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Sökning: WFRF:(Georgescu E.)

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  • Chen, Li-Jen, et al. (författare)
  • Evidence of an extended electron current sheet and its neighboring magnetic island during magnetotail reconnection
  • 2008
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:A12, s. A12213-
  • Tidskriftsartikel (refereegranskat)abstract
    • We have identified a spatially extended electron current sheet (ECS) and its adjacent magnetic island during a magnetotail reconnection event with no appreciable guide field. This finding is based on data from the four Cluster spacecraft and is enabled by detailed maps of electron distribution functions and DC electric fields within the diffusion region. The maps are developed using two-dimensional particle-in-cell simulations with a mass ratio m(i)/m(e) = 800. One spacecraft crossed the ECS earthward of the reconnection null and, together with the other three spacecraft, registered the following properties: (1) The ECS is colocated with a layer of bipolar electric fields normal to the ECS, pointing toward the ECS, and with a half width less than 8 electron skin depths. (2) In the inflow region up to the ECS and separatrices, electrons have a temperature anisotropy (Te-parallel to/Te-perpendicular to > 1), and the anisotropy increases toward the ECS. (3) Within about 1 ion skin depth (d(i)) above and below the ECS, the electron density decreases toward the ECS by a factor of 3-4, reaching a minimum at edges of the ECS, and has a local distinct maximum at the ECS center. (4) A di-scale magnetic island is attached to the ECS, separating it from another reconnection layer. Our simulations established that the electric field normal to the ECS is due to charge imbalance and is of the ECS scale, and ions exhibit electron-scale structures in response to this electric field.
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  • Chen, Li-Jen, et al. (författare)
  • Observation of energetic electrons within magnetic islands
  • 2008
  • Ingår i: Nature Physics. - : Nature Publishing Group. - 1745-2473 .- 1745-2481. ; 4:1, s. 19-23
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic reconnection is the underlying process that releases impulsively an enormous amount of magnetic energy(1) in solar flares(2,3), flares on strongly magnetized neutron stars(4) and substorms in the Earth's magnetosphere(5). Studies of energy release during solar flares, in particular, indicate that up to 50% of the released energy is carried by accelerated 20-100 keV suprathermal electrons(6-8). How so many electrons can gain so much energy during reconnection has been a long-standing question. A recent theoretical study suggests that volume-filling contracting magnetic islands formed during reconnection can produce a large number of energetic electrons(9). Here we report the first evidence of the link between energetic electrons and magnetic islands during reconnection in the Earth's magnetosphere. The results indicate that energetic electron fluxes peak at sites of compressed density within islands, which imposes a new constraint on theories of electron acceleration.
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  • Giunta, Riccardo E., et al. (författare)
  • ESPRAS Survey: National and European Societies for Plastic Surgeons
  • 2024
  • Ingår i: HANDCHIRURGIE MIKROCHIRURGIE PLASTISCHE CHIRURGIE. - 0722-1819 .- 1439-3980.
  • Tidskriftsartikel (refereegranskat)abstract
    • Background The European Society of Plastic, Reconstructive and Aesthetic Surgery (ESPRAS) comprises 40 national societies across Europe. In addition to ESPRAS, there are 8 different European Plastic Surgery societies representing Plastic Surgeons in Europe. The 4 th European Leadership Forum (ELF) of ESPRAS, held under the motto "Stronger together in Europe" in Munich in 2023, aimed to collect and disseminate information regarding the national member societies of ESPRAS and European societies for Plastic Surgeons. The purpose was to identify synergies and redundancies and promote improved cooperation and exchange to enhance coordinated decision-making at the European level. Material and methods An online survey was conducted regarding the organisational structures, objectives and challenges of national and European societies for Plastic Surgeons in Europe. This survey was distributed to official representatives (Presidents, Vice Presidents and General Secretaries) and delegates of national and European societies at the ELF meeting. Missing information was completed using data obtained from the official websites of the respective European societies. Preliminary results were discussed during the 4 th ELF meeting in Munich in March 2023. Results The ESPRAS survey included 22 national and 9 European Plastic Surgery societies representing more than 7000 Plastic Surgeons in Europe. Most national societies consist of less than 500 full members (median 182 members (interquartile range (IQR) 54-400); n=22). European societies, which covered the full spectrum or subspecialities, differed in membership types and congress cycles, with some requiring applications by individuals and others including national societies. The main purposes of the societies include research, representation against other disciplines, specialisation and education as well as more individual goals like patient care and policy regulation. Conclusion This ESPRAS survey offers key insights into the structures, requirements and challenges of national and European societies for Plastic Surgeons, highlighting the relevance of ongoing close exchange between the societies to foster professional advancement and reduce redundancies. Future efforts of the ELF will continue to further explore strategies for enhancing collaboration and harmonisation within the European Plastic Surgery landscape.
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  • Giunta, Riccardo E, et al. (författare)
  • ESPRAS Survey on Breast Reconstruction in Europe. : ESPRAS Umfrage zur Brustrekonstruktion in Europa.
