| 1. |
- Acharya, B. S., et al.
(författare)
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Introducing the CTA concept
- 2013
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Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
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| 2. |
- Dahl-Jensen, D., et al.
(författare)
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Eemian interglacial reconstructed from a Greenland folded ice core
- 2013
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 493:7433, s. 489-494
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Tidskriftsartikel (refereegranskat)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.
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| 5. |
- Shore, R. C., et al.
(författare)
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The Structure and Composition of Deciduous Enamel Affected by Local Hypoplastic Autosomal Dominant Amelogenesis Imperfecta Resulting from an ENAM Mutation
- 2010
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Ingår i: Cells Tissues Organs. - : S. Karger. - 1422-6405 .- 1422-6421. ; 191:4, s. 301-306
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Tidskriftsartikel (refereegranskat)abstract
- In a group of families in northern Sweden, a mutation in the ENAM gene (predicted to produce a highly truncated protein) results in the local hypoplastic form of autosomal dominant amelogenesis imperfecta. In this study, sections of deciduous teeth from members of 3 of these families were examined by scanning electron microscopy (SEM) and the enamel mineral was analysed by energy dispersive X-ray spectroscopy (EDX). The sections were also probed with antibodies raised to a conserved sequence of the enamelin protein. Selected intact teeth were first analysed by digital imaging and ascribed with an 'Enamel Defects Index' (EDI) score. SEM of tooth sections revealed disrupted prism morphology and the prisms had a glass-like appearance in some areas. These areas of dysplasia were sometimes irregular but formed regular arrays in others. Comparison of EDI scores with SEM indicated that in one tooth the surface had no measurable defects but significant defects were present in the underlying enamel microstructure. SEM immunohistochemistry with the antibody raised to a fragment of the enamelin protein produced positive, but light, labelling throughout normal enamel. In dysplastic areas, however, the labelling intensity appeared to be reduced. The results indicate that the presence of functional enamelin in the correct amounts is necessary for correct prism morphogenesis. In addition, a combination of EDI and structural analysis indicate that defects in enamel microstructure are not necessarily visible as defects on the surface of the tooth, suggesting the possibility, at least, that some instances of under-diagnosis may occur. Copyright (C) 2009 S. Karger AG, Basel
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| 7. |
- Scott, L., et al.
(författare)
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Terrestrial fossil-pollen evidence of climate change during the last 26 thousand years in Southern Africa
- 2012
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 32, s. 100-118
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Tidskriftsartikel (refereegranskat)abstract
- In order to define criteria for long-term climate change models in Southern Africa, an overview of the available pollen data during the Late Quaternary is needed. Here we reassess the paleo-climatic conditions in southern Africa by synthesising available fossil pollen data that can provide new insights in environmental change processes. The data considered here include the latest as well as previously published information that has been difficult to assess. Available calibrated pollen sequences spanning the Late Pleistocene and Holocene were subjected to Principal Components Analysis (PCA) to monitor taxa sensitive to moisture and temperature fluctuations. The PCA values are presented graphically as indicators of climate variability for the region. The results cover different biomes that include the summer-rain region in the north and east, the winter-rain area in the south and the dry zone in the west. The PCA plots directly reflect major changes of terrestrial environments due to variations in temperature and moisture. Mostly sub-humid but fluctuating conditions are indicated during the cold Marine Isotope Stage (MIS) 2, which were followed by a dry phase soon after the beginning of the Holocene but before the middle Holocene in the northern, central and eastern parts of the sub-continent. Marked but non-parallel moisture changes occurred in different subregions during the Holocene suggesting that climatic forcing was not uniform over the entire region. Some events seemed to have had a more uniform effect over the sub-continent, e.g., a relatively dry summer rain event at c. two thousand years ago, which can possibly be related to the ENSO phenomenon. The role of anthropogenic activities in some of the most recent vegetation shifts is likely.
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