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norskFakultet for naturvitenskap og teknologi
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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 ... -
Systematic variation in observing altitude of enhanced ion line by the pump near fifth gyroharmonic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-20)The observation of ultra high frequency radar during an ionospheric experiment carrying out at the European Incoherent Scatter Scientific Association, demonstrates a systematic variation in the altitude of the pump enhanced ion line, which is quite remarkably dependent on the pump frequency, that is, when the pump frequency sweeps above the fifth gyroharmonic, the altitude of the enhanced ion line ... -
Evaluation of the Weather Research and Forecasting (WRF) model with respect to wind in complex terrain
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018)In this study the performance of the Weather Research and Forecast (WRF) model in a complex and coastal terrain has been evaluated with focus on wind resource assessment. The study area is a small community on the northern part of the island Senja, Norway. The community, with fishery and seafood as its main industry, is being limited by poor grid connection. One of the solutions is to increase ... -
Does your lab use social media? Sharing three years of experience in science communication
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-27)Effective science communication is essential to share knowledge and recruit the next generation of researchers. Science communication to the general public can, however, be hampered by limited resources and a lack of incentives in the academic environment. Various social media platforms have recently emerged, providing free and simple science communication tools to reach the public and young people ... -
The asymmetric geospace as displayed during the geomagnetic storm on 17 August 2001
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-29)Previous studies have shown that conjugate auroral features are displaced in the two hemispheres when the interplanetary magnetic field (IMF) has a transverse (<i><sub>Y</sub></i>) component. It has also been shown that a <i>B<sub>Y</sub></i> component is induced in the closed magnetosphere due to the asymmetric loading of magnetic flux in the lobes following asymmetric dayside reconnection when the ...
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