Now showing items 1-20 of 2271

    • A red tide in the pack ice of the Arctic Ocean 

      Olsen, Lasse Mork; Duarte, Pedro; Peralta-Ferriz, Cecilia; Kauko, Hanna Maria; Johansson, Malin; Peeken, Ilka; Różańska-Pluta, Magdalena; Tatarek, Agnieszka; Wiktor, Jozef; Fernández-Méndez, Mar; Wagner, Penelope Mae; Pavlov, Alexey K.; Hop, Haakon; Assmy, Phillipp (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-02)
      In the Arctic Ocean ice algae constitute a key ecosystem component and the ice algal spring bloom a critical event in the annual production cycle. The bulk of ice algal biomass is usually found in the bottom few cm of the sea ice and dominated by pennate diatoms attached to the ice matrix. Here we report a red tide of the phototrophic ciliate <i>Mesodinium rubrum</i> located at the ice-water interface ...
    • A 160,000-year-old history of tectonically controlled methane seepage in the Arctic 

      Himmler, Tobias; Sahy, Diana; Martma, Tõnu; Bohrmann, Gerhard; Plaza-Faverola, Andreia; Bünz, Stefan; Condon, Daniel J.; Knies, Jochen; Lepland, Aivo (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-07)
      The geological factors controlling gas release from Arctic deep-water gas reservoirs through seabed methane seeps are poorly constrained. This is partly due to limited data on the precise chronology of past methane emission episodes. Here, we use uranium-thorium dating of seep carbonates sampled from the seabed and from cores drilled at the Vestnesa Ridge, off West Svalbard (79°N, ~1200 m water ...
    • Improved CRISPR/Cas9 gene editing by fluorescence activated cell sorting of green fluorescence protein tagged protoplasts 

      Petersen, Bent Larsen; Möller, Svenning Rune; Mravec, Jozef; Jørgensen, Bodil; Christensen, Mikkel; Liu, Ying; Wandall, Hans H.; Bennett, Eric Paul; Yang, Zhang (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-17)
      <i>Background</i>: CRISPR/Cas9 is widely used for precise genetic editing in various organisms. CRISPR/Cas9 editing may in many plants be hampered by the presence of complex and high ploidy genomes and inefficient or poorly controlled delivery of the CRISPR/Cas9 components to gamete cells or cells with regenerative potential. Optimized strategies and methods to overcome these challenges are ...
    • Homogeneous integrable Legendrian contact structures in dimension five 

      Doubrov, Boris; Medvedev, Alexandr; The, Dennis (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-04)
      We consider Legendrian contact structures on odd-dimensional complex analytic manifolds. We are particularly interested in integrable structures, which can be encoded by compatible complete systems of second order PDEs on a scalar function of many independent variables and considered up to point transformations. Using the techniques of parabolic differential geometry, we compute the associated ...
    • Dust trajectory simulations around Sun, Vega, and Fomalhaut 

      Stamm, Johann Immanuel; Czechowski, Andrzej; Mann, Ingrid; Baumann, Carsten; Myrvang, Margaretha (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-20)
      <p><i>Context - </i>Vega and Fomalhaut display a thermal emission brightness that can possibly arise from hot dust near the stars, an inner extension of their planetary debris disks. There was brought up an idea that nm-sized dust particles are kept in the vicinity of the stars by electromagnetic forces. This resembles the trapping that model calculations show in the corotating magnetic field in the ...
    • Fully Polarizable QM/Fluctuating Charge Approach to Two-Photon Absorption of Aqueous Solutions 

      Di Remigio, Roberto; Giovannini, Tommaso; Ambrosetti, Matteo; Cappelli, Chiara; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-05)
      We present the extension of the quantum/classical polarizable fluctuating charge model to the calculation of single residues of quadratic response functions, as required for the computational modeling of two-photon absorption cross sections. By virtue of a variational formulation of the quantum/classical polarizable coupling, we are able to exploit an atomic orbital-based quasienergy formalism to ...
    • Anticlockwise metamorphic pressure–temperature paths and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower continental crust before and during continental collision 

