1,299 results on '"Duscha A"'
Search Results
2. Observing atmospheric convection with dual-scanning lidars
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C. Duscha, J. Pálenik, T. Spengler, and J. Reuder
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Environmental engineering ,TA170-171 ,Earthwork. Foundations ,TA715-787 - Abstract
While convection is a key process in the development of the atmospheric boundary layer, conventional meteorological measurement approaches fall short in capturing the evolution of the complex dynamics of convection. To obtain deeper observational insight into convection, we assess the potential of a dual-lidar approach. We present the capability of two pre-processing procedures, an advanced clustering filter instead of a simple threshold filter and a temporal interpolation, to increase data availability and reduce errors in the individual lidar observations that would be amplified in the dual-lidar retrieval. To evaluate the optimal balance between spatial and temporal resolution to sufficiently resolve convective properties, we test a set of scan configurations. We deployed the dual-lidar setup at two Norwegian airfields in a different geographic setting and demonstrate its capabilities as a proof of concept. We present a retrieval of the convective flow field in a vertical plane above the airfield for each of these setups. The advanced data filtering and temporal interpolation approaches show an improving effect on the data availability and quality and are applied to the observations used in the dual-lidar retrieval. All tested angular resolutions captured the relevant spatial features of the convective flow field, and balance between resolutions can be shifted towards a higher temporal resolution. Based on the evaluated cases, we show that the dual-lidar approach sufficiently resolves and provides valuable insight into the dynamic properties of atmospheric convection.
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- 2023
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3. Evaluating the Performance of Pulsed and Continuous-Wave Lidar Wind Profilers with a Controlled Motion Experiment
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Shokoufeh Malekmohammadi, Christiane Duscha, Alastair D. Jenkins, Felix Kelberlau, Julia Gottschall, and Joachim Reuder
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floating lidar system ,ship-based lidar ,motion-induced error ,motion compensation ,motion correction ,Science - Abstract
While floating wind lidars provide reliable and cost-effective measurements, these measurements may be inaccurate due to the motion of the installation platforms. Prior studies have not distinguished between systematic errors associated with lidars and errors resulting from motion. This study will fill this gap by examining the impact of platform motion on two types of profiling wind lidar systems: the pulsed WindCube V1 (Leosphere) and the continuous-wave ZephIR 300 (Natural Power). On a moving hexapod platform, both systems were subjected to 50 controlled sinusoidal motion cases in different degrees of freedom. Two reference lidars were placed at a distance of five meters from the platform as reference lidars. Motion-induced errors in mean wind speed and turbulence intensity estimation by lidars are analyzed. Additionally, the effectiveness of a motion correction approach in reducing these errors across various scenarios is evaluated. The results indicate that presence of rotational motion leads to higher turbulence intensity (TI) estimation by moving lidars. The absolute percentage error between lidars is the highest when lidars are exposed to yaw and heave motion and is the lowest when exposed to surge motion. The correlation between lidars, though it is the lowest in the presence of pitch, yaw, and heave motion. Furthermore, applying motion compensation can compensate the correlation drop and erroneous TI estimation.
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- 2024
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4. Sub-arcsecond imaging with the International LOFAR Telescope I. Foundational calibration strategy and pipeline
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Morabito, L. K., Jackson, N. J., Mooney, S., Sweijen, F., Badole, S., Kukreti, P., Venkattu, D., Groeneveld, C., Kappes, A., Bonnassieux, E., Drabent, A., Iacobelli, M., Croston, J. H., Best, P. N., Bondi, M., Callingham, J. R., Conway, J. E., Deller, A. T., Hardcastle, M. J., McKean, J. P., Miley, G. K., Moldon, J., Röttgering, H. J. A., Tasse, C., Shimwell, T. W., van Weeren, R. J., Anderson, J. M., Asgekar, A., Avruch, I. M., van Bemmel, I. M., Bentum, M. J., Bonafede, A., Brouw, W. N., Butcher, H. R., Ciardi, B., Corstanje, A., Coolen, A., Damstra, S., de Gasperin, F., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Garrett, M. A., Griessmeier, J., Gunst, A. W., van Haarlem, M. P., Hoeft, M., van der Horst, A. J., Jütte, E., Kadler, M., Koopmans, L. V. E., Krankowski, A., Mann, G., Nelles, A., Oonk, J. B. R., Orru, E., Paas, H., Pandey, V. N., Pizzo, R. F., Pandey-Pommier, M., Reich, W., Rothkaehl, H., Ruiter, M., Schwarz, D. J., Shulevski, A., Soida, M., Tagger, M., Vocks, C., Wijers, R. A. M. J., Wijnholds, S. J., Wucknitz, O., Zarka, P., and Zucca, P.
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Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
[abridged] The International LOFAR Telescope is an interferometer with stations spread across Europe. With baselines of up to ~2,000 km, LOFAR has the unique capability of achieving sub-arcsecond resolution at frequencies below 200 MHz, although this is technically and logistically challenging. Here we present a calibration strategy that builds on previous high-resolution work with LOFAR. We give an overview of the calibration strategy and discuss the special challenges inherent to enacting high-resolution imaging with LOFAR, and describe the pipeline, which is publicly available, in detail. We demonstrate the calibration strategy by using the pipeline on P205+55, a typical LOFAR Two-metre Sky Survey (LoTSS) pointing. We perform in-field delay calibration, solution referencing to other calibrators, self-calibration, and imaging of example directions of interest in the field. For this specific field and these ionospheric conditions, dispersive delay solutions can be transferred between calibrators up to ~1.5 degrees away, while phase solution transferral works well over 1 degree. We demonstrate a check of the astrometry and flux density scale. Imaging in 17 directions, the restoring beam is typically 0.3" x 0.2" although this varies slightly over the entire 5 square degree field of view. We achieve ~80 to 300 $\mu$Jy/bm image rms noise, which is dependent on the distance from the phase centre; typical values are ~90 $\mu$Jy/bm for the 8 hour observation with 48 MHz of bandwidth. Seventy percent of processed sources are detected, and from this we estimate that we should be able to image ~900 sources per LoTSS pointing. This equates to ~3 million sources in the northern sky, which LoTSS will entirely cover in the next several years. Future optimisation of the calibration strategy for efficient post-processing of LoTSS at high resolution (LoTSS-HR) makes this estimate a lower limit., Comment: Accepted to a special issue of A&A on sub-arcsecond imaging with LOFAR. 24 pages, 16 figures
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- 2021
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5. Sub-arcsecond imaging with the International LOFAR Telescope: II. Completion of the LOFAR Long-Baseline Calibrator Survey
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Jackson, Neal, Badole, Shruti, Morgan, John, Chhetri, Rajan, Prusis, Kaspars, Nikolajevs, Atvars, Morabito, Leah, Brentjens, Michiel, Sweijen, Frits, Iacobelli, Marco, Orrù, Emanuela, Sluman, J., Blaauw, R., Mulder, H., van Dijk, P., Mooney, Sean, Deller, Adam, Moldon, Javier, Callingham, J. R., Harwood, Jeremy, Hardcastle, Martin, Heald, George, Drabent, Alexander, McKean, J. P., Asgekar, A., Avruch, I. M., Bentum, M. J., Bonafede, A., Brouw, W. N., Brüggen, M., Butcher, H. R., Ciardi, B., Coolen, A., Corstanje, A., Damstra, S., Duscha, S., Eislöffel, J., Falcke, H., Garrett, M., de Gasperin, F., Griessmeier, J. -M., Gunst, A. W., van Haarlem, M. P., Hoeft, M., van der Horst, A. J., Jütte, E., Koopmans, L. V. E., Krankowski, A., Maat, P., Mann, G., Miley, G. K., Nelles, A., Norden, M., Paas, M., Pandey, V. N., Pandey-Pommier, M., Pizzo, R. F., Reich, W., Rothkaehl, H., Rowlinson, A., Ruiter, M., Shulevski, A., Schwarz, D. J., Smirnov, O., Tagger, M., Vocks, C., van Weeren, R. J., Wijers, R., Wucknitz, O., Zarka, P., Zensus, J. A., and Zucca, P.
