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Fakultet for naturvitenskap og teknologi

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• Doktorgradsavhandlinger (NT-fak) [52]
• Mastergradsoppgaver for lærerutdanning i naturfag og matematikk [1]
• Mastergradsoppgaver for lærerutdanning i realfag [11]
• Mastergradsoppgaver i energi og miljø i nord [5]

Recent additions

• Optical Forces, Waveguides and Micro Raman Spectroscopy

  Løvhaugen, Pål (Doctoral thesis; Doktorgradsavhandling, 21-Dec-2012)

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  Abstract:

  Optical waveguides are used to confine propagating light. In a dielectric waveguide, a small part of the propagating light travels along and just outside the waveguide surface. This evanescent field can interact with objects on the waveguide surface. Two effects of this light-matter interaction are presented, optical forces and Raman scattering. Optical forces are caused by changes in the momentum of radiation. The forces are exerted on objects interacting with a propagating field. The magnitude of the force is dependent on the difference in permittivity and permeability between the object and the surrounding medium. The forces can be used to trap and control micro- and nanoparticles. In Raman scattering, the scattered field exchanges energy with the scatterer. The amount of energy that is lost or gained depends on the molecular structure of the scatterer. By collecting the spectra of the scattered light, the molecules in the scatterer can be analyzed and characterized. Two numerical studies have been performed to simulate optical forces on a range of micrometer-sized objects trapped and propelled on a waveguide. A numerical model of a hollow glass sphere provides new insights on how the optical force depends on the glass thickness. A numerical model of a red blood cell studies the force dependence on cell shape and refractive index. A model of a real-sized cell is made. Two experimental studies have used Raman spectroscopy to characterize and analyze objects subject to optical forces. One study looks at the viability of using Raman scattering to characterize objects trapped on waveguides. It was found that characterization with Raman spectroscopy is viable with the use of an external, focused light source, while excitation using the evanescent field is difficult. A second study investigates a new technique for proliferation measurements of non-adherent cells. A combined optical trapping–Raman spectroscopy setup is used to show that a Raman probe can be used to measure proliferation of actively replicating cells, even in a sample were the cell growth is slow or negative. The presented studies were performed to investigate the potential of combining characterization with optical trapping on waveguides. This could be of use in an optical lab-on-a-chip for cells.

  URI:

  http://hdl.handle.net/10037/5151

  File(s) in this item: 1

  thesis.pdf   (8.191Mb)
• Geophysical characterizations of fluid flow and gas-hydrate systems of the NW-Svalbard and SW-Barents Sea margins

  Rajan, Anupama (Doctoral thesis; Doktorgradsavhandling, 06-Feb-2013)

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  Abstract:	The thesis consists of four parts and its four main objectives are: (1) to establish a potential link between serpentinization beneath a young sedimented-ocean ridge and carbon release and gas hydrate formation directly above it, (2) to understand the coexistence of free gas and gas-hydrate and to image the geophysical evidence for a geologically controlled gas hydrate, fluid migration pathway and seabed expulsion system, (3) to image the active fluid flow migration path-networks from deep hydrocarbon sources and to assess the distribution of shallow gas accumulation, and (4) to determine in detail the seismic velocity structure of the regions close to the landward limit of hydrate stability zone. The methodology implemented to realize this aims was achieved by integrating 3D seismic imaging, 1D velocity modeling to 2D seismic imaging and bathymetric and oceanographic data mapping. This PhD thesis presents results from four articles that glean into the fluid flow and gas-hydrate systems of the NW-Svalbard and SW-Barents Sea margins. The important results found during this research are: (1) new evidence for carbon release from the deep-seated source rock through the sediments above diapirism and methane capture in the inferred areas of serpentinization at the Knipovich Ridge, (2) new geophysical evidence for gas migration and geologically controlled gas hydrate system offshore NW-Svalbard, where several existing glacigenic debris flow units, which are spatially confined and influence gas migration pathways and hence, the location of gas leakage zones at the seafloor and (3) first findings of the formation of “tilted” bottom-simulating reflector in the SW-Barents Sea. They have formed due to variations in fluid flux along regions of deep-seated fault complexes causing a change in heat flow. The data also provides new evidence for the connection of deep-hydrocarbon and shallow gas hydrate, where existing fault complexes apparently act as pathways for the upward migration of fluids.
  Description:	Papers 2, and 4 of this thesis are not available in Munin: 2. Rajan, A., J. Mienert, and S. Bünz: 'Acoustic evidence for a gas migration and release system in Arctic glaciated continental margins offshore NW-Svalbard', Marine and Petroleum Geology (2012), vol.32(1):36-49. Available at http://dx.doi.org/10.1016/j.marpetgeo.2011.12.008 3. Anupama Rajan, Stefan Bünz, Jürgen Mienert and. Andrew J. Smith: 'Tilted bottomsimulating reflectors (TBSRs) provide evidence for active fluid flow from deep hydrocarbon sources in the SW-Barents Sea' (manuscript) 4. Anupama Rajan, Tim A. Minshull and Jürgen Mienert: 'Heterogeneous distribution of gashydrate and free gas in glaciated sediments of the NW-Svalbard continental margin inferred from changes in compressional wave velocity' (manuscript).
  URI:	http://hdl.handle.net/10037/5149

