| 1. |
- Ahlberg, Erik, et al.
(författare)
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"Vi klimatforskare stödjer Greta och skolungdomarna"
- 2019
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Ingår i: Dagens nyheter (DN debatt). - 1101-2447.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- DN DEBATT 15/3. Sedan industrialiseringens början har vi använt omkring fyra femtedelar av den mängd fossilt kol som får förbrännas för att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det är bråttom att kraftigt reducera utsläppen. Det har Greta Thunberg och de strejkande ungdomarna förstått. Därför stödjer vi deras krav, skriver 270 klimatforskare.
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| 2. |
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| 3. |
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| 4. |
- Martinsson, Johan, et al.
(författare)
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Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol
- 2015
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:24, s. 14663-14671
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Angstrom exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.
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| 5. |
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| 6. |
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| 7. |
- Nilsson, Lovisa, et al.
(författare)
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Relating the single particle soot photometer (SP2) signal response to soot maturity
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Ingår i: Aerosol Science and Technology. - 1521-7388.
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Tidskriftsartikel (refereegranskat)abstract
- Light absorbing carbonaceous aerosols produced from combustion span over a range of physicochemical properties. Soot is the most recognized species in this category and its formation process involves gradual maturation from amorphous young soot with a high hydrogen-to-carbon-ratio toward mature soot aggregates. In this work, the optical response of a single particle soot photometer (SP2) to electrical mobility size selected soot of different maturity produced by a mini-CAST soot generator is investigated. The results show that for soot of a specific mobility diameter, the laser-induced incandescence (LII) signal appears earlier and with a higher LII peak height for increasing soot maturity. The experimental observations are supported by simulations using a numerical model for the LII process. Furthermore, the effect of systematically varying the SP2 laser power on the detection of soot of different maturity using LII is explored. This work can be seen as a step toward the aim of using the SP2 instrument to identify soot particles of different maturity in the atmosphere.
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| 8. |
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| 9. |
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| 10. |
- Ahlberg, Erik, et al.
(författare)
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Measurement report : Black carbon properties and concentrations in southern Sweden urban and rural air-the importance of long-range transport
- 2023
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 23:5, s. 3051-3064
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Tidskriftsartikel (refereegranskat)abstract
- Soot, or black carbon (BC), aerosol is a major climate forcer with severe health effects. The impacts depend strongly on particle number concentration, size and mixing state. This work reports on two field campaigns at nearby urban and rural sites, 65gkm apart, in southern Sweden during late summer 2018. BC was measured using a single-particle soot photometer (SP2) and Aethalometers (AE33). Differences in BC concentrations between the sites are driven primarily by local traffic emissions. Equivalent and refractory BC mass concentrations at the urban site were on average a factor 2.2 and 2.5, with peaks during rush hour up to a factor g1/44, higher than the rural background levels. The number fraction of particles containing a soot core was significantly higher in the city. BC particles at the urban site were on average smaller by mass and had less coating owing to fresh traffic emissions. The organic components of the fresh traffic plumes were similar in mass spectral signature to hydrocarbon-like organic aerosol (HOA), commonly associated with traffic. Despite the intense local traffic (g1/4g30g000 vehicles passing per day), PM1, including organic aerosol, was dominated by aged continental air masses even at the curbside site. The fraction of thickly coated particles at the urban site was highly correlated with the mass concentrations of all measured chemical species of PM1, consistent with aged, internally mixed aerosol. Trajectory analysis for the whole year showed that air masses arriving at the rural site from eastern Europe contained approximately double the amount of BC compared to air masses from western Europe. Furthermore, the largest regional emissions of BC transported to the rural site, from the Malmö-Copenhagen urban area, are discernible above background levels only when precipitation events are excluded. We show that continental Europe and not the Malmö-Copenhagen region is the major contributor to the background BC mass concentrations in southern Sweden.
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| 11. |
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| 12. |
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| 13. |
- Martinsson, Johan, et al.
(författare)
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Carbonaceous aerosol source apportionment using the Aethalometer model - evaluation by radiocarbon and levoglucosan analysis at a rural background site in southern Sweden
- 2017
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:6, s. 4265-4281
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Tidskriftsartikel (refereegranskat)abstract
- With the present demand on fast and inexpensive aerosol source apportionment methods, the Aethalometer model was evaluated for a full seasonal cycle (June 2014June 2015) at a rural atmospheric measurement station in southern Sweden by using radiocarbon and levoglucosan measurements. By utilizing differences in absorption of UV and IR, the Aethalometer model apportions carbon mass into wood burning (WB) and fossil fuel combustion (FF) aerosol. In this study, a small modification in the model in conjunction with carbon measurements from thermal-optical analysis allowed apportioned non-light-absorbing biogenic aerosol to vary in time. The absorption differences between WB and FF can be quantified by the absorption angstrom ngstrom exponent (AAE). In this study AAE(WB) was set to 1.81 and AAE(FF) to 1.0. Our observations show that the AAE was elevated during winter (1.36 +/- 0.07) compared to summer (1.12 +/- 0.07). Quantified WB aerosol showed good agreement with levoglucosan concentrations, both in terms of correlation (R-2 = 0 : 70) and in comparison to reference emission inventories. WB aerosol showed strong seasonal variation with high concentrations during winter (0.65 mu gm(-3), 56% of total carbon) and low concentrations during summer (0.07 mu gm(-3), 6% of total carbon). FF aerosol showed less seasonal dependence; however, black carbon (BC) FF showed clear diurnal patterns corresponding to traffic rush hour peaks. The presumed non-light-absorbing biogenic carbonaceous aerosol concentration was high during summer (1.04 mu gm(-3), 72% of total carbon) and low during winter (0.13 mu gm(-3), 8% of total carbon). Aethalometer model results were further compared to radiocarbon and levoglucosan source apportionment results. The comparison showed good agreement for apportioned mass of WB and biogenic carbonaceous aerosol, but discrepancies were found for FF aerosol mass. The Aethalometer model overestimated FF aerosol mass by a factor of 1.3 compared to radiocarbon and levoglucosan source apportionment. A performed sensitivity analysis suggests that this discrepancy can be explained by interference of non-light-absorbing biogenic carbon during winter. In summary, the Aethalometer model offers a costeffective yet robust high-time-resolution source apportionment at rural background stations compared to a radiocarbon and levoglucosan alternative.
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| 14. |
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| 15. |
- Ringaby, Erik, et al.