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
The Low-Frequency Array (LOFAR) Long-Baseline Calibrator Survey (LBCS) was conducted between 2014 and 2019 in order to obtain a set of suitable calibrators for the LOFAR array. In this paper we present the complete survey, building on the preliminary analysis published in 2016 which covered approximately half the survey area. The final catalogue consists of 30006 observations of 24713 sources in the northern sky, selected for a combination of high low-frequency radio flux density and flat spectral index using existing surveys (WENSS, NVSS, VLSS, and MSSS). Approximately one calibrator per square degree, suitable for calibration of $\geq$ 200 km baselines is identified by the detection of compact flux density, for declinations north of 30 degrees and away from the Galactic plane, with a considerably lower density south of this point due to relative difficulty in selecting flat-spectrum candidate sources in this area of the sky. Use of the VLBA calibrator list, together with statistical arguments by comparison with flux densities from lower-resolution catalogues, allow us to establish a rough flux density scale for the LBCS observations, so that LBCS statistics can be used to estimate compact flux densities on scales between 300 mas and 2 arcsec, for sources observed in the survey. The LBCS can be used to assess the structures of point sources in lower-resolution surveys, with significant reductions in the degree of coherence in these sources on scales between 2 arcsec and 300 mas. The LBCS survey sources show a greater incidence of compact flux density in quasars than in radio galaxies, consistent with unified schemes of radio sources. Comparison with samples of sources from interplanetary scintillation (IPS) studies with the Murchison Widefield Array (MWA) shows consistent patterns of detection of compact structure in sources observed both interferometrically with LOFAR and using IPS., Comment: Accepted to a special issue of A&A on sub-arcsecond imaging with LOFAR
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- 2021
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6. LOFAR imaging of Cygnus A -- Direct detection of a turnover in the hotspot radio spectra
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McKean, J. P., Godfrey, L. E. H., Vegetti, S., Wise, M. W., Morganti, R., Hardcastle, M. J., Rafferty, D., Anderson, J., Avruch, I. M., Beck, R., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Blaauw, R., Bonafede, A., Breitling, F., Broderick, J. W., Bruggen, M., Cerrigone, L., Ciardi, B., de Gasperin, F., Deller, A., Duscha, S., Engels, D., Falcke, H., Fallows, R. A., Frieswijk, W., Garrett, M. A., Griessmeier, J. M., van Haarlem, M. P., Heald, G., Hoeft, M., van der Horst, A. J., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kondratiev, V. I., Koopmans, L. V. E., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., Mulcahy, D. D., Munk, H., Nelles, A., Orru, E., Paas, H., Pandey-Pommier, M., Pietka, M., Pizzo, R., Polatidis, A. G., Reich, W., Rottgering, H. J. A., Rowlinson, A., Scaife, A. M. M., Serylak, M., Shulevski, A., Sluman, J., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Thoudam, S., Toribio, M. C., Vermeulen, R., Vocks, C., van Weeren, R. J., Wucknitz, O., Yatawatta, S., and Zarka, P.
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Astrophysics - Astrophysics of Galaxies - Abstract
The low-frequency radio spectra of the hotspots within powerful radio galaxies can provide valuable information about the physical processes operating at the site of the jet termination. These processes are responsible for the dissipation of jet kinetic energy, particle acceleration, and magnetic-field generation. Here we report new observations of the powerful radio galaxy Cygnus A using the Low Frequency Array (LOFAR) between 109 and 183 MHz, at an angular resolution of ~3.5 arcsec. The radio emission of the lobes is found to have a complex spectral index distribution, with a spectral steepening found towards the centre of the source. For the first time, a turnover in the radio spectrum of the two main hotspots of Cygnus A has been directly observed. By combining our LOFAR imaging with data from the Very Large Array at higher frequencies, we show that the very rapid turnover in the hotspot spectra cannot be explained by a low-energy cut-off in the electron energy distribution, as has been previously suggested. Thermal (free-free) absorption or synchrotron self absorption models are able to describe the low-frequency spectral shape of the hotspots, however, as with previous studies, we find that the implied model parameters are unlikely, and interpreting the spectra of the hotspots remains problematic., Comment: 9 pages, 3 figures, accepted for publication in MNRAS
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- 2021
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7. Medical and Behavioral Knowledge Discovery using Multi-Objective Analysis.
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Sanaz Mostaghim, Qihao Shan, Christiane Desel, Alexander Duscha, Aiden Haghikia, Tobias Hegelmaier, Felix Kuhn, and Stefan Remy
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- 2023
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8. LOFAR 144-MHz follow-up observations of GW170817
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Broderick, J. W., Shimwell, T. W., Gourdji, K., Rowlinson, A., Nissanke, S., Hotokezaka, K., Jonker, P. G., Tasse, C., Hardcastle, M. J., Oonk, J. B. R., Fender, R. P., Wijers, R. A. M. J., Shulevski, A., Stewart, A. J., ter Veen, S., Moss, V. A., van der Wiel, M. H. D., Nichols, D. A., Piette, A., Bell, M. E., Carbone, D., Corbel, S., Eislöffel, J., Grießmeier, J. -M., Keane, E. F., Law, C. J., Muñoz-Darias, T., Pietka, M., Serylak, M., van der Horst, A. J., van Leeuwen, J., Wijnands, R., Zarka, P., Anderson, J. M., Bentum, M. J., Blaauw, R., Brouw, W. N., Brüggen, M., Ciardi, B., de Vos, M., Duscha, S., Fallows, R. A., Franzen, T. M. O., Garrett, M. A., Gunst, A. W., Hoeft, M., Hörandel, J. R., Iacobelli, M., Jütte, E., Koopmans, L. V. E., Krankowski, A., Maat, P., Mann, G., Mulder, H., Nelles, A., Paas, H., Pandey-Pommier, M., Pekal, R., Reich, W., Röttgering, H. J. A., Schwarz, D. J., Smirnov, O., Soida, M., Toribio, M. C., van Haarlem, M. P., van Weeren, R. J., Vocks, C., Wucknitz, O., and Zucca, P.
