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norskFakultet for naturvitenskap og teknologi
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Synthesis and Molecular Structure of a Copper Octaiodocorrole
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-09)Although rather delicate on account of their propensity to undergo deiodination, β-octaiodoporphyrinoids are of considerable interest as potential precursors to novel β-octasubstituted macrocycles. Presented herein are early results of our efforts to synthesize β-octaiodocorrole derivatives. Oxidative condensation of 3,4-diiodopyrrole and aromatic aldehydes failed to yield free-base octaiodocorroles. ... -
Quaternary interaction of cryospheric and oceanographic processes along the central-east Greenland margin
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-16)The east Greenland margin has been influenced by oceanographic and cryospheric processes since the late Miocene, when the southwards flow of the East Greenland Current (EGC) initiated and ice sheets first advanced across the margin. However, the relative importance of these processes, and their influence on the sedimentation of the margin through time remains poorly understood. High‐resolution ... -
Outlier classification using autoencoders: Application for fluctuation driven flows in fusion plasmas
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-16)Understanding the statistics of fluctuation driven flows in the boundary layer of magnetically confined plasmas is desired to accurately model the lifetime of the vacuum vessel components. Mirror Langmuir probes (MLPs) are a novel diagnostic that uniquely allow us to sample the plasma parameters on a time scale shorter than the characteristic time scale of their fluctuations. Sudden large-amplitude ... -
Statistical properties of the plasma fluctuations and turbulent cross-field fluxes in the outboard mid-plane scrape-off layer of Alcator C-Mod
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-29)The Alcator C-Mod mirror Langmuir probe diagnostic is used to characterize plasma fluctuations in the outboard mid-plane scrape-off layer (SOL). Ohmically heated L-mode plasmas with Greenwald fractions from 0.1 to 0.45 are analyzed. In plasmas with a low line-averaged core density, the radial profiles of the average electron density and temperature feature a two-scale structure with a strong gradient ... -
Modelling persistent methane seepage offshore western Svalbard since early Pleistocene
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-31)Recent observations of extensive methane release into the oceans and atmosphere have raised concern as to whether rising temperatures across the Arctic could drive rapid destabilization of gas hydrate reservoirs. Here, we report modelling results from hydrate-modulated methane seepage from Vestnesa Ridge, offshore western Svalbard, suggesting that continuous leakage has occurred from the seafloor ... -
An assessment of biomarker-based multivariate classification methods versus the PIP25 index for paleo Arctic sea ice reconstruction
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-30)The development of various combinative methods for Arctic sea ice reconstruction using the sympagic highly-branched isoprenoid (HBI) IP<sub>25</sub> in conjunction with pelagic biomarkers has often facilitated more detailed descriptions of sea ice conditions than using IP<sub>25</sub> alone. Here, we investigated the application of the Phytoplankton-IP<sub>25</sub> index (PIP<sub>25</sub>) and a ... -
Live-cell imaging of human spermatozoa using structured illumination microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-05)Structural details of spermatozoa are interesting from the perspectives of fundamental biology and growing reproductive health problems. Studies of nanostructural details of these extremely motile cells have been limited to fixed cells, largely using electron microscopy. Here we provide the protocols for and demonstrate live-cell multi-color super-resolution imaging of human spermatozoa using ... -
Reflection groups, arrangements, and invariant real varieties
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-10-18)Let <i>X</i> be a nonempty real variety that is invariant under the action of a reflection group <i>G</i>. We conjecture that if <i>X</i> is defined in terms of the first <i>k</i> basic invariants of <i>G</i> (ordered by degree), then <i>X</i> meets a <i>k</i>-dimensional flat of the associated reflection arrangement. We prove this conjecture for the infinite types, reflection groups of rank at most ... -
DNA binding with a minimal scaffold: structure-function analysis of Lig E DNA ligases
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-11)DNA ligases join breaks in the phosphodiester backbone of DNA by catalysing the formation of bonds between opposing 5′P and 3′OH ends in an adenylation-dependent manner. Catalysis is accompanied by reorientation of two core domains to provide access to the active site for cofactor utilization and enable substrate binding and product release. The general paradigm is that DNA ligases engage their DNA ... -
Evaluation of feature ranking and regression methods for oceanic chlorophyll-a estimation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-22)This paper evaluates two alternative regression techniques for oceanic chlorophyll-a (Chl-a) content estimation. One of the investigated methodologies is the recently introduced Gaussian process regression (GPR) model. We explore two feature ranking methods derived for the GPR model, namely sensitivity analysis (SA) and automatic relevance determination (ARD). We also investigate a second ... -