(författare)
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Co-aligning Aerial Hyperspectral Push-broom Strips for Change Detection
- 2010
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Ingår i: Proc. SPIE 7835, Electro-Optical Remote Sensing, Photonic Technologies, and Applications IV. - : SPIE - International Society for Optical Engineering. - 9780819483539 ; , s. Art.nr. 7835B-36-
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Konferensbidrag (refereegranskat)abstract
- We have performed a field trial with an airborne push-broom hyperspectral sensor, making several flights over the same area and with known changes (e.g., moved vehicles) between the flights. Each flight results in a sequence of scan lines forming an image strip, and in order to detect changes between two flights, the two resulting image strips must be geometrically aligned and radiometrically corrected. The focus of this paper is the geometrical alignment, and we propose an image- and gyro-based method for geometric co-alignment (registration) of two image strips. The method is particularly useful when the sensor is not stabilized, thus reducing the need for expensive mechanical stabilization. The method works in several steps, including gyro-based rectification, global alignment using SIFT matching, and a local alignment using KLT tracking. Experimental results are shown but not quantified, as ground truth is, by the nature of the trial, lacking.
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| 16. |
- Ringaby, Erik, et al.
(författare)
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Co-alignmnent of Aerial Push-broom Strips using Trajectory Smoothness Constraints
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We study the problem of registering a sequence of scan lines (a strip) from an airborne push-broom imager to another sequence partly covering the same area. Such a registration has to compensate for deformations caused by attitude and speed changes in the aircraft. The registration is challenging, as both strips contain such deformations. Our algorithm estimates the 3D rotation of the camera for each scan line, by parametrising it as a linear spline with a number of knots evenly distributed in one of the strips. The rotations are estimated from correspondences between strips of the same area. Once the rotations are known, they can be compensated for, and each line of pixels can be transformed such that ground trace of the two strips are registered with respect to each other.
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| 17. |
- Abera, Asmamaw, et al.
(författare)
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Air pollution measurements and land-use regression in urban sub-saharan Africa using low-cost sensors—possibilities and pitfalls
- 2020
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Air pollution is recognized as the most important environmental factor that adversely affects human and societal wellbeing. Due to rapid urbanization, air pollution levels are increasing in the Sub-Saharan region, but there is a shortage of air pollution monitoring. Hence, exposure data to use as a base for exposure modelling and health effect assessments is also lacking. In this study, low-cost sensors were used to assess PM2.5 (particulate matter) levels in the city of Adama, Ethiopia. The measurements were conducted during two separate 1-week periods. The measurements were used to develop a land-use regression (LUR) model. The developed LUR model explained 33.4% of the variance in the concentrations of PM2.5. Two predictor variables were included in the final model, of which both were related to emissions from traffic sources. Some concern regarding influential observations remained in the final model. Long-term PM2.5 and wind direction data were obtained from the city’s meteorological station, which should be used to validate the representativeness of our sensor measurements. The PM2.5 long-term data were however not reliable. Means of obtaining good reference data combined with longer sensor measurements would be a good way forward to develop a stronger LUR model which, together with improved knowledge, can be applied towards improving the quality of health. A health impact assessment, based on the mean level of PM2.5 (23 µg/m3), presented the attributable burden of disease and showed the importance of addressing causes of these high ambient levels in the area.
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| 18. |
- Ahlberg, Daniel, 1982, et al.
(författare)
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Noise sensitivity in continuum percolation
- 2014
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Ingår i: Israel Journal of Mathematics. - : Springer Science and Business Media LLC. - 0021-2172 .- 1565-8511. ; 201:2, s. 847-899
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Tidskriftsartikel (refereegranskat)abstract
- We prove that the Poisson Boolean model, also known as the Gilbert disc model, is noise sensitive at criticality. This is the first such result for a Continuum Percolation model, and the first which involves a percolation model with critical probability pc not equal 1/2. Our proof uses a version of the Benjamini-Kalai-Schramm Theorem for biased product measures. A quantitative version of this result was recently proved by Keller and Kindler. We give a simple deduction of the non-quantitative result from the unbiased version. We also develop a quite general method of approximating Continuum Percolation models by discrete models with pc bounded away from zero; this method is based on an extremal result on non-uniform hypergraphs.
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| 19. |
- Ahlberg, Erik, et al.
(författare)
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Effect of salt seed particle surface area, composition and phase on secondary organic aerosol mass yields in oxidation flow reactors
- 2019
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:4, s. 2701-2712
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric particulate water is ubiquitous, affecting particle transport and uptake of gases. Yet, research on the effect of water on secondary organic aerosol (SOA) mass yields is not consistent. In this study, the SOA mass yields of an α-pinene and m-xylene mixture, at a concentration of 60 μgm-3, were examined using an oxidation flow reactor operated at a relative humidity (RH) of 60% and a residence time of 160 s. Wet or dried ammonium sulfate and ammonium nitrate seed particles were used. By varying the amount of seed particle surface area, the underestimation of SOA formation induced by the short residence time in flow reactors was confirmed. Starting at a SOA mass concentration of 5 μgm-3, the maximum yield increased by a factor of 2 with dry seed particles and on average a factor of 3.2 with wet seed particles. Hence, wet particles increased the SOA mass yield by 60% compared to the dry experiment. Maximum yield in the reactor was achieved using a surface area concentration of 1600 μm2 cm-3. This corresponded to a condensational lifetime of 20 s for low-volatility organics. The O V C ratio of SOA on wet ammonium sulfate was significantly higher than when using ammonium nitrate or dry ammonium sulfate seed particles, probably due to differences in heterogeneous chemistry.
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| 20. |
- Ahlberg, Erik, et al.
(författare)
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No particle mass enhancement from induced atmospheric ageing at a rural site in northern Europe
- 2019
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- A large portion of atmospheric aerosol particles consists of secondary material produced by oxidation reactions. The relative importance of secondary organic aerosol (SOA) can increase with improved emission regulations. A relatively simple way to study potential particle formation in the atmosphere is by using oxidation flow reactors (OFRs) which simulate atmospheric ageing. Here we report on the first ambient OFR ageing experiment in Europe, coupled with scanning mobility particle sizer (SMPS), aerosol mass spectrometer (AMS) and proton transfer reaction (PTR)-MS measurements. We found that the simulated ageing did not produce any measurable increases in particle mass or number concentrations during the two months of the campaign due to low concentrations of precursors. Losses in the reactor increased with hydroxyl radical (OH) exposure and with increasing difference between ambient and reactor temperatures, indicating fragmentation and evaporation of semivolatile material.
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| 21. |
- Ahlberg, Erik, et al.
