Blar i tittel Doktorgradsavhandlinger (NT-fak)

Viser treff 113-132 av 290

    • Interactive Visualization on High-Resolution Tiled Display Walls with Network Accessible Compute- and Display-Resources 

      Hagen, Tor-Magne Stien (Doctoral thesis; Doktorgradsavhandling, 2011-09-26)
      The vast volume of scientific data produced today requires tools that can enable scientists to explore large amounts of data to extract meaningful information. One such tool is interactive visualization. The amount of data that can be simultaneously visualized on a computer display is proportional to the display’s resolution. While computer systems in general have seen a remarkable increase in ...

    • Interfacial solvation modelling with PCM 

      Mozgawa, Krzysztof (Doctoral thesis; Doktorgradsavhandling, 2016-02-17)
      The effect of surfaces and interfaces on the molecular properties and structure is of a great interest in the applied sciences and technology. In the following thesis, a theoretical framework for the calculations of the free energy and properties, including the effect of interfaces and surfaces, in quantum-mechanical formalism is presented. The model of choice is Polarizable Continuum Method (PCM), ...

    • Interferometric and high time-resolution observations of naturally enhanced ion-acoustic echoes at the EISCAT Svalbard radar: Software radar and incoherent scattering 

      Grydeland, Tom (Doctoral thesis; Doktorgradsavhandling, 2003-06-24)
      We know that the visible Aurora Borealis is structured on many different scales, down to a few tens of metres. By using the EISCAT radars on Svalbard as an interferometer, we have found structures in the radio echoes from the auroral ionosphere on a scale approaching that of the visible aurora, and simultaneously with it, but at far greater ranges. In this thesis we discuss how these radar observations ...

    • Intermittent fluctuations in the boundary of magnetically confined fusion plasmas 

      Ahmed, Sajidah (Doctoral thesis; Doktorgradsavhandling, 2023-10-09)
      Fluctuation-induced transport in the form of hot and dense blob-like filaments is a profound concern for the successful operation of commercially-viable fusion reactors. These turbulent phenomena are inherent in the scrape-off layer (SOL), a region of magnetic field lines intersecting with the material surfaces. These filaments propagate radially outward leading to damaging plasma-wall interaction ...

    • Investigation of Sea Ice Using Multiple Synthetic Aperture Radar Acquisitions 

      Yitayew, Temesgen Gebrie (Doctoral thesis; Doktorgradsavhandling, 2018-02-23)
      The thesis investigates imaging in the vertical direction of different types of ice in the arctic using synthetic aperture radar (SAR) tomography and SAR interferometry. In the first part, the magnitude and the positions of the dominant scattering contributions within snow covered fjord and lake ice layers are effectively identified by using a very high resolution ground-based tomographic SAR system. ...

    • Investigations of summer sea ice with X and C-band multi-polarimetric synthetic aperture radar (SAR) 

      Fors, Ane Schwenke (Doctoral thesis; Doktorgradsavhandling, 2017-03-17)
      In this thesis, we explore the possibilities and limitations of using space-borne multi-polarimetric SAR in summer sea ice investigations. Both X and C-band data are examined. The study utilizes two data sets collected in the Arctic in 2011 (Fram Strait) and 2012 (north of Spitsbergen). Both sets combine satellite SAR scenes with co-located ground and air-borne measurements. Firstly, the study ...

    • Iron dependent gene regulation and siderophore systems in Vibrionaceae 

      Thode, Sunniva Katharina (Doctoral thesis; Doktorgradsavhandling, 2017-03-15)
      Bacteria live in fluctuating environments, which they sense and respond to through gene regulation. Availably of iron is an example of an element fluctuating and that can Bacteria sense.Iron is an essential micronutrient that is scares in several environments, especially in a host. The ferric uptake regulator, Fur, is the major iron level sensing protein and regulator of iron acquisition systems in ...

    • KAIRA - The Kilpisjärvi Atmospheric Imaging Receiver Array 

      McKay, Derek (Doctoral thesis; Doktorgradsavhandling, 2018-08-24)
      The Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) is a phased-array radio detector located in Arctic Finland, where auroral electron precipitation is common. This unique deployment of a modern radio telescope in an unconventional location has resulted in a novel and powerful instrument capable of carrying out a large variety of remote-sensing, geoscience experiments. This work presents a ...

    • Label-free super-resolution optical microscopy 

      Jayakumar, Nikhil (Doctoral thesis; Doktorgradsavhandling, 2024-02-06)
      To see structures well below 200 nm using visible light, super-resolution techniques have been developed. Most of these techniques rely on fluorescence labelling or use of artificial materials to go beyond the Abbe limit. Therefore, achieving super-resolution in the label-free regime is the problem that is being addressed in this thesis. In this work, high-index contrast dielectric waveguides are ...

    • Late glacial and deglacial paleoceanographic and environmental changes at Vestnesa Ridge, Fram Strait: challenges in reading methane-influenced sedimentary records 

      Sztybor, Kamila (Doctoral thesis; Doktorgradsavhandling, 2017-01-18)
      Denne avhandlingen er basert på fire sedimentkjerner fra et område ved Vest Svalbard hvor metan siver opp fra havbunnen. Studien fokuserer på å rekonstruere graden av metanutsiving i fortiden, samt klimavariasjoner i Arktiske strøk med bruk av bentiske foraminiferer. Foraminiferer er encellede organismer som produserer en kalkholdig skall som bevares i sedimentene på havbunnen. Ved å se på geokjemiske ...