  File(s) in this item: 2

  paper_1.pdf   (10.67Mb)

  thesis.pdf   (4.996Mb)
• Understanding and predicting one- and two-photon absorption properties of molecular complexes

  Steindal, Arnfinn Hykkerud (Doctoral thesis; Doktorgradsavhandling, 22-Jan-2013)

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  Abstract:	This thesis presents the development of theoretical models for the calculations of one- and two-photon absorption, and computational studies on solvated systems and biomolecules. The photon-absorbing chromophore is described by density functional theory, while the effects of the surroundings are taken into account by means of polarizable embedding models. The theory and implementation of a three-layered fully polarizable method is presented in this thesis. In this method, the short-range electrostatic potential due to the solvent is treated by a polarizable molecular mechanics force field, while the long-range effects are described by a dielectric continuum. This QM/MM/PCM implementation was tested on three organic molecules solvated in water and shown to converge faster with respect to system size compared to calculations using quantum mechanics/molecular mechanics (QM/MM) only. Further, the parallelization of the QM/MM module in the Dalton program is decribed, making it possible to do calculations on large molecular systems with the use of modern supercomputers. This implementation was used to calculate the one- and two-photon absorption properties in fluorescent proteins, demonstrating the importance of describing the protein surrounding the chromophore by a polarizable embedding.
  Description:	The papers of this thesis are not available in Munin: 1. A. H. Steindal, K. Ruud, L. Frediani, K. Aidas and J. Kongsted: 'Excitation energies in solution: the fully polarizable QM/MM/PCM method', Journal of Physical Chemistry B (2011), vol.115(12):3027–3037. Available at http://dx.doi.org/10.1021/jp1101913 2. A. H. Steindal, J. M. H. Olsen, L. Frediani, J. Kongsted and K. Ruud: 'Parallelization of the polarizable embedding scheme for higher-order response functions', Molecular Physics (2012), Vol. 110, no.19-20. Available at http://dx.doi.org/10.1080/00268976.2012.721016 3. A. H. Steindal, J. M. H. Olsen, K. Ruud, L. Frediani and J. Kongsted: 'A combined quantum mechanics and molecular mechanics study of the one- and two-photon absorption in the green fluorescent protein', Physical Chemistry Chemical Physics (2012), vol.14:5440-5451. Available at http://dx.doi.org/10.1039/C2CP23537D 4. M. T. P. Beerepoot, A. H. Steindal, J. M. H. Olsen, K. Ruud, L. Frediani, B. O. Brandsdal and J. Kongsted: 'A polarizable embedding DFT study of one-photon absorption in fluorescent proteins' (manuscript) 5. N. H. List, J. M. H. Olsen, H. J. Aa. Jensen, A. H. Steindal and J. Kongsted: 'Molecular-level insight into the spectral tuning mechanism of the DsRed chromophore', Journal of Physical Chemistry Letters (2012), vol.3(23):3513–3521. Available at http://dx.doi.org/10.1021/jz3014858
  URI:	http://hdl.handle.net/10037/5148

  File(s) in this item: 1

  thesis.pdf   (1.944Mb)
• Ice Shelf - Ocean Interaction in the Eastern Weddell Sea, Antarctica

  Hattermann, Tore (Doctoral thesis; Doktorgradsavhandling, 10-Dec-2012)

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  Abstract:	This thesis investigates the interaction of the Antarctic ice shelves along the coast of Dronning Maud Land with the ocean circulation in the Eastern Weddell Sea. A set of direct oceanic observations below the Fimbul Ice Shelf, which were acquired during three Antarctic field seasons in the austral summers 2009/10, 2010/11 and 2011/12, is a central element of the presented work. This new oceanographic dataset is complemented by a high-resolution state-of-the-art ice shelf - ocean circulation model. The results provide an estimate of the amount of basal melting at the Fimbul Ice Shelf, and revise the physical processes that determine the ocean heat fluxes over the East Antarctic continental slope. A major finding is that deep-ocean heat fluxes towards the ice are much more constrained than predicted by previous ocean models, causing substantially lower rates of basal melting than earlier suggested. The predicted basal melting is consistent with mass balance estimates from satellite data and implicates that the Fimbul Ice Shelf is currently not subject to rapid basal mass loss. Furthermore, the complex interplay of the processes within the coastal, frontal system, and their respective role in transporting heat for melting towards the ice is examined. The results emphasize the importance of oceanic eddies within the coastal circulation for controlling the inflow of Warm Deep Water into the ice shelf cavities. A realistic representation of the effect of the mesoscale eddy overturning is thus a crucial requirement in order to simulate basal melting along the Weddell Sea coast in the present and future climate. The results also imply that fresh, and solar-heated Antarctic Surface Water plays a central role for the ice shelf cavity exchange. Being produced by sea ice melting at the ocean surface, this water mass directly enters the cavity and increases the melting of shallow ice. Due to its buoyancy, the presence of Antarctic Surface Water also alters the coastal dynamics and regulates the inflow of warm water at depth, thus showing that a more detailed understanding of the role of this water mass for basal melting around Antarctica will need further attention. Finally, the results suggest a direct relationship between the simulated basal melting and only a few deterministic parameters of the coastal circulation, which is used to derive a simple parameterization of for basal melting at the Fimbul Ice Shelf.
  Description:	Papers 3 and 4 are not available in Munin: 3. T. Hattermann, L. H. Smedsrud, O. A. Nøst, J. M. Lilly, and B. Galton-Fenzi: 'Modeling basal melting below the Fimbul Ice Shelf, Antarctica' (manuscript) 4. Q. Zhou, T. Hattermann and O. A. Nøst: 'Wind-driven spreading of fresh Antarctica Surface Water below ice shelves in the Eastern Weddell Sea' (manuscript)
  URI:	http://hdl.handle.net/10037/5147