(författare)
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Secondary organic aerosol from VOC mixtures in an oxidation flow reactor
- 2017
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 161, s. 210-220
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Tidskriftsartikel (refereegranskat)abstract
- The atmospheric organic aerosol is a tremendously complex system in terms of chemical content. Models generally treat the mixtures as ideal, something which has been questioned owing to model-measurement discrepancies. We used an oxidation flow reactor to produce secondary organic aerosol (SOA) mixtures containing oxidation products of biogenic (α-pinene, myrcene and isoprene) and anthropogenic (m-xylene) volatile organic compounds (VOCs). The resulting volume concentration and chemical composition was measured using a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), respectively. The SOA mass yield of the mixtures was compared to a partitioning model constructed from single VOC experiments. The single VOC SOA mass yields with no wall-loss correction applied are comparable to previous experiments. In the mixtures containing myrcene a higher yield than expected was produced. We attribute this to an increased condensation sink, arising from myrcene producing a significantly higher number of nucleation particles compared to the other precursors. Isoprene did not produce much mass in single VOC experiments but contributed to the mass of the mixtures. The effect of high concentrations of isoprene on the OH exposure was found to be small, even at OH reactivities that previously have been reported to significantly suppress OH exposures in oxidation flow reactors. Furthermore, isoprene shifted the particle size distribution of mixtures towards larger sizes, which could be due to a change in oxidant dynamics inside the reactor.
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| 22. |
- Ahlberg, Erik
(författare)
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Speeding up the Atmosphere : Experimental oxidation studies of ambient and laboratory aerosols using a flow reactor
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Apart from gases, the air we breath consist of tiny, so called, aerosol particles. A cubic metre of air in a relatively clean environment can consist of several billion aerosol particles. The impact of these particles on human health and on climate is significant. According to WHO, particles affect more humans than any other pollutant, and is closely related to mortality and morbidity. Further, it has been estimated that anthropogenic particles have cooled the climate, masking up to 50% of the warming caused by greenhouse gases. A large portion of the smallest particles consists of organic compounds, much of which is formed by atmospheric oxidation reactions. This material is called secondary organic aerosol (SOA). In this thesis, submicron secondary aerosol particles have been investigated using an oxidation flow reactor (OFR). Inside the reactor, large concentrations of oxidants produce secondary particulate material in a matter of minutes, thereby speeding up the naturally occuring atmospheric processes.In two laboratory studies, we have investigated the effect of mixing anthropogenic primary and secondary particles with biogenic SOA. In line with expectations, the anthropogenic and biogenic organic precursors mixed, and, in a non-linear way, formed more particulate mass than would otherwise be the case. Further, the effect of wet anthropogenic salt particles on SOA formation was investigated. The produced SOA mass in the presence of wet particles was significantly higher than if the particles were dry. This effect is believed to be very important in the atmosphere since water is always present. In both these studies it was shown that the SOA mass formed in OFRs at low particle mass concentrations, is underestimated due to the limited time for condensation of vapours in the reactor.In a separate study, the SOA formation from biomass burning was investigated. Biogenic SOA dominates on a global scale, but very high concentrations are only formed in the proximity of anthropogenic sources. It was shown that SOA formation from the emissions of a modern wood stove can be large enough to dominate over the primary particle emissions. To estimate the secondary particle formation potential of ambient air, two field studies were performed. In both studies, the simulated atmospheric processing of the background air did not produce much secondary particle mass. From this, it can be concluded that the chosen measurement sites were relatively clean, but the results also point to the efficiency of atmospheric processing. However, in one of the studies, targeting ship emissions at a coastal site, plumes of secondary material, of the same magnitude as the background aerosol particle concentration, was formed. This demonstrates the importance of considering atmospheric processing and the advantage of using OFRs in field studies.The relative importance of SOA in the atmospheric aerosol is believed to increase in the future. Due to complex feedbacks and the many variables affecting SOA formation, it is difficult to parameterize in a simple enough manner fit for global models. Both detailed and large-scale processes needs further investigation to improve estimations of SOA radiative forcing and the anthropogenic effect on biogenic SOA. The popularity of oxidation flow reactors in SOA research is likely to increase. The five original research manuscripts included in this thesis contributes specifically to the OFR research community, but also to improved understanding of SOA formation in the the anthropocene in general.
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| 23. |
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| 24. |
- Ahlberg, Martina, et al.
(författare)
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Reversed interface effects in amorphous FeZr/AlZr multilayers
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 90:18, s. 184403-
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Tidskriftsartikel (refereegranskat)abstract
- We report an anomalous enhancement of the critical temperature (T-c) when the thickness (d) of the magnetic layer is decreased from 60 to 20 angstrom in amorphous FeZr/AlZr multilayers. Further reduction of the thickness causes a decrease of T-c, as expected by finite-size scaling, while the magnetic moment decreases monotonically for all values of d. The increase of the critical temperature is attributed to a reversed interface effect where local changes in the nearest-neighbor distance and coordination number gives a higher effective magnetic coupling at the interfaces compared to the interior of the layer. We have successfully described the results within a model where such interface effects are combined with finite-size scaling.
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| 25. |
- Ahlberg, Mats Steinholtz, et al.
(författare)
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Time without PSA recurrence after radical prostatectomy as a predictor of future biochemical recurrence, metastatic disease and prostate cancer death : a prospective Scandinavian cohort study
- 2022
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Ingår i: BMJ Open. - : BMJ Publishing Group Ltd. - 2044-6055. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Although surveillance after radical prostatectomy routinely includes repeated prostate specific antigen (PSA)-testing for many years, biochemical recurrence often occurs without further clinical progression. We therefore hypothesised that follow-up can be shortened for many patients without increasing the risk of prostate cancer death. We investigated the long-term probabilities of PSA recurrence, metastases and prostate cancer death in patients without biochemical recurrence five and 10 years after radical prostatectomy.Design: Prospective cohort study. Stratification by Gleason score (<= 3+4=7or >= 4+3=7), pathological tumour stage (pT2 or >= pT3) and negative or positive surgical margins.Setting: Between 1989 and 1998, 14 urological centres in Scandinavia randomised patients to the Scandinavian Prostate Cancer Group study number 4 (SPCG-4) trial.ParticipationAll 306 patients from the SPCG-4 trial who underwent radical prostatectomy within 1year from inclusion were eligible. Four patients were excluded due to surgery-related death (n=1) or salvage radiotherapy or hormonal treatment within 6weeks from surgery (n=3).Primary outcome measures: Cumulative incidences and absolute differences in metastatic disease and prostate cancer death.Results: We analysed 302 patients with complete follow-up during a median of 24 years. Median preoperative PSA was 9.8ng/mL and median age was 65 years. For patients without biochemical recurrence 5 years after radical prostatectomy the 20-year probability of biochemical recurrence was 25% among men with Gleason score <= 3+4=7and 57% among men with Gleason score >= 4+3=7; the probabilities for metastases were 0.8% and 17%; and for prostate cancer death 0.8% and 12%, respectively. The long-term probabilities were higher for pT >= 3versus pT2 and for positive versus negative surgical margins. Limitations include small size of the cohort.Conclusion: Many patients with favourable histopathology without biochemical recurrence 5years after radical prostatectomy could stop follow-up earlier than 10 years after radical prostatectomy.