    • Late Glacial – Holocene climate variability and sedimentary environments on northern continental shelves Zonal and meridional Atlantic Water advection 

      Sørensen, Steffen Aagaard (Doctoral thesis; Doktorgradsavhandling, 2011-03-22)
      The overall objective for this PhD-study was to further advance the understanding of the oceanographic variability and development in the Nordic Seas during the Late Glacial and the Holocene and towards the present. The focus is specifically on the poleward Atlantic Water advection along the continental margins of Norway, into the SW Barents Sea and along the West Spitsbergen slope. Four high ...

    • Late Pleistocene-Holocene history of Svalbard ice caps and glaciers – integrating marine, terrestrial and lacustrine archives 

      Allaart, Lis (Doctoral thesis; Doktorgradsavhandling, 2021-03-25)
      The Arctic regions are affected by the modern climate change to a greater extent than the global average. This effect is called the Arctic amplification and is reflected in air temperatures rising with double rate and increased precipitation compared to the global average. The climate of Svalbard is strongly related to variations in the atmospheric and oceanic circulation patterns, and the archipelago ...

    • Late Quaternary paleoceanography of the northern continental margin of Svalbard 

      Chauhan, Teena (Doctoral thesis; Doktorgradsavhandling, 2015-08-27)
      This study focuses on the reconstruction of the variability of Atlantic Water inflow to the Arctic Ocean and its influence on the Svalbard-Barents Sea Ice Sheet (SBIS), sea-ice cover, variations in the bottom current strength and the depositional environment in the past. For this reconstruction, the distribution patterns of planktic and benthic foraminiferal assemblages, oxygen and carbon stable ...

    • Late Weichselian ice-sheet dynamics and deglaciation history of the northern Svalbard margin 

      Fransner, Oscar (Doctoral thesis; Doktorgradsavhandling, 2018-05-04)
      This thesis presents new results from marine geological and geophysical studies based on sediment gravity cores, airgun, subbottom acoustic and high-resolution swath bathymetric data from fjords, the continental shelf and slope north of Nordaustlandet, Svalbard. From these records, the glacial landform assemblages as well as the glacial and postglacial sedimentary environments were interpreted. Where ...

    • Leveraging Computer Vision for Applications in Biomedicine and Geoscience 

      Johansen, Thomas Haugland (Doctoral thesis; Doktorgradsavhandling, 2021-06-25)
      Skin cancer is one of the most common types of cancer and is usually classified as either non-melanoma and melanoma skin cancer. Melanoma skin cancer accounts for about half of all skin cancer-related deaths. The 5-year survival rate is 99% when the cancer is detected early but drops to 25% once it becomes metastatic. In other words, the key to preventing death is early detection. Foraminifera ...

    • Leveraging Kernels for Unsupervised Learning 

      Løkse, Sigurd (Doctoral thesis; Doktorgradsavhandling, 2020-12-11)
      <p>Kernel methods have been a central part of the machine learning arsenal for several decades. Within this framework, unsupervised learning has been a particularly challenging area. This is due to the inherent nature of unsupervised learning tasks, where important information about the structure of the data is unknown to the user, and as such it is difficult to design a kernel or system to solve ...

    • Leveraging Supervoxels for Medical Image Volume Segmentation With Limited Supervision 

      Hansen, Stine (Doctoral thesis; Doktorgradsavhandling, 2022-12-16)
      The majority of existing methods for machine learning-based medical image segmentation are supervised models that require large amounts of fully annotated images. These types of datasets are typically not available in the medical domain and are difficult and expensive to generate. A wide-spread use of machine learning based models for medical image segmentation therefore requires the development of ...

    • Lie-Algebraic Approaches to Highly Symmetric Geometries 

      Winther, Henrik (Doctoral thesis; Doktorgradsavhandling, 2017-02-24)
      We facilitate the exploration and development of geometry by symmetry-based methods. To this end, we answer several natural questions that appear when considering symmetries, for particular examples of geometries

    • Ligand Noninnocence In Manganese, Iron, and Cobalt Corroles 

      Ganguly, Sumit (Doctoral thesis; Doktorgradsavhandling, 2017-11-30)
      In recent years, first-row metallocorroles have provided some of the most instructive examples of noninnocent ligands. This thesis presents a study of some 50 iron, manganese, and cobalt corrole complexes with different axial ligands (including approximately 30 new compounds and 6 new X-ray structures) with emphasis on their noninnocent/innocent character. UV-vis spectroscopy has for some time ...

    • Lithostratigraphy and chemostratigraphy of Triassic black shales on Edgeøya, eastern Svalbard: Implications for understanding Triassic source rock formation on the Norwegian Barents Shelf 

      Wesenlund, Fredrik (Doctoral thesis; Doktorgradsavhandling, 2022-03-25)
      The Norwegian Barents Shelf (NBS) is an Arctic petroleum province with a complex geological history. Current geochemical work on oil discoveries in the region has identified Triassic mudstones as important petroleum source rocks. A review of the published literature found that several source rock-forming processes have been suggested as contributors to their formation. The aim of this thesis is thus ...