Physical Sciences and Mathematics Commons^™

Inferring Late-Holocene Climate In The Ecuadorian Andes Using A Chironomid-Based Temperature Inference Model, Frazer Matthews-Bird, Stephen J. Brooks, Philip B. Holden, Encarni Montoya, William D. Gosling

Ocean Engineering and Marine Sciences Faculty Publications

Presented here is the first chironomid calibration data set for tropical South America. Surface sediments were collected from 59 lakes across Bolivia (15 lakes), Peru (32 lakes), and Ecuador (12 lakes) between 2004 and 2013 over an altitudinal gradient from 150 m above sea level (a.s.l) to 4655 m a.s.l, between 0–17° S and 64–78° W. The study sites cover a mean annual temperature (MAT) gradient of 25 °C. In total, 55 chironomid taxa were identified in the 59 calibration data set lakes. When used as a single explanatory variable, MAT explains 12.9 % of the variance (λ1/λ2 =  1.431). …

Environmental Controls On The Distribution And Diversity Of Lentic Chironomidae (Insecta: Diptera) Across An Altitudinal Gradient In Tropical South America, Frazer Matthews-Bird, William D. Gosling, Angela L. Coe, Mark Bush, Francis E. Mayle, Yarrow Axford, Stephen J. Brooks

Ocean Engineering and Marine Sciences Faculty Publications

To predict the response of aquatic ecosystems to future global climate change, data on the ecology and distribution of keystone groups in freshwater ecosystems are needed. In contrast to mid- and high-latitude zones, such data are scarce across tropical South America (Neotropics). We present the distribution and diversity of chironomid species using surface sediments of 59 lakes from the Andes to the Amazon (0.1–17°S and 64–78°W) within the Neotropics. We assess the spatial variation in community assemblages and identify the key variables influencing the distributional patterns. The relationships between environmental variables (pH, conductivity, depth, and sediment organic content), climatic data, …

Benthic Marine Calcifiers Coexist With Caco3-Undersaturated Seawater Worldwide, Mario Lebrato, Andreas J. Andersson, Justin Baker Ries, Richard B. Aronson, Miles D. Lamare, Wolfgang Koeve, Andreas Oschlies, Maria Débora Iglesias-Rodríguez, Sven Thatje, M. Amsler, Stephanie C. Vos, D. O. B. Jones, H. A. Ruhl, A. R. Gates, J. B. Mcclintock

Ocean Engineering and Marine Sciences Faculty Publications

Ocean acidification and decreasing seawater saturation state with respect to calcium carbonate (CaCO3) minerals have raised concerns about the consequences to marine organisms that build CaCO3 structures. A large proportion of benthic marine calcifiers incorporate Mg2+ into their skeletons (Mg-calcite), which, in general, reduces mineral stability. The relative vulnerability of some marine calcifiers to ocean acidification appears linked to the relative solubility of their shell or skeletal mineralogy, although some organisms have sophisticated mechanisms for constructing and maintaining their CaCO3 structures causing deviation from this dependence. Nevertheless, few studies consider seawater saturation state with respect to the actual Mg-calcite mineralogy …

Atmospheric Sensitivity To Roughness Length In A Regional Atmospheric Model Over The Ohio-Tennessee River Valley, Rezaul Mahmood

School of Natural Resources: Faculty Publications

No abstract provided.

The Metal/Organic Interface In Cobalt/Vinylidene Fluoride Heterostructures, Keith Foreman, E Echeverria, Mark A. Koten, R. M. Lindsay, N. Hong, Jeffrey E. Shield, Shireen Adenwalla

Shireen Adenwalla Papers

Organic-based electronic devices are rapidly increasing in popularity, making it essential to understand and characterize the interface between organic materials and metallic electrodes. This work reports on the characterization of the interface between thin films of an emerging organic ferroelectric, vinylidene fluoride (VDF) oligomer, and Co, an important high Curie temperature ferromagnet. Using a wide battery of experimental techniques, it is shown that VDF oligomer thin films as thin as 15 nm can halt, or prevent, Co oxidization in atmospheric conditions, a necessary condition for device applications. Selectivity of magnetic properties, such as remanent magnetization, is enabled by the clarification …

Ferroelectric Characterization And Growth Optimization Of Thermally Evaporated Vinylidene Fluoride Thin Films, Keith Foreman, N. Hong, C. Labedz, C. Shearer, Stephen Ducharme, Shireen Adenwalla