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| 26. |
- Ahlberg, Per Erik
(författare)
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Glimpsing the hidden majority
- 1990
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 344, s. 23-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 27. |
- Ahlberg, Per Erik, 1963-
(författare)
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Humeral homology and the origin of the tetrapod elbow : a reinterpretation of the enigmatic specimens ANSP 21350 and GSM 104536
- 2011
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Ingår i: Studies on fossil tetrapods. - London : The Palaeontological Association. - 9781444361896 ; , s. 17-29
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Bokkapitel (refereegranskat)abstract
- Two putative tetrapod humeri of Devonian age, ANSP 21350 from the late Famennian of Pennsylvania and GSM 104536 from the late Frasnian of Scat Craig, Scotland, are reinterpreted in the light of more recent discoveries. The morphology of ANSP 21350 can be more fully homologized with those of elpistostegids and early tetrapods than previously recognized. Unique features include distally displaced dorsal muscle attachments and a ventrally rotated distal face of the bone. This suggests that a weight-bearing ventrally directed forearm was created, not by means of a flexed elbow as in other tetrapods, but by distorting the humerus. The olecranon process on the ulna was probably poorly developed or absent. Primitive characters that are absent in other tetrapods add support to the contention that ANSP 21350 is the least crownward of known tetrapod humeri. Contrary to previous claims, Acanthostega has a characteristic tetrapod ulnar morphology with an olecranon process; it does not resemble an elpistostegid ulna and is not uniquely primitive for tetrapods. This suggests that the flexed tetrapod elbow with ulnar extensor muscles attached to the olecranon evolved simultaneously with the large rectangular entepicondyle typical for early tetrapods, probably as part of a single functional complex. GSM 104536 is denfinitely not a primitive tetrapod humerus, nor a sarcopterygian branchial bone, but cannot be positively identified at present.
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| 28. |
- Ahlberg, Per Erik, 1963-, et al.
(författare)
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Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires
- 2009
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 460:7257, s. 888-889
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Tidskriftsartikel (refereegranskat)abstract
- Recent finds(1,2) demonstrate that internal fertilization and viviparity (live birth) were more widespread in the Placodermi, an extinct group of armoured fishes, than was previously realized. Placoderms represent the sister group of the crown group jawed vertebrates (Gnathostomata)(3,4), making their mode(s) of reproduction potentially informative about primitive gnathostome conditions. An ossified pelvic fin basipterygium discovered in the arthrodire Incisoscutum ritchiei was hypothesized to be identical in males and females, with males presumed to have an additional cartilaginous element or series forming a clasper. Here we report the discovery of a completely ossified pelvic clasper in Incisoscutum ritchiei (WAM 03.3.28) which shows that this interpretation was incorrect: the basipterygium described previously(1) is in fact unique to females. The male clasper is a slender rod attached to a square basal plate that articulates directly with the pelvis. It carries a small cap of dermal bone covered in denticles and small hooks that may be homologous with the much larger dermal component of the ptyctodont clasper.
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| 29. |
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| 30. |
- Ahlgren, Björn, et al.
(författare)
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Testing a model for subphotospheric dissipation in GRBs: fits to Fermi data constrain the dissipation scenario
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 485, s. 474-497
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that the prompt emission in gamma-ray bursts (GRBs) could be described by radiation from the photosphere in a hot fireball. Such models must be tested by directly fitting them to data. In this work we use data from the Fermi Gamma-ray Space Telescope and consider a specific photospheric model, in which the kinetic energy of a low-magnetization outflow is dissipated locally by internal shocks below the photosphere. We construct a table model with a physically motivated parameter space and fit it to time-resolved spectra of the 36 brightest Fermi GRBs with a known redshift. We find that about two-thirds of the examined spectra cannot be described by the model, as it typically underpredicts the observed flux. However, since the sample is strongly biased towards bright GRBs, we argue that this fraction will be significantly lowered when considering the full population. From the successful fits we find that the model can reproduce the full range of spectral slopes present in the sample. For these cases we also find that the dissipation consistently occurs at a radius of ∼1012 cm and that only a few per cent efficiency is required. Furthermore, we find a positive correlation between the fireball luminosity and the Lorentz factor. Such a correlation has been previously reported by independent methods. We conclude that if GRB spectra are due to photospheric emission, the dissipation cannot only be the specific scenario we consider here.
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| 31. |
- Ausmeel, Stina, et al.
(författare)
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Methods for identifying aged ship plumes and estimating contribution to aerosol exposure downwind of shipping lanes
- 2019
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 12:8, s. 4479-4493
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Tidskriftsartikel (refereegranskat)abstract
- Ship traffic is a major source of aerosol particles, particularly near shipping lanes and harbours. In order to estimate the contribution to exposure downwind of a shipping lane, it is important to be able to measure the ship emission contribution at various distances from the source. We report on measurements of atmospheric particles 7-20 km downwind of a shipping lane in the Baltic Sea Sulfur Emission Control Area (SECA) at a coastal location in southern Sweden during a winter and a summer campaign. Each ship plume was linked to individual ship passages using a novel method based on wind field data and automatic ship identification system data (AIS), where varying wind speeds and directions were applied to calculate a plume trajectory. In a situation where AIS data are not matching measured plumes well or if AIS data are missing, we provide an alternative method with particle number concentration data. The shipping lane contribution to the particle number concentration in Falsterbo was estimated by subtracting background concentrations from the ship plume concentrations, and more than 150 plumes were analysed. We have also extrapolated the contribution to seasonal averages and provide recommendations for future similar measurements. Averaged over a season, the contribution to particle number concentration was about 18 % during the winter and 10 % during the summer, including those periods with wind directions when the shipping lane was not affecting the station. The corresponding contribution to equivalent black carbon was 1.4 %..
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| 32. |
- Ausmeel, Stina, et al.
(författare)
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Ship plumes in the Baltic Sea Sulfur Emission Control Area: chemical characterization and contribution to coastal aerosol concentrations
- 2020
-
Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 20:15, s. 9135-9151
-
Tidskriftsartikel (refereegranskat)abstract
- In coastal areas, there is increased concern aboutemissions from shipping activities and the associated impacton air quality. We have assessed the ship aerosol propertiesand the contribution to coastal particulate matter (PM) andnitrogen dioxide (NO2) levels by measuring ship plumes inambient conditions at a site in southern Sweden, within a SulfurEmission Control Area. Measurements took place duringa summer and a winter campaign, 10 km downwind ofa major shipping lane. Individual ships showed large variabilityin contribution to total particle mass, organics, sulfate,and NO2. The average emission contribution of theshipping lane was 2913 and 3720 ngm?3 to PM0:5,188 and 3419 ngm?3 to PM0:15, and 1:210:57 and1:110:61 μgm?3 to NO2, during winter and summer, respectively.Sulfate and organics dominated the particle massand most plumes contained undetectable amounts of equivalentblack carbon (eBC). The average eBC contribution was3:51:7 ngm?3 and the absorption Ångström exponent wasclose to 1. Simulated ageing of the ship aerosols using anoxidation flow reactor showed that on a few occasions, therewas an increase in sulfate and organic mass after photochemicalprocessing of the plumes. However, most plumes did notproduce measurable amounts of secondary PM upon simulatedageing.
