The most massive galaxies in clusters are already fully grown at z∼0.5z \sim 0.5

By constructing scaling relations for galaxies in the massive cluster MACSJ0717.5 at $z=0.545$ and comparing with those of Coma, we model the luminosity evolution of the stellar populations and the structural evolution of the galaxies. We calculate magnitudes, surface brightnesses and effective radii using HST/ACS images and velocity dispersions using Gemini/GMOS spectra, and present a catalogue of our measurements for 17 galaxies. We also generate photometric catalogues for $\sim 3000$ galaxies from the HST imaging. With these, we construct the colour-magnitude relation, the fundamental plane, the mass-to-light versus mass relation, the mass-size relation and the mass-velocity dispersion relation for both clusters. We present a new, coherent way of modelling these scaling relations simultaneously using a simple physical model in order to infer the evolution in luminosity, size and velocity dispersion as a function of redshift, and show that the data can be fully accounted for with this model. We find that (a) the evolution in size and velocity dispersion undergone by these galaxies between $z \sim 0.5$ and $z \sim 0$ is mild, with $R_e(z) \sim (1+z)^{-0.40\pm0.32}$ and $\sigma(z) \sim (1+z)^{0.09 \pm 0.27}$, and (b) the stellar populations are old, $\sim 10$ Gyr, with a $\sim 3$ Gyr dispersion in age, and are consistent with evolving purely passively since $z \sim 0.5$ with $\Delta \log M/L_B = -0.55_{-0.07}^{+0.15} z$. The implication is that these galaxies formed their stars early and subsequently grew dissipationlessly so as to have their mass already in place by $z \sim 0.5$, and suggests a dominant role for dry mergers, which may have accelerated the growth in these high-density cluster environments.Comment: 20 pages; accepted for publication in MNRA

Development and use of an extensometer for determining the mechanical compliance of crack toughness test specimens

Extensometer for determining mechanical compliance of crack toughness test specimen

Electrical charging of ash in Icelandic volcanic plumes

The existence of volcanic lightning and alteration of the atmospheric potential gradient in the vicinity of near-vent volcanic plumes provides strong evidence for the charging of volcanic ash. More subtle electrical effects are also visible in balloon soundings of distal volcanic plumes. Near the vent, some proposed charging mechanisms are fractoemission, triboelectrification, and the so-called "dirty thunderstorm" mechanism, which is where ash and convective clouds interact electrically to enhance charging. Distant from the vent, a self-charging mechanism, probably triboelectrification, has been suggested to explain the sustained low levels of charge observed on a distal plume. Recent research by Houghton et al. (2013) linked the self-charging of volcanic ash to the properties of the particle size distribution, observing that a highly polydisperse ash distribution would charge more effectively than a monodisperse one. Natural radioactivity in some volcanic ash could also contribute to self-charging of volcanic plumes. Here we present laboratory measurements of particle size distributions, triboelectrification and radioactivity in ash samples from the Gr\'{i}msv\"{o}tn and Eyjafjallaj\"{o}kull volcanic eruptions in 2011 and 2010 respectively, and discuss the implications of our findings.Comment: XV Conference on Atmospheric Electricity, 15-20 June 2014, Norman, Oklahoma, US

Why the Universe Started from a Low Entropy State

We show that the inclusion of backreaction of massive long wavelengths imposes dynamical constraints on the allowed phase space of initial conditions for inflation, which results in a superselection rule for the initial conditions. Only high energy inflation is stable against collapse due to the gravitational instability of massive perturbations. We present arguments to the effect that the initial conditions problem {\it cannot} be meaningfully addressed by thermostatistics as far as the gravitational degrees of freedom are concerned. Rather, the choice of the initial conditions for the universe in the phase space and the emergence of an arrow of time have to be treated as a dynamic selection.Comment: 12 pages, 2 figs. Final version; agrees with accepted version in Phys. Rev.

