| 1. |
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| 2. |
- de Jong, R. S., et al.
(author)
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4MOST : Project overview and information for the First Call for Proposals
- 2019
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In: The Messenger. - : European Southern Observatory. - 0722-6691. ; 175, s. 3-11
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Journal article (other academic/artistic)abstract
- We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (R = λ/Δλ ~ 6500), and 812 fibres transferring light to the high-resolution spectrograph (R ~ 20 000). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations.
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| 4. |
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| 5. |
- Sigmundsson, F., et al.
(author)
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Segmented lateral dyke growth in a rifting event at Bardarbunga volcanic system, Iceland
- 2015
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 517:7533
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Journal article (peer-reviewed)abstract
- Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long(1). Previous models of rifting events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens(2-4), or magma flowing vertically into dykes from an underlying source(5,6), with the role of topography on the evolution of lateral dykes not clear. Here we show how a recent segmented dyke intrusion in the Bardarbunga volcanic system grew laterally for more than 45 kilometres at a variable rate, with topography influencing the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred primarily over 14 days, was revealed by propagating seismicity, ground deformation mapped by Global Positioning System(GPS), interferometric analysis of satellite radar images (InSAR), and graben formation. The strike of the dyke segments varies from an initially radial direction away from the Bardarbunga caldera, towards alignment with that expected from regional stress at the distal end. A model minimizing the combined strain and gravitational potential energy explains the propagation path. Dyke opening and seismicity focused at the most distal segment at any given time, and were simultaneous with magma source deflation and slow collapse at the Bardarbunga caldera, accompanied by a series of magnitude M > 5 earthquakes. Dyke growth was slowed down by an effusive fissure eruption near the end of the dyke. Lateral dyke growth with segment barrier breaking by pressure build-up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries.
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| 6. |
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| 7. |
- Gumaelius, Lena, et al.
(author)
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Outreach initiatives operated by universities for increasing interest in science and technology
- 2016
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In: European Journal of Engineering Education. - : Taylor & Francis Group. - 0304-3797 .- 1469-5898. ; , s. 1-34
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Journal article (peer-reviewed)abstract
- Since the 1990s, the low number of students choosing to study science and technology in higher education has been on the societal agenda and many initiatives have been launched to promote awareness regarding career options. The initiatives particularly focus on increasing enrolment in the engineering programmes. This article describes and compares eight European initiatives that have been established and operated by universities (and in some cases through collaboration with other actors in society). Each initiative is summarised in a short essay that discusses motivation, organisation, pedagogical approach, and activities. The initiatives are characterised by comparing the driving forces behind their creation, how the initiative activities relate to the activities at the university, size based on the number of participants and cost per participant and pedagogical framework. There seem to be two main tracks for building outreach activities, one where outreach activities are based on the university's normal activities, and one where outreach activities are designed specifically for the visiting students.
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| 8. |
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| 11. |
- Hreinsdottir, S., et al.
(author)
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Volcanic plume height correlated with magma-pressure change at Grimsvotn Volcano, Iceland
- 2014
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In: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 7:3, s. 214-218
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Journal article (peer-reviewed)abstract
- Magma flow during volcanic eruptions causes surface deformation that can be used to constrain the location, geometry and internal pressure evolution of the underlying magmatic source(1). The height of the volcanic plumes during explosive eruptions also varies with magma flow rate, in a nonlinear way(2,3). In May 2011, an explosive eruption at Grimsvotn Volcano, Iceland, erupted about 0.27 km(3) dense-rock equivalent of basaltic magma in an eruption plume that was about 20 km high. Here we use Global Positioning System (GPS) and tilt data, measured before and during the eruption at Grimsvotn Volcano, to show that the rate of pressure change in an underlying magma chamber correlates with the height of the volcanic plume over the course of the eruption. We interpret ground deformation of the volcano, measured by geodesy, to result from a pressure drop within a magma chamber at about 1.7 km depth. We estimate the rate of magma discharge and the associated evolution of the plume height by differentiating the co-eruptive pressure drop with time. The time from the initiation of the pressure drop to the onset of the eruption was about 60 min, with about 25% of the total pressure change preceding the eruption. Near-real-time geodetic observations can thus be useful for both timely eruption warnings and for constraining the evolution of volcanic plumes.
