Faculty Scholarship
Showing 11 - 20 of 733 Items
Under the hood of satellite empirical chlorophyll a algorithms: Revealing the dependencies of maximum band ratio algorithms on inherent optical properties
Date: 2012-09-10
Creator: Michael J. Sauer, C. S. Roesler, P. J. Werdell, A. Barnard
Access: Open access
- Empirically-based satellite estimates of chlorophyll a [Chl] (e.g. OC3) are an important indicator of phytoplankton biomass. To correctly interpret [Chl] variability, estimates must be accurate and sources of algorithm errors known. While the underlying assumptions of band ratio algorithms such as OC3 have been tacitly hypothesized (i.e. CDOM and phytoplankton absorption covary), the influence of component absorption and scattering on the shape of the algorithm and estimated [Chl] error has yet to be explicitly revealed. We utilized the NOMAD bio-optical data set to examine variations between satellite estimated [Chl] and in situ values. We partitioned the variability into (a) signal contamination and (b) natural phytoplankton variability (variability in chlorophyll-specific phytoplankton absorption). Not surprisingly, the OC3 best-fit curve resulted from a balance between these two different sources of variation confirming the bias by detrital absorption on global scale. Unlike previous descriptions of empirical [Chl] algorithms, our study (a) quantified the mean detrital:phytoplankton absorption as ~1:1in the global NOMAD data set, and (b) removed detrital (CDOM + non-algal particle) absorption in radiative transfer models directly showing that the scale of the remaining variability in the band ratio algorithm was dominated by phytoplankton absorption cross section. © 2012 Optical Society of America.
Waterfowl habitat change over five decades in a freshwater tidal ecosystem in mid-coast maine
Date: 2011-01-01
Creator: J. Lichter, M.E.H. Burton, S.L. Close, J.M. Grinvalsky, J., Reblin
Access: Open access
Underway and moored methods for improving accuracy in measurement of spectral particulate absorption and attenuation
Date: 2010-10-01
Creator: Wayne H. Slade, Emmanuel Boss, Giorgio Dall'olmo, M. Rois Langner, James, Loftin, Michael J. Behrenfeld, Collin Roesler, Toby K. Westberry
Access: Open access
- Optical sensors have distinct advantages when used in ocean observatories, autonomous platforms, and on vessels of opportunity, because of their high-frequency measurements, low power consumption, and the numerous established relationships between optical measurements and biogeochemical variables. However, the issues of biofouling and instrument stability over time remain complicating factors when optical instruments are used over periods longer than several days. Here, a method for obtaining calibration-independent measurements of spectral particle absorption and attenuation is presented. Flow-through optical instrumentation is routinely diverted through a large-surface area 0.2-μm cartridge filter, allowing for the calculation of particle optical properties by differencing temporally adjacent filtered and whole water samples. This approach yields measurements that are independent of drift in instrument calibration. The method has advantages not only for coastally moored deployments, but also for applications in optically clear waters where uncertainties in instrument calibration can be a significant part of the signal measured. The differencing technique is demonstrated using WET Labs (Philomath, Oregon) ac-9 and ac-s multi- and hyperspectral absorption and attenuation meters. For the ac-s sensor, a correction scheme is discussed that utilizes the spectral shape of water absorption in the near-infrared to improve the accuracy of temperature and scattering-corrected spectra. Flow-through particulate absorption measurements are compared with discrete filter-pad measurements and are found to agree well (R = 0.77; rmse = 0.0174 m ). © 2010 American Meteorological Society. 2 -1
The Future of Social Movement Organizations: The Waning Dominance of SMOs Online
Date: 2013-04-12
Creator: Jennifer Earl
Access: Open access
- For scholars interested in the role of information communication technologies (ICTs) in protest and social movements, the importance of organizations doesn’t appear to be as axiomatic. Work over the past decade researching “Internet activism” has raised fundamental questions about SMOs and their continuing importance to protest: Do organizations play the same role in online protest as they have played in offline protest? Are SMOs as necessary for online movements and protest organizing? What role or functions do SMOs play in online protest? In this article, I address these questions by first surveying social movement research on pre-Internet protest to establish how traditional social movement scholarship understands the role and impact of SMOs. I then compare these expectations to existing work on online protest. In the end, I argue that there are a variety of factors that contribute to the declining necessity of SMOs. Nonetheless, I point to some advantages that SMOs still seem to offer over other forms of organizing. Finally, I discuss the differences between a movement ecology devoid of SMOs versus one that has some level of SMO presence as well as reasons why SMOs might persist, separate and apart from the advantages the organizational form imparts.
