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Sökning: L773:0029 8549 OR L773:1432 1939

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1.
  • Brzezinski, Juliusz, 1939, et al. (författare)
  • Smooth lattices over quadratic integers
  • 2008
  • Ingår i: Mathematische Zeitschrift. - : Springer Science and Business Media LLC. - 1432-1823 .- 0025-5874. ; 258:1, s. 161-184
  • Tidskriftsartikel (refereegranskat)abstract
    • We construct lattices with quadratic structure over the integers in quadratic number fields having the property that the rank of the quadratic structure is constant and equal to the rank of the lattice in all reductions modulo maximal ideals. We characterize the case in which such lattices are free. The construction gives a representative of the genus of such lattices as an orthogonal sum of "standard" pieces of ranks 1-4 and covers the case of the discriminant of the real quadratic number field congruent to 1 modulo 8 for which a general construction was not known. © 2007 Springer-Verlag.
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2.
  • Kiselman, Christer O., 1939- (författare)
  • How to best fold a triangle
  • 2017
  • Ingår i: Mathematische Semesterberichte. - : Springer Science and Business Media LLC. - 0720-728X .- 1432-1815. ; 65:1, s. 65-89
  • Tidskriftsartikel (refereegranskat)abstract
    • We fold a triangle once along a straight line and study how small the area of the folded figure can be. It can always be as small as the fraction 2 minus the square root of 2 of the area of the original triangle.  This is best possible: For every positive number q less than 2 minus the square root of 2 there are triangles that cannot be folded better than the fraction q.
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3.
  • Kiselman, Christer Oscar, Guest Professor, 1939-, et al. (författare)
  • Existence of continuous right inverses to linear mappings in finite-dimensional geometry
  • 2021
  • Ingår i: Mathematische Semesterberichte. - : Springer Science and Business Media LLC. - 0720-728X .- 1432-1815. ; 68, s. 55-68
  • Tidskriftsartikel (refereegranskat)abstract
    • A linear mapping of a compact convex subset of  a finite-dimensional vector space always possesses a right inverse,  but may lack a continuous right inverse, even if the set is smoothly  bounded.  Examples showing this are given, as well as conditions  guaranteeing the existence of a continuous right  inverse.
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4.
  • Biver, N., et al. (författare)
  • Coma composition of comet 67P/Churyumov-Gerasimenko from radio-wave spectroscopy
  • 2023
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 672
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results of a molecular survey of comet 67P/Churyumov-Gerasimenko undertaken with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m radio telescope in November–December 2021, when it had its most favourable apparition in decades. Observations at IRAM 30-m during the 12–16 November period covered 8 GHz bandwidth at 3 mm, 16 GHz at 2 mm, and 60 GHz in the 1 mm window domain. These were completed by snapshots at 1 mm on 12–13 December and a short observation of the H2O line at 557 GHz with the Odin sub-millimetre observatory on 17.0 November 2021, and with 18-cm observations of OH with the Nançay radio telescope. Less sensitive observations obtained at a previous perihelion passage on 18–22 September 2015 with IRAM and 9–12 November 2015 with Odin are also presented. The gas outflow velocity, outgassing pattern, and temperature have been accurately constrained by the observations. They are perfectly consistent with those measured in situ with the Rosetta/MIRO sub-millimetre instrument in 2015. In particular, the asymmetry of the line is well represented by a jet concentrating three-quarters of the outgassing in about π steradians. We derived abundances relative to water for seven molecules and significant upper limits for approximately five others. The retrieved abundances were compared to those measured in situ at the previous perihelion with Rosetta. While those of HCN, CH3OH, and HNCO are comparable, 67P is found to be depleted in H2S and relatively normal in CS (H2S/CS ≈ 3) in strong contradiction with the Rosetta/ROSINA mass spectrometer measurement of the H2S/CS2 (≈100) abundance ratio. While the formaldehyde total abundance found with IRAM 30-m when assuming it to be mostly produced by a distributed source (Haser parent scale length ≈8000 km) is similar to the one derived by Rosetta/ROSINA, we find that the formaldehyde coming from the nucleus is one order of magnitude less abundant than measured in situ by Rosetta/ROSINA. 
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5.
  • Biver, N., et al. (författare)
  • Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy)
  • 2016
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 589, s. Art. no. A78-
  • Tidskriftsartikel (refereegranskat)abstract
    • The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30 m telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January-3 February 2015. We detected 22 molecules and several isotopologues. The (H2O)-O-16 and (H2O)-O-18 production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of similar to 25%. The inferred isotope ratios in comet Lovejoy are O-16/O-18 = 499 +/- 24 and D/H = 1.4 +/- 0.4 x 10(-4) in water, S-32/S-34 = 24.7 +/- 3.5 in CS, all compatible with terrestrial values. The ratio C-12/C-13 = 109 +/- 14 in HCN is marginally higher than terrestrial and N-14/N-15 = 145 +/- 12 in HCN is half the Earth ratio. Several upper limits for D/H or C-12/C-13 in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system.
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6.
  • Biver, N., et al. (författare)
  • Periodic variation in the water production of comet C/2001 Q4 (NEAT) observed with the Odin satellite
  • 2009
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 501:1, s. 359-366
  • Tidskriftsartikel (refereegranskat)abstract
    • Context: Comet C/2001 Q4 (NEAT) was extensively studied with the 1.1-m submillimetre telescope of the Odin satellite. The H2O line at 557 GHz was regularly observed from 6 March to 16 May 2004 and nearly continuously monitored during 3 periods between 26 April and 2 May 2004. Aims: This last set of data shows periodic variations in the line intensity, and we looked for characterising the long- and short-term behaviour of this comet. Methods: We used the variance ratio method and χ2 minimization to find the period of variation in the water production rate and simulations to infer its amplitude at the nucleus surface. Results: A 40% periodic variation in the water production rate is measured with a period of 0.816±0.004 day (19.58±0.1 h). The comet also exhibits a seasonal effect with a mean peak of outgassing around 2.7×1029 molec. s-1 taking place about 18 days before perihelion.
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7.
  • Bjerkeli, Per, 1977, et al. (författare)
  • Odin observations of water in molecular outflows and shocks
  • 2009
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 507:3, s. 1455-1466
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: We investigate the ortho-water abundance in outflows and shocks in order to improve our knowledge of shock chemistry and of the physics behind molecular outflows.Methods: We used the Odin space observatory to observe the H2O(110-101) line. We obtain strip maps and single pointings of 13 outflows and two supernova remnants where we report detections for eight sources. We used RADEX to compute the beam averaged abundances of o-H2O relative to H2. In the case of non-detection, we derive upper limits on the abundance.Results: Observations of CO emission from the literature show that the volume density of H2 can vary to a large extent, a parameter that puts severe uncertainties on the derived abundances. Our analysis shows a wide range of abundances reflecting the degree to which shock chemistry affects the formation and destruction of water. We also compare our results with recent results from the SWAS team.Conclusions: Elevated abundances of ortho-water are found in several sources. The abundance reaches values as high as what would be expected from a theoretical C-type shock where all oxygen, not in the form of CO, is converted to water. However, the high abundances we derive could also be due to the low densities (derived from CO observations) that we assume. The water emission may in reality stem from high density regions much smaller than the Odin beam. We do not find any relationship between the abundance and the mass loss rate. On the other hand, there is a relation between the derived water abundance and the observed maximum outflow velocity.Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Étude Spatiale (CNES).The Swedish ESO Submillimetre Telescope (SEST) located at La Silla, Chile was funded by the Swedish Research Council (VR) and the European Southern Observatory. It was decommissioned in 2003. Appendix B is only available in electronic form at http://www.aanda.org
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8.
  • Blomsterwall, Elisabeth, et al. (författare)
  • Postural function and subjective eye level in patients with idiopathic normal pressure hydrocephalus.
  • 2011
  • Ingår i: Journal of neurology. - : Springer Science and Business Media LLC. - 1432-1459 .- 0340-5354. ; 258:7, s. 1341-6
  • Tidskriftsartikel (refereegranskat)abstract
    • Disturbance of posture is a frequent indication of idiopathic normal pressure hydrocephalus (iNPH) and is characterised by an increased sway in the frontal and sagittal planes. Further, iNPH patients with increased backward sway are known to have a defective perception of the subjective visual vertical (SVV), with the upper portion of an articulated rod tilted towards themselves. The objective of the present study was to compare subjective eye level (SEL) with actual eye level (EL) and compare this data with SVV and postural function. Twenty iNPH patients and ten normal controls estimated SEL by placing an adjustable horizontal line at EL. Sway pattern and SVV were also examined as previously described. The patients presented larger errors on downward as compared to upward line adjustments; all patients also presented a SVV tilted towards them. The patients swayed more in the sagittal than in the frontal plane at a higher speed than the normal controls, and they were relatively less helped by their vision. This is in accordance with the tendency to fall backwards seen in many iNPH patients. iNPH patients have a tendency to place SEL higher than EL and this, together with examination of SVV and sway pattern, suggests defective internal processing of gravicentric information.