Shireen Adenwalla Papers

Organic thin films have numerous advantages over inorganics in device processing and price. The large polarization of the organic ferroelectric oligomer vinylidene fluoride (VDF) could prove useful for both device applications and the investigation of fundamental physical phenomena. A VDF oligomer thin film vacuum deposition process, such as thermal evaporation, preserves film and interface cleanliness, but is challenging, with successful deposition occurring only within a narrow parameter space. We report on the optimal deposition parameters for VDF oligomer thin films, refining the parameter space for successful deposition, resulting in a high yield of robust ferroelectric films. In particular, we investigate …

Theory Of Magnon Motive Force In Chiral Ferromagnets, Utkan Güngördü, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We predict that magnon motive force can lead to temperature dependent, nonlinear chiral damping in both conducting and insulating ferromagnets. We estimate that this damping can significantly influence the motion of skyrmions and domain walls at finite temperatures. We also find that in systems with low Gilbert damping moving chiral magnetic textures and resulting magnon motive forces can induce large spin and energy currents in the transverse direction.

Stability Of Skyrmion Lattices And Symmetries Of Quasi-Two-Dimensional Chiral Magnets, Utkan Güngördü, Rabindra Nepal, Oleg A. Tretiakov, Kirill D. Belashchenko, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

Recently there has been substantial interest in realizations of skyrmions, in particular in quasi-two-dimensional (2D) systems due to increased stability resulting from reduced dimensionality. A stable skyrmion, representing the smallest realizable magnetic texture, could be an ideal element for ultradense magnetic memories. Here we use the most general form of the quasi-2D free energy with Dzyaloshinskii-Moriya interactions constructed from general symmetry considerations reflecting the underlying system. We predict that the skyrmion phase is robust and it is present even when the system lacks the in-plane rotational symmetry. In fact, the lowered symmetry leads to increased stability of vortex-antivortex lattices with …

Magnetoelectric Domain Wall Dynamics And Its Implications For Magnetoelectric Memory, Kirill D. Belashchenko, Oleg Tchernyshyov, Alexey Kovalev, Oleg A. Tretiakov

Department of Physics and Astronomy: Faculty Publications

Domain wall dynamics in a magnetoelectric antiferromagnet is analyzed, and its implications for magnetoelectric memory applications are discussed. Cr₂O₃ is used in the estimates of the materials parameters. It is found that the domain wall mobility has a maximum as a function of the electric field due to the gyrotropic coupling induced by it. In Cr₂O₃, the maximal mobility of 0.1 m/(s Oe) is reached at E = 0.06 V/nm. Fields of this order may be too weak to overcome the intrinsic depinning field, which is estimated for B-doped Cr₂O_{3 …}

Measurement Of The Differential Cross Section And Charge Asymmetry For Inclusive Pp → W± + X Production At √S = 8 Tev, Ekaterina Avdeeva, Rachel Bartek, Kenneth A. Bloom, Suvadeep Bose, Daniel R. Claes, Aaron Dominguez, Caleb Fangmeier, Rebeca Gonzalez Suarez, Rami Kamalieddin, Daniel Knowlton, Ilya Kravchenko, Jose Monroy, F. Meier, F. Ratnikov, J. E. Siado, Gregory Snow, B. Stieger, Cms Collaboration

Department of Physics and Astronomy: Faculty Publications

The differential cross section and charge asymmetry for inclusive pp → W^± + X → μ^±ν + X production at √s = 8 TeV are measured as a function of muon pseudorapidity. The data sample corresponds to an integrated luminosity of 18.8 fb⁻¹ recorded with the CMS detector at the LHC. These results provide important constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from 10⁻³ to 10⁻¹.

Sliding Mode Observers For Distributed Parameter Systems: Theory And Applications, Niloofar Nasiri Kamran

Doctoral Dissertations and Master's Theses

Many processes in nature and industry can be described by partial differential equations. PDEs employ quantities such as density, temperature, velocity, etc. and their partial derivatives to model these phenomena. However, in the case of distributed parameter systems, it is not always possible to have access to the states of the systems due to technical difficulties such as lack of sensors. Therefore, there is the need for state observers to estimate the states of the system only having the output of the system available. In this research, the theory of sliding mode and variable structure systems are employed in order …

Construction Of An Optical Fiber Strian Gauge, Najwa Sulaiman

Master's Theses and Doctoral Dissertations

This project is focused on the construction of an optical fiber strain gauge that is based on a strain gauge described by Butter and Hocker. Our gauge is designed to generate an interference pattern from the signals carried on two bare single-mode fibers that are fastened to an aluminum cantilever. When the cantilever experiences flexural stress, the interference pattern should change. By observing this change, it is possible to determine the strain experienced by the cantilever. I describe the design and construction of our optical fiber strain gauge as well as the characterization of different parts of the apparatus.