Young people and organised outdoor activities: a study of opportunities in national parks

This thesis examines young people's opportunities to participate in organised outdoor activities. It is set within a context of changing leisure interests, a growth in private sector leisure provision, and increasing emphasis on consumer choice. It argues that whilst, in principle, there is widespread support for young people's participation in outdoor activities, in practice, opportunities are becoming increasingly limited. The study aims to examine the nature of outdoor facilities, to determine their use by young people, to identify changes occurring within the outdoor sector, and to consider the changes in relation to young people's access to the outdoors. The empirical research focuses~ on outdoor activity centres, in acknowledgement that the residential experience offered by such centres can contribute to the social and personal development of young people. It also focuses on the National Parks of England and Wales. These areas possess a wealth of natural resources suitable for a wide range of outdoor activities and, collectively, contain the highest number of outdoor centres in the UK. A combination of quantitative and qualitative methods of data collection, including a questionnaire survey of outdoor centres, interviews with centre operators, and a review of National Park policies, has been used to build up a picture of centre operations, visitor profiles, and the nature of outdoor programmes. The study findings suggest that a number of factors influence young people's opportunities to participate in outdoor activities. These include centre ownership, safety and educational reforms, planning and environmental policies, and young people's leisure behaviour. Recent years have seen a significant growth in privately owned centres and an associated rise in skills-based activities and non-sporting special interest holidays. These programmes have been largely directed at the adult market. There are few indications that this pattern is about to change. Regulation of the outdoor industry, including safety licensing, has put increasing pressures on under-resourced centres and has led to readjustments in centre operations and in the profile of visitor groups. Young people's opportunities to take part in adventurous activities, as a result of safety licensing, have diminished. Educational reforms have further dictated the direction of outdoor courses. Since the late 1980s, there has been a marked increase in primary school visits to outdoor centres and in field studies, whilst secondary schools visits and involvement in physical pursuits have continued to decline. Centre diversification has led to an overall reduction in the number of places available for young people. Planning and environmental policies have shaped the pattern of centre development. The emphasis on environmental protection in the National Parks has led to constraints on outdoor provision although policies, across Parks, vary. Changes in young people's lifestyles have also begun to impact upon the content of outdoor courses, such as the demand for more varied programmes and less traditional activities. Sporting and recreational organisations can, by addressing factors of motivation, play. a significant role in increasing levels of participation. Given the dynamics of the outdoor industry, the relative importance of these factors is difficult to determine, although the provisions of the Education Reform Act 1988 have induced some of the most radical and widespread changes within the outdoor sector in recent years. In trying to encourage and assist young people to take up outdoor opportunities, the outdoor community faces a number of difficulties. These include a lack of cohesion and .. poor image, increasing commercialisation, and the effects of changing leisure interests. The thesis recommends greater collaboration within the community, possibly through a new organisation, to represent a wider range of interests and to act as a more effective lobbying mechanism. It also recommends a strengthening of the links between the outdoor sector and the key players involved in facilitating outdoor opportunities. Finally, it advises organisations to take heed of newly emerging Government statements on out-of-school learning. These may offer viable alternatives to help safeguard young people's opportunities to participate in outdoor activities

Improving health behaviours and outcomes: An intervention to support engagement in physical activity

The purpose of this case study is to offer reflections on the personal experiences, processes of behavioural change; and subsequent outcomes of designing and implementing a collaborative exercise psychology intervention. The intervention, based on Bandura’s (1977) Self Efficacy Theory and using self-efficacy related behaviour change techniques (Michie et al., 2015), aimed to provide families affected by health inequalities with opportunities to enhance their understanding of health and make positive behavioural changes. This case is based around one female client aged 48 years of age who took part in the project with her ten-year-old daughter. Pre- intervention the client was engaging in minimal levels of weekly physical activity and reported poor self-rated mental well-being. Through improvements in self-efficacy, achieved through opportunities on the project, the client was able to make notable improvements to her physical activity levels leading to significant weight loss and improvements in mental well-being. From the practitioners’ perspective, reflection on areas for future work within the field of exercise psychology, particularly guidance on developing effective client-practitioner relationships with ‘hard-to-reach’ individuals and groups is warranted. More consideration for the suitability of the PA guidelines for individuals with poor physical and mental health is also required