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9.
  • Dellve, Lotta, 1965, et al. (författare)
  • Myofeedback training and intensive muscular strength training to decrease pain and improve work ability among female workers on long-term sick leave with neck pain: a randomized controlled trial
  • 2011
  • Ingår i: International archives of occupational and environmental health. - : Springer Science and Business Media LLC. - 1432-1246 .- 0340-0131. ; 84:3, s. 335-46
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract The theoretical framework is that muscle tension in the neck is related to insufficient muscular rest and is a risk factor for chronic pain and reduced work ability. Promoting muscle strength and muscle rest may increase work ability and reduce neck pain. Objectives To test whether myofeedback training or intensive strength training leads to decreased pain and increased work ability in women on long-term sick leave. Methods This is a randomized controlled trial of two 1-month interventions with myofeedback or muscular strength training in the home environment. Female human service organization workers (n = 60) on long-term (>60 days) sick leave and with chronic neck pain were followed with self-reported and laboratory-observed data of health, pain, muscular activation, and work ability, at baseline, immediately after the intervention and 3 months after baseline. Results For both intervention groups, pain was lowered over time compared with the control group. Decreased pain and muscular activity was associated with increased self-rated work ability and with laboratory-observed work ability at 3-month follow-up. Decreased pain was also associated with increased self-rated work ability at 1-month follow-up. Muscular strength training was associated with increased self-rated work ability and mental health. Myofeedback was associated with increased observed work ability and self- rated vitality. Conclusions The two interventions showed positive results, suggesting that they could be developed for use in health care practice to address pain and work ability. The intensive muscular strength training program, which is both easy to conduct at home and easy to coach, was associated with increased work ability.
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10.
  • Enerbäck, Charlotta, 1965, et al. (författare)
  • Stronger association with HLA-Cw6 than with corneodesmosin (S-gene) polymorphisms in Swedish psoriasis patients.
  • 2000
  • Ingår i: Archives of dermatological research. - : Springer Science and Business Media LLC. - 0340-3696 .- 1432-069X. ; 292:11, s. 525-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Psoriasis vulgaris is strongly associated with certain human leukocyte antigens, especially in early onset. The purpose of this study was to study the HLA-Cw6 allele and its contribution to disease susceptibility in a set of 104 families with at least two affected siblings. A sequencing method was utilized to examine the two exons that build up the antigen binding site of the C locus receptor. DNA from patients homozygous for Cw6 based on haplotype information were sequenced. The results confirmed the identity of the Cw6 allele in affected individuals with the consensus sequence for Cw*0602. We screened the set of families for psoriasis patients homozygous for Cw6 and found 11 individuals with a mean age at onset of 16.1 years. The corresponding figure for the Cw6 heterozygotes was 18.45 years and for the Cw6-negatives 22.36 years. This is indicative of a gene dose effect. We performed a transmission disequilibrium test (TDT) on the Cw6 allele per se, used as a biallelic marker. The analysis resulted in a P-value of 5.3 x 10(-17) (t167/nt45). This greatly exceeds our previous results of a TDT in the region, including microsatellite markers and single nucleotide polymorphisms (SNPs) in the coding part of the S gene (corneodesmosin), which is a suggested candidate gene in the region. The maximum nonparametric linkage (NPL) value was also reached using HLA-C as a marker. We conclude that Cw6 is the allele which shows the highest degree of association with psoriasis in our set of families and we propose that it directly influences the age at onset of the disease rather than increasing the genetic load in accordance with a polygenic theory.
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11.
  • Frisk, U., et al. (författare)
  • The Odin satellite - I. Radiometer design and test
  • 2003
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 402:3, s. L27-L34
  • Tidskriftsartikel (refereegranskat)abstract
    • The Sub-millimetre and Millimetre Radiometer (SMR) is the main instrument on the Swedish, Canadian, Finnish and French spacecraft Odin. It consists of a 1.1 metre diameter telescope with four tuneable heterodyne receivers covering the ranges 486-504 GHz and 541-581 GHz, and one fixed at 118.75 GHz together with backends that provide spectral resolution from 150 kHz to 1 MHz. This Letter describes the Odin radiometer, its operation and performance with the data processing and calibration described in Paper II.
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12.
  • Haghighi, Sara, et al. (författare)
  • Incidence of CSF abnormalities in siblings of multiple sclerosis patients and unrelated controls.
  • 2000
  • Ingår i: Journal of neurology. - 0340-5354 .- 1432-1459. ; 247:8, s. 616-22
  • Tidskriftsartikel (refereegranskat)abstract
    • We found that 19% (9/47) of healthy siblings of patients with clinically definite multiple sclerosis had an intrathecal immunological reaction with two or more 2 CSF-enriched oligoclonal bands (OCBs), in contrast to (4%) (2/50) unrelated healthy controls. Furthermore, in this group of nine healthy sibs the measles CSF IgG antibody titers were higher than that of the other sibs and that of controls. There were also differences in the serum titers for measles IgG antibody, which were higher in the group of all healthy sibs than in healthy volunteers, and (as with CSF titers) higher in the subgroup of healthy sibs with two or more 2 CSF-enriched OCBs than the other sibs. Thus a significant proportion of healthy siblings to MS patients have a partially hyperimmune condition similar to that occurring in MS, which in 19% manifested itself as an OCB reaction, in 9% as increased CSF measles IgG antibody titers, and in 21% as increased serum measles IgG antibody titers, these phenomena tending to occur in the same individuals. This condition is characterized by CSF-enriched OCBs with undefined specificity, although some increased antiviral reactivity is found both in the serum and CSF. While it needs further characterization, a genetic trait interacting with common infections is suggested. The recurrence risk of this condition is approximately five times higher than the 3-4% recurrence risk for manifest MS reported for sibs.
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13.
  • Karlsson, Roland, 1948-, et al. (författare)
  • 18-cm VLA observations of OH towards the Galactic Centre : Absorption and emission in the four ground-state OH lines
  • 2003
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 403, s. 1011-1021
  • Tidskriftsartikel (refereegranskat)abstract
    • The OH distribution in the Sgr A Complex has been observed in the 1612-, 1665-, 1667- and 1720-MHz OH transitions with the Very Large Array (VLA) in BnA configuration. Maps are presented with a channel velocity resolution of about 9 km s -1 and with angular resolutions of  . Some clear results are highlighted here, such as absorption from the Circumnuclear Disk (CND) and the OH-Streamer inside the CND near Sgr , strong absorption towards most of the eastern and western parts of the Sgr A East shell, lack of absorption towards both Sgr A West and the compact H II-regions to the east of Sgr A East, and double-lobed structure of the High Negative Velocity Gas (HNVG) oriented northeast and southwest of Sgr , and finally compact, point-like maser emission in all four transitions, in particular a 1720-MHz maser at -132 km s -1 in the CND as counterpart to a 1720-MHz maser at +132 km s -1 in the CND.
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14.
  • Karlsson, R., et al. (författare)
  • Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the Sgr A complex: VLA, Odin and SEST observations
  • 2013
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 554
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. The Sagittarius A complex in the Galactic centre comprises an ensemble of molecular clouds of different species with a variety of geometrical and kinematic properties. This work aims to study molecular abundances, morphology, and kinematics by comparing hydroxyl, water, carbon monoxide, ammonia, and atomic carbon and some of their isotopologues, in the +50 km s-1 cloud, the circumnuclear disk (CND), the +20 km s-1 cloud, the expanding molecular ring and the line-of-sight spiral arm features, including the Local/Sgr arm, the −30 km s-1 arm, and the 3-kpc arm.Methods. We observed the +50 km s-1 cloud, the CND and the +20 km s-1 cloud, and other selected positions at the Galactic centre with the VLA, and the Odin satellite. The VLA was used to map the 1665 and 1667 MHz OH lambda doublet main lines of the (2Π3/2) state, and the Odin satellite was used to map the 557 GHz H2O (110 − 101) line as well as to observe the 548 GHz H218O (110-101) line, the 572 GHz NH3 (10 − 00) line, the 576 GHz CO J = 5 − 4 line and the 492 GHz C i (3P1–3P0) line. Furthermore, the SEST was used to map a region of the Sgr A complex in the 220 GHz C18O J = 2−1 line.Results. Strong OH absorption, H2O emission and absorption lines were seen at all observed positions, and the H218O line was detected in absorption towards the +50 km s-1 cloud, the CND, the +20 km s-1cloud, the expanding molecular ring, and the 3-kpc arm. Strong CO J = 5−4, C18O J = 2−1, and neutral carbon C i emissions were seen towards the +50 and +20 km s-1 clouds. NH3 was only detected in weak absorption originating in the line-of-sight spiral arm features. The abundances of OH and H2O in the +50 and +20 km s-1 clouds reflect the different physical environments in the clouds, where shocks and star formation prevail in the +50 km s-1 cloud and giving rise to a higher rate of H2O production there than in the +20 km s-1 cloud. In the CND, cloud collisions and shocks are frequent, and the CND is also subject to intense UV-radiation emanating from the supermassive black hole and the central star cluster. The CND is rich in H2O and OH, and these abundances are considerably higher than in the +50 and +20 km s-1 clouds. We compare our estimated abundances of OH, H2O, and NH3 with similar and differing results for some other sources available in the literature. As compared to the quiescent cloud values of a few × 10-9, or lower, the H2O abundance is markedly enhanced in the front sides of the Sgr A molecular cloud cores, (2−7) × 10-8, as observed in absorption, and highest in the CND. A similar abundance enhancement is seen in OH. The likely explanation is PDR chemistry including grain surface reactions, and perhaps also the influence of shocks. In the redward high-velocity line wings of the +50 and +20 km s-1 clouds and the CND, the H2O abundances are estimated to be (1−6) × 10-6 or higher, i.e., similar to the water abundances in outflows of the Orion KL and DR21 molecular clouds, which are said to be caused by the combined action of shock desorption from icy grain mantles and high-temperature, gas-phase shock chemistry.
