1,173 research outputs found
Detection of ultra-high energy cosmic ray showers with a single-pixel fluorescence telescope
No full textAbstract not available.T. Fujii, M. Malacari, M. Bertaina, M. Casolino, B. Dawson, P. Horvath, M. Hrabovsky, J. Jiang, D. Mandat, A. Matalon, J.N. Matthews, P. Motloch, M. Palatka, M. Pech, P. Privitera, P. Schovanek, Y. Takizawa, S.B.Thomas, P. Travnicek, K. Yamaza
Sources of two-dimensional supercritical perpendicular shock nonstationarity: nonlinear whistler emission versus shock front self-reformation
No full textInternational audienceTwo-dimensional (2-D) full particle electromagnetic simulations are used for analysing in detail different nonstationary behaviors of perpendicular supercritical shocks (Lembège et al., 2009). A recent study (Hellinger et al., 2007) has previously evidenced that the shock front is dominated by the emission of coherent large amplitude whistler waves for some plasma conditions and shock regimes. These whistler waves are emitted in two-dimensional perpendicular shocks and inhibit the self-reformation driven by the accumulation of reflected ions: then, the shock front appears almost "quasistationary", a result which could seem in apparent contradiction with previous results. The present study allows to clarify the situation by bringing new complementary results:(i) there exists a transition regime around a critical Mach number threshold Mwwe, within which both self-reformation and whistler waves emission can co-exist. (ii) Below (above) this threshold regime, the self-reformation (whistler waves emission) is fully retrieved and becomes dominant. (iii) As MA is larger than Mwwe, this shock front looks "quasi-stationary" in 1-D y-averaged fields profiles, but in fact is nonstationary in full 2-D profiles. Moreover, this nonstationarity is characterized by a quasi-periodic reinforcement of nonlinear waves emission from the ramp. This effect results from the fact that the emission of nonlinear whistler waves varies in time according to the local need for balancing the nonlinear effects at the shock ramp (steepening). (iv) These results are observed for a strictly perpendicular shock, as B0 is within the simulation plane; in contrast, as B0 is perpendicular to the simulation plane, no whistler waves emission is evidenced even for large Mach number; only self-reformation is observed. The coexistence of both processes within the transition regime is characterized by a rapid occurrence of the self-reformation at early time of a run, while nonlinear waves are dominating the whole shock dynamics at later times of the same run. A parametric study shows that effectively the growth of these nonlinear waves is strongly dependant on the time, and increases drastically as the Mach number is above the threshold Mwwe. Present results, even if unexpected, are shown to be in a good agreement with previous 2D PIC and 2D hybrid simulations these are compared with. References : HELLINGER P., P. TRAVICEK, B. LEMBEGE and P. SAVOINI . Emission of nonlinear whistler waves at the front of perpendicular supercritical shocks: Hybrid versus full particle simulations J. Geophys. Res. , VOL. 34, L14109, doi:10.1029/2007GL030239, 2007 LEMBEGE B. , P. SAVOINI, P. HELLINGER and P.M. TRAVNICEK Nonstationarity of a two-dimensional perpendicular shock: competing mechanims J. Geophys. Res., 114, A03217, doi:10.1029/2008JA013618, 200
Madisonia ordinata J. Ponert, Chumova & P. Travnicek 2023, comb. nov.
No full text<i>Madisonia ordinata</i> (Luer & Dodson) J.Ponert, Chumová & P.Trávníček, <i>comb. nov.</i> (Fig. 1) <p> Basionym: <i>Specklinia ordinata</i> Luer & Dodson in Luer (2006: 61).</p> <p> Homotypic synonyms: <i>Anathallis ordinata</i> (Luer & Dodson) Luer (2009: 259), <i>Pleurothallis ordinata</i> (Luer & Dodson) Pfahl (2013: 1).</p>Published as part of <i>Ponert, Jan, Trávníček, Pavel & Chumová, Zuzana, 2023, Phylogenetic placement of Specklinia ordinata in Madisonia (Pleurothallidinae, Orchidaceae), pp. 161-166 in Phytotaxa 585 (2)</i> on page 164, DOI: 10.11646/phytotaxa.585.2.7, <a href="http://zenodo.org/record/7681641">http://zenodo.org/record/7681641</a>
The prototype opto-mechanical system for the Fluorescence detector Array of Single-pixel Telescopes
No full textPublished: July 4, 2017The Fluorescence detector Array of Single-pixel Telescopes is a proposed low-cost, large-area, next-generation experiment for the detection of ultrahigh-energy cosmic rays via the atmospheric fluorescence technique. The proposed design involves the deployment of several hundred large field-of-view fluorescence telescopes on a regular grid of several thousand square kilometers in ground area. This paper describes the optical design of the prototype telescope, as well as its mechanical support structure.D. Mandat, M. Palatka, M. Pech, P. Schovanek, P. Travnicek, L. Nozka, M. Hrabovsky, P. Horvath, T. Fujii, P. Privitera, M. Malacari, J. Farmer, A. Galimova, A. Matalon, M. Merolle, X. Ni, J.A. Bellido, J.N. Matthews and S.B. Thoma
Competition among native and invasive Phragmites australis populations: An experimental test of the effects of invasion status, genome size, and ploidy level