  File(s) in this item: 3

  paper_1.pdf   (3.982Mb)

  paper_2.pdf   (1.604Mb)

  thesis.pdf   (22.16Mb)
• Processes and dynamics during deglaciation of a polar continental shelf. Examples from the marine-based Barents Sea Ice Sheet

  Bjarnadottir, Lilja Run (Doctoral thesis; Doktorgradsavhandling, 20-Dec-2012)

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  Abstract:	The main objective of this PhD thesis was to reconstruct the pattern and main processes of the last deglaciation of the Barents Sea Ice Sheet. The thesis consists of an introductory part and five papers. The conclusions presented in the papers were based on data acquired with a suite of marine geophysical and geological methods, including multibeam-swath bathymetry data, chirp data, airgun and sparker seismic data and sediment (gravity) cores. Bathymetric data were used for identification and mapping of main geomorphic features on the seafloor. The distribution, geometry, reflection signature and seismic/acoustic stratigraphy of seabed sediments, were assessed based on chirp and seismic data. Sediment core analyses provided information about the depositional environment and age constraints for deglaciation. The primary focus was on two main study areas. The first area is Kveithola, a small submarine trough on the western margin of the continental shelf (NW of Bjørnøya). Results from Kveithola are presented in papers 1-2. In the first paper, the sedimentary environment in the trough from the time it was deglaciated before ~14.2 cal ka ago until the last sign of glacimarine sedimentation in the trough ~10.3 cal ka ago, is reconstructed. The second paper summarises both the complex retreat history of the Kveithola Ice Stream and the following glacimarine sedimentation in a conceptual model. The second study area was the central Barents Sea, which is addressed in papers 3-5. The third paper includes a map showing the distribution of large tunnel valleys on the seafloor, along with descriptions and discussions of their attributes, genesis and relevance for glacial history. The fourth paper focuses on the seafloor of upper Bjørnøyrenna, where a landform assemblage related to ice stream stagnation is presented and a new model of ice stream retreat in meltwater-dominated areas is introduced. In the final paper a new reconstruction of the deglaciation of the central Barents Sea is presented. The reconstruction includes main ice flow patterns, prolonged ice margin positions and glacial dynamics during the retreat of the ice sheet, based on both new and old data.
  Description:	The papers of this thesis are not available in Munin: 1. Rüther, D.C., Bjarnadóttir, L.R., Junttila, J., Husum, K., Rasmussen, T.L., Lucchi, R.G. and Andreassen, K.: 'Pattern and timing of the north-western Barents Sea Ice Sheet deglaciation and indications of episodic Holocene deposition', Boreas (2012), vol. 41(3):494-512. Available at http://dx.doi.org/10.1111/j.1502-3885.2011.00244.x 2. Bjarnadóttir, L.R., Rüther, D.C., Winsborrow, M.C.M. and Andreassen, K.: 'Grounding line dynamics of the Kveithola ice stream, W Barents Sea, as identified from seabed geomorphology and shallow seismic stratigraphy', Boreas (2013), vol. 42(1):84–107. Available at http://dx.doi.org/10.1111/j.1502-3885.2012.00273.x 3. Bjarnadóttir, L.R., Winsborrow, M.C.M. and Andreassen, K.: 'Tunnel valleys in the Barents Sea' (manuscript) 4. Andreassen, K., Winsborrow, M.C.M., Bjarnadóttir, L.R. and Rüther, D.C.: 'Landform assemblage from the collapse of the Bjørnøyrenna palaeo-ice stream, northern Barents Sea' (manuscript) 5. Bjarnadóttir, L.R., Winsborrow, M.C. and Andreassen, K.: 'Deglaciation of the central Barents Sea' (manuscript)
  URI:	http://hdl.handle.net/10037/5146

  File(s) in this item: 1

  thesis.pdf   (3.445Mb)

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