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Visar resultat 1 - 5 av 54 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Holocene climate and atmospheric circulation changes in northern Fennoscandia : Interpretations from lacustrine oxygen isotope records

   Författare :Christina E. Jonsson; Gunhild Rosqvist; Jan Seibert; Philip Barker; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; oxygen isotope; diatom silica; lake sediment; atmospheric circulation; North Atlantic Oscillation; northern Fennoscandia; The Holocene; Little Ice Age; Physical geography; Naturgeografi; Physical Geography; naturgeografi;

   Sammanfattning : This thesis investigates how variations in the oxygen isotopic composition of lake waters in northern Fennoscandia are recorded in lake sediment archives, especially diatoms, and how these variations can be used to infer past changes in climate and atmospheric circulation. Results from analyses of the oxygen isotopic composition of lake water samples (δ18Olakew) collected between 2001 and 2006 show that δ18O of northern Fennoscandian lakes is mainly controlled by the isotopic composition of the precipitation (δ18Op). LÄS MER

3. 2. Nitrogen Cycling at Cold Climate Mine Sites in Northen Sweden

   Författare :Lino Nilsson; Anders Widerlund; Anders Lundqvist; Luleå tekniska universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Nitrogen; Mining; Cycling; nutrients; Isotopes; Nitrogen-model; modelling; numerical-modelling; Isotope-tracing; Tracing; Isotope; geochemistry; Applied Geology; Tillämpad geologi;

   Sammanfattning : High nitrogen discharge from mining sites has been an environmental issue that has been closely studied in the recent years. The environmental effects of high nitrogen discharge are mainly eutrophication, but can also lead to changed species composition and algae blooms. LÄS MER

4. 3. The origin of streamwater traced by oxygen-18

   Författare :Allan Rodhe; Erik Eriksson; Lars Bengtsson; Sten Bergström; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; streamflow generation; oxygen-18; isotope hydrograph separation; fractionation; Hydrology; Hydrologi;

   Sammanfattning : .... LÄS MER

5. 4. Modified oxygen and hydrogen transport in Zr-based oxides

   Författare :Clara Anghel; Gunnar Hultquist; Magnus Limbäck; Truls Norby; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Zirconia; Zirconium; Zircaloy; hydrogen and oxygen diffusion; SPP; oxygen dissociating elements; oxidation; dissociation; hydration; CO adsorption; molecular transport; porosity.; Materials science; Teknisk materialvetenskap;

   Sammanfattning : Most metals and alloys in the presence of oxygen and moisture will instantaneously react and form a thin (2-5 nm) surface oxide layer. For further reaction to occur, oxygen ions and/or metal cations often diffuse through the already formed oxide layer. LÄS MER

7. 5. Catalysts for Car Exhaust: Oxygen Storage in Platinum/Ceria and Mass Transfer in Monoliths

   Författare :Anna Holmgren; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; car exhaust; catalysis; flow distribution; mass transfer; oxygen storage capacity OSC ; ceria; computational fluid-dynamics simulations; monolith catalyst; platinum; oxygen transport;

   Sammanfattning : In this work, the oxygen storage/release in Pt/ceria catalysts has been investigated both experimentally and theoretically. Moreover, the flow distribution and mass transfer in monolith catalysts for car-exhaust purification have been studied. LÄS MER