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15.
  • Karlsson, Roland, 1948-, et al. (författare)
  • The OH-streamer in Sagittarius A revisited : Analysis of hydroxyl absorption within 10 pc from the Galactic centre
  • 2015
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 582
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. We study the structure and kinematics of the OH-streamer and the +80 km s(-1) cloud and their interactions with the circumnu-clear disk (CND) and with other molecular clouds in the vicinity of the Galactic centre (GC), and we map OH absorption at about 6 '' resolution at R <= 10 pc from the GC, with about 9 km s(-1) of velocity resolution. Methods. The VLA was used to map OH line absorption at the 1665 and 1667 MHz lambda doublet main lines of the (2)Pi(3/2) state towards the Sagittarius A complex. Results. Strong OH absorption was found in the OH-streamer, the southern streamer (SS), the +20, +50, and +80 km s(-1) molecular clouds, the molecular belt, the CND, the expanding molecular ring (EMR), and the high negative velocity gas (HNVG). The OH-streamer was found to comprise three parts, head, mid, and tail, and to interact with the SS/+20, +80 km s(-1) clouds and the CND. Optical depths and column densities divided by excitation temperatures have been calculated for the OH-streamer and the +80 km s(-1) cloud. Conclusions. The OH-streamer, the SS, the +20 and +80 km s(-1) clouds, and the CND are intimately related in position and velocity space. The OH-streamer was found to be a clumpy object stretching in projection from the inner radius of the CND at about 1.8 pc from Sgr A*towards and partly engulfing Sgr A*. As a side result of our data, a possible link between the near side of the EMR and the CND's southwest lobe was found. Additionally, we found OH absorption against all four of the previously known compact H II regions A-D, located east of Sgr A East, indicating their close association with the +50 km s(-1) cloud.
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16.
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17.
  • Larsman, Pernilla, 1976, et al. (författare)
  • Psychosocial work conditions, perceived stress, perceived muscular tension, and neck/shoulder symptoms among medical secretaries
  • 2013
  • Ingår i: International Archives of Occupational and Environmental Health. - : Springer Science and Business Media LLC. - 1432-1246 .- 0340-0131. ; 86:1, s. 57-63
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose Unfavorable psychosocial working conditions are hypothesized to lead to perceived stress, which, in turn, can be related to an increased risk of development of neck/shoulder symptoms through increased and sustained muscle activation. The aim of the present study was to test this hypothesized process model among medical secretaries, a female-dominated profession characterized by a high amount of visual display unit use and a high prevalence of neck/shoulder symptoms. Methods In this cross-sectional study, a questionnaire survey was conducted among medical secretaries (n = 200). The proposed process model was tested using a path model framework. Results The results indicate that high work demands were related to high perceived stress, which in turn was related to a high perceived muscle tension and neck/shoulder symptoms. Low influence at work was not related to perceived stress, but was directly related to a high perceived muscle tension. Conclusions In general, these cross-sectional results lend tentative support for the hypothesis that adverse psychosocial work conditions (high work demands) may contribute to the development of neck/shoulder symptoms through the mechanism of stress-induced sustained muscular activation. This process model needs to be further tested in longitudinal studies.
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18.
  • Larsson, Bengt, et al. (författare)
  • Molecular oxygen in the rho Ophiuchi cloud
  • 2007
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 466:3, s. 5-
  • Tidskriftsartikel (refereegranskat)abstract
    • Context: Molecular oxygen, O2, has been expected historically to be an abundant component of the chemical species in molecular clouds and, as such, an important coolant of the dense interstellar medium. However, a number of attempts from both ground and from space have failed to detect O2 emission.Aims: The work described here uses heterodyne spectroscopy from space to search for molecular oxygen in the interstellar medium. Methods: The Odin satellite carries a 1.1 m sub-millimeter dish and a dedicated 119 GHz receiver for the ground state line of O2. Starting in 2002, the star forming molecular cloud core ρ Oph A was observed with Odin for 34 days during several observing runs.Results: We detect a spectral line at v_LSR =+3.5 km s-1 with Δ v_FWHM=1.5 km s-1, parameters which are also common to other species associated with ρ Oph A. This feature is identified as the O2 (NJ = 11 - 1_0) transition at 118 750.343 MHz.Conclusions: The abundance of molecular oxygen, relative to H{2} , is 5 × 10-8 averaged over the Odin beam. This abundance is consistently lower than previously reported upper limits.Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Étude Spatiale (CNES). The Swedish Space Corporation has been the industrial prime contractor and also is operating the satellite. Appendix A is only available in electronic form at http://www.aanda.org
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19.
  • Lis, D. C., et al. (författare)
  • Herschel/HIFI discovery of interstellar chloronium (H2Cl+)
  • 2010
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the first detection of chloronium, H_2Cl^+, in the interstellar medium, using the HIFI instrument aboard the Herschel Space Observatory. The 2_12-1_01 lines of ortho-H\_2^35Cl^+ and ortho-H\_2^37Cl^+ are detected in absorption towards NGC 6334I, and the 1_11-0_00 transition of para-H\_2^35Cl^+ is detected in absorption towards NGC 6334I and Sgr B2(S). The H_2Cl^+ column densities are compared to those of the chemically-related species HCl. The derived HCl/H_2Cl^+ column density ratios, ~1-10, are within the range predicted by models of diffuse and dense photon dominated regions (PDRs). However, the observed H_2Cl^+ column densities, in excess of 10^13 cm^-2, are significantly higher than the model predictions. Our observations demonstrate the outstanding spectroscopic capabilities of HIFI for detecting new interstellar molecules and providing key constraints for astrochemical models.
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20.
  • Liseau, René, 1949, et al. (författare)
  • Multi-line detection of O2 toward rho Ophiuchi A
  • 2012
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 541
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Models of pure gas-phase chemistry in well-shielded regions of molecular clouds predict relatively high levels of molecular oxygen, O-2, and water, H2O. These high abundances imply high cooling rates, leading to relatively short timescales for the evolution of gravitationally unstable dense cores, forming stars and planets. Contrary to expectations, the dedicated space missions SWAS and Odin typically found only very small amounts of water vapour and essentially no O-2 in the dense star-forming interstellar medium. Aims. Only toward rho OphA did Odin detect a very weak line of O-2 at 119 GHz in a beam of size 10 arcmin. The line emission of related molecules changes on angular scales of the order of some tens of arcseconds, requiring a larger telescope aperture such as that of the Herschel Space Observatory to resolve the O-2 emission and pinpoint its origin. Methods. We use the Heterodyne Instrument for the Far Infrared (HIFI) aboard Herschel to obtain high resolution O-2 spectra toward selected positions in the rho Oph A core. These data are analysed using standard techniques for O2 excitation and compared to recent PDR-like chemical cloud models. Results. The N-J = 3(3)-1(2) line at 487.2 GHz is clearly detected toward all three observed positions in the rho Oph A core. In addition, an oversampled map of the 5(4)-3(4) transition at 773.8 GHz reveals the detection of the line in only half of the observed area. On the basis of their ratios, the temperature of the O-2 emitting gas appears to vary quite substantially, with warm gas (greater than or similar to 50 K) being adjacent to a much colder region, of temperatures lower than 30 K. Conclusions. The exploited models predict that the O-2 column densities are sensitive to the prevailing dust temperatures, but rather insensitive to the temperatures of the gas. In agreement with these models, the observationally determined O-2 column densities do not seem to depend strongly on the derived gas temperatures, but fall into the range N(O-2) = 3 to greater than or similar to 6 x 10(15) cm(-2). Beam-averaged O-2 abundances are about 5 x 10(-8) relative to H-2. Combining the HIFI data with earlier Odin observations yields a source size at 119 GHz in the range of 4 to 5 arcmin, encompassing the entire rho Oph A core. We speculate that one of the reasons for the generally very low detection rate of O-2 is the short period of time during which O-2 molecules are reasonably abundant in molecular clouds.
