-atom chains of metallic In-In bonds for x > 0.185. The calculated carrier concentration increases from 3.3 x 10 …


Collisional Excitation And Non-Lte Modeling Of Interstellar Chiral Propylene Oxide, Karlis Dzenis, Alexandre Faure, B. A. Mcguire, A. J. Remijan, P. J. Dagdigian, C. Rist, Richard Dawes, Ernesto Quintas-Sánchez, F. Lique, M. Hochlaf Feb 2022

Collisional Excitation And Non-Lte Modeling Of Interstellar Chiral Propylene Oxide, Karlis Dzenis, Alexandre Faure, B. A. Mcguire, A. J. Remijan, P. J. Dagdigian, C. Rist, Richard Dawes, Ernesto Quintas-Sánchez, F. Lique, M. Hochlaf

Chemistry Faculty Research & Creative Works

The first set of theoretical rotational cross sections for propylene oxide (CH3CHCH2O) colliding with cold He atoms has been obtained at the full quantum level using a high-accuracy potential energy surface. By scaling the collision reduced mass, rotational rate coefficients for collisions with para-H2 are deduced in the temperature range 5-30 K. These collisional coefficients are combined with radiative data in a non-LTE radiative transfer model in order to reproduce observations of propylene oxide made toward the Sagittarius B2(N) molecular cloud with the Green Bank and Parkes radio telescopes. The three detected absorption lines are …


The Shepherd Mountain Iron Ore Deposit In Southeast Missouri, Usa -- An Extension Of The Pilot Knob Magmatic-Hydrothermal Ore System: Evidence From Iron Oxide Chemistry, Bolorchimeg N. Tunnell, Marek Locmelis, Cheryl Seeger, Marilena Moroni, Sarah Dare, Ryan Mathur, Brandon Sullivan Feb 2022

The Shepherd Mountain Iron Ore Deposit In Southeast Missouri, Usa -- An Extension Of The Pilot Knob Magmatic-Hydrothermal Ore System: Evidence From Iron Oxide Chemistry, Bolorchimeg N. Tunnell, Marek Locmelis, Cheryl Seeger, Marilena Moroni, Sarah Dare, Ryan Mathur, Brandon Sullivan

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The Southeast Missouri Iron Metallogenic Province in the Midcontinent USA contains seven major and several minor IOA/IOCG-type deposits and a series of shallow vein-type deposits/prospects, all of which are spatially and temporally associated with early Mesoproterozoic (1500–1440 Ma) magmatism in the St. Francois Mountains terrane. One of the vein-type deposits is the Shepherd Mountain deposit, which consists of two northeast-trending ore veins dominated by magnetite and lesser amounts of hematite. Here we report the findings of a study that investigates the origin of the Shepherd Mountain deposit and a possible genetic link to the nearby (i.e., < 5 km away) magmatic to magmatic-hydrothermal Pilot Knob ore system that comprises the massive-to-disseminated Pilot Knob Magnetite deposit and the overlying bedded and brecciated Pilot Knob Hematite deposit. Petrographic observations, whole-rock data and the trace element and Fe isotope composition of magnetite and hematite show that the Shepherd Mountain deposit formed from at least five pulses of magmatic-hydrothermal fluids with different compositions and physicochemical parameters. Integration of the data for the Shepherd Mountain deposit with new and published data from the Pilot Knob Magnetite and Pilot Knob Hematite deposits shows that the three deposits are genetically linked through two local faults. The Ironton and Pilot Knob faults provided fluid pathways that connected the Pilot Knob Magnetite deposit to the shallower Shepherd Mountain and Pilot Knob Hematite deposits. Consequently, we argue that the Shepherd Mountain and Pilot Knob Hematite deposits are near-surface extensions of the same magmatic to hydrothermal plumbing system that formed the Pilot Knob Magnetite deposit at depth.


Characterization Of Single-Shot Attosecond Pulses With Angular Streaking Photoelectron Spectra, Xi Zhao, Siqi Li, Taran Driver, Van Hung Hoang, Anh-Thu Le, James P. Cryan, Agostino Marinelli, C. D. Lin Jan 2022

Characterization Of Single-Shot Attosecond Pulses With Angular Streaking Photoelectron Spectra, Xi Zhao, Siqi Li, Taran Driver, Van Hung Hoang, Anh-Thu Le, James P. Cryan, Agostino Marinelli, C. D. Lin

Physics Faculty Research & Creative Works

Most of the traditional attosecond pulse retrieval algorithms are based on a so-called attosecond streak camera technique, in which the momentum of the electron is shifted by an amount depending on the relative time delay between the attosecond pulse and the streaking infrared pulse. Thus, temporal information of the attosecond pulse is encoded in the amount of momentum shift in the streaked photoelectron momentum spectrogram S(p, τ), where p is the momentum of the electron along the polarization direction and τ is the time delay. An iterative algorithm is then employed to reconstruct the attosecond pulse from the streaking spectrogram. …


Search For Continuous Gravitational Waves From 20 Accreting Millisecond X-Ray Pulsars In O3 Ligo Data, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jan 2022

Search For Continuous Gravitational Waves From 20 Accreting Millisecond X-Ray Pulsars In O3 Ligo Data, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Results are presented of searches for continuous gravitational waves from 20 accreting millisecond x-ray pulsars with accurately measured spin frequencies and orbital parameters, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. The search algorithm uses a hidden Markov model, where the transition probabilities allow the frequency to wander according to an unbiased random walk, while the J-statistic maximum-likelihood matched filter tracks the binary orbital phase. Three narrow subbands are searched for each target, centered on harmonics of the measured spin frequency. The search yields 16 candidates, consistent with a false alarm probability of …


Stripe Order, Impurities, And Symmetry Breaking In A Diluted Frustrated Magnet, Xuecheng Ye, Rajesh Narayanan, Thomas Vojta Jan 2022

Stripe Order, Impurities, And Symmetry Breaking In A Diluted Frustrated Magnet, Xuecheng Ye, Rajesh Narayanan, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the behavior of the frustrated J1-J2 Ising model on a square lattice under the influence of random dilution and spatial anisotropies. Spinless impurities generate a random-field type disorder for the spin-density wave (stripe) order parameter. These random fields destroy the long-range stripe order in the case of spatially isotropic interactions. Combining symmetry arguments, percolation theory, and large-scale Monte Carlo simulations, we demonstrate that arbitrarily weak spatial interaction anisotropies restore the stripe phase. More specifically, the transition temperature Tc into the stripe phase depends on the interaction anisotropy ΔJ via Tc∼1/|ln(ΔJ)| for small …