Viser treff 847-866 av 1261

    • Partially spatially coherent digital holographic microscopy and machine learning for quantitative analysis of human spermatozoa under oxidative stress condition 

      Dubey, Vishesh Kumar; Popova, Daria; Ahmad, Azeem; Acharya, Ganesh; Basnet, Purusotam; Mehta, Dalip Singh; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-05)
      Semen quality assessed by sperm count and sperm cell characteristics such as morphology and motility, is considered to be the main determinant of men’s reproductive health. Therefore, sperm cell selection is vital in assisted reproductive technology (ART) used for the treatment of infertility. Conventional bright field optical microscopy is widely utilized for the imaging and selection of sperm cells ...
    • Particle precipitation during NEIAL events : simultaneous ground based nighttime observations at Svalbard 

      Lunde, June; Løvhaug, Unni Pia; Gustavsson, Björn Johan (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)
    • Particle precipitations during NEIAL events : simultaneous ground based observations at Svalbard 

      Lorentzen, Dag Arne; Lunde, June; Gustavsson, B; Ogawa, Y; Løvhaug, U.P.; Ogawa, Yasunobu (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)
      In this paper we present Naturally Enhanced Ion Acoustic Lines (NEIALs) observed with the EISCAT Svalbard Radar (ESR). For the first time, long sequences of NEIALs are recorded, with more than 50 events within an hour, ranging from 6.4 to 140 s in duration. The events took place from ~08:45 to 10:00 UT, 22 January 2004. We combine ESR data with observations of optical aurora by a meridian scanning ...
    • Particle tracking in 3D 

      Brox, Petter (Master thesis; Mastergradsoppgave, 2013-06)
      The evanescent field of an optical waveguide can be used to trap and propel microscopic particles. A 1µm particle is trapped on a strip waveguide and propelled forward until it reaches a 10µm gap at the centre of a loop, created by splitting the waveguide into two branches. According to simulations, the particle will be elevated 3µm in the gap and be stably trapped in the middle of the gap. The goal ...
    • Patch Size Evolution During Pulsating Aurora 

      Partamies, Noora; Bolmgren, Karl; Heino, Erkka; Ivchenko, Nickolay; Borovsky, Joseph E.; Sundberg, Hanna (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-30)
      We report both decreasing and increasing trends in the patch sizes during pulsating aurora events. About 150 pulsating auroral events over the Fennoscandian Lapland have been successfully analyzed for their average patch size, total patch area, and number of patches as a function of event time, typically 1–2 hr. An automatic routine has been developed to detect patches in the all‐sky camera images. ...
    • Performance Analysis of Roll-Invariant PolSAR Parameters from C-band images with Regard to Sea Ice Type Separation 

      Ratha, Debanshu; Johansson, Malin; Marinoni, Andrea; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06)
      The Polarimetric Synthetic Aperture Radar (PolSAR) backscatter from a target is dependent on the incidence angle. Consequently, the associated roll invariant parameters are affected by changes in incidence angle. In this work, we identify a few of these parameters that remain robust in identifying sea ice features even under large incidence angle variations. We conclude that the helicity angle ...
    • Performance and Future Potential of Solar Photovoltaics in Arctic Settlements 

      Mathiesen, Vemund Nygaard (Master thesis; Mastergradsoppgave, 2020-12-15)
      Data from a solar photovoltaic (PV) installation on Svalbard Airport Longyear has been analyzed to investigate performance of solar photovoltaics in the Arctic. Results show that the average capacity factor at the facility is 5.6 % after its first two full years of production. While the production in the winter is zero, monthly capacity factors are observed to be as high as 16 % in the summer. On ...
    • Person Re-identification in Videos by Analyzing Spatio-temporal Tubes 

      Sekh, Arif Ahmed; Dogra, Debi Prasad; Choi, Heeseung; Chae, Seungho; Kim, Ig-Jae (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-23)
      Typical person re-identification frameworks search for <i>k</i> best matches in a gallery of images that are often collected in varying conditions. The gallery usually contains image sequences for video re-identification applications. However, such a process is time consuming as video re-identification involves carrying out the matching process multiple times. In this paper, we propose a new method ...
    • Phase calibration of the EISCAT Svalbard Radar interferometer using optical satellite signatures. 

      Grydeland, Tom; Sullivan, J.M.; Blixt, Erik Mårten; Ivchenko, N.; Lockwood, M.; Lanchester, B.S. (Journal article; Peer reviewed; Tidsskriftartikkel, 2006-09-20)
      The link between natural ion-line enhancements in radar spectra and auroral activity has been the subject of recent studies but conclusions have been limited by the spatial and temporal resolution previously available. The next challenge is to use shorter sub-second integration times in combination with interferometric programmes to resolve spatial structure within the main radar beam, and so ...
    • Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency 

      Brekke, Asgeir; Blagoveshchenskaya, N. F.; Carlson, H. C.; Kornienko, V. A.; Borisova, T. D.; Rietveld, M. T.; Yeoman, T. K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009-01-08)
      Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency fH was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency ...
    • Photonic-chip assisted correlative light and electron microscopy 

