457 research outputs found
Selecting background galaxies in weak-lensing analysis of galaxy clusters
In this paper, we present a new method to select the faint, background
galaxies used to derive the mass of galaxy clusters by weak lensing.
The method is based on the simultaneous analysis of the shear signal, that
should be consistent with zero for the foreground, unlensed galaxies, and of
the colors of the galaxies: photometric data from the COSMic evOlution Survey
are used to train the color selection. In order to validate this methodology,
we test it against a set of state-of-the-art image simulations of mock galaxy
clusters in different redshift [] and mass
[] ranges, mimicking medium-deep multicolor
imaging observations (e.g. SUBARU, LBT).
The performance of our method in terms of contamination by unlensed sources
is comparable to a selection based on photometric redshifts, which however
requires a good spectral coverage and is thus much more observationally
demanding. The application of our method to simulations gives an average ratio
between estimated and true masses of . As a further test,
we finally apply our method to real data, and compare our results with other
weak lensing mass estimates in the literature: for this purpose we choose the
cluster Abell 2219 (), for which multi-band (BVRi) data are publicly
available.Comment: MNRAS, Accepted 2016 February 2
Synergistic effects of zinc borate and aluminiumtrihydroxide on flammability behaviour of aerospaceepoxy system
The flame retardancy of mono-component epoxy resin (RTM6), widely used for aerospace composites, treated with zinc borate (ZB), aluminium trihydroxide (ATH) and their mixtures at different concentrations have been investigated by morphological and thermal characterization. Cone calorimeter data reveal that combustion behaviour, heat release rate peak (PHRR) and heat release rate average (HRR Average) of RTM6 resin decrease substantially when synergistic effects of zinc borate and aluminium trihydroxide intervene. Thermogravimetric (TGA) results and analysis of the residue show that addition higher than 20% w/w of ZB, ATH, and their mixture greatly promotes RTM6 char formation acting as a barrier layer for the fire development. Depending upon the different used flame additives, SEM micrographs indicate that the morphology of residual char could vary from a compact amalgam-like structure, for the RTM6+ZB system, to a granular structure, characterized by very small particles of degraded resin and additive for the AT
Feasibility of low energy radiative capture experiments at the LUNA underground accelerator facility
The LUNA (Laboratory Underground for Nuclear Astrophysics) facility has been
designed to study nuclear reactions of astrophysical interest. It is located
deep underground in the Gran Sasso National Laboratory, Italy. Two
electrostatic accelerators, with 50 and 400 kV maximum voltage, in combination
with solid and gas target setups allowed to measure the total cross sections of
the radiative capture reactions H(p,)3He and
N(p,)O within their relevant Gamow peaks. We report on
the gamma background in the Gran Sasso laboratory measured by germanium and
bismuth germanate detectors, with and without an incident proton beam. A method
to localize the sources of beam induced background using the Doppler shift of
emitted gamma rays is presented. The feasibility of radiative capture studies
at energies of astrophysical interest is discussed for several experimental
scenarios.Comment: Submitted to Eur. Phys. J.
A weak lensing analysis of the PLCK G100.2-30.4 cluster
We present a mass estimate of the Planck-discovered cluster PLCK G100.2-30.4,
derived from a weak lensing analysis of deep SUBARU griz images. We perform a
careful selection of the background galaxies using the multi-band imaging data,
and undertake the weak lensing analysis on the deep (1hr) r-band image. The
shape measurement is based on the KSB algorithm; we adopt the PSFex software to
model the Point Spread Function (PSF) across the field and correct for this in
the shape measurement. The weak lensing analysis is validated through extensive
image simulations. We compare the resulting weak lensing mass profile and total
mass estimate to those obtained from our re-analysis of XMM-Newton
observations, derived under the hypothesis of hydrostatic equilibrium. The
total integrated mass profiles are in remarkably good agreement, agreeing
within 1 across their common radial range. A mass is derived for the cluster from our weak lensing
analysis. Comparing this value to that obtained from our reanalysis of
XMM-Newton data, we obtain a bias factor of (1-b) = 0.8 0.1. This is
compatible within 1 with the value of (1-b) obtained by Planck
Collaboration XXIV from their calibration of the bias factor using
newly-available weak lensing reconstructed masses.Comment: 11 pages, 12 figures, accepted for publication on Astronomy &
Astrophysics; updates in affiliation
First measurement of the 14N(p,gamma)15O cross section down to 70 keV
In stars with temperatures above 20*10^6 K, hydrogen burning is dominated by
the CNO cycle. Its rate is determined by the slowest process, the
14N(p,gamma)15O reaction. Deep underground in Italy's Gran Sasso laboratory, at
the LUNA 400 kV accelerator, the cross section of this reaction has been
measured at energies much lower than ever achieved before. Using a windowless
gas target and a 4pi BGO summing detector, direct cross section data has been
obtained down to 70 keV, reaching a value of 0.24 picobarn. The Gamow peak has
been covered by experimental data for several scenarios of stable and explosive
hydrogen burning. In addition, the strength of the 259 keV resonance has been
remeasured. The thermonuclear reaction rate has been calculated for
temperatures 90 - 300 *10^6 K, for the first time with negligible impact from
extrapolations
Closing the loop of SIEM analysis to Secure Critical Infrastructures
