Now showing items 221-240 of 389

    • Penalised Complexity Priors for Stationary Autoregressive Processes 

      Sørbye, Sigrunn Holbek; Rue, Håvard (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-23)
      The autoregressive (AR) process of order p(AR(p)) is a central model in time series analysis. A Bayesian approach requires the user to define a prior distribution for the coefficients of the AR(p) model. Although it is easy to write down some prior, it is not at all obvious how to understand and interpret the prior distribution, to ensure that it behaves according to the users' prior knowledge. In ...
    • Jet-determination of symmetries of parabolic geometries 

      Kruglikov, Boris; The, Dennis (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-24)
      We establish 2-jet determinacy for the symmetry algebra of the underlying structure of any (complex or real) parabolic geometry. At non-flat points, we prove that the symmetry algebra is in fact 1-jet determined. Moreover, we prove 1-jet determinacy at any point for a variety of non-flat parabolic geometries—in particular torsion-free, parabolic contact, and several other classes.
    • Fractional Gaussian noise: Prior specification and model comparison 

      Sørbye, Sigrunn Holbek; Rue, Håvard (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-07)
      Fractional Gaussian noise (fGn) is a stationary stochastic process used to model anti-persistent or persistent dependency structures in observed time series. Properties of the autocovariance function of fGn are characterised by the Hurst exponent (<i>H)</i>, which in Bayesian contexts typically has been assigned a uniform prior on the unit interval. This paper argues why a uniform prior is ...
    • Non-degenerate para-complex structures in 6D with large symmetry groups 

      Kruglikov, Boris; Winther, Henrik (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-20)
      For an almost product structure J on a manifold M of dimension 6 with non-degenerate Nijenhuis tensor N J, we show that the automorphism group G=Aut(M,J) has dimension at most 14. In the case of equality G is the exceptional Lie group G∗2. The next possible symmetry dimension is proved to be equal to 10, and G has Lie algebra sp(4,R). Both maximal and submaximal symmetric structures are globally ...
    • Conformal differential invariants 

      Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-27)
      We compute the Hilbert polynomial and the Poincar´e function counting the number of fixed jet-order differential invariants of conformal metric structures modulo local diffeomorphisms, and we describe the field of rational differential invariants separating generic orbits of the diffeomorphism pseudogroup action. This resolves the local recognition problem for conformal structures.
    • Erratum to: Almost complex structures in 6D with nondegenerate Nijenhuis tensors and large symmetry groups 

      Kruglikov, Boris; Winther, Henrik (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-23)
      We correct an error in the second part of Theorem 3 of our original paper.
    • Statistical significance of rising and oscillatory trends in global ocean and land temperature in the past 160 years 

      Østvand, Lene; Rypdal, Kristoffer; Rypdal, Martin Wibe (Journal article; Tidsskriftartikkel, 2014-03-20)
      Various interpretations of the notion of a trend in the context of global warming are discussed, contrasting the difference between viewing a trend as the deterministic response to an external forcing and viewing it as a slow variation which can be separated from the background spectral continuum of long-range persistent climate noise. The emphasis in this paper is on the latter notion, and a general ...
    • Antarctic climate variability on regional and continental scales over the last 2000 years 

      Stenni, Barbara; Curran, Mark A.J.; Abram, Nerilie J.; Orsi, Anais; Goursaud, Sentia; Masson-Delmotte, Valerie; Neukom, Raphael; Goosse, Hugues; Divine, Dmitry V; Van Ommen, Tas; Steig, Eric J.; Dixon, Daniel A.; Thomas, Elizabeth R.; Bertler, Nancy A.N.; Isaksson, Elisabeth; Ekaykin, Alexey; Werner, Martin; Frezzotti, Massimo (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-17)
      Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. ...
    • Generalized Hamming Weights for Almost Affine Codes 

      Johnsen, Trygve; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-17)
      We define generalized Hamming weights for almost affine codes. We show that this definition is natural since we can extend some well known properties of t he generalized Hamming weights for linear codes, to almost affine codes. In addition we discus s duality of almost affine codes, and of the smaller class of multilinear codes.
    • Relative generalized hamming weights and extended weight polynomials of almost affine codes 

