Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 3821-3840 of 5327
-
Plasma cloud detection and diagnostics from arcing by conditional averaging
(Master thesis; Mastergradsoppgave, 2017-06-06)Plasma cloud formation from arcing is experimentally studied. The arcs are formed by a high voltage set-up in the space simulation chamber at UiT. The plasma clouds are observed as large structures in the time series recorded by Langmuir probe and reference probe. By using the method of conditional averaging, the structures are accentuated. The electron cloud formed by arcing was found to be ... -
Comparison of computer systems and ranking criteria for automatic melanoma detection in dermoscopic images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-21)Melanoma is the deadliest form of skin cancer, and early detection is crucial for patient survival. Computer systems can assist in melanoma detection, but are not widespread in clinical practice. In 2016, an open challenge in classification of dermoscopic images of skin lesions was announced. A training set of 900 images with corresponding class labels and semi-automatic/manual segmentation masks ... -
Structure, activity and thermostability investigations of OXA-163, OXA-181 and OXA-245 using biochemical analysis, crystal structures and differential scanning calorimetry analysis
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017)The first crystal structures of the class D β-lactamases OXA-181 and OXA-245 were determined to 2.05 and 2.20 Å resolution, respectively; in addition, the structure of a new crystal form of OXA-163 was resolved to 2.07 Å resolution. All of these enzymes are OXA-48-like and have been isolated from different clinical Klebsiella pneumoniae strains and also from other human pathogens such as Pseudomonas ... -
Correspondence: Reply to ‘Challenges with dating weathering products to unravel ancient landscapes’
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-15)As the title of the correspondence by Fossen et al. suggests, determining the age of landscape elements of the Earth surface is difficult. We thus welcome the opportunity to clarify our arguments on the contentious themes touched upon by Fredin et al. -
The inheritance of a Mesozoic landscape in western Scandinavia
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-28)In-situ weathered bedrock, saprolite, is locally found in Scandinavia, where it is commonly thought to represent pre-Pleistocene weathering possibly associated with landscape formation. The age of weathering, however, remains loosely constrained, which has an impact on existing geological and landscape evolution models and morphotectonic correlations. Here we provide new geochronological evidence ... -
Assessing impacts of simulated oil spills on the Northeast Arctic cod fishery
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-04)We simulate oil spills of 1500 and 4500 m3/day lasting 14, 45, and 90 days in the spawning grounds of the commercial fish species, Northeast Arctic cod. Modeling the life history of individual fish eggs and larvae, we predict deviations from the historical pattern of recruitment to the adult population due to toxic oil exposures. Reductions in survival for pelagic stages of cod were 0–10%, up to a ... -
Leakage from medically-certified to self-certified workplace absence among norwegian employees
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-05)There are two different kinds of sickness absence in Norway: self-certified absence (SCA), and medically-certified absence (MCA). In this study of 6437 Norwegian employees, we applied logistic regression models for a dichotomous SCA variable on initially 38 independent vari- ables including age and gender. Our findings showed that employees reporting long-term health issues but no record of MCA ... -
Laser Based Altimetry for Unmanned Aerial Vehicle Hovering Over a Snow Surface
(Master thesis; Mastergradsoppgave, 2017-06-02)A microwave radar for non-invasive snow stratigraphy measurements has been developed. Results were promising, but it failed to detect light powder snow in the air-snowpack interface. The aim of this thesis is to find and verify a system for estimating altitude on centimeter scale over a snow surface, independent of snow conditions. Also, relative pitch and roll angle estimation between the UAV and ... -
A comparison between optical and SAR classification results for thin sea ice in Storfjorden
(Master thesis; Mastergradsoppgave, 2017-05-31)According to the scientific consensus, the Arctic is currently in a state of unprecedented change. In recent years, climate change has been identified as the main cause of Arctic sea ice decline. For this reason, the need to have access to timely and cost effective data is of great importance. Remote sensing via Earth orbiting satellites offers extensive data coverage in areas that are typically ... -
Modeling Ice-shelf Ocean Interaction at Petermann Glacier, Greenland
(Master thesis; Mastergradsoppgave, 2017-05-15)Petermann Glacier drains about 4% of the Greenland ice sheet area, with at least 80% of its mass loss through basal melting of the floating ice shelf. Utilizing a high-resolution coupled ice-shelf-ocean model, we aim at understanding the ocean circulation in Nares Strait and the mechanism of oceanic heat supply below the ice shelf as well as quantifying the basal mass loss. The numerical model is ... -
