Mathematics Commons^™

Lie Symmetry To Nonlinear Oscillator Systems And Applications, Xiaoyan Li

Theses and Dissertations

In this paper, we apply the theory of Lie symmetry to study a generalized second-order nonlinear differential equation, which includes several physical nonlinear oscillators such as force-free Helmholtz oscillator, force-free Duffing and Duffing-van der Pol oscillators, modified Emden-type equation and its hierarchy etc, and investigate the dynamical properties of this rather general equation. We identify and classify several new integrable cases for arbitrary values of exponents, which determine the tangent vector as well as the infinitesimal generator. Using the Lie point symmetry, we find the useful infinitesimal generators and canonical coordinates, and obtain the first integrals of the second-order nonlinear …

On Hypergroups Of Order At Most 6, Jordy C. Lopez

Theses and Dissertations

This thesis surveys recent results on hypergroups as defined by Frédéric Marty in [3] and [4] and their relation to association schemes as presented in [5]. We show that every association scheme is a hypergroup. Then, we compile a few general results on hypergroups needed for our investigation of hypergroups with three, four and six elements. From [1] and [7], we give examples of hypergroups that do not come from finite schemes and from no scheme at all. Our main result occurs when considering hypergroups S with six elements that have a non-normal closed subset T of order 2 with …

Harmonic Maps Surfaces And Relativistic Strings, Paul Bracken

School of Mathematical & Statistical Sciences Faculty Publications

The harmonic map is introduced and several physical applications are presented. The classical nonlinear σ model can be looked at as the embedding of a two-dimensional surface in a threedimensional sphere, which is itself embedded in a four-dimensional space. A system of nonlinear evolution equations are obtained by working out the zero curvature condition for the Gauss equations relevant to this geometric formulation.

Multicollinearity In Regression Analyses Conducted In Epidemiologic Studies, Kristina Vatcheva, Minjae Lee, Joseph B. Mccormick, Mohammad H. Rahbar

School of Mathematical & Statistical Sciences Faculty Publications

The adverse impact of ignoring multicollinearity on findings and data interpretation in regression analysis is very well documented in the statistical literature. The failure to identify and report multicollinearity could result in misleading interpretations of the results. A review of epidemiological literature in PubMed from January 2004 to December 2013, illustrated the need for a greater attention to identifying and minimizing the effect of multicollinearity in analysis of data from epidemiologic studies. We used simulated datasets and real life data from the Cameron County Hispanic Cohort to demonstrate the adverse effects of multicollinearity in the regression analysis and encourage researchers …

Cirrhosis And Advanced Fibrosis In Hispanics In Texas: The Dominant Contribution Of Central Obesity, Jingjing Jiao, Gordon P. Watt, Minjae Lee, Mohammad H. Rahbar, Kristina Vatcheva, Jen-Jung Pan, Joseph B. Mccormick, Susan P. Fisher-Hoch, Michael Fallon, Laura Beretta

School of Mathematical & Statistical Sciences Faculty Publications

Liver cirrhosis is a leading cause of death in Hispanics and Hispanics who live in South Texas have the highest incidence of liver cancer in the United States. We aimed at determining the prevalence and associated risk factors of cirrhosis in this population. Clinical and demographic variables were extracted for 2466 participants in the community-based Cameron County Hispanic Cohort in South Texas. Aspartate transaminase to Platelet Ratio Index (APRI) was used to predict cirrhosis in Cameron County Hispanic Cohort. The prevalence of cirrhosis using APRI≥2 was 0.94%, which is nearly 4-fold higher than the national prevalence. Using APRI≥1, the overall …

Liver And Other Gastrointestinal Cancers Are Frequent In Mexican Americans, Ariana L. Garza, Kristina Vatcheva, Jen-Jung Pan, Mohammad H. Rahbar, Michael Fallon, Joseph B. Mccormick, Susan P. Fisher-Hoch

School of Mathematical & Statistical Sciences Faculty Publications

Background

Disease patterns in Mexican-American health-disparity populations differ from larger United States populations.

Aims

Determine frequency of gastrointestinal cancers in Mexican Americans.

Methods

We analyzed self-reported data from the Cameron County Hispanic Cohort where we find high rates of risk factors for cancer: obesity (48.5%), diabetes (30.7%). Participants provided cancer histories about themselves and first and second degree relatives. Logistic regression models assessed risk factors. Frequencies of cancer sites were ranked and validated using concurrent age local cancer registry data.

