Viser treff 241-260 av 947

    • Towards robust partially supervised multi-structure medical image segmentation on small-scale data 

      Dong, Nanqing; Kampffmeyer, Michael; Liang, Xiaodan; Xu, Min; Voiculescu, Irina; Xing, Eric (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-20)
      The data-driven nature of deep learning (DL) models for semantic segmentation requires a large number of pixel-level annotations. However, large-scale and fully labeled medical datasets are often unavailable for practical tasks. Recently, partially supervised methods have been proposed to utilize images with incomplete labels in the medical domain. To bridge the methodological gaps in ...
    • Frequency spectra of horizontal winds in the mesosphere and lower thermosphere region from multistatic specular meteor radar observations during the SIMONe 2018 campaign 

      Charuvil, Harikrishnan; Chau, Jorge L.; Marino, Raffaele; Vierinen, Juha; Vargas, Fabio; Urco, Juan M.; Clahsen, Matthias; Jacobi, Christoph (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-11)
      In recent years, multistatic specular meteor radars (SMRs) have been introduced to study the Mesosphere and Lower Thermosphere (MLT) dynamics with increasing spatial and temporal resolution. SMRs, compared to other groundbased observations, have the advantage of continuously measuring the region between 80 and 100 km independent of weather, season, or time of day. In this paper, frequency spectra ...
    • 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 ...
    • Effects of particle precipitation on the polar mesospheric summer echoes observed by EISCAT VHF 224 MHz radar 

      Viswanathan, Lakshmi Narayanan; Häggström, Ingemar; Mann, Ingrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-23)
      We present the results from investigation of spectra of polar mesospheric summer echoes (PMSE) observed with EISCAT VHF 224 MHz radar during energetic particle precipitation events in the summer of 2019. We used the sudden enhancements in electron densities derived from the VHF observations above 90 km as indicators of particle precipitation. We find that the altitude extent of the PMSE increased ...
    • A Stimulated Emission Diagnostic Technique for Electron Temperature of the High Power Radio Wave Modified Ionosphere 

      Fu, Haiyang; Jiang, M. L.; Vierinen, Juha; Häggström, Ingemar; Rietveld, Michael T.; Varberg, Erik; Sato, Hiroatsu; Wu, Jiang; Scales, Wayne A.; Jin, Y. Q. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-09)
      We report observations of stimulated electromagnetic emission (SEE) induced by high power high frequency (HF) radio waves near the third electron gyroharmonic (3urn:x-wiley:00948276:media:grl64672:grl64672-math-0022) at European Incoherent Scatter Radar (EISCAT). It is discovered that stimulated Brillouin scattering (SBS) spectrum behaves similarly as spectral ion lines of the incoherent scatter ...
    • A 30-year probability map for oil spill trajectories in the barents sea to assess potential environmental and socio-economic threats 

      Pavlov, Victor; Martins de Aguiar, Victor Cesar; Hole, Lars Robert; Pongrácz, Eva (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-24)
      Increasing exploration and exploitation activity in the Arctic Ocean has intensified maritime traffic in the Barents Sea. Due to the sparse population and insufficient oil spill response infrastructure on the extensive Barents Sea shoreline, it is necessary to address the possibility of offshore accidents and study hazards to the local environment and its resources. Simulations of surface oil ...
    • Unbalanced low coherence interference microscopy 

      Ahmad, Azeem; Habib, Anowarul; Dubey, Vishesh Kumar; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-03)
      Low coherence interference microscopy (LCIM) provides high spatial phase sensitivity, i.e., speckle free and coherent noise free quantitative phase images of the test specimens. Due to low temporal coherence (TC) length of the light source, LCIM requires precise adjustment of the optical path difference (OPD) between the object and the reference arm, which is only a few micrometers. Consequently, ...
    • Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China-a Pan-Eurasian Experiment (PEEX) programme perspective 

