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Bottom-Up Trait-Mediated Indirect Effects Decrease Pathogen Transmission In A Tritrophic System, Bret D. Elderd Jan 2019

Bottom-Up Trait-Mediated Indirect Effects Decrease Pathogen Transmission In A Tritrophic System, Bret D. Elderd

Faculty Publications

© 2018 by the Ecological Society of America A plant's induction of secondary defenses helps to decrease herbivore damage by changing resource quality. While these chemical or physical defenses may directly decrease herbivory, they can also have indirect consequences. In a tritrophic system consisting of a plant, an insect herbivore, and an insect pathogen, plant based trait-mediated indirect effects (TMIEs) can alter host–pathogen interactions and, thereby, indirectly affect disease transmission. In a series of field experiments, individual soybean plants (Glycine max) were sprayed with either a jasmonic acid (JA) solution to trigger induction of plant defenses or a similar control …

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A Note On The Connectivity Of 2-Polymatroid Minors, Zachary Gershkoff, James Oxley Jan 2019

A Note On The Connectivity Of 2-Polymatroid Minors, Zachary Gershkoff, James Oxley

Faculty Publications

Brylawski and Seymour independently proved that if M is a connected matroid with a connected minor N, and e ∈ E(M) − E(N), then M\e or M/e is connected having N as a minor. This paper proves an analogous but somewhat weaker result for 2-polymatroids. Specifically, if M is a connected 2-polymatroid with a proper connected minor N, then there is an element e of E(M) − E(N) such that M\e or M/e is connected having N as a minor. We also consider what can be said about the uniqueness of the way in which the elements of E(M) − …

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Dependencies Among Dependencies In Matroids, James Oxley, Suijie Wang Jan 2019

Dependencies Among Dependencies In Matroids, James Oxley, Suijie Wang

Faculty Publications

In 1971, Rota introduced the concept of derived matroids to investigate “de-pendencies among dependencies” in matroids. In this paper, we study the derived matroid δM of an F-representation of a matroid M. The matroid δM has a naturally associated F-representation, so we can define a sequence δM, δ2M,. The main result classifies such derived sequences of matroids into three types: finite, cyclic, and divergent. For the first two types, we obtain complete characterizations and thereby resolve some of the questions that Longyear posed in 1980 for binary matroids. For the last type, the divergence is estimated by the coranks of …

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A Matroid Extension Result, James Oxley Jan 2019

A Matroid Extension Result, James Oxley

Faculty Publications

Adding elements to matroids can be fraught with difficulty. In the Vámos matroid V 8 , there are four pairs X 1 , X 2 , X 3 , and X 4 that partition E(V 8 ) such that (X 1 ∪ X 2 , X 3 ∪ X 4 ) is a 3-separation while exactly three of the local connectivities (X 1 , X 3 ), (X 1 , X 4 ), (X 2 , X 3 ), and (X 2 , X 4 ) are one, with the fourth being zero. As is well known, there is no …

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A Splitter Theorem For 3-Connected 2-Polymatroids, James Oxley, Charles Semple, Geoff Whittle Jan 2019

A Splitter Theorem For 3-Connected 2-Polymatroids, James Oxley, Charles Semple, Geoff Whittle

Faculty Publications

Seymour’s Splitter Theorem is a basic inductive tool for dealing with 3-connected matroids. This paper proves a generalization of that theorem for the class of 2-polymatroids. Such structures include matroids, and they model both sets of points and lines in a projective space and sets of edges in a graph. A series compression in such a structure is an analogue of contracting an edge of a graph that is in a series pair. A 2-polymatroid N is an s-minor of a 2-polymatroid M if N can be obtained from M by a sequence of contractions, series compressions, and dual-contractions, where …

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Performance Analysis Of A High-Sensitivity Multi-Pinhole Cardiac Spect System With Hemi-Ellipsoid Detectors, Narayan Bhusal, Joyoni Dey, Jingzhu Xu, Kesava Kalluri, Arda Konik, Joyeeta M. Mukherjee, P. Hendrik Pretorius Jan 2019