  • 2021
  • Ingår i: Handchirurgie, Mikrochirurgie, plastische Chirurgie : Organ der Deutschsprachigen Arbeitsgemeinschaft fur Handchirurgie : Organ der Deutschsprachigen Arbeitsgemeinschaft fur Mikrochirurgie der Peripheren Nerven und Gefasse : Organ der V.... - : Georg Thieme Verlag KG. - 1439-3980. ; 53:4, s. 340-348
  • Tidskriftsartikel (refereegranskat)abstract
    • The European Leadership Forum (ELF) of the European Society of Plastic, Reconstructive and Aesthetic Surgery (ESPRAS) previously identified the need for harmonisation of breast reconstruction standards in Europe, in order to strengthen the role of plastic surgeons. This study aims to survey the status, current trends and potential regional differences in the practice of breast reconstruction in Europe, with emphasis on equity and access.A largescale web-based questionnaire was sent to consultant plastic and reconstructive surgeons, who are experienced in breast reconstruction and with understanding of the national situation in their country. Suitable participants were identified via the Executive Committee (ExCo) of ESPRAS and national delegates of ESPRAS. The results were evaluated and related to evidence-based literature.A total of 33 participants from 29 European countries participated in this study. Overall, the incidence of breast reconstruction was reported to be relatively low across Europe, comparable to other large geographic regions, such as North America. Equity of provision and access to breast reconstruction was distributed evenly within Europe, with geographic regions potentially affecting the type of reconstruction offered. Standard practices with regard to radiotherapy differed between countries and a clear demand for European guidelines on breast reconstruction was reported.This study identified distinct lack of consistency in international practice patterns across European countries and a strong demand for consistent European guidance. Large-scale and multi-centre European clinical trials are required to further elucidate the presented areas of interest and to define European standard operating procedures.
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  • Matsui, H., et al. (författare)
  • Characteristics of storm time electric fields in the inner magnetosphere derived from Cluster data
  • 2010
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115, s. A11215-
  • Tidskriftsartikel (refereegranskat)abstract
    • Storm-time electric fields in the inner magnetosphere measured by Cluster are reported in this study. First, we show two events around the time when Dst index is at a minimum. The electric field possibly related to subauroral ion drifts and/or undershielding is measured inside the inner edge of the electron plasma sheet in the eveningside. For the second event observed in the nightside, the electric field is partly related to dipolarization and is considered as inductive. An electric field without coincident magnetic signatures is also observed. Spatial coherence of the electric field is not large when we check multispacecraft data. It is inferred that the electric field in the magnetotail penetrates inside the region 1 current, while it is not clear about the electric field within the region 2 current from our data. Then superposed epoch analyses using 71 storms are performed. Electric fields at R = 3.5-6R(E) and less than 25 degrees of magnetic latitudes are enhanced around the minimum Dst at all magnetic local times. Electric fields during the recovery phase decay on a time scale shorter than that of Dst index, which could be interpreted in terms of the relation between electric field and ring current during that storm phase. AC electric fields are generally larger than DC electric fields, indicating that the former component might play some role in accelerating ring current particles. These results will be useful to update our empirical electric field model.
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  • Matsui, H., et al. (författare)
  • Multi-spacecraft observations of small-scale fluctuations in density and fields in plasmaspheric plumes
  • 2012
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 30:3, s. 623-637
  • Tidskriftsartikel (refereegranskat)abstract
    • In this event study, small-scale fluctuations in plasmaspheric plumes with time scales of similar to 10 s to minutes in the spacecraft frame are examined. In one event, plasmaspheric plumes are observed by Cluster, while IMAGE measured density enhancement at a similar location. Fluctuations in density exist in plumes as detected by Cluster and are accompanied by fluctuations in magnetic fields and electric fields. Magnetic fluctuations are transverse and along the direction of the plumes. The E/B ratio is smaller than the Alfv,n velocity. Another similar event is briefly presented. We then consider physical properties of the fluctuations. Alfv,n mode modulated by the feedback instability is one possibility, although non-local generation is likely. It is hard to show that the fluctuations represent a fast mode. Interchange motion is possible due to the consistency between measurements and expectations. The energy source could be a pressure or density gradient in plasmaspheric plumes. When more events are accumulated so that statistical analysis becomes feasible, this type of study will be useful to understand the time evolution of plumes.
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  • Nakamura, R, et al. (författare)
  • Substorm observations in the early morning sector with Equator-S and Geotail
  • 1999
  • Ingår i: Annales Geophysicae. - : SPRINGER VERLAG. - 0992-7689 .- 1432-0576. ; 17:12, s. 1602-1610
  • Tidskriftsartikel (refereegranskat)abstract
    • Data from Equator-S and Geotail are used to study the dynamics of the plasma sheet observed during a substorm with multiple intensifications on 25 April 1998, when both spacecraft were located in the early morning sector (03-04 MLT) at a radial distance o
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  • Resultat 1-16 av 16

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