2,864 research outputs found

    Insertion device for pressure testing

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    Test device which introduces either pressure or vacuum into a test pipe or tube, is insertable into the tested item where it secures itself into position and requires no external support. The unit has an operating range from zero to 25,000 psig and to any vacuum level that available equipment can reach

    A Markov Chain Monte Carlo technique to sample transport and source parameters of Galactic cosmic rays: II. Results for the diffusion model combining B/C and radioactive nuclei

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    On-going measurements of the cosmic radiation (nuclear, electronic, and gamma-ray) are shedding new light on cosmic-ray physics. A comprehensive picture of these data relies on an accurate determination of the transport and source parameters of propagation models. A Markov Chain Monte Carlo is used to obtain these parameters in a diffusion model. From the measurement of the B/C ratio and radioactive cosmic-ray clocks, we calculate their probability density functions, with a special emphasis on the halo size L of the Galaxy and the local underdense bubble of size r_h. The analysis relies on the USINE code for propagation and on a Markov Chain Monte Carlo technique (Putze et al. 2009, paper I of this series) for the parameter determination. As found in previous studies, the B/C best-fit model favours diffusion/convection/reacceleration (Model III) over diffusion/reacceleration (Model II). A combined fit on B/C and the isotopic ratios (10Be/9Be, 26Al/27Al, 36Cl/Cl) leads to L ~ 8 kpc and r_h ~ 120 pc for the best-fit Model III. This value for r_h is consistent with direct measurements of the local interstallar medium. For Model II, L ~ 4 kpc and r_h is consistent with zero. We showed the potential and usefulness of the Markov Chain Monte Carlo technique in the analysis of cosmic-ray measurements in diffusion models. The size of the diffusive halo depends crucially on the value of the diffusion slope delta, and also on the presence/absence of the local underdensity damping effect on radioactive nuclei. More precise data from on-going experiments are expected to clarify this issue.Comment: 20 pages, 14 figures, minor language corrections to match the A&A accepted versio

    CLUMPY: a code for gamma-ray signals from dark matter structures

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    We present the first public code for semi-analytical calculation of the gamma-ray flux astrophysical J-factor from dark matter annihilation/decay in the Galaxy, including dark matter substructures. The core of the code is the calculation of the line of sight integral of the dark matter density squared (for annihilations) or density (for decaying dark matter). The code can be used in three modes: i) to draw skymaps from the Galactic smooth component and/or the substructure contributions, ii) to calculate the flux from a specific halo (that is not the Galactic halo, e.g. dwarf spheroidal galaxies) or iii) to perform simple statistical operations from a list of allowed DM profiles for a given object. Extragalactic contributions and other tracers of DM annihilation (e.g. positrons, antiprotons) will be included in a second release.Comment: 15 pages, 7 figures, published in CPC. The CLUMPY code and its documentation can be found at http://lpsc.in2p3.fr/clump

    Nuclear Cosmic Rays propagation in the Atmosphere

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    The transport of the nuclear cosmic ray flux in the atmosphere is studied and the atmospheric corrections to be applied to the measurements are calculated. The contribution of the calculated corrections to the accuracy of the experimental results are discussed and evaluated over the kinetic energy range 10-103^{3} GeV/n. The Boron (B) and Carbon (C) elements system is used as a test case. It is shown that the required corrections become largely dominant at the highest energies investigated. The results are discussed.Comment: Proc. of 30th International Cosmic Ray Conference, Merida, Mexico; 4 page

    Xeff analysis method optimization to enhance IACTs performances

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    The seek of high precision analyses in Îł\gamma-ray astronomy leads to the implementation of multivariate combination, benefiting from several reconstruction methods. Such analysis, called XeffX_{eff}, was developed for the H.E.S.S. data using three shower reconstruction methods. This paper presents the improvement granted to this analysis by refining the distribution calculation of discriminant variables, considering observation conditions, and adding new variables in the XeffX_{eff} combination. The efficiency of the analysis is presented using simulations and real data. A comparison with the standard analysis (model++), for a typical set of sources, shows a significant gain in sensitivity.Comment: Contribution to the Proceedings of the 34th International Cosmic Ray Conference (ICRC 2015), The Hague, The Netherland

    Neutron monitors and muon detectors for solar modulation studies: 2. ϕ\phi time series

