The spectral energy distribution of fermi bright blazars

We have conducted a detailed investigation of the broadband spectral properties of the γ-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi γ-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/γ-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these γ-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log ν-log ν Fν representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, αro, and optical to X-ray, αox, spectral slopes) and from the γ-ray spectral index. Our data show that the synchrotron peak frequency (νSpeak) is positioned between 1012.5 and 1014.5 Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10 13 and 1017 Hz in featureless BL Lacertae objects. We find that the γ-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright FSRQs and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter γ-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple SSC models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study. Since the LAT detector is more sensitive to flat spectrum γ-ray sources, the correlation between νSpeak and γ-ray spectral index strongly favors the detection of high energy peaked blazars, thus explaining the Fermi overabundance of this type of sources compared to radio and EGRET samples. This selection effect is similar to that experienced in the soft X-ray band where HBL BL Lacs are the dominant type of blazars. © 2010 The American Astronomical Society

Comparative Assessment of the Dyeing Process for Pristine and Modified Cotton Fabrics towards the Reduction of the Environmental Fingerprint

Though an important and chronic source of dyes released to the environment, the determination of the release of dyes that occurs during household or industrial washing is usually disregarded. The main scope of this study is to reveal the extent of dye release through washing, and to understand if the modification of cotton fabrics with cationic polymers could reduce it. Modified cotton fabrics, dyed with Acid Blue 281 (AB) or by a mixture of the reactive dyes Novacron Yellow S-3R (NY), Novacron Ruby S-3B (NR) and Novacron Dark Blue S-GL (NDB), underwent a certified washing process. The dyed fabrics were analyzed colorimetrically, while the washing waters were analyzed spectroscopically, via UV/Vis absorption and surface enhanced Raman scattering (SERS). In the modified fabrics dyed with the acid dye, an increased dye uptake was noticed that exhibited a color intensity of K/S~16, compared to K/S~0.45 of the unmodified fabrics. The corresponding normalized dye release (dye concentration/color intensity factor) in the wash water was ~1.6 for the modified fabrics, compared to ~6.5 in the case of the unmodified fabrics, indicating the significance of cotton modification on both the dye uptake and dye release during washing. In the fabrics dyed with a mixture of selected reactive dyes, the color uptake of modified (K/S~10) was also increased compared with unmodified fabrics (K/S~4.5). An important observation, is that in the case of the dyeing of the reactive dyes mixture, a selectivity on the part of the dye uptake was noticed, since the contribution of NY (yellow) is higher compared to that of the blue (positive value of color indicator coordinate (b)); however, this also resulted in an increased NY dye release during washing. The findings of this study could contribute to the dye release problem control due to fabric washing, and to the understanding of any potential selectivity on the part of dye–cotton interactions

Comparative Assessment of the Dyeing Process for Pristine and Modified Cotton Fabrics towards the Reduction of the Environmental Fingerprint

Though an important and chronic source of dyes released to the environment, the determination of the release of dyes that occurs during household or industrial washing is usually disregarded. The main scope of this study is to reveal the extent of dye release through washing, and to understand if the modification of cotton fabrics with cationic polymers could reduce it. Modified cotton fabrics, dyed with Acid Blue 281 (AB) or by a mixture of the reactive dyes Novacron Yellow S-3R (NY), Novacron Ruby S-3B (NR) and Novacron Dark Blue S-GL (NDB), underwent a certified washing process. The dyed fabrics were analyzed colorimetrically, while the washing waters were analyzed spectroscopically, via UV/Vis absorption and surface enhanced Raman scattering (SERS). In the modified fabrics dyed with the acid dye, an increased dye uptake was noticed that exhibited a color intensity of K/S~16, compared to K/S~0.45 of the unmodified fabrics. The corresponding normalized dye release (dye concentration/color intensity factor) in the wash water was ~1.6 for the modified fabrics, compared to ~6.5 in the case of the unmodified fabrics, indicating the significance of cotton modification on both the dye uptake and dye release during washing. In the fabrics dyed with a mixture of selected reactive dyes, the color uptake of modified (K/S~10) was also increased compared with unmodified fabrics (K/S~4.5). An important observation, is that in the case of the dyeing of the reactive dyes mixture, a selectivity on the part of the dye uptake was noticed, since the contribution of NY (yellow) is higher compared to that of the blue (positive value of color indicator coordinate (b)); however, this also resulted in an increased NY dye release during washing. The findings of this study could contribute to the dye release problem control due to fabric washing, and to the understanding of any potential selectivity on the part of dye–cotton interactions