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| 33. |
- Bergfelt, Emma, et al.
(författare)
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Satisfactory outcome after intensive chemotherapy with pragmatic use of minimal residual disease (MRD) monitoring in older patients with Philadelphia-negative B cell precursor acute lymphoblastic leukaemia : a Swedish registry-based study
- 2015
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Ingår i: Medical Oncology. - : Springer Science and Business Media LLC. - 1357-0560 .- 1559-131X. ; 32:4
-
Tidskriftsartikel (refereegranskat)abstract
- The introduction of minimal residual disease (MRD) monitoring, in the Swedish national guidelines for acute lymphoblastic leukaemia, was evaluated in 35 patients aged 46-79 years (median 61), who were diagnosed from 2007 to 2011 and treated with high-intensity, block-based chemotherapy (ABCDV/VABA induction). Both a high complete remission rate (91 %) and acceptable overall survival (OS) rate (47 %) at 5 years were achieved. MRD by flow cytometry was measured in 73 % of the patients reaching complete remission after the first course, but was omitted by the clinicians for eight patients who were either over 70 years of age or already met conventional high-risk criteria. Factors negatively influencing OS were age over 65 years and WHO status >= 2. MRD < 0.1 % after induction had positive impact on continuous complete remission but not on OS. Only five patients were allocated to allogeneic haematopoietic stem cell transplantation in first remission, mainly due to conventional high risk factors. Thus, use of intensive remission induction therapy is effective in a selection of older patients. In a population for whom the possibilities of treatment escalation are limited, the optimal role of MRD monitoring remains to be determined.
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| 34. |
- Björklund, Elisabet, et al.
(författare)
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Quality control of flow cytometry data analysis for evaluation of minimal residual disease in bone marrow from acute leukemia patients during treatment.
- 2009
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Ingår i: Journal of pediatric hematology/oncology : official journal of the American Society of Pediatric Hematology/Oncology. - : Lippincott Williams & Wilkins. - 1536-3678 .- 1077-4114. ; 31:6, s. 406-15
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Tidskriftsartikel (refereegranskat)abstract
- Low levels of leukemia cells in the bone marrow, minimal residual disease (MRD), are considered to be a powerful indicator of treatment response in acute lymphatic leukemia (ALL). A Nordic quality assurance program, aimed on standardization of the flow cytometry MRD analysis, has been established before implementation of MRD at cutoff level 10 as one of stratifying parameters in next Nordic Society of Pediatric Hematology and Oncology (NOPHO) treatment program for ALL. In 4 quality control (QC) rounds 15 laboratories determined the MRD levels in 48 follow-up samples from 12 ALL patients treated according to NOPHO 2000. Analysis procedures were standardized. For each QC round a compact disc containing data in list-mode files was sent out and results were submitted to a central laboratory. At cutoff level 10, which will be applied for clinical decisions, laboratories obtained a high concordance (91.6%). If cutoff level 10 was applied, the concordance would be lower (85.3%). The continuing standardization resulted in better concordance in QC3 and QC4 compared with QC1 and QC2. The concordance was higher in precursor B as compared with T-cell ALL. We conclude that after standardization, flow cytometry MRD detection can be reliably applied in international, multicenter treatment protocols.
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| 35. |
- Blom, Henning, et al.
(författare)
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Devonian vertebrates from East Greenland : a review of faunal composition and distribution
- 2007
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Ingår i: Geodiversitas. - 1280-9659 .- 1638-9395. ; 29:1, s. 119-141
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Forskningsöversikt (refereegranskat)abstract
- The Devonian vertebrate faunas of East Greenland are reviewed and their distribution discussed for the first time in the light of the most recently published stratigraphical framework for the area. The predominantly Middle and Upper Devonian continental sediments have yielded representatives of most major groups of early fossil vertebrates, including heterostracans, placoderms, acanthodians, chondrichthyans, actinopterygians, lungfishes, porolepiforms, "osteolepiforms" and tetrapods, but to date, no single publication has treated them all in their stratigraphical context. We therefore attempt to place them into the most recent, formalised lithostratigraphy, providing improved resolution for their stratigraphical distribution, as a basis for comparing East Greenland with other Devonian faunal successions worldwide. The review highlights the fact that many problems of stratigraphical correlation and dating of the East Greenland Devonian deposits remain to be resolved by further fieldwork. Several assemblages ranging from Givetian to Famennian in age can be distinguished, that correspond to older superceded subdivisional nomenclature. A possible Frasnian fauna has been recognised for the first time, adding details to an otherwise poorly dated part of the succession. Typical Devonian taxa such as Holoptychius Agassiz, 1839 and Groenlandaspis Heintz, 1932 have apparently been recorded in an otherwise unique position above the Devonian-Carboniferous boundary in the upper part of the succession. New specimens of rare elements of the fauna including an unknown arthrodire placoderm, a putative chondrichthyan spine and a patch of possibly regurgitated acanthodian spines, are illustrated for the first time.
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| 36. |
- Boisvert, Catherine Anne, 1978-, et al.
(författare)
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Comparative pelvic development of the axolotl (Ambystoma mexicanum) and the Australian lungfish (Neoceratodus forsteri) : conservation and innovation across the fish-tetrapod transition
- 2013
-
Ingår i: EvoDevo. - : Springer Science and Business Media LLC. - 2041-9139. ; 4, s. 3-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The fish-tetrapod transition was one of the major events in vertebrate evolution and was enabled by many morphological changes. Although the transformation of paired fish fins into tetrapod limbs has been a major topic of study in recent years, both from paleontological and comparative developmental perspectives, the interest has focused almost exclusively on the distal part of the appendage and in particular the origin of digits. Relatively little attention has been paid to the transformation of the pelvic girdle from a small unipartite structure to a large tripartite weight-bearing structure, allowing tetrapods to rely mostly on their hindlimbs for locomotion. In order to understand how the ischium and the ilium evolved and how the acetabulum was reoriented during this transition, growth series of the Australian lungfish Neoceratodus forsteri and the Mexican axolotl Ambystoma mexicanum were cleared and stained for cartilage and bone and immunostained for skeletal muscles. In order to understand the myological developmental data, hypotheses about the homologies of pelvic muscles in adults of Latimeria, Neoceratodus and Necturus were formulated based on descriptions from the literature of the coelacanth (Latimeria), the Australian Lungfish (Neoceratodus) and a salamander (Necturus). Results: In the axolotl and the lungfish, the chondrification of the pelvic girdle starts at the acetabula and progresses anteriorly in the lungfish and anteriorly and posteriorly in the salamander. The ilium develops by extending dorsally to meet and connect to the sacral rib in the axolotl. Homologous muscles develop in the same order with the hypaxial musculature developing first, followed by the deep, then the superficial pelvic musculature. Conclusions: Development of the pelvic endoskeleton and musculature is very similar in Neoceratodus and Ambystoma. If the acetabulum is seen as being a fixed landmark, the evolution of the ischium only required pubic pre-chondrogenic cells to migrate posteriorly. It is hypothesized that the iliac process or ridge present in most tetrapodomorph fish is the precursor to the tetrapod ilium and that its evolution mimicked its development in modern salamanders.
