Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 3321-3340 of 5336
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An Improved Spatial and Temporal Reflectance Unmixing Model to Synthesize Time Series of Landsat-Like Images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-31)The trade-off between spatial and temporal resolution limits the acquisition of dense time series of Landsat images, and limits the ability to properly monitor land surface dynamics in time. Spatiotemporal image fusion methods provide a cost-efficient alternative to generate dense time series of Landsat-like images for applications that require both high spatial and temporal resolution images. The ... -
Evolution in H2O contents during deformation of polycrystalline quartz: An experimental study
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-15)Shear experiments were performed in a Griggs-type apparatus at 800 °C and 1.5 GPa, at a strain rate of 2.1 × 10<sup>−5</sup>s<sup>−1</sup> using different starting materials: (i) Powder (grain size 6–10 μm) of dry Brazil quartz with 0.15 wt% added H<sub>2</sub>O, (ii) “dry” Brazil quartz porphyroclasts (grain size ∼100–200 μm), devoid of fluid inclusions embedded in the same fine grained powder, and ... -
Sea ice segmentation using Tandem-X pursuit mono static and alternative bistatic modes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)In this paper we investigate interferometric pairs of SAR images acquired by Tandem-X with the monostatic pursuit and the alternative bistatic modes for sea ice segmentation. The individual SAR images are modelled as non-Gaussian, and from the modelled data different features are extracted, stacked together and clustered. The interferometric coherence is regarded as an additional feature and utilized ... -
Cryptic frenulates are the dominant chemosymbiotrophic fauna at Arctic and high latitude Atlantic cold seeps
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-28)We provide the first detailed identification of Barents Sea cold seep frenulate hosts and their symbionts. Mitochondrial COI sequence analysis, in combination with detailed morphological investigations through both light and electron microscopy was used for identifying frenulate hosts, and comparing them to Oligobrachia haakonmosbiensis and Oligobrachia webbi, two morphologically similar species ... -
Fault-controlled asymmetric landscapes and low-relief surfaces on Vestvågøya, Lofoten, North Norway: inherited Mesozoic rift-margin structures?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-20)The Lofoten Ridge is an integral basement horst of the hyperextended continental rift-margin off northern Norway. It is a key area for studying onshore–offshore rift-related faults, and for evaluating tectonic control on landscape development along the North Atlantic margin. This paper combines onshore geomorphological relief/aspect data and fault/fracture analysis with offshore bathymetric and ... -
Geological controls on fluid flow and gas hydrate pingo development on the Barents Sea margin
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-16)In 2014, the discovery of seafloor mounds leaking methane gas into the water column in the northwestern Barents Sea became the first to document the existence of non‐permafrost related gas hydrate pingos (GHP) on the Eurasian Arctic shelf. The discovered site is given attention because the gas hydrates occur close to the upper limit of the gas hydrate stability, thus may be vulnerable to climatic ... -
In-situ Measurements of Mesospheric Aerosols - On the observable characteristics of nanoscale ice and meteoric smoke particles
(Doctoral thesis; Doktorgradsavhandling, 2019-01-24)Two sounding rocket payloads were launched from Andøya Space Centre (69.29 N, 16.02 E) during the summer of 2016 within the MAXIDUSTY campaign. Their payloads contained instrumentation aimed at investigating the characteristics of nanoscale aerosols in the upper summer mesosphere, and the role of these particles in phenomena like noctilucent clouds and polar mesospheric summer echoes (PMSE). The ... -
Evidences of accelerating the increase in the concentration of methane in the atmosphere after 2014: satellite data for the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017)Проанализированы результаты спутникового зондирования с помощью европейского орбитального интерферометра IASI/MetOP-A и алгоритма обработки данных, разработанного в NOAA. Спутниковые измерения для умеренных и высоких широт Северного полушария дают рост скорости концентрации метана от 4–9 ppbv/год (частей на миллиард по объему) в 2010–2013 гг. до 12–17 ppbv/год в 2015–2016 гг. Глобальные оценки на ... -
Application of Silicon-Initiated Water Splitting for the Reduction of Organic Substrates
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-06)The use of water as a donor for hydrogen suitable for the reduction of several important classes of organic compounds is described. It is found that the reductive water splitting can be promoted by several metalloids among which silicon shows the best efficiency. The developed methodologies were applied for the reduction of nitro compounds, N‐oxides, sulfoxides, alkenes, alkynes, hydrodehalogenation ... -
Change of the high-latitude ionosphere during heating by a powerful short radio wave of the EISCAT/Heating complex according to signals of the GLONASS satellite and the incoherent scattering radar
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018)Results of observations of variations of temperature, electron concentration and total electron content of the high-latitude region of the ionosphere during its modification by powerful short radio waves of the heating complex EISCAT/Heating (Tromsø, Norway) according to signals of the GLONASS satellites and the incoherent scattering UHF EISCAT radar (Tromsø, Norway) have been provided. The geometry ... -