Results

Among 9,249 individuals (participants and their relatives) there were 1,184 individuals with reports of cancer. Among cohort participants under …

Depression In Mexican Americans With Diagnosed And Undiagnosed Diabetes, Rene L. Olvera, Susan P. Fisher-Hoch, Douglas E. Williamson, Kristina Vatcheva, Joseph B. Mccormick

School of Mathematical & Statistical Sciences Faculty Publications

Background: Depression and diabetes commonly co-occur; however, the strength of the physiological effects of diabetes as mediating factors towards depression is uncertain.

Method: We analyzed extensive clinical, epidemiological and laboratory data from n = 2081 Mexican Americans aged 35-64 years, recruited from the community as part of the Cameron County Hispanic Cohort (CCHC) divided into three groups: Diagnosed (self-reported) diabetes (DD, n = 335), Undiagnosed diabetes (UD, n = 227) and No diabetes (ND, n = 1519). UD participants denied being diagnosed with diabetes, but on testing met the 2010 American Diabetes Association and World Health Organization definitions of diabetes. …

Knowledge For Equitable Mathematics Teaching: The Case Of Latino Ells In U.S. Schools, Aaron T. Wilson

School of Mathematical & Statistical Sciences Faculty Publications

This paper reports the exploration of an aspect of knowledge needed for equitable mathematics teaching. Pedagogical Content Knowledge for Teaching Mathematics to English Language Learners (PCK-MELL) was proposed as a theoretical knowledge construct, a subdomain of MKT, and the construct was investigated through a process of survey instrument development and administration. The survey contained items intended to measure teachers’ knowledge of the obstacles encountered by ELLs in math classes, of the resources that ELLs draw upon, and of instructional strategies for teaching ELLs. Analysis of middle school mathematics teachers’ responses (N = 42) offered insights into how to improve the …

Metabolic Health Has Greater Impact On Diabetes Than Simple Overweight/Obesity In Mexican Americans, Shenghui Wu, Susan P. Fisher-Hoch, Belinda M. Reininger, Kristina Vatcheva, Joseph B. Mccormick

School of Mathematical & Statistical Sciences Faculty Publications

To compare the risk for diabetes in each of 4 categories of metabolic health and BMI. Methods. Participants were drawn from the Cameron County Hispanic Cohort, a randomly selected Mexican American cohort in Texas on the US-Mexico border. Subjects were divided into 4 phenotypes according to metabolic health and BMI: metabolically healthy normal weight, metabolically healthy overweight/obese, metabolically unhealthy normal weight, and metabolically unhealthy overweight/obese. Metabolic health was defined as having less than 2 metabolic abnormalities. Overweight/obese status was assessed by BMI higher than 25 kg/m2. Diabetes was defined by the 2010 ADA definition or by being on a diabetic …

A Polyhedral Model Of Partitions With Bounded Differences And A Bijective Proof Of A Theorem Of Andrews, Beck, And Robbins, Felix Breuer, Brandt Kronholm

School of Mathematical & Statistical Sciences Faculty Publications

The smallest part is a rational function. This result is similar to the closely related case of partitions with fixed differences between largest and smallest parts which has recently been studied through analytic methods by Andrews, Beck, and Robbins. Our approach is geometric: We model partitions with bounded differences as lattice points in an infinite union of polyhedral cones. Surprisingly, this infinite union tiles a single simplicial cone. This construction then leads to a bijection that can be interpreted on a purely combinatorial level.

An Application Of The Spectral Theorem To The Laplacian On A Riemannian Manifold, Paul Bracken

School of Mathematical & Statistical Sciences Faculty Publications

There continues to be great interest in the study of the heat equation on Riemannian manifolds. This may be due to the remarkable more recent work of Patodi [1]. It may also be due in part to the asymptotic expansion of Minakshisundaram and Pleijel. The heat equation involves a parabolic partial differential equation that describes the distribution of heat in a given region over time. This equation has also appears in probability theory to describe random walks. The heat equation is also of importance in Riemannian geometry, topology and applied mathematics.

