Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 1081-1100 of 5404
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Extreme Event Statistics in Dst, SYM-H, and SMR Geomagnetic Indices
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-20)Extreme space weather events are rare, and quantifying their likelihood is challenging, often relying on geomagnetic indices obtained from ground-based magnetometer observations that span multiple solar cycles. The Dst index ring-current monitor, derived from an hourly average over four low-latitude stations, is a benchmark for extreme space weather events, and has been extensively studied ... -
Horizontal Correlation Functions of Wind Fluctuations in the Mesosphere and Lower Thermosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-01)Measurements of kinetic energy in vortical and divergent fluctuations in the mesosphere and lower thermosphere can be used to study stratified turbulence (ST) and gravity waves. This can be done using horizontal correlation functions of the fluctuating component of velocity. This study introduces a novel method for estimating these correlation functions using radars that observe Doppler shifts ... -
B12 and F430 models: Metal- versus ligand-centered redox in cobalt and nickel tetradehydrocorrin derivatives
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-23)DFT calculations with the well-tested OLYP and B3LYP* exchange-correlation functionals (along with D3 dispersion corrections and all-electron ZORA STO-TZ2P basis sets) and careful use of group theory have led to significant insights into the question of metal- versus ligand-centered redox in Co and Ni B,C-tetradehydrocorrin complexes. For the cationic complexes, both metals occur in their low-spin ... -
Gruppelærerdagen – undervisningskvalitet fra første time
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-25)Ved norske universiteter er det vanlig at stipendiater eller studenter fra tidligere kull utfører en stor del av undervisningen innen realfagene. Fokus på opplæring av denne gruppen undervisere kan bidra til en positiv effekt på undervisningskvalitet og studentenes læring. Det varierer imidlertid fra institusjon til institusjon om det finnes en slik type opplæring, og omfang og kvalitet på ... -
A Comparison of Arctic Ocean Sea Ice Export Between Nares Strait and the Canadian Arctic Archipelago
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-13)Nares Strait and the channels of the Canadian Arctic Archipelago (CAA) act as conduits for sea ice export from the Arctic Ocean but have never been directly compared. Here, we perform such a comparison for both the sea ice area and volume fluxes from October 2016 to December 2021. Nares Strait provided the largest average seasonal (October through September) ice area flux of 95 ± 8 × 10<sup>3</sup> ... -
Fossil organic carbon utilization in marine Arctic fjord sediments by subsurface micro-organisms
(Journal article; Tidsskriftartikkel, 2023)Rock-derived or petrogenic organic carbon has traditionally been regarded as being non-bioavailable and bypassing the active carbon cycle when eroded. However, it has become apparent that this organic carbon might not be so inert, especially in fjord systems where petrogenic organic carbon influxes can be high, making its degradation another potential source of greenhouse gas emissions. The extent ... -
Data-driven modeling of energy-exergy in marine engines by supervised ANNs based on fuel type and injection angle classification
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-16)The application of artificial neural networks with the involvement of a modified homogeneity factor to predict exergetic terms from combustive and/or mixing dynamics in a marine engine is considered in this study. This is a significant step since the mathematical formulation of exergy in combustion is complicated and even unconvincing due to the turbulent and highly nonlinear nature of the combustion ... -
Rhenium Biscorrole Sandwich Compounds: XAS Evidence for a New Coordination Motif
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-23)The interaction of three free-base meso-tris(p-X-phenyl)corroles H3[TpXPC] (X = H, CH3, OCH3) with Re2(CO)10 at 235 °C in the presence of K2CO3 in o-dichlorobenzene has led to putative rhenium biscorrole sandwich compounds with the formula ReH[TpXPC]2. Density functional theory calculations and Re L3-edge extended X-ray absorption fine structure measurements suggest a seven-coordinate metal center, ... -
Synoptic Variability in Satellite Altimeter-Derived Radar Freeboard of Arctic Sea Ice
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-09)Satellite observations of sea ice freeboard are integral to the estimation of sea ice thickness. It is commonly assumed that radar pulses from satellite-mounted Ku-band altimeters penetrate through the snow and reflect from the snow-ice interface. We would therefore expect a negative correlation between snow accumulation and radar freeboard measurements, as increased snow loading weighs the ice floe ... -
Transmission structured illumination microscopy with tunable frequency illumination using tilt mirror assembly
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-26)We present experimental demonstration of tilt-mirror assisted transmission structured illumination microscopy (tSIM) that offers a large field of view super resolution imaging. An assembly of custom-designed tilt-mirrors are employed as the illumination module where the sample is excited with the interference of two beams reflected from the opposite pair of mirror facets. Tunable frequency structured ... -
Stiffness tensor estimation of anisotropic crystal using point contact method and unscented Kalman filter
