Showing 2591 - 2600 of 5708 Items
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.
Collecting for a College: Gifts from David P. Becker
Date: 1995-01-01
Creator: Marjorie B. Cohen
Access: Open access
- Catalog of an exhibition held at the Bowdoin College Museum of Art Apr. 20-June 4, 1995.
Characterization of negative phonotactic behavior in the adult cricket, Gryllus bimaculatus Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: Julianne Scholes
Access: Access restricted to the Bowdoin Community
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.
Statement by James Tierney collected by Heather Westleigh on November 19, 2014
Date: 2014-11-19
Creator: James Tierney
Access: Audio recording permanently restricted
IR divergences and Regge limits of subleading-color contributions to the four-gluon amplitude in N=4 SYM theory
Date: 2009-11-11
Creator: Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- We derive a compact all-loop-order expression for the IR-divergent part of the = 4 SYM four-gluon amplitude, which includes both planar and all subleading-color contributions, based on the assumption that the higher-loop soft anomalous dimension matrices are proportional to the one-loop soft anomalous dimension matrix, as has been recently conjectured. We also consider the Regge limit of the four-gluon amplitude, and we present evidence that the leading logarithmic growth of the subleading-color amplitudes is less severe than that of the planar amplitudes. We examine possible 1/N 2 corrections to the gluon Regge trajectory, previously obtained in the planar limit from the BDS ansatz. The double-trace amplitudes have Regge behavior as well, with a nonsense-choosing Regge trajectory and a Regge cut which first emerges at three loops. © SISSA 2009.
Semantic and perceptual effects on recognition memory: Evidence from ERP
Date: 2009-08-04
Creator: Erika Nyhus, Tim Curran
Access: Open access
- The present experiments examined how semantic vs. perceptual encoding and perceptual match affect the processes involved in recognition memory. Experiment 1 examined the effects of encoding task and perceptual match between study and test fonts on recognition discrimination for words. Font fan was used to determine the effect of distinctiveness on perceptual match. The semantic encoding task and perceptual match for distinctive items led to better recognition memory. Event-related brain potentials (ERPs) recorded from the human scalp during recognition memory experiments have revealed differences between old (studied) and new (not studied) items that are thought to reflect the activity of memory-related brain processes. In Experiment 2, the semantic encoding task and perceptual match for distinctive words led to better recognition memory by acting on both familiarity and recollection processes, as purportedly indexed by the FN400 and parietal old/new effects. Combined these results suggest that the semantic encoding task and perceptual match for distinctive items aid recognition memory by acting on both familiarity and recollection processes. © 2009 Elsevier B.V. All rights reserved.
Regge behavior of gluon scattering amplitudes in N = 4 SYM theory
Date: 2008-05-01
Creator: Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- It is shown that the four-gluon scattering amplitude for N = 4 supersymmetric Yang-Mills theory in the planar limit can be written, in both the weak- and strong-coupling limits, as a reggeized amplitude, with a parent trajectory and an infinite number of daughter trajectories. This result is not evident a priori, and relies crucially on the fact that the leading IR-divergence and the finite log2 (s / t)-dependent piece of the amplitude are characterized by the same function for all values of the coupling, as conjectured by Bern, Dixon, and Smirnov, and proved by Alday and Maldacena in the strong-coupling limit. We use the Alday-Maldacena result to determine the exact strong-coupling Regge trajectory. © 2007 Elsevier B.V. All rights reserved.
Rapid phenotypic and genotypic diversification after exposure to the oral host niche in candida albicans
Date: 2018-07-01
Creator: Anja Forche, Gareth Cromie, Aleeza C. Gerstein, Norma V. Solis, Tippapha, Pisithkul, Waracharee Srifa, Eric Jeffery, Darren Abbey, Scott G. Filler, Aimée M. Dudley, Judith Berman
Access: Open access
- In vitro studies suggest that stress may generate random standing variation and that different cellular and ploidy states may evolve more rapidly under stress. Yet this idea has not been tested with pathogenic fungi growing within their host niche in vivo. Here, we analyzed the generation of both genotypic and phenotypic diversity during exposure of Candida albicans to the mouse oral cavity. Ploidy, aneuploidy, loss of heterozygosity (LOH), and recombination were determined using flow cytometry and double digest restriction site-associated DNA sequencing. Colony phenotypic changes in size and filamentous growth were evident without selection and were enriched among colonies selected for LOH of the GAL1 marker. Aneuploidy and LOH occurred on all chromosomes (Chrs), with aneuploidy more frequent for smaller Chrs and whole Chr LOH more frequent for larger Chrs. Large genome shifts in ploidy to haploidy often maintained one or more heterozygous disomic Chrs, consistent with random Chr missegregation events. Most isolates displayed several different types of genomic changes, suggesting that the oral environment rapidly generates diversity de novo. In sharp contrast, following in vitro propagation, isolates were not enriched for multiple LOH events, except in those that underwent haploidization and/or had high levels of Chr loss. The frequency of events was overall 100 times higher for C. albicans populations following in vivo passage compared with in vitro. These hyper-diverse in vivo isolates likely provide C. albicans with the ability to adapt rapidly to the diversity of stress environments it encounters inside the host.