      Faber, Carly; Stunitz, Holger; Gasser, Deta; Jeřábek, Petr; Kraus, Katrin; Corfu, Fernando; Ravna, Erling Krogh; Konopásek, Jiří (Journal article; Tidsskriftartikkel; Peer reviewed, 2019)
      This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kåfjord, and Nordmannvik nappes) in northern Troms, Norway. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure–temperature (<i>P–T</i>) conditions of deformation ...
    • The Origin of Gas Seeps in the Northern Adriatic Sea 

      Donda, Federica; Tinivella, Umberta; Gordini, Emiliano; Panieri, Giuliana; Volpi, Valentina; Civile, Dario; Forlin, Edy; Facchin, Lorenzo; Burca, Mihai; Cova, Andrea; Ferrante, Giulia M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06)
      A multidisciplinary approach has been used for the first time to study the widespread occurrence of hydrocarbon seeps in the northern Adriatic Sea. Geological, geophysical and geochemical analyses were performed to identify and characterize the gas-charged fluids occurring throughout the Plio-Quaternary succession, and to date the shallow gas seeping at three leakage sites. The analysis of CHIRP, ...
    • All-electron fully relativistic Kohn-Sham theory for solids based on the Dirac-Coulomb Hamiltonian and Gaussian-type functions 

      Kadek, Marius; Repisky, Michal; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-03)
      We present the first full-potential method that solves the fully relativistic four-component Dirac-Kohn-Sham equation for materials in the solid state within the framework of atom-centered Gaussian-type orbitals (GTOs). Our GTO-based method treats one-, two-, and three-dimensional periodic systems on an equal footing, and allows for a seamless transition to the methodology commonly used in studies ...
    • Palaeoceanographic reconstruction of surface-ocean changes in the southern Norwegian Sea for the last ~130,000 years based on diatoms and with comparison to foraminiferal records 

      Hoff, Ulrike; Rasmussen, Tine Lander; Meyer, Hanno; Koc, Nalan; Hansen, Jesper (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-28)
      Fossil marine diatom assemblages in a sediment core from the central northern Faroe slope in the Norwegian Sea were used to reconstruct palaeoceanographic changes in the surface water mixed layer from the last ~130,000 years (Marine Isotope Stage (MIS) 6/5 transition to MIS 1 (including the Eemian and Holocene interglacials) and to compare the results with previously published results on planktic ...
    • Morphological evidence for marine ice stream shutdown, central Barents Sea 

      Kurjanski, Bartosz; Rea, Brice R.; Spagnolo, Matteo; Winsborrow, Monica; Cornwell, David G.; Andreassen, Karin; Howell, John (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-02)
      Marine-based ice streams are responsible for a significant proportion of the ice mass loss from the present-day Greenland Ice Sheet, East Antarctic Ice Sheet (EAIS) and West Antarctic Ice Sheet (WAIS) but the processes controlling their initiation, evolution and shutdown remain elusive, hindering our understanding of how existing ice masses will respond to predicted future warming. The exposed beds ...
    • Reviewing the Cenozoic Net Erosion of the Barents Sea Shelf 

      Lasabuda, Amando Putra Ersaid; Laberg, Jan Sverre; Knutsen, Stig-Morten; Rydningen, Tom Arne (Conference object; Konferansebidrag, 2019-01)
    • Detection of meteoroid hypervelocity impacts on the Cluster spacecraft: First results 

      Vaverka, Jakub; Pellinen-Wannberg, Asta; Kero, Johan; Mann, Ingrid; De Spiegeleer, Alexandre; Hamrin, Maria; Norberg, Carol; Pitkaenen, Timo (Journal article; Peer reviewed, 2017-06-29)
      We present the first study of dust impact events on one of the Earth‐orbiting Cluster satellites. The events were identified in the measurements of the wide band data (WBD) instrument on board the satellite operating in monopole configuration. Since 2009 the instrument is operating in this configuration due to the loss of three electric probes and is therefore measuring the potential between the ...
    • Response properties of embedded molecules through the polarizable embedding model 