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Astrophysics - High Energy Astrophysical Phenomena - Abstract
We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO-Virgo. These data, with a central frequency of 144 MHz, were obtained with LOFAR, the Low-Frequency Array. The maximum elevation of the target is just 13.7 degrees when observed with LOFAR, making our observations particularly challenging to calibrate and significantly limiting the achievable sensitivity. On time-scales of 130-138 and 371-374 days after the merger event, we obtain 3$\sigma$ upper limits for the afterglow component of 6.6 and 19.5 mJy beam$^{-1}$, respectively. Using our best upper limit and previously published, contemporaneous higher-frequency radio data, we place a limit on any potential steepening of the radio spectrum between 610 and 144 MHz: the two-point spectral index $\alpha^{610}_{144} \gtrsim -2.5$. We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations., Comment: 9 pages, 2 figures, accepted for publication in MNRAS
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- 2020
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9. A LOFAR Observation of Ionospheric Scintillation from Two Simultaneous Travelling Ionospheric Disturbances
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Fallows, Richard A., Forte, Biagio, Astin, Ivan, Allbrook, Tom, Arnold, Alex, Wood, Alan, Dorrian, Gareth, Mevius, Maaijke, Rothkaehl, Hanna, Matyjasiak, Barbara, Krankowski, Andrzej, Anderson, James M., Asgekar, Ashish, Avruch, I. Max, Bentum, Mark, Bisi, Mario M., Butcher, Harvey R., Ciardi, Benedetta, Dabrowski, Bartosz, Damstra, Sieds, de Gasperin, Francesco, Duscha, Sven, Eislöffel, Jochen, Franzen, Thomas M. O., Garrett, Michael A., Grie\b{eta}meier, Jean-Matthias, Gunst, André W., Hoeft, Matthias, Hörandel, Jörg R., Iacobelli, Marco, Intema, Huib T., Koopmans, Leon V. E., Maat, Peter, Mann, Gottfried, Nelles, Anna, Paas, Harm, Pandey, Vishambhar N., Reich, Wolfgang, Rowlinson, Antonia, Ruiter, Mark, Schwarz, Dominik J., Serylak, Maciej, Shulevski, Aleksander, Smirnov, Oleg M., Soida, Marian, Steinmetz, Matthias, Thoudam, Satyendra, Toribio, M. Carmen, van Ardenne, Arnold, van Bemmel, Ilse M., van der Wiel, Matthijs H. D., van Haarlem, Michiel P., Vermeulen, René C., Vocks, Christian, Wijers, Ralph A. M. J., Wucknitz, Olaf, Zarka, Philippe, and Zucca, Pietro
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Astrophysics - Earth and Planetary Astrophysics ,Physics - Geophysics ,Physics - Space Physics - Abstract
This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cas A, taken overnight on 18-19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10-80MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A cross-correlation analysis of data received by the dense array of stations in the LOFAR "core" reveals two different velocities in the scintillation pattern: a primary velocity of ~30m/s with a north-west to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ~110m/s with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller--scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported., Comment: 24 pages, 16 figures. Accepted for open-access publication in the Journal of Space Weather and Space Climate. For associated movie file, see https://www.swsc-journal.org/10.1051/swsc/2020010/olm
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- 2020
10. Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequencies
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de Gasperin, F., Vink, J., McKean, J. P., Asgekar, A., Bentum, M. J., Blaauw, R., Bonafede, A., Bruggen, M., Breitling, F., Brouw, W. N., Butcher, H. R., Ciardi, B., Cuciti, V., de Vos, M., Duscha, S., Eisloffel, J., Engels, D., Fallows, R. A., Franzen, T. M. O., Garrett, M. A., Gunst, A. W., Horandel, J., Heald, G., Koopmans, L. V. E., Krankowski, A., Maat, P., Mann, G., Mevius, M., Miley, G., Nelles, A., Norden, M. J., Offringa, A. R., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Reich, W., Rowlinson, A., Schwarz, D. J., Shulevski, A., Smirnov, O., Soida, M., Tagger, M., Toribio, M. C., van Ardenne, A., van der Horst, A. J., van Haarlem, M. P., van Weeren, R. J., Vocks, C., Wucknitz, O., Zarka, P., and Zucca, P.
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Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Astrophysics of Galaxies ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (<100 MHz) can reach several thousands of janskys, and they often contaminate observations of the low-frequency sky by interfering with image processing. Furthermore, these sources are foreground objects for all-sky observations hampering the study of faint signals, such as the cosmological 21 cm line from the epoch of reionisation. We aim to produce robust models for the surface brightness emission as a function of frequency for the A-team sources at ultra-low frequencies. These models are needed for the calibration and imaging of wide-area surveys of the sky with low-frequency interferometers. This requires obtaining images at an angular resolution better than 15 arcsec with a high dynamic range and good image fidelity. We observed the A-team with the Low Frequency Array (LOFAR) at frequencies between 30 MHz and 77 MHz using the Low Band Antenna (LBA) system. We reduced the datasets and obtained an image for each A-team source. The paper presents the best models to date for the sources Cassiopeia A, Cygnus A, Taurus A, and Virgo A between 30 MHz and 77 MHz. We were able to obtain the aimed resolution and dynamic range in all cases. Owing to its compactness and complexity, observations with the long baselines of the International LOFAR Telescope will be required to improve the source model for Cygnus A further., Comment: 7 pages, 2 figures, accepted A&A, online data on A&A website
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- 2020
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11. Carbon capture in blue hydrogen production is not where it is supposed to be - Evaluating the gap between practical experience and literature estimates
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Riemer, Matia and Duscha, Vicki
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- 2023
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12. Teachers’ competence: How to protect teachers’ mental health from the burden caused by students’ private in-class use of technical devices?
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Brailovskaia, Julia, primary, Duscha, Anna-Lena, additional, Kreyelkamp, Greta M., additional, and Margraf, Jürgen, additional
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- 2024
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13. A Ship-Based Characterization of Coherent Boundary-Layer Structures Over the Lifecycle of a Marine Cold-Air Outbreak
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Duscha, Christiane, Barrell, Christopher, Renfrew, Ian A., Brooks, Ian M., Sodemann, Harald, and Reuder, Joachim
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- 2022
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14. Shock location and CME 3D reconstruction of a solar type II radio burst with LOFAR
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Zucca, P., Morosan, D. E., Rouillard, A. P., Fallows, R., Gallagher, P. T., Magdalenic, J., Klein, K-L., Mann, G., Vocks, C., Carley, E. P., Bisi, M. M., Kontar, E. P., Rothkaehl, H., Dabrowski, B., Krankowski, A., Anderson, J., Asgekar, A., Bell, M. E., Bentum, M. J., Best, P., Blaauw, R., Breitling, F., Broderick, J. W., Brouw, W. N., Bruggen, M., Butcher, H. R., Ciardi, B., de Geus, E., Deller, A., Duscha, S., Eisloffel, J., Garrett, M. A., Grießmeier, J. M., Gunst, A. W., Heald, G., Hoeft, M., Horandel, J., Iacobelli, M., Juette, E., Karastergiou, A., van Leeuwen, J., McKay-Bukowski, D., Mulder, H., Munk, H., Nelles, A., Orru, E., Paas, H., Pandey, V. N., Pekal, R., Pizzo, R., Polatidis, A. G., Reich, W., Rowlinson, A., Schwarz, D. J., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Soida, M., Thoudam, S., Toribio, M. C., Vermeulen, R., van Weeren, R. J., Wucknitz, O., and Zarka, P.
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Astrophysics - Solar and Stellar Astrophysics - Abstract
Type II radio bursts are evidence of shocks in the solar atmosphere and inner heliosphere that emit radio waves ranging from sub-meter to kilometer lengths. These shocks may be associated with CMEs and reach speeds higher than the local magnetosonic speed. Radio imaging of decameter wavelengths (20-90 MHz) is now possible with LOFAR, opening a new radio window in which to study coronal shocks that leave the inner solar corona and enter the interplanetary medium and to understand their association with CMEs. To this end, we study a coronal shock associated with a CME and type II radio burst to determine the locations at which the radio emission is generated, and we investigate the origin of the band-splitting phenomenon., Comment: 7 Figures, 9 Pages
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- 2018
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15. Functional and structural readouts for early detection of retinal involvement in multiple sclerosis
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Khaldoon O. Al-Nosairy, Alexander Duscha, Henrike Buhr, Antonia Lipp, Christiane Desel, Tobias Hegelmaier, Hagen Thieme, Aiden Haghikia, and Michael B. Hoffmann
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MS ,optic neuritis (ON) ,electroretinography (ERG) ,mfPhNR ,mfPERG ,OCT ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 ,Neurology. Diseases of the nervous system ,RC346-429 - Abstract
IntroductionThe retina, a window into the brain, allows for the investigation of many disease-associated inflammatory and neurodegenerative changes affecting the central nervous system (CNS). Multiple sclerosis (MS), an autoimmune disease targeting the CNS, typically impacts on the visual system including the retina. Hence, we aimed to establish innovative functional retinal measures of MS-related damage, e.g., spatially resolved non-invasive retinal electrophysiology, backed by established morphological retinal imaging markers, i.e., optical coherence tomography (OCT).Methods20 healthy controls (HC) and 37 people with MS [17 without history of optic neuritis (NON) and 20 with (HON) history of optic neuritis] were included. In this work, we differentially assessed photoreceptor/bipolar cells (distal retina) and retinal ganglion cell (RGC, proximal retina) function besides structural assessment (OCT). We compared two multifocal electroretinography-based approaches, i.e., the multifocal pattern electroretinogram (mfPERG) and the multifocal electroretinogram to record photopic negative response (mfERGPhNR). Structural assessment utilized peripapillary retinal nerve fiber layer thickness (pRNFL) and macular scans to calculate outer nuclear thickness (ONL) and macular ganglion cell inner plexiform layer thickness (GCIPL). One eye was randomly selected per subject.ResultsIn NON, photoreceptor/bipolar cell layer had dysfunctional responses evidenced by reduced mfERGPhNR-N1 peak time of the summed response, but preserved structural integrity. Further, both NON and HON demonstrated abnormal RGC responses as evidenced by the photopic negative response of mfERGPhNR (mfPhNR) and mfPERG indices (P < 0.05). Structurally, only HON had thinned retina at the level of RGCs in the macula (GCIPL, P < 0.01) and the peripapillary area (pRNFL, P < 0.01). All three modalities showed good performance to differentiate MS-related damage from HC, 71–81% area under curve.ConclusionIn conclusion, while structural damage was evident mainly for HON, functional measures were the only retinal read-outs of MS-related retinal damage that were independent of optic neuritis, observed for NON. These results indicate retinal MS-related inflammatory processes in the retina prior to optic neuritis. They highlight the importance of retinal electrophysiology in MS diagnostics and its potential as a sensitive biomarker for follow-up in innovative interventions.