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21.
  • Liseau, René, 1949, et al. (författare)
  • O(18)O and C(18)O observations of rho Ophiuchi A
  • 2010
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 510:1, s. A98 -
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Contrary to theoretical expectation, surprisingly low concentrations of molecular oxygen, O-2, have been found in the interstellar medium. Telluric absorption makes ground based O-2 observations essentially impossible and observations had to be done from space. Millimetre-wave telescopes on space platforms were necessarily small, which resulted in large, several arcminutes wide, beam patterns. Observations of the (N-J = 1(1)-1(0)) ground state transition of O-2 with the Odin satellite resulted in a greater than or similar to 5 sigma detection toward the dense core rho OphA. At the frequency of the line, 119 GHz, the Odin telescope has a beam width of 10', larger than the size of the dense core. Aims. The precise nature of the emitting source and its exact location and extent are therefore unknown. The current investigation is intended to remedy this. Methods. Although the Earth's atmosphere is entirely opaque to low-lying O-2 transitions, it allows ground based observations of the much rarer (OO)-O-16-O-18 in favourable conditions and at much higher angular resolution with larger telescopes. In addition, rho OphA exhibits both multiple radial velocity systems and considerable velocity gradients. Extensive mapping of the region in the proxy (CO)-O-18 (J = 3-2) line can be expected to help identify the O-2 source on the basis of its line shape and Doppler velocity. Line opacities were determined from observations of optically thin (CO)-C-13-O-18 (J = 3-2). During several observing periods, two C18O intensity maxima in rho OphA were searched for (OO)-O-18 in the (2(1)-0(1)) line at 234 GHz with the 12m APEX telescope. These positions are associated also with peaks in the mm-continuum emission from dust. Results. Our observations resulted in an upper limit on the integrated O18O intensity of integral T-A* dv 16. Combining Odin's O-2 with the present (OO)-O-18 observations we infer an O-2 abundance 5 x 10(-7)
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22.
  • Lycke, Jan, 1956, et al. (författare)
  • Asymptomatic visual loss in multiple sclerosis.
  • 2001
  • Ingår i: Journal of neurology. - : Springer Science and Business Media LLC. - 0340-5354 .- 1432-1459. ; 248:12, s. 1079-86
  • Tidskriftsartikel (refereegranskat)abstract
    • Visual disturbances are common in multiple sclerosis (MS) and often a result of acute demyelinating optic neuropathy. Careful examination of MS patients, who have never suffered optic neuritis, may also reveal asymptomatic visual loss. This type of silent disease activity was investigated by computerised resolution perimetry, which has the potential to reflect the percentage of functional retino-cortical neural channels. The time of onset and the evolution of asymptomatic visual loss was investigated. One approach was to retrospectively select patients who never had suffered acute optic neuritis from a closely monitored MS population and re-examine them again. Sixteen patients were identified and vision was evaluated during a period of 5.5-9 years of follow-up and compared with that in 14 healthy controls. The mean channel percentage of the MS group was 89 +/- 19 % (SD) on entry into the study, compared with 110 +/- 15% (SD) of controls (p < 0.003). At termination of the study the mean percentage was essentially unchanged both in MS patients (87 +/- 21%, SD) and controls (110 +/- 19%, SD). The second approach was to test a group of 7 patients with MS or strongly suspected MS, with the same method, in close connection with their first clinical exacerbation. All cases lacked visual symptoms and none had previously had acute visual loss. Again, virtually all performed subnormally in the vision tests, and to the same degree as in the first group of patients. Results were compared with those obtained from 25 MS patients who had experienced one or more attacks of optic neuritis. Compared with controls the loss of functional retino-cortical neural channels was 20% in patients without a previous history of optic neuritis and 30 % in patients who previously had experienced optic neuritis. We conclude that asymptomatic visual loss seems to be a universal feature of MS and has a substantial impact on the visual pathways, that it is present already at the time of clinical onset of the disease, and that any progression thereafter is slow enough to elude detection during several years of follow-up.
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23.
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24.
  • Olofsson, Henrik, 1972, et al. (författare)
  • A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite. I. The observational data
  • 2007
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 476:number 2, December III, s. 791-806
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims.Spectral line surveys are useful since they allow identification of new molecules and new lines in uniformly calibrated data sets. The subsequent multi-transition analysis will provide improved knowledge of molecular abundances, cloud temperatures and densities, and may also reveal previously unsuspected blends of molecular lines, which otherwise may lead to erroneous conclusions. Nonetheless, large portions of the sub-millimetre spectral regime remain unexplored due to severe absorptions by H2O and O2 in the terrestrial atmosphere. The purpose of the measurements presented here is to cover wavelength regions at and around 0.55 mm - regions largely unobservable from the ground.Methods.Using the Odin astronomy/aeronomy satellite, we performed the first spectral survey of the Orion KL molecular cloud core in the bands 486-492 and 541-576 GHz with rather uniform sensitivity (22-25 mK baseline noise). Odin's 1.1 m size telescope, equipped with four cryo-cooled tuneable mixers connected to broad band spectrometers, was used in a satellite position-switching mode. Two mixers simultaneously observed different 1.1 GHz bands using frequency steps of 0.5 GHz (25 h each). An on-source integration time of 20 h was achieved for most bands. The entire campaign consumed ~1100 orbits, each containing one hour of serviceable astro-observation.Results.We identified 280 spectral lines from 38 known interstellar molecules (including isotopologues) having intensities in the range 80 to 0.05 K. An additional 64 weak lines remain unidentified. Apart from the ground state rotational 11,0-10,1 transitions of ortho-H2O, H218O and H217O, the high energy 62,4-71,7 line of para-H2O (Eu=867$\,$K) and the HDO(20,2-11,1) line have been observed, as well as the 10-01 lines from NH3 and its rare isotopologue 15NH3. We suggest assignments for some unidentified features, notably the new interstellar molecules ND and SH-. Severe blends have been detected in the line wings of the H218O, H217O and 13CO lines changing the true linewidths of the outflow emission.
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25.
  • Olofsson, Henrik, 1972, et al. (författare)
  • Odin water mapping in the Orion KL region
  • 2003
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 402, s. L47-L54
  • Tidskriftsartikel (refereegranskat)abstract
    • New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1\arcmin beam size at 557 GHz), are presented. The ortho-H2O \jkktrans{1}{1}{0}{1}{0}{1} ground state transition was observed in a 7arcminx 7arcmin rectangular grid with a spacing of 1\arcmin, while the same line of H218O was measured in two positions, Orion KL itself and 2\arcmin south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60\arcsec-110\arcsec. The H2O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near (or ``blue'') part of the outflow (and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL H218O outflow emission emanates from the compact (size ~ 15\arcsec) low-velocity flow and here estimate an H2O abundance of circa 10-5 compared to all H2 in the flow - an order of magnitude below earlier estimates of the H2O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. H218O is detected for the first time in the southern position at a level of ~ 0.15 K and we here estimate an H2O abundance of (1-8) x 10-8. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'Études Spatiales (CNES, France). The Swedish Space Corporation (SSC) was the industrial prime contractor and is also responsible for the satellite operation.
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26.
  • Persson, Carina, 1964, et al. (författare)
  • A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite. II. Data analysis
  • 2007
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 476:2, December III, s. 807-827
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims.We investigate the physical and chemical conditions in a typical star forming region, including an unbiased search for new molecules in a spectral region previously unobserved.Methods.Due to its proximity, the Orion KL region offers a unique laboratory of molecular astrophysics in a chemically rich, massive star forming region. Several ground-based spectral line surveys have been made, but due to the absorption by water and oxygen, the terrestrial atmosphere is completely opaque at frequencies around 487 and 557 GHz. To cover these frequencies we used the Odin satellite to perform a spectral line survey in the frequency ranges 486-492 GHz and 541-577 GHz, filling the gaps between previous spectral scans. Odin's high main beam efficiency, $\eta_{{\rm mb}}$ = 0.9, and observations performed outside the atmosphere make our intensity scale very well determined.Results.We observed 280 spectral lines from 38 molecules including isotopologues, and, in addition, 64 unidentified lines. A few U-lines have interesting frequency coincidences such as ND and the anion SH-. The beam-averaged emission is dominated by CO, H2O, SO2, SO, 13CO and CH3OH. Species with the largest number of lines are CH3OH, (CH3)2O, SO2, 13CH3OH, CH3CN and NO. Six water lines are detected including the ground state rotational transition 11,0-10,1 of o-H2O, its isotopologues o-H218O and o-H217O, the Hot Core tracing p-H2O transition 62,4-71,7, and the 20, 2-11,1 transition of HDO. Other lines of special interest are the 10-0$_$ transition of NH3 and its isotopologue 15NH3. Isotopologue abundance ratios of D/H, 12C/13C, 32S/34S, 34S/33S, and 18O/17O are estimated. The temperatures, column densities and abundances in the various subregions are estimated, and we find very high gas-phase abundances of H2O, NH3, SO2, SO, NO, and CH3OH. A comparison with the ice inventory of ISO sheds new light on the origin of the abundant gas-phase molecules.
