304 results on '"Louarn P"'
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2. The older the better? Delayed complementarity, overyielding, and improved residue composition in ageing alfalfa-fescue mixtures
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Louarn, Gaëtan, Edouard, Sylvain, Barre, Philippe, Julier, Bernadette, and Gastal, François
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- 2024
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3. Genetic variation and morphogenetic determinants of root-shoot allocation in two perennial forage legumes
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Aillery, Valentin, Vleugels, Tim, Cnops, Gerda, De Swaef, Tom, Gentelet, Florian, Jeudy, Christian, Lamboeuf, Mickaël, Lootens, Peter, Roy, Eric, Salon, Christophe, and Louarn, Gaëtan
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- 2024
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4. Impact of intraspecific genetic variation on interspecific competition: a theoretical case study of forage binary mixtures
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Béatrice Wolff, Bernadette Julier, and Gaëtan Louarn
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multi-species grasslands ,genetic diversity ,individual-based model ,competition ,complementarity ,overyielding ,Plant culture ,SB1-1110 - Abstract
IntroductionIncreasing intraspecific genetic variation (IV) has been identified as a potential factor to improve productivity and stabilise botanical composition in plant communities. In grasslands systems, this could offer a lever to manage uncertainties of production and variability in the harvested species balance. However, little is known about the conditions to favour IV impact and the mechanisms at play.MethodsThe dependency of IV impact on traits holding it and environmental stressors were analysed using a spatially-explicit individual-based model (IBM) of grassland communities. Sixty-three binary mixtures were defined to reflect a gradient of functional divergence between species regarding light and nitrogen (N) acquisition. The growth and dynamics of these communities were simulated for one year with three possible IV levels under two environments contrasting in terms of soil N fertility.Results and discussionThe model predicted a positive impact of moderate and high IV levels on maintaining the species balance over time, but no marked effects on mixture productivity. This stabilising effect increased at higher IV levels and under low soil N fertility. It also tended to be more pronounced in communities with intermediate functional divergence offering a significant overlap between light and N acquisition parameter values of both species. The major traits involved in the plant response to neighbours differed depending on the most contested resource, as indicated by the within-population selection of individuals with favourable N-related parameters under low N and light-related parameters under high N environments. The hypothesis that IV favours a complementarity of resource use between species was not supported. Rather, a greater spatial heterogeneity in competitive interactions was demonstrated, leading to a higher probability of growth and survival for individuals within the subordinate species. These results highlight the potential usefulness of IV to design forage mixtures with improved stability and resilience.
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- 2024
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5. Ion‐Acoustic Waves Associated With Interplanetary Shocks
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J. J. Boldú, D. B. Graham, M. Morooka, M. André, Yu. V. Khotyaintsev, A. Dimmock, D. Píša, J. Souček, M. Maksimovic, P. Louarn, A. Fedorov, G. Nicolaou, and C. Owen
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collisionless shock ,plasma waves ,instabilities ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Abstract Ion‐acoustic waves (IAWs) commonly occur near interplanetary (IP) shocks. These waves are important because of their potential role in the dissipation required for collisionless shocks to exist. We study IAW occurrence statistically at different heliocentric distances using Solar Orbiter to identify the processes responsible for IAW generation near IP shocks. We show that close to IP shocks the occurrence rate of IAW increases and peaks at the ramp. In the upstream region, the IAW activity is highly variable among different shocks and increases with decreasing distance from the Sun. We show that the observed currents near IP shocks are insufficient to reach the threshold for the current‐driven instability. We argue that two‐stream proton distributions and suprathermal electrons are likely sources of the waves.
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- 2024
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6. Electron Beams at Europa
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F. Allegrini, J. Saur, J. R. Szalay, R. W. Ebert, W. S. Kurth, S. Cervantes, H. T. Smith, F. Bagenal, S. J. Bolton, G. Clark, J. E. P. Connerney, P. Louarn, B. Mauk, D. J. McComas, A. Pontoni, Y. Sarkango, P. Valek, and R. J. Wilson
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Europa ,Jupiter's magnetosphere ,electron ,plasma ,Juno ,flyby ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Abstract Jupiter's moon Europa contains a subsurface ocean whose presence is inferred from magnetic field measurements, the interpretation of which depends on knowledge of Europa's local plasma environment. A recent Juno spacecraft flyby returned new observations of plasma electrons with unprecedented resolution. Specifically, powerful magnetic field‐aligned electron beams were discovered near Europa. These beams, with energies from ∼30 to ∼300 eV, locally enhance electron‐impact‐excited emissions and ionization in Europa's atmosphere by more than a factor three over the local space environment, and are associated with large jumps of the magnetic fields. The beams therefore play an essential role in shaping Europa's plasma and magnetic field environment and thus need to be accounted for electromagnetic sounding of Europa's ocean and plume detection by future missions such as JUICE and Europa Clipper.
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- 2024
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7. Connecting Solar Wind Velocity Spikes Measured by Solar Orbiter and Coronal Brightenings Observed by SDO
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Chuanpeng Hou, Alexis P. Rouillard, Jiansen He, Bahaeddine Gannouni, Victor Réville, Philippe Louarn, Andrey Fedorov, Lubomír Přech, Christopher J. Owen, Daniel Verscharen, Raffaella D’Amicis, Luca Sorriso-Valvo, Naïs Fargette, Jesse Coburn, Vincent Génot, Jim M. Raines, Roberto Bruno, Stefano Livi, Benoit Lavraud, Nicolas André, Gabriel Fruit, Rungployphan Kieokaew, Illya Plotnikov, Emmanuel Penou, Alain Barthe, Dhiren Kataria, Matthieu Berthomier, Frederic Allegrini, Vito Fortunato, Gennaro Mele, and Timothy Horbury
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Interplanetary magnetic fields ,Solar wind ,Solar coronal transients ,Supergranulation ,Astrophysics ,QB460-466 - Abstract
The Parker Solar Probe's discovery that magnetic switchbacks and velocity spikes in the young solar wind are abundant has prompted intensive research into their origin(s) and formation mechanism(s) in the solar atmosphere. Recent studies, based on in situ measurements and numerical simulations, argue that velocity spikes are produced through interchange magnetic reconnection. Our work studies the relationship between interplanetary velocity spikes and coronal brightenings induced by changes in the photospheric magnetic field. Our analysis focuses on the characteristic periodicities of velocity spikes detected by the Proton Alpha Sensor on the Solar Orbiter during its fifth perihelion pass. Throughout the time period analyzed here, we estimate their origin along the boundary of a coronal hole. Around the boundary region, we identify periodic variations in coronal brightening activity observed by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. The spectral characteristics of the time series of in situ velocity spikes, remote coronal brightenings, and remote photospheric magnetic flux exhibit correspondence in their periodicities. Therefore, we suggest that the localized small-scale magnetic flux within coronal holes fuels a magnetic reconnection process that can be observed as slight brightness augmentations and outward fluctuations or jets. These dynamic elements may act as mediators, bonding magnetic reconnection with the genesis of velocity spikes and magnetic switchbacks.
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- 2024
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8. Regulus infers signed regulatory relations from few samples' information using discretization and likelihood constraints.
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Marine Louarn, Guillaume Collet, Ève Barré, Thierry Fest, Olivier Dameron, Anne Siegel, and Fabrice Chatonnet
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Biology (General) ,QH301-705.5 - Abstract
MotivationTranscriptional regulation is performed by transcription factors (TF) binding to DNA in context-dependent regulatory regions and determines the activation or inhibition of gene expression. Current methods of transcriptional regulatory circuits inference, based on one or all of TF, regions and genes activity measurements require a large number of samples for ranking the candidate TF-gene regulation relations and rarely predict whether they are activations or inhibitions. We hypothesize that transcriptional regulatory circuits can be inferred from fewer samples by (1) fully integrating information on TF binding, gene expression and regulatory regions accessibility, (2) reducing data complexity and (3) using biology-based likelihood constraints to determine the global consistency between a candidate TF-gene relation and patterns of genes expressions and region activations, as well as qualify regulations as activations or inhibitions.ResultsWe introduce Regulus, a method which computes TF-gene relations from gene expressions, regulatory region activities and TF binding sites data, together with the genomic locations of all entities. After aggregating gene expressions and region activities into patterns, data are integrated into a RDF (Resource Description Framework) endpoint. A dedicated SPARQL (SPARQL Protocol and RDF Query Language) query retrieves all potential relations between expressed TF and genes involving active regulatory regions. These TF-region-gene relations are then filtered using biological likelihood constraints allowing to qualify them as activation or inhibition. Regulus provides signed relations consistent with public databases and, when applied to biological data, identifies both known and potential new regulators. Regulus is devoted to context-specific transcriptional circuits inference in human settings where samples are scarce and cell populations are closely related, using discretization into patterns and likelihood reasoning to decipher the most robust regulatory relations.
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- 2024
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9. Elemental analysis by XRF and HE-PIXE on silver coins from the 16th-17th centuries and on a gilded crucifix from the 12th century
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Gillon, A., Koumeir, C., Meziani, C.-P., Haddad, F., Louarn, G., Metivier, V., Mouchard, Q., Salaün, G., and Servagent, N.