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    The level of solar modulation at different times (related to the solar activity) is a central question of solar and galactic cosmic-ray physics. In the first paper of this series, we have established a correspondence between the uncertainties on ground-based detectors count rates and the parameter ϕ\phi (modulation level in the force-field approximation) reconstructed from these count rates. In this second paper, we detail a procedure to obtain a reference ϕ\phi time series from neutron monitor data. We show that we can have an unbiased and accurate ϕ\phi reconstruction (Δϕ/ϕ≃10%\Delta\phi/\phi\simeq 10\%). We also discuss the potential of Bonner spheres spectrometers and muon detectors to provide ϕ\phi time series. Two by-products of this calculation are updated ϕ\phi values for the cosmic-ray database and a web interface to retrieve and plot ϕ\phi from the 50's to today (\url{http://lpsc.in2p3.fr/crdb}).Comment: 15 pages, 5 figures, 2 tables. AdSR, in press. Web interface to get modulation parameter phi(t): new tab in http://lpsc.in2p3.fr/crd

    Work and pay in flexible and regulated labor markets: A generalized perspective on institutional evolution and inequality trends in Europe and the US

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    In den letzten Jahren hat sich eine unified theory aus der Arbeitsökonomik heraus-gebildet, in der die Meinung vorherrscht, dass die Kombination makroökonomi- scher Schocks und flexibler Arbeitsmarktinstitutionen in den USA eine starke Zu-nahme der Lohnungleichheit verursacht habe, wĂ€hrend die gleichen Schocks in Europa vor allem fĂŒr gering qualifizierte Arbeitnehmer eine hohe Arbeitslosigkeit und geringe BeschĂ€ftigungsniveaus gebracht hĂ€tten als (unerwĂŒnschter) Nebeneffekt der durch die strikten institutionellen Regelungen des Arbeitsmarkts in Europa rigiden Löhne. In der vorliegenden Analyse wird hingegen argumentiert, dass Institutionen in Europa eigene Formen der FlexibilitĂ€t entwickelt hĂ€tten, die im Gefolge der in der unified theory beschriebenen Schocks ebenfalls zu einer zunehmenden Un-gleichheit in Europa gefĂŒhrt hĂ€tten, aber eben in anderer Gestalt. In Frankreich sei beispielsweise die Ungleichheit bei der Arbeitsplatzsicherheit schneller gewachsen als in den USA. DarĂŒber hinaus hĂ€tten Entwicklungen auf dem französischen Ar-beitsmarkt dazu gefĂŒhrt, dass sich gering qualifizierte Arbeitnehmer in unsicheren BeschĂ€ftigungsverhĂ€ltnissen konzentrierten. -- In recent years a unified theory has emerged out of labor economics, which argues that a combination of macroeconomic shocks and flexible labor market institutions in the U.S. has produced strong upward trends in wage inequality, while these same shocks have produced high unemployment and low employment growth in Europe as a side effect of the wage stability preserved by that continents rigid labor market in-stitutions. This paper argues instead that European institutions in fact have evolved their own form of flexibility, which, in combination with the macroeconomic shocks described in the unified theory, have also led to rising inequality in Europe, but of a different form. Taking France as an example, inequality of employment security has risen faster here than in the U.S. Furthermore, trends in the French labor market have led to increased concentration of low-skill workers in these insecure job statuses. These results challenge the view that unemployment is the main mecha-nism through which European labor markets absorbed asymmetric shocks to their demand for labor. They also challenge the view that Europeans have intolerance for inequality, but instead suggest that the main difference between the two sides of the Atlantic concerns the nature of the inequalities that each society is willing to tolerate.

    Variation of the X-ray non-thermal emission in the Arches cloud

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    The origin of the iron fluorescent line at 6.4 keV from an extended region surrounding the Arches cluster is debated and the non-variability of this emission up to 2009 has favored the low-energy cosmic-ray origin over a possible irradiation by hard X-rays. By probing the variability of the Arches cloud non-thermal emission in the most recent years, including a deep observation in 2012, we intend to discriminate between the two competing scenarios. We perform a spectral fit of XMM-Newton observations collected from 2000 to 2013 in order to build the Arches cloud lightcurve corresponding to both the neutral Fe Kalpha line and the X-ray continuum emissions. We reveal a 30% flux drop in 2012, detected with more than 4 sigma significance for both components. This implies that a large fraction of the studied non-thermal emission is due to the reflection of an X-ray transient source.Comment: 5 pages, 3 figures, accepted for publication in MNRAS Letter

    Decaying dark matter: a stacking analysis of galaxy clusters to improve on current limits

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    We show that a stacking approach to galaxy clusters can improve current limits on decaying dark matter by a factor ≳5−100\gtrsim 5-100, with respect to a single source analysis, for all-sky instruments such as Fermi-LAT. Based on the largest sample of X-ray-selected galaxy clusters available to date (the MCXC meta-catalogue), we provide all the astrophysical information, in particular the astrophysical term for decaying dark matter, required to perform an analysis with current instruments.Comment: 6 pages, 3 figures, supplementary file available on demand, accepted for publication in PR
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