Fluid-loaded metasurfaces

We consider wave propagation along fluid-loaded structures which take the form of an elastic plate augmented by an array of resonators forming a metasurface, that is, a surface structured with sub-wavelength resonators. Such surfaces have had considerable recent success for the control of wave propagation in electromagnetism and acoustics, by combining the vision of sub-wavelength wave manipulation, with the design, fabrication and size advantages associated with surface excitation. We explore one aspect of recent interest in this field: graded metasurfaces, but within the context of fluid-loaded structures. Graded metasurfaces allow for selective spatial frequency separation and are often referred to as exhibiting rainbow trapping. Experiments, and theory, have been developed for acoustic, electromagnetic, and even elastic, rainbow devices but this has not been approached for fluid-loaded structures that support surface waves coupled with the acoustic field in a bulk fluid. This surface wave, coupled with the fluid, can be used to create an additional effect by designing a metasurface to mode convert from surface to bulk waves. We demonstrate that sub-wavelength control is possible and that one can create both rainbow trapping and mode conversion phenomena for a fluid-loaded elastic plate model.Comment: 13 pages, 10 figure

Short time-scale optical variability of the dwarf Seyfert nucleus in NGC 4395

We present optical spectroscopic observations of the least-luminous known Seyfert 1 galaxy, NGC 4395, which was monitored every half-hour over the course of 3 nights. The continuum emission varied by ~35 per cent over the course of 3 nights, and we find marginal evidence for greater variability in the blue continuum than the red. A number of diagnostic checks were performed on the data in order to constrain any systematic or aperture effects. No correlations were found that adequately explained the observed variability, hence we conclude that we have observed real intrinsic variability of the nuclear source. No simultaneous variability was measured in the broad H-beta line, although given the difficulty in deblending the broad and narrow components it is difficult to comment on the significance of this result. The observed short time-scale continuum variability is consistent with NGC 4395 having an intermediate-mass (~10^5 solar masses) central supermassive black hole, rather than a very low accretion rate. Comparison with the Seyfert 1 galaxy NGC 5548 shows that the observed variability seems to scale with black hole mass in roughly the manner expected in accretion models. However the absolute time-scale of variability differs by several orders of magnitude from that expected in simple accretion disc models in both cases.Comment: 16 pages, 14 figures, 5 tables, accepted for publication in MNRA

Childhood and the politics of scale: Descaling children's geographies?

This is the post-print version of the final published paper that is available from the link below. Copyright @ 2008 SAGE Publications.The past decade has witnessed a resurgence of interest in the geographies of children's lives, and particularly in engaging the voices and activities of young people in geographical research. Much of this growing body of scholarship is characterized by a very parochial locus of interest — the neighbourhood, playground, shopping mall or journey to school. In this paper I explore some of the roots of children's geographies' preoccupation with the micro-scale and argue that it limits the relevance of research, both politically and to other areas of geography. In order to widen the scope of children's geographies, some scholars have engaged with developments in the theorization of scale. I present these arguments but also point to their limitations. As an alternative, I propose that the notion of a flat ontology might help overcome some difficulties around scalar thinking, and provide a useful means of conceptualizing sociospatiality in material and non-hierarchical terms. Bringing together flat ontology and work in children's geographies on embodied subjectivity, I argue that it is important to examine the nature and limits of children's spaces of perception and action. While these spaces are not simply `local', they seldom afford children opportunities to comment on, or intervene in, the events, processes and decisions that shape their own lives. The implications for the substance and method of children's geographies and for geographical work on scale are considered

Targeting Mr Average: Participation, gender equity and school sport partnerships

The School Sport Partnership Programme (SSPP) is one strand of the national strategy for physical education and school sport in England, the physical education and school sport Club Links Strategy (PESSCL). The SSPP aims to make links between school physical education (PE) and out of school sports participation, and has a particular remit to raise the participation levels of several identified under-represented groups, of which girls and young women are one. National evaluations of the SSPP show that it is beginning to have positive impacts on young people's activity levels by increasing the range and provision of extra curricular activities (Office for Standards in Education (OFSTED), 2003, 2004, 2005; Loughborough Partnership, 2005, 2006). This paper contributes to the developing picture of the phased implementation of the programme by providing qualitative insights into the work of one school sport partnership with a particular focus on gender equity. The paper explores the ways in which gender equity issues have been explicitly addressed within the 'official texts' of the SSPP; how these have shifted over time and how teachers are responding to and making sense of these in their daily practice. Using participation observation, interview and questionnaire data, the paper explores how the coordinators are addressing the challenge of increasing the participation of girls and young women. The paper draws on Walby's (2000) conceptualisation of different kinds of feminist praxis to highlight the limitations of the coordinators' work. Two key themes from the data and their implications are addressed: the dominance of competitive sport practices and the PE professionals' views of targeting as a strategy for increasing the participation of under-represented groups. The paper concludes that coordinators work within an equality or difference discourse with little evidence of the transformative praxis needed for the programme to be truly inclusive. © 2008 Taylor & Francis