Understanding the effect of political advertising on voter turnout: A response to Krasno and Green
Date: 2008-01-01
Creator: Michael M. Franz, Paul Freedman, Ken Goldstein, Travis N. Ridout
Access: Open access
- Krasno and Green have argued that political advertising has no impact on voter turnout. We remain unconvinced by their evidence, given concerns about how they measure the advertising environment, how they measure advertising tone, their choice of modeling techniques and the generalizability of their findings. These differences aside, we strongly agree that political advertising does little to undermine voter participation. © 2008 Southern Political Science Association.
Climate change's impact on key ecosystem services and the human well-being they support in the US
Date: 2013-11-01
Creator: Erik J. Nelson, Peter Kareiva, Mary Ruckelshaus, Katie Arkema, Gary, Geller, Evan Girvetz, Dave Goodrich, Virginia Matzek, Malin Pinsky
Access: Open access
- Climate change alters the functions of ecological systems. As a result, the provision of ecosystem services and the well-being of people that rely on these services are being modified. Climate models portend continued warming and more frequent extreme weather events across the US. Such weather-related disturbances will place a premium on the ecosystem services that people rely on. We discuss some of the observed and anticipated impacts of climate change on ecosystem service provision and livelihoods in the US. We also highlight promising adaptive measures. The challenge will be choosing which adaptive strategies to implement, given limited resources and time. We suggest using dynamic balance sheets or accounts of natural capital and natural assets to prioritize and evaluate national and regional adaptation strategies that involve ecosystem services. © The Ecological Society of America.
The Effects of Corporate Governance on the Innovation Performance of Chinese SMEs
Date: 2013-03-10
Creator: Yao Tang, Daniel Shapiro, Miaojun Wang, Weiying Zhang
Access: Open access
- We investigate the degree to which corporate governance and ownership affects the innovation performance of firms in China with a particular focus on privately owned small and medium enterprises (SMEs). We hypothesize that (1) board-related governance measures will enhance innovation because they improve monitoring and provide access to necessary resources; (2) ownership concentration initially facilitates innovation because large shareholders are more likely to commit to the long-term nature of innovation, and have the incentive to monitor managers whose time horizon may be shorter; however we argue that these effects weaken as large shareholders becomes entrenched at higher levels of concentration; and (3) hiring an external CEO will enhance innovation both by ensuring professional management of the company, and by alleviating the entrenchment possibilities associated with large shareholders. These hypotheses are tested using a unique sample of 370 mostly private and relatively small Chinese firms in Zhejiang province, for the period 2004 to 2006. The results suggest that for this sample, corporate governance and ownership affect innovation activity when measured by patenting activity, but not when measured by new product sales.
Equivalence classes in the Weyl groups of type Bn
Date: 2008-04-01
Creator: Thomas Pietraho
Access: Open access
- We consider two families of equivalence classes in the Weyl groups of type B n which are suggested by the study of left cells in unequal parameter Iwahori-Hecke algebras. Both families are indexed by a non-negative integer r. It has been shown that the first family coincides with left cells corresponding to the equal parameter Iwahori-Hecke algebra when r=0; the equivalence classes in the second family agree with left cells corresponding to a special class of choices of unequal parameters when r is sufficiently large. Our main result shows that the two families of equivalence classes coincide, suggesting the structure of left cells for remaining choices of the Iwahori-Hecke algebra parameters. © 2007 Springer Science+Business Media, LLC.
Whole genome sequence of the heterozygous clinical isolate Candida krusei 81-B-5
Date: 2017-09-01
Creator: Christina A. Cuomo, Terrance Shea, Bo Yang, Reeta Rao, Anja, Forche
Access: Open access
- Candida krusei is a diploid, heterozygous yeast that is an opportunistic fungal pathogen in immunocompromised patients. This species also is utilized for fermenting cocoa beans during chocolate production. One major concern in the clinical setting is the innate resistance of this species to the most commonly used antifungal drug fluconazole. Here, we report a high-quality genome sequence and assembly for the first clinical isolate of C. krusei, strain 81-B-5, into 11 scaffolds generated with PacBio sequencing technology. Gene annotation and comparative analysis revealed a unique profile of transporters that could play a role in drug resistance or adaptation to different environments. In addition, we show that, while 82% of the genome is highly heterozygous, a 2.0 Mb region of the largest scaffold has undergone loss of heterozygosity. This genome will serve as a reference for further genetic studies of this pathogen.
Higher rank lamplighter groups are graph automatic
Date: 2018-02-15
Creator: Sophie Bérubé, Tara Palnitkar, Jennifer Taback
Access: Open access
- We show that the higher rank lamplighter groups, or Diestel–Leader groups Γd(q) for d≥3, are graph automatic. This introduces a new family of graph automatic groups which are not automatic.