Recent additions

  • Homogeneous Levi non-degenerate hypersurfaces in C^3 

    Doubrov, Boris; Medvedev, Alexandr; The, Dennis (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-09)
    We classify all (locally) homogeneous Levi non-degenerate real hypersurfaces in C<sup>3</sup> with symmetry algebra of dimension ≥6.
  • Higher Weight Spectra of Veronese Codes 

    Johnsen, Trygve; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-18)
    We study q-ary linear codes C obtained from Veronese surfaces over finite fields.We show how one can find the higher weight spectra of these codes, or equivalently, the weight distribution of all extension codes of C over all field extensions of the ground field. Our methods will be a study of the Stanley-Reisner rings of a series of matroids associated to each code C.
  • Spatial trend analysis of gridded temperature data at varying spatial scales 

    Haug, Ola; Thorarinsdottir, Thordis Linda; Sørbye, Sigrunn Holbek; Franzke, Christian L.E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-28)
    Classical assessments of trends in gridded temperature data perform independent evaluations across the grid, thus, ignoring spatial correlations in the trend estimates. In particular, this affects assessments of trend significance as evaluation of the collective significance of individual tests is commonly neglected. In this article we build a space–time hierarchical Bayesian model for temperature ...
  • Symmetric Non-Negative Forms and Sums of Squares 

    Blekherman, Grigoriy; Riener, Cordian (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-21)
    We study symmetric non-negative forms and their relationship with symmetric sums of squares. For a fixed number of variables <i>n</i> and degree 2<i>d</i>, symmetric non-negative forms and symmetric sums of squares form closed, convex cones in the vector space of <i>n</i>-variate symmetric forms of degree 2<i>d</i>. Using representation theory of the symmetric group we characterize both cones in a ...
  • Food recommendation using machine learning for physical activities in patients with type 1 diabetes 

    Ngo, Phuong; Tayefi, Maryam; Nordsletta, Anne Torill; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2019)
    Physical activities have a significant impact on blood glucose homeostasis of patients with type 1 diabetes. Regular physical exercise provides many proven health benefits and is recommended as part of a healthy lifestyle. However, one of the main side effects of physical activities is hypoglycemia (low blood glucose). Fear of hypoglycemia generally leads to the patients not participating in ...
  • Poincaré function for moduli of differential-geometric structures 

    Kruglikov, Boris (Journal article; Tidsskriftartikkel, 2019)
    The Poincaré function is a compact form of counting moduli in local geometric problems. We discuss its property in relation to V. Arnold’s conjecture, and derive this conjecture in the case when the pseudogroup acts algebraically and transitively on the base. Then we survey the known counting results for differential invariants and derive new formulae for several other classification problems in ...
  • Integrable Systems in Four Dimensions Associated with Six-Folds in Gr(4, 6) 

    Doubrov, Boris; Ferapontov, Evgeny V; Kruglikov, Boris; Novikov, Vladimir S (Journal article; Tidsskriftartikkel; Preprint; Manuskript, 2018-01-29)
    Let Gr(d, n) be the Grassmannian of <i>d</i>-dimensional linear subspaces of an <i>n</i>-dimensional vector space <i>V</i>. A submanifold <i>X</i> ⊂ Gr(<i>d, n</i>) gives rise to a differential system Σ(X) that governs <i>d</i>-dimensional submanifolds of <i>V</i> whose Gaussian image is contained in <i>X</i>. We investigate a special case of this construction where <i>X</i> is a six-fold in Gr(4, ...
  • Dispersionless integrable hierarchies and GL(2,R) geometry 

    Ferapontov, Evgeny V; Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-08)
    Paraconformal or GL(2, ℝ) geometry on an <i>n</i>-dimensional manifold <i>M</i> is defined by a field of rational normal curves of degree <i>n</i> – 1 in the projectivised cotangent bundle <i>ℙT*M</i>. Such geometry is known to arise on solution spaces of ODEs with vanishing Wünschmann (Doubrov–Wilczynski) invariants. In this paper we discuss yet another natural source of <i>GL</i>(2, ℝ) structures, ...
  • Differential invariants of Kundt waves 

    Kruglikov, Boris; McNutt, David Duncan; Schneider, Eivind (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-17)
    Kundt waves belong to the class of spacetimes which are not distinguished by their scalar curvature invariants. We address the equivalence problem for the metrics in this class via scalar differential invariants with respect to the equivalence pseudo-group of the problem. We compute and finitely represent the algebra of those on the generic stratum and also specify the behavior for vacuum Kundt ...
  • Relative profiles and extended weight polynomials of almost affine codes 

    Johnsen, Trygve; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2019)
    In this paper we study various aspects concerning almost affine codes, a class including, and strictly larger than, that of linear codes. We use the combinatorial tool demi-matroids to show how one can define relative length/dimension and dimension/length profiles of flags (chains) of almost affine codes. In addition we show two specific results. One such result is how one can express the relative ...
  • On the Ewald Oseen scattering formulation for light scattering: stability, singularity and parallelization. 