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- 2023
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16. The Association of a J-burst with a Solar Jet
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Morosan, D. E., Gallagher, P. T., Fallows, R. A., Reid, H., Mann, G., Bisi, M. M., Magdalenic, J., Rucker, H. O., Thide, B., Vocks, C., Anderson, J., Asgekar, A., Avruch, I. M., Bell, M. E., Bentum, M. J., Best, P., Blaauw, R., Bonafede, A., Breitling, F., Broderick, J. W., Bruggen, M., Cerrigone, L., Ciardi, B., de Geus, E., Duscha, S., Eisloffel, J., Falcke, H., Garrett, M. A., Griessmeier, J. M., Gunst, A. W., Hoeft, M., Iacobelli, M., Juette, E., Kuper, G., McFadden, R., McKay-Bukowski, D., McKean, J. P., Mulcahy, D. D., Munk, H., Nelles, A., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pizzo, R., Polatidis, A. G., Reich, W., Schwarz, D. J., Sluman, J., Smirnov, O., Steinmetz, M., Tagger, M., ter Veen, S., Thoudam, S., Toribio, M. C., Vermeulen, R., van Weeren, R. J., Wucknitz, O., and Zarka, P.
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Astrophysics - Solar and Stellar Astrophysics - Abstract
Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections and numerous smaller-scale events such as solar jets. These events are often associated with accelerated particles that can cause emission at radio wavelengths. The reconfiguration of the solar magnetic field in the corona is believed to be the cause of the majority of solar energetic events and accelerated particles. Aims. Here, we investigate a bright J-burst that was associated with a solar jet and the possible emission mechanism causing these two phenomena. Methods. We used data from the Solar Dynamics Observatory (SDO) to observe a solar jet, and radio data from the Low Frequency Array (LOFAR) and the Nan\c{c}ay Radioheliograph (NRH) to observe a J-burst over a broad frequency range (33-173 MHz) on 9 July 2013 at ~11:06 UT. Results. The J-burst showed fundamental and harmonic components and it was associated with a solar jet observed at extreme ultraviolet wavelengths with SDO. The solar jet occurred at a time and location coincident with the radio burst, in the northern hemisphere, and not inside a group of complex active regions in the southern hemisphere. The jet occurred in the negative polarity region of an area of bipolar plage. Newly emerged positive flux in this region appeared to be the trigger of the jet. Conclusions. Magnetic reconnection between the overlying coronal field lines and the newly emerged positive field lines is most likely the cause of the solar jet. Radio imaging provides a clear association between the jet and the J-burst which shows the path of the accelerated electrons., Comment: 11 pages, 8 figures
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- 2017
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17. Evaluating the Performance of Pulsed and Continuous-Wave Lidar Wind Profilers with a Controlled Motion Experiment.
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Malekmohammadi, Shokoufeh, Duscha, Christiane, Jenkins, Alastair D., Kelberlau, Felix, Gottschall, Julia, and Reuder, Joachim
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- *
ROTATIONAL motion , *DEGREES of freedom , *LIDAR , *TURBULENCE , *PERCENTILES - Abstract
While floating wind lidars provide reliable and cost-effective measurements, these measurements may be inaccurate due to the motion of the installation platforms. Prior studies have not distinguished between systematic errors associated with lidars and errors resulting from motion. This study will fill this gap by examining the impact of platform motion on two types of profiling wind lidar systems: the pulsed WindCube V1 (Leosphere) and the continuous-wave ZephIR 300 (Natural Power). On a moving hexapod platform, both systems were subjected to 50 controlled sinusoidal motion cases in different degrees of freedom. Two reference lidars were placed at a distance of five meters from the platform as reference lidars. Motion-induced errors in mean wind speed and turbulence intensity estimation by lidars are analyzed. Additionally, the effectiveness of a motion correction approach in reducing these errors across various scenarios is evaluated. The results indicate that presence of rotational motion leads to higher turbulence intensity (TI) estimation by moving lidars. The absolute percentage error between lidars is the highest when lidars are exposed to yaw and heave motion and is the lowest when exposed to surge motion. The correlation between lidars, though it is the lowest in the presence of pitch, yaw, and heave motion. Furthermore, applying motion compensation can compensate the correlation drop and erroneous TI estimation. [ABSTRACT FROM AUTHOR]
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- 2024
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18. ACL Injury Prevention Education Improves Implementation of Neuromuscular Training Among High School Sports Coaches: A Cross-Sectional Survey Study.
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Janosky, Joseph J., Russomano, James, Duscha, Connor, Henderson, Alexandra, Archer, Alexandra, Kinderknecht, James J., and Marx, Robert G.
