In this paper we discuss the broad-band X-ray characteristics of a complete sample of 36 type 1 active galactic nuclei (AGN), detected by INTEGRAL in the 20–40 keV band above the 5.5σ level. We present, for all the objects in the sample, the broad-band (1–110 keV) spectral analysis obtained by using INTEGRAL / Swift /Burst Alert Telescope observations together with XMM–Newton , Chandra , ASCA and Swift /X-Ray Telescope data. We also present the general average properties of the sample, i.e. the distribution of photon indices, high-energy cut-offs, reflection fractions and absorption properties, together with an in-depth analysis of their parameter space. We find that the average Seyfert 1 power law has an index of 1.7 with a dispersion of 0.2. The mean cut-off energy is at around 100 keV, with most objects displaying E c in the range 50–150 keV; the average amount of Compton reflection is 1.5 with a typical dispersion of 0.7. We do not find any convincing correlation between the various parameters, an indication that our analysis is not strongly dependent by the interplay between them. Finally, we investigate how the results presented in this work fit into current frameworks for AGN spectral modelling and cosmic diffuse X-ray background synthesis models. 相似文献
Understanding the chemical links between ozone (O3) and its two main precursors, nitrogen oxides (NOx) and volatile organic compounds (VOC), is important for designing effective
photochemical smog reduction strategies. This chemical relationship will determine which precursor (NOx or VOC) emission reduction
will be more effective for decreasing the ozone formation. Under certain conditions, ozone levels decrease as a result of
a reduction in NOx emissions but do not respond significantly to changes in VOC emissions (NOx-sensitive condition), while
under other conditions ozone concentrations decrease in response to reductions in VOCs and may even increase when NOx emissions
are reduced (VOC-sensitive conditions). Indicator species can be used to assess the sensitivity of ozone to changes in the
emissions of its precursors. These indicators are species or species ratios involved in ozone photochemistry which reflect
the primary chemical process through which the ozone was formed. In this work we use the MM5-CAMx model system to explore
the behaviour of various indicator species during two meteorological situations featuring different atmospheric conditions
in a complex terrain area. The results show that indicators based on nitrogen compounds (i.e,. NOy and NOz) are suitable for
defining the transition range from VOC- to NOx-sensitive chemistry, and that despite the uncertainties associated with the
use of chemical indicators, the ratios O3/NOy and O3/NOz may provide a simple and useful way to summarize the response of ozone to changes in NOx and VOC emissions in Southwestern
Spain. 相似文献
In this study, five cores of the Anllóns River bed sediments were analyzed in order to evaluate the downcore and downstream
variations in their chemical composition. The first step was the evaluation of the metal distribution in the bulk (<2 mm)
and fine fractions (<63 μm). The analysis revealed that most of the metals followed the same trend in both fractions, although
the fine fraction presented usually higher concentrations. However, the concentration of both fractions tended to equalize
with increasing contamination. No general increase was observed in the metal concentrations toward the surface which could
be attributed to recent anthropogenic contributions. Instead, the distributions were homogeneous or peaked at various depths
downcore. The most important historical feature was observed at the mouth of the river, at 96-cm depth, corresponding to the
end of the eighteenth century. Upcore increased metal concentrations in parallel with increased fine fraction occurred from
this depth, which were attributed to a bridge construction and consequent changes in sediment dynamics. As the metal concentrations
can be influenced by variations in texture or other sediment characteristics, the second step was to evaluate the efficiency
of several normalized indexes in the assessment of the degree of contamination, by calculating the enrichment factor (EF),
the geoaccumulation index (IGEO) and the pollution load index (PLI). The EFs obtained were <10, thus revealing little anthropogenic inputs to the basin.
