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Articles 451 - 480 of 698

Full-Text Articles in Physical Sciences and Mathematics

Shining A Light On A Hidden Figure: Dorothy Hoover, Lily S. Khadjavi Jan 2020

Shining A Light On A Hidden Figure: Dorothy Hoover, Lily S. Khadjavi

Mathematics Faculty Works

No abstract provided.

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A Linear Optimal Feedback Control For Producing 1,3-Propanediol Via Microbial Fermentation, Yangping Ma Jan 2020

A Linear Optimal Feedback Control For Producing 1,3-Propanediol Via Microbial Fermentation, Yangping Ma

Mathematics Faculty Works

In this paper, we consider a multistage feedback control strategy for the production of 1,3-propanediol(1,3-PD) in microbial fermentation. The feedback control strategy is widely used in industry, and to the best of our knowledge, this is the first time it is applied to 1,3-PD. The feedback control law is assumed to be linear of the concentrations of biomass and glycerol, and the coefficients in the controller are continuous. A multistage feedback control law is obtained by using the control parameterization method on the coefficient functions. Then, the optimal control problem can be transformed into an optimal parameter selection problem. The …

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Graphs Admitting Only Constant Splines, Alissa Crans, Blake Mellor Jan 2020

Graphs Admitting Only Constant Splines, Alissa Crans, Blake Mellor

Mathematics Faculty Works

We study generalized graph splines, introduced by Gilbert, Tymoczko, and Viel (2016). For a large class of rings, we characterize the graphs that only admit constant splines. To do this, we prove that if a graph has a particular type of cutset (e.g., a bridge), then the space of splines naturally decomposes as a certain direct sum of submodules. As an application, we use these results to describe splines on a triangulation studied by Zhou and Lai, but over a different ring than they used.

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Gardening Resources, Center For Urban Resilience Mar 2019

Gardening Resources, Center For Urban Resilience

Module 10: Garden Ecology

No abstract provided.

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Birds In The Urban Landscape, Center For Urban Resilience Jan 2019

Birds In The Urban Landscape, Center For Urban Resilience

Module 10: Garden Ecology

No abstract provided.

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Finite N-Quandles Of Torus And Two-Bridge Links, Alissa Crans, Blake Mellor, Patrick Shanahan Jan 2019

Finite N-Quandles Of Torus And Two-Bridge Links, Alissa Crans, Blake Mellor, Patrick Shanahan

Mathematics Faculty Works

We compute Cayley graphs and automorphism groups for all finite n-quandles of two-bridge and torus knots and links, as well as torus links with an axis.

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An Enumeration Process For Racks, Patrick Shanahan Jan 2019

An Enumeration Process For Racks, Patrick Shanahan

Mathematics Faculty Works

Given a presentation for a rack , we define a process which systematically enumerates the elements of . The process is modeled on the systematic enumeration of cosets first given by Todd and Coxeter. This generalizes and improves the diagramming method for -quandles introduced by Winker. We provide pseudocode that is similar to that given by Holt, Eick, and O'Brien for the Todd-Coxeter process. We prove that the process terminates if and only if is finite, in which case, the procedure outputs an operation table for the finite rack. We conclude with an application to knot theory

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Thermostability And Excision Activity Of Polymorphic Forms Of Hogg1, Kathryn Mouzakis Jan 2019

Thermostability And Excision Activity Of Polymorphic Forms Of Hogg1, Kathryn Mouzakis

Chemistry and Biochemistry Faculty Works

Objectives: Reactive oxygen species (ROS) oxidize guanine residues in DNA to form 7,8-dihydro-oxo-2′-deoxyguanosine (8oxoG) lesions in the genome. Human 8-oxoguanine glycosylase-1 (hOGG1) recognizes and excises this highly mutagenic species when it is base-paired opposite a cytosine. We sought to characterize biochemically several hOGG1 variants that have been found in cancer tissues and cell lines, reasoning that if these variants have reduced repair capabilities, they could lead to an increased chance of mutagenesis and carcinogenesis. Results: We have over-expressed and purified the R46Q, A85S, R154H, and S232T hOGG1 variants and have investigated their repair efficiency and thermostability. The hOGG1 variants showed …

