| 1. |
- Maes, S.L., et al.
(författare)
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Environmental drivers of increased ecosystem respiration in a warming tundra
- 2024
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 629:8010, s. 105-113
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Tidskriftsartikel (refereegranskat)abstract
- Arctic and alpine tundra ecosystems are large reservoirs of organic carbon. Climate warming may stimulate ecosystem respiration and release carbon into the atmosphere. The magnitude and persistency of this stimulation and the environmental mechanisms that drive its variation remain uncertain. This hampers the accuracy of global land carbon–climate feedback projections. Here we synthesize 136 datasets from 56 open-top chamber in situ warming experiments located at 28 arctic and alpine tundra sites which have been running for less than 1 year up to 25 years. We show that a mean rise of 1.4 °C [confidence interval (CI) 0.9–2.0 °C] in air and 0.4 °C [CI 0.2–0.7 °C] in soil temperature results in an increase in growing season ecosystem respiration by 30% [CI 22–38%] (n = 136). Our findings indicate that the stimulation of ecosystem respiration was due to increases in both plant-related and microbial respiration (n = 9) and continued for at least 25 years (n = 136). The magnitude of the warming effects on respiration was driven by variation in warming-induced changes in local soil conditions, that is, changes in total nitrogen concentration and pH and by context-dependent spatial variation in these conditions, in particular total nitrogen concentration and the carbon:nitrogen ratio. Tundra sites with stronger nitrogen limitations and sites in which warming had stimulated plant and microbial nutrient turnover seemed particularly sensitive in their respiration response to warming. The results highlight the importance of local soil conditions and warming-induced changes therein for future climatic impacts on respiration.
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| 2. |
- Mattila, S., et al.
(författare)
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A dust-enshrouded tidal disruption event with a resolved radio jet in a galaxy merger
- 2018
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 361:6401, s. 482-485
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Tidskriftsartikel (refereegranskat)abstract
- Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). We have observed a transient source in the western nucleus of the merging galaxy pair Arp 299 that radiated >1.5 × 1052erg at infrared and radio wavelengths but was not luminous at optical or x-ray wavelengths. We interpret this as a TDE with much of its emission reradiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the difference between theoretical predictions and observed luminosities of TDEs. The radio observations resolve an expanding and decelerating jet, probing the jet formation and evolution around a SMBH.
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| 3. |
- Kankare, E., et al.
(författare)
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Core-collapse supernova subtypes in luminous infrared galaxies
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 649
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Tidskriftsartikel (refereegranskat)abstract
- The fraction of core-collapse supernovae (CCSNe) occurring in the central regions of galaxies is not well constrained at present. This is partly because large-scale transient surveys operate at optical wavelengths, making it challenging to detect transient sources that occur in regions susceptible to high extinction factors. Here we present the discovery and follow-up observations of two CCSNe that occurred in the luminous infrared galaxy (LIRG) NGC 3256. The first, SN 2018ec, was discovered using the ESO HAWK-I /GRAAL adaptive optics seeing enhancer, and was classified as a Type Ic with a host galaxy extinction of AV = 2:1+0:3 0:1 mag. The second, AT 2018cux, was discovered during the course of follow-up observations of SN 2018ec, and is consistent with a subluminous Type IIP classification with an AV = 2:1 +/- 0:4 mag of host extinction. A third CCSN, PSN J10275082 4354034 in NGC 3256, was previously reported in 2014, and we recovered the source in late-time archival Hubble Space Telescope imaging. Based on template light curve fitting, we favour a Type IIn classification for it with modest host galaxy extinction of AV = 0:3+0:4 0:3 mag. We also extend our study with follow-up data of the recent Type IIb SN 2019lqo and Type Ib SN 2020fkb that occurred in the LIRG system Arp 299 with host extinctions of AV = 2:1 +0:1 0 :3 and AV = 0:4 +0:1 0 :2 mag, respectively. Motivated by the above, we inspected, for the first time, a sample of 29 CCSNe located within a projected distance of 2.5 kpc from the host galaxy nuclei in a sample of 16 LIRGs. We find, if star formation within these galaxies is modelled assuming a global starburst episode and normal IMF, that there is evidence of a correlation between the starburst age and the CCSN subtype. We infer that the two subgroups of 14 H-poor (Type IIb /Ib /Ic /Ibn) and 15 H-rich (Type II /IIn) CCSNe have di fferent underlying progenitor age distributions, with the H-poor progenitors being younger at 3 sigma significance. However, we note that the currently available sample sizes of CCSNe and host LIRGs are small, and the statistical comparisons between subgroups do not take into account possible systematic or model errors related to the estimated starburst ages.
