Viser treff 508-527 av 942

    • Models for electrostatic drift waves with density variations along magnetic field lines 

      Garcia, Odd Erik; Pecseli, Hans (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Drift waves with vertical magnetic fields in gravitational ionospheres are considered where the unperturbed plasma density is enhanced in a magnetic flux tube. The gravitational field gives rise to an overall decrease of plasma density for increasing altitude. Simple models predict that drift waves with finite vertical wave vector components can increase in amplitude merely due to a conservation of ...
    • Modification of the high-latitude ionospheric F region by high-power HF radio waves at frequencies near the fifth and sixth electron gyroharmonics 

      Borisova, Tatiana D.; Blagoveshchenskaya, Nataly F.; Kalishin, Aleksei S.; Rietveld, Michael T.; Yeoman, Timothy Kenneth; Hägström, I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-01)
      We study the modification effects of the high-latitude ionospheric F region induced by a highpower O-mode HF radio wave injected towards the magnetic zenith, at frequencies near the fifth and sixth electron gyroharmonics using the EISCAT/Heating facility. Multi-instrument diagnostics with the EISCAT incoherent scatter radar (930 MHz) at Tromsø, Norway, the CUTLASS coherent radar at Hankasalmi, ...
    • Modulation of polar mesospheric summer echoes (PMSEs) with high-frequency heating during low solar illumination 

      Gunnarsdottir, Tinna; Mann, Ingrid; Poggenpohl, Arne Hendrik; Mahmoudian, Alireza; Dalin, Peter; Rietveld, Michael T.; Haeggstroem, Ingemar (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-14)
      Polar mesospheric summer echo (PMSE) formation is linked to charged dust/ice particles in the mesosphere. We investigate the modulation of PMSEs with radio waves based on measurements with EISCAT VHF radar and EISCAT heating facility during low solar illumination. The measurements were made in August 2018 and 2020 around 20:02 UT. Heating was operated in cycles with intervals of 48 s on and 168 ...
    • Monitoring a changing Arctic: Recent advancements in the study of sea ice microbial communities 

      Matero, Ilkka; Bellas, Christopher; Turpin-Jelfs, Thomas; Anhaus, Philipp; Graeve, Martin; Fripiat, Francois; Tranter, Martyn; Landy, Jack Christopher; Sanchez-Baracaldo, Patricia; Leu, Eva; Katlein, Christian; Mundy, C.J.; Rysgaard, Søren; Tedesco, Letizia; Haas, Christian; Nicolaus, Marcel (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-25)
      Sea ice continues to decline across many regions of the Arctic, with remaining ice becoming increasingly younger and more dynamic. These changes alter the habitats of microbial life that live within the sea ice, which support healthy functioning of the marine ecosystem and provision of resources for human-consumption, in addition to influencing biogeochemical cycles (e.g. air–sea CO2 exchange). With ...
    • Monitoring glacier changes using multitemporal multipolarization SAR images 

      Akbari, Vahid; Doulgeris, Anthony Paul; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • Monthly mean climatology of the prevailing winds and tides in the Arctic mesosphere/lower thermosphere. 

      Hall, Chris; Portnyagin, Y.I.; Solovjova, T.V.; Makarov, N.A.; Merzlyakov, E.G.; Manson, A.H.; Meek, C.E.; Hocking, W.; Pancheva, D.; Hoffmann, P.; Singer, W.; Murayama, Y.; Igarashi, K.; Forbes, J.M.; Palo, S.; Nozawa, S.; Mitchell, N. (Journal article; Peer reviewed; Tidsskriftartikkel, 2004-11-03)
      The Arctic MLT wind regime parameters measured at the ground-based network of MF and meteor radar stations (Andenes 69° N, Tromsø 70° N, Esrange 68° N, Dixon 73.5° N, Poker Flat 65° N and Resolute Bay 75° N) are discussed and compared with those observed in the mid-latitudes. The network of the ground-based MF and meteor radars for measuring winds in the Arctic upper mesosphere and lower thermosphere ...
    • Moon Imaging Technique and Experiments Based on Sanya Incoherent Scatter Radar 

