| 1. |
- Actis, M., et al.
(author)
-
Design concepts for the Cherenkov Telescope Array CTA : an advanced facility for ground-based high-energy gamma-ray astronomy
- 2011
-
In: Experimental astronomy. - : Springer. - 0922-6435 .- 1572-9508. ; 32:3, s. 193-316
-
Journal article (peer-reviewed)abstract
- Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.
|
|
| 2. |
|
|
| 3. |
- Dahl-Jensen, D., et al.
(author)
-
Eemian interglacial reconstructed from a Greenland folded ice core
- 2013
-
In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 493:7433, s. 489-494
-
Journal article (peer-reviewed)abstract
- Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.
|
|
| 4. |
- Dahlqvist, Johanna, 1979-, et al.
(author)
-
Identification and functional characterization of a novel susceptibility locus for small vessel vasculitis with MPO-ANCA
- 2022
-
In: Rheumatology. - Oxford, United Kingdom : Oxford University Press (OUP). - 1462-0324 .- 1462-0332. ; 61:8
-
Journal article (peer-reviewed)abstract
- Objective To identify and characterize genetic loci associated with the risk of developing ANCA-associated vasculitides (AAV). Methods Genetic association analyses were performed after Illumina sequencing of 1853 genes and subsequent replication with genotyping of selected single nucleotide polymorphisms in a total cohort of 1110 Scandinavian cases with granulomatosis with polyangiitis or microscopic polyangiitis, and 1589 controls. A novel AAV-associated single nucleotide polymorphism was analysed for allele-specific effects on gene expression using luciferase reporter assay. Results PR3-ANCA(+) AAV was significantly associated with two independent loci in the HLA-DPB1/HLA-DPA1 region [rs1042335, P = 6.3 x 10(-61), odds ratio (OR) 0.10; rs9277341, P = 1.5 x 10(-44), OR 0.22] and with rs28929474 in the SERPINA1 gene (P = 2.7 x 10(-10), OR 2.9). MPO-ANCA(+) AAV was significantly associated with the HLA-DQB1/HLA-DQA2 locus (rs9274619, P = 5.4 x 10(-25), OR 3.7) and with a rare variant in the BACH2 gene (rs78275221, P = 7.9 x 10(-7), OR 3.0), the latter a novel susceptibility locus for MPO-ANCA(+) granulomatosis with polyangiitis/microscopic polyangiitis. The rs78275221-A risk allele reduced luciferase gene expression in endothelial cells, specifically, as compared with the non-risk allele. Conclusion We identified a novel susceptibility locus for MPO-ANCA(+) AAV and propose that the associated variant is of mechanistic importance, exerting a regulatory function on gene expression in specific cell types.
|
|
| 5. |
- Duplessis, P., et al.
(author)
-
Highly Hygroscopic Aerosols Facilitate Summer and Early-Autumn Cloud Formation at Extremely Low Concentrations Over the Central Arctic Ocean
- 2024
-
In: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 129:2
-
Journal article (peer-reviewed)abstract
- Arctic clouds are sensitive to atmospheric particles since these are sometimes in such low concentrations that clouds cannot always form under supersaturated water vapor conditions. This is especially true in the late summer, when aerosol concentrations are generally very low in the high Arctic. The environment changes rapidly around freeze-up as the open waters close and snow starts accumulating on ice. We investigated droplet formation during eight significant fog events in the central Arctic Ocean, north of 80 degrees, from August 12 to 19 September 2018 during the Arctic Ocean 2018 expedition onboard the icebreaker Oden. Calculated hygroscopicity parameters (kappa) for the entire study were very high (up to kappa = 0.85 +/- 0.13), notably after freeze-up, suggesting that atmospheric particles were very cloud condensation nuclei (CCN)-active. At least one of the events showed that surface clouds were able to form and persist for at least a couple hours at aerosol concentrations less than 10 cm-3, which was previously suggested to be the minimum for cloud formation. Among these events that were considered limited in CCN, effective radii were generally larger than in the high CCN cases. In some of the fog events, droplet residuals particles did not reactivate under supersaturations up to 0.95%, suggesting either in-droplet reactions decreased hygroscopicity, or an ambient supersaturation above 1%. These results provide insight into droplet formation during the clean late-summer and fall of the high Arctic with limited influence from continental sources. The Arctic atmosphere can be very clean in the summer, to the point that clouds cannot form because there are insufficient particles present for the water vapor to condense upon. This has important implications for the radiation budget, which is highly dependent on clouds. As part of the Arctic Ocean 2018 expedition in the central Arctic Ocean near the North Pole, we investigated the ability of particles to turn into droplets throughout the whole cruise (August 12 to 19 September 2018), and during eight significant fog events. Overall, we found that after the sea ice started to freeze, the particles were more capable of turning into cloud droplets. During one fog event, we observed fog droplets forming when the particle concentrations were lower than the limit that past studies had suggested that fog/cloud could be sustained. During several fog events, the dried fog droplets did not always re-form droplets when exposed to cloud-like conditions, which suggests that the original droplets must have formed under extreme conditions. Our results show that in the summer/fall in the high Arctic, liquid droplets sometimes form under unusual circumstances that are likely not always considered in models. Aerosol hygroscopicity was greater after surface water freeze-up than beforeHygroscopicity of Aitken mode particles was generally greater than accumulation mode particlesCloud droplet effective radii during aerosol-limited periods were larger generally than periods with higher aerosol concentrations
|
|
| 6. |
- Lundin, Erik J, et al.
(author)
-
Is the subarctic landscape still a carbon sink? : Evidence from a detailed catchment balance
- 2016
-
In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 43:5, s. 1988-1995
-
Journal article (peer-reviewed)abstract
- Climate warming raises the question whether high-latitude landscape still function as net carbon (C) sinks. By compiling an integrated C balance for an intensely studied subarctic catchment, we show that this catchment's C balance is not likely to be a strong current sink of C, a commonly held assumption. In fact, it is more plausible (71% probability) that the studied catchment functions as a C source (-1120gCm(-2)yr(-1)). Analyses of individual fluxes indicate that soil and aquatic C losses offset C sequestering in other landscape components (e.g., peatlands and aboveground forest biomass). Our results stress the importance of fully integrated catchment C balance estimates and highlight the importance of upland soils and their interaction with the aquatic network for the catchment C balance.
|
|