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| 12. |
- Sigmundsson, F., et al.
(author)
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Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption
- 2010
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In: Nature. ; 468:7322, s. 426-430
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Journal article (peer-reviewed)abstract
- Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During such eruptions, rapid deflation occurs as magma flows out and pressure is reduced1–3. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallajo¨kull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic, closing airspace over much of Europe for days. This eruption was preceded by an effusive flank eruption of basalt from 20 March to 12 April 2010. The 2010 eruptions are the culmination of 18 years of intermittent volcanic unrest4–9. Here we show that deformation associated with the eruptions was unusual because it did not relate to pressure changes within a single magma chamber. Deformation was rapid before the first eruption (.5mm per day after 4 March), but negligible during it. Lack of distinct co-eruptive deflation indicates that the net volume of magma drained from shallow depth during this eruption was small; rather, magma flowed from considerable depth. Before the eruption, a 0.05km3 magmatic intrusion grew over a period of three months, in a temporally and spatially complex manner, as revealed by GPS (Global Positioning System) geodetic measurements and interferometric analysis of satellite radar images. The second eruption occurred within the ice-capped caldera of the volcano, with explosivity amplified by magma–ice interaction. Gradual contraction of a source, distinct from the pre-eruptive inflation sources, is evident from geodetic data. Eyjafjallajo¨kull’s behaviour can be attributed to its off-rift setting with a ‘cold’ subsurface structure and limited magma at shallow depth, as may be typical for moderately active volcanoes. Clear signs of volcanic unrest signals over years to weeks may indicate reawakening of such volcanoes, whereas immediate short-term eruption precursors may be subtle and difficult to detect.
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| 14. |
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| 15. |
- Arnadottir, M, et al.
(author)
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The effect of reduced glomerular filtration rate on plasma total homocysteine concentration
- 1996
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In: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 56:1, s. 41-46
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Journal article (peer-reviewed)abstract
- The concentration of homocysteine in plasma has been shown to be increased in renal failure, possibly contributing to the accelerated atherosclerosis observed in uraemic patients. The aim of the present study was to document the relationship between plasma total homocysteine (tHcy) concentrations and glomerular filtration rates (GFR) in highly selected patients, with renal function ranging from normal to dialysis dependency. GFR was defined as the plasma clearance of iohexol; a more accurate method than the creatinine-based estimations applied in previous studies. Plasma tHcy concentrations were highly correlated to GFR (r = -0.70, p < 0.0001) and were significantly increased already in moderate renal failure. According to a multiple regression analysis, GFR and red cell folate concentrations independently predicted plasma tHcy concentrations, whereas those of serum creatinine, plasma pyridoxal-5-phosphate, urine albumin and urine alpha-1-microglobulin (a marker of tubular damage) did not. Thus, GFR seems to be a better determinant of plasma tHcy concentration than serum creatinine concentration. Plasma total cysteine and total cysteinylglycine concentrations followed the same pattern as those of tHcy.
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| 16. |
- Arnadottir, M, et al.
(author)
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The effect of vitamin B-12 on total plasma homocysteine concentration in folate-replete hemodialysis patients
- 2003
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In: Clinical Nephrology. - 0301-0430. ; 59:3, s. 186-189
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Journal article (peer-reviewed)abstract
- Aim: Results from several studies indicate that the total homocysteine (tHcy) concentration in plasma is an independent risk factor for cardiovascular disease in hemodialysis patients. Folic acid is the established mainstay of homocysteine-lowering treatment, but since such treatment does not normalize plasma tHcy concentration in hemodialysis patients, it is of importance to search for additional therapy. Methods: Twenty-eight folate-replete hemodialysis patients were randomized to 2 equally sized groups, a treatment group and a control group. The treatment group received vitamin B 12 tablets at a dose of 2 mg 3 times a week for 6 weeks (after each dialysis session) while the control group received no such treatment. Blood samples were collected before and at the end of the treatment period for analysis of tHcy in plasma and vitamin B-12, methylmalonic acid as well as folate in serum. Results: At the end of the study period, serum vitamin B12 concentrations were significantly higher in the treatment group than in the control group. Plasma tHcy concentrations decreased significantly in both groups during the study period. However, there was no difference between the responses of the 2 groups. Conclusion: The results of this open, randomized controlled study did not support the hypothesis that treatment with oral vitamin B12 has considerable homocysteine-lowering effect in folate-replete hemodialysis patients.