      Tinguely, Jean-Claude; Steyer, Anna Maria; Øie, Cristina Ionica; Helle, Øystein Ivar; Dullo, Firehun Tsige; Olsen, Randi; McCourt, Peter; Schwab, Yannick; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)
      Correlative light and electron microscopy (CLEM) unifies the versatility of light microscopy (LM) with the high resolution of electron microscopy (EM), allowing one to zoom into the complex organization of cells. Here, we introduce photonic chip assisted CLEM, enabling multi-modal total internal reflection fluorescence (TIRF) microscopy over large field of view and high precision localization of the ...
    • Photonic-chip based free space beam shaping and steering for advanced optical microscopy application 

      Lahrberg, Marcel; Dullo, Firehun Tsige; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-12)
      Photonic-chip-based light illumination has recently found applications in optical microscopy and nanoscopy methodologies. The photonic chip removes the dependency on imaging objective lenses to generate the required illumination patterns for different microscopy methods. Until now, all the reported chip-based optical microscopy methods exploit the evanescent field present on top of a waveguide surface ...
    • Photonic-chip: a multimodal imaging tool for histopathology 

      Villegas, Luis; Dubey, Vishesh Kumar; Tinguely, Jean-Claude; Coucheron, David Andre; Priyadarshi, Anish; Acuña Maldonado, Sebastian Andres; Agarwal, Krishna; Mateos, Jose M; Nystad, Mona; Hovd, Aud-Malin Karlsson; Fenton, Kristin Andreassen; Ahluwalia, Balpreet Singh (Conference object; Konferansebidrag, 2021-04)
      We propose the photonic-chip as a multimodal imaging platform for histopathological assessment, allowing large fields-of-view across diverse microscopy methods including total internal reflection fluorescence and single-molecule localization.
    • Physical and statistical based decomposition of Polarimetric Synthetic Aperture Radar images of Arctic Sea ice 

      Arienzo, Alberto (Master thesis; Mastergradsoppgave, 2015-06-01)
      The studies about the climatic changes have always more underlined the importance of the climatic balance of the Arctic regions. For this reason the need of monitoring the Arctic becomes always more urgent. To measure the sea ice thickness, the sea ice cover, the motion of the glaciers and to discriminate the various kind of ice are only several of the challenges about the Arctic monitoring. But the ...
    • Physics-based machine learning for subcellular segmentation in living cells 

      Sekh, Arif Ahmed; Opstad, Ida Sundvor; Godtliebsen, Gustav; Birgisdottir, Åsa Birna; Ahluwalia, Balpreet Singh; Agarwal, Krishna; Prasad, Dilip K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-15)
      Segmenting subcellular structures in living cells from fluorescence microscope images is a ground truth (GT)-deficient problem. The microscopes’ three-dimensional blurring function, finite optical resolution due to light diffraction, finite pixel resolution and the complex morphological manifestations of the structures all contribute to GT-hardness. Unsupervised segmentation approaches are quite ...
    • Planetary auroral imaging 

      Nagoshi, Yoshiaki (Mastergradsoppgave; Master thesis, 2021-07-09)
      The interaction of the solar wind and the Earth magnetosphere cause auroras. The energetic electrically charged particles, mostly electrons, accelerate along the Earth magnetic field lines into the upper atmosphere, where they collide with gas atoms, causing them to emit light. Some planets also have auroral emission in their characteristic environment. The Jovian magnetosphere is the largest ...
    • Planetary radar science case for EISCAT 3D 

      Tveito, Torbjørn; Vierinen, Juha; Gustavsson, Björn Johan; Narayanan, Viswanathan Lakshmi (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-12)
      Ground-based inverse synthetic aperture radar is a tool that can provide insights into the early history and formative processes of planetary bodies in the inner solar system. This information is gathered by measuring the scattering matrix of the target body, providing composite information about the physical structure and chemical makeup of its surface and subsurface down to the penetration ...
    • Plasma cloud detection and diagnostics from arcing by conditional averaging 

      Nilsen, Kenneth (Master thesis; Mastergradsoppgave, 2017-06-06)
      Plasma cloud formation from arcing is experimentally studied. The arcs are formed by a high voltage set-up in the space simulation chamber at UiT. The plasma clouds are observed as large structures in the time series recorded by Langmuir probe and reference probe. By using the method of conditional averaging, the structures are accentuated. The electron cloud formed by arcing was found to be ...
    • Plasma density over Svalbard during the ISBJØRN campaign. 

      Hall, Chris; Van Eyken, A.P.; Svenes, K.R. (Journal article; Peer reviewed; Tidsskriftartikkel, 2000)
      In 1997, reliable operation of the EISCAT Svalbard Radar (ESR) was achieved and a rocket launching facility at Ny Ålesund on Svalbard (79°N, 12°E) (SVALRAK) was established. On 20 November, 1977, the first instrumented payload was launched from SVALRAK. Although the payload configuration had been flown many times previously from Andøya Rocket Range on the Norwegian mainland, this presented an ...
    • Plasma fluctuations in the scrape-off layer and at the divertor target in Alcator C-Mod and their relationship to divertor collisionality and density shoulder formation 

      Kuang, AQ; LaBombard, Brian; Brunner, D; Garcia, Odd Erik; Kube, Ralph; Theodorsen, Audun (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-15)
      Experiments indicate that the formation of density shoulders in the far scrape-off layer (SOL) is associated with an increase in cross-field transport and the propagation of coherent structures of high density known as blobs. It has been suggested that far SOL divertor collisionality (Λ<sub>div</sub>) may be a controlling parameter in this physics, which could be challenging for heat flux mitigation ...