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- 2023
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10. ICARUS: in-situ studies of the solar corona beyond Parker Solar Probe and Solar Orbiter
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Krasnoselskikh, Vladimir, Tsurutani, Bruce T., Dudok de Wit, Thierry, Walker, Simon, Balikhin, Michael, Balat-Pichelin, Marianne, Velli, Marco, Bale, Stuart D., Maksimovic, Milan, Agapitov, Oleksiy, Baumjohann, Wolfgang, Berthomier, Matthieu, Bruno, Roberto, Cranmer, Steven R., de Pontieu, Bart, Meneses, Domingos de Sousa, Eastwood, Jonathan, Erdelyi, Robertus, Ergun, Robert, Fedun, Viktor, Ganushkina, Natalia, Greco, Antonella, Harra, Louise, Henri, Pierre, Horbury, Timothy, Hudson, Hugh, Kasper, Justin, Khotyaintsev, Yuri, Kretzschmar, Matthieu, Krucker, Säm, Kucharek, Harald, Langevin, Yves, Lavraud, Benoît, Lebreton, Jean-Pierre, Lepri, Susan, Liemohn, Michael, Louarn, Philippe, Moebius, Eberhard, Mozer, Forrest, Nemecek, Zdenek, Panasenco, Olga, Retino, Alessandro, Safrankova, Jana, Scudder, Jack, Servidio, Sergio, Sorriso-Valvo, Luca, Souček, Jan, Szabo, Adam, Vaivads, Andris, Vekstein, Grigory, Vörös, Zoltan, Zaqarashvili, Teimuraz, Zimbardo, Gaetano, and Fedorov, Andrei
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- 2022
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11. BepiColombo mission confirms stagnation region of Venus and reveals its large extent
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M. Persson, S. Aizawa, N. André, S. Barabash, Y. Saito, Y. Harada, D. Heyner, S. Orsini, A. Fedorov, C. Mazelle, Y. Futaana, L. Z. Hadid, M. Volwerk, G. Collinson, B. Sanchez-Cano, A. Barthe, E. Penou, S. Yokota, V. Génot, J. A. Sauvaud, D. Delcourt, M. Fraenz, R. Modolo, A. Milillo, H.-U. Auster, I. Richter, J. Z. D. Mieth, P. Louarn, C. J. Owen, T. S. Horbury, K. Asamura, S. Matsuda, H. Nilsson, M. Wieser, T. Alberti, A. Varsani, V. Mangano, A. Mura, H. Lichtenegger, G. Laky, H. Jeszenszky, K. Masunaga, C. Signoles, M. Rojo, and G. Murakami
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Science - Abstract
BepiColombo mission had two Venus flybys on its way to Mercury. Here, the authors show that during its second flyby of Venus BepiColombo has crossed the stagnation region, which was predicted by the models.
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- 2022
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12. Comparative Study of the Kinetic Properties of Proton and Alpha Beams in the Alfvénic Wind Observed by SWA-PAS On Board Solar Orbiter
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Roberto Bruno, Rossana De Marco, Raffaella D’Amicis, Denise Perrone, Maria Federica Marcucci, Daniele Telloni, Raffaele Marino, Luca Sorriso-Valvo, Vito Fortunato, Gennaro Mele, Francesco Monti, Andrei Fedorov, Philippe Louarn, Chris J. Owen, and Stefano Livi
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Fast solar wind ,Alfvén waves ,Plasma physics ,Astronomy data analysis ,Astrophysics ,QB460-466 - Abstract
The problems of heating and acceleration of solar wind particles are of significant and enduring interest in astrophysics. The interactions between waves and particles are crucial in determining the distributions of proton and alpha particles, resulting in non-Maxwellian characteristics, including temperature anisotropies and particle beams. These processes can be better understood as long as the beam can be separated from the core for the two major components of the solar wind. We utilized an alternative numerical approach that leverages the clustering technique employed in machine learning to differentiate the primary populations within the velocity distribution rather than employing the conventional bi-Maxwellian fitting method. Separation of the core and beam revealed new features for protons and alphas. We estimated that the total temperature of the two beams was slightly higher than that of their respective cores, and the temperature anisotropy for the cores and beams was larger than 1. We concluded that the temperature ratio between alphas and protons largely over 4 is due to the presence of a massive alpha beam, which is approximately 50% of the alpha core. We provided evidence that the alpha core and beam populations are sensitive to Alfvénic fluctuations and the surfing effect found in the literature can be recovered only when considering the core and beam as a single population. Several similarities between proton and alpha beams would suggest a common and local generation mechanism not shared with the alpha core, which may not have necessarily been accelerated and heated locally.
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- 2024
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13. Ternary Planar Heterojunction Organic Solar Cells Based on the Ternary Active Layers: α-6T/AlPcCl/C60
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Hajar Ftouhi, Hind Lamkaouane, Mustapha Diani, Guy Louarn, Ludovic Arzel, Jean-Christian Bernède, Mohammed Addou, and Linda Cattin
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organic photovoltaic cells ,ambipolar organic layer ,aluminum phthalocyanine chloride ,alpha-sexithiophene ,Production of electric energy or power. Powerplants. Central stations ,TK1001-1841 - Abstract
Ternary planar heterojunction organic solar cells (PHJ-OPVs) were fabricated using three organic small molecules, alpha-sexithiophene (α-6T), aluminum phthalocyanine chloride (AlPcCl) and fullerene (C60). These molecules can be easily sublimated under a vacuum; they have complementary optical absorption spectra and their energy band structure alignment is favorable for electronic charge transfers. Moreover, α-6T and AlPcCl have almost the same HOMO, which is desirable to avoid any decrease in open circuit voltage. The AlPcCl intercalated layer bridges the energy levels of the electron donor, α-6T, and the electron acceptor, C60, which facilitates charge transport through the energy cascade effect. Moreover, the charge carrier mobility measurements of AlPcCl, using the space charge limited current method, demonstrated that it iss ambipolar. All these properties combine to improve the power conversion efficiency (PCE) of PHJ-OPVs by moving from binary structures (α-6T/C60, α-6T/AlPcCl and AlPcCl/C60) to ternary ones (α-6T/AlPcCl/C60). We show, in this study, that both interfaces of the ternary PHJ-OPVs are efficient for carrier separation. After optimization of the different layer thickness, we show that, by comparing the optimum efficiencies of the binary PHJ-OPVs, the realization of ternary PHJ-OPVs, based on the active layers α-6T/AlPcCl/C60, using the following optimized method, allows us to achieve a PCE of 4.33%.
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- 2022
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14. Evidence for Non‐Monotonic and Broadband Electron Distributions in the Europa Footprint Tail Revealed by Juno In Situ Measurements
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J. Rabia, V. Hue, J. R. Szalay, N. André, Q. Nénon, M. Blanc, F. Allegrini, S. J. Bolton, J. E. P. Connerney, R. W. Ebert, G. R. Gladstone, T. K. Greathouse, P. Louarn, A. Mura, E. Penou, and A. H. Sulaiman
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Geophysics. Cosmic physics ,QC801-809 - Abstract
Abstract We characterize the precipitating electrons accelerated in the Europa‐magnetosphere interaction by analyzing in situ measurements and remote sensing observations recorded during 10 crossings of the flux tubes connected to Europa's auroral footprint tail by Juno. The electron downward energy flux, ranging from 34 to 0.8 mW/m2, exhibits an exponential decay as a function of downtail distance, with an e‐folding factor of 7.4°. Electrons are accelerated at energies between 0.3 and 25 keV, with a characteristic energy that decreases downtail. The electron distributions form non‐monotonic spectra in the near tail (i.e., within an angular separation of less than 4°) that become broadband in the far tail. The size of the interaction region at the equator is estimated to be 4.2 ± 0.9 Europa radii, consistent with previous estimates based on theory and UV observations.
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- 2023
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15. LatHyS global hybrid simulation of the BepiColombo second Venus flyby
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Aizawa, S., Persson, M., Menez, T., André, N., Modolo, R., Génot, V., Sanchez-Cano, B., Volwerk, M., Chaufray, J.-Y., Baskevitch, C., Heyner, D., Saito, Y., Harada, Y., Leblanc, F., Barthe, A., Penou, E., Fedorov, A., Sauvaud, J.-A., Yokota, S., Auster, U., Richter, I., Mieth, J., Horbury, T.S., Louarn, P., Owen, C.J., and Murakami, G.
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- 2022
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16. Testing the flux tube expansion factor: Solar wind speed relation with Solar Orbiter data.
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Dakeyo, J.-B., Rouillard, A. P., Réville, V., Démoulin, P., Maksimovic, M., Chapiron, A., Pinto, R. F., and Louarn, P.
