Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 2081-2100 of 5378
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Structural and biochemical characterization of the environmental MBLs MYO-1, ECV-1 and SHD-1
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-28)Background: MBLs form a large and heterogeneous group of bacterial enzymes conferring resistance to b-lactam antibiotics, including carbapenems. A large environmental reservoir of MBLs has been identified, which can act as a source for transfer into human pathogens. Therefore, structural investigation of environmental and clinically rare MBLs can give new insights into structure–activity relationships ... -
CryoSat-2 Significant Wave Height in Polar Oceans Derived Using a Semi-Analytical Model of Synthetic Aperture Radar 2011–2019
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-18)This paper documents the retrieval of significant ocean surface wave heights in the Arctic Ocean from CryoSat-2 data. We use a semi-analytical model for an idealised synthetic aperture satellite radar or pulse-limited radar altimeter echo power. We develop a processing methodology that specifically considers both the Synthetic Aperture and Pulse Limited modes of the radar that change close to ... -
Probability distributions for wind speed volatility characteristics: A case study of Northern Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11)The Norwegian Arctic is rich in wind resources. The development of wind power in this region can boost green energy and also promote local economies. In wind power engineering, it is a tremendous advantage to base projects on a sound understanding of the intrinsic properties of wind resources in an area. Wind speed volatility, a phenomenon that strongly affects wind power generation, has not received ... -
Single-shot fringe pattern phase retrieval using improved period-guided bidimensional empirical mode decomposition and Hilbert transform
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-17)Fringe pattern analysis is the central aspect of numerous optical measurement methods, e.g., interferometry, fringe projection, digital holography, quantitative phase microscopy. Experimental fringe patterns always contain significant features originating from fluctuating environment, optical system and illumination quality, and the sample itself that severely affect analysis outcome. Before the ... -
Rapid Atlantification along the Fram Strait at the beginning of the 20th century
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-24)The recent expansion of Atlantic waters into the Arctic Ocean represents undisputable evidence of the rapid changes occurring in this region. Understanding the past variability of this “Atlantification” is thus crucial in providing a longer perspective on the modern Arctic changes. Here, we reconstruct the history of Atlantification along the eastern Fram Strait during the past 800 years using ... -
A Parsimonious Description and Cross-Country Analysis of COVID-19 Epidemic Curves
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-06)In a given country, the cumulative death toll of the first wave of the COVID-19 epidemic follows a sigmoid curve as a function of time. In most cases, the curve is well described by the Gompertz function, which is characterized by two essential parameters, the initial growth rate and the decay rate as the first epidemic wave subsides. These parameters are determined by socioeconomic factors and ... -
A 10-year record of Arctic summer sea ice freeboard from CryoSat-2
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-29)Satellite observations of pan-Arctic sea ice thickness have so far been constrained to winter months. For radar altimeters, conventional methods cannot differentiate leads from meltwater ponds that accumulate at the ice surface in summer months, which is a critical step in the ice thickness calculation. Here, we use over 350 optical and synthetic aperture radar (SAR) images from the summer months ... -
Putative fossils of chemotrophic microbes preserved in seep carbonates from Vestnesa Ridge, off northwest Svalbard, Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-20)The microbial key players at methane seeps are methanotrophic archaea and sulfate-reducing bacteria. They form spherical aggregates and jointly mediate the sulfate-dependent anaerobic oxidation of methane (SD–AOM: CH4 + SO42– → HCO3– + HS– + H2O), thereby inducing the precipitation of authigenic seep carbonates. While seep carbonates constitute valuable archives for molecular fossils of SD–AOM-mediating ... -
Sources and sinks of methane in sea ice: Insights from stable isotopes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-27)We report on methane (CH<sub>4)</sub> stable isotope (d<sup>13</sup>C and d<sup>2</sup> H) measurements from landfast sea ice collected near Barrow (Utqiagvik, Alaska) and Cape Evans (Antarctica) over the winter-to-spring transition. These measurements provide novel insights into pathways of CH<sub>4</sub> production and consumption in sea ice. We found substantial differences between the two ... -
Microstructure and fluid flow in the vicinity of basin bounding faults in rifts – The Dombjerg Fault, NE Greenland rift system
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-14)Faults commonly form loci for high fluid flux in sedimentary basins, where fluids, rocks and deformation processes frequently interact. Here, we elucidate the interaction of fluid flow, diagenesis and deformation near basin-bounding faults in sedimentary basins through a study in the vicinity (0–3.5 km) of the Dombjerg Fault in the NE Greenland rift system. Due to fault-controlled fluid circulation, ... -
