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Sökning: WFRF:(Bleeker A.)

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  • Ernst, R. E., et al. (författare)
  • Long-lived connection between southern Siberia and northern Laurentia in the Proterozoic
  • 2016
  • Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 9:6, s. 464-469
  • Tidskriftsartikel (refereegranskat)abstract
    • Precambrian supercontinents Nuna-Columbia (1.7 to 1.3 billion years ago) and Rodinia (1.1 to 0.7 billion years ago) have been proposed. However, the arrangements of crustal blocks within these supercontinents are poorly known. Huge, dominantly basaltic magmatic outpourings and intrusions, covering up to millions of square kilometres, termed Large Igneous Provinces, typically accompany (super) continent breakup, or attempted breakup and offer an important tool for reconstructing supercontinents. Here we focus on the Large Igneous Province record for Siberia and Laurentia, whose relative position in Nuna-Columbia and Rodinia reconstructions is highly controversial. We present precise geochronology - nine U-Pb and six Ar-Ar ages - on dolerite dykes and sills, along with existing dates from the literature, that constrain the timing of emplacement of Large Igneous Province magmatism in southern Siberia and northern Laurentia between 1,900 and 720 million years ago. We identify four robust age matches between the continents 1,870, 1,750, 1,350 and 720 million years ago, as well as several additional approximate age correlations that indicate southern Siberia and northern Laurentia were probably near neighbours for this 1.2-billion-year interval. Our reconstructions provide a framework for evaluating the shared geological, tectonic and metallogenic histories of these continental blocks.
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  • Sutton, M. A., et al. (författare)
  • Towards a climate-dependent paradigm of ammonia emission and deposition
  • 2013
  • Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2970 .- 0962-8436. ; 368:1621
  • Tidskriftsartikel (refereegranskat)abstract
    • Existing descriptions of bi-directional ammonia (NH3) land-atmosphere exchange incorporate temperature and moisture controls, and are beginning to be used in regional chemical transport models. However, such models have typically applied simpler emission factors to upscale the main NH3 emission terms. While this approach has successfully simulated the main spatial patterns on local to global scales, it fails to address the environment-and climate-dependence of emissions. To handle these issues, we outline the basis for a new modelling paradigm where both NH3 emissions and deposition are calculated online according to diurnal, seasonal and spatial differences in meteorology. We show how measurements reveal a strong, but complex pattern of climatic dependence, which is increasingly being characterized using ground-based NH3 monitoring and satellite observations, while advances in process-based modelling are illustrated for agricultural and natural sources, including a global application for seabird colonies. A future architecture for NH3 emission-deposition modelling is proposed that integrates the spatio-temporal interactions, and provides the necessary foundation to assess the consequences of climate change. Based on available measurements, a first empirical estimate suggests that 5 degrees C warming would increase emissions by 42 per cent (28-67%). Together with increased anthropogenic activity, global NH3 emissions may increase from 65 (45-85) Tg N in 2008 to reach 132 (89-179) Tg by 2100.
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  • Caton, Summer A., et al. (författare)
  • Evolution of the sources of TTG and associated rocks during the Archean from in-situ 87Sr/86Sr isotope analysis of apatite by LA-MC-ICPMS
  • 2022
  • Ingår i: Lithos. - : Elsevier BV. - 0024-4937 .- 1872-6143. ; 428-429
  • Tidskriftsartikel (refereegranskat)abstract
    • Radiogenic isotopes provide an important means towards elucidating Archean crustal evolution. The global Hf and Nd isotope record of Archean crustal fragments has been instrumental to unveiling the history of ancient crustal growth and differentiation. The Rb-Sr system could provide valuable complementary constraints in this regard, as this system is particularly sensitive to magmatic fractionation processes, and the chemical and isotopic evolution of magma sources. Application of this system has so far been complicated, however, by its susceptibility to isotope re-equilibration or alteration of the Rb/Sr parent-daughter ratio. In-situ Sr isotope analysis of primary igneous minerals with very low Rb/Sr, such as apatite, provides a new means to determine the initial 87Sr/86Sr (87Sr/86Sri) values for igneous rocks directly. In this study, we apply in-situ Sr isotope analysis of apatite by LA-MC-ICPMS to tonalite-trondhjemite-granodiorite (TTG) rocks and end-member sanukitoids from Archean cratons worldwide. The 87Sr/86Sri values of sanukitoids are relatively radiogenic, supporting the model in which such rocks are formed by flux melting of a mantle strongly enriched by metasomatism, possibly by slab-derived fluids. The 87Sr/86Sri values for TTGs formed between 3.72 and 3.45 Ga are generally radiogenic, indicating aged amphibolite sources. The 87Sr/86Sri values of younger TTGs are systematically lower and were derived from mafic sources that had an average age of ≤0.2 Gyr. This evolution matches with observations from Hf isotopes for TTGs of similar age and indicates a systematic change in the nature or efficiency of TTG crust formation during the Paleoarchean. In-situ Sr isotope analysis of apatite provides a useful method to uncover the Sr record of the early continental crust, and enables constraints on local source evolution and the general two-step evolutionary process of Archean crust formation.
