Handling uncertainties in background shapes: the discrete profiling method

A common problem in data analysis is that the functional form, as well as the parameter values, of the underlying model which should describe a dataset is not known a priori. In these cases some extra uncertainty must be assigned to the extracted parameters of interest due to lack of exact knowledge of the functional form of the model. A method for assigning an appropriate error is presented. The method is based on considering the choice of functional form as a discrete nuisance parameter which is profiled in an analogous way to continuous nuisance parameters. The bias and coverage of this method are shown to be good when applied to a realistic example.Comment: Accepted by J.Ins

Examining the relationship between pubertal stage, adolescent health behaviours and stress

Background. This paper examines the associations between puberty and three important health behavlours (smoking, food intake and exercise) and explores whether these associations are mediated by puberty's relationship to stress and psychological difficulties.Method. Data were taken from the first year of the ongoing, 5-year, Health and Behaviours in Teenagers Study (HABITS). This is a school-based study set in 36 schools in London. In the first year of the study, 4320 students (2578 boys, 1742 girls) in their first year of secondary education took part.Results. Among girls, being more pubertally advanced was associated with a greater likelihood of having tried smoking. Among boys, being more pubertally advanced was associated with a greater likelihood of having tried smoking, a higher intake of high-fat food and higher levels of exercise. More pubertally advanced girls experienced more stress but not more psychological difficulties. There were no associations between puberty and either stress or psychological difficulties in boys. Stress and psychological difficulties were associated with health behaviours in girls and boys, but neither of these factors mediated the relationship between pubertal stage and health behaviours found in girls.Conclusions. These results suggest that the onset of puberty has a marked effect on the development of health behaviours. Puberty was related to an acceleration of the development of unhealthy behaviours, except for exercise behaviour in boys, where advanced puberty was associated with more exercise. These changes were unrelated to adolescent issues of stress and a causal explanation for these associations must be sought elsewhere

Human papillomavirus (HPV) information needs: a theoretical framework

Background With the introduction of human papillomavirus (HPV) testing and vaccination in the UK, health professionals will start to receive questions about the virus from their patients. This study aimed to identify the key questions about HPV that British women will ask when considering having an HPV test or vaccination.Methods Face-to-face interviews were carried out with 21 women to discover what they wanted to know about HPV. A thematic framework approach was used to analyse the data and identify key themes in women's HPV knowledge requirements.Results Women's questions about HPV fell into six areas: identity (e.g. What are the symptoms?), cause (e.g. How do you get HPV?), timeline (e.g. How long does it last?), consequences (e.g. Does it always cause cervical cancer?) and control-cure (e.g. Can you prevent infection?). In addition, they asked procedural questions about testing and vaccination (e.g. Where do I get an HPV test?). These mapped well onto the dimensions identified in Leventhal's description of Jay models of illness, called the 'Common Sense Model' (CSM).Discussion and conclusions These results indicated that the majority of the questions women asked about HPV fitted well into the CSM, which therefore provides a structure for women's information needs. The findings could help health professionals understand what questions they may be expected to answer. Framing educational materials using the CSM themes may also help health educators achieve a good fit with what the public want to know

Multi-Wavelength Study of Sgr A*: The Short Time Scale Variability

To understand the correlation and the radiation mechanism of flare emission in different wavelength bands, we have coordinated a number of telescopes to observe SgrA* simultaneously. We focus only on one aspect of the preliminary results of our multi-wavelength observing campaigns, namely, the short time scale variability of emission from SgrA* in near-IR, X-ray and radio wavelengths. The structure function analysis indicate most of the power spectral density is detected on hourly time scales in all wavelength bands. We also report minute time scale variability at 7 and 13mm placing a strong constraint on the nature of the variable emission. The hourly time scale variability can be explained in the context of a model in which the peak frequency of emission shifts toward lower frequencies as a self-absorbed synchrotron source expands adiabatically near the acceleration site. The short time scale variability, on the other hand, places a strong constraint on the size of the emitting region. Assuming that rapid minute time scale fluctuations of the emission is optically thick in radio wavelength, light travel arguments requires relativistic particle energy, thus suggesting the presence of outflow from SgrA*.Comment: 9 pages, 4 figures, The Galactic Center: A Window on the Nuclear Environment of Disk Galaxies ASP Conference Series, 2010 eds: M. Morris, D. Q. Wang and F. Yua

The Highest Redshift Relativistic Jets

We describe our efforts to understand large-scale (10's-100's kpc) relativistic jet systems through observations of the highest-redshift quasars. Results from a VLA survey search for radio jets in ~30 z>3.4 quasars are described along with new Chandra observations of 4 selected targets.Comment: 5 pages, 2 figures, to appear in Extragalactic Jets: Theory and Observation from Radio to Gamma Ray, Eds. T.A. Rector and D.S. De Youn