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| 4. |
- Väisänen, P, et al.
(författare)
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Adaptive optics imaging and optical spectroscopy of a multiple merger in a luminous infrared galaxy
- 2008
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 384:3, s. 886-906
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Tidskriftsartikel (refereegranskat)abstract
- We present near-infrared (NIR) adaptive optics imaging obtained with VLT/NACO and optical spectroscopy from the Southern African Large Telescope of a luminous IR galaxy (LIRG) IRAS 19115-2124. These data are combined with archival Hubble Space Telescope imaging and Spitzer imaging and spectroscopy, allowing us to study this disturbed interacting/merging galaxy, dubbed the Bird, in extraordinary detail. In particular, the data reveal a triple system where the LIRG phenomenon is dominated by the smallest of the components. One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disc and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7 × 1010Msolarfor both. The third component appears to be a 1-2 × 1010Msolar mass irregular galaxy. The total system exhibits HII galaxy-like optical line ratios and strengths, and no evidence for active galactic nucleus (AGN) activity is found from optical or mid-IR data. The star formation rate is estimated to be ~190Msolaryr-1. We also report a search for supernovae from NIR images separated by five months and search for superstar cluster candidates. We detect outflowing gas from the Bird mostly in the range 100-300 km s-1 using NaI D absorption features. Overall, the Bird shows kinematic, dynamical and emission-line properties typical for cool ultraluminous IR galaxies (ULIRGs). However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation, as revealed by Spitzer imaging, does not come from the two major K-band nuclei, but from the third irregular component. This is in contrast to the conventional view that the (U)LIRG phases are powered by infalling gas to the major nuclei of the merging spiral galaxies. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components. Based on observations made with ESO Telescopes at the Paranal Observatory under programme 073.D-0406A, and with the Southern African Large Telescope (SALT).
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| 5. |
- Soininen, E.M., et al.
(författare)
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Location of studies and evidence of effects of herbivory on Arctic vegetation: a systematic map
- 2021
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Ingår i: Environmental Evidence. - : BioMed Central (BMC). - 2047-2382. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Herbivores modify the structure and function of tundra ecosystems. Understanding their impacts is necessary to assess the responses of these ecosystems to ongoing environmental changes. However, the effects of herbivores on plants and ecosystem structure and function vary across the Arctic. Strong spatial variation in herbivore effects implies that the results of individual studies on herbivory depend on local conditions, i.e., their ecological context. An important first step in assessing whether generalizable conclusions can be produced is to identify the existing studies and assess how well they cover the underlying environmental conditions across the Arctic. This systematic map aims to identify the ecological contexts in which herbivore impacts on vegetation have been studied in the Arctic. Specifically, the primary question of the systematic map was: “What evidence exists on the effects of herbivores on Arctic vegetation?”.Methods: We used a published systematic map protocol to identify studies addressing the effects of herbivores on Arctic vegetation. We conducted searches for relevant literature in online databases, search engines and specialist websites. Literature was screened to identify eligible studies, defined as reporting primary data on herbivore impacts on Arctic plants and plant communities. We extracted information on variables that describe the ecological context of the studies, from the studies themselves and from geospatial data. We synthesized the findings narratively and created a Shiny App where the coded data are searchable and variables can be visually explored.Review findings: We identified 309 relevant articles with 662 studies (representing different ecological contexts or datasets within the same article). These studies addressed vertebrate herbivory seven times more often than invertebrate herbivory. Geographically, the largest cluster of studies was in Northern Fennoscandia. Warmer and wetter parts of the Arctic had the largest representation, as did coastal areas and areas where the increase in temperature has been moderate. In contrast, studies spanned the full range of ecological context variables describing Arctic vertebrate herbivore diversity and human population density and impact.Conclusions: The current evidence base might not be sufficient to understand the effects of herbivores on Arctic vegetation throughout the region, as we identified clear biases in the distribution of herbivore studies in the Arctic and a limited evidence base on invertebrate herbivory. In particular, the overrepresentation of studies in areas with moderate increases in temperature prevents robust generalizations about the effects of herbivores under different climatic scenarios.
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| 6. |
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| 7. |
- Blom, Victoria, et al.
