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Willis W.T.,Arizona State University | Jackman M.R.,Aurora University | Messer J.I.,Mesa Community College | Kuzmiak-Glancy S.,George Washington University | Glancy B.,U.S. National Institutes of Health
Medicine and Science in Sports and Exercise

Mitochondrial oxidative phosphorylation is the primary source of cellular energy transduction in mammals. This energy conversion involves dozens of enzymatic reactions, energetic intermediates, and the dynamic interactions among them. With the goal of providing greater insight into the complex thermodynamics and kinetics ("thermokinetics") of mitochondrial energy transduction, a simple hydraulic analog model of oxidative phosphorylation is presented. In the hydraulic model, water tanks represent the forward and back "pressures" exerted by thermodynamic driving forces: the matrix redox potential (ΔG redox), the electrochemical potential for protons across the mitochondrial inner membrane (ΔG H +), and the free energy of adenosine 5′-triphosphate (ATP) (ΔG ATP). Net water flow proceeds from tanks with higher water pressure to tanks with lower pressure through "enzyme pipes" whose diameters represent the conductances (effective activities) of the proteins that catalyze the energy transfer. These enzyme pipes include the reactions of dehydrogenase enzymes, the electron transport chain (ETC), and the combined action of ATP synthase plus the ATP-adenosine 5′-diphosphate exchanger that spans the inner membrane. In addition, reactive oxygen species production is included in the model as a leak that is driven out of the ETC pipe by high pressure (high ΔG redox) and a proton leak dependent on the ΔG H + for both its driving force and the conductance of the leak pathway. Model water pressures and flows are shown to simulate thermodynamic forces and metabolic fluxes that have been experimentally observed in mammalian skeletal muscle in response to acute exercise, chronic endurance training, and reduced substrate availability, as well as account for the thermokinetic behavior of mitochondria from fast- and slow-twitch skeletal muscle and the metabolic capacitance of the creatine kinase reaction. © 2016 by the American College of Sports Medicine. Source

Poland M.P.,U.S. Geological Survey | Van Der Hoeven Kraft K.J.,Mesa Community College | Teasdale R.,California State University, Chico

Using On-Line Volcano Monitoring Data in College and University Courses: The Volcano Exploration Project: Pu'u " (VEPP); Hawaii Volcanoes National Park, Hawaii, 26-30 July 2010; Volcanic activity is an excellent hook for engaging college and university students in geoscience classes. An increasing number of Internet-accessible real-time and near-real time volcano monitoring data are now available and constitute an important resource for geoscience education; however, relatively few data sets are comprehensive, and many lack background information to aid in interpretation. In response to the need for organized, accessible, and well-documented volcano education resources, the U.S. Geological Survey's Hawaiian Volcano Observatory (HVO), in collaboration with NASA and the University of Hawai'i at Manoa, established the Volcanoes Exploration Project: Pu'u " (VEPP). The VEPP Web site (http://vepp.wr.usgs. gov) is an educational resource that provides access, in near real time, to geodetic, seismic, and geologic data from the active Pu'u " eruptive vent on Kilauea volcano, Hawaii, along with background and context information. A strength of the VEPP site is the common theme of the Pu'u " eruption, which allows the site to be revisited multiple times to demonstrate different principles and integrate many aspects of volcanology. Source

Dorn R.I.,Arizona State University | Gordon S.J.,United States Air Force Academy | Allen C.D.,University of Colorado at Denver | Cerveny N.,Mesa Community College | And 9 more authors.

Researchers exploring rock decay hail from chemistry, engineering, geography, geology, paleoclimatology, soil science, and other disciplines and use laboratory, microscopic, theoretical, and field-based strategies. We illustrate here how the tradition of fieldwork forms the core knowledge of rock decay and continues to build on the classic research of Blackwelder, Bryan, Gilbert, Jutson, King, Linton, Twidale, and von Humboldt. While development of nonfield-based investigation has contributed substantially to our understanding of processes, the wide range of environments, stone types, and climatic variability encountered raises issues of temporal and spatial scales too complex to fit into attempts at universal modeling. Although nonfield methods are immensely useful for understanding overarching processes, they can miss subtle differences in factors that ultimately shape rock surfaces. We, therefore, illustrate here how the tradition of fieldwork continues today alongside laboratory and computer-based investigations and contributes to our understanding of rock decay processes. This includes the contribution of fieldwork to the learning process of undergraduates, the calculation of activation energies of plagioclase and olivine dissolution, the high Arctic, the discovery of a new global carbon sink, the influence of plant roots, an analysis of the need for protocols, tafoni development, stone monuments, and rock coatings. These compiled vignettes argue that, despite revolutionary advances in instrumentation, rock decay research must remain firmly footed in the field. © 2012 Elsevier B.V. Source

Vodopivec A.,IMFM | Kaatz F.H.,University of Advancing Technology | Kaatz F.H.,Chandler Gilbert Community College | Kaatz F.H.,Mesa Community College | Mohar B.,Simon Fraser University
Journal of Mathematical Chemistry

The topographical Wiener index is calculated for two-dimensional graphs describing porous arrays, including bee honeycomb. For tiling in the plane, we model hexagonal, triangular, and square arrays and compare with topological formulas for the Wiener index derived from the distance matrix. The normalized Wiener indices of C 4, T 13, and O(4), for hexagonal, triangular, and square arrays are 0.993, 0.995, and 0.985, respectively, indicating that the arrays have smaller bond lengths near the center of the array, since these contribute more to the Wiener index. The normalized Perron root (the first eigenvalue, λ 1), calculated from distance/distance matrices describes an order parameter, Φ = λ 1/n, where Φ = 1 for a linear graph and n is the order of the matrix. This parameter correlates with the convexity of the tessellations. The distributions of the normalized distances for nearest neighbor coordinates are determined from the porous arrays. The distributions range from normal to skewed to multimodal depending on the array. These results introduce some new calculations for 2D graphs of porous arrays. © Springer Science+Business Media, LLC 2009. Source

Wood D.A.,U.S. Geological Survey | Vandergast A.G.,U.S. Geological Survey | Lemos Espinal J.A.,Laboratorio Of Ecologia | Fisher R.N.,U.S. Geological Survey | And 2 more authors.
Molecular Ecology

Glacial-interglacial cycles of the Pleistocene are hypothesized as one of the foremost contributors to biological diversification. This is especially true for cold-adapted montane species, where range shifts have had a pronounced effect on population-level divergence. Gartersnakes of the Thamnophis rufipunctatus species complex are restricted to cold headwater streams in the highlands of the Sierra Madre Occidental and southwestern USA. We used coalescent and multilocus phylogenetic approaches to test whether genetic diversification of this montane-restricted species complex is consistent with two prevailing models of range fluctuation for species affected by Pleistocene climate changes. Our concatenated nuDNA and multilocus species analyses recovered evidence for the persistence of multiple lineages that are restricted geographically, despite a mtDNA signature consistent with either more recent connectivity (and introgression) or recent expansion (and incomplete lineage sorting). Divergence times estimated using a relaxed molecular clock and fossil calibrations fall within the Late Pleistocene, and zero gene flow scenarios among current geographically isolated lineages could not be rejected. These results suggest that increased climate shifts in the Late Pleistocene have driven diversification and current range retraction patterns and that the differences between markers reflect the stochasticity of gene lineages (i.e. ancestral polymorphism) rather than gene flow and introgression. These results have important implications for the conservation of T. rufipunctatus (sensu novo), which is restricted to two drainage systems in the southwestern US and has undergone a recent and dramatic decline. © 2011 Blackwell Publishing Ltd. Source

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