Showing 381 - 390 of 722 Items
Xanthophyll cycle activity in two prominent arctic shrub species
Date: 2017-01-01
Creator: T.S. Magney
B.A. Logan
J.S. Reblin
N.T. Boelman
J.U.H., Eitel
H.E. Greaves
K.L. Griffin
C.M. Prager
L.A. Vierling
Access: Open access
Locating noctiluca miliaris in the arabian sea: An optical proxy approach
Date: 2014-01-01
Creator: Patricia S. Thibodeau
Collin S. Roesler
Susan L. Drapeau
S. G. Prabhu Matondkar
Joaquim I., Goes
P. Jeremy Werdell
Access: Open access
- Coincident with shifting monsoon weather patterns over India, the phytoplankter Noctiluca miliaris has recently been observed to be dominating phytoplankton blooms in the northeastern Arabian Sea during the winter monsoons. Identifying the exact environmental and/or ecological conditions that favor this species has been hampered by the lack of concurrent environmental and biological observations on time and space scales relevant to ecologic and physiologic processes. We present a bio-optical proxy for N. miliaris measured on highly resolved depth scales coincident with hydrographic observations with the goal to identify conducive hydrographic conditions for the bloom. The proxy is derived from multichannel excitation chlorophyll a fluorescence and is validated with microscopy, pigment composition, and spectral absorption. Phytoplankton populations dominated by either diatoms or other dinoflagellates were additionally discerned. N. miliaris populations in full bloom were identified offshore in low-nutrient and low–N:P ratio surface waters within a narrow temperature and salinity range. These populations transitioned to high-biomass diatom-dominated coastal upwelling populations. A week later, the N. miliaris blooms were observed in declining phase, transitioning to very-low-biomass populations of non–N. miliaris dinoflagellates. There were no clear hydrographic conditions uniquely associated with the N. miliaris populations, although N. miliaris was not found in the upwelling or extremely oligotrophic waters. Taxonomic transitions were not discernible in the spatial structure of the bloom as identified by the ocean color Chl imagery, indicating that in situ observations may be necessary to resolve community structure, particularly for populations below the surface.
Measuring Creative Performance of Teams Through Dynamic Semantic Social Network Analysis
Creator: Peter Gloor
Access: Open access
- In this project we compare communication structure and content exchanged by members of creative, interdisciplinary teams of medical researchers, physicians, patients and caretakers with their creative output. We find that longitudinal social networking patterns and word usage predict creative performance. We collected the e-mail archives of 60 members of a community of researchers working on 12 projects improving various aspects of the daily lives of patients of Crohn’s disease. Our results indicate that more creative projects show a decrease in group density, while more actors are involved, and more emails are exchanged, suggesting that a more successful project attracts more attention from many different people. We also found that members of more creative projects use more emotional language, which gets more focused over time.
Contingent planning under uncertainty via stochastic satisfiability
Date: 2003-07-01
Creator: Stephen M. Majercik
Michael L. Littman
Access: Open access
- We describe a new planning technique that efficiently solves probabilistic propositional contingent planning problems by converting them into instances of stochastic satisfiability (SSAT) and solving these problems instead. We make fundamental contributions in two areas: the solution of SSAT problems and the solution of stochastic planning problems. This is the first work extending the planning-as-satisfiability paradigm to stochastic domains. Our planner, ZANDER, can solve arbitrary, goal-oriented, finite-horizon partially observable Markov decision processes (POMDPs). An empirical study comparing ZANDER to seven other leading planners shows that its performance is competitive on a range of problems. © 2003 Elsevier Science B.V. All rights reserved.
Subversive, mother, killjoy: Sexism against dilma rousseff and the social imaginary of Brazil’s rightward turn
Date: 2019-03-01
Creator: Joseph Jay Sosa
Access: Open access
- From resistance fighter against Brazil’s military dictatorship to its first female president, Dilma Rousseff’s biography follows the historic arc of democratization in Brazil. Her 2016 impeachment was also the culminating event of numerous crises that polarized Brazilian society. To supporters, Rousseff’s removal without evidence constitutes an abrogation of democracy. To critics, Rousseff had to answer for an economic recession and widespread corruption (though she was not implicated in any investigation). This article examines the social imaginaries of the rightward turn that made Rousseff’s removal possible. Moving across diverse sets of public culture-street protests, journalistic accounts, political observations, and Rousseff’s speeches-the article uses sexism against Rousseff as an analytic to deconstruct the cultural narratives of Brazil’s rightward turn. A first section considers conservative efforts to paint Rousseff as a political subversive. These accusations drew on long-standing, right-wing Brazilian tropes around people who don’t “act right” in the moral, sexual, and ideological fields. A second section reads the maternal metaphors of Rousseff’s governance strategies against conflicting political renderings of the family-pitting left-wing versions of family rooted in economic development against Evangelical Christian accounts of the family as a gender-normative unit. A third section argues that Rousseff’s response to the charges against her turned her (and those who argued her case) into what Sara Ahmed calls “feminist killjoys.” Ultimately, the question of sexism in Rousseff’s impeachment shows how deep-seated cultural conservatisms can be activated in a new era of democratic uncertainty.
A critical, analytical framework for the digital machine
Date: 2021-01-01
Creator: Crystal Hall
Eric Chown
Fernando Nascimento
Access: Open access
- The Faculty of Digital and Computational Studies (DCS) at Bowdoin College proposes a critical, analytical framework, referred to as the ‘4As,’ as an interdisciplinary means to interpret, evaluate, and create the data, operations, and devices of computing across all domains of knowledge production. Following other disciplines that have developed in symbiotic relationships to one another, DCS puts computation in conversation with fields from across the arts, humanities, physical, and social sciences. Our foundational premise is the bidirectional influence between these disciplines and digital artifacts and computation. The 4As (artifact, architecture, abstraction, and agency) benefit from both the scepticism of the liberal arts in the face of ubiquitous digital processes and the analytical opening for examining questions pertaining to creative and imaginative alternatives to the digital and computational status quo. We provide an ultra-contemporary case study to demonstrate the framework in use.