Soil methane sink capacity response to a long-term wildfire chronosequence in Northern Sweden

Boreal forests occupy nearly one fifth of the terrestrial land surface and are recognised as globally important regulators of carbon (C) cycling and greenhouse gas emissions. Carbon sequestration processes in these forests include assimilation of CO2 into biomass and subsequently into soil organic matter, and soil microbial oxidation of methane (CH4). In this study we explored how ecosystem retrogression, which drives vegetation change, regulates the important process of soil CH4 oxidation in boreal forests. We measured soil CH4 oxidation processes on a group of 30 forested islands in northern Sweden differing greatly in fire history, and collectively representing a retrogressive chronosequence, spanning 5000 years. Across these islands the build-up of soil organic matter was observed to increase with time since fire disturbance, with a significant correlation between greater humus depth and increased net soil CH4 oxidation rates. We suggest that this increase in net CH4 oxidation rates, in the absence of disturbance, results as deeper humus stores accumulate and provide niches for methanotrophs to thrive. By using this gradient we have discovered important regulatory controls on the stability of soil CH4 oxidation processes that could not have not been explored through shorter-term experiments. Our findings indicate that in the absence of human interventions such as fire suppression, and with increased wildfire frequency, the globally important boreal CH4 sink could be diminished

The impact of a health professional recommendation on weight loss attempts in overweight and obese British adults: a cross-sectional analysis

Objectives: To examine the effect that health professional (HP) advice to lose weight has on overweight and obese adults ’ motivation to lose weight and attempts to lose weight. Design: Cross-sectional survey. Setting: Great Britain. Participants: 810 overweight or obese (body mass index ≥ 25 kg/m 2 ) adults. Main outcome measures: Participants were asked if they had ever received HP advice to lose weight and reported their desire to weigh less (ideal weight ≤ 95% of current weight) and whether they were attempting to lose weight. Results: Only 17% of overweight and 42% of obese respondents recalled ever having received HP advice to lose weight. HP advice was associated with wanting to weigh less (89% vs 61% among those not receiving advice) and attempting to lose weight (68% vs 37%). In multivariable analyses, HP advice to lose weight was associated with increased odds of wanting to weigh less (OR=3.71, 95% CI 2.10 to 6.55) and attempting to lose weight (OR=3.53, 95% CI 2.44 to 5.10) independent of demographic characteristics and weight status. Conclusions: HP advice to lose weight appears to increase motivation to lose weight and weight loss behaviour, but only a minority of overweight or obese adults receive such advice. Better training for HPs in delivering brief weight counselling could offer an opportunity to improve obese patients ’ motivation to lose weight

Resistive jet simulations extending radially self-similar magnetohydrodynamic models

Numerical simulations with self-similar initial and boundary conditions provide a link between theoretical and numerical investigations of jet dynamics. We perform axisymmetric resistive magnetohydrodynamic (MHD) simulations for a generalised solution of the Blandford & Payne type, and compare them with the corresponding analytical and numerical ideal-MHD solutions. We disentangle the effects of the numerical and physical diffusivity. The latter could occur in outflows above an accretion disk, being transferred from the underlying disk into the disk corona by MHD turbulence (anomalous turbulent diffusivity), or as a result of ambipolar diffusion in partially ionized flows. We conclude that while the classical magnetic Reynolds number $R_{\rm m}$ measures the importance of resistive effects in the induction equation, a new introduced number, \rbeta=(\beta/2)R_{\rm m} with $\beta$ the plasma beta, measures the importance of the resistive effects in the energy equation. Thus, in magnetised jets with $\beta<2$, when \rbeta \la 1 resistive effects are non-negligible and affect mostly the energy equation. The presented simulations indeed show that for a range of magnetic diffusivities corresponding to \rbeta \ga 1 the flow remains close to the ideal-MHD self-similar solution.Comment: Accepted for publication in MNRA

Pulmonary nodules and CT screening: the past, present and future

Lung cancer screening has come a long way since the early studies with chest X-ray. Advancing technology and progress in the processing of images have enabled low dose CT to be tried and tested, and evidence suggests its use can result in a significant mortality benefit. There are several issues that need refining in order to successfully implement screening in the UK and elsewhere. Some countries have started patchy implementation of screening and there is increased recognition that the appropriate management of pulmonary nodules is crucial to optimise benefits of early detection, while reducing harm caused by inappropriate medical intervention. This review summarises and differentiates the many recent guidelines on pulmonary nodule management, discusses screening activity in other countries and exposes the present barriers to implementation in the UK