Performance Analysis Of A High-Sensitivity Multi-Pinhole Cardiac Spect System With Hemi-Ellipsoid Detectors, Narayan Bhusal, Joyoni Dey, Jingzhu Xu, Kesava Kalluri, Arda Konik, Joyeeta M. Mukherjee, P. Hendrik Pretorius

Faculty Publications

Purpose: Single-photon emission computed tomography (SPECT) is a noninvasive imaging modality, used in myocardial perfusion imaging. The challenges facing the majority of clinical SPECT systems are low sensitivity, poor resolution, and the relatively high radiation dose to the patient. New generation systems (GE Discovery, DSPECT) dedicated to cardiac imaging improve sensitivity by a factor of 5–8. This improvement can be used to decrease acquisition time and/or dose. However, in the case of ultra-low dose (~3 mCi) injections, acquisition times are still significantly long, taking 10–12 min. The purpose of this work is to investigate a new gamma camera design with …

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Simplicial Volume Of Links From Link Diagrams, Oliver Dasbach, Anastasiia Tsvietkova Jan 2019

Simplicial Volume Of Links From Link Diagrams, Oliver Dasbach, Anastasiia Tsvietkova

Faculty Publications

The hyperbolic volume of a link complement is known to be unchanged when a half-twist is added to a link diagram, and a suitable 3-punctured sphere is present in the complement. We generalise this to the simplicial volume of link complements by analysing the corresponding toroidal decompositions. We then use it to prove a refined upper bound for the volume in terms of twists of various lengths for links.

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The Gauss Decomposition Of Products Of Spherical Harmonics, Ricardo Estrada Jan 2019

The Gauss Decomposition Of Products Of Spherical Harmonics, Ricardo Estrada

Faculty Publications

The product of two homogeneous harmonic polynomials is homogeneous, but not harmonic, in general. We give formulas for the Gauss decomposition of the product of two homogeneous harmonic polynomials.

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The Funk-Hecke Formula, Harmonic Polynomials, And Derivatives Of Radial Distributions, Ricardo Estrada Jan 2019

The Funk-Hecke Formula, Harmonic Polynomials, And Derivatives Of Radial Distributions, Ricardo Estrada

Faculty Publications

We give a version of the Funk-Hecke formula that holds with minimal assumptons and apply it to obtain formulas for the distributional derivatives of radial distributions in Rn of the type Yk ∇ ∆j (f (r)), where Yk is a harmonic homogeneous polynomial. We show that such derivatives have simpler expressions than those of the form p ∇ (f (r)) for a general polynomial p.

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Backstepping Design For Output Feedback Stabilization For A Class Of Uncertain Systems, Frédéric Mazenc, Laurent Burlion, Michael Malisoff Jan 2019

Backstepping Design For Output Feedback Stabilization For A Class Of Uncertain Systems, Frédéric Mazenc, Laurent Burlion, Michael Malisoff

Faculty Publications

We construct bounded globally asymptotically stabilizing output feedbacks for a family of nonlinear systems, using a dynamic extension and a converging-input-converging-state assumption. We provide sufficient conditions for this assumption to hold, in terms of Lyapunov functions. The novelty is that our construction provides formulas for the control bounds while allowing uncertainties that prevent the use of classical backstepping, and cases where only part of the state variable is available for measurement, without requiring the time lagged states in the feedback control that were required in the artificial delays approach. We illustrate the relevance of our work to engineering in an …

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Diet Of Lesser Scaup Wintering On Lake Pontchartrain, Louisiana, Clay M. Stroud, Claire E. Caputo, Michael A. Poirrier, Kevin M. Ringelman Jan 2019

Diet Of Lesser Scaup Wintering On Lake Pontchartrain, Louisiana, Clay M. Stroud, Claire E. Caputo, Michael A. Poirrier, Kevin M. Ringelman