      Li, Mingyuan; Yue, Xinan; Wang, Yonghui; Wang, Junyi; Ding, Feng; Vierinen, Juha; Zhang, Ning; Wang, Zhongqiu; Ning, Baiqi; Zhao, Biqiang; Zeng, Lingqi (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-13)
      This article introduces the experiment design for Moon imaging based on Sanya incoherent scatter radar (SYISR) and algorithm research in data processing. The peak power of SYISR is 2 MW. The transmitted frequency used for Moon imaging experiments is 430 MHz. We conducted Moon imaging experiments using two types of waveforms, 13-bit Barker code, and linear frequency modulation (LFM) chirp. Considering ...
    • MOSIDEO/CIRFA Tank Experiments on Behavior and Detection of Oil in Ice 

      Petrich, Christian; O'Sadnick, Megan Eileen; Brekke, Camilla; Myrnes, Marianne; Maus, Sønke; Salomon, Martina Lan; Woelk, Sofie; Grydeland, Tom; Jenssen, Rolf-Ole Rydeng; Eicken, Hajo; Oggier, Marc; Ferro-Famil, Laurent; Harkati, Lekhmissi; Rebane, Ott; Reimer, Nils (Conference object; Konferansebidrag, 2019-06)
      In the Arctic, presence of sea ice presents a challenge to safe and sustainable operations. To optimize planning and minimize impact of inadvertent oil spills, oil-in-ice experiments were performed at the HSVA Arctic Environmental Test Basin (AETB) from 14 March to 4 April 2017. Following an under-ice spill and simulated springtime warming, the microscopic movement and distribution of oil in the sea ...
    • Muliggjørende teknologi og rammebetingelser 

      Sæle, Hanne; Grande, Ove Steinar; Ingebrigtsen, Karoline; Ahcin, Peter (Research report; Forskningsrapport, 2018-02-19)
    • Multi-color imaging of sub-mitochondrial structures in living cells using structured illumination microscopy 

      Opstad, Ida Sundvor; Wolfson, Deanna; Øie, Cristina Ionica; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-18)
      The dimensions of mitochondria are close to the diffraction limit of conventional light microscopy techniques, making the complex internal structures of mitochondria unresolvable. In recent years, new fluorescence-based optical imaging techniques have emerged, which allow for optical imaging below the conventional limit, enabling super-resolution (SR). Possibly the most promising SR and diffraction-limited ...
    • Multi-frequency polarimetric SAR signatures of lead sea ice and oil spills 

      Johansson, Malin; Brekke, Camilla; Spreen, Gunnar (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)
      Synthetic aperture radar is used to identify and monitor oil spills. Separation from oil spill look-alikes is an important part of a fully automatic oil spill detection scheme. Here we investigate the polarimetric signatures for oil spills and newly formed sea ice (a well-known look-alike) in fully polarimetric Radarsat-2 satellite scenes. Using the fully polarimetric scenes we calculate four different ...
    • Multi-instrument observations of a large scale Pc4 pulsation 

      Behlke, Rico; Clausen, L. B. N.; Yeoman, T. K.; Lucek, E. A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2008)
    • Multi-instrument observations of the Pajala fireball: origin, characteristics, and atmospheric implications 

      Vierinen, Juha; Aslaksen, Torstein; Chau, Jorge L.; Gritsevich, Maria; Gustavsson, Bjorn Johan; Kastinen, Daniel; Kero, Johan; Kozlovsky, Alexandre; Kværna, Tormod; Näsholm, Sven Peter; Ulich, Thomas; Vegum, Ketil; Midtskogen, Steinar; Lester, Mark (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-07)
      Meteor observations provide information about Solar System constituents and their influx onto Earth, their interaction processes in the atmosphere, as well as the neutral dynamics of the upper atmosphere. This study presents optical, radar, and infrasound measurements of a daytime fireball that occurred on 4 December 2020 at 13:30 UTC over Northeast Sweden. The fireball was recorded with two video ...
    • Multi-mission remote sensing of low concentration produced water slicks 

      Johansson, Malin; Skrunes, Stine; Brekke, Camilla; Isaksen, Hugo (Journal article; Tidsskriftartikkel, 2021-04)
      Produced water is legally released from oil platforms and often detected by oil spill detection services despite their low oil concentrations. Using fully-polarimetric RADARSAT-2 and dual-polarimetric Sentinel-1 data we investigate their synthetic aperture radar (SAR) characteristics. Detectability ranges within the SAR and optical Sentinel-2 and PlanetScope images are assessed and compared to in-situ ...
    • Multi-modal chip-based fluorescence and quantitative phase microscopy for studying inflammation in macrophages 