      Lappalainen, Hanna K.; Petäjä, Tuukka; Vihma, Timo Pekka; Räisänen, Jouni; Baklanov, Alexander; Chalov, Sergey; Esau, Igor; Ezhova, Ekaterina; Leppäranta, Matti; Pozdnyakov, Dmitry; Pumpanen, Jukka; Andreae, Meinrat O.; Arshinov, Mikhail; Asmi, Eija; Bai, Jianhui; Bashmachnikov, Igor; Belan, Boris; Bianchi, Federico; Biskaborn, Boris; Boy, Michael; Bäck, Jaana; Cheng, Bin; Chubarova, Natalia; Duplissy, Jonathan; Dyukarev, Egor; Eleftheriadis, Konstantinos; Forsius, Martin; Heimann, Martin; Juhola, Sirkku; Konovalov, Vladimir; Konovalov, Igor; Konstantinov, Pavel; Köster, Kajar; Lapshina, Elena; Lintunen, Anna; Mahura, Alexander; Makkonen, Risto; Malkhazova, Svetlana; Mammarella, Ivan; Mammola, Stefano; Mazon, Stephany Buenrostro; Meinander, Outi; Mikhailov, Eugene; Miles, Victoria; Myslenkov, Stanislav; Orlov, Dmitry; Paris, Jean-Daniel; Pirazzini, Roberta; Popovicheva, Olga; Pulliainen, Jouni; Rautiainen, Kimmo; Sachs, Torsten; Shevchenko, Vladimir; Skorokhod, Andrey; Stohl, Andreas; Suhonen, Elli; Thomson, Erik S.; Tsidilina, Marina; Tynkkynen, Veli-Pekka; Uotila, Petteri; Virkkula, Aki; Voropay, Nadezhda; Wolf, Tobias; Yasunaka, Sayaka; Zhang, Jiahua; Qiu, Yubao; Ding, Aijun; Guo, Huadong; Bondur, Valery; Kasimov, Nikolay; Zilitinkevich, Sergej; Kerminen, Veli-Matti; Kulmala, Markku (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-06)
      The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical ...
    • Rechargeable Iron-Ion Battery Using a Pure Ionic Liquid Electrolyte 

      Zhao, Yansong; Zhen, Yingpeng; Boström, Tobias Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-07)
      A rechargeable iron-ion battery (Fe-ion battery) has been fabricated in our laboratory using a pure ionic liquid electrolyte. Magnetic ionic liquids of 1-butyl-3-methylimidazolium tetrachloroferrate (BmimFeCl<sub>4</sub>) and 1-methyl-3-octylimidazolium tetrachloroferrate (OmimFeCl<sub>4</sub>) are synthesized and utilized as electrolytes in this work. The chemical structure of the two ionic ...
    • Three-dimensional structured illumination microscopy data of mitochondria and lysosomes in cardiomyoblasts under normal and galactose-adapted conditions 

      Opstad, Ida Sundvor; Godtliebsen, Gustav; Ströhl, Florian; Myrmel, Truls; Ahluwalia, Balpreet Singh; Agarwal, Krishna; Birgisdottir, Åsa birna (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-23)
      This three-dimensional structured illumination microscopy (3DSIM) dataset was generated to highlight the suitability of 3DSIM to investigate mitochondria-derived vesicles (MDVs) in H9c2 cardiomyoblasts in living or fxed cells. MDVs act as a mitochondria quality control mechanism. The cells were stably expressing the tandem-tag eGFP-mCherry-OMP25-TM (outer mitochondrial membrane) which can be used ...
    • Mixing up contrastive learning: Self-supervised representation learning for time series 

      Wickstrøm, Kristoffer; Kampffmeyer, Michael; Mikalsen, Karl Øyvind; Jenssen, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-14)
      The lack of labeled data is a key challenge for learning useful representation from time series data. However, an unsupervised representation framework that is capable of producing high quality representations could be of great value. It is key to enabling transfer learning, which is especially beneficial for medical applications, where there is an abundance of data but labeling is costly and time ...
    • Machine Learning Detection of Dust Impact Signals Observed by The Solar Orbiter 

      Kvammen, Andreas; Wickstrøm, Kristoffer; Kociscak, Samuel; Vaverka, Jakub; Nouzak, Libor; Zaslavsky, Arnaud; Rackovic Babic, Kristina; Gjelsvik, Amalie; Pisa, David; Souček, Jan; Mann, Ingrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-11)
      This article present results from automatic detection of dust impact signals observed by the Solar Orbiter – Radio and Plasma Waves instrument.<p> <p>A sharp and characteristic electric field signal is observed by the Radio and Plasma Waves instrument when a dust particle impact the spacecraft at high velocity. In this way, ∼5–20 dust impacts are daily detected as the Solar Orbiter travels through ...
    • Deep microlocal reconstruction for limited-angle tomography 

      Andrade-Loarca, Héctor; Kutyniok, Gitta Astrid Hildegard; Öktem, Ozan; Petersen, Philipp (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-04)
      We present a deep-learning-based algorithm to jointly solve a reconstruction problem and a wavefront set extraction problem in tomographic imaging. The algorithm is based on a recently developed digital wavefront set extractor as well as the well-known microlocal canonical relation for the Radon transform. We use the wavefront set information about x-ray data to improve the reconstruction ...
    • Formation of ice particles through nucleation in the mesosphere 