Critical Infrastructure Protection is one of the main challenges of last years. Security Information and Event Management (SIEM) systems are widely used for coping with this challenge. However, they currently present several limitations that have to be overcome. In this paper we propose an enhanced SIEM system in which we have introduced novel components to i) enable multiple layer data analysis; ii) resolve conflicts among security policies, and discover unauthorized data paths in such a way to be able to reconfigure network devices. Furthermore, the system is enriched by a Resilient Event Storage that ensures integrity and unforgeability of events stored
Acute and cumulative effects of rTMS on behavioural and EMG parameters in Focal Hand Dystonia
Previous studies suggest that low-frequency repetitive Transcranial Magnetic Stimulation (rTMS) over contralateral premotor cortex (PMC) might ameliorate Focal Hand Dystonia (FHD) symptoms. In the present study behavioral and muscle activity outcomes were explored in a patient with FHD following a single and multiple sessions of rTMS. The patient's behavior was assessed on handwriting tasks, while surface EMG signals were recorded. In Experiment 1 evaluations were performed before and after one session of active and sham 1Hz rTMS over contralateral PMC. In Experiment 2, evaluations were performed before and after six sessions of the same treatment. In Experiment 1 active rTMS improved the patient's performance, although the EMG amplitude did not change. In Experiment 2, the patient showed an improvement of performance along with a decrease of 20% in the EMG amplitude. These results demonstrated that a single session of rTMS ameliorated the patient's performance, while multiple sessions were necessary to reduce muscles activity
A multi-indicator approach to compare the sustainability of organic vs. integrated management of grape production
Sustainable agricultural practices are increasingly becoming a strategic asset for global and national environmental policies and economy. A big challenge is the selection of appropriate indicators to describe the complexity of the agroecosystem management. In the present work, the sustainability of grape production, in vineyard trials of Pinot blanc and Rhine Riesling, managed with integrated (INT) and organic management (organic, with cattle manure ORG1 and organic with green manure ORG2), was compared using a multi-indicator approach. The experiment was set in 2011 (1.5 ha in Trento, Italy) and carbon footprint (CF), nitrogen footprint (NF), water footprint (WF), soil microbial diversity (alpha diversity of bacteria, fungi, oomycetes communities) and soil C stock change, were evaluated in 2018. The CF was 0.213â0.227 kg CO2-eq/kg in the INT, 0.144â0.168 kg CO2-eq/kg in ORG1 and 0.134â0.147 kg CO2-eq/kg in ORG2. The NF was around 1 g Nr/kg for the INT, 0.4 g Nr/kg for ORG1 and 0.5 g Nr/kg for ORG2. The WF, excluding the pesticides impact on grey water, was 666â708 L/kg for INT, 605â655 L/kg for ORG1 and 529â580 L/kg for ORG2. The impact of farming practices on soil microbial alpha diversity showed no significant difference among treatments for oomycetes and significantly higher indexes for fungi and bacteria in the ORG1, with INT and ORG2, being similar. No difference in bulk organic C were observed among treatments. Overall, the multi-indicator approach allowed to demonstrate that the organic management was more beneficial for most of the environmental spheres of the agroecosystem compared to integrated management, without affecting the grape yiel
Neutron-induced background by an alpha-beam incident on a deuterium gas target and its implications for the study of the 2H(alpha,gamma)6Li reaction at LUNA
The production of the stable isotope Li-6 in standard Big Bang
nucleosynthesis has recently attracted much interest. Recent observations in
metal-poor stars suggest that a cosmological Li-6 plateau may exist. If true,
this plateau would come in addition to the well-known Spite plateau of Li-7
abundances and would point to a predominantly primordial origin of Li-6,
contrary to the results of standard Big Bang nucleosynthesis calculations.
Therefore, the nuclear physics underlying Big Bang Li-6 production must be
revisited. The main production channel for Li-6 in the Big Bang is the
2H(alpha,gamma)6Li reaction. The present work reports on neutron-induced
effects in a high-purity germanium detector that were encountered in a new
study of this reaction. In the experiment, an {\alpha}-beam from the
underground accelerator LUNA in Gran Sasso, Italy, and a windowless deuterium
gas target are used. A low neutron flux is induced by energetic deuterons from
elastic scattering and, subsequently, the 2H(d,n)3He reaction. Due to the
ultra-low laboratory neutron background at LUNA, the effect of this weak flux
of 2-3 MeV neutrons on well-shielded high-purity germanium detectors has been
studied in detail. Data have been taken at 280 and 400 keV alpha-beam energy
and for comparison also using an americium-beryllium neutron source.Comment: Submitted to EPJA; 13 pages, 8 figure
First Direct Measurement of the ^{17}O(p,\gamma)^{18}F Reaction Cross-Section at Gamow Energies for Classical Novae
Classical novae are important contributors to the abundances of key isotopes,
such as the radioactive ^{18}F, whose observation by satellite missions could
provide constraints on nucleosynthesis models in novae. The
^{17}O(p,\gamma)^{18}F reaction plays a critical role in the synthesis of both
oxygen and fluorine isotopes but its reaction rate is not well determined
because of the lack of experimental data at energies relevant to novae
explosions. In this study, the reaction cross section has been measured
directly for the first time in a wide energy range Ecm = 200 - 370 keV
appropriate to hydrogen burning in classical novae. In addition, the E=183 keV
resonance strength, \omega \gamma=1.67\pm0.12 \mueV, has been measured with the
highest precision to date. The uncertainty on the ^{17}O(p,\gamma)^{18}F
reaction rate has been reduced by a factor of 4, thus leading to firmer
constraints on accurate models of novae nucleosynthesis.Comment: accepted by Phys. Rev. Let
- âŠ