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-02)The potential application of Lithium Niobate (LiNbO3) crystal is immense, specifically in the domain of metasurfaces and nano-resonators. However, the practical application of LiNbO<sub>3</sub> is impeded due to unreliable experimental techniques and inaccurate inversion algorithms for material characterization. In the current research, material characterization of anisotropic crystal is proposed ... -
Image inpainting in acoustic microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-27)Scanning acoustic microscopy (SAM) is a non-ionizing and label-free imaging modality used to visualize the surface and internal structures of industrial objects and biological specimens. The image of the sample under investigation is created using high-frequency acoustic waves. The frequency of the excitation signals, the signal-to-noise ratio, and the pixel size all play a role in acoustic image ... -
The Perfluoro Cage Effect: A Search for Electron-Encapsulating Molecules
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-25)Quantum chemical calculations have for some time predicted that perfluorinated polyhedral organic molecules should exhibit a low-energy LUMO consisting of the overlapping inward-pointing lobes of the C−F σ* orbitals. Accordingly, these molecules should be able to encapsulate an electron within the interior of their cavities. Inspired by the recent confirmation of this prediction for perfluorocubane, ... -
The influence of different fuels and injection methods of RCCI and DCI in hybrid ICE-Battery vehicle performance
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-16)The incorporation of two recent technologies of using the dual-fuel reactivity controlled compression ignition (RCCI) combustion engine within the hybrid electric vehicle (HEV) is practiced to show how this combination can reduce the emission and enhance the thermal efficiency of the system. In particular, the heat transfers from the engine wall and the exhaust heat flow from the engine under ... -
Analysis of the impact of deploying thermal protective immersion suits on evacuation time for passenger ships operating in polar waters
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-22)For passenger vessels operating in polar waters, the Polar Code requires that in case of possibility of immersion in polar waters, thermal protective immersion suits (TPIS) should be available for all passengers. Thus, international standards require that TPIS can be donned within 2 min and that walking speeds are reduced by no more than 25%. Clearlythese requirements are arbitrary and do not ... -
A clinically motivated self-supervised approach for content-based image retrieval of CT liver images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-09)Deep learning-based approaches for content-based image retrieval (CBIR) of computed tomography (CT) liver images is an active field of research, but suffer from some critical limitations. First, they are heavily reliant on labeled data, which can be challenging and costly to acquire. Second, they lack transparency and explainability, which limits the trustworthiness of deep CBIR systems. We address ... -
Lignocellulose Conversion via Catalytic Transformations Yields Methoxyterephthalic Acid Directly from Sawdust
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-10)Poly(ethylene terephthalate) polyester represents the most common class of thermoplastic polymers widely used in the textile, bottling, and packaging industries. Terephthalic acid and ethylene glycol, both of petrochemical origin, are polymerized to yield the polyester. However, an earlier report suggests that polymerization of methoxyterephthalic acid with ethylene glycol provides a methoxy-polyester ... -
Investigation of tetrasubstituted heterocycles reveals hydantoins as a promising scaffold for development of novel antimicrobials with membranolytic properties
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-24)Mimics of antimicrobial peptides (AMPs) have been proposed as a promising class of antimicrobial agents. We report the analysis of five tetrasubstituted, cationic, amphipathic heterocycles as potential AMP mimics. The analysis showed that the heterocyclic scaffold had a strong influence on the haemolytic activity of the compounds, and the hydantoin scaffold was identified as a promising template for ... -
Highly sensitive quantitative phase microscopy and deep learning aided with whole genome sequencing for rapid detection of infection and antimicrobial resistance
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-12)Current state-of-the-art infection and antimicrobial resistance (AMR) diagnostics are based on culture-based methods with a detection time of 48–96 h. Therefore, it is essential to develop novel methods that can do real-time diagnoses. Here, we demonstrate that the complimentary use of label-free optical assay with whole-genome sequencing (WGS) can enable rapid diagnosis of infection and AMR. Our ... -
The Departure from Mixed-Layer Similarity During the Afternoon Decay of Turbulence in the Free-Convective Boundary Layer: Results from Large-Eddy Simulations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-21)This study analyses the departure of the velocity-variances profiles from their quasi-steady state described by the mixed-layer similarity, using large-eddy simulations with different prescribed shapes and time scales of the surface kinematic heat flux decay. Within the descriptive frames where the time is tracked solely by the forcing time scale (either constant or time-dependent) describing the ...