Optimization of a polymer layer highly doped with Cryptophane-A for methane sensing
(Master thesis; Mastergradsoppgave, 2017-05-15)The main objective of this thesis is to optimize the thickness of sensitive polymer layer highly doped with Cryptophane-A for methane pre-concentration and to make the existing sensor more stable and selective towards methane. In recent years, methane detection has become a hot topic due to the strong impact of methane on the global warming and the climate change. There has also been rising ... -
Investigation of inflammatory response of macrophages and trophoblasts using structured illumination microscopy
(Master thesis; Mastergradsoppgave, 2017-05-15)Approximately 800 women die from pregnancy or childbirth-related pregnancy complications around the world every day. One of the major reasons for these complications is inflammation following infection. Approximately 40% cases of preterm births occur due to microbial invasion in the genitourinary track. During inflammation, macrophages present at the feto-maternal junction release an increased amount ... -
Novel aspects of pathogenicity of Aliivibrio salmonicida
(Doctoral thesis; Doktorgradsavhandling, 2014-06-19)Analysis of the fish health reports annually published online by the Norwegian Veterinary Institute (data available starting from 2005), have demonstrated a good epidemiological situation with Cold Water Vibriosis (CWV) in 2005-2010. During this 5 year period only 4 cases were detected in Norway. Starting from 2011 the situation began to change and only during 2011, 5 cases of CWV have been detected ... -
Eigen-analysis reveals components supporting super-resolution imaging of blinking fluorophores
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-30)This paper presents eigen-analysis of image stack of blinking fluorophores to identify the components that enable super-resolved imaging of blinking fluorophores. Eigen-analysis reveals that the contributions of spatial distribution of fluorophores and their temporal photon emission characteristics can be completely separated. While cross-emitter cross-pixel information of spatial distribution ... -
Acoustic generation of underwater cavities - Comparing modeled and measured acoustic signals generated by seismic air gun arrays
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-14)Underwater vapor cavities can be generated by acoustic stimulation. When the acoustic signals from several air guns are reflected from the sea surface, the pressure drop at some locations is sufficient for cavity growth and subsequent collapse. In this paper the generation of multiple water vapor cavities and their collapses are numerically modeled and the results are validated by comparing with ... -
Laser diagnostics of the mesospheric magnetic field. Understanding remote laser magnetometry in northern Norway
(Master thesis; Mastergradsoppgave, 2017-05-15)This thesis outlines initial motivations and propositions for the Mesospheric Optical Magnetometry (MOM) project, using lidar equipment at ALOMAR observatory in northern Norway to initiate a novel technique for measuring Earth’s magnetic field at approximately 90 km altitude. Included is an in-depth discussion of the physical phenomena within Earth’s mesospheric sodium layer, relevant atomic physics, ... -
Estimation of Neutral Densities in the Thermosphere
(Master thesis; Mastergradsoppgave, 2017-05-17)Ionospheric energy balance is studied with incoherent scatter radar measurements that allow the estimation of neutral density and temperature from a statistical inversion problem. This method has been successfully studied at low latitudes using data over several years to make a robust model. This has not been done within the high latitude auroral regions and there are many factors that can complicate ... -
Ligand Noninnocence In Manganese, Iron, and Cobalt Corroles
(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 ... -
Origins and impacts of spatial and temporal long-range dependence in the climate system
(Doctoral thesis; Doktorgradsavhandling, 2017-11-27)The internal variability of most Earth surface temperatures has a power spectral density well described by a power law, S(f) ~ f<sup>-β</sup>, and we typically observe 0 < β < 1. This characterizes variability exhibiting long-range dependence (LRD), which has no characteristic time scale. However, there is no consensus about the physical mechanisms behind this property, and the topic of this thesis ... -
Seepage from an arctic shallow marine gas hydrate reservoir is insensitive to momentary ocean warming
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-07)Arctic gas hydrate reservoirs located in shallow water and proximal to the sediment-water interface are thought to be sensitive to bottom water warming that may trigger gas hydrate dissociation and the release of methane. Here, we evaluate bottom water temperature as a potential driver for hydrate dissociation and methane release from a recently discovered, gas-hydrate-bearing system south of ...