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SOLAR magnetic fields ,MAGNETIC fields in the solar corona ,ROTATION of the Sun ,SOLAR corona ,SOLAR activity ,SOLAR wind ,SOLAR atmosphere - Abstract
Context. The properties of the solar wind measured in situ in the heliosphere are largely controlled by energy deposition in the solar corona, which is in turn closely related to the properties of the coronal magnetic field. Previous studies have shown that long-duration and large-scale magnetic structures show an inverse relation between the solar wind velocity measured in situ near 1 au and the expansion factor of the magnetic flux tubes in the solar atmosphere. Aims. The advent of the Solar Orbiter mission offers a new opportunity to analyse the relation between solar wind properties measured in situ in the inner heliosphere and the coronal magnetic field. We exploit this new data in conjunction with models of the coronal magnetic field and the solar wind to evaluate the flux expansion factor and speed relation. Methods. We use a Parker-like solar wind model, the "isopoly" model presented in previous works, to describe the motion of the solar wind plasma in the radial direction and model the tangential plasma motion due to solar rotation with the Weber and Davis equations. Both radial and tangential velocities are used to compute the plasma trajectory and streamline from Solar Orbiter location sunward to the solar 'source surface' at r
ss . We then employed a potential field source surface (PFSS) model to reconstruct the coronal magnetic field below rss to connect wind parcels mapped back to the photosphere. Results. We found a statistically weak anti-correlation between the in situ bulk velocity and the coronal expansion factor, for about 1.5 years of solar data. Classification of the data by source latitude reveals different levels of anticorrelation, which is typically higher when Solar Orbiter magnetically connects to high latitude structures than when it connects to low latitude structures. We show the existence of a fast solar wind that originates in strong magnetic field regions at low latitudes and undergoes large expansion factor. We provide evidence that such winds become supersonic during the super-radial expansion (below rss ) and are theoretically governed by a positive v–f correlation. We find that faster winds exhibit, on average, a flux tube expansion at a larger radius than slower winds. Conclusions. An anticorrelation between solar wind speed and expansion factor is present for solar winds originating in high latitude structures in solar minimum activity, typically associated with coronal hole-like structures, but this cannot be generalized to lower latitude sources. We have found extended time intervals of fast solar wind associated with both large expansion factors and strong photospheric magnetic fields. Therefore, the value of the expansion factor alone cannot be used to predict the solar wind speed. Other parameters, such as the height at which the expansion gradient is the strongest, must also be taken into account. [ABSTRACT FROM AUTHOR]- Published
- 2024
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17. Dispersal-based species pools as sources of connectivity area mismatches
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Préau, Clémentine, Dubos, Nicolas, Lenormand, Maxime, Denelle, Pierre, Le Louarn, Marine, Alleaume, Samuel, and Luque, Sandra
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- 2022
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18. Improving reusability along the data life cycle: a regulatory circuits case study
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Marine Louarn, Fabrice Chatonnet, Xavier Garnier, Thierry Fest, Anne Siegel, Catherine Faron, and Olivier Dameron
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Dataset architecture ,Bioinformatics ,RDF named graphs ,SPARQL ,Reusability ,Linked Open Data ,Computer applications to medicine. Medical informatics ,R858-859.7 - Abstract
Abstract Background In life sciences, there has been a long-standing effort of standardization and integration of reference datasets and databases. Despite these efforts, many studies data are provided using specific and non-standard formats. This hampers the capacity to reuse the studies data in other pipelines, the capacity to reuse the pipelines results in other studies, and the capacity to enrich the data with additional information. The Regulatory Circuits project is one of the largest efforts for integrating human cell genomics data to predict tissue-specific transcription factor-genes interaction networks. In spite of its success, it exhibits the usual shortcomings limiting its update, its reuse (as a whole or partially), and its extension with new data samples. To address these limitations, the resource has previously been integrated in an RDF triplestore so that TF-gene interaction networks could be generated with two SPARQL queries. However, this triplestore did not store the computed networks and did not integrate metadata about tissues and samples, therefore limiting the reuse of this dataset. In particular, it does not enable to reuse only a portion of Regulatory Circuits if a study focuses on a subset of the tissues, nor to combine the samples described in the datasets with samples from other studies. Overall, these limitations advocate for the design of a complete, flexible and reusable representation of the Regulatory Circuits dataset based on Semantic Web technologies. Results We provide a modular RDF representation of the Regulatory Circuits, called Linked Extended Regulatory Circuits (LERC). It consists in (i) descriptions of biological and experimental context mapped to the references databases, (ii) annotations about TF-gene interactions at the sample level for 808 samples, (iii) annotations about TF-gene interactions at the tissue level for 394 tissues, (iv) metadata connecting the knowledge graphs cited above. LERC is based on a modular organisation into 1,205 RDF named graphs for representing the biological data, the sample-specific and the tissue-specific networks, and the corresponding metadata. In total it contains 3,910,794,050 triples and is available as a SPARQL endpoint. Conclusion The flexible and modular architecture of LERC supports biologically-relevant SPARQL queries. It allows an easy and fast querying of the resources related to the initial Regulatory Circuits datasets and facilitates its reuse in other studies. Associated website https://regulatorycircuits-lod.genouest.org
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- 2022
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19. Ten (not so) simple rules for clinical trial data-sharing
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Claude Pellen, Anne Le Louarn, Gilliosa Spurrier-Bernard, Evelyne Decullier, Jean-Marie Chrétien, Eric Rosenthal, Gérard Le Goff, David Moher, John P. A. Ioannidis, and Florian Naudet
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Biology (General) ,QH301-705.5 - Abstract
Clinical trial data-sharing is seen as an imperative for research integrity and is becoming increasingly encouraged or even required by funders, journals, and other stakeholders. However, early experiences with data-sharing have been disappointing because they are not always conducted properly. Health data is indeed sensitive and not always easy to share in a responsible way. We propose 10 rules for researchers wishing to share their data. These rules cover the majority of elements to be considered in order to start the commendable process of clinical trial data-sharing: Rule 1: Abide by local legal and regulatory data protection requirements Rule 2: Anticipate the possibility of clinical trial data-sharing before obtaining funding Rule 3: Declare your intent to share data in the registration step Rule 4: Involve research participants Rule 5: Determine the method of data access Rule 6: Remember there are several other elements to share Rule 7: Do not proceed alone Rule 8: Deploy optimal data management to ensure that the data shared is useful Rule 9: Minimize risks Rule 10: Strive for excellence.
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- 2023
20. Kinetic Features of Alpha Particles in a Pestchek-like Magnetic Reconnection Event in the Solar Wind Observed by Solar Orbiter
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Die Duan, Jiansen He, Xingyu Zhu, Rui Zhuo, Ziqi Wu, Georgios Nicolaou, Jia Huang, Daniel Verscharen, Liu Yang, Christopher J. Owen, Andrey Fedorov, Philippe Louarn, and Timothy S. Horbury
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Solar wind ,Solar magnetic reconnection ,Heliosphere ,Astrophysics ,QB460-466 - Abstract
The acceleration and heating of solar wind particles by magnetic reconnection are important mechanisms in space physics. Although alpha particles ( ^4 He ^2+ ) are the second most abundant population of solar wind ions, their kinetic behavior in solar wind magnetic reconnection is not well understood. Using the high-energy (1500–3000 eV) range of the Solar Wind Analyser/Proton–Alpha Sensor instrument on board Solar Orbiter, we study the kinetic features of alpha particles in an exhaust region of a Pestchek-like solar-wind reconnection event with a weak guide field. A pair of back-to-back compound discontinuities is observed in the exhaust region. We find that the plasma in the magnetic exhaust region is heated and bounded by slow shocks (SSs), while the accelerated reconnection jet is bounded by rotational discontinuities (RDs). The SSs are outside the RDs, which is not expected from the magnetohydrodynamical prediction. We suggest this different location of the discontinuities is due to the enhanced parallel temperature T _p _∥ > T _p _⊥ , which reduces the local Alfvén speed in the exhaust region, allowing the SSs to propagate faster than the RDs. Inside the exhaust region, the guide field is dominant. We find a two-population distribution of the alpha particles. These two populations are field aligned downstream the SSs and shift to have a perpendicular offset in the reconnection jet, suggesting that the change of the magnetic field at the RDs has similar timescales with the proton gyroperiod, but faster than those of the alpha particles, such that the alpha particles behave like pickup ions.
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- 2023
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21. Magnetic Field Spectral Evolution in the Inner Heliosphere
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Nikos Sioulas, Zesen Huang, Chen Shi, Marco Velli, Anna Tenerani, Trevor A. Bowen, Stuart D. Bale, Jia Huang, Loukas Vlahos, L. D. Woodham, T. S. Horbury, Thierry Dudok de Wit, Davin Larson, Justin Kasper, Christopher J. Owen, Michael L. Stevens, Anthony Case, Marc Pulupa, David M. Malaspina, J. W. Bonnell, Roberto Livi, Keith Goetz, Peter R. Harvey, Robert J. MacDowall, Milan Maksimović, P. Louarn, and A. Fedorov
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Solar wind ,Magnetohydrodynamics ,Interplanetary turbulence ,Space plasmas ,Plasma astrophysics ,Astrophysics ,QB460-466 - Abstract
Parker Solar Probe and Solar Orbiter data are used to investigate the radial evolution of magnetic turbulence between 0.06 ≲ R ≲ 1 au. The spectrum is studied as a function of scale, normalized to the ion inertial scale d _i . In the vicinity of the Sun, the inertial range is limited to a narrow range of scales and exhibits a power-law exponent of, α _B = −3/2, independent of plasma parameters. The inertial range grows with distance, progressively extending to larger spatial scales, while steepening toward a α _B = −5/3 scaling. It is observed that spectra for intervals with large magnetic energy excesses and low Alfvénic content steepen significantly with distance, in contrast to highly Alfvénic intervals that retain their near-Sun scaling. The occurrence of steeper spectra in slower wind streams may be attributed to the observed positive correlation between solar wind speed and Alfvénicity.
