Now showing items 223-242 of 392

    • Nanoscopy of bacterial cells immobilized by holographic optical tweezers 

      Diekmann, Robin; Wolfson, Deanna; Spahn, Christoph; Heilemann, Mike; Schuttpelz, Mark; Huser, Thomas (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-13)
      Imaging non-adherent cells by super-resolution far-field fluorescence microscopy is currently not possible because of their rapid movement while in suspension. Holographic optical tweezers (HOTs) enable the ability to freely control the number and position of optical traps, thus facilitating the unrestricted manipulation of cells in a volume around the focal plane. Here we show that immobilizing ...
    • New capabilities of the upgraded EISCAT high-power HF facility 

      Rietveld, Michael T; Senior, Andrew; Markkanen, Jussi; Westman, Assar (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-22)
      The high-power HF (high-frequency) facility (commonly known as Heating) near Tromsø, Norway, which is an essential part of the European Incoherent Scatter Scientific Association, has been upgraded in certain key areas in recent years. It is one of only four similar facilities in the world operating at present. An updated description of the facility is given, together with scientific motivation and ...
    • A new method of inferring the size, number density, and charge of mesospheric dust from its in situ collection by the DUSTY probe 

      Havnes, Ove; Antonsen, Tarjei; Baumgarten, Gerd; Hartquist, Thomas W.; Biebricher, Alexander; Fredriksen, Åshild; Friedrich, Martin; Hedin, Jonas (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-15)
      <p>We present a new method of analyzing measurements of mesospheric dust made with DUSTY rocket-borne Faraday cup probes. It can yield the variation in fundamental dust parameters through a mesospheric cloud with an altitude resolution down to 10 cm or less if plasma probes give the plasma density variations with similar height resolution. A DUSTY probe was the first probe that unambiguously detected ...
    • New ways of looking at very small holes – using optical nanoscopy to visualize liver sinusoidal endothelial cell fenestrations 

      Øie, Cristina Ionica; Mönkemöller, Viola; Hübner, Wolfgang; Schüttpelz, Mark; Mao, Hong; Ahluwalia, Balpreet Singh; Huser, Thomas Rolf; McCourt, Peter Anthony (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-10)
      Super-resolution fluorescence microscopy, also known as nanoscopy, has provided us with a glimpse of future impacts on cell biology. Far-field optical nanoscopy allows, for the first time, the study of sub-cellular nanoscale biological structures in living cells, which in the past was limited to electron microscopy (EM) (in fixed/dehydrated) cells or tissues. Nanoscopy has particular utility in the ...
    • Next-generation Space Object Radar Tracking Simulator: SORTS++ 

      Kastinen, D; Vierinen, Juha; Kero, Johan; Hesselbach, S; Grydeland, Tom; Krag, Holger (Journal article; Tidsskriftartikkel, 2019)
      We describe the software toolbox SORTS++ which is the next-generation Space Object Radar Tracking Simulator (SORTS). This toolbox is able to simulate general Space Surveillance and Tracking (SST) applications from catalogue maintenance to cold-start performance for radar systems or collections of radar systems. We have applied this toolbox to the EISCAT 3D radar system, currently under construction, ...
    • Non-Gaussian Clustering of SAR images for Glacier Change Detection 

      Eltoft, Torbjørn; Akbari, Vahid; Doulgeris, Anthony Paul (Conference object; Konferansebidrag, 2010)
    • Non-gaussian clustering of SAR images for glacier change detection 

      Akbari, Vahid; Doulgeris, Anthony Paul; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel, 2010-12)
      Our aim is to use unsupervised, non-Gaussian clustering of Arctic glaciers for post-classification change detection. Firstly, we demonstrate the consistency of non-Gaussian clustering algorithms for Envisat ASAR images by characterizing the expected random error level for different SAR acquisition conditions (such as incidence angle). This allows us to determine whether an observed variation is ...
    • Non-heuristic automatic techniques for overcoming low signal-to-noise-ratio bias of localization microscopy and multiple signal classification algorithm 

      Agarwal, Krishna; Macháň, Radek; Prasad, Dilip Kumar (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-21)
      Localization microscopy and multiple signal classification algorithm use temporal stack of image frames of sparse emissions from fluorophores to provide super-resolution images. Localization microscopy localizes emissions in each image independently and later collates the localizations in all the frames, giving same weight to each frame irrespective of its signal-to-noise ratio. This results in a ...
    • Non-Oberbeck-Boussinesq zonal flow generation 

      Held, M; Wiesenberger, M; Kube, Ralph; Kendl, Alexander (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-26)
      Novel mechanisms for zonal flow (ZF) generation for both large relative density fluctuations and background density gradients are presented. In this non-Oberbeck–Boussinesq (NOB) regime ZFs are driven by the Favre stress, the large fluctuation extension of the Reynolds stress, and by background density gradient and radial particle flux dominated terms. Simulations of a nonlinear full-F gyro-fluid ...
    • Non-triggered auroral substorms and long-period (1–4 mHz) geomagnetic and auroral luminosity pulsations in the polar cap 

