Faculty Scholarship
Showing 331 - 340 of 733 Items
Multiproxy lake sediment records at the northern and southern boundaries of the Aspen Parkland region of Manitoba, Canada
Date: 2009-09-01
Creator: Rebecca Teed, Charles Umbanhower, Philip Camill
Access: Open access
- Aspen parkland in central Canada may change substantially with increased warming and aridity as prairies replace forests, fire return intervals decrease and lake levels decline. We examined the relationships among vegetation, climate, fire and lake-ecosystem properties using lake sediment cores from the current northern and southern boundaries of the aspen parkland in southwestern Manitoba. We analyzed pollen, charcoal, sediment magnetics, biogenic silica, phosphorus, grain size and LOI, and dated the cores using Pb and C (AMS, calibrated). The Jones Lake record, from the southern edge of the parkland, began considerably earlier (~11 000 cal. BP) than the Mallard Pond record at the northern edge (~8600 cal. BP). These sites were characterized as prairie communities with low fire severity and relatively low lake productivity during the warm, dry period from 9000 to 6000 cal. BP. Beginning around 6500 cal. BP at Jones Lake and 3400 cal. BP at Mallard Pond, conditions appeared to get wetter as indicated by arboreal pollen percentage increases from ~30% to 40-60%, concurrent with a rise in charcoal and proxies for lake productivity (biogenic silica and percent organic phosphorus). Similar to previous studies along the prairie-forest border, we found that charcoal increased during warmer, wetter periods with increased forest cover and fuel loading rather than during warmer, drier periods of prairie dominance. Our results underscore the importance of regional changes in moisture, and its effects on lake levels and forest biomass, as a dominant control of the aspen parkland dynamics. © The Author(s), 2009. 210 14
Flow around phoronids: Consequnces of a neighbor to suspension feeders
Date: 1990-01-01
Creator: Amy S. Johnson
Access: Open access
- This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right. © 1990, by the Association for the Sciences of Limnology and Oceanography, Inc.
The state of cell wall pectin monitored by wall associated kinases: A model
Date: 2015-07-03
Creator: Bruce D. Kohorn
Access: Open access
- The Wall Associated Kinases (WAKs) bind to both cross-linked polymers of pectin in the plant cell wall, but have a higher affinity for smaller fragmented pectins that are generated upon pathogen attack or wounding. WAKs are required for cell expansion during normal seedling development and this involves pectin binding and a signal transduction pathway involving MPK3 and invertase induction. Alternatively WAKs bind pathogen generated pectin fragments to activate a distinct MPK6 dependent stress response. Evidence is provided for a model for how newly generated pectin fragments compete for longer pectins to alter the WAK dependent responses.
The Issue Focus of Online and Television Advertising in the 2016 Presidential Campaign
Date: 2020-01-01
Creator: Michael M. Franz, Erika Franklin Fowler, Travis Ridout, Meredith Yiran Wang
Access: Open access
- Theories of campaign issue emphasis were developed in a pre-digital era. How well do these theories explain spending in the current era, when digital media allow for targeting of specific types of voters? In this research, we compare how the 2016 campaigns, both primary and general election, deployed television advertising with how they deployed online advertising. We suggest that, because online messages are targeted to specific viewer profiles much more than television messages, television ads should be more likely to discuss highly salient issues and valance issues than online ads. To test these ideas, we rely upon data from the Wesleyan Media Project, which tracked all televised political ads that aired in 2016, and our coding of data from Pathmatics, a company that tracks online advertising. We find, contrary to our expectations, that the predictors of issue discussion online and on television are largely similar.