Faculty Publications

The lesser scaup Aythya affinis has been a species of conservation concern since continental breeding populations began declining in the 1980s. The causes of this decline are likely multifaceted, but cross-seasonal effects are believed to play a prominent role: females unable to acquire sufficient nutrient reserves during winter and spring migration have poor survival and breeding success. Understanding scaup diet composition and prey selection can help managers not only diagnose mechanisms underlying wintering scaup distributions, but may also help direct management actions to increase forage availability and quality. We evaluated the diet of 60 scaup collected from a major wintering …

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Calibrating A Taper Model For Oriental Spruce In Turkey, Ramazan Özçelik, Quang V. Cao, Hakkı Yavuz Jan 2019

Calibrating A Taper Model For Oriental Spruce In Turkey, Ramazan Özçelik, Quang V. Cao, Hakkı Yavuz

Faculty Publications

In this study, Max and Burkhart (1976)’s segmented taper model was used to describe stem profile and predict stem volume of oriental spruce in Turkey. Thirty procedures were evaluated, which include five fitting methods and six adjustment strategies. The fitting methods resulted in parameters that were optimized for (1) taper, (2) cumulative volume, (3) taper and cumulative volume, (4) taper and total volume, and (5) taper, cumulative volume, and total volume. The adjustment strategies are (1) unadjusted, and adjusted to match (2) DBH, (3) predicted total volume, (4) DBH and predicted total volume, (5) a combined estimator, and (6) DBH …

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A Method To Derive A Tree Survival Model From Any Existing Stand Survival Model, Quang V. Cao Jan 2019

A Method To Derive A Tree Survival Model From Any Existing Stand Survival Model, Quang V. Cao

Faculty Publications

This study addresses a situation in which a forest manager has been using a whole-stand model that seems to predict well for their stands and now wants to derive an individual-tree model from it to form an integrated system that can perform well at both stand and tree levels. A simple method was developed to derive tree survival models from three existing stand-level survival models. The derived tree survival models were based on the difference between the diameter of a given tree and the diameter at which tree and stand survival probabilities are equal. For stand survival prediction, each stand …

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Food-Burying Behavior In Red Imported Fire Ants (Hymenoptera: Formicidae), Wenquan Qin, Xuan Chen, Linda M. Hooper-Bùi, Jiacheng Cai, Lei Wang, Zhaohui Sun, Xiujun Wen, Cai Wang Jan 2019

Food-Burying Behavior In Red Imported Fire Ants (Hymenoptera: Formicidae), Wenquan Qin, Xuan Chen, Linda M. Hooper-Bùi, Jiacheng Cai, Lei Wang, Zhaohui Sun, Xiujun Wen, Cai Wang

Faculty Publications

The food-burying behavior has been reported in many mammals and birds, but was rarely observed in invertebrates. The red imported fire ants, Solenopsis invicta Buren, is an invasive pest in many areas of the world that usually performing food-burying during the foraging processes. However, the impacted factors and measureable patterns of this behavior is largely unknown. In the present study, food-burying vs food-transport behaviors of Solenopsis invicta were observed under laboratory and field conditions. When starved (no food was provided for 37 days) in the laboratory, food (sausage) was consumed by large numbers of ants, and few burying behaviors were …

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Radon Transforms Over Lower-Dimensional Horospheres In Real Hyperbolic Space, William O. Bray, Boris Rubin Jan 2019

Radon Transforms Over Lower-Dimensional Horospheres In Real Hyperbolic Space, William O. Bray, Boris Rubin

Faculty Publications

We study horospherical Radon transforms that integrate functions on the n-dimensional real hyperbolic space over horospheres of arbitrary fixed dimension 1 ≤ d ≤ n-1. Exact existence conditions and new explicit inversion formulas are obtained for these transforms acting on smooth functions and functions belonging to Lp. The case d = n 1 agrees with the well-known Gelfand-Graev transform.

