Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 2401-2420 of 5368
-
How Does El Niño–Southern Oscillation Change Under Global Warming—A First Look at CMIP6
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-22)The latest generation of coupled models, the sixth Coupled Models Intercomparison Project (CMIP6), is used to study the changes in the El Niño–Southern Oscillation (ENSO) in a warming climate. For the four future scenarios studied, the sea surface temperature variability increases in most CMIP6 models, but to varying degrees. This increase is linked to a weakening of the east‐west temperature gradient ... -
Waveguide-based Excitation for High-throughput Imaging
(Doctoral thesis; Doktorgradsavhandling, 2021-03-24)Chip–based fluorescence imaging is an emerging field where the fluorophores in a sample are excited by the evanescent field generated by waveguides. The aim of this thesis is to explore how waveguide–based excitation can benefit super–resolution optical microscopy, as well as investigate other imaging and spectroscopic applications which can benefit from the same platform. For all imaging and ... -
Trapped Particle Motion In Magnetodisc Fields
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-13)The spatial and temporal characterization of trapped charged particle trajectories in magnetospheres has been extensively studied in dipole magnetic field structures. Such studies have allowed the calculation of spatial quantities, such as equatorial loss cone size as a function of radial distance, the location of the mirror points along particular field lines (<i>L</i>‐shells) as a function of the ... -
Vaccination criteria based on factors influencing COVID-19 diffusion and mortality
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-15)SARS-CoV-2 is highly contagious, rapidly turned into a pandemic, and is causing a relevant number of critical to severe life-threatening COVID-19 patients. However, robust statistical studies of a large cohort of patients, potentially useful to implement a vaccination campaign, are rare. We analyzed public data of about 19,000 patients for the period 28 February to 15 May 2020 by several mathematical ... -
Photonic-chip assisted correlative light and electron microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)Correlative light and electron microscopy (CLEM) unifies the versatility of light microscopy (LM) with the high resolution of electron microscopy (EM), allowing one to zoom into the complex organization of cells. Here, we introduce photonic chip assisted CLEM, enabling multi-modal total internal reflection fluorescence (TIRF) microscopy over large field of view and high precision localization of the ... -
In-Silico Evaluation of Glucose Regulation Using Policy Gradient Reinforcement Learning for Patients with Type 1 Diabetes Mellitus
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-11)In this paper, we test and evaluate policy gradient reinforcement learning for automated blood glucose control in patients with Type 1 Diabetes Mellitus. Recent research has shown that reinforcement learning is a promising approach to accommodate the need for individualized blood glucose level control algorithms. The motivation for using policy gradient algorithms comes from the fact that adaptively ... -
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 ...