      Johnsen, Trygve; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-23)
      This paper is devoted to giving a generalization from linear codes to the larger class of almost affine codes of two different results. One such result is how one can express the relative generalized Hamming weights of a pair of codes in terms of intersection properties between the smallest of these codes and subcodes of the largest code. The other result tells how one can find the extended ...
    • A global multiproxy database for temperature reconstructions of the Common Era 

      Emile-Geay, Julien; McKay, Nicholas P; Kaufman, Darrell S; Von Gunten, Lucien; Wang, Jianghao; Anchukaitis, Kevin J; Abram, Nerilie J; Addison, Jason A; Curran, Mark AJ; Evans, Michael N; Henley, Benjamin J; Hao, Zhixin; Martrat, Belen; McGregor, Helen V; Neukom, Raphael; Pederson, Gregory T; Stenni, Barbara; Thirumalai, Kaustubh; Werner, Johannes P; Xu, Chenxi; Divine, Dmitry V; Dixon, Bronwyn C; Gergis, Joelle; Mundo, Ignacio A; Nakatsuka, Takeshi; Phipps, Steven J; Routson, Cody C; Steig, Eric J; Tierney, Jessica E; Tyler, Jonathan J; Allen, Kathryn J; Bertler, Nancy AN; Bjorklund, Jesper; Chase, Brian M; Chen, Min-Te; Cook, Ed; De Jong, Rixt; DeLong, Kristine L; Dixon, Daniel A; Ekaykin, Alexey A; Ersek, Vasile; Filipsson, Helena L; Francus, Pierre; Freund, Mandy B; Frezzotti, Massimo; Gaire, Narayan P; Gajewski, Konrad; Ge, Quansheng; Goosse, Hugues; Gornostaeva, Anastasia; Grosjean, Martin; Horiuchi, Kazuho; Hormes, Anne; Husum, Katrine; Isaksson, Elisabeth; Kandasamy, Selvaraj; Kawamura, Kenji; Kilbourne, K Halimeda; Koc, Nalan; Leduc, Guillaume; Linderholm, Hans W; Lorrey, Andrew M; Mikhalenko, Vladimir; Mortyn, P Graham; Motoyama, Hideaki; Moy, Andrew D; Mulvaney, Robert; Munz, Philipp M; Nash, David J; Oerter, Hans; Opel, Thomas; Orsi, Anais J; Ovchinnikov, Dmitriy V; Porter, Trevor J; Roop, Heidi A; Saenger, Casey; Sano, Masaki; Sauchyn, David; Saunders, Krystyna M; Seidenkrantz, Marit-Solveig; Severi, Mirko; Shao, Xuemei; Sicre, Marie-Alexandrine; Sigl, Michael; Sinclair, Kate; St George, Scott; St Jacques, Jeannine-Marie; Thamban, Meloth; Thapa, Udya Kuwar; Thomas, Elizabeth R; Turney, Chris; Uemura, Ryu; Viau, Andre E; Vladimirova, Diana O; Wahl, Eugene R; White, James WC; Yu, Zicheng; Zinke, Jens (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-11)
      Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records ...
    • Younger Dryas ice margin retreat triggered by ocean surface warming in central-eastern Baffin Bay 

      Oksman, Mimmi; Weckström, Kaarina; Miettinen, Arto; Juggins, Stephen; Divine, Dmitry V; Jackson, Rebecca; Telford, Richard; Korsgaard, Niels J.; Kučera, Michal (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-10-18)
      The transition from the last ice age to the present-day interglacial was interrupted by the Younger Dryas (YD) cold period. While many studies exist on this climate event, only few include high-resolution marine records that span the YD. In order to better understand the interactions between ocean, atmosphere and ice sheet stability during the YD, more high-resolution proxy records from the Arctic, ...
    • Does proximity of women to facilities with better choice of contraceptives affect their contraceptive utilization in rural Ethiopia? 