- Abstract
Background: Neuromuscular training (NMT) programs delivered by trained personnel have demonstrated protective effects against anterior cruciate ligament (ACL) injury among high school sports participants, but few studies have investigated the impact of education on high school sports coaches' knowledge and incorporation of NMT programs into daily practice sessions. Purpose: We sought to evaluate changes in knowledge and behavior among high school sports coaches who completed an NMT-based injury prevention training program. Methods: High school sports coaches were invited to complete a free online training course in incorporating NMT into daily practice sessions. Anonymized surveys were administered before and after education and at 3 months to evaluate knowledge level and program effectiveness. Results: Of the 13,640 coaches who enrolled in the training course in 2019, 1641 submitted pre- and post-education and 3-month follow-up surveys. Prior to training, 4.4% reported incorporating NMT into daily training sessions and the mean knowledge score was 1.89 ± 1.55. After training, 92.7% of participants reported that they intended to incorporate NMT into their daily training sessions and the mean knowledge score was 4.87 ± 1.11. At 3-month follow-up, 88.9% of participants reported incorporating NMT into daily training sessions. A chi-square test revealed a significant association between pre- and post-education incorporation of NMT into daily practice sessions, and a multiple regression analysis resulted in a significant model with intent to incorporate NMT into daily practice sessions identified as a significant behavior predictor. Conclusion: These survey results show that completion of a training course significantly improved ACL injury prevention knowledge among a cohort of high school sports coaches and likely contributed to the sustained incorporation of NMT into their daily practice sessions. [ABSTRACT FROM AUTHOR]
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- 2024
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19. Methodik der IT-Prüfung
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Duscha, Peter, Sowa, Aleksandra, Duscha, Peter, and Schreiber, Sebastian
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- 2019
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20. Audit, Continuous Audit, Monitoring und Revision
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Duscha, Peter, Sowa, Aleksandra, Duscha, Peter, and Schreiber, Sebastian
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- 2019
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21. Einleitung
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Sowa, Aleksandra, Duscha, Peter, Schreiber, Sebastian, Sowa, Aleksandra, Duscha, Peter, and Schreiber, Sebastian
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- 2019
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22. 'Für die Ausübung ihrer zukünftigen Freiheit' – Öffentlichkeitsarbeit als gesellschaftliche Veränderungspraxis
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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23. 'Sozusagen das Leben nochmal aufbauen für die' – Beratungsprozesse zwischen Bevormundung und Ermächtigung
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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24. 'Politik ist wie Schokolade – schmeckt gut!' – Mobilisierung als Weg zur politischen Selbstverwirklichung
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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25. Methodische und methodologische Zugänge: Die Erforschung der Sozialraum- und Unterstützungskonstruktionen einer Migrantinnenorganisation mit der Grounded Theory
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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26. Doing Mulher: die Rahmenstrategie der 'Basisorganisation' durch 'Basisarbeit'
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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27. Der brasilianische Migrantinnenverein Mulher: Entstehung der Unterstützungsaktivitäten
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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28. Die Entdeckung von MigrantInnenorganisationen durch die Soziale Arbeit in Deutschland: vom Integrationshindernis zur (semi-)professionellen (Selbst-)Hilfeinstanz
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Duscha, Annemarie and Duscha, Annemarie
- Published
- 2019
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29. Soziale Arbeit im Angesicht von Migration, Globalisierung und Transnationalität
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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30. Zentrale Ergebnisse und Ausblick
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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31. Modell selbstorganisierter transnationaler sozialer Unterstützung bei migrationsbedingten Belastungen
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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32. Besonderheiten der mulherschen Lesart von Basisorganisation
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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33. 'In Brasilien ein neues Leben anfangen': die grenzüber spannende Arbeit mit brasilianischen Häftlingen und ihren Familien
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Duscha, Annemarie and Duscha, Annemarie
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- 2019
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34. Zusammenfassung
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Ihlau, Susann, Duscha, Hendrik, Ihlau, Susann, and Duscha, Hendrik
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- 2019
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35. Grundlagen der Unternehmensbewertung
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Ihlau, Susann, Duscha, Hendrik, Ihlau, Susann, and Duscha, Hendrik
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- 2019
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36. Besonderheiten bei der Bewertung von KMU
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Ihlau, Susann, Duscha, Hendrik, Ihlau, Susann, and Duscha, Hendrik
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- 2019
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37. Spezifische Merkmale und Besonderheiten von KMU
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Ihlau, Susann, Duscha, Hendrik, Ihlau, Susann, and Duscha, Hendrik
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- 2019
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38. The COTUR project: remote sensing of offshore turbulence for wind energy application
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E. Cheynet, M. Flügge, J. Reuder, J. B. Jakobsen, Y. Heggelund, B. Svardal, P. Saavedra Garfias, C. Obhrai, N. Daniotti, J. Berge, C. Duscha, N. Wildmann, I. H. Onarheim, and M. Godvik
- Subjects
Environmental engineering ,TA170-171 ,Earthwork. Foundations ,TA715-787 - Abstract
The paper presents the measurement strategy and data set collected during the COTUR (COherence of TURbulence with lidars) campaign. This field experiment took place from February 2019 to April 2020 on the southwestern coast of Norway. The coherence quantifies the spatial correlation of eddies and is little known in the marine atmospheric boundary layer. The study was motivated by the need to better characterize the lateral coherence, which partly governs the dynamic wind load on multi-megawatt offshore wind turbines. During the COTUR campaign, the coherence was studied using land-based remote sensing technology. The instrument setup consisted of three long-range scanning Doppler wind lidars, one Doppler wind lidar profiler and one passive microwave radiometer. Both the WindScanner software and LidarPlanner software were used jointly to simultaneously orient the three scanner heads into the mean wind direction, which was provided by the lidar wind profiler. The radiometer instrument complemented these measurements by providing temperature and humidity profiles in the atmospheric boundary layer. The scanning beams were pointed slightly upwards to record turbulence characteristics both within and above the surface layer, providing further insight on the applicability of surface-layer scaling to model the turbulent wind load on offshore wind turbines. The preliminary results show limited variations of the lateral coherence with the scanning distance. A slight increase in the identified Davenport decay coefficient with the height is partly due to the limited pointing accuracy of the instruments. These results underline the importance of achieving pointing errors under 0.1∘ to study properly the lateral coherence of turbulence at scanning distances of several kilometres.
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- 2021
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39. A large light-mass component of cosmic rays at 10^{17} - 10^{17.5} eV from radio observations
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Buitink, S., Corstanje, A., Falcke, H., Hörandel, J. R., Huege, T., Nelles, A., Rachen, J. P., Rossetto, L., Schellart, P ., Scholten, O., ter Veen, S., Thoudam, S., Trinh, T. N. G., Anderson, J., Asgekar, A., Avruch, I. M., Bell, M. E., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J. W., Brouw, W. N., Brüggen, M., Butcher, H. R., Carbone, D., Ciardi, B., Conway, J. E., de Gasperin, F., de Geus, E., Deller, A., Dettmar, R. -J., van Diepen, G., Duscha, S., Eislöffel, J., Engels, D., Enriquez, J. E., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Griessmeier, J. M., Gunst, A. W., van Haarlem, M. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, A., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Loose, G. M., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J. P., Mevius, M., Mulcahy, D. D., Munk, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pietka, M., Pizzo, R., Polatidis, A. G., Reich, W., Röttgering, H. J. A., Scaife, A. M. M., Schwarz, D. J., Serylak, M., Sluman, J., Smirnov, O., Stappers, B. W., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Toribio, M. C., Vermeulen, R., Vocks, C., Vogt, C., van Weeren, R. J., Wijers, R. A. M. J., Wijnholds, S. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, J. A.
- Subjects
Astrophysics - High Energy Astrophysical Phenomena ,High Energy Physics - Experiment - Abstract
Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10^{17} eV and 10^{18} eV are essential to understand whether this energy range is dominated by Galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate cascades of secondary particles (air showers) in the atmosphere and their masses are inferred from measurements of the atmospheric depth of the shower maximum, Xmax, or the composition of shower particles reaching the ground. Current measurements suffer from either low precision, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique, suitable for determination of Xmax with a duty cycle of in principle nearly 100%. The radiation is generated by the separation of relativistic charged particles in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean precision of 16 g/cm^2 between 10^{17}-10^{17.5} eV. Because of the high resolution in $Xmax we can determine the mass spectrum and find a mixed composition, containing a light mass fraction of ~80%. Unless the extragalactic component becomes significant already below 10^{17.5} eV, our measurements indicate an additional Galactic component dominating at this energy range., Comment: 35 pages, 11 figures, updated version: Pierre Auger Observatory data ICRC 2015 added to Fig 2
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- 2016
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40. LOFAR MSSS: Detection of a low-frequency radio transient in 400 hrs of monitoring of the North Celestial Pole
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Stewart, A. J., Fender, R. P., Broderick, J. W., Hassall, T. E., Muñoz-Darias, T., Rowlinson, A., Swinbank, J. D., Staley, T. D., Molenaar, G. J., Scheers, B., Grobler, T. L., Pietka, M., Heald, G., McKean, J. P., Bell, M. E., Bonafede, A., Breton, R. P., Carbone, D., Cendes, Y., Clarke, A. O., Corbel, S., de Gasperin, F., Eislöffel, J., Falcke, H., Ferrari, C., Grießmeier, J. -M., Hardcastle, M. J., Heesen, V., Hessels, J. W. T., Horneffer, A., Iacobelli, M., Jonker, P., Karastergiou, A., Kokotanekov, G., Kondratiev, V. I., Kuniyoshi, M., Law, C. J., van Leeuwen, J., Markoff, S., Miller-Jones, J. C. A., Mulcahy, D., Orru, E., Pandey-Pommier, M., Pratley, L., Rol, E., Röttgering, H. J. A., Scaife, A. M. M., Shulevski, A., Sobey, C. A., Stappers, B. W., Tasse, C., van der Horst, A. J., van Velzen, S., van Weeren, R. J., Wijers, R. A. M. J., Wijnands, R., Wise, M., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, I. M., Bentum, M. J., Bernardi, G., Best, P., Breitling, F., Brüggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., Corstanje, A., de Geus, E., Deller, A., Duscha, S., Frieswijk, W., Garrett, M. A., Gunst, A. W., van Haarlem, M. P., Hoeft, M., Hörandel, J., Juette, E., Kuper, G., Loose, M., Maat, P., McFadden, R., McKay-Bukowski, D., Moldon, J., Munk, H., Norden, M. J., Paas, H., Polatidis, A. G., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Thoudam, S., Toribio, M. C., Vermeulen, R., Vocks, C., Wijnholds, S. J., Wucknitz, O., and Yatawatta, S.
