Showing 571 - 580 of 722 Items
Probing the National Geoscience Faculty Survey for Reported Use of Practices that Support Inclusive Learning Environments in Undergraduate Courses
Date: 2019-07-17
Creator: Rachel J. Beane
Karen S. McNeal
R. Heather Macdonald
Access: Open access
- What is the extent to which college and university geoscience faculty report using education practices that contribute to more inclusive learning environments and engage a diverse population of students? In the 2016 National Geoscience Faculty Survey, faculty answered questions about their practices in a specific introductory or major course they had taught in the previous two years, and about how they share and learn about the content and methods used in their teaching. Based on factor analysis, 22 of the survey questions divided into four categories associated with inclusive teaching practices: geoscientist representations, curricular choices, learning strategies, and career pathways. The self-reported use of practices across these four categories varies greatly, with some used by as many as 71% of faculty respondents whereas others by only 8%. These data provide new information on the current state of teaching practices in the geosciences with regard to inclusive practices, and establish a baseline to which responses from future surveys may be compared. Univariate general modeling combined with ANOVA tests on the responses to the questions shows that education practices differ based on variables such as teaching style, communication with colleagues, years of teaching experience, faculty type, institution type, class size, and course type (introductory or major). These differences suggest opportunities for focused geoscience faculty development around education practices that support the success of a diverse population of undergraduate students and the enhancement of inclusive learning environments in the geosciences.
Maintenance of dynamic strain similarity and environmental stres factor in different flow habitats: Thallus allometry and material properties of a giant kelp
Date: 1994-01-01
Creator: A. S. Johnson
M. A.R. Koehl
Access: Open access
Module structure of cells in unequal-parameter Hecke algebras
Date: 2010-09-06
Creator: Thomas Pietraho
Access: Open access
- A conjecture of Bonnafé, Geck, Iancu, and Lam parametrizes Kazhdan-Lusztig left cells for unequal-parameter Hecke algebras in type Bn by families of standard domino tableaux of arbitrary rank. Relying on a family of properties outlined by Lusztig and the recent work of Bonnafé, we verify the conjecture and describe the structure of each cell as a module for the underlying Weyl group. © 2010 by The Editorial Board of the Nagoya Mathematical Journal.
Climate change and health costs of air emissions from biofuels and gasoline
Date: 2009-02-10
Creator: Jason Hill
Stephen Polasky
Erik Nelson
David Tilman
Hong, Huo
Lindsay Ludwig
James Neumann
Haochi Zheng
Diego Bonta
Access: Open access
- Environmental impacts of energy use can impose large costs on society. We quantify and monetize the life-cycle climate-change and health effects of greenhouse gas (GHG) and fine particulate matter (PM2.5) emissions from gasoline, corn ethanol, and cellulosic ethanol. For each billion ethanol-equivalent gallons of fuel produced and combusted in the US, the combined climate-change and health costs are $469 million for gasoline, $472-952 million for corn ethanol depending on biorefinery heat source (natural gas, corn stover, or coal) and technology, but only $123-208 million for cellulosic ethanol depending on feedstock (prairie biomass, Miscanthus, corn stover, or switchgrass). Moreover, a geographically explicit life-cycle analysis that tracks PM2.5 emissions and exposure relative to U.S. population shows regional shifts in health costs dependent on fuel production systems. Because cellulosic ethanol can offer health benefits from PM2.5 reduction that are of comparable importance to its climate-change benefits from GHG reduction, a shift from gasoline to cellulosic ethanol has greater advantages than previously recognized. These advantages are critically dependent on the source of land used to produce biomass for biofuels, on the magnitude of any indirect land use that may result, and on other as yet unmeasured environmental impacts of biofuels. © 2009 by The National Academy of Sciences of the USA.
Solving which trilemma? The many interpretations of equality, Pareto, and freedom of occupational choice
Date: 2017-08-01
Creator: Kristi A. Olson
Access: Open access
- According to the trilemma claim, we cannot have all three of equality, Pareto, and freedom of occupational choice. In response to the trilemma, John Rawls famously sacrificed equality by introducing incentives. In contrast, GA Cohen and others argued that we can, in fact, have all three provided that individuals are properly motivated by an egalitarian ethos. The incentives debate, then, concerns the plausibility of the ethos solution versus the plausibility of the incentives solution. Considerable ink has been spilled on both sides of the debate. Yet, in this essay, I argue that we cannot have this debate until we clarify the terms. Once we clarify the terms, however, we might discover that there is no debate to be had. This is because, depending on how equality, Pareto, and freedom of occupational choice are interpreted, there might not be a trilemma in the first place. Specifically, I use a small but crucial distinction in how equality, the egalitarian ethos, and Pareto are assessed – what I call the internal/external distinction – to disentangle the various paths each solution – the ethos or incentives – could take. I conclude that both solutions have gained illicit plausibility by virtue of not keeping the distinction straight.