      Steinmann, Casper; Reinholdt, Peter; Nørby, Morten Steen; Kongsted, Jacob; Olsen, Jógvan Magnus Haugaard (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-04)
      The polarizable embedding (PE) model is a fragment‐based quantum‐classical approach aimed at accurate inclusion of environment effects in quantum‐mechanical response property calculations. The aim of this tutorial review is to give insight into the practical use of the PE model. Starting from a set of molecular structures and until you arrive at the final property, there are many crucial details to ...
    • Evidence of Isotopic Fractionation During Vapor Exchange Between the Atmosphere and the Snow Surface in Greenland 

      Madsen, M.V.; Steen‐Larsen, H.C.; Hörhold, M.; Box, J.; Berben, Sarah Miche Patricia; Capron, E.; Faber, Anne-Katrine; Hubbard, Alun Lloyd; Jensen, Mari Fjalstad; Jones, T.R.; Kipfstuhl, S.; Koldtoft, I.; Pillar, H.R.; Vaughn, B.H.; Vladimirova, D.; Dahl‐Jensen, D. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-18)
      Several recent studies from both Greenland and Antarctica have reported significant changes in the water isotopic composition of near‐surface snow between precipitation events. These changes have been linked to isotopic exchange with atmospheric water vapor and sublimation‐induced fractionation, but the processes are poorly constrained by observations. Understanding and quantifying these processes ...
    • Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge 

      Yao, Haoyi; Hong, Wei-Li; Panieri, Giuliana; Sauer, Simone; Torres, Marta E.; Lehmann, Moritz F.; Grüdger, Friederike; Niemann, Helge (Journal article; Peer reviewed, 2019-05-29)
      We report a rare observation of a mini-fracture in near-surface sediments (30 cm below the seafloor) visualized using a rotational scanning X-ray of a core recovered from the Lomvi pockmark, Vestnesa Ridge, west of Svalbard (1200 m water depth). Porewater geochemistry and lipid biomarker signatures revealed clear differences in the geochemical and biogeochemical regimes of this core compared with ...
    • MiMiC: A Novel Framework for Multiscale Modeling in Computational Chemistry 

      Olsen, Jógvan Magnus Haugaard; Bolnykh, Viacheslav; Meloni, Simone; Ippoliti, Emiliano; Bircher, Martin Peter; Carloni, Paolo; Rothlisberger, Ursula (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-18)
      We present a flexible and efficient framework for multiscale modeling in computational chemistry (MiMiC). It is based on a multiple-program multiple-data (MPMD) model with loosely coupled programs. Fast data exchange between programs is achieved through the use of MPI intercommunicators. This allows exploiting the existing parallelization strategies used by the coupled programs while maintaining a ...
    • Distribution and quantification of gas hydrates and free gas in marine sediments of Vestnesa Ridge, offshore W-Svalbard 

      Singhroha, Sunny (Doctoral thesis; Doktorgradsavhandling, 2019-06-18)
      Gas hydrates store a large amount of methane (>500 Gt of Carbon) in continental margins and permafrost environments. Some of these deposits occur in climate sensitive areas, such as Arctic and permafrost settings. Gas hydrates occur extensively in the Vestnesa Ridge, a contourite drift deposit on the western Svalbard margin. The eastern segment of the Vestnesa Ridge is characterized by the presence ...
    • Organic Matter Sources in North Atlantic Fjord Sediments 

      Faust, Johan Christoph; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-31)
      To better constrain the global carbon cycle fundamental knowledge of the role of carbon cycling on continental margins is crucial. Fjords are particularly important shelf areas for carbon burial due to relatively high sedimentation rates and high organic matter fluxes. As terrigenous organic matter is more resistant to remineralization than marine organic matter, a comprehensive knowledge of the ...
    • Constraints on Gas Hydrate Distribution and Morphology in Vestnesa Ridge, Western Svalbard Margin, Using Multicomponent Ocean‐Bottom Seismic Data 

      Singhroha, Sunny; Chand, Shyam; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-26)
      Gas hydrates occur within sediments on the western Svalbard continental margin and the Vestnesa Ridge, a large sediment drift that extends in a west‐north‐west direction from the margin towards the mid‐ocean ridge. We acquired multi‐component ocean‐bottom seismic (OBS) data at ten locations on the crest area of the eastern segment of the Vestnesa Ridge, an area with active gas seepage. P and S‐wave ...