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| 37. |
- Boisvert, Catherine Anne, 1978-
(författare)
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The Origin of Tetrapod Limbs and Girdles: Fossil and Developmental Evidence
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Around 375 million years ago, the first tetrapods appeared, marking one of the most important events in vertebrate evolutionary history. The fin to limb transition saw the appearance of fingers and a weight bearing pelvic girdle. While very little research has been done on the evolution of the tetrapod pelvic girdle, a fair amount has been done on the origins of fingers but some aspects remained controversial. A combination of palaeontology, developmental biology and comparative morphology was therefore used in this thesis to better understand the fin to limb transition. The pectoral fin of Panderichthys, a sarcopterygian fish closely related to tetrapods was CT-scanned and modeled in three dimensions and its pelvic girdle and fin were examined with traditional techniques. This information from the fossil record was integrated with comparisons of the development of the Australian lungfish, Neoceratodus forsteri, our closest living fish relative and the axolotl (Ambystoma mexicanum), a salamander representing well the condition of early tetrapods. Development of bone and cartilage was studied through clearing and staining and development of skeletal muscles through immunostaining. In situ hybridizations were performed on the lungfish to study the expression of Hoxd13, associated with the formation of digits in tetrapods. This work shows that the late expression phase of Hoxd13 is present in Neoceratodus and is associated with the formation of radials. Redescription of the pectoral fin of Panderichthys reveals that distal radials are present, which, in addition to other information, lead us to conclude that digits are not novelties in tetrapods but rather have evolved from the distal radials present in the fins of all sarcopterygian fish. The earliest tetrapods lack a full set of wrist + carpals/ankle + tarsal bones. Here, we propose that this region of the limbs evolved after fingers and toes through an expansion of the region between the proximal limb bones and the digits. As for the pelvic girdle, it is very primitive in Panderichthys but comparison of its development in Neoceratodus and Ambystoma suggest that the ischium evolved through the posterior expansion of the pubis and the ilium, through an elongation of the iliac process already present in sarcopterygian fishes. The results of this thesis help to better understand the fin to limb transition and show that it is more gradual than previously believed.
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| 38. |
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| 39. |
- Botella, Hector, et al.
(författare)
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Jaws and teeth of the earliest bony fishes
- 2007
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 448:7153, s. 583-586
-
Tidskriftsartikel (refereegranskat)abstract
- Extant jawed vertebrates, or gnathostomes, fall into two major monophyletic groups, namely chondrichthyans (cartilaginous fishes) and osteichthyans (bony fishes and tetrapods). Fossil representatives of the osteichthyan crown group are known from the latest Silurian period, 418 million years (Myr) ago, to the present. By contrast, stem chondrichthyans and stem osteichthyans are still largely unknown. Two extinct Palaeozoic groups, the acanthodians and placoderms, may fall into these stem groups or the common stem group of gnathostomes, but their relationships and monophyletic status are both debated. Here we report unambiguous evidence for osteichthyan characters in jaw bones referred to the late Silurian (423–416-Myr-old) fishes Andreolepis hedei and Lophosteus superbus, long known from isolated bone fragments, scales and teeth, and whose affinities to, or within, osteichthyans have been debated1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. The bones are a characteristic osteichthyan maxillary and dentary, but the organization of the tooth-like denticles they bear differs from the large, conical teeth of crown-group osteichthyans, indicating that they can be assigned to the stem group. Andreolepis and Lophosteus are thus not only the oldest but also the most phylogenetically basal securely identified osteichthyans known so far.
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| 40. |
- Clack, Jennifer A., et al.
(författare)
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Sarcopterygians : From Lobe-Finned Fishes to the Tetrapod Stem Group
- 2016
-
Ingår i: Evolution of the Vertebrate Ear. - Cham : Springer Publishing Company. - 9783319466590 - 9783319466613 ; , s. 51-70
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The sarcopterygians or lobe-finned fishes is the group that gave rise to tetrapods, and they were the dominant bony fishes of the Devonian period. Their otic regions were constructed similarly to those of both the actinopterygians and chondrichthyans, their structure being the common inheritance of all jawed vertebrates. One distinguishing feature of the primitive sarcopterygian braincase was that the division between the anterior ethmosphenoid and posterior otoccipital section sof the braincase was marked by a flexible hinge joint, which is seen today in the modern coelacanth, Latimeria. The hyomandibular was long and projected ventrally with an opercular process that contacted the opercular bone and with the distal end associated indirectly with the jaw joint. It was a key component of the buccal pumping mechanism for breathing and feeding. The braincases of dipnoans (lungfishes) were the most highly modified of sarcopterygian braincases with consolidated fore and aft portions and reduction or loss of the hyomandibula. The utricle was enlarged in several fossil dipnoans, although the reason for this is not clear. The braincases of tetrapodomorph sarcopterygians differed little from the primitive condition in the group. The main modifications were to the more crownward and tetrapod-like forms from the Late Devonian. In these fishes, the hyomandibula was reduced in length, its contact with the opercular bone lost and, ultimately, the opercular bone itself disappeared. The spiracular notch and associated cleft increased in width and volume respectively, possibly resulting in increased air-breathing capacity and reduced use of the gill system.
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| 41. |
- Clement, Alice, et al.
(författare)
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The First Virtual Cranial Endocast of a Lungfish (Sarcopterygii: Dipnoi)
- 2014
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:11
-
Tidskriftsartikel (refereegranskat)abstract
- Lungfish, or dipnoans, have a history spanning over 400 million years and are the closest living sister taxon to the tetrapods. Most Devonian lungfish had heavily ossified endoskeletons, whereas most Mesozoic and Cenozoic lungfish had largely cartilaginous endoskeletons and are usually known only from isolated tooth plates or disarticulated bone fragments. There is thus a substantial temporal and evolutionary gap in our understanding of lungfish endoskeletal morphology, between the diverse and highly variable Devonian forms on the one hand and the three extant genera on the other. Here we present a virtual cranial endocast of Rhinodipterus kimberleyensis, from the Late Devonian Gogo Formation of Australia, one of the most derived fossil dipnoans with a well-ossified braincase. This endocast, generated from a Computed Microtomography (µCT) scan of the skull, is the first virtual endocast of any lungfish published, and only the third fossil dipnoan endocast to be illustrated in its entirety. Key features include long olfactory canals, a telencephalic cavity with a moderate degree of ventral expansion, large suparaotic cavities, and moderately enlarged utricular recesses. It has numerous similarities to the endocasts of Chirodipterus wildungensis and Griphognathus whitei, and to a lesser degree to 'Chirodipterus' australis and Dipnorhynchus sussmilchi. Among extant lungfish, it consistently resembles Neoceratodus more closely than Lepidosiren and Protopterus. Several trends in the evolution of the brains and labyrinth regions in dipnoans, such as the expansions of the utricular recess and telencephalic regions over time, are identified and discussed.