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  • Flechard, C. R., et al. (författare)
  • Dry deposition of reactive nitrogen to European ecosystems: a comparison of inferential models across the NitroEurope network
  • 2011
  • Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:6, s. 2703-2728
  • Tidskriftsartikel (refereegranskat)abstract
    • Inferential models have long been used to determine pollutant dry deposition to ecosystems from measurements of air concentrations and as part of national and regional atmospheric chemistry and transport models, and yet models still suffer very large uncertainties. An inferential network of 55 sites throughout Europe for atmospheric reactive nitrogen (N-r) was established in 2007, providing ambient concentrations of gaseous NH3, NO2, HNO3 and HONO and aerosol NH4+ and NO3- as part of the NitroEurope Integrated Project. Network results providing modelled inorganic Nr dry deposition to the 55 monitoring sites are presented, using four existing dry deposition routines, revealing inter-model differences and providing ensemble average deposition estimates. Dry deposition is generally largest over forests in regions with large ambient NH3 concentrations, exceeding 30-40 kg N ha(-1) yr(-1) over parts of the Netherlands and Belgium, while some remote forests in Scandinavia receive less than 2 kg N ha(-1) yr(-1). Turbulent Nr deposition to short vegetation ecosystems is generally smaller than to forests due to reduced turbulent exchange, but also because NH3 inputs to fertilised, agricultural systems are limited by the presence of a substantial NH3 source in the vegetation, leading to periods of emission as well as deposition. Differences between models reach a factor 2-3 and are often greater than differences between monitoring sites. For soluble Nr gases such as NH3 and HNO3, the non-stomatal pathways are responsible for most of the annual uptake over many surfaces, especially the non-agricultural land uses, but parameterisations of the sink strength vary considerably among models. For aerosol NH4+ and NO3-, discrepancies between theoretical models and field flux measurements lead to much uncertainty in dry deposition rates for fine particles (0.1-0.5 mu m). The validation of inferential models at the ecosystem scale is best achieved by comparison with direct long-term micrometeorological Nr flux measurements, but too few such datasets are available, especially for HNO3 and aerosol NH4+ and NO3-.
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  • Rutten, Martijn G. S., et al. (författare)
  • Normalization of hepatic ChREBP activity does not protect against liver disease progression in a mouse model for Glycogen Storage Disease type Ia
  • 2023
  • Ingår i: Cancer & Metabolism. - : Springer Nature. - 2049-3002. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundGlycogen storage disease type 1a (GSD Ia) is an inborn error of metabolism caused by a defect in glucose-6-phosphatase (G6PC1) activity, which induces severe hepatomegaly and increases the risk for liver cancer. Hepatic GSD Ia is characterized by constitutive activation of Carbohydrate Response Element Binding Protein (ChREBP), a glucose-sensitive transcription factor. Previously, we showed that ChREBP activation limits non-alcoholic fatty liver disease (NAFLD) in hepatic GSD Ia. As ChREBP has been proposed as a pro-oncogenic molecular switch that supports tumour progression, we hypothesized that ChREBP normalization protects against liver disease progression in hepatic GSD Ia.MethodsHepatocyte-specific G6pc knockout (L-G6pc−/−) mice were treated with AAV-shChREBP to normalize hepatic ChREBP activity.ResultsHepatic ChREBP normalization in GSD Ia mice induced dysplastic liver growth, massively increased hepatocyte size, and was associated with increased hepatic inflammation. Furthermore, nuclear levels of the oncoprotein Yes Associated Protein (YAP) were increased and its transcriptional targets were induced in ChREBP-normalized GSD Ia mice. Hepatic ChREBP normalization furthermore induced DNA damage and mitotic activity in GSD Ia mice, while gene signatures of chromosomal instability, the cytosolic DNA-sensing cGAS-STING pathway, senescence, and hepatocyte dedifferentiation emerged.ConclusionsIn conclusion, our findings indicate that ChREBP activity limits hepatomegaly while decelerating liver disease progression and protecting against chromosomal instability in hepatic GSD Ia. These results disqualify ChREBP as a therapeutic target for treatment of liver disease in GSD Ia. In addition, they underline the importance of establishing the context-specific roles of hepatic ChREBP to define its therapeutic potential to prevent or treat advanced liver disease.