Selection of Candida albicans trisomy during oropharyngeal infection results in a commensal-like phenotype
Date: 2019-05-01
Creator: Anja Forche, Norma V. Solis, Marc Swidergall, Robert Thomas, Alison, Guyer, Annette Beach, Gareth A. Cromie, Giang T. Le, Emily Lowell, Norman Pavelka, Judith Berman, Aimeé M. Dudley, Anna Selmecki, Scott G. Filler
Access: Open access
- When the fungus Candida albicans proliferates in the oropharyngeal cavity during experimental oropharyngeal candidiasis (OPC), it undergoes large-scale genome changes at a much higher frequency than when it grows in vitro. Previously, we identified a specific whole chromosome amplification, trisomy of Chr6 (Chr6x3), that was highly overrepresented among strains recovered from the tongues of mice with OPC. To determine the functional significance of this trisomy, we assessed the virulence of two Chr6 trisomic strains and a Chr5 trisomic strain in the mouse model of OPC. We also analyzed the expression of virulence-associated traits in vitro. All three trisomic strains exhibited characteristics of a commensal during OPC in mice. They achieved the same oral fungal burden as the diploid progenitor strain but caused significantly less weight loss and elicited a significantly lower inflammatory host response. In vitro, all three trisomic strains had reduced capacity to adhere to and invade oral epithelial cells and increased susceptibility to neutrophil killing. Whole genome sequencing of pre- and post-infection isolates found that the trisomies were usually maintained. Most post-infection isolates also contained de novo point mutations, but these were not conserved. While in vitro growth assays did not reveal phenotypes specific to de novo point mutations, they did reveal novel phenotypes specific to each lineage. These data reveal that during OPC, clones that are trisomic for Chr5 or Chr6 are selected and they facilitate a commensal-like phenotype.
Mutation of an Arabidopsis Golgi membrane protein ELMO1 reduces cell adhesion
Date: 2021-05-01
Creator: Bruce D. Kohorn, Frances D.H. Zorensky, Jacob Dexter-Meldrum, Salem Chabout, Gregory, Mouille, Susan Kohorn
Access: Open access
- Plant growth, morphogenesis and development involve cellular adhesion, a process dependent on the composition and structure of the extracellular matrix or cell wall. Pectin in the cell wall is thought to play an essential role in adhesion, and its modification and cleavage are suggested to be highly regulated so as to change adhesive properties. To increase our understanding of plant cell adhesion, a population of ethyl methanesulfonate-mutagenized Arabidopsis were screened for hypocotyl adhesion defects using the pectin binding dye Ruthenium Red that penetrates defective but not wild-type (WT) hypocotyl cell walls. Genomic sequencing was used to identify a mutant allele of ELMO1 which encodes a 20 kDa Golgi membrane protein that has no predicted enzymatic domains. ELMO1 colocalizes with several Golgi markers and elmo1-/- plants can be rescued by an ELMO1-GFP fusion. elmo1-/- exhibits reduced mannose content relative to WT but no other cell wall changes and can be rescued to WT phenotype by mutants in ESMERALDA1, which also suppresses other adhesion mutants. elmo1 describes a previously unidentified role for the ELMO1 protein in plant cell adhesion.
Polar firn air reveals large-scale impact of anthropogenic mercury emissions during the 1970s
Date: 2009-09-22
Creator: Xavier Faïn, Christophe P. Ferrari, Aurélien Dommergue, Mary R. Albert, Mark, Battle, Jeff Severinghaus, Laurent Arnaud, Jean Marc Barnola, Warren Cairns, Carlo Barbante, Claude Boutron
Access: Open access
- Mercury (Hg) is an extremely toxic pollutant, and its biogeochemical cycle has been perturbed by anthropogenic emissions during recent centuries. In the atmosphere, gaseous elemental mercury (GEM; Hg°) is the predominant form of mercury (up to 95%). Here we report the evolution of atmospheric levels of GEM in mid- to high-northern latitudes inferred from the interstitial air of firn (perennial snowpack) at Summit, Greenland. GEM concentrations increased rapidly after World War II from ≈1.5 ng m-3 reaching a maximum of ≈3 ng m-3 around 1970 and decreased until stabilizing at ≈1.7 ng m -3 around 1995. This reconstruction reproduces real-time measurements available from the Arctic since 1995 and exhibits the same general trend observed in Europe since 1990. Anthropogenic emissions caused a two-fold rise in boreal atmospheric GEM concentrations before the 1970s, which likely contributed to higher deposition of mercury in both industrialized and remotes areas. Once deposited, this toxin becomes available for methylation and, subsequently, the contamination of ecosystems. Implementation of air pollution regulations, however, enabled a large-scale decline in atmospheric mercury levels during the 1980s. The results shown here suggest that potential increases in emissions in the coming decades could have a similar large-scale impact on atmospheric Hg levels.