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Domain Decomposition For Quasi-Periodic Scattering By Layered Media Via Robust Boundary-Integral Equations At All Frequencies, Carlos Pérez-Arancibia, Stephen P. Shipman, Catalin Turc, Stephanos Venakides Jan 2019

Domain Decomposition For Quasi-Periodic Scattering By Layered Media Via Robust Boundary-Integral Equations At All Frequencies, Carlos Pérez-Arancibia, Stephen P. Shipman, Catalin Turc, Stephanos Venakides

Faculty Publications

We develop a non-overlapping domain decomposition method (DDM) for scalar wave scattering by periodic layered media. Our approach relies on robust boundary-integral equation formulations of Robin-to-Robin (RtR) maps throughout the frequency spectrum, including cutoff (or Wood) frequencies. We overcome the obstacle of non-convergent quasi-periodic Green functions at these frequencies by incorporating newly introduced shifted Green functions. Using the latter in the definition of quasi-periodic boundary-integral operators leads to rigorously stable computations of RtR operators. We develop Nyström discretizations of the RtR maps that rely on trigonometric interpolation, singularity resolution, and fast convergent windowed quasi-periodic Green functions. We solve the tridiagonal …

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A Finite Element Method For A Phase Field Model Of Nematic Liquid Crystal Droplets, Amanda E. Diegel, Shawn W. Walker Jan 2019

A Finite Element Method For A Phase Field Model Of Nematic Liquid Crystal Droplets, Amanda E. Diegel, Shawn W. Walker

Faculty Publications

We develop a novel finite element method for a phase field model of nematic liquid crystal droplets. The continuous model considers a free energy comprised of three components: the Ericksen’s energy for liquid crystals, the Cahn-Hilliard energy representing the interfacial energy of the droplet, and an anisotropic weak anchoring energy that enforces a condition such that the director field is aligned perpendicular to the interface of the droplet. Applications of the model are for finding minimizers of the free energy and exploring gradient flow dynamics. We present a finite element method that utilizes a special discretization of the liquid crystal …

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Mathematical Modeling Of Frontal Polymerization, John A. Pojman Jan 2019

Mathematical Modeling Of Frontal Polymerization, John A. Pojman

Faculty Publications

© EDP Sciences, 2019 Frontal polymerization is way to convert liquid resin into a solid material with a self-propagating reaction. The reaction spreads like a flame from the heat of the reaction that diffuses into neighboring regions, starting more reaction. The frontal velocity has been accurately modeled for free-radical polymerization systems. The dynamics of fronts have been studied theoretically and experimentally. If the viscosity of the initial medium is low, then fronts can become unstable due to buoyancy-driven convection. A fascinating aspect of frontal polymerization is that fronts often do not propagate as a plane waves but exhibit complex modes …

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Kms Conditions, Standard Real Subspaces And Reflection Positivity On The Circle Group, Karl Hermann Neeb, Gestur Ólafsson Jan 2019

Kms Conditions, Standard Real Subspaces And Reflection Positivity On The Circle Group, Karl Hermann Neeb, Gestur Ólafsson

Faculty Publications

We continue our investigations of the representation theoretic side of reflection positivity by studying positive definite functions Ψ on the additive group (ℝ, +) satisfying a suitably defined KMS condition. These functions take values in the space Bil (V) of bilinear forms on a real vector space V. As in quantum statistical mechanics, the KMS condition is defined in terms of an analytic continuation of Ψ to the strip [z ∈ : 0 ≥ Imz ≥ β] with a coupling condition Ψ (iβ + t) = Ψ (t) on the boundary. Our first main result consists of a characterization of …

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An Analysis Of The Effect Of Tooth Wear On Bovid Identification, Juliet K. Brophy, Gregory J. Matthews, George K. Thiruvathukal Jan 2019

An Analysis Of The Effect Of Tooth Wear On Bovid Identification, Juliet K. Brophy, Gregory J. Matthews, George K. Thiruvathukal