      Tanaka, Kyoko; Mann, Ingrid; Kimura, Yuki (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-28)
      Observations of polar mesospheric clouds have revealed the presence of solid ice particles in the upper mesosphere at high latitudes; however, their formation mechanism remains uncertain. In this study, we investigated the formation process of ice particles through nucleation from small amounts of water vapor at low temperatures. Previous studies that used classical nucleation theory have shown ...
    • Report From Surveys To Assess Harp And Hooded Seal Pup Production In The Greenland Sea Pack-Ice In 2022 

      Biuw, Martin; Nilssen, Kjell Tormod; Kristiansen, Martin; Lindblom, Lotta; Poltermann, Michael Tino; Haug, Tore; Johansson, Malin (Research report; Forskningsrapport, 2022-06-07)
      Cruise no.: 2022703 : The 2022 survey of harp and hooded seal pup production in the Greenland Sea was carried out to obtain updated estimates to be used to assess current status of these two seal stocks. Since a similar survey in 2018 indicated a 40% reduction in harp seal pup production since the 2012 survey, and the continued lack of increase in pup production of the severely depleted hooded ...
    • Thermodynamic and dynamic contributions to seasonal Arctic sea ice thickness distributions from airborne observations 

      von Albeldyll, Luisa; Hendricks, Stefan; Grodofzig, Raphael; Krumpen, Thomas; Arndt, Stefanie; Belter, H. Jakob; Birnbaum, Gerit; Cheng, Bin; Hoppmann, Mario; Hutchings, Jennifer; Itkin, Polona; Lei, Ruibo; Nicolaus, Marcel; Ricker, Robert; Rohde, Jan; Suhrhoff, Mira; Timofeeva, Anna; Watkins, Daniel; Webster, Melinda; Haas, Christian (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-18)
      Sea ice thickness is a key parameter in the polar climate and ecosystem. Thermodynamic and dynamic processes alter the sea ice thickness.The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition provided a unique opportunity to study seasonal sea ice thickness changes of the same sea ice. We analyzed 11 large-scale (*50 km) airborne electromagnetic sea thickness ...
    • Validation of Multistatic Meteor Radar Analysis Using Modeled Mesospheric Dynamics: An Assessment of the Reliability of Gradients and Vertical Velocities 

      Charuvil Asokan, Harikrishnan; Chau, Jorge L.; Larsen, Miguel F.; Conte, J. Federico; Marino, Raffaele; Vierinen, Juha; Baumgarten, Gerd; Borchert, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-28)
      A virtual meteor radar system based on the upper-atmosphere extension of the high-resolution ICOsahedral Non-hydrostatic general circulation model is constructed to validate multistatic specular meteor radar (SMR) analyses. The virtual radar system examines the validity of mean winds and gradients estimation techniques used in multistatic SMRs. The study is motivated by unexpected mean values and ...
    • 2022 Tonga Volcanic Eruption Induced Global Propagation of Ionospheric Disturbances via Lamb Waves 

      Zhang, Shun-Rong; Vierinen, Juha; Aa, Ercha; Goncharenko, Larisa P.; Erickson, Philip J.; Rideout, William; Coster, Anthea J.; Spicher, Andres (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-23)
      The Tonga volcano eruption at 04:14:45 UT on 2022-01-15 released enormous amounts of energy into the atmosphere, triggering very significant geophysical variations not only in the immediate proximity of the epicenter but also globally across the whole atmosphere. This study provides a global picture of ionospheric disturbances over an extended period for at least 4 days. We find traveling ionospheric ...
    • ICEBEAR-3D: A Low Elevation Imaging Radar Using a Non-Uniform Coplanar Receiver Array for E Region Observations 

      Lozinsky, Adam; Hussey, Glenn; McWilliams, Kathryn; Huyghebaert, Devin Ray; Galeschuk, Draven (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-19)
      The Ionospheric Continuous-wave E region Bistatic Experimental Auroral Radar (ICEBEAR) has been reconfigured using a phase error minimization and stochastic antenna location perturbation technique. The resulting 45-baseline sparse non-uniform coplanar T-shaped array, ICEBEAR-3D, is used for aperture synthesis radar imaging of low elevation targets. The reconfigured receiver antenna array now has ...
    • Finite element simulation of transmission and reflection of acoustic waves in the ultrasonic transducer 

      Shukla, Kaushik; Ahmad, Azeem; Ahluwalia, Balpreet Singh; Melandsø, Frank; Habib, Anowarul (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-30)
      In scanning acoustic microscopy (SAM), the image quality depends on several factors such as noise level, resolution, and interaction of the waves with sample boundaries. The theoretical equations for the reflection coefficient and transmission coefficient are suitable for plane boundaries but fail for curved/rough boundaries. We presented a finite element method-based modeling for the loss ...