Fakultet for naturvitenskap og teknologi: Nye registreringer
Viser treff 2401-2420 av 5362
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Biochemical characterization of ferric uptake regulator (Fur) from Aliivibrio salmonicida. Mapping the DNA sequence specificity through binding studies and structural modelling
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-09)Iron is an essential nutrient for bacteria, however its propensity to form toxic hydroxyl radicals at high intracellular concentrations, requires its acquisition to be tightly regulated. Ferric uptake regulator (Fur) is a metal-dependent DNA-binding protein that acts as a transcriptional regulator in maintaining iron metabolism in bacteria and is a highly interesting target in the design of new ... -
G(3)-supergeometry and a supersymmetric extension of the Hilbert–Cartan equation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-23)We realize the simple Lie superalgebra <i>G</i>(3) as supersymmetry of various geometric structures, most importantly super-versions of the Hilbert–Cartan equation (SHC) and Cartan's involutive PDE system that exhibit <i>G</i>(2) symmetry. We provide the symmetries explicitly and compute, via the first Spencer cohomology groups, the Tanaka–Weisfeiler prolongation of the negatively graded Lie ... -
Extraordinary evanescent field confinement waveguide sensor for mid-infrared trace gas spectroscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-29)Nanophotonic waveguides are at the core of a great variety of optical sensors. These structures confine light along defined paths on photonic chips and provide light–matter interaction via an evanescent field. However, waveguides still lag behind free-space optics for sensitivity-critical applications such as trace gas detection. Short optical pathlengths, low interaction strengths, and spurious ... -
Hyperspectral imaging for the detection of glioblastoma tumor cells in H&E slides using convolution neural networks
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-30)Hyperspectral imaging (HSI) technology has demonstrated potential to provide useful information about the chemical composition of tissue and its morphological features in a single image modality. Deep learning (DL) techniques have demonstrated the ability of automatic feature extraction from data for a successful classification. In this study, we exploit HSI and DL for the automatic differentiation ... -
Late Pleistocene-Holocene history of Svalbard ice caps and glaciers – integrating marine, terrestrial and lacustrine archives
(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 ... -
On Automated Classification of Sea Ice Types in SAR Imagery
(Doctoral thesis; Doktorgradsavhandling, 2021-03-12)With the Arctic sea ice continuously decreasing in both extent and thickness, fast and robust production of reliable ice charts becomes more important to ensure the safety of Arctic operations. This thesis focuses on the development of automated algorithms for the mapping of sea ice from synthetic aperture radar (SAR) images. It presents a thorough background on the topics of sea ice observations ... -
Incident Angle Dependence of Sentinel-1 Texture Features for Sea Ice Classification
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-04)Robust and reliable classification of sea ice types in synthetic aperture radar (SAR) images is needed for various operational and environmental applications. Previous studies have investigated the class-dependent decrease in SAR backscatter intensity with incident angle (IA); others have shown the potential of textural information to improve automated image classification. In this work, we investigate ... -
Determination of the Dielectric Properties of Marine Surface Slicks Using Synthetic Aperture Radar
(Doctoral thesis; Doktorgradsavhandling, 2021-03-03)Over the course of the last three decades, Synthetic Aperture Radar (SAR) has proven itself to be an effective monitoring technology for marine applications. The clear benefits of using SAR as opposed to optical devices is that SAR is insensitive to cloud cover, lighting conditions and can also provide imagery to a high degree of resolution. Given these benefits, there is a large incentive to implement ... -
Wind at Northern Senja: Use of numerical weather prediction models for wind resource assessment
(Master thesis; Mastergradsoppgave, 2020-12-15)Wind resource assessment for establishing decentralized power production in remote and complex areas, is challenging due to a lack of observational data. To overcome this problem, Numerical Weather Prediction (NWP) models can be used to provide data where no observations exist. This thesis uses NWP models to do a wind resource assessment at northern Senja. The power grid in the area is prone to ... -
Veikimorener i Norrbotten, Nord-Sverige – dødislandskap og morenebelter fra siste istid. Geomorfologisk tilnærming og GPR-profilanalyse av veikimorener innen den nordligste buen av veikimorenebeltet – Lainiobuen
(Master thesis; Mastergradsoppgave, 2020-12-30)Skandinavias glasiasjonshistorie er enda ikke kontinuerlig sammensatt for weichselistiden. I forhold til det fennoskandiske isskjoldet har nye studier avdekket alternative geokronologiske tolkninger for tidlig og midt weichsel i Nord-Sverige. Veikimorenelandskapet ble dannet over en stadial-interstadial syklus korrelert til tidlig weichsel av Lagerbäck (1988). Dette motstrides av moderne vitenskapelige ... -
