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Portland State University

2022

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Articles 181 - 184 of 184

Full-Text Articles in Physical Sciences and Mathematics

Patterns Of Interdisciplinary Collaboration Resemble Biogeochemical Relationships In The Mcmurdo Dry Valleys, Antarctica: A Historical Social Network Analysis Of Science, 1907–2016, Stephen M. Chignell, Adrian Howkins, Poppie Gullett, Andrew G. Fountain Jan 2022

Patterns Of Interdisciplinary Collaboration Resemble Biogeochemical Relationships In The Mcmurdo Dry Valleys, Antarctica: A Historical Social Network Analysis Of Science, 1907–2016, Stephen M. Chignell, Adrian Howkins, Poppie Gullett, Andrew G. Fountain

Geology Faculty Publications and Presentations

Co-authorship networks can provide key insights into the production of scientific knowledge. This is particularly interesting in Antarctica, where most human activity relates to scientific research. Bibliometric studies of Antarctic science have provided a useful understanding of international and interdisciplinary collaboration, yet most research has focused on broad-scale analyses over recent time periods. Here, we take advantage of a ‘Goldilocks’ opportunity in the McMurdo Dry Valleys, an internationally important region of Antarctica and the largest ice-free region on the continent. The McMurdo Dry Valleys have attracted continuous and diverse scientific activity since 1958. It is a geographically confined region with …

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A One-Dimensional Field Dislocation Mechanics Model Using Discontinuous Galerkin Method, Ja'nya Breeden, Dow Drake, Jay Gopalakrishnan, Saurabh Puri Jan 2022

A One-Dimensional Field Dislocation Mechanics Model Using Discontinuous Galerkin Method, Ja'nya Breeden, Dow Drake, Jay Gopalakrishnan, Saurabh Puri

Mathematics and Statistics Faculty Publications and Presentations

A numerical solution strategy for a one-dimensional field dislocation mechanics (FDM) model using the Discontinuous Galerkin (DG) method is developed. The FDM model is capable of simulating the dynamics of discrete, nonsingular dislocations using a partial differential equation involving a conservation law for the Burgers vector content with constitutive input for nucleation and velocity. Modeling of individual dislocation lines with an equilibrium compact core structure in the context of this continuum elastoplastic framework requires a non-convex stored energy density. Permanent deformation and stress redistribution caused by the dissipative transport of dislocations is modeled using thermodynamics-based constitutive laws. A DG method …

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Periodic Points Of Polynomials Over Finite Fields, Derek Garton Jan 2022

Periodic Points Of Polynomials Over Finite Fields, Derek Garton

Mathematics and Statistics Faculty Publications and Presentations

Fix an odd prime p. If r is a positive integer and f is a polynomial with coefficients in Fpr, let Pp,r⁡(f) be the proportion of P1⁢(Fpr) that is periodic with respect to f. We show that as r increases, the expected value of Pp,r⁡(f), as f ranges over quadratic polynomials, is less than 22/(log⁡log⁡pr). This result follows from a uniformity theorem on specializations of dynamical systems of rational functions over residually finite Dedekind domains. The specialization theorem generalizes previous work by Juul et al. that holds for rings of integers of number fields. Moreover, under stronger hypotheses, we effectivize …

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Equivalence Of The Transition Heat Capacities Of Proteins And Dna, Matthew W. Eskew, Albert S. Benight Jan 2022

Equivalence Of The Transition Heat Capacities Of Proteins And Dna, Matthew W. Eskew, Albert S. Benight

Chemistry Faculty Publications and Presentations

It has been reported for many globular proteins that the native heat capacity at 25°C, per gram, is the same. This has been interpreted to indicate that heat capacity is a fundamental property of native proteins that provides important information on molecular structure and stability. Heat capacities for both proteins and DNA has been suggested to be related to universal effects of hydration/solvation on native structures. Here we report on results from thermal denaturation analysis of two well-known proteins, human serum albumin and lysozyme, and a short DNA hairpin. The transition heat capacities at the Tm for the three molecules …

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