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- 2023
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22. Association mapping for broomrape resistance in sunflower
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Álvaro Calderón-González, Begoña Pérez-Vich, Nicolas Pouilly, Marie-Claude Boniface, Johann Louarn, Leonardo Velasco, and Stéphane Muños
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broomrape resistance ,genome-wide association mapping (GWAS) ,candidate genes ,Orobanche cumana ,parasitic plants ,Plant culture ,SB1-1110 - Abstract
IntroductionSunflower breeding for resistance to the parasitic plant sunflower broomrape (Orobanche cumana Wallr.) requires the identification of novel resistance genes. In this research, we conducted a genome-wide association study (GWAS) to identify QTLs associated with broomrape resistance.MethodsThe marker-trait associations were examined across a germplasm set composed of 104 sunflower accessions. They were genotyped with a 600k AXIOM® genome-wide array and evaluated for resistance to three populations of the parasite with varying levels of virulence (races EFR, FGV, and GTK) in two environments.Results and DiscussionThe analysis of the genetic structure of the germplasm set revealed the presence of two main groups. The application of optimized treatments based on the general linear model (GLM) and the mixed linear model (MLM) allowed the detection of 14 SNP markers significantly associated with broomrape resistance. The highest number of marker-trait associations were identified on chromosome 3, clustered in two different genomic regions of this chromosome. Other associations were identified on chromosomes 5, 10, 13, and 16. Candidate genes for the main genomic regions associated with broomrape resistance were studied and discussed. Particularly, two significant SNPs on chromosome 3 associated with races EFR and FGV were found at two tightly linked SWEET sugar transporter genes. The results of this study have confirmed the role of some QTL on resistance to sunflower broomrape and have revealed new ones that may play an important role in the development of durable resistance to this parasitic weed in sunflower.
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- 2023
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23. Improving reusability along the data life cycle: a regulatory circuits case study
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Louarn, Marine, Chatonnet, Fabrice, Garnier, Xavier, Fest, Thierry, Siegel, Anne, Faron, Catherine, and Dameron, Olivier
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- 2022
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24. BepiColombo mission confirms stagnation region of Venus and reveals its large extent
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Persson, M., Aizawa, S., André, N., Barabash, S., Saito, Y., Harada, Y., Heyner, D., Orsini, S., Fedorov, A., Mazelle, C., Futaana, Y., Hadid, L. Z., Volwerk, M., Collinson, G., Sanchez-Cano, B., Barthe, A., Penou, E., Yokota, S., Génot, V., Sauvaud, J. A., Delcourt, D., Fraenz, M., Modolo, R., Milillo, A., Auster, H.-U., Richter, I., Mieth, J. Z. D., Louarn, P., Owen, C. J., Horbury, T. S., Asamura, K., Matsuda, S., Nilsson, H., Wieser, M., Alberti, T., Varsani, A., Mangano, V., Mura, A., Lichtenegger, H., Laky, G., Jeszenszky, H., Masunaga, K., Signoles, C., Rojo, M., and Murakami, G.
- Published
- 2022
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25. Investigation of aluminum phthalocyanine chloride as acceptor material in planar organic solar cells: comparative study with fullerene
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Ftouhi, Hajar, Lamkaouane, Hind, Louarn, Guy, Diani, Mustapha, Bernède, Jean-Christian, Addou, Mohammed, and Cattin, Linda
- Published
- 2021
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26. Assessing the effect of sample bias correction in species distribution models
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Nicolas Dubos, Clémentine Préau, Maxime Lenormand, Guillaume Papuga, Sophie Monsarrat, Pierre Denelle, Marine Le Louarn, Stien Heremans, Roel May, Philip Roche, and Sandra Luque
- Subjects
Accessibility maps ,Cross-validation ,Performance metrics ,Overlap ,Pseudo-absence selection ,Terrestrial vertebrates ,Ecology ,QH540-549.5 - Abstract
1. Open-source biodiversity databases contain a large number of species occurrence records but are often spatially biased; which affects the reliability of species distribution models based on these records. Sample bias correction techniques require data filtering which comes at the cost of record numbers, or require considerable additional sampling effort. Since independent data is rarely available, assessment of the correction technique often relies solely on performance metrics computed using subsets of the available – biased – data, which may prove misleading.2. Here, we assess the extent to which an acknowledged sample bias correction technique is likely to improve models’ ability to predict species distributions in the absence of independent data. We assessed variation in model predictions induced by the aforementioned correction and model stochasticity; the variability between model replicates related to a random component (pseudo-absences sets and cross-validation subsets). We present, then, an index of the effect of correction relative to model stochasticity; the Relative Overlap Index (ROI). We investigated whether the ROI better represented the effect of correction than classic performance metrics (Boyce index, cAUC, AUC and TSS) and absolute overlap metrics (Schoener’s D, Pearson’s and Spearman’s correlation coefficients) when considering data related to 64 vertebrate species and 21 virtual species with a generated sample bias.3. When based on absolute overlaps and cross-validation performance metrics, we found that correction produced no significant effects. When considering its effect relative to model stochasticity, the effect of correction was strong for most species at one of the three sites. The use of virtual species enabled us to verify that the correction technique improved both distribution predictions and the biological relevance of the selected variables at the specific site, when these were not correlated with sample bias patterns.4. In the absence of additional independent data, the assessment of sample bias correction based on subsample data may be misleading. We propose to investigate both the biological relevance of environmental variables selected, and, the effect of sample bias correction based on its effect relative to model stochasticity.
- Published
- 2022
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27. THE 4C APPROACH AS A WAY TO UNDERSTAND SPECIES INTERACTIONS DETERMINING INTERCROPPING PRODUCTIVITY
- Author
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Eric JUSTES, Laurent BEDOUSSAC, Christos DORDAS, Ela FRAK, Gaetan LOUARN, Simon BOUDSOCQ, Etienne-Pascal JOURNET, Anastasios LITHOURGIDIS, Chrysanthi PANKOU, Chaochun ZHANG, Georg CARLSSON, Erik Steen JENSEN, Christine WATSON, Long LI
- Subjects
compensation ,competition ,complementarity ,cooperation ,interspecific interactions ,land equivalent ratio ,light ,nutrients ,species mixtures ,water ,Agriculture (General) ,S1-972 - Abstract
● The 4C approach considers intercropping performances as the result of joint 4C effects. ● Partial land equivalent ratios indicate which effect(s) are the major one(s). ● A major effect of complementarity is related to a better capture of abiotic resources. Modern agriculture needs to develop transition pathways toward agroecological, resilient and sustainable farming systems. One key pathway for such agroecological intensification is the diversification of cropping systems using intercropping and notably cereal-grain legume mixtures. Such mixtures or intercrops have the potential to increase and stabilize yields and improve cereal grain protein concentration in comparison to sole crops. Species mixtures are complex and the 4C approach is both a pedagogical and scientific way to represent the combination of four joint effects of Competition, Complementarity, Cooperation, and Compensation as processes or effects occurring simultaneously and dynamically between species over the whole cropping cycle. Competition is when plants have fairly similar requirements for abiotic resources in space and time, the result of all processes that occur when one species has a greater ability to use limiting resources (e.g., nutrients, water, space, light) than others. Complementarity is when plants grown together have different requirements for abiotic resources in space, time or form. Cooperation is when the modification of the environment by one species is beneficial to the other(s). Compensation is when the failure of one species is compensated by the other(s) because they differ in their sensitivity to abiotic stress. The 4C approach allows to assess the performance of arable intercropping versus classical sole cropping through understanding the use of abiotic resources.
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- 2021
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28. Analysis of Dibenzyltoluene Mixtures: From Fast Analysis to In-Depth Characterization of the Compounds
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Xiaolong Ji, Essyllt Louarn, Fabienne Fache, Laurent Vanoye, Anne Bonhommé, Isabelle Pitault, and Valérie Meille
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LOHC ,DBT ,analysis ,GC–MS ,isomers ,synthesis ,Organic chemistry ,QD241-441 - Abstract
The so-called dibenzyltoluene (H0-DBT) heat transfer oil contains numerous isomers of dibenzyltoluene as well as (benzyl)benzyltoluene (methyl group on the central vs. the side aromatic ring). As it is used as a liquid organic hydrogen carrier (LOHC), a detailed analysis of its composition is crucial in assessing the kinetic rate of hydrogenation for each constituent and studying the mechanism of H0-DBT hydrogenation. To identify all of the compounds in the oil, an in-depth analysis of the GC–MS spectra was performed. To confirm peak attribution, we synthesized some DBTs and characterized the pure compounds using NMR and Raman spectroscopies. Moreover, a fast-GC analysis was developed to rapidly determine the degree of hydrogenation of the mixture.