Globalizing extraction and indigenous rights in the russian arctic: The enduring role of the state in natural resource governance
Date: 2019-12-01
Creator: Svetlana A. Tulaeva
Maria S. Tysiachniouk
Laura A. Henry
Leah S. Horowitz
Access: Open access
- The governance of extractive industries has become increasingly globalized. International conventions and multi-stakeholder institutions set out rules and standards on a range of issues, such as environmental protection, human rights, and Indigenous rights. Companies' compliance with these global rules may minimize risks for investors and shareholders, while offering people at sites of extraction more leverage. Although the Russian state retains a significant stake in the oil and gas industries, Russian oil and gas companies have globalized as well, receiving foreign investment, participating in global supply chains, and signing on to global agreements. We investigate how this global engagement has affected Nenets Indigenous communities in Yamal, an oil-and gas-rich region in the Russian Arctic, by analyzing Indigenous protests and benefit-sharing arrangements. Contrary to expectations, we find that Nenets Indigenous communities have not been empowered by international governance measures, and also struggle to use domestic laws to resolve problems. In Russia, the state continues to play a significant role in determining outcomes for Indigenous communities, in part by working with Indigenous associations that are state allies. We conclude that governance generating networks in the region are under-developed.
Mechanical Autonomous Stochastic Heat Engine
Date: 2016-06-28
Creator: Marc Serra-Garcia
André Foehr
Miguel Molerón
Joseph Lydon
Christopher, Chong
Chiara Daraio
Access: Open access
- Stochastic heat engines are devices that generate work from random thermal motion using a small number of highly fluctuating degrees of freedom. Proposals for such devices have existed for more than a century and include the Maxwell demon and the Feynman ratchet. Only recently have they been demonstrated experimentally, using, e.g., thermal cycles implemented in optical traps. However, recent experimental demonstrations of classical stochastic heat engines are nonautonomous, since they require an external control system that prescribes a heating and cooling cycle and consume more energy than they produce. We present a heat engine consisting of three coupled mechanical resonators (two ribbons and a cantilever) subject to a stochastic drive. The engine uses geometric nonlinearities in the resonating ribbons to autonomously convert a random excitation into a low-entropy, nonpassive oscillation of the cantilever. The engine presents the anomalous heat transport property of negative thermal conductivity, consisting in the ability to passively transfer energy from a cold reservoir to a hot reservoir.
Systematic ENSO-driven nutrient variability recorded by central equatorial Pacific corals
Date: 2013-08-16
Creator: Michèle LaVigne
Intan S. Nurhati
Kim M. Cobb
Helen V. McGregor
Daniel, Sinclair
Robert M. Sherrell
Access: Open access
- Variations in ocean productivity are driven largely by nutrient supply to the photic zone, but temporal records of nutrient variability are sparse. Here we show scleractinian coral P/Ca proxy records of variations in phosphate concentrations during El Niño Southern Oscillation (ENSO) cycles in the central equatorial Pacific. Covarying P/Ca records in Porites corals from Christmas and Fanning Islands show a regional ∼40% decrease during the upwelling relaxation of the 1997-1998 El Niño, consistent with less frequent nutrient measurements from this area. Similar ∼35-45% skeletal P/Ca decreases occur during the 1982-1983 and 1986-1987 El Niño events, which predate satellite color and regional nutrient measurements. After each El Niño event, nutrient increases lag temperature recovery by 4-12 months, likely reflecting uptake by massive phytoplankton blooms that followed resumption of upwelling. The results support the utility of coral P/Ca to probe the mechanisms linking ENSO, equatorial upwelling, and carbon cycling in the past. © 2013. American Geophysical Union. All Rights Reserved.
All-loop-orders relation between Regge limits of N = 4 SYM and N = 8 supergravity four-point amplitudes
Date: 2021-02-01
Creator: Stephen G. Naculich
Access: Open access
- We examine in detail the structure of the Regge limit of the (nonplanar) N = 4 SYM four-point amplitude. We begin by developing a basis of color factors Cik suitable for the Regge limit of the amplitude at any loop order, and then calculate explicitly the coefficients of the amplitude in that basis through three-loop order using the Regge limit of the full amplitude previously calculated by Henn and Mistlberger. We compute these coefficients exactly at one loop, through O(ϵ 2) at two loops, and through O(ϵ) at three loops, verifying that the IR-divergent pieces are consistent with (the Regge limit of) the expected infrared divergence structure, including a contribution from the three-loop correction to the dipole formula. We also verify consistency with the IR-finite NLL and NNLL predictions of Caron-Huot et al. Finally we use these results to motivate the conjecture of an all-orders relation between one of the coefficients and the Regge limit of the N = 8 supergravity four-point amplitude.
Efficiency of incentives to jointly increase carbon sequestration and species conservation on a landscape
Date: 2008-07-15
Creator: Erik Nelson
Stephen Polasky
David J. Lewis
Andrew J. Plantinga
Eric, Lonsdorf
Denis White
David Bael
Joshua J. Lawler
Access: Open access
- We develop an integrated model to predict private land-use decisions in response to policy incentives designed to increase the provision of carbon sequestration and species conservation across heterogeneous landscapes. Using data from the Willamette Basin, Oregon, we compare the provision of carbon sequestration and species conservation under five simple policies that offer payments for conservation. We evaluate policy performance compared with the maximum feasible combinations of carbon sequestration and species conservation on the landscape for various conservation budgets. None of the conservation payment policies produce increases in carbon sequestration and species conservation that approach the maximum potential gains on the landscape. Our results show that policies aimed at increasing the provision of carbon sequestration do not necessarily increase species conservation and that highly targeted policies do not necessarily do as well as more general policies. © 2008 by The National Academy of Sciences of the USA.