Faculty Publications

Previous research provides a method for reducing the subjectivity in taxonomic identification of species in the family Bovidae by quantifying the occlusal surface of molar teeth using elliptical Fourier analysis. In this current study, we specifically test what effect medium to late tooth wear has on the identification of bovids when using the form (size and shape) of the occlusal surface to classify specimens. To achieve this, the classification results of teeth with ≥85% of their occlusal surface (training data set) were compared with the results of teeth with 87% of the time with both Alcelaphini and Reduncini classifying correctly …

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Formation Of Social Capital For Community College Students: A Second-Order Confirmatory Factor Analysis, Yu (April) Chen, Soko S. Starobin Jan 2019

Formation Of Social Capital For Community College Students: A Second-Order Confirmatory Factor Analysis, Yu (April) Chen, Soko S. Starobin

Faculty Publications

Objective: This quantitative study constructed a statistical model to measure family social capital and college social capital among community college students. The authors also examined influences of these two types of social capital constructs on degree aspiration. Method: This study utilized the STEM (Science, Technology, Engineering and Mathematics) Student Success Literacy Survey (SSSL) to collect data in all 15 community college districts in Iowa. With more than 5,000 responses, the authors conducted descriptive analysis, exploratory and confirmatory factor analysis, and structural equation modeling (SEM) analysis. Results: College social capital was measured by three latent variables such as interaction with advisors, …

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Undergraduate International Student Enrollment Forecasting Model: An Application Of Time Series Analysis, Yu April Chen, Ran Li, Linda Serra Hagedorn Jan 2019

Undergraduate International Student Enrollment Forecasting Model: An Application Of Time Series Analysis, Yu April Chen, Ran Li, Linda Serra Hagedorn

Faculty Publications

This study developed statistical models to forecast international undergraduate student enrollment at a Midwest university. The authors constructed a Seasonal Autoregressive Integrated Moving Average model with input variables to estimate future enrollment. This model reflected enrollment patterns by semester through highlighting seasonality. Further, authors added input variables such as visa policy changes, the rapid increase of Chinese undergraduate enrollment, and tuition rate into the model estimation. The visa policy change and the increase of Chinese undergraduate enrollment were significant predictors of international undergraduate enrollment. The effect of tuition rates was significant but minimal in magnitude. Findings of this study generate …

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Composition Of Gaussian Noises From Successive Convex Integrations, Amites Dasgupta Jan 2019

Composition Of Gaussian Noises From Successive Convex Integrations, Amites Dasgupta

Communications on Stochastic Analysis

No abstract provided.

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Limiting Means For Spherical Slices, Amy Peterson, Ambar Sengupta Jan 2019

Limiting Means For Spherical Slices, Amy Peterson, Ambar Sengupta

Communications on Stochastic Analysis

No abstract provided.

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Generalized Stochastic Burgers' Equation With Non-Lipschitz Diffusion Coefficient, Vivek Kumar, Ankik Kumar Giri Jan 2019

Generalized Stochastic Burgers' Equation With Non-Lipschitz Diffusion Coefficient, Vivek Kumar, Ankik Kumar Giri

Communications on Stochastic Analysis

No abstract provided.

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Non-Pt-Symmetric Two-Layer Cylindrical Waveguide For Exceptional-Point-Enhanced Optical Devices, Yin Huang, Yuecheng Shen, Georgios Veronis Jan 2019

Non-Pt-Symmetric Two-Layer Cylindrical Waveguide For Exceptional-Point-Enhanced Optical Devices, Yin Huang, Yuecheng Shen, Georgios Veronis

Faculty Publications

We investigate the exceptional points in a two-layer cylindrical waveguide structure consisting of absorbing and non-absorbing dielectrics. We show that, by tuning the core to total radius ratio and the refractive index of the core layer in such a structure, the complex effective indices of two waveguide modes can coalesce so that an exceptional point is formed. We show that the sensitivity of the effective index of the waveguide mode to variations of the refractive index of the material filling the shell layer is enhanced at the exceptional point. In addition, we show that larger sensitivity enhancement is obtained for …