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Green Chemistry In United States Science Policy, Emily Jarvis Jan 2019

Green Chemistry In United States Science Policy, Emily Jarvis

Chemistry and Biochemistry Faculty Works

Although optimizing each of the Twelve Principles of Green Chemistry is necessary for achieving the greenest possible chemistry in the lab, there are additional creative ways to promote green chemistry not encompassed by these. Communicating to society the importance of green chemistry beyond the laboratory is essential. Of course, doing this effectively presents distinct challenges to those encountered when designing chemical syntheses. Here, I discuss several observations from my time working in federal science policy as an American Association for the Advancement of Science/American Chemical Society Congressional Science Fellow in the United States Senate. I suggest a practical science policy …

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Remarks On Suzuki's Epimorphism Number, Patrick Shanahan Jan 2019

Remarks On Suzuki's Epimorphism Number, Patrick Shanahan

Mathematics Faculty Works

A partial order on prime knots can be defined by declaring 𝐽≥𝐾, if there exists an epimorphism from the knot group of 𝐽 onto the knot group of 𝐾. Suppose that 𝐽 is a 2-bridge knot that is strictly greater than 𝑚 distinct, nontrivial knots. In this paper, we determine a lower bound on the crossing number of 𝐽 in terms of 𝑚. Using this bound, we answer a question of Suzuki regarding the 2-bridge epimorphism number EK(𝑛) which is the maximum number of nontrivial knots which are strictly smaller than some 2-bridge knot with crossing number 𝑛. We establish …

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The Origins Of Spectra, An Organization For Lgbt Mathematicians, Lily S. Khadjavi Jan 2019

The Origins Of Spectra, An Organization For Lgbt Mathematicians, Lily S. Khadjavi

Mathematics Faculty Works

No abstract provided.

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On The Structure Of Hom Quandles, Alissa Crans Jan 2019

On The Structure Of Hom Quandles, Alissa Crans

Mathematics Faculty Works

We continue the study of the quandle of homomorphisms into a medial quandle begun in [2]. We show that it suffices to consider only medial source quandles, and therefore the structure theorem of [11] provides a characterization of the Hom quandle. In the particular case when the target is 2-reductive this characterization takes on a simple form that makes it easy to count and determine the structure of the Hom quandle

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Native Gardens In Southern California, Center For Urban Resilience Jan 2018

Native Gardens In Southern California, Center For Urban Resilience

Module 10: Garden Ecology

No abstract provided.

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Stochastic Maximum Principle For Partial Information Optimal Investment And Dividend Problem Of An Insurer, Yanping Ma Jan 2018

Stochastic Maximum Principle For Partial Information Optimal Investment And Dividend Problem Of An Insurer, Yanping Ma

Mathematics Faculty Works

We study an optimal investment and dividend problem of an insurer, where the aggregate insurance claims process is modeled by a pure jump Lévy process. We allow the management of the dividend payment policy and the investment of surplus in a continuous-time financial market, which is composed of a risk free asset and a risky asset. The information available to the insurer is partial information. We generalize this problem as a partial information regular-singular stochastic control problem, where the control variable consists of regular control and singular control. Then maximum principles are established to give sufficient and necessary optimality conditions …

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The Multilinear Structure Of Relu Networks, Thomas Laurent Jan 2018

The Multilinear Structure Of Relu Networks, Thomas Laurent

Mathematics Faculty Works

We study the loss surface of neural networks equipped with a hinge loss criterion and ReLU or leaky ReLU nonlinearities. Any such network defines a piecewise multilinear form in parameter space. By appealing to harmonic analysis we show that all local minima of such network are non-differentiable, except for those minima that occur in a region of parameter space where the loss surface is perfectly flat. Non-differentiable minima are therefore not technicalities or pathologies; they are heart of the problem when investigating the loss of ReLU networks. As a consequence, we must employ techniques from nonsmooth analysis to study these …