- Subjects
Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We present the results of a four-month campaign searching for low-frequency radio transients near the North Celestial Pole with the Low-Frequency Array (LOFAR), as part of the Multifrequency Snapshot Sky Survey (MSSS). The data were recorded between 2011 December and 2012 April and comprised 2149 11-minute snapshots, each covering 175 deg^2. We have found one convincing candidate astrophysical transient, with a duration of a few minutes and a flux density at 60 MHz of 15-25 Jy. The transient does not repeat and has no obvious optical or high-energy counterpart, as a result of which its nature is unclear. The detection of this event implies a transient rate at 60 MHz of 3.9 (+14.7, -3.7) x 10^-4 day^-1 deg^-2, and a transient surface density of 1.5 x 10^-5 deg^-2, at a 7.9-Jy limiting flux density and ~10-minute time-scale. The campaign data were also searched for transients at a range of other time-scales, from 0.5 to 297 min, which allowed us to place a range of limits on transient rates at 60 MHz as a function of observation duration., Comment: 23 pages, 16 figures, 5 tables, accepted for publication in MNRAS
- Published
- 2015
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41. Imaging Jupiter's radiation belts down to 127 MHz with LOFAR
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Girard, J. N., Zarka, P., Tasse, C., Hess, S., de Pater, I., Santos-Costa, D., Nenon, Q., Sicard, A., Bourdarie, S., Anderson, J., Asgekar, A., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Breton, R. P., Broderick, J. W., Brouw, W. N., Brüggen, M., Ciardi, B., Corbel, S., Corstanje, A., de Gasperin, F., de Geus, E., Deller, A., Duscha, S., Eislöffel, J., Falcke, H., Frieswijk, W., Garrett, M. A., Grießmeier, J., Gunst, A. W., Hessels, J. W. T., Hoeft, M., Hörandel, J., Iacobelli, M., Juette, E., Kondratiev, V. I., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Loose, M., Maat, P., Mann, G., Markov, S., McFadden, R., McKay-Bukowski, D., Moldon, J., Munk, H., Nelles, A., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A. G., Reich, W., Röttgering, H., Rowlinson, A., Schwarz, D., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Thoudam, S., Toribio, M. C., Vermeulen, R., Vocks, C., van Weeren, R. J., Wijers, R. A. M. J., and Wucknitz, O.
- Subjects
Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
Context. Observing Jupiter's synchrotron emission from the Earth remains today the sole method to scrutinize the distribution and dynamical behavior of the ultra energetic electrons magnetically trapped around the planet (because in-situ particle data are limited in the inner magnetosphere). Aims. We perform the first resolved and low-frequency imaging of the synchrotron emission with LOFAR at 127 MHz. The radiation comes from low energy electrons (~1-30 MeV) which map a broad region of Jupiter's inner magnetosphere. Methods (see article for complete abstract) Results. The first resolved images of Jupiter's radiation belts at 127-172 MHz are obtained along with total integrated flux densities. They are compared with previous observations at higher frequencies and show a larger extent of the synchrotron emission source (>=4 $R_J$). The asymmetry and the dynamic of east-west emission peaks are measured and the presence of a hot spot at lambda_III=230 {\deg} $\pm$ 25 {\deg}. Spectral flux density measurements are on the low side of previous (unresolved) ones, suggesting a low-frequency turnover and/or time variations of the emission spectrum. Conclusions. LOFAR is a powerful and flexible planetary imager. The observations at 127 MHz depict an extended emission up to ~4-5 planetary radii. The similarities with high frequency results reinforce the conclusion that: i) the magnetic field morphology primarily shapes the brightness distribution of the emission and ii) the radiating electrons are likely radially and latitudinally distributed inside about 2 $R_J$. Nonetheless, the larger extent of the brightness combined with the overall lower flux density, yields new information on Jupiter's electron distribution, that may shed light on the origin and mode of transport of these particles., Comment: 10 pages, 12 figures, accepted for publication in A&A (27/11/2015) - abstract edited because of limited characters
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- 2015
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42. Propionic acid beneficially modifies osteoporosis biomarkers in patients with multiple sclerosis
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Alexander Duscha, Tobias Hegelmaier, Kerstin Dürholz, Christiane Desel, Ralf Gold, Mario M. Zaiss, and Aiden Haghikia
- Subjects
Neurology. Diseases of the nervous system ,RC346-429 - Abstract
Background: The impact of the gut and its microbiota are increasingly appreciated in health and disease. Short-chain fatty acids (SCFAs) are among the main metabolites synthesized from bacterial fermentation. Recently, we showed the anti-inflammatory and potentially neuroprotective effect of propionic acid (PA) in multiple sclerosis (MS). Osteoporosis is one of the most common co-morbidities for MS patients with limited therapeutic options available. Osteoporosis is closely linked to an imbalance of cells of the immune system and an immune-mediated impact on bone structure via the gut has been shown. Interestingly, intake of SCFA leads to bone mass increase and concomitant reduction of inflammation-induced bone loss in mice. Objective: To determine the impact of PA supplementation on markers of bone metabolism in MS patients. Methods: We investigated the influence of 14 days supplementation with PA on bone metabolism in 20 MS patients. To this end, β-CrossLaps and osteocalcin, established markers of bone metabolism, were measured in serum before and after PA intake and correlated with phenotypic and functional immunodata. Results: Supplementation with PA induced a significant increase in serum levels of osteocalcin, a surrogate marker for bone formation. Levels of β-CrossLaps, a marker for bone resorption, were significantly decreased after therapy. Regulatory T-cell (Treg) numbers and suppressive capacity positively correlated with serum levels of osteocalcin while Th17 cell numbers showed an inverse correlation. Our findings are in line with animal studies showing that SCFA induced increased bone formation and reduced bone resorption. Conclusion: In addition to its immune regulatory, disease-modifying effect on MS disease course, supplementation with PA beneficially influences serum levels of β-CrossLaps and osteocalcin and may thus also protect against osteoporosis, a common co-morbidity in MS.
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- 2022
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43. Wide-Band, Low-Frequency Pulse Profiles of 100 Radio Pulsars with LOFAR
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Pilia, M., Hessels, J. W. T., Stappers, B. W., Kondratiev, V. I., Kramer, M., van Leeuwen, J., Weltevrede, P., Lyne, A. G., Zagkouris, K., Hassall, T. E., Bilous, A. V., Breton, R. P., Falcke, H., Grießmeier, J. -M., Keane, E., Karastergiou, A., Kuniyoshi, M., Noutsos, A., Osłowski, S., Serylak, M., Sobey, C., ter Veen, S., Alexov, A., Anderson, J., Asgekar, A., Avruch, I. M., Bell, M. E., Bentum, M. J., Bernardi, G., Bîrzan, L., Bonafede, A., Breitling, F., Broderick, J. W., Brüggen, M., Ciardi, B., Corbel, S., de Geus, E., de Jong, A., Deller, A., Duscha, S., Eislöffel, J., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Gunst, A. W., Hamaker, J. P., Heald, G., Horneffer, A., Jonker, P., Juette, E., Kuper, G., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., Miller-Jones, J. C. A., Nelles, A., Paas, H., Pandey-Pommier, M., Pietka, M., Pizzo, R., Polatidis, A. G., Reich, W., Röttgering, H., Rowlinson, A., Schwarz, D., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J. D., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, M. C., van der Horst, A. J., Vermeulen, R., Vocks, C., van Weeren, R. J., Wijers, R. A. M. J., Wijnands, R., Wijnholds, S. J., Wucknitz, O., and Zarka, P.
