Viser treff 121-140 av 389

    • Instance Segmentation of Microscopic Foraminifera 

      Johansen, Thomas Haugland; Sørensen, Steffen Aagaard; Møllersen, Kajsa; Godtliebsen, Gustav (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-16)
      Foraminifera are single-celled marine organisms that construct shells that remain as fossils in the marine sediments. Classifying and counting these fossils are important in paleo-oceanographic and -climatological research. However, the identification and counting process has been performed manually since the 1800s and is laborious and time-consuming. In this work, we present a deep learning-based ...
    • Classification of Simply-Transitive Levi Non-Degenerate Hypersurfaces in C^3 

      Doubrov, Boris; Merker, Joël; The, Dennis (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-24)
      Holomorphically homogeneous Cauchy–Riemann (CR) real hypersurfaces M<sup>3</sup>⊂C<sup>2</sup> were classified by Élie Cartan in 1932. In the next dimension, we complete the classification of simply-transitive Levi non-degenerate hypersurfaces M<sup>5</sup>⊂C<sup>3</sup> using a novel Lie algebraic approach independent of any earlier classifications of abstract Lie algebras. Central to our approach ...
    • Real Plane Algebraic Curves 

      González García, Pedro (Master thesis; Mastergradsoppgave, 2021-06-18)
      This master thesis studies several properties of real plane algebraic curves, focusing on the case of even degree. The question of the relative positions of the connected components of real plane algebraic curves originates in Hilbert's sixteenth problem which, despite its prominence, is still open in the case of higher degree curves. The goal of this thesis is an exposition of fundamental ...
    • Trans-dimensional inference over Bayesian neural networks 

      Berezowski, Jonathan (Master thesis; Mastergradsoppgave, 2021-06-03)
      Trans-dimensional Bayesian inference for multi-layer perceptron architectures of varying size by reversible jump Markov chain Monte Carlo is developed and examined for its theoretical and practical merits and considerations. The algorithm features the No-U-Turn Sampler and Hamiltonian Monte Carlo for within-dimension moves, and makes use of a delayed-rejection sampler while exploring a variety of ...
    • Symmetric Ideals 

      Lien, Arne (Mastergradsoppgave; Master thesis, 2021-05-14)
      Polynomials appear in many different fields such as statistics, physics and optimization. However, when the degrees or the number of variables are high, it generally becomes quite difficult to solve polynomials or to optimize polynomial functions. An approach that can often be helpful to reduce the complexity of such problems is to study symmetries in the problems. A relatively new field, that has ...
    • Estimation of Excess Mortality and Years of Life Lost to COVID-19 in Norway and Sweden between March and November 2020 

      Rypdal, Martin Wibe; Rypdal, Kristoffer; Løvsletten, Ola; Sørbye, Sigrunn Holbek; Ytterstad, Elinor; Bianchi, Filippo Maria (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-08)
      We estimate the weekly excess all-cause mortality in Norway and Sweden, the years of life lost (YLL) attributed to COVID-19 in Sweden, and the significance of mortality displacement. We computed the expected mortality by taking into account the declining trend and the seasonality in mortality in the two countries over the past 20 years. From the excess mortality in Sweden in 2019/20, we estimated ...
    • Machine Learning in Chronic Pain Research: A Scoping Review 

      Jenssen, Marit Dagny Kristine; Bakkevoll, Per Atle; Ngo, Phuong; Budrionis, Andrius; Fagerlund, Asbjørn Johansen; Tayefi, Maryam; Bellika, Johan Gustav; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-02)
      Given the high prevalence and associated cost of chronic pain, it has a significant impact on individuals and society. Improvements in the treatment and management of chronic pain may increase patients’ quality of life and reduce societal costs. In this paper, we evaluate state-of-the-art machine learning approaches in chronic pain research. A literature search was conducted using the PubMed, IEEE ...
    • Modelling suggests limited change in the reproduction number from reopening Norwegian kindergartens and schools during the COVID-19 pandemic 

      Rypdal, Martin Wibe; Rypdal, Veronika Gjertsen; Jakobsen, Per Kristen; Ytterstad, Elinor; Løvsletten, Ola; Klingenberg, Claus; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-25)
      <i>Background</i> - To suppress the COVID-19 outbreak, the Norwegian government closed all schools on March 13, 2020. The kindergartens reopened on April 20, and the schools on April 27 and May 11 of 2020. The effect of these measures is largely unknown since the role of children in the spread of the SARS-CoV-2 virus is still unclear. There are only a few studies of school closures as a separate ...
    • De-identifying Swedish EHR text using public resources in the general domain 

