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Sökning: WFRF:(Isaacs Sarah) > (2010-2014)

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  • Coxall, Helen K., et al. (författare)
  • Export of nutrient rich Northern Component Water preceded early Oligocene Antarctic glaciation
  • 2018
  • Ingår i: Nature Geoscience. - 1752-0894. ; 11:3, s. 190-196
  • Tidskriftsartikel (refereegranskat)abstract
    • The onset of the North Atlantic Deep Water formation is thought to have coincided with Antarctic ice-sheet growth about 34 million years ago (Ma). However, this timing is debated, in part due to questions over the geochemical signature of the ancient Northern Component Water (NCW) formed in the deep North Atlantic. Here we present detailed geochemical records from North Atlantic sediment cores located close to sites of deep-water formation. We find that prior to 36 Ma, the northwestern Atlantic was stratified, with nutrient-rich, low-salinity bottom waters. This restricted basin transitioned into a conduit for NCW that began flowing southwards approximately one million years before the initial Antarctic glaciation. The probable trigger was tectonic adjustments in subarctic seas that enabled an increased exchange across the Greenland-Scotland Ridge. The increasing surface salinity and density strengthened the production of NCW. The late Eocene deep-water mass differed in its carbon isotopic signature from modern values as a result of the leakage of fossil carbon from the Arctic Ocean. Export of this nutrient-laden water provided a transient pulse of CO2 to the Earth system, which perhaps caused short-term warming, whereas the long-term effect of enhanced NCW formation was a greater northward heat transport that cooled Antarctica.
  • Christel, Stephan, et al. (författare)
  • RNA transcript sequencing reveals inorganic sulfur compound oxidation pathways in the acidophile Acidithiobacillus ferrivorans
  • 2016
  • Ingår i: FEMS Microbiology Letters. - 0378-1097. ; 363:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Acidithiobacillus ferrivorans is an acidophile implicated in low-temperature biomining for the recovery of metals from sulfide minerals. Acidithiobacillus ferrivorans obtains its energy from the oxidation of inorganic sulfur compounds, and genes encoding several alternative pathways have been identified. Next-generation sequencing of At. ferrivorans RNA transcripts identified the genes coding for metabolic and electron transport proteins for energy conservation from tetrathionate as electron donor. RNA transcripts suggested that tetrathionate was hydrolyzed by the tetH1 gene product to form thiosulfate, elemental sulfur and sulfate. Despite two of the genes being truncated, RNA transcripts for the SoxXYZAB complex had higher levels than for thiosulfate quinone oxidoreductase (doxDA genes). However, a lack of heme-binding sites in soxX suggested that DoxDA was responsible for thiosulfate metabolism. Higher RNA transcript counts also suggested that elemental sulfur was metabolized by heterodisulfide reductase (hdr genes) rather than sulfur oxygenase reductase (sor). The sulfite produced as a product of heterodisulfide reductase was suggested to be oxidized by a pathway involving the sat gene product or abiotically react with elemental sulfur to form thiosulfate. Finally, several electron transport complexes were involved in energy conservation. This study has elucidated the previously unknown At. ferrivorans tetrathionate metabolic pathway that is important in biomining.
  • Jidesjö, Anders (författare)
  • Students’ interest in science and technology as a function of science in society : Mediated experience and the public understanding of science
  • ????
  • Annan publikation (övrigt vetenskapligt)abstract
    • Young people’s interest in science and technology has long been an object for research. Cultural aspects and informal learning have been identified as important factors to be considered. In this study comparative content analysis is used to compare what secondary students want to learn about in science and technology with the topics covered in international popular science television. Important similarities are identified. The results are discussed from the perspective of media theory in terms of modernity affecting young people’s experience as a result of the popularization of science by communication media. The role of public understanding of science is identified and the importance of difference between science in society and science in school is elaborated on. The work has implications for future research, for interpretation and categorization of the results of such research, and for understanding student’s encounters with school science.