Using 'big data' to explain visits to lakes in 17 US states
Date: 2020-07-01
Creator: Erik Nelson
Maggie Rogers
Spencer Wood
Jesse Chung
Bonnie, Keeler
Access: Open access
- We use large dataset on US lakes from 17 states to estimate the relationship between summertime visits to lakes as proxied by social media use and the lakes' water quality, amenities, and surrounding landscape features and socioeconomic conditions. Prior to estimating these relationships we worked on 1) selecting a parsimonious set of explanatory variables from a roster of more than 100 lake attributes and 2) accounting for the non-random pattern of missing water quality data. These steps 1) improved the interpretability of the estimated visit models and 2) widened our estimated models' scope of statistical inference. We used Machine Learning techniques to select parsimonious sets of explanatory variables and multiple imputation to estimate water quality at lakes missing this data. We found the following relationships between summertime visits to lake and their attributes across the 17-state region. First, we estimated that every additional meter of average summer-time Secchi depth between 1995 and 2014 was associated with at least 7.0% more summer-time visits to a lake between 2005 to 2014, all else equal. Second, we consistently found that lake amenities, such as beaches, boat launches, and public toilets, were more powerful predictors of visits than water quality. Third, we also found that visits to a lake were strongly influenced by the lake's accessibility and its distance to nearby lakes and the amenities the nearby lakes offered. Finally, our results highlight the biased results that "big data"-based research on recreation can generate if non-random missing observation patterns in the data are not corrected.
Projected land-use change impacts on ecosystem services in the United States
Date: 2014-05-20
Creator: Joshua J. Lawler
David J. Lewis
Erik Nelson
Andrew J. Plantinga
Stephen, Polasky
John C. Withey
David P. Helmers
Sebastián Martinuzzi
Derric Penningtonh
Access: Open access
- Providing food, timber, energy, housing, and other goods and services, while maintaining ecosystem functions and biodiversity that underpin their sustainable supply, is one of the great challenges of our time. Understanding the drivers of land-use change and how policies can alter land-use change will be critical to meeting this challenge. Here we project land-use change in the contiguous United States to 2051 under two plausible baseline trajectories of economic conditions to illustrate how differences in underlying market forces can have large impacts on land-use with cascading effects on ecosystem services and wildlife habitat. We project a large increase in croplands (28.2 million ha) under a scenario with high crop demand mirroring conditions starting in 2007, compared with a loss of cropland (11.2 million ha) mirroring conditions in the 1990s. Projected land-use changes result in increases in carbon storage, timber production, food production from increased yields, and >10% decreases in habitat for 25% of modeled species. We also analyze policy alternatives designed to encourage forest cover and natural landscapes and reduce urban expansion. Although these policy scenarios modify baseline land-use patterns, they do not reverse powerful underlying trends. Policy interventions need to be aggressive to significantly alter underlying land-use change trends and shift the trajectory of ecosystem service provision.
Accelerating change: The power of faculty change agents to promote diversity and inclusive teaching practices
Date: 2019-10-02
Creator: R. Heather Macdonald
Rachel J. Beane
Eric M.D. Baer
Pamela L. Eddy
Norlene R., Emerson
Jan Hodder
Ellen R. Iverson
John R. McDaris
Kristin O’Connell
Carol J. Ormand
Access: Open access
- Faculty play an important role in attracting students to the geosciences, helping them to thrive in geoscience programs, and preparing them for careers. Thus, faculty have the responsibility to work toward broadening participation in the geosciences by implementing equitable and inclusive practices in their teaching and their programs. Faculty professional development that promotes diversity and inclusion is one way to move evidence-based practices into wider use. The adoption of these practices may be accelerated through a professional development diffusion model that amplifies the impacts through the work of faculty change agents. An example of this approach is the SAGE 2YC professional development program, in which faculty change agents learn and practice strategies during workshop sessions, implement changes in their own teaching, and then work in teams to lead workshops in their region under the auspices of the national program. Although this example focuses on two-year colleges, the model is applicable to faculty professional development more broadly. The success of the model is due in large part to a suite of leader-developed workshop sessions and curated resources that change agent teams may select and adapt for the regional workshops they lead. Furthermore, change agents are trusted colleagues, which makes adoption of the evidence-based practices by regional workshop participants more likely. Increased adoption of a change agent approach to faculty development will support the creation and sharing of additional resources, leading to wider diffusion and implementation of inclusive teaching practices.
Making predictions in an uncertain world: Environmental structure and cognitive maps
Date: 1999-01-01
Creator: Eric Chown
Access: Open access
- This article examines the relationship between environmental and cognitive structure. One of the key tasks for any agent interacting in the real world is the management of uncertainty; because of this the cognitive structures which interact with real environments, such as would be used in navigation, must effectively cope with the uncertainty inherent in a constantly changing world. Despite this uncertainty, however, real environments usually afford structure that can be effectively exploited by organisms. The article examines environmental characteristics and structures that enable humans to survive and thrive in a wide range of real environments. The relationship between these characteristics and structures, uncertainty, and cognitive structure is explored in the context of PLAN, a proposed model of human cognitive mapping, and R-PLAN, a version of PLAN that has been instantiated on an actual mobile robot. An examination of these models helps to provide insight into environmental characteristics which impact human performance on tasks which require interaction with the world. Copyright 1999 International Society for Adaptive Behavior.