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  • Bleeker, Gitta, et al. (författare)
  • MIBG scans in patients with stage 4 neuroblastoma reveal two metastatic patterns, one is associated with MYCN amplification and in MYCN-amplified tumours correlates with a better prognosis
  • 2015
  • Ingår i: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer Science and Business Media LLC. - 1619-7070 .- 1619-7089. ; 42:2, s. 222-230
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose The aim of this study was to find clinically relevant MIBG-avid metastatic patterns in patients with newly diagnosed stage 4 neuroblastoma. Methods Diagnostic I-123-MIBG scans from 249 patients (123 from a European and 126 from the COG cohort) were assessed for metastatic spread in 14 body segments and the form of the lesions: "focal" (clear margins distinguishable from adjacent background) or "diffuse" (indistinct margins, dispersed throughout the body segment). The total numbers of diffuse and focal lesions were recorded. Patients were then categorized as having lesions exclusively focal, lesions more focal than diffuse, lesions more diffuse than focal, or lesions exclusively diffuse. Results Diffuse lesions affected a median of seven body segments and focal lesions a median of two body segments (P<0.001, both cohorts). Patients with a focal pattern had a median of 2 affected body segments and those with a diffuse pattern a median of 11 affected body segments (P<0.001, both cohorts). Thus, two MIBG-avid metastatic patterns emerged: "limited-focal" and "extensive-diffuse". The median numbers of affected body segments in MYCN-amplified (MNA) tumours were 5 (European cohort) and 4 (COG cohort) compared to 9 and 11, respectively, in single-copy MYCN (MYCNsc) tumours (P<0.001). Patients with exclusively focal metastases were more likely to have a MNA tumour (60 % and 70 %, respectively) than patients with the other types of metastases (23 % and 28 %, respectively; P<0.001). In a multivariate Cox regression analysis, focal metastases were associated with a better event-free and overall survival than the other types of metastases in patients with MNA tumours in the COG cohort (P<0.01). Conclusion Two metastatic patterns were found: a " limited and focal" pattern found mainly in patients with MNA neuroblastoma that correlated with prognosis, and an " extensive and diffuse" pattern found mainly in patients with MYCNsc neuroblastoma.
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  • Bleeker, M. C. G., et al. (författare)
  • Penile cancer: epidemiology, pathogenesis and prevention
  • 2009
  • Ingår i: World Journal of Urology. - : Springer Science and Business Media LLC. - 1433-8726 .- 0724-4983. ; 27:2, s. 141-150
  • Tidskriftsartikel (refereegranskat)abstract
    • Penile cancer is a disease with a high morbidity and mortality. Its prevalence is relatively rare, but the highest in some developing countries. Insight into its precursor lesions, pathogenesis and risk factors offers options to prevent this potentially mutilating disease. This review presents an overview of the different histologically and clinically identified precursor lesions of penile cancer and discusses the molecular pathogenesis, including the role of HPV in penile cancer development. A systematic review of the literature evaluating penile carcinogenesis, risk factors and molecular mechanisms involved. Careful monitoring of men with lichen sclerosis, genital Bowen's disease, erythroplasia of Queyrat and bowenoid papulosis seems useful, thereby offering early recognition of penile cancer and, subsequently, conservative therapeutic options. Special attention is given to flat penile lesions, which contain high numbers of HPV. Their role in HPV transmission to sexual partners is highlighted, but their potential to transform as a precursor lesion into penile cancer has been unsatisfactorily explored. Further research should not only focus on HPV mediated pathogenic pathways but also on the non-HPV related molecular and genetic factors that play a role in penile cancer development. Options for prevention of penile cancer include (neonatal) circumcision, limitation of penile HPV infections (either by prophylactic vaccination or condom use), prevention of phimosis, treatment of chronic inflammatory conditions, limiting PUVA treatment, smoking cessation and hygienic measures.