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27.
  • Persson, Carina, 1964, et al. (författare)
  • The first spectral line surveys searching for signals from the dark ages
  • 2010
  • Ingår i: Astronomy and Astrophysics. - Paris : EDP Sciences. - 0004-6361 .- 1432-0746. ; 515:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. Our aim is to observationally investigate the cosmic Dark Ages in order to constrain star and structure formation models, as well as the chemical evolution in the early Universe. Methods. Spectral lines from atoms and molecules in primordial perturbations at high redshifts can give information about the conditions in the early universe before and during the formation of the first stars in addition to the epoch of reionisation. The lines may arise from moving primordial perturbations before the formation of the first stars (resonant scattering lines), or could be thermal absorption or emission lines at lower redshifts. The difficulties in these searches are that the source redshift and evolutionary state, as well as molecular species and transition are unknown, which implies that an observed line can fall within a wide range of frequencies. The lines are also expected to be very weak. Observations from space have the advantages of stability and the lack of atmospheric features which is important in such observations. We have therefore, as a first step in our searches, used the Odin* satellite to perform two sets of spectral line surveys towards several positions. The first survey covered the band 547-578 GHz towards two positions, and the second one covered the bands 542.0-547.5 GHz and 486.5-492.0 GHz towards six positions selected to test different sizes of the primordial clouds. Two deep searches centred at 543.250 and 543.100 GHz with 1 GHz bandwidth were also performed towards one position. The two lowest rotational transitions of H-2 will be redshifted to these frequencies from z similar to 20-30, which is the predicted epoch of the first star formation. Results. No lines are detected at an rms level of 14-90 and 5-35 mK for the two surveys, respectively, and 2-7 mK in the deep searches with a channel spacing of 1-16 MHz. The broad bandwidth covered allows a wide range of redshifts to be explored for a number of atomic and molecular species and transitions. From the theoretical side, our sensitivity analysis show that the largest possible amplitudes of the resonant lines are about 1 mK at frequencies less than or similar to 200 GHz, and a few mu K around 500-600 GHz, assuming optically thick lines and no beam-dilution. However, if existing, thermal absorption lines have the potential to be orders of magnitude stronger than the resonant lines. We make a simple estimation of the sizes and masses of the primordial perturbations at their turnaround epochs, which previously has been identified as the most favourable epoch for a detection. This work may be considered as an important pilot study for our forthcoming observations with the Herschel Space Observatory.
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28.
  • Persson, Carina, 1964, et al. (författare)
  • Upper limits to interstellar NH+ and para-NH2- abundances. Herschel-HIFI observations towards Sgr B2 (M) and G10.6-0.4 (W31C)
  • 2014
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 567, s. Art. no. A130-
  • Tidskriftsartikel (refereegranskat)abstract
    • The understanding of interstellar nitrogen chemistry has improved significantly with recent results from the Herschel Space Observatory. To set even better constraints, we report here on deep searches for the NH+ ground state rotational transition J=1.5-0.5 of the ^2Pi_1/2 lower spin ladder, with fine-structure transitions at 1013 and 1019 GHz, and the para-NH2- 1_1,1-0_0,0 rotational transition at 934 GHz towards Sgr B2(M) and G10.6-0.4 using Herschel-HIFI. No clear detections of NH+ are made and the derived upper limits are
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29.
  • Persson, Carina, 1964, et al. (författare)
  • Water and ammonia abundances in S140 with the Odin satellite
  • 2009
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 2:494, s. 637-646
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the effect of the physical environment on water and ammonia abundances across the S140 photodissociation region (PDR) with an embedded outflow.We used the Odin satellite to obtain strip maps of the ground-state rotational transitions of ortho-water and ortho-ammonia, as well as CO(5-4) and 13co(5-4) across the PDR, and H_2^18O in the central position. A physi-chemicalinhomogeneous PDR model was used to compute the temperature and abundance distributions for water, ammonia, and CO. A multi-zone escape probability method then calculated the level populations and intensity distributions. These results are compared to a homogeneous model computed with an enhanced version of the RADEX code.H_2O, NH_3, and ^13CO show emission from an extended PDR with a narrow line width of ~3 km/s. Like CO, the water line profile is dominated by outflow emission, but mainly in the red wing. Even though CO shows strong self-absorption, no signs of self-absorption are seen in the water line. The H_2^18O molecule is not detected.The PDR model suggests that the water emission arises mainly from the surfaces of optically thick, high-density clumps with n(H_2)>10^6 cm^-3 and a clump water abundance, with respect to H_2, of 5*10^-8. The mean water abundance in the PDR is 5*10^-9 and between ~4*10^-8 - 4*10^-7 in the outflow derived from a simple two-level approximation.The RADEX model points to a somewhat higher average PDR water abundance of 1*10^-8. At low temperatures deep in the cloud, the water emission is weaker, likely due to adsorption onto dust grains, while ammonia is still abundant. Ammonia is also observed in the extended clumpy PDR, likely from the same high density and warm clumps as water. The average ammonia abundance is about the same as for water: 4*10^-9 and 8*10^-9 given by the PDR model and RADEX, respectively. The differences between the models most likely arise from uncertainties in density,beam-filling, and volume-filling of clumps. The similarity of water and ammonia PDR emission is also seen in the almost identical line profiles observed close to the bright rim. Around the central position, ammonia also shows some outflow emission, although weaker than water in the red wing. Predictions of the H_2O 1(1,0)-1(0,1) and 1(1,1)-0(0,0) antenna temperatures across the PDR are estimated with our PDR model for the forthcoming observations with the Herschel Space Observatory.
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30.
  • Rinck, Peter A., et al. (författare)
  • Paul Christian Lauterbur
  • 2007
  • Ingår i: European Radiology. - : Springer. - 0938-7994 .- 1432-1084. ; 17:8, s. 2208-2210
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • n/a
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31.
  • Sandqvist, Aage, et al. (författare)
  • Herschel HIFI observations of the Sgr A+50 km s(-1) Cloud Deep searches for O-2 in emission and foreground absorption
  • 2015
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 584
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The Herschel Oxygen Project (HOP) is an open time key program, awarded 140 h of observing time to search for molecular oxygen (O-2) in a number of interstellar sources. To date O-2 has definitely been detected in only two sources, namely rho Oph A and Orion, reflecting the extremely low abundance of O-2 in the interstellar medium. Aims. One of the sources in the HOP program is the + 50 km s(-1) Cloud in the Sgr A Complex in the centre of the Milky Way. Its environment is unique in the Galaxy and this property is investigated to see if it is conducive to the presence of O-2. Methods. The Herschel Heterodyne Instrument for the Far Infrared (HIFI) is used to search for the 487 and 774 GHz emission lines of O-2. Results. No O-2 emission is detected towards the Sgr A + 50 km s(-1) Cloud, but a number of strong emission lines of methanol (CH3OH) and absorption lines of chloronium (H2Cl+) are observed. Conclusions. A 3 sigma upper limit for the fractional abundance ratio of [O-2]/[H-2] in the Sgr A + 50 km s(-1) Cloud is found to be X(O-2)
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32.
  • Sandqvist, Aage, et al. (författare)
  • Odin observations of ammonia in the SgrA+50 km s(-1) cloud and circumnuclear disk
  • 2017
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 599
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The Odin satellite is now into its sixteenth year of operation, much surpassing its design life of two years. One of the sources which Odin has observed in great detail is the Sgr A complex in the centre of the Milky Way.Aims. To study the presence of NH3 in the Galactic centre and spiral arms.Methods. Recently, Odin has made complementary observations of the 572 GHz NH3 line towards the SgrA + 50 km s(-1) cloud and circumnuclear disk (CND).Results. Significant NH3 emission has been observed in both the + 50 km s(-1) cloud and the CND. Clear NH3 absorption has also been detected in many of the spiral arm features along the line of sight from the Sun to the core of our Galaxy.Conclusions. The very large velocity width (80 km s 1) of the NH3 emission associated with the shock region in the southwestern part of the CND may suggest a formation / desorption scenario similar to that of gas-phase H2O in shocks / outflows.
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33.