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Deep Linear Networks With Arbitrary Loss: All Local Minima Are Global, Thomas Laurent Jan 2018

Deep Linear Networks With Arbitrary Loss: All Local Minima Are Global, Thomas Laurent

Mathematics Faculty Works

We consider deep linear networks with arbitrary convex differentiable loss. We provide a short and elementary proof of the fact that all local minima are global minima if the hidden layers are either 1) at least as wide as the input layer, or 2) at least as wide as the output layer. This result is the strongest possible in the following sense: If the loss is convex and Lipschitz but not differentiable then deep linear networks can have sub-optimal local minima.

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Facilitators And Outcomes Of Stem-Education Groups Working Toward Disciplinary Integration, Anna E. Bargagliotti Jan 2018

Facilitators And Outcomes Of Stem-Education Groups Working Toward Disciplinary Integration, Anna E. Bargagliotti

Mathematics Faculty Works

There is a growing societal recognition of the need for transdisciplinary scholarly collaboration which can enhance undergraduate physics, science, and engineering education. A regional conference/network with 100 university education researchers in physics and other STEM fields was formed to address three themes (problemsolving, computational thinking, and equity) with multiple goals including to strive for transdisciplinary publications. As part of an ongoing participant observation study, phone interviews were conducted 3-4 months later. One year later, publications that were completed as a result of the conference were analyzed for their disciplinary integration. The papers showed evidence of interdispliciplanry collaboration but transdiciplinary collaboration …

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Beyond The Point Charge: Equipotential Surfaces And Electric Fields Of Various Charge Configurations, Jeffrey A. Phillips, Jeff Sanny, David Berube, Anatol Hoemke Jan 2017

Beyond The Point Charge: Equipotential Surfaces And Electric Fields Of Various Charge Configurations, Jeffrey A. Phillips, Jeff Sanny, David Berube, Anatol Hoemke

Physics Faculty Works

A laboratory experiment often performed in an introductory electricity and magnetism course involves the mapping of equipotential lines on a conductive sheet between two objects at different potentials. In this article, we describe how we have expanded this experiment so that it can be used to illustrate the electrostatic properties of conductors. Different configurations of electrodes can be used to show that the electric field is zero inside a conductor as well as within a cavity, the electric field is perpendicular to conducting surfaces, and the charge distribution on conducting surfaces can vary.

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Applications Of Fractional Calculus To Newtonian Mechanics, Gabriele U. Varieschi Jan 2017

Applications Of Fractional Calculus To Newtonian Mechanics, Gabriele U. Varieschi

Physics Faculty Works

We investigate some basic applications of Fractional Calculus (FC) to Newtonian mechanics. After a brief review of FC, we consider a possible generalization of Newton's second law of motion and apply it to the case of a body subject to a constant force. In our second application of FC to Newtonian gravity, we consider a generalized fractional gravitational potential and derive the related circular orbital velocities. This analysis might be used as a tool to model galactic rotation curves, in view of the dark matter problem. Both applications have a pedagogical value in connecting fractional calculus to standard mechanics and …

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The Stress Granule Transcriptome Reveals Principles Of Mrna Accumulation In Stress Granules, Sarah F. Mitchell Jan 2017

The Stress Granule Transcriptome Reveals Principles Of Mrna Accumulation In Stress Granules, Sarah F. Mitchell

Chemistry and Biochemistry Faculty Works

Stress granules are mRNA-protein assemblies formed from nontranslating mRNAs. Stress granules are important in the stress response and may contribute to some degenerative diseases. Here, we describe the stress granule transcriptome of yeast and mammalian cells through RNA-sequencing (RNA-seq) analysis of purified stress granule cores and single-molecule fluorescence in situ hybridization (smFISH) validation. While essentially every mRNA, and some noncoding RNAs (ncRNAs), can be targeted to stress granules, the targeting efficiency varies from <1% to >95%. mRNA accumulation in stress granules correlates with longer coding and UTR regions and poor translatability. Quantifying the RNA-seq analysis by smFISH reveals that only 10% of …