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| 42. |
- Clément, Gaël, et al.
(författare)
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A new tristichopterid (Sarcopterygii, Tetrapodomorpha) from the Upper Famennian Evieux Formation (Upper Devonian) of Belgium
- 2009
-
Ingår i: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 52, s. 823-836
-
Tidskriftsartikel (refereegranskat)abstract
- Additional material of a large specimen of tristichopterid fish from the Upper Famennian Evieux Formation of Belgium is described. This large fish was previously assigned to Tristichopteridae gen. et sp. indet. due to the lack of diagnostic anatomical data. New available material consists of the internal surface of the parietal shield, vomers and anterior part of the parasphenoid, subopercular and submandibulo-branchiostegal bones, and an internal view of the anterior part of the mandible. A possible autapomorphy of the new form from Belgium, Langlieria socqueti gen. nov. et sp. nov., is the absence of marginal teeth on the vomer except on its most lateral part. Apart from these features, it only differs from the genus Mandageria from Australia in the absence of marginal teeth between the dentary fang and the mandibular symphysis, in the presence of a raised marginal crest lateral to the anterior coronoid fang, and in the presence of numerous small marginal teeth on the premaxilla. It differs from the cosmopolitan genus Eusthenodon in a number of respects: the supratemporal, tabular, and postparietal bones are superficially fused, as are the intertemporal and parietal bones, the dermal ornament is proportionally very fine, and the denticulated field of the parasphenoid stands proud rather than being recessed into the body of the bone.
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| 43. |
- Dods, Robert, 1989, et al.
(författare)
-
Ultrafast structural changes within a photosynthetic reaction centre.
- 2021
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 589:7841, s. 310-314
-
Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic reaction centres harvest the energy content of sunlight by transporting electrons across an energy-transducing biological membrane. Here we use time-resolved serial femtosecond crystallography1 using an X-ray free-electron laser2 to observe light-induced structural changes in the photosynthetic reaction centre of Blastochloris viridis on a timescale of picoseconds. Structural perturbations first occur at the special pair of chlorophyll molecules of the photosynthetic reaction centre that are photo-oxidized by light. Electron transfer to the menaquinone acceptor on the opposite side of the membrane induces a movement of this cofactor together with lower amplitude protein rearrangements. These observations reveal how proteins use conformational dynamics to stabilize the charge-separation steps of electron-transfer reactions.
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| 44. |
- Dupret, Vincent, et al.
(författare)
-
A primitive placoderm sheds light on the origin of the jawed vertebrate face
- 2014
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 507:7493, s. 500-503
-
Tidskriftsartikel (refereegranskat)abstract
- Extant vertebrates form two clades, the jawless Cyclostomata (lampreys and hagfishes) and the jawed Gnathostomata (all other vertebrates), with contrasting facial architectures(1,2). These arise during development from just a few key differences in the growth patterns of the cranial primordia: notably, the nasal sacs and hypophysis originate from a single placode in cyclostomes but from separate placodes in gnathostomes, and infraoptic ectomesenchyme migrates forward either side of the single placode in cyclostomes but between the placodes in gnathostomes(3-8). Fossil stem gnathostomes preserve cranial anatomies rich in landmarks that provide proxies for developmental processes and allow the transition from jawless to jawed vertebrates to be broken down into evolutionary steps(7,9-12). Here we use propagation phase contrast synchrotron microtomography to image the cranial anatomy of the primitive placoderm (jawed stem gnathostome) Romundina(13), and show that itcombines jawed vertebrate architecture with cranial and cerebral proportions resembling those of cyclostomes and the galeaspid (jawless stem gnathostome) Shuyu(11). This combination seems to be primitive for jawed vertebrates, and suggests a decoupling between ectomesenchymal growth trajectory, ectomesenchymal proliferation, and cerebral shape change during the origin of gnathostomes.
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| 45. |
- Dupret, Vincent, 1977-, et al.
(författare)
-
Bone vascularization and growth in placoderms (Vertebrata) : The example of the premedian plate of Romundina stellina Ørvig, 1975
- 2010
-
Ingår i: Comptes rendus. Palevol. - : Elsevier BV. - 1631-0683 .- 1777-571X. ; 9:6-7, s. 369-375
-
Tidskriftsartikel (refereegranskat)abstract
- The Placodermi (armored jawed fishes), which appeared during the Lower Silurian and disappeared without leading any descendants at the end of the Famennian (Latest Devonian), have the highest diversity of known Devonian vertebrate groups. As phylogenetically basal gnathostomes (jawed vertebrates), they are potentially informative about primitive jawed vertebrate anatomy and origins. Until recently, the study of their internal or histological structures has required destructive methods such as sectioning or serial grinding. Recent advances in tomography and imaging technologies, especially through the increasing use of synchrotron phase contrast imaging for the study of fossils, allow us to reveal the inner structures of the fossil nondestructively and with unprecedented three-dimensional level of detail. Here, we present for the first time the prerostral anatomy of the small acanthothoracid Romundina stellina, one of the earliest and most basal placoderms. Phase contrast imaging allows us to reconstruct the vascularization and nerve canals of the premedian plate and adjacent parts of the skeleton three-dimensionally in great detail, providing important clues to the growth modes and biology of the animal.
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| 46. |
- Dupret, Vincent, et al.
(författare)
-
Non-tetrapod sarcopterygians from the Valentia Slate Formation (Givetian, Devonian) of the Iveragh Peninsula, south-western Ireland: systematic reappraisal and palaeobiogeographic implications
- 2023
-
Ingår i: Spanish Journal of Palaeontology. - 2255-0550 .- 2660-9568. ; 38:1, s. 37-45
-
Tidskriftsartikel (refereegranskat)abstract
- The Middle Devonian (Givetian) Valentia Slate Formation in the Iveragh Peninsula, southwest Ireland, is more renowned for the second oldest record of tetrapod trackways in the world than for its heavily metamorphosed bone remains. The present study focuses on new discoveries of non-tetrapod sarcopterygian fish fossils from the Valentia Slate Formation. Micro-CT scanning technology allows a re-interpretation of a previously published acanthodian fin spine as a fanged coronoid of a probable Rhizodontida and the identification of a Dipnoi tooth plate and bone. In addition, a scale of Holoptychius is described. The presence of rhizodontids suggests Gondwanan ties, and a first northward dispersal wave of these vertebrates into Euramerica as early as middle Givetian. This hypothesis is supported by the common occurrence of the placoderm Bothriolepis in the Valentia Slate Formation.
