Sökning: "ice core"

Visar resultat 16 - 20 av 57 avhandlingar innehållade orden ice core.

1. 16. Simulation of Core-Level Spectra of H-bonded Systems

   Författare :Iurii Zhovtobriukh; Lars G.M. Pettersson; Anders Nilsson; Marcus Lundberg; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; water; x-ray absorption; non-resonant x-ray emission; damped linear response theory; time-dependent density functional theory; semi-classical approximation to Kramers-Heisenberg formula; Reverse Monte-Carlo; kemisk fysik; Chemical Physics;

   Sammanfattning : The thesis consists of three related projects where attempts have been made to simulate X-Ray Absorption (XAS) spectra of water and hexagonal ice, static non-resonant X-ray Emission (XES) spectrum of water and to apply the semi-classical approximation to Kramers-Heisenberg formula (SCKH) formalism to calculate the non-resonant XES spectrum of water and methanol. The first project is devoted to an investigation of the performance of damped response theory in combination with the DFT electronic structure method (CPP-DFT) in XAS spectrum simulations of liquid water. LÄS MER

3. 17. Astrochemical Surface Science: Water Desorption from Nanostructured Graphite

   Författare :Anna Clemens; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; intercalation; temperature programmed desorption; diffuse reflection; geometrical resonances; water ice; ultra high vacuum;

   Sammanfattning : To date, around 180 different molecules have been identified in the interstellar medium (ISM). Some of them form molecular ices on cold interstellar dust grain surfaces. An interstellar dust grain particle is in the order of nanometres in size and is usually composed of a carbonaceous or silicatious grain core. LÄS MER

4. 18. Disentangling production and climate signals from high-resolution Beryllium records: implications for solar and geomagnetic reconstructions

   Författare :Minjie Zheng; MERGE: ModElling the Regional and Global Earth system; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Solar Activity; 10Be; 7Be; ice cores; tropopause; climate; cosmogenic radionuclides; geomagnetic reconstructions; multi-linear regression;

   Sammanfattning : The sun is the most important energy source for the Earth’s climate system, however, influences of solar variations on climate are not fully understood. Studying past solar activity can improve our understanding of what role the sun plays in Earth’s climate. LÄS MER

5. 19. Influence of solar activity and environment on 10Be in recent natural archives

   Författare :Ann-Marie Berggren; Ala Aldahan; Göran Possnert; Anne Hormes; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; cosmogenic isotopes; beryllium; ice cores; varved lake sediments; accelerator mass spectrometry; co-precipitation; Quaternary geology; Kvartärgeologi;

   Sammanfattning : Understanding the link between the Sun and climate is vital in the current incidence of global climate change, and 10Be in natural archives constitutes an excellent tracer for this purpose. As cosmic rays enter the atmosphere, cosmogenic isotopes like 10Be and 14C are formed. LÄS MER

7. 20. Detecting changes in climate and atmospheric composition with tracers in Arctic ice caps

   Författare :Margareta Hansson; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : Changes in climate and atmospheric composition over decades to a hundred thousand years have been studied by extracting records of various tracers from two Arctic ice cores. A seven metre long ice core of superimposed ice was recovered from the Storöya ice cap in north-eastern Svalbard. LÄS MER