  • Sandzén, Birger, 1944-, et al. (författare)
  • Treatment of Common Bile Duct Stones in Sweden 1989-2006 : An Observational Nationwide Study of a Paradigm Shift
  • 2012
  • Ingår i: World Journal of Surgery. - New York : Springer-Verlag New York. - 0364-2313 .- 1432-2323. ; 36:9, s. 2146-2153
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: The preferred strategies for treatment of common bile duct stones have changed from choledochotomy with cholecystectomy to sphincterotomy with or without cholecystectomy. The aim of the present study was to compare the effectiveness of these treatment strategies on a nationwide level in Sweden. METHODS: All patients with hospital care for benign biliary diagnoses 1988-2006 were identified in Swedish registers. Patients with common bile duct stones and a first admission with choledochotomy and or endoscopic sphincterotomy from 1989 through 2006 comprised the study group. These patients were analyzed with respect to readmission for biliary diagnoses and acute pancreatitis. RESULTS: Incidence of open and laparoscopic choledochotomy decreased from 19.4 to 5.2, whereas endoscopic sphincterotomy increased from 5.1 to 26.1 per 100,000 inhabitants per year, respectively. Among patients treated for common bile duct stones (n = 26,815), 60.0 % underwent cholecystectomy during the first hospital admission in 1989-1994, compared to 30.1 % in 2001-2006. The treatment strategy that included endoscopic sphincterotomy was associated with more readmissions for biliary diagnoses and increased risk for acute pancreatitis than the treatment strategy with choledochotomy. However, patients treated with endoscopic sphincterotomy and concurrent cholecystectomy at the index admission had the lowest risk of readmission. CONCLUSIONS: Cholecystectomy has been increasingly separated from treatment of bile duct stones, and endoscopic sphincterotomy has superseded choledochotomy as a first alternative for bile duct clearance in Sweden. In patients fit for surgery, clearance of the common bile duct can be combined with cholecystectomy, as it probably reduces the need for biliary related readmissions.
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34.
  • Thorsson, Sofia, 1972, et al. (författare)
  • Thermal bioclimatic conditions and patterns of behaviour in an urban park in Goteborg, Sweden
  • 2004
  • Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 48:3, s. 149-156
  • Tidskriftsartikel (refereegranskat)abstract
    • People in urban areas frequently use parks for recreation and outdoor activities. Owing to the complexity of the outdoor environment, there have only been a few attempts to understand the effect of the thermal environment on people's use of outdoor spaces. This paper therefore seeks to determine the relationship between the thermal environment, park use and behavioural patterns in an urban area of Sweden. The methods used include structured interviews, unobtrusive observations of the naturally occurring behaviour and simultaneous measurements of thermal comfort variables, i.e., air temperature, air humidity, wind speed and global radiation. The thermal environment is investigated through the mean radiant temperature (T-mrt) and the predicted mean vote (PMV) index. The outcome is compared to the subjective behaviour and thermal sensation of the interviewees. It is found that the thermal environment, access and design are important factors in the use of the park. In order to continue to use the park when the thermal conditions become too cold or too hot for comfort, people improve their comfort conditions by modifying their clothing and by choosing the most supportive thermal opportunities available within the place. The study also shows that psychological aspects such as time of exposure, expectations, experience and perceived control may influence the subjective assessment. Comparison between the thermal sensation of the interviewees and the thermal sensation assessed by the PMV index indicates that steady-state models such as the PMV index may not be appropriate for the assessment of short-term outdoor thermal comfort, mainly because they are unable to analyse transient exposure.
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35.
  • Wikkelsö, Carsten, et al. (författare)
  • Subjective visual vertical and Romberg's test correlations in hydrocephalus.
  • 2003
  • Ingår i: Journal of neurology. - : Springer Science and Business Media LLC. - 0340-5354 .- 1432-1459. ; 250:6, s. 741-5
  • Tidskriftsartikel (refereegranskat)abstract
    • Exploration of the subjective visual vertical in pitch and Romberg's test in patients with hydrocephalus. Patients Eleven patients with communicating normal pressure hydrocephalus and six with non-communicating hydrocephalus due to aqueductal stenosis were examined before and after surgical treatment.The subjective visual vertical was examined with a simple, custom-made articulated rod. The rod was faintly illuminated from within so as to appear floating in space when presented in darkness. The test task was to manually adjust the rod's position in pitch so that it appeared perfectly vertical. Romberg's test was performed under standardized conditions.Patients with a backward movement on Romberg's test showed a deviation of the subjective visual vertical, tilting the upper end of the rod closer to their eyes. Patients moving in other directions tilted the rod in the opposite direction (p < 0.01). The time in which the patients managed Romberg's test with open eyes correlated with the intratest variability of rod placement (r = 0.86, p < 0.001). After surgery, improvements on Romberg's test correlated with a decreased intratest variability of the subjective visual vertical. There were no differences between the two patient groups.Quantitative measurements of the subjective visual vertical in pitch correlate strongly with results of Romberg's test in patients with hydrocephalus.
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36.
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37.
  • Wirström, Eva, 1977, et al. (författare)
  • A search for pre-biotic molecules in hot cores
  • 2007
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 473, s. 177-180
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. Our aim is to better understand the complex chemistry of organic molecules in the interstellar medium, leading to the formation of pre-biotic molecules such as amino acids.Methods. We have performed a search for the pre-biotic molecules amino acetonitrile (H2N CH2 CN) and vinyl acetylene (C2H3 CCH) towards four northern hot core sources using the Onsala 20 m telescope.Results. We have determined upper limits to the column density of amino acetonitrile (1-4*10^13 cm^-2) and vinyl acetylene (2-7*10^14 cm^-2) in the observed sources. In addition, from the absence of other lines within the observed frequency band, we have further constrained the column density of oxiranecarbonitrile (c-C3H3 NO) and amino-ethanol (NH2 CH2 CH2 OH) in these sources.
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38.
  • Wirström, Eva, 1977, et al. (författare)
  • Ground-state ammonia and water in absorption towards Sgr B2
  • 2010
  • Ingår i: Astronomy and Astrophysics. - Paris, France : EDP Sciences. - 0004-6361 .- 1432-0746. ; 522:1, s. A19, 1-9
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Observations of transitions to the ground-state of a molecule are essential to obtain a complete picture of its excitation and chemistry in the interstellar medium, especially in diffuse and/or cold environments. For the important interstellar molecules H2O and NH3, these ground-state transitions are heavily absorbed by the terrestrial atmosphere, hence not observable from the ground.Aims: We attempt to understand the chemistry of nitrogen, oxygen, and their important molecular forms, NH3 and H2O in the interstellar medium of the Galaxy.Methods: We have used the Odin* submillimetre-wave satellite telescope to observe the ground state transitions of ortho-ammonia and ortho-water, including their 15N, 18O, and 17O isotopologues, towards Sgr B2. The extensive simultaneous velocity coverage of the observations, >500 km s-1, ensures that we can probe the conditions of both the warm, dense gas of the molecular cloud Sgr B2 near the Galactic centre, and the more diffuse gas in the Galactic disk clouds along the line-of-sight.Results: We present ground-state NH3 absorption in seven distinct velocity features along the line-of-sight towards Sgr B2. We find a nearly linear correlation between the column densities of NH3 and CS, and a square-root relation to N2H+. The ammonia abundance in these diffuse Galactic disk clouds is estimated to be about 0.5–1 × 10-8, similar to that observed for diffuse clouds in the outer Galaxy. On the basis of the detection of H_218O absorption in the 3 kpc arm, and the absence of such a feature in the H_217O spectrum, we conclude that the water abundance is around 10-7, compared to ~10-8 for NH3. The Sgr B2 molecular cloud itself is seen in absorption in NH3, 15NH3, H2O, H_218O, and H_217O, with emission superimposed on the absorption in the main isotopologues. The non-LTE excitation of NH3 in the environment of Sgr B2 can be explained without invoking an unusually hot (500 K) molecular layer. A hot layer is similarly not required to explain the line profiles of the 11,0≥ts10,1 transition from H2O and its isotopologues. The relatively weak 15NH3 absorption in the Sgr B2 molecular cloud indicates a high [ 14N/15N] isotopic ratio >600. The abundance ratio of H_218O and H_217O is found to be relatively low, 2.5–3. These results together indicate that the dominant nucleosynthesis process in the Galactic centre is CNO hydrogen burning.Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the centre National d'Études Spatiales (CNES, France). The Swedish Space Corporation (SSC) was the industrial prime contractor and is also responsible for the satellite operation.
  •  
39.