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| 17. |
- Arnadottir, Solveig, 1968-
(author)
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Physical activity, participation and self-rated health among older community-dwelling Icelanders : a population-based study
- 2010
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Doctoral thesis (other academic/artistic)abstract
- Background: The main objective of this study was to investigate older people’s physical activity, their participation in various life situations, and their perceptions of their own health. This included an exploration of potential influences of urban versus rural residency on these outcomes, an evaluation of the measurement properties of a balance confidence scale, and an examination of the proposed usefulness of the International Classification of Functioning, Disability and Health (ICF) as a conceptual framework to facilitate analysis and understanding of selected outcomes.Methods: The study design was cross-sectional, population-based, with random selection from the national register of one urban and two rural municipalities in Northern Iceland. There were 186 participants, all community-dwelling, aged 65 to 88 years (mean = 73.8), and 48% of the group were women. The participation rate was 79%. Data was collected in 2004, in face-to-face interviews and through various standardized assessments. The main outcomes were total physical activity; leisure-time, household, and work-related physical activity; participation frequency and perceived participation restrictions; and self-rated health. Other assessments represented aspects of the ICF body functions, activities, environmental factors and personal factors. Moreover, Rasch analysis methods were applied to examine and modify the Activities-specific Balance Confidence (ABC) scale and the ICF used as a conceptual framework throughout the study.Results: The total physical activity score was the same for urban and rural people and the largest proportion of the total physical activity behavior was derived from the household domain. Rural females received the highest scores of all in household physical activity and rural males were more physically active than the others in the work-related domain. However, leisure-time physical activity was more common in urban than rural communities. A physically active lifestyle, urban living, a higher level of cognition, younger age, and fewer depressive symptoms were all associated with more frequent participation. Rural living and depressive symptoms were associated with perceived participation restrictions. Moreover, perceived participation restrictions were associated with not being employed and limitations in advanced lower extremity capacity. Both fewer depressive symptoms and advanced lower extremity capacity also increased the likelihood of better self-rated health, as did capacity in upper extremities, older age, and household physical activity. Rasch rating scale analysis indicated a need to modify the ABC to improve its psychometric properties. The modified ABC was then used to measure balance confidence which, however, was found not to play a major role in explaining participation or self-rated health. Finally, the ICF was useful as a conceptual framework for mapping various components of functioning and health and to facilitate analyses of their relationships.Conclusions: The results highlighted the commonalities and differences in factors associated with participation frequency, perceived participation restrictions, and self-rated health in old age. Some of these factors, such as advanced lower extremity capacity, depressive symptoms, and physical activity pattern should be of particular interest for geriatric physical therapy due to their potential for interventions. While the associations between depressive symptoms, participation, and self-rated health are well known, research is needed on the effects of advanced lower extremity capacity on participation and self-rated health in old age. The environment (urban versus rural) also presented itself as an important contextual variable to be aware of when working with older people’s participation and physically active life-style. Greater emphasis should be placed on using Rasch measurement methods for improving the availability of quality scientific measures to evaluate various aspects of functioning and health among older adults. Finally, a coordinated implementation of a conceptual framework such as ICF may further advance interdisciplinary and international studies on aging, functioning, and health.
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| 18. |
- Berg, Anna-Lena, et al.