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Modeling/Simulation Of The Dividing Wall Column By Using The Rigorous Model, Chi Zhai, Qinjun Liu, Jose A. Romagnoli, Wei Sun Jan 2019

Modeling/Simulation Of The Dividing Wall Column By Using The Rigorous Model, Chi Zhai, Qinjun Liu, Jose A. Romagnoli, Wei Sun

Faculty Publications

Dividing wall column (DWC) is an atypical distillation column with an internal, vertical WE partition wall that effectively accommodates two conventional distillation columns into one to improve the thermodynamic efficiency. In previous studies, different equivalent models by combining conventional columns are adopted to approximate the DWC modeling, which may not well describe the integration of the DWC; moreover, the computational cost increases when multiple columns are implemented to represent one DWC. In this paper, a rigorous mathematical model is proposed based on the mass balance, the energy and phase equilibrium of the DWC, where decision variables and state variables are …

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Three-Dimensional Analytical Poromechanical Solutions For An Arbitrarily Inclined Borehole Subjected To Fluid Injection, S. L. Chen Jan 2019

Three-Dimensional Analytical Poromechanical Solutions For An Arbitrarily Inclined Borehole Subjected To Fluid Injection, S. L. Chen

Faculty Publications

Hydraulic fracturing is the primary method of stimulation in unconventional reservoirs, playing a significant role in oil and gas production enhancement. A key issue for the analysis of hydraulic fracture initiation is to accurately determine the stress distributions in the vicinity of the borehole caused by the injection of pressurized fluids. This paper develops an exact, three-dimensional, poroelastic coupled analytical solution for such stress analysis of an arbitrarily inclined borehole subjected concurrently to a finite-length fluid discharge and in situ stresses, using Fourier expansion theorem and the Laplace–Fourier integral transform technique. The complicated boundary conditions, which involve the mixed boundary …

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Analysis Of Cylindrical Cavity Expansion In Anisotropic Critical State Soils Under Drained Conditions, K. Liu, S. L. Chen Jan 2019

Analysis Of Cylindrical Cavity Expansion In Anisotropic Critical State Soils Under Drained Conditions, K. Liu, S. L. Chen

Faculty Publications

This paper presents a semi-analytical solution for the drained cylindrical cavity expansion problem using the well-known anisotropic modified Cam clay model proposed by Dafalias in 1987. The prominent feature of this elastoplastic model, i.e., its capability to describe both the initial fabric anisotropy and stress-induced anisotropy of soils, makes the anisotropic elastoplastic solution derived herein for the cavity problem a more realistic one. Following the development by Chen and Abousleiman in 2013 of a novel solution scheme that establishes a link between the Eulerian and Lagrangian formulations of the condition of radial equilibrium, the plastic zone solution can eventually be …

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Mrt-Lattice Boltzmann Model For Multilayer Shallowwater Flow, Kevin R. Tubbs, Frank T.C. Tsai Jan 2019

Mrt-Lattice Boltzmann Model For Multilayer Shallowwater Flow, Kevin R. Tubbs, Frank T.C. Tsai

Faculty Publications

The objectives of this study are to introduce a multiple-relaxation-time (MRT) lattice Boltzmann model (LBM) to simulate multilayer shallow water flows and to introduce graphics processing unit (GPU) computing to accelerate the lattice Boltzmann model. Using multiple relaxation times in the lattice Boltzmann model has an advantage of handling very low kinematic viscosity without causing a stability problem in the shallow water equations. This study develops a multilayer MRT-LBM to solve the multilayer Saint-Venant equations to obtain horizontal flow velocities in various depths. In the multilayer MRT-LBM, vertical kinematic viscosity forcing is the key term to couple adjacent layers. We …

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