| 1. |
- Berggren, Ann-Marie, 1969-, et al.
(author)
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A 600-year annual 10Be record from the NGRIP ice core, Greenland
- 2009
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 36, s. L11801-
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Journal article (peer-reviewed)abstract
- Despite the extensive use of 10Be as the most significant information source on past solar activity, there has been only one record (Dye-3, Greenland) providing annual resolution over several centuries. Here we report a new annual resolution 10Be record spanning the period 1389-1994 AD, measured in an ice core from the NGRIP site in Greenland. NGRIP and Dye-3 10Be exhibits similar long-term variability, although occasional short term differences between the two sites indicate that at least two high resolution 10Be records are needed to assess local variations and to confidently reconstruct past solar activity. A comparison with sunspot and neutron records confirms that ice core 10Be reflects solar Schwabe cycle variations, and continued 10Be variability suggests cyclic solar activity throughout the Maunder and Spörer grand solar activity minima. Recent 10Be values are low; however, they do not indicate unusually high recent solar activity compared to the last 600 years.
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| 2. |
- Ljung, Karl, et al.
(author)
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Variable Be-10 fluxes in lacustrine sediments from Tristan da Cunha, South Atlantic: a solar record?
- 2007
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 26:7-8, s. 829-835
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Journal article (peer-reviewed)abstract
- A 650-yr-long sediment sequence from a crater lake on Tristan da Cunha, South Atlantic, was analysed for its Be-10 content. Based on C-14 dating, and sedimentary, geochemical, magnetic and palynological records, the period between 900 and 1450 AD appears to have been unusually stable in terms of sedimentation and vegetation and therefore this period was chosen for analysis of the Be-10 content. During this period of highly organic sedimentation and closed vegetation, the pattern of Be-10 flux variations follows the Be-10 fluctuations from the GRIP ice core and estimated C-14 production rates well. However, before and after this stable period, variable sedimentation rates have to be accounted for to obtain results that are comparable to the established Be-10/C-14 records. Our data show not only the possibility of obtaining detailed enough Be-10 flux data from sedimentary sequences to reconstruct past solar forcing but also how sensitive this type of record is to sedimentary and environmental changes. If suitable archives can be found, they have the potential to improve reconstructions of solar activity far back in time. (c) 2007 Elsevier Ltd. All rights reserved.
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| 3. |
- Moschovitis, Giorgio, et al.
(author)
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Heart rate and adverse outcomes in patients with prevalent atrial fibrillation
- 2021
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In: Open Heart. - : BMJ. - 2053-3624. ; 8:1
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Journal article (peer-reviewed)abstract
- OBJECTIVE: The optimal target heart rate in patients with prevalent atrial fibrillation (AF) is not well defined. The aim of this study was to analyse the associations between heart rate and adverse outcomes in a large contemporary cohort of patients with prevalent AF.METHODS: From two prospective cohort studies, we included stable AF outpatients who were in AF on the baseline ECG. The main outcome events assessed during prospective follow-up were heart failure hospitalisation, stroke or systemic embolism and death. The associations between heart rate and adverse outcomes were evaluated using multivariable Cox regression models.RESULTS: The study population consisted of 1679 patients who had prevalent AF at baseline. Mean age was 74 years, and 24.6% were women. The mean heart rate on the baseline ECG was 78 (±19) beats per minute (bpm). The median follow-up was 3.9 years (IQR 2.2-5.0). Heart rate was not significantly associated with heart failure hospitalisation (adjusted HR (aHR) per 10 bpm increase, 1.00, 95% CI 0.94 to 1.07, p=0.95), stroke or systemic embolism (aHR 0.95, 95% CI 0.84 to 1.07, p=0.38) or death (aHR 1.02, 95% CI 0.95 to 1.09, p=0.66). There was no evidence of a threshold effect for heart rates <60 bpm or >100 bpm.CONCLUSIONS: In this large contemporary cohort of outpatients with prevalent AF, we found no association between heart rate and adverse outcome events. These data are in line with recommendations that strict heart rate control is not needed in otherwise stable outpatients with AF.
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| 4. |
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| 5. |
- Muscheler, Raimund, et al.
(author)
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Solar activity during the last 1000 yr inferred from radionuclide records
- 2007
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 26:1-2, s. 82-97
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Journal article (peer-reviewed)abstract
- Identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors-solar forcing. Prior to the period of direct solar observations, radionuclide abundances in natural archives provide the best-known proxies for changes in solar activity. Here we present two independent reconstructions of changes in solar activity during the last 1000 yr, which are inferred from Be-10 and C-14 records. We analyse the tree-ring C-14 data (SHCal, IntCa104 from 1000 to 1510 AD and annual data from 1511 to 1950 AD) and four Be-10 records from Greenland ice cores (Camp Century, GRIP, Milcent and Dye3) together with two Be-10 records from Antarctic ice cores (Dome Concordia and South Pole). In general, the Be-10 and C-14 records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates. Differences between Be-10 records from Antarctica and Greenland indicate that climatic changes have influenced the deposition of Be-10 during some periods of the last 1000 yr. The radionuclide-based reconstructions of past changes in solar activity do not always agree with the sunspot record, which indicates that the coupling between those proxies is not as close as has been sometimes assumed. The tree-ring C-14 record and Be-10 from Antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr. (c) 2006 Elsevier Ltd. All rights reserved.
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| 6. |
- Willerslev, Eske, et al.
(author)
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Ancient biomolecules from deep ice cores reveal a forested Southern Greenland
- 2007
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In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 317:5834, s. 111-114
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Journal article (peer-reviewed)abstract
- It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.
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