(author)
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Beneficial effects of ACTH on the serum lipoprotein profile and glomerular function in patients with membranous nephropathy
- 1999
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In: Kidney International. - : Elsevier BV. - 1523-1755 .- 0085-2538. ; 56:4, s. 1534-1543
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Journal article (peer-reviewed)abstract
- BACKGROUND: Previous studies have shown that short-term treatment with adrenocorticotrophic hormone (ACTH) has a strong and rapid lipid-lowering effect. In this long-term study of nephrotic patients with idiopathic membranous nephropathy, the influence of ACTH on the serum lipoprotein profile and glomerular function as well as the dose-effect relationship was investigated. METHODS: Fourteen patients received ACTH intramuscularly at increasing doses during 56 days. Serum concentrations of lipids, lipoproteins, and apolipoproteins as well as variables of glomerular function were analyzed, and the side-effects were recorded. ACTH treatment, in the estimated optimal dosage, was then continued in five patients with severe steroid-resistant nephrotic syndrome. In these five patients, the total treatment period was 12 months, and the follow-up time after discontinuing treatment was 18 months. RESULTS: Taking both the statistically significant therapeutic effects and the modest side-effects into consideration, the optimal dosage of ACTH was estimated to be 1 mg twice per week. At that dose, reductions by 30 to 60% in the serum concentrations of cholesterol, triglycerides, apolipoprotein B, and lipoprotein(a) were observed, whereas the serum concentrations of high-density lipoprotein cholesterol and apolipoprotein AI rose by 30 to 40%. In addition, the urinary albumin excretion decreased by 90%, and the glomerular filtration rate increased by 25%. Deterioration was observed in all cases when ACTH was discontinued after a treatment duration of 56 days. However, the five patients in whom ACTH therapy was resumed were still in remission 18 months after discontinuance of treatment. CONCLUSIONS: In nephrotic patients with idiopathic membranous nephropathy, treatment with ACTH 1 mg twice per week was associated with significant long-term improvements in serum lipoprotein pattern and glomerular function.
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| 19. |
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| 20. |
- Geirsson, H., et al.
(author)
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Overview of results from continuous GPS observations in Iceland from 1995 to 2010
- 2010
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In: Jökull. - 0449-0576. ; 60:1, s. 1-21
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Journal article (peer-reviewed)abstract
- Iceland is a natural laboratory for a variety of processes associated with crustal deformation, such as earthquakes, magmatic events, tectonic plate motions, and glacial load changes. Continuous GPS (CGPS) measurements started in Iceland in 1995, and since then data from the network have helped to shed light on many different active deformation processes. The number of CGPS sites in Iceland tripled during 2006–2008, as a result of an international collaborative effort coordinated by Icelandic scientists. By early 2010 the number of CGPS stations in Iceland had reached 64, located primarily around and within the North- American–Eurasian plate boundary zone. Since its initiation, the CGPS network has played an important role in monitoring volcanoes and seismogenic areas, most notably during the 2009–2010 Eyjafjallajökull volcano unrest. Plate spreading of up to 2 cm per year usually dominates the horizontal motion observed at the CGPS sites, while uplift is observed at many of the stations due to recent retreat of the Icelandic ice caps. Co-seismic and post-seismic deformation of the largest earthquakes in 2000 and 2008 in the South Iceland Seismic Zone were captured by the network, and high-rate (1 Hz) CGPS observations helped to identify two magnitude 6 mainshocks in 2008 that were separated in time by only 2–3 seconds. The CGPS network has thus enabled us to monitor deformation occurring over days to months caused by migration of magma or fluids, post-seismic transients, rapid deformation caused by earthquakes and eruptions, as well as the long term plate spreading signal.
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| 21. |
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| 22. |
- Keiding, M, et al.
