The pernicious effects of deposition of airborne particles on monumental stones have been widely demonstrated, but estimates of deposition fluxes on historic buildings remain a hard task because of ...the lack of careful experiments and modelling. AERBOX is a new box model developed by ENVIROWARE and ENEA, simulating the whole life cycle of aerosols. AERBOX takes into account all the relevant chemical and physical processes involved: emission, chemical reactions in gas and in gas–liquid phases, deposition, entrainment, condensation and nucleation. Concentration and deposition rates of 52 species of gaseous pollutants and 14 species of particulate pollutants are calculated on hourly basis.
A modelling system composed by AERBOX and the emission pre-processor Tool for Hourly Speciation of CORINAIR Annual Emissions (THOSCANE) has been applied to estimate the flux of particulate matter deposited on the monumental area of Florence downtown starting from a CORINAIR emission inventory developed by the Tuscany Region including the industrial and mobile sources in the area of Florence and Prato counties. The time and chemical profiles of the emissions have been adapted to the Tuscany region from the reference profiles given by both the California Air Resource Board and EPA and meteorological inputs were given by the Tuscany Meteorological Centre. Concentrations and deposition fluxes were compared with field measurements available in the open literature.
The neutron capture cross section of 154Gd was measured from 1 eV to 300 keV in the experimental area located 185 m from the CERN n_TOF neutron spallation source, using a metallic sample of ...gadolinium, enriched to 67% in 154Gd. The capture measurement, performed with four C6D6 scintillation detectors, has been complemented by a transmission measurement performed at the GELINA time-of-flight facility (JRC-Geel), thus minimising the uncertainty related to sample composition. An accurate Maxwellian averaged capture cross section (MACS) was deduced over the temperature range of interest for s process nucleosynthesis modelling. We report a value of 880(50) mb for the MACS at kT=30 keV, significantly lower compared to values available in literature. The new adopted 154Gd(n,γ) cross section reduces the discrepancy between observed and calculated solar s-only isotopic abundances predicted by s-process nucleosynthesis models.
This work reports on accurate, high-resolution measurements of the 25Mg(n,γ)26Mg and 25Mg(n,tot) cross sections in the neutron energy range from thermal to about 300 keV, leading to a significantly ...improved 25Mg(n,γ)26Mg parametrization. The relevant resonances for n+25Mg were characterized from a combined R-matrix analysis of the experimental data. This resulted in an unambiguous spin/parity assignment of the corresponding excited states in 26Mg. With this information experimental upper limits of the reaction rates for 22Ne(α,n)25Mg and 22Ne(α,γ)26Mg were established, potentially leading to a significantly higher (α,n)/(α,γ) ratio than previously evaluated. The impact of these results has been studied for stellar models in the mass range 2 to 25 M⊙.
.
Neutron capture cross section measurements on
155
Gd and
157
Gd were performed using the time-of-flight technique at the n_TOF facility at CERN on isotopically enriched samples. The measurements ...were carried out in the n_TOF experimental area EAR1, at 185 m from the neutron source, with an array of 4 C
6
D
6
liquid scintillation detectors. At a neutron kinetic energy of 0.0253 eV, capture cross sections of 62.2(2.2) and 239.8(8.4) kilobarn have been derived for
155
Gd and
157
Gd, respectively, with up to 6% deviation relative to values presently reported in nuclear data libraries, but consistent with those values within 1.6 standard deviations. A resonance shape analysis has been performed in the resolved resonance region up to 181 eV and 307 eV, respectively for
155
Gd and
157
Gd, where on average, resonance parameters have been found in good agreement with evaluations. Above these energies and up to 1 keV, the observed resonance-like structure of the cross section has been analysed and characterised. From a statistical analysis of the observed neutron resonances we deduced: neutron strength function of
2
.
01
(
28
)
×
10
-
4
and
2
.
17
(
41
)
×
10
-
4
; average total radiative width of 106.8(14) meV and 101.1(20) meV and
s
-wave resonance spacing 1.6(2) eV and 4.8(5) eV for n +
155
Gd and n +
157
Gd systems, respectively.
Pollutant concentrations relative to the years 1993-1995 measured in the Bologna urban area by a network of automatic stations (S.A.R.A. Sistema Automatico di Rilevamento Ambientale) are analysed to ...estimate the typical behaviour of the pollutants, especially with regard to periodicities and meteorological dependencies and to attempt prediction for the pollutant daily concentration up to a few days using a statistically based model. The results obtained show the presence of a very significant weekly periodicity for all the analysed pollutants. A yearly periodicity has been found only for the primary pollutants analysed. The statistical prediction, using an ARMA model with meteorological variables as transfer functions, shows good predicting capabilities up to one day for carbon monoxide (CO) and sulphur dioxide (SO2) and up to two days for nitrogen dioxide (NO2).
We have measured the capture cross section of the
155
Gd and
157
Gd isotopes between 0.025 eV and 1 keV. The capture events were recorded by an array of 4 C
6
D
6
detectors, and the capture yield was ...deduced exploiting the total energy detection system in combination with the Pulse Height Weighting Techniques. Because of the large cross section around thermal neutron energy, 4 metallic samples of different thickness were used to prevent problems related to self-shielding. The samples were isotopically enriched, with a cross contamination of the other isotope of less than 1.14%. The capture yield was analyzed with an R-Matrix code to describe the cross section in terms of resonance parameters. Near thermal energies, the results are significantly different from evaluations and from previous time-of-flight experiments. The data from the present measurement at n_TOF are publicly available in the experimental nuclear reaction database EXFOR.
Neutron capture measurements on \(^{155}\)Gd and \(^{157}\)Gd were performed using the time-of-flight technique at the n\_TOF facility at CERN. Four samples in form of self-sustaining metallic discs ...isotopically enriched in \(^{155}\)Gd and \(^{157}\)Gd were used. The measurements were carried out at the experimental area (EAR1) at 185 m from the neutron source, with an array of 4 C\(_6\)D\(_6\) liquid scintillation detectors. The capture cross sections of \(^{155}\)Gd and \(^{157}\)Gd at neutron kinetic energy of 0.0253 eV have been estimated to be 62.2(2.2) kb and 239.8(9.3) kb, respectively, thus up to 6\% different relative to the ones reported in the nuclear data libraries. A resonance shape analysis has been performed in the resolved resonance region up to 180 eV and 300 eV, respectively, in average resonance parameters have been found in good agreement with evaluations. Above these energies the observed resonance-like structures in the cross section have been tentatively characterised in terms of resonance energy and area up to 1 keV.
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