- Subjects
Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Astrophysics of Galaxies ,Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
LOFAR offers the unique capability of observing pulsars across the 10-240 MHz frequency range with a fractional bandwidth of roughly 50%. This spectral range is well-suited for studying the frequency evolution of pulse profile morphology caused by both intrinsic and extrinsic effects: such as changing emission altitude in the pulsar magnetosphere or scatter broadening by the interstellar medium, respectively. The magnitude of most of these effects increases rapidly towards low frequencies. LOFAR can thus address a number of open questions about the nature of radio pulsar emission and its propagation through the interstellar medium. We present the average pulse profiles of 100 pulsars observed in the two LOFAR frequency bands: High Band (120-167 MHz, 100 profiles) and Low Band (15-62 MHz, 26 profiles). We compare them with Westerbork Synthesis Radio Telescope (WSRT) and Lovell Telescope observations at higher frequencies (350 and1400 MHz) in order to study the profile evolution. The profiles are aligned in absolute phase by folding with a new set of timing solutions from the Lovell Telescope, which we present along with precise dispersion measures obtained with LOFAR. We find that the profile evolution with decreasing radio frequency does not follow a specific trend but, depending on the geometry of the pulsar, new components can enter into, or be hidden from, view. Nonetheless, in general our observations confirm the widening of pulsar profiles at low frequencies, as expected from radius-to-frequency mapping or birefringence theories. We offer this catalog of low-frequency pulsar profiles in a user friendly way via the EPN Database of Pulsar Profiles (http://www.epta.eu.org/epndb/)., Comment: 38 pages, 11 figures, 5 tables, A&A in press, updated with editorial corrections
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- 2015
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44. The LOFAR Multifrequency Snapshot Sky Survey (MSSS) I. Survey description and first results
- Author
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Heald, G. H., Pizzo, R. F., Orrú, E., Breton, R. P., Carbone, D., Ferrari, C., Hardcastle, M. J., Jurusik, W., Macario, G., Mulcahy, D., Rafferty, D., Asgekar, A., Brentjens, M., Fallows, R. A., Frieswijk, W., Toribio, M. C., Adebahr, B., Arts, M., Bell, M. R., Bonafede, A., Bray, J., Broderick, J., Cantwell, T., Carroll, P., Cendes, Y., Clarke, A. O., Croston, J., Daiboo, S., de Gasperin, F., Gregson, J., Harwood, J., Hassall, T., Heesen, V., Horneffer, A., van der Horst, A. J., Iacobelli, M., Jelić, V., Jones, D., Kant, D., Kokotanekov, G., Martin, P., McKean, J. P., Morabito, L. K., Nikiel-Wroczyński, B., Offringa, A., Pandey, V. N., Pandey-Pommier, M., Pietka, M., Pratley, L., Riseley, C., Rowlinson, A., Sabater, J., Scaife, A. M. M., Scheers, L. H. A., Sendlinger, K., Shulevski, A., Sipior, M., Sobey, C., Stewart, A. J., Stroe, A., Swinbank, J., Tasse, C., Trüstedt, J., Varenius, E., van Velzen, S., Vilchez, N., van Weeren, R. J., Wijnholds, S., Williams, W. L., de Bruyn, A. G., Nijboer, R., Wise, M., Alexov, A., Anderson, J., Avruch, I. M., Beck, R., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Breitling, F., Brouw, W. N., Brüggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., de Geus, E., de Jong, A., de Vos, M., Deller, A., Dettmar, R. J., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fender, R., Garrett, M. A., Grießmeier, J., Gunst, A. W., Hamaker, J. P., Hessels, J. W. T., Hoeft, M., Hörandel, J., Holties, H. A., Intema, H., Jackson, N. J., Jütte, E., Karastergiou, A., Klijn, W. F. A., Kondratiev, V. I., Koopmans, L. V. E., Kuniyoshi, M., Kuper, G., Law, C., van Leeuwen, J., Loose, M., Maat, P., Markoff, S., McFadden, R., McKay-Bukowski, D., Mevius, M., Miller-Jones, J. C. A., Morganti, R., Munk, H., Nelles, A., Noordam, J. E., Norden, M. J., Paas, H., Polatidis, A. G., Reich, W., Renting, A., Röttgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B. W., Steinmetz, M., Tagger, M., Tang, Y., ter Veen, S., Thoudam, S., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., Wucknitz, O., Yatawatta, S., and Zarka, P.
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR's multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the "MSSS Verification Field" (MVF), a region of 100 square degrees centered at J2000 (RA,Dec)=(15h,69deg). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108" resolution, and 550 mJy at 50 MHz with 166" resolution. Images and catalogs for the full survey, expected to contain 150,000-200,000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs., Comment: 23 pages, 19 figures. Accepted for publication in Astronomy & Astrophysics. MSSS Verification Field images and catalog data may be downloaded from http://vo.astron.nl
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- 2015
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45. Calibrating the absolute amplitude scale for air showers measured at LOFAR
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Nelles, A., Hörandel, J. R., Karskens, T., Krause, M., Buitink, S., Corstanje, A., Enriquez, J. E., Erdmann, M., Falcke, H., Haungs, A., Hiller, R., Huege, T., Krause, R., Link, K., Norden, M. J., Rachen, J. P., Rossetto, L., Schellart, P., Scholten, O., Schröder, F. G., ter Veen, S., Thoudam, S., Trinh, T. N. G., Weidenhaupt, K., Wijnholds, S. J., Anderson, J., Bähren, L., Bell, M. E., Bentum, M. J., Best, P., Bonafede, A., Bregman, J., Brouw, W. N., Bruüggen, M., Butcher, H. R., Carbone, D., Ciardi, B., de Gasperin, F., Duscha, S., Eislöffel, J., Fallows, R. A., Frieswijk, W., Garrett, M. A., van Haarlem, M. P., Heald, G., Hoeft, M., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V. I., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., McFadden, R., McKay-Bukowski, D., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pizzo, R., Polatidis, A. G., Reich, W., Röttgering, H., Schwarz, D., Serylak, M., Sluman, J., Smirnov, O., Tasse, C., Toribio, M. C., Vermeulen, R., van Weeren, R. J., Wijers, R. A. M. J., Wucknitz, O., and Zarka, P.
