Showing 1191 - 1200 of 5831 Items
Holocene peatland carbon dynamics in the circum-Arctic region: An introduction
Date: 2014-01-01
Creator: Zicheng Yu, Julie Loisel, Daniel J. Charman, David W. Beilman, Philip, Camill
Access: Open access
- Peatlands represent the largest and most concentrated carbon pool in the terrestrial biosphere, and their dynamics during the Holocene have had significant impacts on the global carbon cycle. In this Introduction paper, we provide an overview of the contributions presented in this Special Issue on Holocene peatland carbon dynamics. We also provide a brief history and current status of peat-core-based research on peatland carbon dynamics. Finally, we identify and discuss some challenges and opportunities that would guide peatland carbon research in the near future. These challenges and opportunities include the need to fill data gaps and increase geographic representations of peat carbon accumulation records, a better understanding of peatland lateral expansion process and improved estimate of peatland area change over time, developing regional carbon accumulation histories and carbon pool estimates, and projecting and quantifying overall peatland net carbon balance in a changing world.
Midterm Decline in Comparative Perspective
Date: 2019-05-01
Creator: Duncan Gans
Access: Open access
Aneuploidy and isochromosome formation in drug-resistant Candida albicans
Date: 2006-07-21
Creator: Anna Selmecki, Anja Forche, Judith Berman
Access: Open access
- Resistance to the limited number of available antifungal drugs is a serious problem in the treatment of Candida albicans. We found that aneuploidy in general and a specific segmental aneuploidy, consisting of an isochromosome composed of the two left arms of chromosome 5, were associated with azole resistance. The isochromosome forms around a single centromere flanked by an inverted repeat and was found as an independent chromosome or fused at the telomere to a full-length homolog of chromosome 5. Increases and decreases in drug resistance were strongly associated with gain and loss of this isochromosome, which bears genes expressing the enzyme in the ergosterol pathway targeted by azole drugs, efflux pumps, and a transcription factor that positively regulates a subset of efflux pump genes.
Attention training toward and away from threat in social phobia: Effects on subjective, behavioral, and physiological measures of anxiety
Date: 2012-01-01
Creator: Alexandre Heeren, Hannah E. Reese, Richard J. McNally, Pierre Philippot
Access: Open access
- Social phobics exhibit an attentional bias for threat in probe detection and probe discrimination paradigms. Attention training programs, in which probes always replace nonthreatening cues, reduce attentional bias for threat and self-reported social anxiety. However, researchers have seldom included behavioral measures of anxiety reduction, and have never taken physiological measures of anxiety reduction. In the present study, we trained individuals with generalized social phobia (n = 57) to attend to threat cues (attend to threat), to attend to positive cues (attend to positive), or to alternately attend to both (control condition). We assessed not only self-reported social anxiety, but also behavioral and physiological measures of social anxiety. Participants trained to attend to nonthreatening cues demonstrated significantly greater reductions in self-reported, behavioral, and physiological measures of anxiety than did participants from the attend to threat and control conditions. © 2011 Elsevier Ltd.
Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps
Date: 2014-12-01
Creator: G. Hugelius, J. Strauss, S. Zubrzycki, J. W. Harden, E. A.G., Schuur, C. L. Ping, L. Schirrmeister, G. Grosse, G. J. Michaelson, C. D. Koven, J. A. O'Donnell, B. Elberling, U. Mishra, P. Camill, Z. Yu, J. Palmtag
Access: Open access
- Soils and other unconsolidated deposits in the northern circumpolar permafrost region store large amounts of soil organic carbon (SOC). This SOC is potentially vulnerable to remobilization following soil warming and permafrost thaw, but SOC stock estimates were poorly constrained and quantitative error estimates were lacking. This study presents revised estimates of permafrost SOC stocks, including quantitative uncertainty estimates, in the 0-3 m depth range in soils as well as for sediments deeper than 3 m in deltaic deposits of major rivers and in the Yedoma region of Siberia and Alaska. Revised estimates are based on significantly larger databases compared to previous studies. Despite this there is evidence of significant remaining regional data gaps. Estimates remain particularly poorly constrained for soils in the High Arctic region and physiographic regions with thin sedimentary overburden (mountains, highlands and plateaus) as well as for deposits below 3 m depth in deltas and the Yedoma region. While some components of the revised SOC stocks are similar in magnitude to those previously reported for this region, there are substantial differences in other components, including the fraction of perennially frozen SOC. Upscaled based on regional soil maps, estimated permafrost region SOC stocks are 217 ± 12 and 472 ± 27 Pg for the 0-0.3 and 0-1 m soil depths, respectively (±95% confidence intervals). Storage of SOC in 0-3 m of soils is estimated to 1035 ± 150 Pg. Of this, 34 ± 16 Pg C is stored in poorly developed soils of the High Arctic. Based on generalized calculations, storage of SOC below 3 m of surface soils in deltaic alluvium of major Arctic rivers is estimated as 91 ± 52 Pg. In the Yedoma region, estimated SOC stocks below 3 m depth are 181 ± 54 Pg, of which 74 ± 20 Pg is stored in intact Yedoma (late Pleistocene ice- and organic-rich silty sediments) with the remainder in refrozen thermokarst deposits. Total estimated SOC storage for the permafrost region is ∼1300 Pg with an uncertainty range of ∼1100 to 1500 Pg. Of this, ∼500 Pg is in non-permafrost soils, seasonally thawed in the active layer or in deeper taliks, while ∼800 Pg is perennially frozen. This represents a substantial ∼300 Pg lowering of the estimated perennially frozen SOC stock compared to previous estimates.
David Batchelder: Photographs
Date: 1969-01-01
Creator: Richard V. West
Access: Open access
- Catalog of an exhibition held at the Bowdoin College Museum of Art.
Lesley Vance
Date: 2011-01-01
Creator: Diana K. Tuite
Access: Open access
- Catalog of an exhibition held April 12-July 1, 2012, at the Bowdoin College Museum of Art, Brunswick, Maine. Includes essay "Conspiring forms" by Diana Tuite (p. 2-3)
Kernel functions on domains with hyperelliptic double
Date: 1977-01-01
Creator: William H. Barker
Access: Open access
- Iii this paper we show that the structure of the Bergman and Szegö kernel functions is especially simple on domains with hyperelliptic double. Each such domain is conformally equivalent to the exterior of a system of slits taken from the real axis, and on such domains the Bergman kernel function and its adjoint are essentially the same, while the Szegö kernel function and its adjoint are elementary and can be written in a closed form involving nothing worse than fourth roots of polynomials. Additionally, a number of applications of these results are obtained. © 1977 American Mathematical Society.