Titanium oxide (TiO2) nanoparticles are added to sunscreens as they have broad absorbance across the whole UV spectrum. Although photostable, TiO2 nanoparticles can de-excite via surface states giving rise to reactive oxygen species (ROS) formation within the sunscreen formulation. An increased ROS load can degrade organic components within the sunscreen, such as UV absorbers or anti-oxidants, ...

We present analysis and photoionization modeling of the Chandra high resolution spectrum of Mrk 279. There is clear evidence of an absorbing outflow which is best fit by a two component model, one with a low ionization parameter and one with a higher ionization parameter. The column density of the X-ray warm absorber, about logNH = 20, is the smallest known of all AGNs in which X-ray absorbing ...

PKS 0537–441, a bright γ-ray emitting blazar, was observed at radio, optical, UV and X-ray frequencies during various EGRET pointings, often quasi-simultaneously. In 1995 the object was found in an intense emission state at all wavelengths. BeppoSAX observations made in 1998, non-simultaneously with exposures at other frequencies, allow us to characterize precisely the spectral shape of the hig...

We present a complete catalogue of 27 O VI absorbers at low redshift (0.12 < z < 0.5) from a blind survey of 16 QSO echelle spectra in the HST/STIS data archive. These absorbers are identified based only upon matching line profiles and the expected doublet ratio between the λλ 1031, 1037 transitions. Subsequent searches are carried out to identify their associated transitions. Here we present a...

Recent observations suggest the incidence of strong intervening Mg ii absorption systems along the line-of-sight to gamma ray burst (GRB) afterglows is significantly higher than expected from analogous quasar sightlines. One possible explanation is a geometric effect, arising because Mg ii absorbers only partially cover the quasar continuum regions, in which case Mg ii absorbers must be conside...

The H I Parkes All Sky Survey (HIPASS) galaxy catalogue is cross-correlated with known low redshift, low column density (NHI < 10 cm) Lyman-α absorbers from the literature. The redshift-space correlation is found to be similar in strength to HIPASS galaxy self-clustering (correlation length s0,ag = 6 ± 4 and s0,gg = 3.1 ± 0.5 h −1 100 Mpc respectively). In realspace the cross-correlation is str...