Asymptotic And Optimal Liouville Properties For Wolff Type Integral Systems, John Villavert

School of Mathematical & Statistical Sciences Faculty Publications

This article examines the properties of positive solutions to fully nonlinear systems of integral equations involving Hardy and Wolff potentials. The first part of the paper establishes an optimal existence result and a Liouville type theorem for the integral systems. Then, the second part examines the decay rates of positive bound states at infinity. In particular, a complete characterization of the asymptotic properties of bounded and decaying solutions is given by showing that such solutions vanish at infinity with two principle rates: the slow decay rates and the fast decay rates. In fact, the two rates can be fully distinguished …

Stability Analysis And Hopf Bifurcation Of Density-Dependent Predator-Prey Systems With Beddington-Deangelis Functional Response, Xin Jiang, Zhikun She, Zhaosheng Feng

School of Mathematical & Statistical Sciences Faculty Publications

In this article, we study a density-dependent predator-prey system with the Beddington-DeAngelis functional response for stability and Hopf bifurcation under certain parametric conditions. We start with the condition of the existence of the unique positive equilibrium, and provide two sufficient conditions for its local stability by the Lyapunov function method and the Routh-Hurwitz criterion, respectively. Then, we establish sufficient conditions for the global stability of the positive equilibrium by proving the non-existence of closed orbits in the first quadrant R²+. Afterwards, we analyze the Hopf bifurcation geometrically by exploring the monotonic property of the trace of the Jacobean matrix with …

The Effect Of Ignoring Statistical Interactions In Regression Analyses Conducted In Epidemiologic Studies: An Example With Survival Analysis Using Cox Proportional Hazards Regression Model, Kristina Vatcheva, Joseph B. Mccormick, Mohammad H. Rahbar

School of Mathematical & Statistical Sciences Faculty Publications

Objective: To demonstrate the adverse impact of ignoring statistical interactions in regression models used in epidemiologic studies.

Study design and setting: Based on different scenarios that involved known values for coefficient of the interaction term in Cox regression models we generated 1000 samples of size 600 each. The simulated samples and a real life data set from the Cameron County Hispanic Cohort were used to evaluate the effect of ignoring statistical interactions in these models.

Results: Compared to correctly specified Cox regression models with interaction terms, misspecified models without interaction terms resulted in up to 8.95 fold bias in estimated …

The Complete Classification Of Five-Dimensional Dirichlet–Voronoi Polyhedra Of Translational Lattices, Mathieu Dutour Sikiric, Alexey Garber, Achill Schürmann, Clara Waldmann

School of Mathematical & Statistical Sciences Faculty Publications

This paper reports on the full classification of Dirichlet–Voronoi polyhedra and Delaunay subdivisions of five-dimensional translational lattices. A complete list is obtained of 110 244 affine types (L-types) of Delaunay subdivisions and it turns out that they are all combinatorially inequivalent, giving the same number of combinatorial types of Dirichlet–Voronoi polyhedra. Using a refinement of corresponding secondary cones, 181 394 contraction types are obtained. The paper gives details of the computer-assisted enumeration, which was verified by three independent implementations and a topological mass formula check.

Hepatitis C Virus In Mexican Americans: A Population-Based Study Reveals Relatively High Prevalence And Negative Association With Diabetes, Gordon P. Watt, Kristina Vatcheva, Laura Beretta, Jen-Jung Pan, Michael Fallon, Joseph B. Mccormick, Susan P. Fisher-Hoch

School of Mathematical & Statistical Sciences Faculty Publications

This study aimed to estimate the prevalence and risk factors for hepatitis C virus (HCV) infection in Mexican Americans living in South Texas. We tested plasma for the presence of HCV antibody from the Cameron County Hispanic Cohort (CCHC), a randomized, population-based cohort in an economically disadvantaged Mexican American community on the United States/Mexico border with high rates of chronic disease. A weighted prevalence of HCV antibody of 2·3% [n = 1131, 95% confidence interval (CI) 1·2-3·4] was found. Participants with diabetes had low rates of HCV antibody (0·4%, 95% CI 0·0-0·9) and logistic regression revealed a statistically significant negative …

Quantization Coefficients In Infinite Systems, Eugen Mihailescu, Mrinal Kanti Roychowdhury

School of Mathematical & Statistical Sciences Faculty Publications

We investigate quantization coefficients for probability measures μ on limit sets, which are generated by systems S of infinitely many contractive similarities and by probabilistic vectors. The theory of quantization coefficients for infinite systems has significant differences from the finite case. One of these differences is the lack of finite maximal antichains, and another is the fact that the set of contraction ratios has zero infimum; another difference resides in the specific geometry of S and of its noncompact limit set J . We prove that, for each r ∈ ( 0 , ∞ ) , there exists a unique …

The Bourbaki-Jacobson Correspondence, Jose R. Vera

Theses and Dissertations

A general ring theoretic correspondence between subrings of the endomorphism ring of the additive group of a commutative field will be established. This correspondence (called Bourbaki-Jacobson Correspondence) provides the ordinary Galois correspondence when applied to specific group rings. Throughout this thesis, we will work with finite dimensional field extensions.