No full textAmong the traits whose relevance for plant invasions has recently been suggested are genome size (the amount of nuclear DNA) and ploidy level. So far, research on the role of genome size in invasiveness has been mostly based on indirect evidence by comparing species with different genome sizes, but how karyological traits influence competition at the intraspecific level remains unknown. We addressed these questions in a common-garden experiment evaluating the outcome of direct intraspecific competition among 20 populations of Phragmites australis, represented by clones collected in North America and Europe, and differing in their status (native and invasive), genome size (small and large), and ploidy levels (tetraploid, hexaploid, or octoploid). Each clone was planted in competition with one of the others in all possible combinations with three replicates in 45-L pots. Upon harvest, the identity of 21 shoots sampled per pot was revealed by flow cytometry and DNA analysis. Differences in performance were examined using relative proportions of shoots of each clone, ratios of their aboveground biomass, and relative yield total (RYT). The performance of the clones in competition primarily depended on the clone status (native vs. invasive). Measured in terms of shoot number or aboveground biomass, the strongest signal observed was that North American native clones always lost in competition to the other two groups. In addition, North American native clones were suppressed by European natives to a similar degree as by North American invasives. North American invasive clones had the largest average shoot biomass, but only by a limited, nonsignificant difference due to genome size. There was no effect of ploidy on competition. Since the North American invaders of European origin are able to outcompete the native North American clones, we suggest that their high competitiveness acts as an important driver in the early stages of their invasion
Detection of high-energy muons in cosmic ray showers.
No full textThe DELPHI detector located at LEP accelerator has been used to measure multi-muon bundles originated from cosmic ray interactions. Two subdetectors - Hadron Calorimeter and Time Projection Chamber - are used for this purpose. The 1999 and 2000 data are analyzed over wide range of muon multiplicities. The muon multiplicity distribution is compared with prediction of Monte-Carlo simulation based on CORSIKA/QGSJET. The Monte-Carlo does not describe the large multiplicity part of data. Even the extreme assumption on the cosmic ray composition (pure iron nuclei) hardly predicts number of high multiplicity events comparable with the data. The impact of QGSJET internal parameters onto the result is also studied.Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi
Using stars to determine the absolute pointing of the fluorescence detector telescopes of the Pierre Auger Observatory
No full textWe describe in this paper two methods to accurately determine the absolute pointing of the fluorescence detector (FD) telescopes of the Pierre Auger Observatory. Our aim is to provide reliable and precise procedures to check and monitor the absolute telescope’s pointing and its long-term stability during the whole life of the project, estimated to be about 20 years.
The two methods described, called “single pixel method” and “star track method”, are based on the FD capability to be sensitive to signals left by stars traversing the telescope field of view. As the star positions in the sky are known with very high precision, the identification of the star signals provides a powerful tool to check the telescope alignment. We used data acquired during regular observation periods in 2004 and we demonstrated that the two methods presented in this paper provide compatible sets of pointing directions
Studium vlivu hadronizace a detektoru na urcovani kinematickych charakteristik partonu v interakcich
No full textFirst results from the full-scale prototype for the Fluorescence detector Array of Single-pixel Telescopes
No full textThe Fluorescence detector Array of Single-pixel Telescopes (FAST) is a design concept for the next generation of ultrahigh-energy cosmic ray (UHECR) observatories, addressing the require- ments for a large-area, low-cost detector suitable for measuring the properties of the highest en- ergy cosmic rays. In the FAST design, a large field of view is covered by a few pixels at the focal plane of a mirror or Fresnel lens. Motivated by the successful detection of UHECRs using a prototype comprised of a single 200 mm photomultiplier-tube and a 1 m2 Fresnel lens system [Astropart.Phys. 74 (2016) 64-72], we have developed a new full-scale prototype consisting of four 200 mm photomultiplier-tubes at the focus of a segmented mirror of 1.6 m in diameter. In October 2016 we installed the full-scale prototype at the Telescope Array site in central Utah, USA, and began steady data taking. We report on first results of the full-scale FAST prototype, including measurements of artificial light sources, distant ultraviolet lasers, and UHECRs.Toshihiro Fujii, Max Malacari, Justin Albury, Jose A. Bellido, John Farmer, Aygul Galimova, Pavel Horvath, Miroslav Hrabovsky, Dusan Mandat, Ariel Matalon, John N. Matthews, Maria Merolle, Xiaochen Ni, Libor Nozka, Miroslav Palatka, Miroslav Pech, Paolo Privitera, Petr Schovanek, Stan B. Thomas, Petr Travnicek (FAST Collaboration
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