(author)
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Earthquakes, stress, and strain along an obliquely divergent plate boundary : Reykjanes Peninsula, southwest Iceland
- 2009
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202 .- 2169-9313 .- 2169-9356. ; 114, s. B09306-
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Journal article (peer-reviewed)abstract
- We investigate the seismicity and the state of stress along the obliquely divergent Reykjanes Peninsula plate boundary and compare the directions of stress from inversion of earthquake focal mechanisms with the directions of strain rate from GPS data. The seismicity on the peninsula since early instrumental recordings in 1926 shows a systematic change from primarily earthquake swarms in the west to main shock-aftershock sequences in the east. The largest earthquakes on the Reykjanes Peninsula typically occur by right-lateral slip on N-S faults and reach magnitude 6 on the eastern part of the peninsula. During 1997-2006 most earthquakes on the Reykjanes Peninsula were located in two areas, Fagradalsfjall and Krisuvik on the central part of the peninsula, as recorded by the South Iceland Lowland (SIL) seismic network. The state of stress estimated by inversion of microearthquake focal mechanisms from the SIL catalogue is mainly oblique strike slip, with a tendency toward a normal stress state. Mapping the directions of the least compressive horizontal stress (S-hmin) shows an average Shmin direction of N(120 +/- 6)degrees E and a remarkable agreement with the directions of greatest extensional strain rate ((epsilon) over dot(Hmax)) derived from GPS velocities during 2000-2006. The agreement between the directions of stress at depth and strain rate observed at the surface indicate that the earthquakes are primarily driven by plate motion.
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| 23. |
- Keiding, M., et al.
(author)
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Strain accumulation along an oblique plate boundary : the Reykjanes Peninsula, southwest Iceland
- 2008
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In: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 172:2, s. 861-872
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Journal article (peer-reviewed)abstract
- We use annual GPS observations on the Reykjanes Peninsula (RP) from 2000 to 2006 to generate maps of surface velocities and strain rates across the active plate boundary. We find that the surface deformation on the RP is consistent with oblique plate boundary motion on a regional scale, although considerable temporal and spatial strain rate variations are observed within the plate boundary zone. A small, but consistent increase in eastward velocity is observed at several stations on the southern part of the peninsula, compared to the 1993-1998 time period. The 2000-2006 velocities can be modelled by approximating the plate boundary as a series of vertical dislocations with left-lateral motion and opening. For the RP plate boundary we estimate left-lateral motion 18(-3)(+4) mm yr(-1) and opening of 7(-2)(+3) mm yr(-1) below a locking depth of 7(-2)(+1) km. The resulting deep motion of 20(-3)(+4) mm yr(-1) in the direction of N(100(-6)(+8))degrees E agrees well with the predicted relative North America-Eurasia rate. We calculate the areal and shear strain rates using velocities from two periods: 1993-1998 and 2000-2006. The deep motion along the plate boundary results in left-lateral shear strain rates, which are perturbed by shallow deformation due to the 1994-1998 inflation and elevated seismicity in the Hengill-Hromundartindur volcanic system, geothermal fluid extraction at the Svartsengi power plant, and possibly earthquake activity on the central part of the peninsula.
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| 24. |
- Oddsson, Asmundur, et al.
(author)
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Deficit of homozygosity among 1.52 million individuals and genetic causes of recessive lethality
- 2023
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In: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Journal article (peer-reviewed)abstract
- Genotypes causing pregnancy loss and perinatal mortality are depleted among living individuals and are therefore difficult to find. To explore genetic causes of recessive lethality, we searched for sequence variants with deficit of homozygosity among 1.52 million individuals from six European populations. In this study, we identified 25 genes harboring protein-altering sequence variants with a strong deficit of homozygosity (10% or less of predicted homozygotes). Sequence variants in 12 of the genes cause Mendelian disease under a recessive mode of inheritance, two under a dominant mode, but variants in the remaining 11 have not been reported to cause disease. Sequence variants with a strong deficit of homozygosity are over-represented among genes essential for growth of human cell lines and genes orthologous to mouse genes known to affect viability. The function of these genes gives insight into the genetics of intrauterine lethality. We also identified 1077 genes with homozygous predicted loss-of-function genotypes not previously described, bringing the total set of genes completely knocked out in humans to 4785.
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