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Search Results: 1 - 10 of 462639 matches for " Brad A. Seibel "
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Energetic Plasticity Underlies a Variable Response to Ocean Acidification in the Pteropod, Limacina helicina antarctica
Brad A. Seibel, Amy E. Maas, Heidi M. Dierssen
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030464
Abstract: Ocean acidification, caused by elevated seawater carbon dioxide levels, may have a deleterious impact on energetic processes in animals. Here we show that high PCO2 can suppress metabolism, measured as oxygen consumption, in the pteropod, L. helicina forma antarctica, by ~20%. The rates measured at 180–380 μatm (MO2 = 1.25 M?0.25, p = 0.007) were significantly higher (ANCOVA, p = 0.004) than those measured at elevated target CO2 levels in 2007 (789–1000 μatm, = 0.78 M?0.32, p = 0.0008; Fig. 1). However, we further demonstrate metabolic plasticity in response to regional phytoplankton concentration and that the response to CO2 is dependent on the baseline level of metabolism. We hypothesize that reduced regional Chl a levels in 2008 suppressed metabolism and masked the effect of ocean acidification. This effect of food limitation was not, we postulate, merely a result of gut clearance and specific dynamic action, but rather represents a sustained metabolic response to regional conditions. Thus, pteropod populations may be compromised by climate change, both directly via CO2-induced metabolic suppression, and indirectly via quantitative and qualitative changes to the phytoplankton community. Without the context provided by long-term observations (four seasons) and a multi-faceted laboratory analysis of the parameters affecting energetics, the complex response of polar pteropods to ocean acidification may be masked or misinterpreted.
The real limits to marine life: a further critique of the Respiration Index
B. A. Seibel,J. J. Childress
Biogeosciences Discussions , 2012, DOI: 10.5194/bgd-9-16521-2012
Abstract: The recently proposed "Respiration Index" (RI = log[PO2]/[PCO2]) suggests that aerobic metabolism is limited by the ratio of reactants (R, oxygen) and products (P, carbon dioxide) according to the thermodynamics of cellular respiration. Here we demonstrate that, because of the large standard free energy change for organic carbon oxidation (ΔG° = 686 kcal mol 1), carbon dioxide can never reach concentrations that would limit the thermodynamics of this reaction. A PCO2 to PO2 ratio of 10503 would be required to reach equilibrium (equilibrium constant, Keq = 10503), where ΔG = 0. Thus a respiration index of 503 would be the real thermodynamic limit to aerobic life. Such a Respiration Index is never reached either in the cell or in the environment. Moreover cellular respiration and oxygen provision are kinetically controlled such that, within limits, environmental oxygen and CO2 concentrations have little to do with intracellular concentrations. The RI is fundamentally different from the aragonite saturation state, a thermodynamic index used to quantify the potential effect of CO2 on calcification rates, because of its failure to incorporate the equilibrium constant of the reaction. Not only is the RI invalid, its use leads to incorrect and dangerous predictions of the threat of changing oxygen and carbon dioxide to marine life. We provide a physiological model that identifies oxygen thresholds, and allows for synergistic effects of ocean acidification and global warming.
YouTube as a Source of Information on Confined Space Safety
Muise A Brad,Brad Freeman,Earl Blair
International Journal of Occupational Safety and Health , 2012, DOI: 10.3126/ijosh.v2i1.5626
Abstract: Safety professionals looking for information on confined space safety often use the Internet as a resource. YouTube is a popular website that may be used to supplement safety training or as a source of information pertaining to Confined Spaces (CS).??YouTube was examined as a source of information on CS safety.
Poles Apart: The “Bipolar” Pteropod Species Limacina helicina Is Genetically Distinct Between the Arctic and Antarctic Oceans
Brian Hunt,Jan Strugnell,Nina Bednarsek,Katrin Linse,R. John Nelson,Evgeny Pakhomov,Brad Seibel,Dirk Steinke,Laura Würzberg
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009835
Abstract: The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five “forma”. However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (±0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems.
Optimal Time-Trial Bicycle Racing with Headwinds and Tailwinds
A. Brad Anton
Physics , 2013,
Abstract: Many time-trial and triathlon bicycle races take place on relatively flat, closed-circuit courses. In the absence of hills, riding-speed is limited almost solely by aerodynamic drag; consequently, winds can have a big effect on elapsed times. I analyze the special case of a straight out-and-back race in a steady wind, assuming the rider has a given total amount of energy to expend and can choose only two speeds - the aided speed with tailwind and the hindered speed into headwind. In this ideal circumstance the problem of choosing optimal riding speeds reduces to a constrained nonlinear optimization that can be solved with elementary calculus. My analysis reveals a practical rule of thumb that can be used more generally to choose optimal riding speeds for time-trial racing on closed-circuit courses in the presence of headwinds and tailwinds.