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An Analysis Of Secondary Teachers' Reasoning With Participatory Sensing Data, Anna E. Bargagliotti Jan 2017

An Analysis Of Secondary Teachers' Reasoning With Participatory Sensing Data, Anna E. Bargagliotti

Mathematics Faculty Works

"Participatory sensing is a data collection method in which communities of people collect and share data to investigate large-scale processes. These data have many features often associated with the big data paradigm: they are rich and multivariate, include non-numeric data, and are collected as determined by an algorithm rather than by traditional experimental designs. While not often found in classrooms, arguably they should be since data with these features are commonly encountered in daily life. Because of this, it is of interest to examine how teachers reason with and about such data. We propose methods for describing progress through a …

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Deadly Heat Waves Projected In The Densely Populated Agricultural Regions Of South Asia, Eun-Soon Im, Jeremy S. Pal, Elfatih A. B. Eltahir Jan 2017

Deadly Heat Waves Projected In The Densely Populated Agricultural Regions Of South Asia, Eun-Soon Im, Jeremy S. Pal, Elfatih A. B. Eltahir

Civil and Environmental Engineering Faculty Works

The risk associated with any climate change impact reflects intensity of natural hazard and level of human vulnerability. Previous work has shown that a wet-bulb temperature of 35°C can be considered an upper limit on human survivability. On the basis of an ensemble of high-resolution climate change simulations, we project that extremes of wet-bulb temperature in South Asia are likely to approach and, in a few locations, exceed this critical threshold by the late 21st century under the business-as-usual scenario of future greenhouse gas emissions. The most intense hazard from extreme future heat waves is concentrated around densely populated agricultural …

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Optimization And Control Of Agent-Based Models In Biology: A Perspective, G. An, B. G. Fitzpatrick, S. Christley, P. Federico, A. Kanarek, R. Miller Neilan, M. Oremland, R. Salinas, R. Laubeanbacher, S. Lenhart Jan 2017

Optimization And Control Of Agent-Based Models In Biology: A Perspective, G. An, B. G. Fitzpatrick, S. Christley, P. Federico, A. Kanarek, R. Miller Neilan, M. Oremland, R. Salinas, R. Laubeanbacher, S. Lenhart

Mathematics Faculty Works

Agent-based models (ABMs) have become an increasingly important mode of inquiry for the life sciences. They are particularly valuable for systems that are not understood well enough to build an equation-based model. These advantages, however, are counterbalanced by the difficulty of analyzing and using ABMs, due to the lack of the type of mathematical tools available for more traditional models, which leaves simulation as the primary approach. As models become large, simulation becomes challenging. This paper proposes a novel approach to two mathematical aspects of ABMs, optimization and control, and it presents a few first steps outlining how one might …

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On Homology Of Associative Shelves, Alissa Crans Jan 2017

On Homology Of Associative Shelves, Alissa Crans

Mathematics Faculty Works

Homology theories for associative algebraic structures are well established and have been studied for a long time. More recently, homology theories for selfdistributive algebraic structures motivated by knot theory, such as quandles and their relatives, have been developed and investigated. In this paper, we study associative self-distributive algebraic structures and their one-term and two-term (rack) homology groups.

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The Alexander Polynominal For Virtual Twist Knots, Isaac Benioff, Blake Mellor Jan 2017

The Alexander Polynominal For Virtual Twist Knots, Isaac Benioff, Blake Mellor

Mathematics Faculty Works

We define a family of virtual knots generalizing the classical twist knots. We develop a recursive formula for the Alexander polynomial Δ0 (as defined by Silver and Williams [Polynomial invariants of virtual links, J. Knot Theory Ramifications12 (2003) 987–1000]) of these virtual twist knots. These results are applied to provide evidence for a conjecture that the odd writhe of a virtual knot can be obtained from Δ0 .

