Intrinsic absorbers are significant components of AGN environments that provide valuable information and interesting challenges. We present a very brief (and biased, and sometimes speculative) overview of intrinsic absorbers from the perspective of different absorption line classes. We also discuss ways of addressing and learning from the “problem” of partial coverage of the background light so...

Nowadays modified textiles, especially UV-protective, antibacterial and antimicrobial ones, have become the focus of great interest. In this study, several new UV absorbers, bis(indolyl)methane derivatives, were synthesized and grafted onto polyvinyl alcohol polymer (PVA). Their application properties on cotton-based textile materials were determined; the UV protection factor values of the modi...

A thermogravimetric method was used to measure the vapour pressures of a series of hydroxybenzophenone UV stabilisers. Enthalpies of vaporisation were determined from the slope of a plot of the logarithm of the vapour pressure against reciprocal absolute temperature. Enthalpies of sublimation were measured either directly by the same method or by summing the enthalpy of vaporisation with the en...

cerium oxide (ceria) nano particle, as photodegradation prevention agent was studied in water-based polyurethane clear coat  systems. polyurethane coatings show superior weathering resistance compared with acrylic melamine systems. however, any chemical change has detrimental effects on the property profile of pu coatings. coatings containing various amounts of cerium oxide nanoparticles were p...

We report the detection, based on HST and Keck data, of two peculiar absorbers in the Lyα forest of the quasar PKS 0454+039. These clouds, at redshifts z = 0.6248 and 0.9315 respectively, display both Mg ii and Fe ii absorption lines in addition to the Lyα line. Based upon photoionization models, these are inferred to be photoionized by the intergalactic UV background, and to have H i column de...

A generic assumption of ionization models of quasar absorption systems is that radiation from local sources is negligible compared with the cosmological background. We test this assumption and find that it is unlikely to hold for absorbers as rare as H I Lyman limit systems. Assuming that the absorption systems are gas clouds centered on sources of radiation, we derive analytic estimates for th...

We present a study of 15 long-duration γ-ray burst (GRB) host galaxies at z > 2. The GRBs are selected with available early-time afterglow spectra in order to compare interstellar medium (ISM) absorption-line properties with stellar properties of the host galaxies. In addition to five previously studied hosts, we consider new detections for the host galaxies of GRB 050820 and GRB 060206 and pla...

The lifespan of organic coatings is reduced in outdoor applications by attacks of solar radiation, oxygen and atmospheric pollutants. Degradation of coating and recoating introduce pollutants into the environment. For solvent base coatings like alkyd paints volatile organic compounds (VOC) are main source of pollution. Undesirable mechanical, physical and chemical consequences of the resulting ...

The objectives of this study were to evaluate the light fastness of selected natural dyes (madder, weld and woad) and the effect of some commonly used antioxidants and UV absorbers on the light fastness of these dyes. The photofading rate curves of madder and weld fixed on cotton correspond to type II fading rate curves described by Giles. These results are in concordance with those of Cox-Crew...