Full State Revivals In Linearly Coupled Chains With Commensurate Eigenspectra, J. J. P. Veerman, Jovan Petrovic

Mathematics and Statistics Faculty Publications and Presentations

Coherent state transfer is an important requirement in the construction of quantum computer hardware. The state transfer can be realized by linear next-neighbour-coupled finite chains. Starting from the commensurability of chain eigenvalues as the general condition of periodic dynamics, we find chains that support full periodic state revivals. For short chains, exact solutions are found analytically by solving the inverse eigenvalue problem to obtain the coupling coefficients between chain elements. We apply the solutions to design optical waveguide arrays and perform numerical simulations of light propagation thorough realistic waveguide structures. Applications of the presented method to the realization of a …

Voxel Based Morphometry In Optical Coherence Tomography: Validation & Core Findings, Bhavna J. Antony, Min Chen, Aaron Carass, Bruno M. Jedynak, Omar Al-Louzi, Sharon D. Solomon, Shiv Saidha, Peter Calabresi, Jerry L. Prince

Mathematics and Statistics Faculty Publications and Presentations

Optical coherence tomography (OCT) of the human retina is now becoming established as an important modality for the detection and tracking of various ocular diseases. Voxel based morphometry (VBM) is a long standing neuroimaging analysis technique that allows for the exploration of the regional differences in the brain. There has been limited work done in developing registration based methods for OCT, which has hampered the advancement of VBM analyses in OCT based population studies. Following on from our recent development of an OCT registration method, we explore the potential benefits of VBM analysis in cohorts of healthy controls (HCs) and …

Building Resiliency In Response To Sea Level Rise And Recurrent Flooding: Comprehensive Planning In Hampton Roads, Joshua G. Behr, Rafael Diaz, Molly Mitchell

VMASC Publications

[Introduction]

Over the past few decades, the Hampton Roads region, with its extensive coastline, has been experiencing more frequent flooding from surges and precipitation caused by tropical storms, nor’easters and heavy thunderstorms (Figure 1). Recurrent flooding is “flooding that occurs repeatedly in the same area over time due to precipitation events, high tides or storm surge.”¹ The recurrence of tidal/surge flooding in Hampton Roads has increased from 1.7 days of “nuisance” flooding per year in 1960 to 7.3 days per year in 2014.² Although there is no definitive region-wide data to document the increases in precipitation-induced flooding, there …

Potential Benefits And Shortcomings Of Marine Protected Areas For Small Seabirds Revealed Using Miniature Tags, Sara M. Maxwell, Melinda G. Conners, Nicholas B. Sisson, Tiffany M. Dawson

Biological Sciences Faculty Publications

Marine protected areas are considered important tools for protecting marine biodiversity, and animal tracking is a key way to determine if boundaries are effectively placed for protection of key marine species, including seabirds. We tracked chick-rearing brown noddies (Anous stolidus) from the Dry Tortugas National Park in Florida USA in 2016 using 1.8 g Nanofix GPS tags (n = 10), making this the first time this species has ever been tracked. We determined movement parameters, such as flight speed, distance traveled and home range, and how birds used a complex of marine protected areas including the Dry Tortugas …

Are We Missing Important Areas In Pelagic Marine Conservation? Redefining Conservation Hotspots In The Ocean, Dana K. Briscoe, Sara M. Maxwell, Raphael Kudela, Larry B. Crowder

Biological Sciences Faculty Publications

The protection of biodiversity is one of the most important goals in terrestrial and marine conservation. Marine conservation approaches have traditionally followed the example of terrestrial initiatives. However, patterns, processes, habitats, and threats differ greatly between the 2 systems - and even within the marine environment. As a result, there is still a lack of congruence as to how to best identify and prioritize conservation approaches moving from the static terrestrial and nearshore realm into a more fluid, 3-dimensional pelagic realm. To address this problem, we investigate how the conservation science literature has been used to inform and guide management …