- Published
- 2023
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29. Ion‐Acoustic Waves Associated With Interplanetary Shocks.
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Boldú, J. J., Graham, D. B., Morooka, M., André, M., Khotyaintsev, Yu. V., Dimmock, A., Píša, D., Souček, J., Maksimovic, M., Louarn, P., Fedorov, A., Nicolaou, G., and Owen, C.
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ELECTRON distribution ,PLASMA waves ,ELECTRIC currents ,PLASMA instabilities ,THERMODYNAMIC equilibrium - Abstract
Ion‐acoustic waves (IAWs) commonly occur near interplanetary (IP) shocks. These waves are important because of their potential role in the dissipation required for collisionless shocks to exist. We study IAW occurrence statistically at different heliocentric distances using Solar Orbiter to identify the processes responsible for IAW generation near IP shocks. We show that close to IP shocks the occurrence rate of IAW increases and peaks at the ramp. In the upstream region, the IAW activity is highly variable among different shocks and increases with decreasing distance from the Sun. We show that the observed currents near IP shocks are insufficient to reach the threshold for the current‐driven instability. We argue that two‐stream proton distributions and suprathermal electrons are likely sources of the waves. Plain Language Summary: Ion‐acoustic waves (IAWs) are fluctuations in the electric field that occur at frequencies close to the ion plasma frequency. These waves are commonly found in the solar wind and often cluster around interplanetary (IP) shock waves. In this study, we investigate and quantify how common IAWs are in the vicinity of IP shocks. Our research revealed that IAW activity is enhanced before and after most IP shock passages. Furthermore, IAWs are more likely to be observed preceding IP shocks that are closer to the Sun. We find that the occurrence rate of IAWs shows no clear dependence on the IP shock parameters. We explore the possible mechanisms that could explain the presence of these IAWs. For instance, IAW modes can be excited by electric currents if the associated drift velocity between ions and electrons is above a certain threshold. However, the currents alone are not strong enough to generate the IAWs found near IP shocks. We discuss other potential generation mechanisms, such as velocity distributions of ions and electrons deviating from thermodynamic equilibrium. Key Points: The occurrence of Ion‐acoustic waves (IAWs) is enhanced at interplanetary (IP) shocks, peaking at the shock rampThe occurrence rate of IAWs in the upstream region of IP shocks increases with decreasing radial distance from the SunIAWs are observed upstream of an IP shock together with two‐stream protons and an electron strahl [ABSTRACT FROM AUTHOR]
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- 2024
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30. Electron Beams at Europa.
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Allegrini, F., Saur, J., Szalay, J. R., Ebert, R. W., Kurth, W. S., Cervantes, S., Smith, H. T., Bagenal, F., Bolton, S. J., Clark, G., Connerney, J. E. P., Louarn, P., Mauk, B., McComas, D. J., Pontoni, A., Sarkango, Y., Valek, P., and Wilson, R. J.
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ELECTRON beams ,EUROPA (Satellite) ,MAGNETIC field measurements ,SPACE environment ,JUNO (Space probe) ,ELECTROMAGNETIC induction - Abstract
Jupiter's moon Europa contains a subsurface ocean whose presence is inferred from magnetic field measurements, the interpretation of which depends on knowledge of Europa's local plasma environment. A recent Juno spacecraft flyby returned new observations of plasma electrons with unprecedented resolution. Specifically, powerful magnetic field‐aligned electron beams were discovered near Europa. These beams, with energies from ∼30 to ∼300 eV, locally enhance electron‐impact‐excited emissions and ionization in Europa's atmosphere by more than a factor three over the local space environment, and are associated with large jumps of the magnetic fields. The beams therefore play an essential role in shaping Europa's plasma and magnetic field environment and thus need to be accounted for electromagnetic sounding of Europa's ocean and plume detection by future missions such as JUICE and Europa Clipper. Plain Language Summary: A recent Juno spacecraft close flyby of Jupiter's moon Europa revealed the presence of powerful electrons beams. Based on previous observations and modeling of electron beams at the moon Io, such beams were not expected to be observed so close to Europa. Overall, the proximity of the beams to Europa indicates that the acceleration of these electrons takes place much closer to Europa than anticipated and that these beams, therefore, stem from a new and previously unknown acceleration mechanism. The beams are predicted to have an outsized influence on the ionization of the constituents of Europa's tenuous atmosphere and are accompanied with large magnetic field perturbations. Hence, these electron beams are an important ionization source that modify the moon's ionosphere, the electric current systems, and the magnetic field environment. In particular, the presence of electron beams will affect plasma conditions that are used to infer the extent of a subsurface ocean via the magnetic induction signal. These beams significantly impact the space plasma environment around Europa which needs to be accounted for by future missions such as ESA's (European Space Agency) JUICE (Jupiter Icy Moons Explorer) and NASA's (National Aeronautics and Space Administration) Europa Clipper mission. Key Points: Powerful electron beams that significantly shape Europa's space environment are discovered during a Juno flybyThe beams enhance electron‐impact‐excited emissions in Europa's atmosphere and are associated with large jumps of the magnetic fieldsThe beams' proximity to Europa and their pitch angle distribution constrain the source acceleration to be near or within the plasma disk [ABSTRACT FROM AUTHOR]
- Published
- 2024
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31. Power Conversion Efficiency Improvement of Planar Organic Photovoltaic Cells Using an Original Hybrid Electron-Transporting Layer
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Linda Cattin, Guy Louarn, Ludovic Arzel, Nicolas Stephant, Mustapha Morsli, and Jean Christian Bernède
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Chemistry ,QD1-999 - Published
- 2021
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32. Non-field-aligned Proton Beams and Their Roles in the Growth of Fast Magnetosonic/Whistler Waves: Solar Orbiter Observations
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Xingyu Zhu, Jiansen He, Die Duan, Daniel Verscharen, Christopher J. Owen, Andrey Fedorov, Philippe Louarn, and Timothy S. Horbury
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Solar wind ,Heliosphere ,Astrophysics ,QB460-466 - Abstract
The proton beam is an important population of the non-Maxwellian proton velocity distribution in the solar wind, but its role in wave activity remains unclear. In particular, the velocity vector of the proton beam and its influence on wave growth/damping have not been addressed before. Here we explore the origin and the associated particle dynamics of a kinetic wave event in the solar wind by analyzing measurements from Solar Orbiter and comparing them with theoretical predictions from linear Vlasov theory. We identify the waves as outward-propagating circularly polarized fast magnetosonic/whistler (FM/W) waves. The proton’s velocity distribution functions can destabilize FM/W waves. According to linear Vlasov theory, the velocity fluctuations of the core and the beam associated with FM/W waves render the original field-aligned background drift velocity non-field-aligned. This non-field-aligned drift velocity carrying the information of the velocity fluctuations of the core and the beam is responsible for the wave growth/damping. Specifically, for the FM/W waves we analyze, the non-field-aligned fluctuating velocity of the beam population is responsible for the growth of these unstable waves in the presence of a proton beam. In contrast, the core population plays the opposite role, partially suppressing the wave growth. Remarkably, the observed drift velocity vector between the core and the beam is not field aligned during an entire wave period. This result contrasts the traditional expectation that the proton beam is field aligned.
- Published
- 2023
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33. Ion Energization and Thermalization in Magnetic Reconnection Exhaust Region in the Solar Wind
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Ziqi Wu, Jiansen He, Die Duan, Xingyu Zhu, Chuanpeng Hou, Daniel Verscharen, Georgios Nicolaou, Christopher J. Owen, Andrey Fedorov, and Philippe Louarn
- Subjects
Heliosphere ,Solar magnetic reconnection ,Solar wind ,Astrophysics ,QB460-466 - Abstract
Plasma energization and thermalization in magnetic reconnection is an important topic in astrophysical studies. We select two magnetic reconnection exhausts encountered by Solar Orbiter and analyze the associated ion heating in the kinetic regime. Both cases feature asymmetric plasma merging in the exhaust and anisotropic heating. For a quantitative investigation of the associated complex velocity-space structures, we adopt a three-dimensional Hermite representation of the proton velocity distribution function to produce the distribution of Hermite moments. We also derive the enstrophy and Hermite spectra to analyze the free energy conversion and transfer in phase space. We find a depletion of Hermite power at small m (corresponding to large-scale structures in velocity space) inside the reconnection exhaust region, concurrent with enhanced proton temperature and decreased enstrophy. Furthermore, the slopes of the 1D time-averaged parallel Hermite spectra are lower inside the exhaust and consistent with the effect of phase mixing that creates small fluctuations in velocity space. These fluctuations store free energy at higher m and are smoothed by weak collisionality, leading to irreversible thermalization. We also suggest that the perpendicular heating may happen via perpendicular phase mixing resulting from finite Larmor radius effects around the exhaust boundary.