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| 47. |
- Dupret, Vincent, et al.
(författare)
-
The internal cranial anatomy of Romundina stellina Orvig, 1975 (Vertebrata, Placodermi, Acanthothoraci) and the origin of jawed vertebrates : Anatomical atlas of a primitive gnathostome
- 2017
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:2
-
Tidskriftsartikel (refereegranskat)abstract
- Placoderms are considered as the first jawed vertebrates and constitute a paraphyletic group in the stem-gnathostome grade. The acanthothoracid placoderms are among the phylogenetically most basal and morphologically primitive gnathostomes, but their neurocranial anatomy is poorly understood. Here we present a near-complete three-dimensional skull of Romundina stellina, a small Early Devonian acanthothoracid from the Canadian Arctic Archipelago, scanned with propagation phase contrast microtomography at a 7.46 mu m isotropic voxel size at the European Synchrotron Radiation Facility, Grenoble, France. This is the first model of an early gnathostome skull produced using this technique, and as such represents a major advance in objectivity compared to past descriptions of placoderm neurocrania on the basis of grinding series. Despite some loss of material along an oblique crack, most of the internal structures are remarkably preserved, and most of the missing structures can be reconstructed by symmetry. This virtual approach offers the possibility to connect with certainty all the external foramina to the blood and nerve canals and the central structures, and thus identify accurate homologies without destroying the specimen. The high level of detail enables description of the main arterial, venous and nerve canals of the skull, and other perichondrally ossified endocranial structures such as the palatoquadrate articulations, the endocranial cavity and the inner ear cavities. The braincase morphology appears less extreme than that of Brindabellaspis, and is in some respects more reminiscent of a basal arthrodire such as Kujdanowiaspis.
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| 48. |
- Fadel, Alexandre, et al.
(författare)
-
Palaeoenvironmental signatures revealed from rare earth element (REE) compositions of vertebrate microremains of the Vesiku Bone Bed (Homerian, Wenlock), Saaremaa Island, Estonia
- 2015
-
Ingår i: Estonian journal of earth sciences. - : Estonian Academy Publishers. - 1736-4728 .- 1736-7557. ; 64:1, s. 36-41
-
Tidskriftsartikel (refereegranskat)abstract
- Rare earth elements (REEs) have been analysed from fossil vertebrate microremains (thelodont scales) from the Vesiku Bone Bed, Saaremaa, Estonia, using in situ microsampling by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Well-preserved scales of three species of the genus Thelodus (T. carinatus, T. laevis and Thelodus sp.) show very uniform REE patterns with slightly lower overall REE concentrations in enameloid than in dentine, with enrichment in middle REEs, depletion in heavy REEs and pronounced negative europium anomaly, but no cerium anomaly. The results of this study suggest a similar diagenetic history and possibly contemporaneous habitats for all three Thelodus species, as well as possible suboxic to anoxic conditions of the bottom and pore waters during the formation of the Vesiku Bone Bed.
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| 49. |
- Fiz-Palacios, Omar, et al.
(författare)
-
Did terrestrial diversification of amoebas (Amoebozoa) occur in synchrony with land plants?
- 2013
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:9, s. e74374-
-
Tidskriftsartikel (refereegranskat)abstract
- Evolution of lineage diversification through time is an active area of research where much progress has been made in the last decade. Contrary to the situation in animals and plants little is known about how diversification rates have evolved in most major groups of protist. This is mainly due to uncertainty about phylogenetic relationships, scarcity of the protist fossil record and the unknown diversity within these lineages. We have analyzed the evolutionary history of the supergroup Amoebozoa over the last 1000 million years using molecular dating and species number estimates. After an origin in the marine environment we have dated the colonization of terrestrial habitats by three distinct lineages of Amoebozoa: Dictyostelia, Myxogastria and Arcellinida. The common ancestor of the two sister taxa, Dictyostelia and Myxogastria, appears to have existed before the colonization of land by plants. In contrast Arcellinida seems to have diversify in synchrony with land plant radiation, and more specifically with that of mosses. Detection of acceleration of diversification rates in Myxogastria and Arcellinida points to a co-evolution within the terrestrial habitats, where land plants and the amoebozoans may have interacted during the evolution of these new ecosystems.
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| 50. |
- Ghouse, Jonas, et al.
(författare)
-
Association of Variants Near the Bradykinin Receptor B2 Gene With Angioedema in Patients Taking ACE Inhibitors
- 2021
-
Ingår i: Journal of the American College of Cardiology. - : Elsevier. - 0735-1097 .- 1558-3597. ; 78:7, s. 696-709
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND Angioedema is a rare but potentially life-threatening adverse reaction associated with angiotensinconverting enzyme (ACE) inhibitors. Identification of potential genetic factors related to this adverse event may help identify at-risk patients. OBJECTIVES The aim of this study was to identify genetic factors associated with ACE inhibitor-associated angioedema. METHODS A genomewide association study involving patients of European descent, all taking ACE inhibitors, was conducted in a discovery cohort (Copenhagen Hospital Biobank), and associations were confirmed in a replication cohort (Swedegene). Cases were defined as subjects with angioedema events and filled prescriptions for ACE inhibitors #180 days before the events. Control subjects were defined as those with continuous treatment with ACE inhibitors without any history of angioedema. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed for angioedema risk using logistic mixed model regression analysis. Summary statistics from the discovery and replication cohorts were analyzed using a fixed-effects meta-analysis model. RESULTS The discovery cohort consisted of 462 cases and 53,391 ACE inhibitor-treated control subjects. The replication cohort consisted of 142 cases and 1,345 ACE inhibitor-treated control subjects. In the discovery cohort, 1 locus, residing at chromosome 14q32.2, was identified that associated with angioedema at the genomewide significance level of P <5 x 10-8. The lead variant at this locus, rs34485356, is an intergenic variant located 60 kb upstream of BDKRB2 (OR: 1.62; 95% CI: 1.38 to 1.90; P = 4.3 x 10-9). This variant was validated in our replication cohort with a similar direction and effect size (OR: 1.60; 95% CI: 1.13 to 2.25; P = 7.2 x 10-3). We found that carriers of the risk allele had significantly lower systolic (-0.46 mm Hg per T allele; 95% CI:-0.83 to-0.10; P = 0.013) and diastolic (-0.26 mm Hg per T allele; 95% CI:-0.46 to-0.05; P = 0.013) blood pressure. CONCLUSIONS In this genomewide association study involving individuals treated with ACE inhibitors, we found that common variants located in close proximity to the bradykinin receptor B2 gene were associated with increased risk for ACE inhibitor-related angioedema.
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