Geospatial Approaches To Support Pelagic Conservation Planning And Adaptive Management, L. M. Wedding, Sara M. Maxwell, D. Hyrenbach, D. C. Dunn, J. J. Roberts, D. Briscoe, E. Hines, P. N. Halpin

Biological Sciences Faculty Publications

Place-based management in the open ocean faces unique challenges in delineating boundaries around temporally and spatially dynamic systems that span broad geographic scales and multiple management jurisdictions, especially in the 'high seas'. Geospatial technologies are critical for the successful design of pelagic conservation areas, because they provide information on the spatially and temporally dynamic oceanographic features responsible for driving species distribution and abundance in the open ocean, the movements of protected species, and the spatial patterns of distribution of potential threats. Nevertheless, there are major challenges to implementing these geospatial approaches in the open ocean. This Theme Section seeks to …

Synthesis Of Dmap Tethered Polymer Chains For Reversible Micelle Formation, Richard Arthur Fredricks

Master's Theses and Doctoral Dissertations

Dimethylaminopyridine (DMAP) can act to catalyze numerous organic reactions. To increase its recovery and reuse, it has been tethered to dendrimers and to micellar systems, creating nano-scale catalytic pockets for reactions to proceed. Previously developed systems show diminished reactivity over time as the products of the reaction fill up the nano-scale reactor. Thus, the goal of my research is to use RAFT polymerization methods to synthesize a hydrophobic polymer chain bearing 4-methylaminopyridine units and to attach it to a hydrophilic polymer chain to create a polymer system capable of micelle formation in solution. These functionalized micelles are designed to be …

Instructors' Perceptions Of Their Students' Conceptions: The Case In Undergraduate Mathematics, Wes Maciejewski

Faculty Research, Scholarly, and Creative Activity

How a student conceives the nature of a subject they study affects the approach they take to that study and ultimately their learning outcome. This conception is shaped by prior experience with the subject and has a lasting impact on the student's learning. For subsequent education to be effective, an instructor must link the current topic to the student's prior knowledge. Short of assessing their students, an instructor relies on their subjective experience, intuitions, and perceptions about this prior knowledge. These perceptions shape the educational experience. The current study explores, in the context of undergraduate mathematics, the alignment of instructors' …

Electropolymerized Layersas Selective Membranesin First Generation Uric Acid Biosensors, Kaiwen Chen, Grace E. Conway, Gregory A. Hamilton, Matthew L. Trawick, Michael C. Leopold

Chemistry Faculty Publications

Electropolymerized films that can serve as semi-permeable membranes and provide selectivity within a xerogel-based, 1^stgeneration biosensor assembly are explored in this study. Layered biosensing schemes of this nature rely primarily upon an electropolymerized ad-layer to supplement the xerogel and provide effective selectivity for detection of a targeted analyte. While effective electropolymers have been established for glucose sensing, the adaptation of the strategy to other analytes of clinical importance hinges upon the systematic evaluation of electropolymerized films to identify a selective film. Uric acid is a key species in the diagnosis/monitoring of a number of diseases and conditions. An …

Tandem Mass Spectrometric Analysis Of Phosphoamino Acid-Metal Ion Complexes, Urmi Patel

All Capstone Projects

The complex of phosphoamino acid with metal ions was prepared by mixing both solutions and analyzed using ESI MS/MS technique. In this study, O-phospho-L-serine and O-phospho-L-tyrosine were used as phosphoamino acids and single charged metal ions such as Li+, Na+, K+, Rb+, Cs+ and Ag+ were used to study the dissociation patterns when combined with phosphoamino acid. The complexes were successfully fragmented in mass spectra using ESI MS/MS technique and the fragmentation products were studied and the dissociation patterns were proposed.

Geometric Algorithms For Modeling Protein Structures, Dan Zeng

Undergraduate Research Symposium Posters

Understanding the structures of macromolecular assemblies is necessary to describe the mechanics of a wide variety of cellular processes. Such assemblies often consist of hundreds of proteins and nucleic acid, each with a unique shape. Modern imaging techniques, including electron cryo-microscopy, create 3D density maps to portray the shapes of these assemblies. However, computational methods for deriving structural models from these images are not fully developed because structural geometry varies depending on the image resolution. To address this issue, we developed geometric algorithms in Gorgon, a molecular visualization software. First, we created an interface for Pathwalking. This algorithm determines protein …

Calculating The Observable Properties Of Mass Accreting Black Holes, Heather Lee

Undergraduate Research Symposium Posters

My goal is to generalize Chandrasekhar’s formulas to include partial Rayleigh Scattering. In my summer research, I successfully recalculated key tables and solutions from his book and I am working in generalizing his results for use in an infinitely deep electron atmosphere. Here, I will summarize how Chandrasekhar derived his formulas and how to potentially generalize them to include absorption.