      Shiferaw, Solomon; Spigt, Mark; Seme, Assefa; Amogne, Ayanaw; Skrøvseth, Stein Olav; Desta, Selamawit; Radloff, Scott; Tsui, Amy; Dinant, Geert-Jan (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-13)
      Background:<br>There is limited evidence of the linkage between contraceptive use, the range of methods available and level of contraceptive stocks at health facilities and distance to facility in developing countries. The present analysis aims at examining the influence of contraceptive method availability and distance to the nearby facilities on modern contraceptive utilization among married women ...
    • Surface water conditions and calcium carbonate preservation in the Fram Strait during marine isotope stage 2, 28.8–15.4 kyr 

      Zamelczyk, Katarzyna; Rasmussen, Tine Lander; Husum, Katrine; Godtliebsen, Fred; Hald, Morten (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-14)
      We present a high-resolution record of calcium carbonate preservation alongside the distribution pattern of planktic foraminifera from the Fram Strait. The record covers the marine isotope stage (MIS) 2, 28.8 to 15.4 kyr, including the Last Glacial Maximum (LGM) and the early deglaciation in multidecadal temporal resolution. The investigation is based on the distribution patterns of planktic ...
    • Analysis of free text in electronic health records for identification of cancer patient trajectories 

      Jensen, Kasper; Soguero-Ruiz, Cristina; Mikalsen, Karl Øyvind; Lindsetmo, Rolv-Ole; Kouskoumvekaki, Irene; Girolami, Mark; Skrovseth, Stein Olav; Augestad, Knut Magne (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-07)
      With an aging patient population and increasing complexity in patient disease trajectories, physicians are often met with complex patient histories from which clinical decisions must be made. Due to the increasing rate of adverse events and hospitals facing financial penalties for readmission, there has never been a greater need to enforce evidence-led medical decision-making using available ...
    • Using anchors from free text in electronic health records to diagnose postoperative delirium 

      Mikalsen, Karl Øyvind; Soguero-Ruiz, Cristina; Jensen, Kasper; Hindberg, Kristian; Gran, Mads; Revhaug, Arthur; Lindsetmo, Rolv-Ole; Skrøvseth, Stein Olav; Godtliebsen, Fred; Jenssen, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-19)
      Objectives:<br> Postoperative delirium is a common complication after major surgery among the elderly. Despite its potentially serious consequences, the complication often goes undetected and undiagnosed. In order to provide diagnosis support one could potentially exploit the information hidden in free text documents from electronic health records usin ...
    • Comparison of computer systems and ranking criteria for automatic melanoma detection in dermoscopic images 

      Møllersen, Kajsa; Zortea, Maciel; Schopf, Thomas Roger Griesbeck; Kirchesch, Herbert M.; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-21)
      Melanoma is the deadliest form of skin cancer, and early detection is crucial for patient survival. Computer systems can assist in melanoma detection, but are not widespread in clinical practice. In 2016, an open challenge in classification of dermoscopic images of skin lesions was announced. A training set of 900 images with corresponding class labels and semi-automatic/manual segmentation masks ...
    • Leakage from medically-certified to self-certified workplace absence among norwegian employees 

      Karlsen, Geir Runar; Ytterstad, Elinor (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-05)
      There are two different kinds of sickness absence in Norway: self-certified absence (SCA), and medically-certified absence (MCA). In this study of 6437 Norwegian employees, we applied logistic regression models for a dichotomous SCA variable on initially 38 independent vari- ables including age and gender. Our findings showed that employees reporting long-term health issues but no record of MCA ...
    • Elemental carbon measurements in European Arctic snow packs 

      Forsström, S.; Isaksson, Elisabeth; Skeie, Ragnhild Bieltvedt; Ström, Johan; Pedersen, CA; Hudson, S.R.; Berntsen, Terje Koren; Lihavainen, H.; Godtliebsen, Fred; Gerland, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-12-26)
      Black carbon (BC) and other light-absorbing particles deposited on snow and ice are known to perturb the surface radiative balance. There are few published observations of the concentration of these particles in the snow in Scandinavia and the European Arctic. We measured BC concentrations in snow samples collected in this region from 2007 to 2009, and we present the results here. The data set ...
    • Dynamic self-organisation of haematopoiesis and (a)symmetric cell division 

      Måløy, Marthe; Måløy, Frode; Jakobsen, Per; Brandsdal, Bjørn Olav (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-05)
      A model of haematopoiesis that links self-organisation with symmetric and asymmetric cell division is presented in this paper. It is assumed that all cell divisions are completely random events, and that the daughter cells resulting from symmetric and asymmetric stem cell divisions are, in general, phenotypically identical, and still, the haematopoietic system has the flexibility to self-renew, ...