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  • Hertel, O., et al. (författare)
  • Governing processes for reactive nitrogen compounds in the European atmosphere
  • 2012
  • Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 9:12, s. 4921-4954
  • Forskningsöversikt (refereegranskat)abstract
    • Reactive nitrogen (Nr) compounds have different fates in the atmosphere due to differences in the governing processes of physical transport, deposition and chemical transformation. N r compounds addressed here include reduced nitrogen (NH x : ammonia (NH 3 ) and its reaction product ammonium (NH 4 + )), oxidized nitrogen (NO y : nitrogen monoxide (NO) + nitrogen dioxide (NO 2 ) and their reaction products) as well as organic nitrogen compounds (organic N). Pollution abatement strategies need to take into account the differences in the governing processes of these compounds when assessing their impact on ecosystem services, biodiversity, human health and climate. NO x (NO + NO 2 ) emitted from traffic affects human health in urban areas where the presence of buildings increases the residence time in streets. In urban areas this leads to enhanced exposure of the population to NO x concentrations. NO x emissions generally have little impact on nearby ecosystems because of the small dry deposition rates of NO x . These compounds need to be converted into nitric acid (HNO 3 ) before removal through deposition is efficient. HNO 3 sticks quickly to any surface and is thereby either dry deposited or incorporated into aerosols as nitrate (NO 3 + ). In contrast to NOx compounds, NH 3 has potentially high impacts on ecosystems near the main agricultural sources of NH 3 because of its large ground-level concentrations along with large dry deposition rates. Aerosol phase NH 4 + and NO 3 + contribute significantly to background PM 2.5 and PM 10 (mass of aerosols with an aerodynamic diameter of less than 2.5 and 10 μm, respectively) with an impact on radiation balance as well as potentially on human health. Little is known quantitatively and qualitatively about organic N in the atmosphere, other than that it contributes a significant fraction of wet-deposited N, and is present in both gaseous and particulate forms. Further studies are needed to characterise the sources, air chemistry and removal rates of organic N emissions.
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14.
  • Kastek, N., et al. (författare)
  • U-Pb Geochronology and Geochemistry of the Povungnituk Group of the Cape Smith Belt : Part of a Craton-Scale Circa 2.0 Ga Minto-Povungnituk Large Igneous Province, Northern Superior Craton
  • 2018
  • Ingår i: Lithos. - : Elsevier BV. - 0024-4937. ; 320-321, s. 315-331
  • Tidskriftsartikel (refereegranskat)abstract
    • Magmatism of the Povungnituk Group of the Cape Smith Belt, northern Superior craton, was formed in three stages: (i)early alkaline magmatism and associated carbonatites (undated), (ii) a main flood basalt sequence (Beauparlant Formation) (constrained between 2040 and 1991 Ma), and (iii) a late stage alkaline pulse (Cecilia Formation) (ca. 1959 Ma). We suggest that the main stage of magmatic activity (middle pulse) was of short duration. A new U–Pb baddeleyite age of 1998 ± 6 Ma is obtained from a dolerite sill intruding the uppermost section of the Beauparlant Formation. This age has regional significance because it matches the previously obtained 1998 ± 2 Ma age for the Watts Group (Purtuniq) ophiolite of the northern Cape Smith Belt and the 1998 ± 2 Ma U-Pb age of the Minto dykes intruding the craton to the south. These coeval units, along with additional units correlated on paleomagnetic grounds (Eskimo Formation), are interpreted to define a large igneous province (LIP), extending over an area of >400,000 km2, which we herein define as the Minto-Povungnituk LIP. Geochemical comparison between the Watts Group ophiolite, Minto dykes and the mafic Povungnituk Group shows significant differences allowing these data to be divided into two groups and domains within the LIP. A northern domain, comprising the Povungnituk and Watts groups, shows mixing between a depleted mantle source and a more enriched mantle plume-sourced melt. A southern domain comprising the Minto dykes and the paleomagnetically linked Eskimo Formation shows signs of an even more enriched source, while these magmas also show the effect of crustal contamination. Two distinct source mechanisms can be responsible for the observed geochemical differences between the two domains. First, a difference in lithospheric sources, where melting of different portions of Superior craton lithosphere caused the different melt signatures in the interior of the craton. In this case magmatism in the two domains is only related by having the same heat source (e.g.,a mantle plume) interpreted to be located on the northwestern side of the northern Superior craton. Second, two distinct deep mantle sources that remained separated within the ascending plume. This is analogous to some current hotspots interpreted to sample both large low shear velocity provinces (LLSVP) and adjacent ambient deep mantle. This latter interpretation would allow for the use of bilateral chemistry in LIPs as a potential tool for the recognition and mapping of the LLSVP boundaries throughout Earth's history.