On the Isotypic Decomposition of Cohomology Modules of Symmetric Semi-algebraic Sets: Polynomial Bounds on Multiplicities
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-30)We consider symmetric (under the action of products of finite symmetric groups) real algebraic varieties and semi-algebraic sets, as well as symmetric complex varieties in affine and projective spaces, defined by polynomials of degrees bounded by a fixed constant <i>d</i>. We prove that if a Specht module, S<sup>λ</sup>, appears with positive multiplicity in the isotypic decomposition of the ... -
On the equivariant Betti numbers of symmetric definable sets: vanishing, bounds and algorithms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-02)Let R be a real closed field. We prove that for any fixed <i>d</i>, the equivariant rational cohomology groups of closed symmetric semi-algebraic subsets of R<sup><i>k</i></sup> defined by polynomials of degrees bounded by <i>d</i> vanishes in dimensions <i>d</i> and larger. This vanishing result is tight. Using a new geometric approach we also prove an upper bound of [mathematical formula] on the ... -
Method for detection of leads from Sentinel-1 SAR images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-05)The presence of leads with open water or thin ice is an important feature of the Arctic sea ice cover. Leads regulate the heat, gas and moisture fluxes between the ocean and atmosphere and are areas of high ice growth rates during periods of freezing conditions. Here, an algorithm providing an automatic lead detection based on synthetic aperture radar images is described that can be applied to a ... -
Assessing the performance of the BARCAST climate field reconstruction technique for a climate with long-range memory
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-29)The skill of the state-of-the-art climate field reconstruction technique BARCAST (Bayesian Algorithm for Reconstructing Climate Anomalies in Space and Time) to reconstruct temperature with pronounced long-range memory (LRM) characteristics is tested. A novel technique for generating fields of target data has been developed and is used to provide ensembles of LRM stochastic processes with a prescribed ... -
Enzyme mechanism, thermostability, and structural studies of OXA-48 like carbapenemases involved in antibiotic resistance
(Master thesis; Mastergradsoppgave, 2018-05-15)Antibiotic resistance is being recognized as a world-wide crisis in modern medicine, rapidly outpacing available treatment options. The serine-beta-lactamase OXA-48 was first identified from a carbapenem- and multidrug- resistant Klebsiella pneumoniae isolate in Turkey in 2001, and is now one of the most geographically widespread members of the class D beta-lactamases. OXA-48 like beta-lactamases ... -
Solvent effect with Multiwavelets
(Master thesis; Mastergradsoppgave, 2017-11-15)This thesis contains the inclusion of solvent effect in the computational chemistry program MRChem. Water in water systems are of importance. -
Early and Middle Pleistocene environments, landforms and sediments in Scotland
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-04)This paper reviews the changing environments, developing landforms and terrestrial stratigraphy during the Early and Middle Pleistocene stages in Scotland. Cold stages after 2.7 Ma brought mountain ice caps and lowland permafrost, but larger ice sheets were short-lived. The late Early and Middle Pleistocene sedimentary record found offshore indicates more than 10 advances of ice sheets from ... -
Distribution of siderophore gene systems on a Vibrionaceae phylogeny: Database searches, phylogenetic analyses and evolutionary perspectives
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-14)Siderophores are small molecules synthesized and secreted by bacteria and fungi to scavenge iron. Extracellular ferri-siderohores are recognized by cognate receptors on the cell surface for transport over membranes. Several siderophore systems from <i>Vibrionaceae</i> representatives are known and well understood, e.g., the molecular structure of the siderophore, the biosynthesis gene cluster ... -
Quantification of the magnitude of net erosion in the southwest Barents Sea using sonic velocities and compaction trends in shales and sandstones
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-19)During specific intervals within Mesozoic and Cenozoic times, several areas of the southwestern Barents Sea were subjected to uplift and erosion. Areas with missing shallow stratigraphic interval sections and major erosion can be seen at several places along interpreted regional profiles in the southwestern Barents Sea. A new Normal Compaction Trend (NCT) for two selected shale– and ... -
Iron dependent gene regulation and siderophore systems in Vibrionaceae
(Doctoral thesis; Doktorgradsavhandling, 2017-03-15)Bacteria live in fluctuating environments, which they sense and respond to through gene regulation. Availably of iron is an example of an element fluctuating and that can Bacteria sense.Iron is an essential micronutrient that is scares in several environments, especially in a host. The ferric uptake regulator, Fur, is the major iron level sensing protein and regulator of iron acquisition systems in ...
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