- Published
- 2023
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34. Slow Solar Wind Connection Science during Solar Orbiter’s First Close Perihelion Passage
- Author
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Stephanie L. Yardley, Christopher J. Owen, David M. Long, Deborah Baker, David H. Brooks, Vanessa Polito, Lucie M. Green, Sarah Matthews, Mathew Owens, Mike Lockwood, David Stansby, Alexander W. James, Gherardo Valori, Alessandra Giunta, Miho Janvier, Nawin Ngampoopun, Teodora Mihailescu, Andy S. H. To, Lidia van Driel-Gesztelyi, Pascal Démoulin, Raffaella D’Amicis, Ryan J. French, Gabriel H. H. Suen, Alexis P. Rouillard, Rui F. Pinto, Victor Réville, Christopher J. Watson, Andrew P. Walsh, Anik De Groof, David R. Williams, Ioannis Zouganelis, Daniel Müller, David Berghmans, Frédéric Auchère, Louise Harra, Udo Schuehle, Krysztof Barczynski, Éric Buchlin, Regina Aznar Cuadrado, Emil Kraaikamp, Sudip Mandal, Susanna Parenti, Hardi Peter, Luciano Rodriguez, Conrad Schwanitz, Phil Smith, Luca Teriaca, Cis Verbeeck, Andrei N. Zhukov, Bart De Pontieu, Tim Horbury, Sami K. Solanki, Jose Carlos del Toro Iniesta, Joachim Woch, Achim Gandorfer, Johann Hirzberger, David Orozco Súarez, Thierry Appourchaux, Daniele Calchetti, Jonas Sinjan, Fatima Kahil, Kinga Albert, Reiner Volkmer, Mats Carlsson, Andrzej Fludra, Don Hassler, Martin Caldwell, Terje Fredvik, Tim Grundy, Steve Guest, Margit Haberreiter, Sarah Leeks, Gabriel Pelouze, Joseph Plowman, Werner Schmutz, Sunil Sidher, William T. Thompson, Philippe Louarn, and Andrei Federov
- Subjects
Solar physics ,Slow solar wind ,Solar wind ,Solar active regions ,Astrophysics ,QB460-466 - Abstract
The Slow Solar Wind Connection Solar Orbiter Observing Plan (Slow Wind SOOP) was developed to utilize the extensive suite of remote-sensing and in situ instruments on board the ESA/NASA Solar Orbiter mission to answer significant outstanding questions regarding the origin and formation of the slow solar wind. The Slow Wind SOOP was designed to link remote-sensing and in situ measurements of slow wind originating at open–closed magnetic field boundaries. The SOOP ran just prior to Solar Orbiter’s first close perihelion passage during two remote-sensing windows (RSW1 and RSW2) between 2022 March 3–6 and 2022 March 17–22, while Solar Orbiter was at respective heliocentric distances of 0.55–0.51 and 0.38–0.34 au from the Sun. Coordinated observation campaigns were also conducted by Hinode and IRIS. The magnetic connectivity tool was used, along with low-latency in situ data and full-disk remote-sensing observations, to guide the target pointing of Solar Orbiter. Solar Orbiter targeted an active region complex during RSW1, the boundary of a coronal hole, and the periphery of a decayed active region during RSW2. Postobservation analysis using the magnetic connectivity tool, along with in situ measurements from MAG and SWA/PAS, showed that slow solar wind originating from two out of three of the target regions arrived at the spacecraft with velocities between ∼210 and 600 km s ^−1 . The Slow Wind SOOP, despite presenting many challenges, was very successful, providing a blueprint for planning future observation campaigns that rely on the magnetic connectivity of Solar Orbiter.
- Published
- 2023
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- View/download PDF
35. On the use of multiple stacked active layers in organic photovoltaic cells
- Author
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Cattin, L., El Jouad, Z., Siad, M. B., Morsli, M., Arzel, L., Ortega, E., Louarn, G., Neculqueo, G., Lamkaouane, H., Khelil, A., Addou, M., del Valle, M. A., Mir, F., and Bernède, J. C.
- Published
- 2020
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- View/download PDF
36. Lovebirds in the air: trade patterns, establishment success and niche shifts of Agapornis parrots within their non-native range
- Author
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Mori, Emiliano, Cardador, Laura, Reino, Luís, White, Rachel L., Hernández-Brito, Dailos, Le Louarn, Marine, Mentil, Lorenzo, Edelaar, Pim, Pârâu, Liviu G., Nikolov, Boris P., and Menchetti, Mattia
- Published
- 2020
- Full Text
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37. Effects of reconstruction layer profiles on atmospheric tomography in E-ELT AO systems
- Author
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Saxennhuber, Daniela, Auzinger, Gunter, Le Louarn, Miska, and Obereder, Andreas
- Subjects
compression algorithm ,atmospheric tomography ,reconstruction algorithm - Abstract
In this paper, we will present new compression algorithms to determine optimal layer heights and turbulenceweights for the tomographic reconstruction in wide field AO systems. Among other approaches, a new compressionmethod based on discrete optimization of collecting atmospheric layers to subgroups is discussed. Furthermore,studies of the influence of layer heights and c2n-profiles on the reconstruction quality for differentreconstruction algorithms and atmospheric profiles will be shown. Our comparison suggests that reconstructionson fewer atmospheric layers yield comparable quality with lower computational effort, if an appropriatecompression algorithm is used. The numerical results were obtained on the ESO end-to-end simulation toolOCTOPUS.
- Published
- 2015
38. Low Wind Effect, the main limitation of the SPHERE instrument
- Author
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Sauvage, Jean-François, Fusco, Thierry, Guesalaga, Andres, Wizinowitch, Peter, O'Neal, Jared, N'Diaye, Mamadou, Vigan, Arthur, Grard, Julien, Lesur, Geoffroy, Mouillet, David, Beuzit, Jean-Luc, Kasper, Markus, Le Louarn, Miska, Milli, Julien, Dohlen, Kjetil, Neichel, Benoit, Bourget, Pierre, Heigenauer, Pierre, and Mawet, Dimitri
- Subjects
extreme adaptive optics ,high contrast imaging ,dome seeing - Abstract
The SPHERE instrument (Beuzit, et al., 2010) is dedicated to the direct imaging of extra-solar planets. This kind of observation allows one to study the photons emitted by the planet’s atmosphere itself, or reflected by its surface. The search for bio-markers is therefore made possible. The SPHERE instrument has been installed and commissioned at VLT Paranal Observatory during 2014 and now routinely delivers high contrast images to the exoplanet community. This paper presents a study of the main actual limitation of the SPHERE instrument, as known as the Low Wind Effect [LWE]. This effect has been discovered on SPHERE during commissioning period. Its effect is a strong degradation of the instrument PSF, preventing instrument to perform high contrast imaging. It happens during particularly low wind conditions (below 1m/s at the telescope level) which happens one night out of five.
- Published
- 2015
39. Simulations of AO for the E-ELT and its instruments
- Author
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Le Louarn, Miska
- Subjects
Adaptive Optics ,Extremely Large Telescopes ,Wavefront sensing ,Scalloping ,Outer scale of turbulence ,Multi-conjugate AO ,Laser Tomography AO - Abstract
We present an overview of the latest simulation results obtained for the European Extremely Large Telescope's different Adaptive Optics systems. Different areas of the telescope and instruments are covered. Simulations showing how a single conjugated AO system can be used to detect a scalloping error is shown. We show that when the scalloping error modes are entered in the reconstruction modal basis, the DM shape can be used to estimate the scalloping error through a simple matrix vector multiply. Temporal averaging allows to get rid of the atmospheric noise on the scalloping measurement assuming a perfect “scalloping actuator” and to get a measurement accuracy of ~20nm rms. In a second part, we focus on a few results obtained on tomographic AO systems, like for example the sensitivity to the number of Deformable Mirrors and their pitch in multi-conjugate AO, and the impact of the outer scale of turbulence on Laser tomography AO.
- Published
- 2015
40. Functional–Structural Plant Models Mission in Advancing Crop Science: Opportunities and Prospects
- Author
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Soualihou Soualiou, Zhiwei Wang, Weiwei Sun, Philippe de Reffye, Brian Collins, Gaëtan Louarn, and Youhong Song
- Subjects
functional-structural plant modeling ,plant architecture ,plant phenotyping ,genotype to phenotype ,assisted molecular breeding ,Plant culture ,SB1-1110 - Abstract
Functional–structural plant models (FSPMs) have been evolving for over 2 decades and their future development, to some extent, depends on the value of potential applications in crop science. To date, stabilizing crop production by identifying valuable traits for novel cultivars adapted to adverse environments is topical in crop science. Thus, this study will examine how FSPMs are able to address new challenges in crop science for sustainable crop production. FSPMs developed to simulate organogenesis, morphogenesis, and physiological activities under various environments and are amenable to downscale to the tissue, cellular, and molecular level or upscale to the whole plant and ecological level. In a modeling framework with independent and interactive modules, advanced algorithms provide morphophysiological details at various scales. FSPMs are shown to be able to: (i) provide crop ideotypes efficiently for optimizing the resource distribution and use for greater productivity and less disease risk, (ii) guide molecular design breeding via linking molecular basis to plant phenotypes as well as enrich crop models with an additional architectural dimension to assist breeding, and (iii) interact with plant phenotyping for molecular breeding in embracing three-dimensional (3D) architectural traits. This study illustrates that FSPMs have great prospects in speeding up precision breeding for specific environments due to the capacity for guiding and integrating ideotypes, phenotyping, molecular design, and linking molecular basis to target phenotypes. Consequently, the promising great applications of FSPMs in crop science will, in turn, accelerate their evolution and vice versa.