  • Wirström, Eva, 1977, et al. (författare)
  • Observational tests of interstellar methanol formation
  • 2011
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 533, s. A24-
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. It has been established that the classical gas-phase production of interstellar methanol (CH(3)OH) cannot explain observed abundances. Instead it is now generally thought that the main formation path has to be by successive hydrogenation of solid CO on interstellar grain surfaces. Aims. While theoretical models and laboratory experiments show that methanol is efficiently formed from CO on cold grains, our aim is to test this scenario by astronomical observations of gas associated with young stellar objects (YSOs). Methods. We have observed the rotational transition quartets J = 2(K) - 1(K) of (12)CH(3)OH and (13)CH(3)OH at 96.7 and 94.4 GHz, respectively, towards a sample of massive YSOs in different stages of evolution. In addition, the J = 1-0 transitions of (12)C(18)O and (13)C(18)O were observed towards some of these sources. We use the (12)C/(13)C ratio to discriminate between gas-phase and grain surface origin: If methanol is formed from CO on grains, the ratios should be similar in CH(3)OH and CO. If not, the ratio should be higher in CH(3)OH due to (13)C fractionation in cold CO gas. We also estimate the abundance ratios between the nuclear spin types of methanol (E and A). If methanol is formed on grains, this ratio is likely to have been thermalized at the low physical temperature of the grain, and therefore show a relative over-abundance of A-methanol. Results. We show that the (12)C/(13)C isotopic ratio is very similar in gas-phase CH(3)OH and C(18)O, on the spatial scale of about 40 '', towards four YSOs. For two of our sources we find an overabundance of A-methanol as compared to E-methanol, corresponding to nuclear spin temperatures of 10 and 16 K. For the remaining five sources, the methanol E/A ratio is less than unity. Conclusions. While the (12)C/(13)C ratio test is consistent with methanol formation from hydrogenation of CO on grain surfaces, the result of the E/A ratio test is inconclusive.
  •  
40.
  • Wirström, Eva, 1977, et al. (författare)
  • Odin * CO and 13CO J=5-4 mapping of Orion KL - a step towards accurate water abundances
  • 2006
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 453, s. 979-987
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. The very high main beam efficiency (90%) of the telescope on the sub-millimetre wave satellite Odin, in combination with the small calibration errors in the absence of atmospheric attenuation, assures that observed line brightness temperatures are very accurately determined. Based on this, we attempt to determine the column density distribution of H-2, and the ortho-water abundance, in the Orion KL region.Methods. We have, for the first time, mapped the (CO)-C-12 J = 5-4 emission in a 7' x 7' region covering Orion KL, observed simultaneously with a (CO)-C-13 J = 5-4 map. Also presented are (CO)-O-18 J = 5-4 emission data at four different positions and a (CO)-O-17 J = 5-4 emission spectrum detected towards the Orion KL position. The Odin mapping was performed at 1' spacing ( beam full width at half maximum 126'' at 557 GHz).Results. The CO J = 5-4 narrow line emission from this region mainly arises in the warm, dense gas at the interface ( the photon-dominated region) between the M42 HII region and the Orion A molecular cloud, the Orion PDR. The (CO)-C-12 and (CO)-C-13 J = 5-4 emission maps have been used to determine the column density distribution of H-2 gas across the Orion KL region. The results have been verified by comparing to column densities obtained using the decidedly optically thin (CO)-O-18 emission as input to the RADEX radiative transfer code. We find H-2 column densities ranging from 5 x 10(21) cm(-2) at map edges to 7 x 10(22) cm(-2) at the molecular ridge. The mass of the gas in the mapped region is estimated to be 480 M-circle dot, of which 320 M-circle dot is situated towards the molecular ridge. We estimate that about half of this mass belongs to the warm Orion PDR interface layer. Finally, based on data from the positions where (CO)-O-18 J = 5-4 has been observed, we estimate the ortho-water abundance in the Orion PDR layer to be >= 8 x 10(-8), higher than previously estimated.
  •  
41.
  • Norén, Karin, et al. (författare)
  • Pulses of movement across the sea ice: population connectivity and temporal genetic structure in the arctic fox
  • 2011
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 166:4, s. 973-984
  • Tidskriftsartikel (refereegranskat)abstract
    • Lemmings are involved in several important functions in the Arctic ecosystem. The Arctic fox (Vulpes lagopus) can be divided into two discrete ecotypes: “lemming foxes” and “coastal foxes”. Crashes in lemming abundance can result in pulses of “lemming fox” movement across the Arctic sea ice and immigration into coastal habitats in search for food. These pulses can influence the genetic structure of the receiving population. We have tested the impact of immigration on the genetic structure of the “coastal fox” population in Svalbard by recording microsatellite variation in seven loci for 162 Arctic foxes sampled during the summer and winter over a 5-year period. Genetic heterogeneity and temporal genetic shifts, as inferred by STRUCTURE simulations and deviations from Hardy–Weinberg proportions, respectively, were recorded. Maximum likelihood estimates of movement as well as STRUCTURE simulations suggested that both immigration and genetic mixture are higher in Svalbard than in the neighbouring “lemming fox” populations. The STRUCTURE simulations and AMOVA revealed there are differences in genetic composition of the population between summer and winter seasons, indicating that immigrants are not present in the reproductive portion of the Svalbard population. Based on these results, we conclude that Arctic fox population structure varies with time and is influenced by immigration from neighbouring populations. The lemming cycle is likely an important factor shaping Arctic fox movement across sea ice and the subsequent population genetic structure, but is also likely to influence local adaptation to the coastal habitat and the prevalence of diseases.
  •  
42.
  • Aerts, R., et al. (författare)
  • Seasonal climate manipulations have only minor effects on litter decomposition rates and N dynamics but strong effects on litter P dynamics of sub-arctic bog species
  • 2012
  • Ingår i: Oecologia. - : Springer. - 0029-8549 .- 1432-1939. ; 170:3, s. 809-819
  • Tidskriftsartikel (refereegranskat)abstract
    • Litter decomposition and nutrient mineralization in high-latitude peatlands are constrained by low temperatures. So far, little is known about the effects of seasonal components of climate change (higher spring and summer temperatures, more snow which leads to higher winter soil temperatures) on these processes. In a 4-year field experiment, we manipulated these seasonal components in a sub-arctic bog and studied the effects on the decomposition and N and P dynamics of leaf litter of Calamagrostis lapponica, Betula nana, and Rubus chamaemorus, incubated both in a common ambient environment and in the treatment plots. Mass loss in the controls increased in the order Calamagrostis < Betula < Rubus. After 4 years, overall mass loss in the climate-treatment plots was 10 % higher compared to the ambient incubation environment. Litter chemistry showed within each incubation environment only a few and species-specific responses. Compared to the interspecific differences, they resulted in only moderate climate treatment effects on mass loss and these differed among seasons and species. Neither N nor P mineralization in the litter were affected by the incubation environment. Remarkably, for all species, no net N mineralization had occurred in any of the treatments during 4 years. Species differed in P-release patterns, and summer warming strongly stimulated P release for all species. Thus, moderate changes in summer temperatures and/or winter snow addition have limited effects on litter decomposition rates and N dynamics, but summer warming does stimulate litter P release. As a result, N-limitation of plant growth in this sub-arctic bog may be sustained or even further promoted.
  •  
43.
  • Ahlbäck Widenfalk, Lina, et al. (författare)
  • Spatially structured environmental filtering of collembolan traits in late successional salt marsh vegetation
  • 2015
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 179, s. 537-549
  • Tidskriftsartikel (refereegranskat)abstract
    • Both the environment and the spatial configuration of habitat patches are important factors that shape community composition and affect species diversity patterns. Species have traits that allow them to respond to their environment. Our current knowledge on environment to species traits relationships is limited in spite of its potential importance for understanding community assembly and ecosystem function. The aim of our study was to examine the relative roles of environmental and spatial variables for the small-scale variation in Collembola (springtail) communities in a Dutch salt marsh. We used a trait-based approach in combination with spatial statistics and variance partitioning, between environmental and spatial variables, to examine the important ecological factors that drive community composition. Turnover of trait diversity across space was lower than for species diversity. Most of the variation in community composition was explained by small-scale spatial variation in topography, on a scale of 4-6 m, most likely because it determines the effect of inundation, which restricts where habitat generalists can persist. There were only small pure spatial effects on species and trait diversity, indicating that biotic interactions or dispersal limitation probably were less important for structuring the community at this scale. Our results suggest that for springtails, life form (i.e. whether they live in the soil or litter or on the surface/in vegetation) is an important and useful trait to understand community assembly. Hence, using traits in addition to species identity when analysing environment-organism relationships results in a better understanding of the factors affecting community composition.
  •  
44.