Methane bubbles in the Arctic Ocean. Quantification, variability analysis and modelling of free and dissolved methane from the seafloor to the atmosphere
(Doctoral thesis; Doktorgradsavhandling, 2018-11-09)Intensive but heterogeneous and transient seepage of methane (CH4) bubbles from the seafloor exist west of Prins Karls Forland (PKF), offshore western Svalbard. The powerful greenhouse gas CH4, has 32 times higher warming potential than carbon dioxide (CO2) and if seepage of CH4 from the seafloor reaches the atmosphere, it will contribute to the warming climate. Warming of the oceans may in turn, ... -
Insight into the fluorescence quenching of Trp214 at HSA by the Dimetridazole ligand from simulation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-24)Spectroscopy is an important tool for detecting drug binding to amino acid sequences. One such important spectroscopic process is the fluorescence quenching due to charge transfer (CT) processes between a drug molecule and the chromophore center of Human Serum Albumin (HSA). We present a theoretical investigation of the CT occurring upon electronic excitation when a dimetridazole (Dmz) molecule ... -
Design and development of a context-aware knowledge-based module for identifying relevant information and information gaps in patients with type 1 diabetes self-collected health data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-11)<p><i>Background</i>: Patients with diabetes use an increasing number of self-management tools in their daily life. However, health institutions rarely use the data generated by these services mainly due to (1) the lack of data reliability, and (2) medical workers spending too much time extracting relevant information from the vast amount of data produced. This work is part of the FullFlow project, ... -
Exceptionally simple PDE
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-08)We give local descriptions of parabolic contact structures and show how their flat models yield explicit PDE having symmetry algebras isomorphic to all complex simple Lie algebras except <math><msub is="true"><mrow is="true"><mi mathvariant="fraktur" is="true">sl</mi></mrow><mrow is="true"><mn is="true">2</mn></mrow></msub></math>. This yields a remarkably uniform generalization of the Cartan–Engel ... -
Spreading of drill cuttings and sediment recovery of three exploration wells of different ages, SW Barents Sea, Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-14)Five stations (≤250 m from the well heads) from three exploration wells of different ages from the SW Barents Sea were studied to investigate the spreading of drill cuttings and sediment quality. Two of the wells were drilled before the restriction of use of oil-based drilling fluids (1993). Elevated concentrations of Ba were found in sediments near all the wells with the highest concentrations ... -
Iron‐Catalyzed Carbenoid Transfer Reactions of Vinyl Sulfoxonium Ylides: An Experimental and Computational Study
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-15)A method for the generation of unprecedented vinyl carbenoids from sulfoxonium ylides has been developed and applied in the synthesis of a diverse array of heterocycles such as indolizines, pyrroles, 3‐pyrrolin‐2‐ones, and furans. The reactions proceed by FeBr<sub>2</sub> catalysis under mild reaction conditions with a broad substrate scope. A reaction pathway involving iron carbenoids is proposed ... -
Ionospheric Response Observed by EISCAT During the 6–8 September 2017 Space Weather Event: Overview
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-03)We present ionospheric plasma conditions observed by the EISCAT radars in Tromsø and on Svalbard, covering 68°–81° geomagnetic latitude, during 6–8 September 2017. This is a period when X2.2 and X9.3 X‐ray flares occurred, two interplanetary coronal mass ejections (ICMEs) arrived at the Earth accompanied by enhancements of MeV‐range energetic particle flux in both the solar wind (SEP event) and inner ... -
Rhodium-Catalyzed Hydrocarboxylation: Mechanistic Analysis Reveals Unusual Transition State for Carbon–Carbon Bond Formation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-12)The mechanism of rhodium-COD-catalyzed hydrocarboxylation of styrene derivatives and α,β-unsaturated carbonyl compounds with CO<sub>2</sub> has been investigated using density functional theory (PBE-D2/IEFPCM). The calculations support a catalytic cycle as originally proposed by Mikami and co-workers including β-hydride elimination, insertion of the unsaturated substrate into a rhodium–hydride bond, ... -
Mutational analysis of the pro-peptide of a marine intracellular subtilisin protease supports its role in inhibition
(Journal article; Tidsskriftartikkel, 2018-06-16)Intracellular subtilisin proteases (ISPs) have important roles in protein processing during the stationary phase in bacteria. Their unregulated protein degrading activity may have adverse effects inside a cell, but little is known about their regulatory mechanism. Until now, ISPs have mostly been described from <i>Bacillus</i> species, with structural data from a single homolog. Here, we study a ... -
Cordilleran ice-sheet growth fueled primary productivity in the Gulf of Alaska, northeast Pacific Ocean
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-15)Fertilization of the ocean by eolian dust and icebergs is an effective mechanism to enhance primary productivity. In particular, high-nutrient, low-chlorophyll (HNLC) areas where phytoplankton growth is critically iron-limited, such as the subarctic Pacific Ocean and the Southern Ocean, are proposed to respond to increases in bioavailable Fe supply with enhanced phytoplankton productivity and carbon ...