  • Sciaraffia, Elena, et al. (författare)
  • The use of impedance cardiography for optimizing the interventricular stimulation interval in cardiac resynchronization therapy-a comparison with left ventricular contractility
  • 2009
  • Ingår i: Journal of interventional cardiac electrophysiology (Print). - 1383-875X .- 1572-8595. ; 25:3, s. 223-228
  • Tidskriftsartikel (refereegranskat)abstract
    • The present study aimed to assess whether impedance cardiography (IC) can correctly identify the optimal interventricular (VV) pacing interval in cardiac resynchronization therapy (CRT). Twenty four patients received a biventricular pacemaker and underwent IC for cardiac output (CO) measurements to identify the optimal VV interval. Invasive measurements of left ventricular (LV) dP/dt(max) were used as a reference. During optimization the VV interval was changed with 20 ms steps from +80 (LV pre-excitation) to-80 ms (RV pre-excitation). The optimal VV interval was defined as the one that resulted in the highest LV dP/dt(max) value and the highest CO obtained by IC, respectively. During simultaneous biventricular pacing both LV dP/dt(max) and CO increased (mean 16.6% and 16.2%, respectively) as compared to baseline. Biventricular pacing with optimized VV intervals resulted in a further absolute increase of LV dP/dt (max) and CO (5.6% and 41.3%, respectively). The average decrease in LV dP/dt(max) was 79.6 +/- 51.6 mmHg/s when the optimal VV interval was programmed according to the IC measurements. Cross spectral analysis showed no correlation between the optimal VV intervals identified by the two methods (p > 0.05) and identical optimal VV intervals were identified in only six of the 24 patients. When broader VV time intervals were compared the correlation between the two methods was statistically significant (p = 0,0166). In conclusion, the use of IC for VV interval optimization is questionable since these optimized time intervals do not seem to correlate well with those obtained by measuring LV dP/dt.
  • Stålstedt, Jeanette, 1982- (författare)
  • Phylogeny, taxonomy and species delimitation of water mites and velvet mites
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • This study is part of the Swedish Taxonomy Initiative (STI) - one of the most ambitious all taxa biodiversity inventories in the world. One of the pillars in STI is to support taxonomic research on the most neglected taxonomic groups with the aim to lift the level of knowledge of biodiversity in the country. There is still a lot to be discovered, especially in the microscopic world, and this includes mites. Many aspects of mite biology and diversity are poorly known, such as species richness, abundance, distribution, lifestyle and behavior of species. Mites inhabits all sorts of aquatic, terrestrial, arboreal and parasitic habitats, nevertheless even in well-studied systems mites are often overlooked. Despite being among the smallest of arthropods, they are of medical and economical importance and may be very abundant in the ecosystems they inhabit. This thesis focuses on Parasitengona (Acariformes: Prostigmata), one of the most diverse taxa among the arachnids. It includes the aquatic Hydrachnidia (water mites) and the terrestrial Trombidia (e.g. velvet mites, chiggers). A unifying characteristic of Parasitengona is their complex life cycle of active and inactive stages, parasitic larvae and predatory deutonymphs and adults. They typically parasitize and prey on arthropods, except the chiggers which have vertebrates as hosts. The aim of this thesis is to shed light on the phylogeny and taxonomy of Parasitengona with emphasis on the Swedish fauna. To achieve this, mites were collected from different localities throughout the country between the years 2007-2016. Water mites were sampled with a hand net. Larvae of terrestrial Parasitengona were collected with sweeping nets and sorted out from malaise trap samples from the Swedish Malaise Trap Project. To collect the adults Berlese-Tullgren extractor and pitfall traps were used as well as hand collecting and sifting with litter reducer. The material collected abroad was kindly provided through collaboration.  Methods used in the papers included morphometrics, multivariate analyses, experimental rearing, DNA extraction and sequencing, Bayesian phylogenetic analyses and molecular species delimitation. In paper I and II, we combine molecular species delimitation models and morphological data to resolve taxonomical issues. This integrative taxonomic approach of combining data resulted in Piona dispersa Sokolow, 1926 as a valid species and redescriptions, new synonyms and neotypes provided for Erythraeus phalangoides (De Geer, 1778),  E. cinereus (Dugès, 1834) and E. regalis (C.L. Koch, 1837). Based on the new inventories we produce an updated and annotated checklist of 105 terrestrial Parasitengona species for Fennoscandia in paper III, and use metadata to increase the knowledge on distribution, habitat preferences, life stages and abundance. Out of these, 20 species are new findings for the region and five are potential new species for science. In paper IV, we provide a molecular phylogeny of Parasitengona based on the genes 18S, 28S and COI for 80 taxa with a sampling focus on the terrestrial lineages. Based on the results we offer a revised higher-level classification of the group. In particular the analyses supported Tanaupodoidea Thor, 1935 as a separate superfamily, but Trombiculoidea Ewing, 1929 was not monophyletic and was synonymized, along with Chyzerioidea Womersley, 1954, with Trombidioidea Leach, 1815.
  • Tchaplyguine, M., et al. (författare)
  • What one can learn about clusters using the unique tools of x-ray photoelectron spectroscopy
  • 2012
  • Ingår i: Journal of Physics, Conference Series. - 1742-6588 .- 1742-6596. ; 388:15, s. 152025
  • Tidskriftsartikel (refereegranskat)abstract
    • This presentation is intended to illustrate various types of collisional processes relevant for free clusters probed by x-ray photoelectron spectroscopy using our own examples ranging from free-electron-metal clusters, through half-metal and semiconductor clusters to dielectrics, the latter from van-der-Waals to ionic clusters.
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