      Chomutare, Taridzo; Yigzaw, Kassaye Yitbarek; Budrionis, Andrius; Makhlysheva, Alexandra; Godtliebsen, Fred; Dalianis, Hercules (Journal article; Tidsskriftartikkel; Peer reviewed, 2020)
      Sensitive data is normally required to develop rule-based or train machine learning-based models for de-identifying electronic health record (EHR) clinical notes; and this presents important problems for patient privacy. In this study, we add non-sensitive public datasets to EHR training data; (i) scientific medical text and (ii) Wikipedia word vectors. The data, all in Swedish, is used to train a ...
    • Challenges and opportunities beyond structured data in analysis of electronic health records 

      Tayefi, Maryam; Ngo, Phuong; Chomutare, Taridzo; Dalianis, Hercules; Salvi, Elisa; Budrionis, Andrius; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-14)
      Electronic health records (EHR) contain a lot of valuable information about individual patients and the whole population. Besides structured data, unstructured data in EHRs can provide extra, valuable information but the analytics processes are complex, time-consuming, and often require excessive manual effort. Among unstructured data, clinical text and images are the two most popular and important ...
    • Higher weight spectra of codes from Veronese threefolds 

      Johnsen, Trygve; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-23)
      We study binary linear codes C obtained from the quadric Veronese embedding of P<sup>3</sup> in P<sup>9</sup> over F<sub>2</sub>. We show how one can find the higher weight spectra of these codes. Our method will be a study of the Stanley-Reisner rings of a series of matroids associated to each code <i>C</i>.
    • Joint Invariants of Linear Symplectic Actions 

      Andreassen, Fredrik; Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)
      We review computations of joint invariants on a linear symplectic space, discuss variations for an extension of group and space and relate this to other equivalence problems and approaches, most importantly to differential invariants.
    • Differential Invariants of Linear Symplectic Actions 

      Jensen, Jørn Olav; Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)
      We consider the equivalence problem for symplectic and conformal symplectic group actions on submanifolds and functions of symplectic and contact linear spaces. This is solved by computing differential invariants via the Lie-Tresse theorem.
    • Ice-albedo tipping points in a diffusive energy-balance model with land and ocean 

      Hilbertsen, Kristian Bergum (Mastergradsoppgave; Master thesis, 2021-01-20)
      The ice-albedo feedback is associated with the nonlinearity in the climate system, due to the sudden change in albedo between ice-free and ice-covered surfaces. This nonlinearity can potentially cause abrupt and dramatic shifts in the climate, referred to as tipping points. It is also believed that this mechanism has contributed significantly to the precipitous losses of Arctic sea ice, which have ...
    • Vaccination criteria based on factors influencing COVID-19 diffusion and mortality 

      Spassiani, Ilaria; Gubian, Lorenzo; Palu, Giorgio; Sebastiani, Giovanni (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 ...
    • G(3)-supergeometry and a supersymmetric extension of the Hilbert–Cartan equation 

      Kruglikov, Boris; Santi, Andrea; The, Dennis (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 ...
    • Hyperspectral imaging for the detection of glioblastoma tumor cells in H&E slides using convolution neural networks 

      Ortega, S.; Halicek, M.; Fabelo, H.; Camacho, R.S.; Plaza, M.L.; Godtliebsen, Fred; Callico, G. M.; Fei, Baowei (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 ...
    • Towards detection and classification of microscopic foraminifera using transfer learning 

      Johansen, Thomas Haugland; Sørensen, Steffen Aagaard (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-06)
      <p>Foraminifera are single-celled marine organisms, which may have a planktic or benthic lifestyle. During their life cycle they construct shells consisting of one or more chambers, and these shells remain as fossils in marine sediments. Classifying and counting these fossils have become an important tool in e.g. oceanography and climatology. <p>Currently the process of identifying and counting ...
    • Snow avalanche segmentation in SAR images with Fully Convolutional Neural Networks 

      Bianchi, Filippo Maria; Grahn, Jakob; Eckerstorfer, Markus; Malnes, Eirik; Vickers, Hannah (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-10)
      Knowledge about frequency and location of snow avalanche activity is essential for forecasting and mapping of snow avalanche hazard. Traditional field monitoring of avalanche activity has limitations, especially when surveying large and remote areas. In recent years, avalanche detection in Sentinel-1 radar satellite imagery has been developed to improve monitoring. However, the current state-of-the-art ...
    • Estimation of Blood Glucose Concentration During Endurance Sports 

      Sebastiani, Giovanni; Uteng, Stig; Godtliebsen, Fred; Polàk, Jan; Brož, Jan (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-21)
      In this paper, we describe a new statistical approach to estimate blood glucose concentration along time during endurance sports based on measurements of glucose concentration in subcutaneous interstitial tissue. The final goal is the monitoring of glucose concentration in blood to maximize performance in endurance sports. Blood glucose concentration control during and after aerobic physical ...