- Published
- 2021
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41. Selective wet oxidation of AlAsSb alloys on GaAs
- Author
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Stephane Calvez, Oleksandr Stepanenko, Kevin Louarn, Emmanuelle Daran, Alexandre Arnoult, and Guilhem Almuneau
- Subjects
Physics ,QC1-999 - Abstract
In this paper, the oxidation of thin low-Sb-containing AlAsSb layers quasi-lattice matched on GaAs substrates is studied in detail since, compared to AlGaAs, these alloys had the prospects of being laterally oxidized at a faster rate, at lower process temperatures, and with a reduced volume change. Combining monitoring data of the oxidation kinetics and anisotropy with atomic-force-microscopy surface measurements enables us to establish the optimal composition range and process parameters that lead to nearly isotropic and Sb-segregation-free oxidations. The study also shows that strain plays a central role in triggering the detrimental Sb segregation.
- Published
- 2021
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42. The Influence of Alkali Metals on the Doping of Poly(p-phenylene) Oligomers
- Author
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Laura Oliveira Péres, Rebeca da Rochas Rodrigues, and Guy Louarn
- Subjects
phenylene ,oligomers ,X-ray ,Raman ,terphenyl ,quaterphenyl ,Organic chemistry ,QD241-441 - Abstract
In this study, we report on crystallographic studies that were performed on Na- and K-doped terphenyl and quaterphenyl. The data obtained via X-ray scattering and transmission electron diffraction show that, for both K-doped terphenyl and quaterphenyl samples, there is an increase in the c parameter. However, in regard to Na-doped terphenyl, there is a c parameter decrease along with an a parameter increase, which may be accounted for by the polymerization of this oligomer. Moreover, in order to complete the crystallographic study, a Raman analysis was conducted to describe the localization of the radical anions and the local distortions induced by the electric charges during the doping process.
- Published
- 2022
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43. Properties of Electrons Accelerated by the Ganymede‐Magnetosphere Interaction: Survey of Juno High‐Latitude Observations.
- Author
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Rabia, J., Hue, V., André, N., Nénon, Q., Szalay, J. R., Allegrini, F., Sulaiman, A. H., Louis, C. K., Greathouse, T. K., Sarkango, Y., Santos‐Costa, D., Blanc, M., Penou, E., Louarn, P., Ebert, R. W., Gladstone, G. R., Mura, A., Connerney, J. E. P., and Bolton, S. J.
- Subjects
ATMOSPHERE of Jupiter ,PARTICLE acceleration ,ELECTRON distribution ,JUNO (Space probe) ,ELECTRONS ,ELECTRON beams - Abstract
The encounter between the Jovian co‐rotating plasma and Ganymede gives rise to electromagnetic waves that propagate along the magnetic field lines and accelerate particles by resonant or non‐resonant wave‐particle interaction. They ultimately precipitate into Jupiter's atmosphere and trigger auroral emissions. In this study, we use Juno/JADE, Juno/UVS data, and magnetic field line tracing to characterize the properties of electrons accelerated by the Ganymede‐magnetosphere interaction in the far‐field region. We show that the precipitating energy flux exhibits an exponential decay as a function of downtail distance from the moon, with an e‐folding value of 29°, consistent with previous UV observations from the Hubble Space Telescope (HST). We characterize the electron energy distributions and show that two distributions exist. Electrons creating the Main Alfvén Wing (MAW) spot and the auroral tail always have broadband distribution and a mean characteristic energy of 2.2 keV while in the region connected to the Transhemispheric Electron Beam (TEB) spot the electrons are distributed non‐monotonically, with a higher characteristic energy above 10 keV. Based on the observation of bidirectional electron beams, we suggest that Juno was located within the acceleration region during the 11 observations reported. We thus estimate that the acceleration region is extended, at least, between an altitude of 0.5 and 1.3 Jupiter radius above the 1‐bar surface. Finally, we estimate the size of the interaction region in the Ganymede orbital plane using far‐field measurements. These observations provide important insights for the study of particle acceleration processes involved in moon‐magnetosphere interactions. Plain Language Summary: The Galilean moons orbit in a plasma‐rich environment, created by the intense volcanism of Io and transported radially outward in the Jovian magnetosphere. At the orbital locations of the moons, this plasma, co‐rotating with Jupiter, flows at a velocity significantly higher than the moons' orbital speed. Consequently, the moons disturb the plasma flow. This interaction gives rise to a set of physical processes, including the generation of electromagnetic waves that propagate away from the moons and accelerate charged particles, triggering auroral emissions by precipitating into Jupiter's atmosphere. In this study, we investigate the properties of the electrons accelerated by the Ganymede‐magnetosphere interaction. We use data from the JADE and UVS instruments onboard the Juno spacecraft as well as magnetic field line tracing methods. Following a statistical characterization of the electron properties, we compare our results with previous findings that have reported electron observations resulting from the Io‐ and Europa‐magnetosphere interactions. Key Points: Juno particle and UV measurements are combined with field‐line tracing to identify 11 in situ crossings of the Ganymede flux tubeWe provide a statistical study of the accelerated electrons observed in the high‐latitude far‐field regionWe find two distinct regions in which the electrons properties, that is, characteristic energy, energy flux, and distribution, greatly differ [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
44. Temporal and Spatial Variability of the Electron Environment at the Orbit of Ganymede as Observed by Juno.
- Author
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Pelcener, S., André, N., Nénon, Q., Rabia, J., Rojo, M., Kamran, A., Blanc, M., Louarn, P., Penou, E., Santos‐Costa, D., Allegrini, F., Ebert, R. W., Wilson, R. J., Szalay, J., Mauk, B. H., Paranicas, C., Clark, G., Bagenal, F., and Bolton, S.
- Subjects
ORBITS (Astronomy) ,THERMAL electrons ,ELECTRONS ,SOLAR system ,ELECTRON density - Abstract
The thermal and energetic electrons along Ganymede's orbit not only weather the surface of the icy moon, but also represent a major threat to spacecraft. In this article, we rely on Juno plasma measurements to characterize the temporal and spatial variability of the electron environment upstream of Ganymede. In particular, we find that electron spectra observed by Juno have fluxes larger by a factor of 2–9 at energies above 10 keV than what was measured two decades earlier by Galileo. This result will advance our understanding of the surface weathering and may be a concern for the radiation safety of the JUICE mission. Furthermore, the June 2021 close fly‐by of Ganymede through the moon's wake reveals that the open field line regions of its magnetosphere attenuate electron fluxes at all energies by a factor of 1.6–5, thereby offering a natural shelter to visiting spacecraft crossing this region. Plain Language Summary: Ganymede, the only magnetized moon in our Solar System, orbits deep inside the giant magnetosphere of Jupiter where it interacts with the temporally and spatially variable magnetized disk of plasma in corotation around the planet, its magnetodisk. The intensities of ions and electrons precipitating to the surface of Ganymede in particular depend on the location of the moon with respect to the Jovian magnetodisk. In this work, we provide a full quantification of electron properties along the orbit of Ganymede as observed by Juno. This is done by combining observations from two instruments in order to build composite electron energy spectra and derive their omnidirectional fluxes, densities, and pressures. We report that the average electron omnidirectional fluxes are significantly attenuated when measured above or below the magnetodisk, as well as strongly inside the magnetosphere of the moon where its intrinsic magnetic field provides additional shielding. We confirm that the electron total density is dominated by the thermal population, whereas the total pressure is dominated by the suprathermal one. When comparing our results with Galileo‐based observations and models, we find that the latter the latter two underestimate fluxes in particular at high energies, and we put these observations in context for the future exploration of Ganymede by JUICE. Key Points: We present composite electron energy spectra combining all Juno particle data from 07/2017 to 08/2022 at Ganymede's orbitWe study the variability of electron fluxes inside and outside the Jovian magnetodisk as well as within Ganymede's magnetosphereGalileo‐based models underestimate the electron fluxes observed by Juno in particular at high energies [ABSTRACT FROM AUTHOR]
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- 2024
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45. A New Type of Jovian Hectometric Radiation Powered by Monoenergetic Electron Beams.
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Collet, B., Lamy, L., Louis, C. K., Zarka, P., Prangé, R., Louarn, P., Kurth, W. S., and Allegrini, F.