      Dubey, Vishesh; Ahmad, Azeem; Singh, Rajwinder; Wolfson, Deanna; Basnet, Purusotam; Acharya, Ganesh; Mehta, Dalip Singh; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-24)
      Total internal reflection fluorescence (TIRF) microscopy benefits from high-sensitivity, low background noise, low photo-toxicity and high-contrast imaging of sub-cellular structures close to the membrane surface. Although, TIRF microscopy provides high-contrast imaging it does not provide quantitative information about morphological features of the biological cells. Here, we propose an integrated ...
    • Multi-moded high-index contrast optical waveguide for super-contrast high-resolution label-free microscopy 

      Jayakumar, Nikhil; Dullo, Firehun Tsige; Dubey, Vishesh Kumar; Ahmad, Azeem; Ströhl, Florian; Cauzzo, Jennifer; Mazagao Guerreiro, Eduarda; Snir, Omri; Skalko-Basnet, Natasa; Agarwal, Krishna; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-20)
      The article elucidates the physical mechanism behind the generation of superior-contrast and highresolution label-free images using an optical waveguide. Imaging is realized by employing a high index contrast multi-moded waveguide as a partially coherent light source. The modes provide near-field illumination of unlabeled samples, thereby repositioning the higher spatial frequencies of the ...
    • Multi-radar observations of polar mesosphere summer echoes during the PHOCUS campaign on 20-22 July 2011 

      Belova, Evgenia; Kirkwood, Sheila; Latteck, Ralph; Zecha, Marius; Pinedo Nava, Henry; Hedin, Jonas; Gumbel, Jörg (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-06-27)
      During the PHOCUS rocket campaign, on 20-22 July 2011, the observations of polar mesosphere summer echoes (PMSE) were made by three mesosphere-stratosphere-troposphere radars, operating at about 50 MHz. One radar, ESRAD is located at Esrange in Sweden, where the rocket was launched, two other radars, MAARSY and MORRO, are located 250 km north-west and 200 km north of ESRAD, respectively, on the other ...
    • Multi-scale measurements of mesospheric aerosols and electrons during the MAXIDUSTY campaign 

      Antonsen, Tarjei; Havnes, Ove; Spicher, Andres (Journal article; Peer reviewed, 2019-04-08)
      We present in situ measurements of small-scale fluctuations in aerosol populations as recorded through a mesospheric cloud system from the Faraday cups DUSTY and MUDD during on the MAXIDUSTY-1 and 1B sounding rocket payloads launched in the summer of 2016. <br>Two mechanically identical DUSTY probes mounted with an inter-spacing of ∼10 cm recorded very different currents, with strong spin modulation, ...
    • Multi-static spatial and angular studies of polar mesospheric summer echoes combining MAARSY and KAIRA 

      Chau, Jorge L.; McKay, Derek; Vierinen, Juha; La Hoz, Cesar Augusto Vergara; Ulich, Thomas; Lehtinen, Markku; Latteck, Ralph (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-06)
      Polar mesospheric summer echoes (PMSEs) have been long associated with noctilucent clouds (NLCs). For large ice particles sizes and relatively high ice densities, PMSEs at 3m Bragg wavelengths are known to be good tracers of the atmospheric wind dynamics and to be highly correlated with NLC occurrence. Combining the Middle Atmosphere ALOMAR Radar System (MAARSY) and the Kilpisjärvi Atmospheric Imaging ...
    • Multi-View Self-Constructing Graph Convolutional Networks With Adaptive Class Weighting Loss for Semantic Segmentation 

      Liu, Qinghui; Kampffmeyer, Michael; Jenssen, Robert; Salberg, Arnt Børre (Conference object; Konferansebidrag, 2020-07-28)
      We propose a novel architecture called the Multi-view Self-Constructing Graph Convolutional Networks (MSCG-Net) for semantic segmentation. Building on the recently proposed Self-Constructing Graph (SCG) module, which makes use of learnable latent variables to self-construct the underlying graphs directly from the input features without relying on manually built prior knowledge graphs, we leverage ...