Use Of Cubic B-Spline In Approximating Solutions Of Boundary Value Problems, Maria Mungia, Dambaru Bhatta

School of Mathematical & Statistical Sciences Faculty Publications

Here we investigate the use of cubic B-spline functions in solving boundary value problems. First, we derive the linear, quadratic, and cubic B-spline functions. Then we use the cubic B-spline functions to solve second order linear boundary value problems. We consider constant coefficient and variable coefficient cases with non-homogeneous boundary conditions for ordinary differential equations. We also use this numerical method for the space variable to obtain solutions for second order linear partial differential equations. Numerical results for various cases are presented and compared with exact solutions.

Depression, Obesity, And Metabolic Syndrome: Prevalence And Risks Of Comorbidity In A Population-Based Study Of Mexican Americans, Rene L. Olvera, Douglas E. Williamson, Susan P. Fisher-Hoch, Kristina Vatcheva, Joseph B. Mccormick

School of Mathematical & Statistical Sciences Faculty Publications

Introduction: We examined the prevalence of depression, obesity, and metabolic syndrome and associations between them in a population-based representative cohort of Mexican Americans living on the United States-Mexico border.

Method: The sample in this cross-sectional analysis consisted of 1,768 Mexican American adults (≥ 18 years of age) assessed between the years 2004 and 2010, with whom we tested our central hypothesis of a significant relationship between obesity and depression. Depression was measured using the Center for Epidemiologic Studies-Depression scale (CES-D) with a cutoff score of ≥ 16 for depression and a cutoff score of ≥ 27 for severe depression. We …

Barriers To Disaster Preparedness Among Medical Special Needs Populations, Leslie Meyer, Kristina Vatcheva, Stephanie Castellanos, Belinda M. Reininger

School of Mathematical & Statistical Sciences Faculty Publications

A medical special needs (MSN) assessment was conducted among 3088 respondents in a hurricane prone area. The sample was female (51.7%), Hispanic (92.9%), aged >45 years (51%), not insured for health (59.2%), and with an MSN (33.2%). Barriers to preparedness were characterized for all households, including those with inhabitants reporting MSN ranging from level 0 (mild) to level 4 (most severe). Multivariable logistic regression tested associations between hurricane preparedness and barriers to evacuation by level of MSN. A significant interaction effect between number of evacuation barriers and MSN was found. Among households that reported individuals with level 0 MSN, the …

Association Of Total And Differential White Blood Cell Counts To Development Of Type 2 Diabetes In Mexican Americans In Cameron County Hispanic Cohort, Kristina Vatcheva, Susan P. Fisher-Hoch, Mohammad H. Rahbar, Minjae Lee, Rene L. Olvera, Joseph B. Mccormick

School of Mathematical & Statistical Sciences Faculty Publications

Objective: To evaluate the relationship between total and differential White Blood Cell (WBC) counts with time to transition to type 2 diabetes in Mexican Americans using prospective data from the Cameron County Hispanic Cohort (CCHC).

Results: Multivariable Cox proportional hazards regression models revealed that obese Mexican-American cohort participants whose total WBC or granulocyte count increased over time had 1.39 and 1.35 times higher risk respectively of transition to type 2 diabetes when compared to overweight participants. The granulocyte or total WBC count in participants with BMI≥35 were significant risk factors for transition to type 2 diabetes.