A new data set for estimating organic carbon storage to 3 m depth in soils of the northern circumpolar permafrost region
Date: 2013-12-23
Creator: G. Hugelius, J. G. Bockheim, P. Camill, B. Elberling, G., Grosse, J. W. Harden, K. Johnson, T. Jorgenson, C. D. Koven, P. Kuhry, G. Michaelson, U. Mishra, J. Palmtag, J. O'Donnell, L. Schirrmeister, E. A.G. Schuur
Access: Open access
- High-latitude terrestrial ecosystems are key components in the global carbon cycle. The Northern Circumpolar Soil Carbon Database (NCSCD) was developed to quantify stocks of soil organic carbon (SOC) in the northern circumpolar permafrost region (a total area of 18.7 × 106 km2). The NCSCD is a geographical information system (GIS) data set that has been constructed using harmonized regional soil classification maps together with pedon data from the northern permafrost region. Previously, the NCSCD has been used to calculate SOC storage to the reference depths 0–30 cm and 0–100 cm (based on 1778 pedons). It has been shown that soils of the northern circumpolar permafrost region also contain significant quantities of SOC in the 100–300 cm depth range, but there has been no circumpolar compilation of pedon data to quantify this deeper SOC pool and there are no spatially distributed estimates of SOC storage below 100 cm depth in this region. Here we describe the synthesis of an updated pedon data set for SOC storage (kg C m−2) in deep soils of the northern circumpolar permafrost regions, with separate data sets for the 100–200 cm (524 pedons) and 200–300 cm (356 pedons) depth ranges. These pedons have been grouped into the North American and Eurasian sectors and the mean SOC storage for different soil taxa (subdivided into Gelisols including the sub-orders Histels, Turbels, Orthels, permafrost-free Histosols, and permafrost-free mineral soil orders) has been added to the updated NCSCDv2. The updated version of the data set is freely available online in different file formats and spatial resolutions that enable spatially explicit applications in GIS mapping and terrestrial ecosystem models. While this newly compiled data set adds to our knowledge of SOC in the 100–300 cm depth range, it also reveals that large uncertainties remain. Identified data gaps include spatial coverage of deep (> 100 cm) pedons in many regions as well as the spatial extent of areas with thin soils overlying bedrock and the quantity and distribution of massive ground ice.©Author(s) 2013.
Sponsorship, Disclosure, and Donors: Limiting the Impact of Outside Group Ads
Date: 2015-03-25
Creator: Travis N. Ridout, Michael M. Franz, Erika Franklin Fowler
Access: Open access
- This research examines how an attack ad’s sponsorship conditions its effectiveness. We use data from a survey experiment that exposed participants to a fictional campaign ad. Treatments varied the ad’s sponsor (candidate vs. group), the group’s donor base (small donor vs. large donors), and the format of the donor disclosure (news reports vs. disclaimers in the ads). We find that ads sponsored by unknown groups are more effective than candidate-sponsored ads, but disclosure of donors reduces the influence of group advertising, leveling the playing field such that candidate- and group-sponsored attacks become equally effective. Increased disclosure does not, however, advantage small-donor groups over large-donor groups.
MAO-A phenotype effects response sensitivity and the parietal old/new effect during recognition memory
Date: 2018-02-13
Creator: Robert S. Ross, Andrew Smolen, Tim Curran, Erika Nyhus
Access: Open access
- A critical problem for developing personalized treatment plans for cognitive disruptions is the lack of understanding how individual differences influence cognition. Recognition memory is one cognitive ability that varies from person to person and that variation may be related to different genetic phenotypes. One gene that may impact recognition memory is the monoamine oxidase A gene (MAO-A), which influences the transcription rate of MAO-A. Examination of how MAO-A phenotypes impact behavioral and event-related potentials (ERPs) correlates of recognition memory may help explain individual differences in recognition memory performance. Therefore, the current study uses electroencephalography (EEG) in combination with genetic phenotyping of the MAO-A gene to determine how well-characterized ERP components of recognition memory, the early frontal old/new effect, left parietal old/new effect, late frontal old/new effect, and the late posterior negativity (LPN) are impacted by MAO-A phenotype during item and source memory. Our results show that individuals with the MAO-A phenotype leading to increased transcription have lower response sensitivity during both item and source memory. Additionally, during item memory the left parietal old/new effect is not present due to increased ERP amplitude for correct rejections. The results suggest that MAO-A phenotype changes EEG correlates of recognition memory and influences how well individuals differentiate between old and new items.