(författare)
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Lifestyle Habits and Mental Health in Light of the Two COVID-19 Pandemic Waves in Sweden, 2020
- 2021
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1660-4601 .- 1661-7827. ; 18:6
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Tidskriftsartikel (refereegranskat)abstract
- The COVID-19 pandemic has become a public health emergency of international concern, which may have affected lifestyle habits and mental health. Based on national health profile assessments, this study investigated perceived changes of lifestyle habits in response to the COVID-19 pandemic and associations between perceived lifestyle changes and mental health in Swedish working adults. Among 5599 individuals (50% women, 46.3 years), the majority reported no change (sitting 77%, daily physical activity 71%, exercise 69%, diet 87%, alcohol 90%, and smoking 97%) due to the pandemic. Changes were more pronounced during the first wave (April-June) compared to the second (October-December). Women, individuals <60 years, those with a university degree, white-collar workers, and those with unhealthy lifestyle habits at baseline had higher odds of changing lifestyle habits compared to their counterparts. Negative changes in lifestyle habits and more time in a mentally passive state sitting at home were associated with higher odds of mental ill-health (including health anxiety regarding one's own and relatives' health, generalized anxiety and depression symptoms, and concerns regarding employment and economy). The results emphasize the need to support healthy lifestyle habits to strengthen the resilience in vulnerable groups of individuals to future viral pandemics and prevent health inequalities in society.
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| 8. |
- Ekblom Bak, Elin, 1981-, et al.
(författare)
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Cardiorespiratory fitness and lifestyle on severe COVID-19 risk in 279,455 adults: a case control study
- 2021
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Ingår i: International Journal of Behavioral Nutrition and Physical Activity. - : Springer Science and Business Media LLC. - 1479-5868. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Background The impact of cardiorespiratory fitness (CRF) and other lifestyle-related factors on severe COVID-19 risk is understudied. The present study aims to investigate lifestyle-related and socioeconomic factors as possible predictors of COVID-19, with special focus on CRF, and to further study whether these factors may attenuate obesity- and hypertension-related risks, as well as mediate associations between socioeconomic factors and severe COVID-19 risk. Methods Out of initially 407,131 participants who participated in nationwide occupational health service screening between 1992 and 2020, n = 857 cases (70% men, mean age 49.9 years) of severe COVID-19 were identified. CRF was estimated using a sub-maximum cycle test, and other lifestyle variables were self-reported. Analyses were performed including both unmatched, n = 278,598, and sex-and age-matched, n = 3426, controls. Severe COVID-19 included hospitalization, intensive care or death due to COVID-19. Results Patients with more severe COVID-19 had significantly lower CRF, higher BMI, a greater presence of comorbidities and were more often daily smokers. In matched analyses, there was a graded decrease in odds for severe COVID-19 with each ml in CRF (OR = 0.98, 95% CI 0.970 to 0.998), and a two-fold increase in odds between the lowest and highest (< 32 vs. >= 46 ml center dot min(-1)center dot kg(-1)) CRF group. Higher BMI (per unit increase, OR = 1.09, 1.06 to 1.12), larger waist circumference (per cm, OR = 1.04, 1.02 to 1.06), daily smoking (OR = 0.60, 0.41 to 0.89) and high overall stress (OR = 1.36, 1.001 to 1.84) also remained significantly associated with severe COVID-19 risk. Obesity- and blood pressure-related risks were attenuated by adjustment for CRF and lifestyle variables. Mediation through CRF, BMI and smoking accounted for 9% to 54% of the associations between low education, low income and blue collar/low skilled occupations and severe COVID-19 risk. The results were consistent using either matched or unmatched controls. Conclusions Both lifestyle-related and socioeconomic factors were associated with risk of severe COVID-19. However, higher CRF attenuated the risk associated with obesity and high blood pressure, and mediated the risk associated with various socioeconomic factors. This emphasises the importance of interventions to maintain or increase CRF in the general population to strengthen the resilience to severe COVID-19, especially in high-risk individuals.
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| 9. |
- Kankare, E., et al.