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Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
Air showers induced by cosmic rays create nanosecond pulses detectable at radio frequencies. These pulses have been measured successfully in the past few years at the LOw Frequency ARray (LOFAR) and are used to study the properties of cosmic rays. For a complete understanding of this phenomenon and the underlying physical processes, an absolute calibration of the detecting antenna system is needed. We present three approaches that were used to check and improve the antenna model of LOFAR and to provide an absolute calibration of the whole system for air shower measurements. Two methods are based on calibrated reference sources and one on a calibration approach using the diffuse radio emission of the Galaxy, optimized for short data-sets. An accuracy of 19% in amplitude is reached. The absolute calibration is also compared to predictions from air shower simulations. These results are used to set an absolute energy scale for air shower measurements and can be used as a basis for an absolute scale for the measurement of astronomical transients with LOFAR., Comment: 34 pages, 10 figures
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- 2015
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46. LOFAR discovery of a quiet emission mode in PSR B0823+26
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Sobey, C., Young, N. J., Hessels, J. W. T., Weltevrede, P., Noutsos, A., Stappers, B. W., Kramer, M., Bassa, C., Lyne, A. G., Kondratiev, V. I., Hassall, T. E., Keane, E. F., Bilous, A. V., Breton, R. P., Grießmeier, J. -M., Karastergiou, A., Pilia, M., Serylak, M., ter Veen, S., van Leeuwen, J., Alexov, A., Anderson, J., Asgekar, A., Avruch, I. M., Bell, M. E., Bentum, M. J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Corstanje, A., Carbone, D., de Geus, E., de Vos, M., van Duin, A., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Gunst, A. W., Hamaker, J. P., Heald, G., Hoeft, M., Hörandel, J., Jütte, E., Kuper, G., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J. P., Mulcahy, D. D., Munk, H., Nelles, A., Norden, M. J., Orrù, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pietka, G., Pizzo, R., Polatidis, A. G., Rafferty, D., Renting, A., Röttgering, H., Rowlinson, A., Scaife, A. M. M., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., van Weeren, R. J., Wijers, R. A. M. J., Wise, M. W., Wucknitz, O., Yatawatta, S., and Zarka, P.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over timescales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insight into the relationship between these various emission phenomena and what they might teach us about pulsar magnetospheres. Here we report on the LOFAR discovery that PSR B0823+26 has a weak and sporadically emitting 'quiet' (Q) emission mode that is over 100 times weaker (on average) and has a nulling fraction forty-times greater than that of the more regularly-emitting 'bright' (B) mode. Previously, the pulsar has been undetected in the Q-mode, and was assumed to be nulling continuously. PSR B0823+26 shows a further decrease in average flux just before the transition into the B-mode, and perhaps truly turns off completely at these times. Furthermore, simultaneous observations taken with the LOFAR, Westerbork, Lovell, and Effelsberg telescopes between 110 MHz and 2.7 GHz demonstrate that the transition between the Q-mode and B-mode occurs within one single rotation of the neutron star, and that it is concurrent across the range of frequencies observed., Comment: 15 pages, 8 figures, 2 tables, accepted for publication in MNRAS
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- 2015
47. The peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?
- Author
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Shulevski, A., Morganti, R., Barthel, P. D., Murgia, M., van Weeren, R. J., White, G. J., Brüggen, M., Kunert-Bajraszewska, M., Jamrozy, M., Best, P. N., Röttgering, H. J. A., Chyzy, K. T., de Gasperin, F., Bîrzan, L., Brunetti, G., Brienza, M., Rafferty, D. A., Anderson, J., Beck, R., Deller, A., Zarka, P., Schwarz, D., Mahony, E., Orrú, E., Bell, M. E., Bentum, M. J., Bernardi, G., Bonafede, A., Breitling, F., Broderick, J. W., Butcher, H. R., Carbone, D., Ciardi, B., de Geus, E., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Grießmeier, J., Gunst, A. W., Heald, G., Hoeft, M., Hörandel, J., Horneffer, A., van der Horst, A. J., Intema, H., Juette, E., Karastergiou, A., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., McFadden, R., McKay-Bukowski, D., McKean, J. P., Meulman, H., Mulcahy, D. D., Munk, H., Norden, M. J., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A. G., Reich, W., Rowlinson, A., Scaife, A. M. M., Serylak, M., Sluman, J., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, M. C., Vermeulen, R., Vocks, C., Wijers, R. A. M. J., Wise, M. W., and Wucknitz, O.
- Subjects
Astrophysics - Astrophysics of Galaxies ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Using observations obtained with the LOw Fequency ARray (LOFAR), the Westerbork Synthesis Radio Telescope (WSRT) and archival Very Large Array (VLA) data, we have traced the radio emission to large scales in the complex source 4C 35.06 located in the core of the galaxy cluster Abell 407. At higher spatial resolution (~4"), the source was known to have two inner radio lobes spanning 31 kpc and a diffuse, low-brightness extension running parallel to them, offset by about 11 kpc (in projection). At 62 MHz, we detect the radio emission of this structure extending out to 210 kpc. At 1.4 GHz and intermediate spatial resolution (~30"), the structure appears to have a helical morphology. We have derived the characteristics of the radio spectral index across the source. We show that the source morphology is most likely the result of at least two episodes of AGN activity separated by a dormant period of around 35 Myr. The AGN is hosted by one of the galaxies located in the cluster core of Abell 407. We propose that it is intermittently active as it moves in the dense environment in the cluster core. Using LOFAR, we can trace the relic plasma from that episode of activity out to greater distances from the core than ever before. Using the the WSRT, we detect HI in absorption against the center of the radio source. The absorption profile is relatively broad (FWHM of 288 km/s), similar to what is found in other clusters. Understanding the duty cycle of the radio emission as well as the triggering mechanism for starting (or restarting) the radio-loud activity can provide important constraints to quantify the impact of AGN feedback on galaxy evolution. The study of these mechanisms at low frequencies using morphological and spectral information promises to bring new important insights in this field., Comment: 10 pages, 6 figures. Accepted to A&A
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- 2015
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48. Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers
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Schellart, P., Trinh, T. N. G., Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., Hörandel, J. R., Nelles, A., Rachen, J. P., Rossetto, L., Scholten, O., ter Veen, S., Thoudam, S., Ebert, U., Koehn, C., Rutjes, C., Alexov, A., Anderson, J. M., Avruch, I. M., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J. W., Brüggen, M., Butcher, H. R., Ciardi, B., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Fallows, R. A., Frieswijk, W., Garrett, M. A., Grießmeier, J., Gunst, A. W., Heald, G., Hessels, J. W. T., Hoeft, M., Holties, H. A., Juette, E., Kondratiev, V. I., Kuniyoshi, M., Kuper, G., Mann, G., McFadden, R., McKay-Bukowski, D., McKean, J. P., Mevius, M., Moldon, J., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A. G., Reich, W., Röttgering, H., Scaife, A. M. M., Schwarz, D. J., Serylak, M., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Tasse, C., Toribio, M. C., van Weeren, R. J., Vermeulen, R., Vocks, C., Wise, M. W., Wucknitz, O., and Zarka, P.
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Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields., Comment: 6 pages, 3 figures, accepted for publication in Physical Review Letters
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- 2015
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49. Einleitung
- Author
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Duscha, Annemarie and Duscha, Annemarie
- Published
- 2019
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50. Measuring a Cherenkov ring in the radio emission from air showers at 110-190 MHz with LOFAR
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Nelles, A., Schellart, P., Buitink, S., Corstanje, A., de Vries, K. D., Enriquez, J. E., Falcke, H., Frieswijk, W., Hörandel, J. R., Scholten, O., ter Veen, S., Thoudam, S., Akker, M. van den, Anderson, J., Asgekar, A., Bell, M. E., Bentum, M. J., Bernardi, G., Best, P., Bregman, J., Breitling, F., Broderick, J., Brouw, W. N., Brüggen, M., Butcher, H. R., Ciardi, B., Deller, A., Duscha, S., Eislöffel, J., Fallows, R. A., Garrett, M. A., Gunst, A. W., Hassall, T. E., Heald, G., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., Mevius, M., Norden, M. J., Paas, H., Pandey-Pommier, M., Pietka, G., Pizzo, R., Polatidis, A. G., Reich, W., Röttgering, H., Scaife, A. M. M., Schwarz, D., Smirnov, O., Stapper, B. W., Steinmetz, M., Stewart, A., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., van Weeren, R. J., Wijnholds, S. J., Wucknitz, O., Yatawatta, S., and Zarka, P.
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
Measuring radio emission from air showers offers a novel way to determine properties of the primary cosmic rays such as their mass and energy. Theory predicts that relativistic time compression effects lead to a ring of amplified emission which starts to dominate the emission pattern for frequencies above ~100 MHz. In this article we present the first detailed measurements of this structure. Ring structures in the radio emission of air showers are measured with the LOFAR radio telescope in the frequency range of 110 - 190 MHz. These data are well described by CoREAS simulations. They clearly confirm the importance of including the index of refraction of air as a function of height. Furthermore, the presence of the Cherenkov ring offers the possibility for a geometrical measurement of the depth of shower maximum, which in turn depends on the mass of the primary particle., Comment: 20 pages, 10 figures, accpeted for publication in Astroparticle Physics
- Published
- 2014
- Full Text
- View/download PDF
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