Structure and mechanism of a phage-encoded SAM lyase revises catalytic function of enzyme family
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-10)The first S-adenosyl methionine (SAM) degrading enzyme (SAMase) was discovered in bacteriophage T3, as a counter-defense against the bacterial restriction-modification system, and annotated as a SAM hydrolase forming 5’ methyl-thioadenosine (MTA) and L-homoserine. From environmental phages, we recently discovered three SAMases with barely detectable sequence similarity to T3 SAMase and without ... -
Biomarker and isotopic composition of seep carbonates record environmental conditions in two Arctic methane seeps
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-12)Present-day activity of cold-seeps in the ocean is evident from direct observations of methane emanating from the seafloor, the presence of chemosynthetic organisms, or the quantification of gas concentrations in the water column and pore water solutes. Verifying past cold seep activity and biogeochemical characteristics is more challenging but may be reconstructed from proxy records of authigenic ... -
CO2 Increase Experiments Using the CESM: Relationship to Climate Sensitivity and Comparison of CESM1 to CESM2
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-14)We examine the response of the Community Earth System Model Versions 1 and 2 (CESM1 and CESM2) to abrupt quadrupling of atmospheric CO2 concentrations (4xCO2) and to 1% annually increasing CO2 concentrations (1%CO2). Different estimates of equilibrium climate sensitivity (ECS) for CESM1 and CESM2 are presented. All estimates show that the sensitivity of CESM2 has increased by 1.5 K or more over that ... -
Vibrational spectroscopy beyond the harmonic approximation with the Polarizable Embedding model
(Doctoral thesis; Doktorgradsavhandling, 2021-02-23)In order to efficiently and accurately calculate vibrational properties for solvated systems, a theoretical framework for combining response theory with the Polarizable Embedding model (PE) has been derived and implemented, and is presented in this thesis. An open-ended recursive formalism is utilized through the implementation in OpenRSP, allowing energy-derivatives to be calculated analytically ... -
Environmental variability off NE Greenland (western Fram Strait) during the past 10,600 years
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)To reconstruct the climatic and paleoceanographic variability offshore Northeast Greenland during the last ~10 ka with multidecadal resolution, sediment core PS93/025 from the outermost North-East Greenland continental shelf (80.5°N) was studied by a variety of micropaleontological, sedimentological and isotopic methods. High foraminiferal fluxes, together with high proportions of ice-rafted debris ... -
Dinocyst stratigraphy of the Valanginian to Aptian succession (the Rurikfjellet and Helvetiafjellet formations) from Spitsbergen, Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-11)In order to improve the understanding of how the high northern latitudes responded to the escalating warming which led to the middle Cretaceous super greenhouse climate, more temperature proxy records from the High Arctic are needed. One of the current obstacles in obtaining such records is poor age control on the Lower Cretaceous strata in the Boreal region. Here, we provide a biostratigraphic ... -
Passive seismic recording of cryoseisms in Adventdalen, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-20)A series of transient seismic events were discovered in passive seismic recordings from 2-D geophone arrays deployed at a frost polygon site in Adventdalen, Svalbard. These events contain a high proportion of surface wave energy and produce high-quality dispersion images using an apparent offset re-sorting and inter-trace delay minimisation technique to locate the seismic source, followed by ... -
Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard
(Journal article; Tidsskriftartikkel, 2020-11-10)The Svalbard margin represents one of the northernmost gas hydrate provinces worldwide. Vestnesa Ridge (VR) and Svyatogor Ridge (SR) west of Svalbard are two prominent sediment drifts showing abundant pockmarks and sites of seismic chimney structures. Some of these sites at VR are associated with active gas venting and were the focus of drilling and coring with the seafloor‐deployed MARUM‐MeBo70 ... -
Evolution of a shear zone before, during and after melting
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-03)Partial melt in the deforming mid- or lower continental crust causes a strength decrease and drives formation of lithological heterogeneities. However, mechanisms of formation of syn-melt deformation zones and strain partitioning in partially molten rock remain poorly understood. We use field and microstructural observations to unravel the evolution of a partial melt shear zone, Seiland Igneous ... -
Klimanøytral miljøpark – en vurdering av kostnader og nytteverdi for klimagassreduserende tiltak
(Master thesis; Mastergradsoppgave, 2020-12-14)Remiks AS har gjennom flere år gjort en kartlegging av klimagassutslipp knyttet til egen virksomhet. På bakgrunn av dette er det iverksatt flere tiltak på aktuelle områder som har blitt identifisert. Det er i midlertidig ikke sikkert at investeringene som er gjort er de mest effektive tiltakene om man vurderer kostnadene mot klimanytten. Denne studien vil vurdere tiltakene solenergi, biodrivstoff, ...