(författare)
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DISCOVERY OF TWO SUPERNOVAE IN THE NUCLEAR REGIONS OF THE LUMINOUS INFRARED GALAXY IC 883
- 2012
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 744:2
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of two consecutive supernovae (SNe), 2010cu and 2011hi, located at 0 ''.37 (180 pc) and 0 ''.79 (380 pc) projected distance, respectively, from the center of the K-band nucleus of the luminous infrared galaxy (LIRG) IC 883. The SNe were discovered in an ongoing near-infrared K-band search for core-collapse SNe in such galaxies using the ALTAIR/NIRI adaptive optics system with laser guide star at the Gemini-North Telescope. These are thus the closest SNe yet discovered to an LIRG nucleus in optical or near-infrared wavelengths. The near-infrared light curves and colors of both SNe are consistent with core-collapse events. Both SNe seem to suffer from relatively low host galaxy extinction suggesting that regardless of their low projected galactocentric distances, they are not deeply buried in the nuclear regions of the host galaxy.
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| 10. |
- Mattila, Seppo, et al.
(författare)
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Adaptive Optics Discovery of Supernova 2004ip in the Nuclear Regions of the Luminous Infrared Galaxy IRAS 18293-3413
- 2007
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Ingår i: The Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 659:1, s. L9-L12
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Tidskriftsartikel (refereegranskat)abstract
- We report a supernova discovery in Ks-band images from the NAOS CONICA adaptive optics (AO) system on the ESO Very Large Telescope. The images were obtained as part of a near-infrared search for highly obscured supernovae in the nuclear regions of luminous and ultraluminous infrared galaxies. SN 2004ip is located within a circumnuclear starburst at 1.4" (or 500 pc) projected distance from the K-band nucleus of the luminous infrared galaxy IRAS 18293-3413. The supernova luminosity and light curve are consistent with a core-collapse event suffering from a host galaxy extinction of up to about 40 mag in the V band, which is as expected for a circumnuclear starburst environment. This is the first supernova to be discovered making use of AO correction and demonstrates the potential of the current 8 m-class telescopes equipped with AO in discovering supernovae from the innermost nuclear regions of luminous and ultraluminous infrared galaxies.
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| 11. |
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| 12. |
- Monteux, Sylvain, 1989-, et al.
(författare)
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Controlling biases in targeted plant removal experiments
- 2024
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Ingår i: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 242:4, s. 1835-1845
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Tidskriftsartikel (refereegranskat)abstract
- Targeted removal experiments are a powerful tool to assess the effects of plant species or (functional) groups on ecosystem functions. However, removing plant biomass in itself can bias the observed responses. This bias is commonly addressed by waiting until ecosystem recovery, but this is inherently based on unverified proxies or anecdotal evidence. Statistical control methods are efficient, but restricted in scope by underlying assumptions.We propose accounting for such biases within the experimental design, using a gradient of biomass removal controls. We demonstrate the relevance of this design by presenting (1) conceptual examples of suspected biases and (2) how to observe and control for these biases.Using data from a mycorrhizal association-based removal experiment, we show that ignoring biomass removal biases (including by assuming ecosystem recovery) can lead to incorrect, or even contrary conclusions (e.g. false positive and false negative). Our gradient design can prevent such incorrect interpretations, regardless of whether aboveground biomass has fully recovered.Our approach provides more objective and quantitative insights, independently assessed for each variable, than using a proxy to assume ecosystem recovery. Our approach circumvents the strict statistical assumptions of, for example, ANCOVA and thus offers greater flexibility in data analysis.
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| 13. |
- Thierry, Dominique, et al.
(författare)
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Long-term atmospheric corrosion of Zn–5%Al-coated steel and HDG during outdoor worldwide exposures
- 2020
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Ingår i: Corrosion Engineering, Science and Technology. - : Taylor and Francis Ltd.. - 1478-422X .- 1743-2782. ; 55:7, s. 520-530
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Tidskriftsartikel (refereegranskat)abstract
- Hot-dipped galvanised (HDG) steel and Zn5Al-coated steel were exposed for 6 years at different atmospheric weathering sites worldwide. The mass loss of the coatings has been measured after 1, 2, 4 and 6 years of exposure. In addition, corrosion products have been determined using scanning electron microscopy, X-ray diffraction and FTIR spectroscopy. It is shown that Zn5Al is better than HDG-steel independently on the exposure duration and location. The mass loss of Zn5Al is also less dependent of the environmental parameters (such as chloride deposition, relative humidity and temperature) than HDG-steel. The ratio of performance after 6 years of exposure varied from 1.3 to 5.1 with the mean value of 3.1. The analyses of the corrosion products indicate the formation of protective Zn/Al - (Formula presented.) layered double hydroxide (LDH) and sulphate-containing corrosion products of Zn and Al after 6 years of exposure. A mechanism explaining the superior properties of Zn5Al is proposed.
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