  • Albrectsen, Benedicte Riber, 1960-, et al. (författare)
  • Both plant genotype and herbivory shape aspen endophyte communities
  • 2018
  • Ingår i: Oecologia. - : Springer. - 0029-8549 .- 1432-1939. ; 187:2, s. 535-545
  • Tidskriftsartikel (refereegranskat)abstract
    • Salicinoid phenolic glycosides are common defence substances in salicaceous trees and specialist leaf beetles use these compounds for their own defence against predators. Salicinoids vary qualitatively and qualitatively in aspen (Populus tremula) and this variation has a genetic basis. The foliar endophyte mycobiome is plentiful and we hypothesised that it is related to plant genotype, potentially mediated by salicinoid composition, and that interactions with the leaf beetle Chrysomela tremula may alter this relationship. We studied these three-way interactions in controlled greenhouse experiments. Endophytic fungi were isolated from sterilised leaf tissues with and without beetle damage, and from beetles. We confirmed that endophyte composition was influenced by host genotype. Beetle activity added generalist morphs to the mycobiome that overrode the initial host association. Yeast-like genera (Cryptococcus and Rhodotorula) were isolated only from beetle-damaged tissues and from beetles, whereas fast-growing filamentous fungi dominated beetle-free control plants. Competition experiments between filamentous fungi of plant origin and beetle-related yeasts suggested interaction of both stimulating and inhibiting modes of action amongst the fungi. As a result, we detected examples of amensalism, commensalism, parasitism and competition between the morphs tested, but we found no evidence of mutualism, and consequently no co-evolutionary relationship could be demonstrated, between yeasts carried by beetles, host genotype and associated filamentous morphs. Endophyte studies are method-dependent and high-throughput sequencing technology best define the fungal mycobiome, culturing however continues to be a cheap way to provide fundamental ecological insights and it is also required for experimental studies.
  •  
45.
  • Anderson, P, et al. (författare)
  • Within-plant variation in induced defence in developing leaves of cotton plants
  • 2005
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 1432-1939 .- 0029-8549. ; 144:3, s. 427-434
  • Tidskriftsartikel (refereegranskat)abstract
    • According to optimal defence theory (ODT) plants should invest in stronger defence in the most valuable parts, such as reproductive or young tissue. Cotton plants are known to express high resistance to herbivore feeding in the developing leaves at the top of the plant after herbivore-damage. Cotton plants also have developing leaves on side shoots from the nodes all along the plant. This allowed us to investigate within-plant distribution of defence between younger tissues at different locations on the plant. We found that all developing leaves showed increased resistance to feeding by larvae of the generalist moth Spodoptera littoralis after herbivore damage to leaves of the plant. An increase in the concentration of secondary compounds, terpenoid aldehydes, was found in developing leaves both at the top of the plant and on the side shoots. However, the resistance was stronger in the top leaves than in the side shoot leaves, showing that there is intra-plant variation in the induced response between different leaves of the same age. After the initial damage, larval feeding mainly occurred on the older, fully developed true leaves. Furthermore, the herbivore-induced resistance in the developing leaves reduced upward movement of feeding larvae on the plant and reduced the feeding on the upper parts of the plant over a period of at least 6 days. The plant thus benefits from defending all developing leaves by directing feeding to older, less valuable leaves and lower parts of the plant. The observed distribution of defence within cotton plants supports ODT.
  •  
46.
  • Andersson, Malte, 1941, et al. (författare)
  • Reproductive tactics under severe egg predation: an eider's dilemma.
  • 2006
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 148:2, s. 350-5
  • Tidskriftsartikel (refereegranskat)abstract
    • Parental defence against predators may increase offspring survival but entail other costs. Egg predation is frequent early in the laying sequence of the common eider, which differs in this and in several other ways from most other waterfowl. We test the hypothesis that permanent presence at the nest from the second or third egg is an adaptation for reducing egg predation in eiders. Two other alternative hypotheses for lower predation at later nest stages are early predation loss of the most vulnerable nests and seasonal decrease in predation risk. Analyses of predation rates at the one-egg and later stages refute these two alternatives. Early nest attendance by eider females is estimated to increase clutch survival by about 20% in four-egg and 35% in five-egg clutches, albeit probably at a cost of smaller clutch size.
  •  
47.
  • Andersson, Petter, et al. (författare)
  • Insect density-plant density relationships : a modified view of insect responses to resource concentrations
  • 2013
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 173:4, s. 1333-1344
  • Tidskriftsartikel (refereegranskat)abstract
    • Habitat area is an important predictor of spatial variation in animal densities. However, the area often correlates with the quantity of resources within habitats, complicating our understanding of the factors shaping animal distributions. We addressed this problem by investigating densities of insect herbivores in habitat patches with a constant area but varying numbers of plants. Using a mathematical model, predictions of scale-dependent immigration and emigration rates for insects into patches with different densities of host plants were derived. Moreover, a field experiment was conducted where the scaling properties of odour-mediated attraction in relation to the number of odour sources were estimated, in order to derive a prediction of immigration rates of olfactory searchers. The theoretical model predicted that we should expect immigration rates of contact and visual searchers to be determined by patch area, with a steep scaling coefficient, mu = -1. The field experiment suggested that olfactory searchers should show a less steep scaling coefficient, with mu a parts per thousand -0.5. A parameter estimation and analysis of published data revealed a correspondence between observations and predictions, and density-variation among groups could largely be explained by search behaviour. Aphids showed scaling coefficients corresponding to the prediction for contact/visual searchers, whereas moths, flies and beetles corresponded to the prediction for olfactory searchers. As density responses varied considerably among groups, and variation could be explained by a certain trait, we conclude that a general theory of insect responses to habitat heterogeneity should be based on shared traits, rather than a general prediction for all species.
  •  
48.
  • Andersson, Petter, et al. (författare)
  • Plant patch structure influences plant fitness via antagonistic and mutualistic interactions but in different directions
  • 2016
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 180:4, s. 1175-1182
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant patch structure and environmental context can influence the outcome of antagonistic and mutualistic plant-insect interactions, leading to spatially variable fitness effects for plants. We investigated the effects of herbivory and pollen limitation on plant reproductive performance in 28 patches of the self-compatible perennial herb Scrophularia nodosa and assessed how such effects varied with plant patch size, plant density and tree cover. Both antagonistic and mutualistic interactions had strong effects on plant reproductive performance. Leaf feeding from herbivores reduced both fruit production and seed germination, and leaf herbivory increased with plant patch size. Experimentally hand-pollinated flowers produced more seeds than open-pollinated flowers, and pollen limitation was more severe in patches with fewer plants. Our study on S. nodosa is one of few which documents that plant patch structure influences the outcome of both antagonistic and mutualistic plant-insect interactions. The results thus provide an example of how variation in plant patch structure and environmental factors can lead to spatially variable fitness effects from mutualistic and antagonistic interactions.
  •  
49.
  • Andreasson, Fredrik, et al. (författare)
  • Age-dependent effects of predation risk on night-time hypothermia in two wintering passerine species
  • 2019
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 189:2, s. 329-337
  • Tidskriftsartikel (refereegranskat)abstract
    • Small animals that winter at northern latitudes need to maximize energy intake and minimize energy loss. Many passerine birds use night-time hypothermia to conserve energy. A potential cost of night-time hypothermia with much theoretical (but little empirical) support is increased risk of night-time predation, due to reduced vigilance and lower escape speed in hypothermic birds. This idea has never been tested in the wild. We, therefore, increased perceived predation risk in great tits (Parus major) and blue tits (Cyanistes caeruleus) roosting in nest boxes during cold winter nights to measure any resultant effect on their use of night-time hypothermia. Roosting birds of both species that experienced their first winter were less prone to use hypothermia as an energy-saving strategy at low ambient temperatures when exposed to increased perceived predation risk either via handling (great tits) or via predator scent manipulation (blue tits). However, we did not record such effects in birds that were in their second winter or beyond. Our results suggest that effects of increased predation risk are age- and temperature specific. This could be caused by age-related differences in experience and subsequent risk assessment, or by dominance-related variation in habitat quality between young and old birds. Predation risk could, through its effect on use and depth of night-time hypothermia, be important for total energy management and winter survival for resident birds at northern latitudes.
  •  
50.
  • Andreasson, Fredrik, et al. (författare)
  • Variation in breeding phenology in response to climate change in two passerine species
  • 2023
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 201:1, s. 279-285
  • Tidskriftsartikel (refereegranskat)abstract
    • Increasingly warmer springs have caused phenological shifts in both plants and animals. In birds, it is well established that mean laying date has advanced to match the earlier food peak. We know less about changes in the distribution of egg-laying dates within a population and the environmental variables that determine this variation. This could be an important component of how populations respond to climate change. We, therefore, used laying date and environmental data from 39 years (1983–2021) to determine how climate change affected laying date variation in blue tits (Cyanistes caeruleus) and marsh tits (Poecile palustris), two sympatric passerines with different life histories. Both species advanced mean laying date (0.19–0.24 days per year) and mean laying date showed a negative relationship with maximum spring temperature in both blue and marsh tits. In springs with no clear temperature increase during the critical time window (the time-window in which mean laying date was most sensitive to temperature) start of breeding in blue tits was distributed over a longer part of the season. However, there was no such pattern in marsh tits. Our findings suggest that temperature change, and not necessarily absolute temperature, can shape the variation in breeding phenology in a species-specific manner, possibly linked to variation in life-history strategies. This is an important consideration when predicting how climate change affects timing of breeding within a population.
  •  
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