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Träfflista för sökning "WFRF:(Kockum Ingrid Skelton) "

Sökning: WFRF:(Kockum Ingrid Skelton)

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  • Andrén, Margareta, et al. (författare)
  • Coupling between mineral reactions, chemical changes in groundwater, and earthquakes in Iceland
  • 2016
  • Ingår i: Journal of Geophysical Research - Solid Earth. - 2169-9313 .- 2169-9356. ; 121:4, s. 2315-2337
  • Tidskriftsartikel (refereegranskat)abstract
    • Chemical analysis of groundwater samples collected from a borehole at Hafralækur, northernIceland, from October 2008 to June 2015 revealed (1) a long-term decrease in concentration of Si and Naand (2) an abrupt increase in concentration of Na before each of two consecutive M > 5 earthquakes whichoccurred in 2012 and 2013, both 76 km from Hafralækur. Based on a geochemical (major elements and stableisotopes), petrological, and mineralogical study of drill cuttings taken from an adjacent borehole, we areable to show that (1) the long-term decrease in concentration of Si and Na was caused by constant volumereplacement of labradorite by analcime coupled with precipitation of zeolites in vesicles and along fracturesand (2) the abrupt increase of Na concentration before the first earthquake records a switchover tononstoichiometric dissolution of analcime with preferential release of Na into groundwater. We attributedecay of the Na peaks, which followed and coincided with each earthquake to uptake of Na along fracturedor porous boundaries between labradorite and analcime crystals. Possible causes of these Na peaks are anincrease of reactive surface area caused by fracturing or a shift from chemical equilibrium caused by mixingbetween groundwater components. Both could have been triggered by preseismic dilation, which was alsoinferred in a previous study by Skelton et al. (2014). The mechanism behind preseismic dilation so far from thefocus of an earthquake remains unknown.
  • Skelton, Alasdair, et al. (författare)
  • Changes in groundwater chemistry before two consecutive earthquakes in Iceland
  • 2014
  • Ingår i: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 7:10, s. 752-756
  • Tidskriftsartikel (refereegranskat)abstract
    • Groundwater chemistry has been observed to change before earthquakes and is proposed as a precursor signal. Such changes include variations in radon count rates(1,2), concentrations of dissolved elements(3-5) and stable isotope ratios(4,5). Changes in seismicwave velocities(6), water levels in boreholes(7), micro-seismicity(8) and shear wave splitting(9) are also thought to precede earthquakes. Precursor activity has been attributed to expansion of rock volume(7,10,11). However, most studies of precursory phenomena lack sufficient data to rule out other explanations unrelated to earthquakes(12). For example, reproducibility of a precursor signal has seldom been shown and few precursors have been evaluated statistically. Here we analyse the stable isotope ratios and dissolved element concentrations of groundwater taken from a borehole in northern Iceland between 2008 and 2013. We find that the chemistry of the groundwater changed four to six months before two greater than magnitude 5 earthquakes that occurred in October 2012 and April 2013. Statistical analyses indicate that the changes in groundwater chemistry were associated with the earthquakes. We suggest that the changes were caused by crustal dilation associated with stress build-up before each earthquake, which caused different groundwater components to mix. Although the changes we detect are specific for the site in Iceland, we infer that similar processes may be active elsewhere, and that groundwater chemistry is a promising target for future studies on the predictability of earthquakes.
  • Olafsson, Sigurgeir, et al. (författare)
  • Fourteen sequence variants that associate with multiple sclerosis discovered by meta-analysis informed by genetic correlations
  • Ingår i: npj Genomic Medicine. - : Nature Publishing Group. - 2056-7944. ; 2:1
  • Tidskriftsartikel (refereegranskat)abstract
    • A meta-analysis of publicly available summary statistics on multiple sclerosis combined with three Nordic multiple sclerosis cohorts (21,079 cases, 371,198 controls) revealed seven sequence variants associating with multiple sclerosis, not reported previously. Using polygenic risk scores based on public summary statistics of variants outside the major histocompatibility complex region we quantified genetic overlap between common autoimmune diseases in Icelanders and identified disease clusters characterized by autoantibody presence/absence. As multiple sclerosis-polygenic risk scores captures the risk of primary biliary cirrhosis and vice versa (P = 1.6 × 10-7, 4.3 × 10-9) we used primary biliary cirrhosis as a proxy-phenotype for multiple sclerosis, the idea being that variants conferring risk of primary biliary cirrhosis have a prior probability of conferring risk of multiple sclerosis. We tested 255 variants forming the primary biliary cirrhosis-polygenic risk score and found seven multiple sclerosis-associating variants not correlated with any previously established multiple sclerosis variants. Most of the variants discovered are close to or within immune-related genes. One is a low-frequency missense variant in TYK2, another is a missense variant in MTHFR that reduces the function of the encoded enzyme affecting methionine metabolism, reported to be dysregulated in multiple sclerosis brain.
  • Tengvall, Katarina, 1980- (författare)
  • Genetic Studies in Dogs Implicate Novel Genes Involved in Atopic Dermatitis and IgA Deficiency
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • This thesis presents genetic studies of atopic dermatitis (AD) and IgA deficiency in dogs.AD is a chronic inflammatory and pruritic skin disorder caused by allergic reactions against environmental allergens. Both genetic and environmental factors are involved in the development of Canine AD (CAD) and human AD. In Paper I, we performed genome-wide association studies (GWAS) and identified a locus on chromosome 27 significantly associated with CAD in German shepherd dogs (GSDs). The locus contains several genes and fine-mapping indicated strongest association close to the candidate gene PKP2. In Paper II, we performed additional fine-mapping and identified four highly associated SNPs located in regions with transcriptional regulatory potential in epithelial and immune cells. The risk alleles were associated with increased transcriptional activity and the effect on expression was cell-type dependent. These data indicate that multiple cell-type specific enhancers regulate the expression of PKP2, and/or the neighboring genes YARS2, DNM1L and FGD4, and predispose GSDs to CAD.IgA deficiency is the most common primary immune deficiency disorder in both humans and dogs, characterized by a higher risk of recurrent mucosal tract infections, allergic and other immune-mediated diseases. In Paper III, we performed the widest screening (to date) of serum IgA levels in dog breeds (Ndogs=1267, Nbreeds=22) and defined eight breeds as predisposed to low IgA levels. In Paper IV, we performed GWAS in four of the breeds defined as prone to low IgA levels. We used a novel percentile groups-approach to establish breed-specific cut-offs to perform analyses in a close to continuous manner. In total, 35 genomic loci were suggestively associated (p<0.0005) to IgA levels, and three genomic regions (including the genes KIRREL3 and SERPINA9) were genome-wide significantly associated with IgA levels in GSDs. A ~20kb long haplotype on chromosome 28, significantly associated to IgA levels in Shar-Pei dogs, was positioned within the first intron of the gene SLIT1 overlapping with a possible dog domestication sweep.This thesis suggests novel candidate genes involved in two immune-mediated disorders in the dog. Hopefully, these results will become an important resource for the genetic research of the corresponding human diseases.
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