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  • Mitchell, Ross N., et al. (författare)
  • PLATE TECTONICS BEFORE 2.0 Ga: EVIDENCE FROM PALEOMAGNETISM OF CRATONS WITHIN SUPERCONTINENT NUNA
  • 2014
  • Ingår i: American Journal of Science. - : American Journal of Science (AJS). - 0002-9599. ; 314:4, s. 878-894
  • Tidskriftsartikel (refereegranskat)abstract
    • Laurentia, the core of Paleo- to Mesoproterozoic supercontinent Nuna, has remained largely intact since assembly 2.0 to 1.8 billion years ago [Ga]. For earlier times, previous paleomagnetic data on poorly dated Paleoproterozoic mafic intrusions yielded ambiguous estimates of the amount of separation between key cratons within Nuna such as the Slave and Superior. Recent developments in paleomagnetism and U-Pb baddeleyite geochronology, including new results reported herein, yield sufficiently precise data to generate partial apparent polar wander paths for both the Slave and Superior craton from 2.2 to 2.0 Ga. Our new apparent polar wander comparison confirms earlier speculations that processes similar to plate tectonics, with relative motion between the Slave and Superior cratons, were operative leading up to the final assembly of supercontinent Nuna.
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  • Robroek, Björn J. M., et al. (författare)
  • Taxonomic and functional turnover are decoupled in European peat bogs
  • 2017
  • Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • In peatland ecosystems, plant communities mediate a globally significant carbon store. The effects of global environmental change on plant assemblages are expected to be a factor in determining how ecosystem functions such as carbon uptake will respond. Using vegetation data from 56 Sphagnum-dominated peat bogs across Europe, we show that in these ecosystems plant species aggregate into two major clusters that are each defined by shared response to environmental conditions. Across environmental gradients, we find significant taxonomic turnover in both clusters. However, functional identity and functional redundancy of the community as a whole remain unchanged. This strongly suggests that in peat bogs, species turnover across environmental gradients is restricted to functionally similar species. Our results demonstrate that plant taxonomic and functional turnover are decoupled, which may allow these peat bogs to maintain ecosystem functioning when subject to future environmental change.
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17.
  • Smit, Mattijs, et al. (författare)
  • Formation of Archean continental crust constrained by boron isotopes
  • 2019
  • Ingår i: Geochemical Perspective Letters. - : European Association of Geochemistry. - 2410-3403. ; , s. 23-26
  • Tidskriftsartikel (refereegranskat)abstract
    • The continental crust grew and matured compositionally during the Palaeo- to Neoarchean through the addition of juvenile tonalite-trondhjemite-granodiorite (TTG) crust. This change has been linked to the start of global plate tectonics, following the general interpretation that TTGs represent ancient analogues of arc magmas. To test this, we analysed B concentrations and isotope compositions in 3.8-2.8 Ga TTGs from different Archean terranes. The 11B/10B values and B concentrations of the TTGs, and their correlation with Zr/Hf, indicatedifferentiation from a common B-poor mafic source that did not undergo addition of B from seawater or seawater-altered rocks. The TTGs thus do not resemble magmatic rocks from active margins, which clearly reflect such B addition to their source. The B- and 11B-poor nature of TTGs indicates that modern style subduction may not have been a dominant process in the formation of juvenile continental crust before 2.8 Ga.
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18.
  • Van Der Weide, R.Y., et al. (författare)
  • Innovation in mechanical weed control in crop rows
  • 2008
  • Ingår i: Weed research (Print). - : Wiley. - 0043-1737 .- 1365-3180. ; 48:3, s. 215-224
  • Tidskriftsartikel (refereegranskat)abstract
    • Weed control within crop rows is one of the main problems in organic farming. For centuries, different weed removal tools have been used to reduce weeds in the crop rows. Stimulated by the demand from organic farmers, research in several European countries over the last decade has focused on mechanisation using harrowing, torsion finger weeding and weeding with compressed air (Pneumat). Intelligent weeders are now being developed which offer more advanced ways to control weeds, including larger ones and to leave the crop plants unharmed. One of the first commercially available intelligent weeders, the Sarl Radis from France, has a simple crop detection system based on light interception, which guides a hoe in and out of the crop row, around the crop plants. The inclusion of innovative technologies, including advanced sensing and robotics, in combination with new cropping systems, might lead to a breakthrough in physical weed control in row crops leading to significant reductions, or even elimination, of the need for hand weeding. © 2008 The Authors.
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