Polar Lows - Moist Baroclinic Cyclones in Four Different Vertical Wind Shear Environments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-15)Polar lows are intense mesoscale cyclones that develop in polar marine air masses. Motivated by the large variety of their proposed intensification mechanisms, cloud structure, and ambient sub-synoptic environment, we use self-organising maps to classify polar lows. The method is applied to 370 polar lows in the north-eastern Atlantic, which were obtained by matching mesoscale cyclones from ... -
Estimating Remaining Carbon Budgets Using Temperature Responses Informed by CMIP6
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-12)A remaining carbon budget (RCB) estimates how much CO2 we can emit and still reach a specific temperature target. The RCB concept is attractive since it easily communicates to the public and policymakers, but RCBs are also subject to uncertainties. The expected warming levels for a given carbon budget has a wide uncertainty range, which increases with less ambitious targets, i.e., with higher CO2 ... -
Distinct methane-dependent biogeochemical states in Arctic seafloor gas hydrate mounds
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-02)Archaea mediating anaerobic methane oxidation are key in preventing methane produced in marine sediments from reaching the hydrosphere; however, a complete understanding of how microbial communities in natural settings respond to changes in the flux of methane remains largely uncharacterized. We investigate microbial communities in gas hydrate-bearing seafloor mounds at Storfjordrenna, offshore ... -
On Jordan classes for Vinberg's theta-groups
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-23)V. L. Popov has recently introduced an analogue of Jordan classes (packets or decomposition classes) for the action of a θ-group (G0, V), showing that they are finitely-many, locally-closed, irreducible unions of G0-orbits of constant dimension partitioning V. We carry out a local study of their closures showing that Jordan classes are smooth and that their closure is a union of Jordan classes. We ... -
A Green, Scalable, and Catalyst-Free One-Minute Synthesis of Quinoxalines
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-10)A highly efficient and catalyst-free protocol is reported for the synthesis of quinoxalines via the classical cyclocondensation reaction between aryldiamines and dicarbonyl compounds. Remarkably simple and green reaction conditions employing methanol as solvent afforded medium to excellent yield of quinoxalines after only one-minute reaction time at ambient temperature. The conditions allow at least ... -
Biosignal-Based Driving Skill Classification Using Machine Learning: A Case Study of Maritime Navigation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-19)This work presents a novel approach to detecting stress differences between experts and novices in Situation Awareness (SA) tasks during maritime navigation using one type of wearable sensor, Empatica E4 Wristband. We propose that for a given workload state, the values of biosignal data collected from wearable sensor vary in experts and novices. We describe methods to conduct a designed SA task ... -
File System Support for Privacy-Preserving Analysis and Forensics in Low-Bandwidth Edge Environments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-18)In this paper, we present initial results from our distributed edge systems research in the domain of sustainable harvesting of common good resources in the Arctic Ocean. Specifically, we are developing a digital platform for real-time privacy-preserving sustainability management in the domain of commercial fishery surveillance operations. This is in response to potentially privacy-infringing mandates ... -
Resilience Assessment: A Performance‐Based Importance Measure
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-12)The resilience of a system can be considered as a function of its reliability and recoverability. Hence, for effective resilience management, the reliability and recoverability of all components which build up the system need to be identified. After that, their importance should be identified using an appropriate model for future resource allocation. The critical infrastructures are under dynamic ... -
Unraveling the Impact of Land Cover Changes on Climate Using Machine Learning and Explainable Artificial Intelligence
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-15)A general issue in climate science is the handling of big data and running complex and computationally heavy simulations. In this paper, we explore the potential of using machine learning (ML) to spare computational time and optimize data usage. The paper analyzes the effects of changes in land cover (LC), such as deforestation or urbanization, on local climate. Along with green house gas emission, ... -
High-throughput spatial sensitive quantitative phase microscopy using low spatial and high temporal coherent illumination
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-04)High space-bandwidth product with high spatial phase sensitivity is indispensable for a single-shot quantitative phase microscopy (QPM) system. It opens avenue for widespread applications of QPM in the field of biomedical imaging. Temporally low coherence light sources are implemented to achieve high spatial phase sensitivity in QPM at the cost of either reduced temporal resolution or smaller field ...