Alfred Werner revisited: Some subtleties of complex ion synthesis and isomerism

The synthesis of perhaps the best-known Wernerian complex, [Co(en)3]3+, is very efficient, but nonetheless results in the formation of various side-products. Today, the use of X-ray crystallography to characterise such materials provides new insights into the reaction pathways of the synthesis and the exact forms possible for the products. The structures of cis-[Co(en)2(H2NCH2CH2NH3)Cl]Cl[ZnCl4], cis-[Co(en)2(NH3)Cl]S2O6, [Co(en)(NH2CH2CH2N=CHCH2NH2))Cl][ZnCl4], [Co(en)2(N-CH3en)][Co(CN)6]?2 H2O and [Co(en)2(N-CH3en)][Co(CN)6], are presently discussed in this regard

Development and delivery of an exercise programme for falls prevention: the Prevention of Falls Injury Trial (PreFIT)

This paper describes the development and implementation of an exercise intervention to prevent falls within The Prevention of Fall Injury Trial (PreFIT), which is a large multi-centred randomised controlled trial based in the UK National Health Service (NHS).Using the template for intervention description and replication (TIDieR) checklist, to describe the rationale and processes for treatment selection and delivery of the PreFIT exercise intervention.Based on the results of a validated falls and balance survey, participants were eligible for the exercise intervention if they were at moderate or high risk of falling.Intervention development was informed using the current evidence base, published guidelines, and pre-existing surveys of clinical practice, a pilot study and consensus work with therapists and practitioners. The exercise programme targets lower limb strength and balance, which are known, modifiable risk factors for falling. Treatment was individually tailored and progressive, with seven recommended contacts over a six-month period. Clinical Trials Registry (ISCTRN 71002650)

Knowledge about foot-specific foot falls risk factors and exercise among physiotherapists in the UK and Portugal: a cross-sectional survey

BACKGROUND AND PURPOSE: Foot‐related falls risk factors and specific foot and ankle exercise interventions are within the scope of Physiotherapy, yet little is known about United Kingdom (UK) and Portugal‐based (PT) physiotherapists' self‐perceived knowledge, confidence and practice of such interventions, or perceptions of patients' falls prevention knowledge. The purpose of this study was to assess levels of self‐reported knowledge, confidence, and practices surrounding foot‐specific falls risk and exercise for fall prevention in physiotherapists working in the UK and in Portugal. It also aimed to explore physiotherapists' views about their participants' falls prevention knowledge. METHODS: A self‐report online survey was developed, and pilot tested in both nations. Registered Physiotherapists were invited to participate through their professional associations, social media and snowballing. Mann‐Whitney tests were used to compare mean ranks of ordinal variables between nations and Chi‐square test to assess the independency between pairs of variables. Spearman's correlation coefficient (rs) was used to measure the association between pairs of variables (p < 0.05). RESULTS: 682 physiotherapists participated in the survey [UK n = 229 (mean (SD) age = 43(10) years, 86.9% female]; PT n = 453 (mean (SD) age = 33(9) years, 78.3% female]. Among physiotherapists with a caseload of ≥70% older adults, more PT‐based physiotherapists held postgraduate qualifications (p = 0.01). Most physiotherapists correctly identified generic and foot‐specific risk factors (≥70% of participants for each item). More UK‐based physiotherapists reported always prescribing ankle and foot exercises (42.6% vs. 33%, p =< 0.001) and displayed higher levels of self‐reported confidence surrounding exercise‐based interventions. DISCUSSION: Our sample of UK and Portugal‐based physiotherapists are aware of the contribution of foot‐specific risk factors and exercise to falls prevention, with the former group being more confident in exercise‐based interventions. Both groups of physiotherapists perceived that their older patients had little knowledge about these topics, with UK older adults having slightly better knowledge on generic falls risk factors at first contact. Future studies and strategies for knowledge translation and education in foot health and foot function screening and management for physiotherapists, within a falls prevention scope, may be informed by this study