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Grnsight: A Web Application And Service For Visualizing Models Of Small- To Medium-Scale Gene Regulatory Networks, Kam D. Dahlquist, John David N. Dionisio, Ben G. Fitzpatrick, Nicole A. Anguiano, Anindita Varshneya, Britain J. Southwick, Mihir Samdarshi Sep 2016

Grnsight: A Web Application And Service For Visualizing Models Of Small- To Medium-Scale Gene Regulatory Networks, Kam D. Dahlquist, John David N. Dionisio, Ben G. Fitzpatrick, Nicole A. Anguiano, Anindita Varshneya, Britain J. Southwick, Mihir Samdarshi

Biology Faculty Works

GRNsight is a web application and service for visualizing models of gene regulatory networks (GRNs). A gene regulatory network (GRN) consists of genes, transcription factors, and the regulatory connections between them which govern the level of expression of mRNA and protein from genes. The original motivation came from our efforts to perform parameter estimation and forward simulation of the dynamics of a differential equations model of a small GRN with 21 nodes and 31 edges. We wanted a quick and easy way to visualize the weight parameters from the model which represent the direction and magnitude of the influence of …

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Topological Symmetry Groups Of Complete Bipartite Graphs, Kathleen Hake, Blake Mellor, Matthew Pittluck Jun 2016

Topological Symmetry Groups Of Complete Bipartite Graphs, Kathleen Hake, Blake Mellor, Matthew Pittluck

Mathematics Faculty Works

The symmetries of complex molecular structures can be modeled by the {\em topological symmetry group} of the underlying embedded graph. It is therefore important to understand which topological symmetry groups can be realized by particular abstract graphs. This question has been answered for complete graphs [7]; it is natural next to consider complete bipartite graphs. In previous work we classified the complete bipartite graphs that can realize topological symmetry groups isomorphic to A4 , S4 or A5 [12]; in this paper we determine which complete bipartite graphs have an embedding in S 3 whose topological symmetry group …

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Wormhole Geometries In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi, Kellie L. Ault May 2016

Wormhole Geometries In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi, Kellie L. Ault

Physics Faculty Works

We present an analysis of the classic wormhole geometries based on conformal Weyl gravity, rather than standard general relativity. The main characteristics of the resulting traversable wormholes remain the same as in the seminal study by Morris and Thorne, namely, that effective super-luminal motion is a viable consequence of the metric. Improving on previous work on the subject, we show that for particular choices of the shape and redshift functions the wormhole metric in the context of conformal gravity does not violate the main energy conditions at or near the wormhole throat. Some exotic matter might still be needed at …

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Black Hole Shadows In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi, Jonas Mureika Jan 2016

Black Hole Shadows In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi, Jonas Mureika

Physics Faculty Works

We calculate the characteristics of the “black hole shadow” for a rotating, neutral black hole in fourth-order conformal Weyl gravity. It is shown that the morphology is not significantly affected by the underlying framework, except for very large masses. Conformal gravity black hole shadows would also significantly differ from their general relativistic counterparts if the values of the main conformal gravity parameters, γ and κ, were increased by several orders of magnitude. Such increased values for γ and κ are currently ruled out by gravitational phenomenology. Therefore, it is unlikely that these differences in black hole shadows will be detected …

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Alexander And Writhe Polynomials For Virtual Knots, Blake Mellor Jan 2016

Alexander And Writhe Polynomials For Virtual Knots, Blake Mellor

Mathematics Faculty Works

We give a new interpretation of the Alexander polynomial Δ0 for virtual knots due to Sawollek and Silver and Williams, and use it to show that, for any virtual knot, Δ0 determines the writhe polynomial of Cheng and Gao (equivalently, Kauffman's affine index polynomial). We also use it to define a second-order writhe polynomial, and give some applications.

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