Structure And Stability Of Primordial Stars, Aysel İbrahi̇m Karafi̇stan

Turkish Journal of Physics

For decades large-scale cosmic structures have been modeled as the gravitational amplification of small-density perturbations of the cosmological recombination epoch of the Big Bang. In astrophysics, cosmological nucleosynthesis is considered responsible for the production of the pristine gas, which should be found in the first-generation stars in the form of hydrogen and helium as the main constituents. In the later type of second-generation stars, hydrogen is converted into helium by the CN-cycle reactions, in which heavier elements are produced. These elements are believed to enrich the intergalactic medium by possible star bursts at the last stages of evolution. Stability criteria …

The Observational Status Of Simple Inflationary Models: An Update, Nobuchika Okada, Vedat Nefer Şenoğuz, Qaisar Shafi

Turkish Journal of Physics

We provide an update on five relatively well-motivated inflationary models in which the inflaton is a Standard Model singlet scalar field. These include i) the textbook quadratic and quartic potential models but with additional couplings of the inflaton to fermions and bosons, which enable reheating and also modify the naive predictions for the scalar spectral index $n_s$ and $r$, ii) models with Higgs and Coleman-Weinberg potentials, and finally iii) a quartic potential model with nonminimal coupling of the inflaton to gravity. For $n_s$ values close to 0.96, as determined by the WMAP9 and Planck experiments, most of the considered models …

Pp-Waves In Modified Gravity, Ahmet Baykal

Turkish Journal of Physics

The family of metrics corresponding to the plane-fronted gravitational waves with parallel propagation, commonly referred to as the family of pp-wave metrics, is studied in the context of various modified gravitational models in a self-contained and coherent manner by using a variant of the null coframe formulation of Newman and Penrose and the exterior algebra of differential forms on pseudo-Riemannian manifolds.

Supergravity Backgrounds And Symmetry Superalgebras, Ümi̇t Ertem

Turkish Journal of Physics

We consider the bosonic sectors of supergravity theories in ten and eleven dimensions corresponding to the low energy limits of string theories and M-theory. The solutions of supergravity field equations are known as supergravity backgrounds and the number of preserved supersymmetries in those backgrounds are determined by Killing spinors. We provide some examples of supergravity backgrounds that preserve different fractions of supersymmetry. An important invariant for the characterization of supergravity backgrounds is their Killing superalgebras, which are constructed out of Killing vectors and Killing spinors of the background. After constructing Killing superalgebras of some special supergravity backgrounds, we discuss the …

Neutron Stars: Compact Objects With Relativistic Gravity, Kazim Yavuz Ekşi̇

Turkish Journal of Physics

General properties of neutron stars are briefly reviewed with an emphasis on the indispensability of general relativity in our understanding of these fascinating objects. In Newtonian gravity the pressure within a star merely plays the role of opposing self-gravity. In general relativity all sources of energy and momentum contribute to the gravity. As a result, the pressure not only opposes gravity but also enhances it. The latter role of pressure becomes more pronounced with increasing compactness, $M/R$, where $M$ and $R$ are the mass and radius of the star, and sets a critical mass beyond which collapse is inevitable. This …

Exact Solutions To The Geodesic Equations Of Linear Dilaton Black Holes, Alan Hameed Hussein Hamo, Izzet Sakalli

Turkish Journal of Physics

In this paper, we analyze the geodesics of the 4-dimensional linear dilaton black hole (LDBH) spacetime, which is an exact solution to the Einstein-Maxwell-dilaton theory. LDBHs have nonasymptotically flat geometry, and their Hawking radiation is an isothermal process. The geodesics motions of the test particles are studied via the standard Lagrangian method. After obtaining the Euler-Lagrange equations, we show that exact analytical solutions to the radial and angular geodesic equations can be obtained. In particular, it is shown that one of the possible solutions for the radial trajectories can be given in terms of the Weierstrass P-function ($\wp $-function), which …