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WAVE amplification ,MONOENERGETIC radiation ,ELECTRON distribution ,DISTRIBUTION (Probability theory) ,RADIO waves ,ELECTRON beams - Abstract
In this study, we statistically analyze the Jovian auroral radio sources detected in situ by Juno/Waves at frequencies f below the electron cyclotron frequency fce. We first conduct a survey of Juno/Waves data over 1–40 MHz from 2016 to 2022. The 15 detected HectOMetric (HOM) sources all lie within 1–5 MHz and are both less frequent than the radio sources commonly observed slightly above fce and clustered in the southern hemisphere, within ∼90–270° longitudes. We analyze these emission regions with a growth rate analysis in the framework of the Cyclotron Maser Instability (CMI), which we apply to JADE‐E high cadence electron measurements. We show that the f < fce emissions correspond to crossed radio sources, ∼300 km wide. They are located in a hot and highly depleted auroral plasma environment, along flux tubes colocated with upward field‐aligned current and at the equatorward edge of the main auroral oval. The wave amplification is consistent with the CMI and its free energy source consists of a shell‐type electron distribution function (EDF) with characteristic energies of 0.2–5keV. More energetic, 5–50 keV, shell‐type EDFs were systematically observed at higher latitudes but without any radio counterpart. Various parameters for the f < fce HOM sources, reminiscent of the ones at Earth/Saturn, are compared. Other CMI‐unstable EDFs, primarily loss cone ones, are systematically observed during the same intervals, giving rise to emission observed at fce < f < fce + 0.5%. Our analysis thus reveals that different portions of the same EDF can be CMI‐unstable and simultaneously amplify radio waves below and above fce. Plain Language Summary: Taking advantage of Juno radio, electron and magnetic measurements within the source of Jupiter's auroral radio emissions, we analyze a new type of HectOMectric (HOM, a wavelength of 1 hm matching a frequency of 3 MHz) emissions observed in situ by Juno/Waves at frequencies f below the electron cyclotron frequency fce. We first survey the Juno/Waves radio observations over 1–40 MHz between 2016 and 2022, covering the first 45 orbits. The 15 detected cases of f < fce emissions are much less frequent than the usual HOM emissions observed slightly above fce and their sources are inhomogeneously distributed. We then analyze these events in the framework of the Cyclotron Maser Instability (CMI) by calculating their theoretical growth rate from electron distribution functions simultaneously measured by the Juno/JADE‐E spectrometer. We show that the f < fce HOM sources are definitely consistent with the CMI powered by electron beams of 0.2–5 keV. This new type of Jovian auroral radio emission is reminiscent of the ones prominently observed at Earth and Saturn. These f < fce sources co‐exist with HOM emission at fce < f < fce + 0.5%, which is also driven by the CMI based on different well‐known sources of free energy. Key Points: A survey of Juno/Waves in situ measurement (2016–2022) reveals 15 hectometric sources observed below the local electron cyclotron frequencyWe show with a Cyclotron Maser Instability growth rate analysis using Juno/JADE‐E data that they are generated by 0.2–5 keV shell electronsThis new source of Jovian auroral radio emission is reminiscent of the auroral kilometric radiations of Earth and Saturn [ABSTRACT FROM AUTHOR]
- Published
- 2024
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46. Jovian High‐Latitude Ionospheric Ions: Juno In Situ Observations
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P. W. Valek, F. Allegrini, F. Bagenal, S. J. Bolton, J. E. P. Connerney, R. W. Ebert, T. K. Kim, S. M. Levin, P. Louarn, D. J. Mccomas, J. R. Szalay, M. F. Thomsen, and R. J. Wilson
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Jupiter ,ionosphere ,high latitude ,ions ,in situ ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Abstract The low‐altitude, high‐velocity trajectory of the Juno spacecraft enables the Jovian Auroral Distributions Experiment to make the first in situ observations of the high‐latitude ionospheric plasma. Ions are observed to energies below 1 eV. The high‐latitude ionospheric ions are observed simultaneously with a loss cone in the magnetospheric ions, suggesting precipitating magnetospheric ions contribute to the heating of the upper ionosphere, raising the scale height, and pushing ionospheric ions to altitudes of 0.5 RJ above the planet where they are observed by Jovian Auroral Distributions Experiment. The source of the magnetospheric ions is tied to the Io torus and plasma sheet, indicated by the cutoff seen in both the magnetospheric and ionospheric plasma at the Io M‐shells. Equatorward of the Io M‐shell boundary, the ionospheric ions are not observed, indicating a drop in the scale height of the ionospheric ions at those latitudes.
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- 2019
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47. Solar Orbiter SWA Observations of Electron Strahl Properties Inside 1 AU
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Christopher J. Owen, Joel Baby Abraham, Georgios Nicolaou, Daniel Verscharen, Philippe Louarn, and Timothy S. Horbury
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solar wind ,electron strahl ,heliosphere ,Solar Orbiter ,Elementary particle physics ,QC793-793.5 - Abstract
The Solar Wind Analyser (SWA) suite on Solar Orbiter includes an Electron Analyser System (SWA-EAS) which is capable of high temporal and angular resolution measurements of solar wind electrons in the energy range ∼1 eV to ∼5 keV. In this article we report early nominal phase observations of the suprathermal electron population at energies ≥70 eV (representative of the ’strahl’ population), and use a simple fitting routine and classification system to determine the characteristics of the distributions and determine the variations in their properties as a function of heliocentric distance and solar wind properties. We find that under our classification system a significant population of radially outward moving strahl beams is identifiable in the tested samples. These are seen in across solar wind speed regimes, but, consistent with earlier observations, are slightly more prevalent in high speed wind. These beams occur at all distances examined (∼0.43 to ∼1.0 AU), but do not show significant evolution with distance, suggesting a balance between focusing and scattering processes across the distance range covered. However, the data suggests that the beams broaden on average with increasing magnetic field strength and narrow on average with increasing solar wind speed. We also identify a small population, occurring in sporadic clusters, which have deficits in phase space density in the sunward moving part of the electron distribution. These clusters occur across the distance range sampled and show some variations in average properties with radial distance, suggesting they too are influenced by competing scattering and (de-)focusing processes. The implications for the origin and evolution of these electron populations derived from these new observations are explored.
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- 2022
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48. Efficient and Facile Synthetic Route of MoO3:MoS2 Hybrid Thin Layer via Oxidative Reaction of MoS2 Nanoflakes
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Hind Lamkaouane, Hajar Ftouhi, Mireille Richard-Plouet, Nicolas Gautier, Nicolas Stephant, Mimoun Zazoui, Mohammed Addou, Linda Cattin, Jean Christian Bernède, Yamina Mir, and Guy Louarn
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hybrid layer ,thin films ,2D nanomaterials ,transition metal dichalcogenide ,molybdenum disulfide ,molybdenum trioxide ,Chemistry ,QD1-999 - Abstract
In the present study, MoO3:MoS2 hybrid thin layers have been synthesized through partial oxidation of MoS2. We have demonstrated that the reaction requires darkness conditions to decrease the oxidation rate, thus obtaining the hybrid, MoO3:MoS2. A simple liquid-phase exfoliation (LPE) is carried out to achieve homogenous MoS2 nanoflakes and high reproducibility of the results after MoS2 oxidation. XPS analyses reveal the presence of MoO3, MoS2, and MoOxSy in the hybrid layer. These results are also confirmed by X-ray diffraction and high-resolution TEM. Optical absorbance reveals that the absorption peaks of the MoO3:MoS2 hybrid are slightly redshifted with the appearance of absorption peaks in the near-infrared region due to the defects created after the oxidation reaction. The composition and atomic percentages of each component in the hybrid layer as a function of reaction time have also been reported to give perspective guides for improving electronic and optoelectronic devices based on 2D-MoS2.
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- 2022
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49. The place of 18F FDG PET/CT in the management of patients with eosinophilic fasciitis: a case report
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N. Belfeki, N. Louarn, I. Chouchane, A. Abbadi, and S. Diamantis
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Eosinophilic fasciitis ,FDG ,PET/CT. ,Medicine ,Internal medicine ,RC31-1245 - Abstract
Eosinophilic fasciitis is a rare connective tissue disease with a clinical presentation of scleroderma-like disease. We report a case of a 36-year-old female patient with a 6-month history of progressive stiffness involving her forearms and legs with joint pain. Laboratory examinations showed hypereosinophilia and elevated C-reactive protein. 18F FDG PET/CT showed diffuse and symmetrical increased uptake in the fasciae of the upper and lower limbs, sparing both muscles and fat tissues. Guided biopsy and histologic examination confirmed the diagnosis of eosinophilic fasciitis. 18F FDG PET/CT is of great help in the diagnosis of eosinophilic fasciitis, as it can guide the biopsy where FDG uptake is strongest and also help rule out possible associated neoplasms.
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- 2021
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50. Alfvénic velocity spikes and rotational flows in the near-Sun solar wind
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Kasper, J. C., Bale, S. D., Belcher, J. W., Berthomier, M., Case, A. W., Chandran, B. D. G., Curtis, D. W., Gallagher, D., Gary, S. P., Golub, L., Halekas, J. S., Ho, G. C., Horbury, T. S., Hu, Q., Huang, J., Klein, K. G., Korreck, K. E., Larson, D. E., Livi, R., Maruca, B., Lavraud, B., Louarn, P., Maksimovic, M., Martinovic, M., McGinnis, D., Pogorelov, N. V., Richardson, J. D., Skoug, R. M., Steinberg, J. T., Stevens, M. L., Szabo, A., Velli, M., Whittlesey, P. L., Wright, K. H., Zank, G. P., MacDowall, R. J., McComas, D. J., McNutt, Jr, R. L., Pulupa, M., Raouafi, N. E., and Schwadron, N. A.
- Published
- 2019
- Full Text
- View/download PDF
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