Experiments carried out under temperatures and relative humidities that approximate ambient conditions show that the rate of hydration of obsidian is a function of the relative humidity, as well as of previously established variables of temperature and obsidian chemical composition. Measurements of the relative humidity of soil at 25 sites and at depths of between 0.01 and 2 m below ground show that in most soil environments, at depths below about 0.25 m, the relative humidity is constant at 100%. We have found that the thickness of the hydrated layer developed on obsidian outcrops exposed to the sun and to relative humidities of 30-90% is similar to that formed on other portions of the outcrop that were shielded from the sun and exposed to a relative humidity of approximately 100%. Surface samples of obsidian exposed to solar heating should hydrate more rapidly than samples buried in the ground. However, the effect of the lower mean relative humidity experiences by surface samples tends to compensate for the elevated temperature, which may explain why obsidian hydration ages of surface samples usually approximate those derived from buried samples.

We present the first experimentally determined oscillator strengths for the Pb ii transitions at 1203.6 Å and 1433.9 Å, obtained from lifetime measurements made using beam-foil techniques. We also present new detections of these lines in the interstellar medium from an analysis of archival spectra acquired by the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. Our observations of the Pb ii λ1203 line represent the first detection of this transition in interstellar gas. Our experimental f-values for the Pb ii λ1203 and λ1433 transitions are consistent with recent theoretical results, including our own relativistic calculations, but are significantly smaller than previous values based on older calculations. Our new f-value for Pb ii λ1433 (0.321 ± 0.034) yields an increase in the interstellar abundance of Pb of 0.43 dex over estimates based on the f-value listed by Morton. With our revised f-values, and with our new detections of Pb ii λ1203 and λ1433, we find that the depletion of Pb onto interstellar grains is not nearly as severe as previously thought, and is very similar to the depletions seen for elements such as Zn and Sn, which have similar condensation temperatures.

We studied a cross-sectional sample of the population of Kech, a small rural town in Pakistan to determine the prevalence and risk factors for hepatitis C infection. The prevalence of hepatitis C was 110 out of 2000 persons (5·5%, 95% confidence interval 4·5–6·5). Higher rates were identified in males. Independent risk factors identified were age ⩾75 years, being a healthcare worker, and injecting drug use. There was a high prevalence of many potential routes of transmission of bloodborne viruses and most people reported at least one potential risk factor.

Energies for symmetric tilt grain boundaries in pure Al and in Al with substitutional Pb defects at coincident sites along the grain boundaries were calculated using a modified embedded atom method potential and density functional theory. The agreement between the analytic potential, the first principles calculations and experiment is reasonably good for the pure system. For the Al-Pb system both the analytic potential and first principles calculations predict that Pb segregation to the interface is energetically preferred compared to the dilute solution. The application of a disclination structural unit model to calculating grain boundary energies over the entire range of tilt angles is also explained.

This paper describes sentinel laboratory surveillance of hepatitis C antibody testing in England. Demographic and test result data were supplemented by follow-up questionnaires sent to the requesting clinician. Between October 2002 and September 2003 almost 75000 anti-HCV tests were performed in eight sentinel centres. More males were tested than females and over half of those tested were aged 25–44 years. Overall 5·7% (3333/58144, range 2·8–7·7%) individuals tested positive. Follow-up questionnaire data showed that 82% (1043/1277) of the positives had injecting drug use reported as the main risk exposure. The majority of negative individuals were undergoing routine screening as recommended for specific patient groups. Most individuals were asymptomatic. Antibody prevalence was estimated to be 34% in current injecting drug users and 42% in former injectors. Comparing positives to routine national surveillance suggests that only 53% (1782/3333) of diagnosed cases were reported. Sentinel laboratory data can provide valuable supplementary data to national surveillance.

The purpose of this questionnaire study was to evaluate the existing knowledge of binaural hearing and the attitudes and practices of prescribing bilateral hearing aids amongst otolaryngologists in the United Kingdom. Of the 950 questionnaires sent to the current members of the British Association of Otolaryngologists and Head and Neck Surgeons (BAO-HNS), there were 591 respondents (62 per cent). The true response rate with completed questionnaires was 59 per cent. Eighty-one per cent of the respondents were aware of the importance of binaural hearing and had a positive attitude towards binaural fitting. The practice of bilateral hearing aid prescriptions was found to be poor amongst all grades on the NHS (less than 10 per cent of all hearing aid prescriptions). This practice in the private sector was variable, dependent largely on patient preference and affordability. The practice of binaural prescription was higher for patients in the paediatric age group than amongst adults. Two common indications for hearing aid prescriptions for unilateral deafness were otitis media with effusion in children (23 per cent of respondents) and for tinnitus masking in adults (12 per cent of respondents). Many otolaryngologists believed that there was not enough evidence to support bilateral bone-anchored hearing aid implantation and bilateral cochlear implantation. Ninety-four per cent of the respondents believed that binaural hearing was as important as binocular vision.