Conclusions: Increased total WBC …

Completion Of Hankel Partial Contractions Of Non-Extremal Type, In Hyoun Kim, Seonguk Yoo, Jasang Yoon

School of Mathematical & Statistical Sciences Faculty Publications

A matrix completion problem has been exploited amply because of its abundant applications and the analysis of contractions enables us to have insight into structure and space of operators. In this article, we focus on a specific completion problem related to Hankel partial contractions. We provide concrete necessary and sufficient conditions for the existence of completion of Hankel partial contractions for both extremal and non-extremal types with lower dimensional matrices. Moreover, we give a negative answer for the conjecture presented in [8]. For our results, we use several tools such as the Nested Determinants Test (or Choleski's Algorithm), the Moore-Penrose …

Higgs Boson Equation In De Sitter Spacetime: Numerical Investigation Of Bubbles Using Gpus, Jacob N. Banda

Theses and Dissertations - UTB/UTPA

The Higgs field, along with its corresponding boson, represent a milestone for modern day particle physics. In this work we consider the Higgs boson equation in de Sitter spacetime. Previous work by K. Yagdjian [23] has formulated sufficient conditions for the existence of the zeros of global solutions in the interior of their supports. In searching for such solutions, we turn to heterogeneous parallel computing, which allows for faster computation through graphical processing units (GPUs). Armed with general-purpose computation on graphics hardware (GPGPU) techniques and explicit numerical schemes, we approximate solutions of the equation for the Higgs boson along with …

On Various Solutions To A (2+1) Dimensional General Camassa-Holm Equation, Eric J. Tovar

Theses and Dissertations - UTB/UTPA

We study a (2+1)-dimensional generalized Camassa-Holm (2dgCH) equation with both quadratic and cubic nonlinearity. We derive a peaked soliton (peakon) solution and multi-peakon solutions. In particular, the two-peakon dynamical system is explicitly presented and their collisions are investigated in detail. We also find weak kink and kink-peakon interactional solutions. Furthermore, we study all possible smooth one-soliton solutions for the system.

Financial Market And Pricing Of Emerging Financial Derivatives: A Mathematical Approach, Haicheng Gu

Theses and Dissertations - UTB/UTPA

Pricing has been one of the key problems of financial market theory. With the development of the modern financial market, various new financial derivatives have been created and need to be priced properly. In the thesis, we are going to use several mathematical tools to investigate the essential structure of the financial market and models for financial derivatives.

Zeros Of Cubic Eisenstein Series, Sahak D. Sandragorsian

Theses and Dissertations - UTB/UTPA

This thesis provides a detailed exposition and extension of the work of F. K. C. Rankin and Swinnerton-Dyer on the location of the zeros of Eisenstein series for SL(2,Z). Exact values of the zeros in special cases will be given in terms of modular functions. Analogous new results on zeros of cubic Eisenstein series will be presented.

Undiagnosed Diabetes And Pre-Diabetes In Health Disparities, Susan P. Fisher-Hoch, Kristina Vatcheva, Mohammad H. Rahbar, Joseph B. Mccormick

School of Mathematical & Statistical Sciences Faculty Publications

Globally half of all diabetes mellitus is undiagnosed. We sought to determine the extent and characteristics of undiagnosed type 2 diabetes mellitus and pre-diabetes in Mexican Americans residing in the United States. This disadvantaged population with 50% lifetime risk of diabetes is a microcosm of the current pandemic. We accessed baseline data between 2004 and 2014 from 2,838 adults recruited to our Cameron County Hispanic Cohort (CCHC); a two-stage randomly selected 'Framingham-like' cohort of Mexican Americans on the US Mexico border with severe health disparities. We examined prevalence, risk factors and metabolic health in diagnosed and undiagnosed diabetes and pre-diabetes. …

Approximate Analysis Solution Of Burgers-Kdv Equation, Hani Aldirawi

Theses and Dissertations - UTB/UTPA

In this thesis, we study the Two-Dimensional Burgers-Kortewege-de Vries(2D-BKdV) equation by analyzing the equivalent Abel equation, which indicates that under some particular conditions, the 2D-BKdV equation has a unique bounded traveling wave solution. By using the theorem of contractive mapping, a traveling wave solution to the 2D-BKdV equation is expressed explicitly.

A Study On Hispanic College Students' Mathematics Anxiety, Study Habits, And Academic Performances On Mathematics, Luis M. Fernandez

Theses and Dissertations - UTB/UTPA

Mathematics anxiety has been described as a feeling of apprehension, fear, tension, and discomfort when confronted with mathematics. Mathematics anxiety has also been shown to interfere with mathematics performance; therefore, for our research we investigated what portions of individuals seem to suffer higher levels of mathematics anxiety and to what extent they are affected by it. We also investigated the study habits of the students and how these affect their mathematics anxiety levels and overall mathematics performance. Our data was obtained from Hispanic undergraduate students (n=405) who took Elementary Algebra (Math 1300), Intermediate Algebra (Math 1334), College Algebra (Math 1340) …