    Lin, Aihua; Jakobsen, Per Kristen (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-15)
    In this paper we discuss some of the mathematical and numerical issues that have to be addressed when calculating wave scattering using the Ewald Oseen scattering (EOS) formulation which is newly developed for solving linear and nonlinear scattering problems. The discussion is framed in context of light scattering by objects whose optical response can be of a nonlinear and/or inhomogeneous nature. ...
  • Warming trends and long-range dependent climate variability since year 1900: A Bayesian approach 

    Myrvoll-Nilsen, Eirik; Fredriksen, Hege-Beate; Sørbye, Sigrunn Holbek; Rypdal, Martin wibe (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-21)
    Temporal persistence in unforced climate variability makes detection of trends in surface temperature difficult. Part of the challenge is methodological since standard techniques assume a separation of time scales between trend and noise. In this work we present a novel Bayesian approach to trend detection under the assumption of long-range dependent natural variability, and we use estimates of ...
  • The effects of terlipressin and direct portacaval shunting on liver hemodynamics following 80% hepatectomy in the pig 

    Hammond, John S.; Godtliebsen, Fred; Steigen, Sonja Eriksson; Guha, I. Neil; Wyatt, Judy; Revhaug, Arthur; Lobo, Dileep N.; Mortensen, Kim Erlend (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-15)
    Liver failure is the major cause of death following liver resection. Post-resection portal venous pressure (PVP) predicts liver failure, is implicated in its pathogenesis, and when PVP is reduced, rates of liver dysfunction decrease. The aim of the present study was to characterize the hemodynamic, biochemical, and histological changes induced by 80% hepatectomy in non-cirrhotic pigs and determine ...
  • Quality of life in substance use disorder patients with and without attention deficit hyperactivity disorder 12 months after treatment: a naturalistic follow-up study 

    Flores, Lizbett; Lensing, Michael B.; Ytterstad, Elinor; Eisemann, Martin (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-22)
    There is sparse research on quality of life (QoL) as an outcome measure in patients with substance use disorders (SUD), with or without attention deficit hyperactivity disorder (ADHD). We aimed to investigate whether SUD patients with and without ADHD (SUD + ADHD vs. SUD − ADHD) differed in QoL at baseline and at a 12-month follow-up after SUD treatment. The groups were additionally compared with ...
  • Surface mass balance and stable oxygen isotope ratios from shallow firn cores on Fimbulisen, East Antarctica 

    Schlosser, E; Anschütz, Helgard; Isaksson, E.; Martma, T; Divine, Dmitry V; Nøst, O.-A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
    The mass balance of Antarctica is one of the crucial factors for determining sea-level change in a warming climate. The marginal zones of the continent, namely the ice shelves, are most sensitive to climate change. During the 2009/10 austral summer an extensive glaciological field campaign was carried out on Fimbulisen, an ice shelf in East Antarctica, to investigate its recent surface mass balance. ...
  • Recent advances in hyperspectral imaging for melanoma detection 

    Johansen, Thomas Haugland; Møllersen, Kajsa; Ortega, Samuel; Fabelo, Himar; Garcia, Aday; Callico, Gustavo; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-22)
    Skin cancer is one of the most common types of cancer. Skin cancers are classified as nonmelanoma and melanoma, with the first type being the most frequent and the second type being the most deadly. The key to effective treatment of skin cancer is early detection. With the recent increase of computational power, the number of algorithms to detect and classify skin lesions has increased. The overall ...
  • Arctic hydroclimate variability during the last 2000 years: current understanding and research challenges 

    Linderholm, Hans W.; Nicolle, Marie; Francus, Pierre; Gajewski, Konrad; Helama, Samuli; Korhola, Atte; Solomina, Olga; Yu, Zicheng; Zhang, Peng; D'Andrea, William J.; Debret, Maxime; Divine, Dmitry V; Gunnarson, Björn E.; Loader, Neil J.; Massei, Nicolas; Seftigen, Kristina; Thomas, Elizabeth K.; Werner, Johannes; Andersson, Sofia; Berntsson, Annika; Luoto, Tomi P.; Nevalainen, Liisa; Saarni, Saija; Väliranta, Minna (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-10)
    Reanalysis data show an increasing trend in Arctic precipitation over the 20th century, but changes are not homogenous across seasons or space. The observed hydroclimate changes are expected to continue and possibly accelerate in the coming century, not only affecting pan-Arctic natural ecosystems and human activities, but also lower latitudes through the atmospheric and ocean circulations. However, ...
  • Inter-outbreak stability reflects the size of the susceptible pool and forecasts magnitudes of seasonal epidemics 

    Rypdal, Martin Wibe; Sugihara, George (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-30)
    For dengue fever and other seasonal epidemics we show how the stability of the preceding inter-outbreak period can predict subsequent total outbreak magnitude, and that a feasible stability metric can be computed from incidence data alone. As an observable of a dynamical system, incidence data contains information about the underlying mechanisms: climatic drivers, changing serotype pools, the ecology ...
  • Maximizing Interpretability and Cost-Effectiveness of Surgical Site Infection (SSI) Predictive Models Using Feature-Specific Regularized Logistic Regression on Preoperative Temporal Data 

    Kocbek, Primoz; Fijacko, Nino; Soguero-Ruiz, Cristina; Mikalsen, Karl Øyvind; Maver, Uros; Brzan, Petra Povalej; Stozer, Andraz; Jenssen, Robert; Skrøvseth, Stein Olav; Stiglic, Gregor (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-19)
    This study describes a novel approach to solve the surgical site infection (SSI) classification problem. Feature engineering has traditionally been one of the most important steps in solving complex classification problems, especially in cases with temporal data. The described novel approach is based on abstraction of temporal data recorded in three temporal windows. Maximum likelihood L1-norm ...
  • 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 ...

View more