The IGEO produced higher values when compared with the EFs. Instead of absolute EF or IGEO absolute values, the use of cumulative probability plots allowed identifying more accurately potential outliers indicating
contamination. Only one population was identified for Zn and Pb, with a reduced number of outliers at the highest concentrations
for Pb. As shown, a more complex plot with the outliers identified at C4 and C5. Finally, the PLI allowed determining the
absence of a significant contamination in the bed sediments. The bioavailable and non-geogenic fractions contribute up to
a 90% of the total concentrations in the case of As and Cu, and showed similar (dissimilar) profiles in comparison with total
metals. Also, the quality guidelines were surpassed, so the high solubility of As, Zn, Pb and Ni in the sediments revealed
the need to monitor the bed sediment quality of the Anllóns River. 相似文献
We carry out a study of the interaction between electromagnetic fields produced innature and cells with no structure but with different shapes and sizes, considered asapproximations of those observed in the human body. Magnetic fields produced byvarious atmospheric and geomagnetic phenomena are compared with the fieldsgenerated by the cells themselves. Working with frequencies up to 105 Hz, we found that in most cases lightning is the natural phenomena capable of producingfield intensities comparable to those generated by the cells. As a first approximationwe assume that a cell might be affected only if a field of intensity comparable to thecell's field is present. Oscillating fields of less intensity and their harmonics can involveresonant interactions with the cells, however this situation is not considered here. Under the approximation of our study we found that the size and the shape are parameters of paramount importance: lightning represents a natural hazard only for the largest cells, while the quadrangular cells are not affected by any of the natural phenomena considered here. 相似文献
Since the publication of the paper of , loss on ignition (LOI) has been widely used as a method to estimate the amount of organic matter and carbonate mineral content (and indirectly of organic and inorganic carbon) in sediments. The relationships between LOI at 550 °C (LOI550) and organic carbon (OC) content and between LOI at 950 °C (LOI950) and inorganic carbon (IC) content are currently accepted as a standard. However, the comparison of 150 analyses of samples of diverse lithologies, collected from a single core, reveals that these relationships are affected by sediment composition (presence of clays, salts, and the variable content of organic carbon). This results in an incremental error on the estimation of carbon content from LOI values that invalidates the use of LOI values as a quantitative method for estimating carbon content. Conversely, the general trends of LOI550 and LOI950 show a good correlation with carbon content (both organic and inorganic) allowing use of LOI as a qualitative test for carbon content. Similarly, in our case, LOI at 105 °C (LOI105) is a good qualitative proxy for the trends in gypsum content. 相似文献
In this paper, we analyze the probability density function (PDF) of solar wind velocity and proton density, based on generalized thermostatistics (GT) approach, comparing theoretical results with observational data. The time-series analyzed were obtained from the SOHO satellite mission where measurements were sampled every hour. We present in the investigations data for two years of different solar activity: (a) moderate activity (MA) period (1997) and (b) high activity (HA) period (2000). For the MA period, the results show good agreement between experimental data and GT model. For the HA period, the agreement between experimental and theoretical PDFs was fairly good, but some distortions were observed, probably due to intermittent characteristics of turbulent processes. As a complementary analysis, the global wavelet spectrum (GWS) was obtained, allowing the characterization of the predominant temporal variability scales for both periods and the stochastic aspects of the nonlinear solar wind variability are discussed. 相似文献
Volcanic rocks from Serra Branca, Iberian Pyrite Belt, Portugal, consist of calc-alkaline felsic and intermediate rocks. The latter are massive andesites, whereas the former include four dacitic to rhyolitic lithologies, distinguishable on spiderdiagrams and binary plots of immobile elements. Zircon thermometry indicates that two felsic suites may have formed from different magmas produced at distinct temperatures, with only limited fractionation within each suite. Alternatively, all the felsic rocks can be related through fractionation of a single magma if the lower zircon saturation temperature obtained for one suite merely results from Zr dilution, mostly reflecting silicification.
The relatively high magma temperatures at Serra Branca ease the classification of felsic rocks based on their HFSE contents and also indicate volcanogenic massive sulfide deposit favorability. This contrasts with other areas of the Belt that register lower magma temperatures and are subsequently barren. However, magma temperatures may have not been high enough to cause complete melting of refractory phases in which HFSE reside during crustal fusion of an amphibolite protolith, implying difficult discrimination of tectonic environments for the felsic rocks. The intermediate rocks were possibly formed by mixing between basaltic magmas and crustal material, compatible with volcanism in an attenuated continental lithosphere setting. 相似文献
We analyse the data from narrow band H and [O III] CCD imaging of a sample of nearby spiral galaxies with active nuclei. The results show that the large scale star formation depends on the level of nuclear activity, with Seyfert 2 presenting the strongest disk and circum-nuclear star formation, while Seyfert 1 show very little. We present particular results for the galaxies NGC 3982, NGC 4579, NGC 5427 and NGC 7469. 相似文献