      Yagova, Nadezda; Nosikova, Natalia; Baddeley, Lisa; Kozyreva, Olga; Lorentzen, Dag A.; Pilipenko, Vyacheslav; Johnsen, Magnar G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-08)
      A study is undertaken into parameters of the polar auroral and geomagnetic pulsations in the frequency range 1– 4 mHz (Pc5/Pi3) during quiet geomagnetic intervals preceding auroral substorms and non-substorm background variations. Special attention is paid to substorms that occur under parameters of the interplanetary magnetic field (IMF) conditions typical for undisturbed days (“non-triggered ...
    • Nonlocal damage mechanics for quantification of health for piezoelectric sensor 

      Habib, Anowarul; Shelke, Amit; Amjad, U; Pietsch, Ullrich; Banerjee, S (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-18)
      In this paper, a novel method to quantify the incubation of damage on piezoelectric crystal is presented. An intrinsic length scale parameter obtained from nonlocal field theory is used as a novel measure for quantification of damage precursor. Features such as amplitude decay, attenuation, frequency shifts and higher harmonics of guided waves are commonly-used damage features. Quantification of the ...
    • Nordlys i verdensrommet 

      Havnes, Ove (Journal article; Tidsskriftartikkel, 1980)
      Vi vil ikke her gå inn i nordlyset som vi kjenner det fra jorden, men kort omtale andre steder i verdensrommet hvor vi har observert nordlyslignende fenomen eller hvor vi kan vente å finne beslektede fenomen.
    • Nordlysobservatoriet i dag 

      Solheim, Jan-Erik (Journal article; Tidsskriftartikkel, 1980)
      Da Det Norske Institutt for Kosmisk Fysikk ble del av Universitetet i Tromsø, opphørte Nordlysobservatoriet å eksistere som en formell enhet. Det som i dag omfattes av Nordlysobservatoriet, er dels en fortsettelse av den opprinnelige observasjonsvirksomheten til det gamle Nordlysobservatoriet - men også nye aktiviteter har kommet til - særlig innen feltene plasmafysikk og radiogeofysikk. I det ...
    • Nordområdeprosjektet EISCAT 

      Brekke, Asgeir (Chronicle; Kronikk, 2011)
    • A novel code for numerical 3-D MHD studies of CME expansion 

      Kopp, A.; Kleimann, Jens; Fichtner, H.; Grauer, R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)
    • Novel specular meteor radar systems using coherent MIMO techniques to study the mesosphere and lower thermosphere 

      Chau, J. L.; Urco, Miguel; Vierinen, Juha; Volz, Ryan; Clahsen, Matthias; Pfeffer, Nico; Trautner, Jörg (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-05)
      Typical specular meteor radars (SMRs) use one transmitting antenna and at least a five-antenna interferometric configuration on reception to study the mesosphere and lower thermosphere (MLT) region. The interferometric configuration allows the measurement of the angle-of-arrival (AOA) of the detected meteor echoes, which in turn is needed to derive atmospheric parameters (e.g., mean winds, momentum ...
    • Numerical Analysis of Microwave Scattering from Layered Sea Ice Based on the Finite Element Method 

      Xu, Xu; Brekke, Camilla; Doulgeris, Anthony Paul; Melandsø, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-21)
      A two-dimensional scattering model based on the Finite Element Method (FEM) is built for simulating the microwave scattering of sea ice, which is a layered medium. The scattering problem solved by the FEM is formulated following a total- and scattered-field decomposition strategy. The model set-up is first validated with good agreements by comparing the results of the FEM with those of the small ...
    • Numerical and experimental evaluation of high-frequency unfocused polymer transducer arrays 

      Habib, Anowarul; Wagle, Sanat; Decharat, Adit; Melandsø, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-12)
      High-frequency unfocused polymer array transducers are developed using an adhesive-free layer-by-layer assembly method. The current paper focuses on experimental and numerical methods for measuring the acoustic performance of these types of array transducers. Two different types of numerical approaches were used to simulate the transducer performance, including a finite element method (FEM) study ...
    • Numerical Simulation of Microwave Scattering from Sea Ice Based on The Finite Element Method 

      Xu, Xu; Doulgeris, Anthony Paul; Melandsø, Frank; Brekke, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-03)
      In this paper, a 2-dimensional scattering model for sea ice based on the Finite Element Method (FEM) is presented. The scattering problem is formulated following a physics-separate strategy. The wave in the air domain is expressed by the scattered field formulation, while the wave in the sea ice domain is expressed by the total field formulation. The two separate physics and formulations are coupled ...
    • Object-based detection of linear kinematic features in sea ice 

      Linow, Stefanie; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-18)
      Inhomogenities in the sea ice motion field cause deformation zones, such as leads, cracks and pressure ridges. Due to their long and often narrow shape, those structures are referred to as Linear Kinematic Features (LKFs). In this paper we specifically address the identification and characterization of variations and discontinuities in the spatial distribution of the total deformation, which ...