The metabolic response of pteropods to acidification reflects natural CO2-exposure in oxygen minimum zones
A. E. Maas, K. F. Wishner,B. A. Seibel
Biogeosciences (BG) & Discussions (BGD) , 2012,
Abstract: Shelled pteropods (Thecosomata) are a group of holoplanktonic mollusks that are believed to be especially sensitive to ocean acidification because their aragonitic shells are highly soluble. Despite this concern, there is very little known about the physiological response of these animals to conditions of elevated carbon dioxide. This study examines the oxygen consumption and ammonia excretion of five pteropod species, collected from tropical regions of the Pacific Ocean, to elevated levels of carbon dioxide (0.10%, 1000 ppm). Our results show that pteropods that naturally migrate into oxygen minimum zones, such as Hyalocylis striata, Clio pyramidata, Cavolinia longirostris and Creseis virgula, were not affected by carbon dioxide at the levels and duration tested. Diacria quadridentata, which does not migrate, responds to high carbon dioxide conditions with reduced oxygen consumption and ammonia excretion. This indicates that the natural chemical environment of individual species may influence their resilience to ocean acidification.
The metabolic response of pteropods to ocean acidification reflects natural CO2-exposure in oxygen minimum zones
A. E. Maas,K. F. Wishner,B. A. Seibel
Biogeosciences Discussions , 2011, DOI: 10.5194/bgd-8-10295-2011
Abstract: Shelled pteropods (Thecosomata) are a group of holoplanktonic mollusks that are believed to be especially sensitive to ocean acidification because their aragonitic shells are highly soluble. Despite this concern, there is very little known about the physiological response of these animals to conditions of elevated carbon dioxide. This study examines the oxygen consumption and ammonia excretion of five pteropod species, collected from tropical regions of the Pacific Ocean, to elevated levels of carbon dioxide (0.10%, 1000 ppm). Our results show that pteropods that naturally migrate into oxygen minimum zones, such as Hyalocylis striata, Clio pyramidata, Cavolinia longirostris and Creseis virgula, were not affected by carbon dioxide at the levels and duration tested. Diacria quadridentata, which does not migrate, responds to high carbon dioxide conditions with reduced oxygen consumption and ammonia excretion. This indicates that the natural chemical environment of individual species influences their resilience to ocean acidification.
Psychoeducational Group Curriculum to Address American Indian Marginalization  [PDF]
Jesse A. Steinfeldt, Brad D. Foltz, Rex A. Stockton
Creative Education (CE) , 2014, DOI: 10.4236/ce.2014.520199
Abstract: As a mechanism for collaborative group learning, we have designed a psychoeducational group curriculum that utilizes social justice principles within a liberation framework to address societal marginalization of American Indian communities. The curriculum within this proposed psychoeducational group format helps educators facilitate student exploration of societal portrayals of American Indians with the intent of developing action plans to address social injustice. Students exposed to the curriculum within this psychoeducational group will be equipped with critical thinking skills to transform their emerging social justice awareness and knowledge into social justice skills. Additionally, educators who lead this group can become social justice role models for others by using this experience to address issues of oppression and marginalization that are manifest in other forms in society.
Review: Iwanaga, Kazuki (ed.) (2008), Women and Politics in Thailand: Continuity and Change
Lydia Seibel
Journal of Current Southeast Asian Affairs , 2010,
Abstract: Review of the edited volume: Iwanaga, Kazuki (ed.) (2008), Women and Politics in Thailand: Continuity and Change, Copenhagen: NIAS Press, ISBN 9788791114359, 284 pages.
ExpressionPlot: a web-based framework for analysis of RNA-Seq and microarray gene expression data
Brad A Friedman, Tom Maniatis
Genome Biology , 2011, DOI: 10.1186/gb-2011-12-7-r69
Abstract: RNA-Seq has emerged in recent years as the eminent platform for analysis of gene expression and RNA processing [1-3]. However, processing the raw sequence data to get useful and accurate information about gene expression and RNA processing is still a daunting task, even for computationally inclined researchers. High quality software packages now exist to perform specific steps in the analysis pipeline [4-10], as well as web-based systems such as Galaxy [11] and GenePattern [12] that enable the management of data flow through these tools. We present ExpressionPlot, an open source solution consisting of a back end pipeline, which performs alignment and statistical analyses, and a web-based front end, which allows users to explore and further compare the completed analyses. Compared to Galaxy and GenePattern, ExpressionPlot's web-based front end is novel in the ease with which one can browse and manipulate gene expression results: gene/isoform lists are one-click filterable, sortable and hyperlinked to the underlying genomic regions in the table_browser tool. Furthermore, even with differing platforms (such as microarray versus RNA-Seq) or organisms (such as mouse versus human), the front end can automatically compare changes in gene expression across different experiments using the 4 way and heatmap tools.ExpressionPlot can be tested as a virtual machine (running under VirtualBox), or installed directly into an existing web server. Input to ExpressionPlot can be raw sequence data (FASTQ files) or Affymetrix array data (CEL files), completed alignments (BAM files), or tables of gene expression values and changes generated by other back ends. Once data are pre-processed, the web-based front end allows users to easily browse measures of quality control, plot changes in gene expression and RNA processing, browse hyperlinked tables of changed genes and splicing events, generate read plots from a genomic view, compare different datasets (including from different organisms o
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