The effect of the equivalent-weights particle filter on dynamical balance in a primitive equation model

The disadvantage of the majority of data assimilation schemes is the assumption that the conditional probability density function of the state of the system given the observations [posterior probability density function (PDF)] is distributed either locally or globally as a Gaussian. The advantage, however, is that through various different mechanisms they ensure initial conditions that are predominantly in linear balance and therefore spurious gravity wave generation is suppressed. The equivalent-weights particle filter is a data assimilation scheme that allows for a representation of a potentially multimodal posterior PDF. It does this via proposal densities that lead to extra terms being added to the model equations and means the advantage of the traditional data assimilation schemes, in generating predominantly balanced initial conditions, is no longer guaranteed. This paper looks in detail at the impact the equivalent-weights particle filter has on dynamical balance and gravity wave generation in a primitive equation model. The primary conclusions are that (i) provided the model error covariance matrix imposes geostrophic balance, then each additional term required by the equivalent-weights particle filter is also geostrophically balanced; (ii) the relaxation term required to ensure the particles are in the locality of the observations has little effect on gravity waves and actually induces a reduction in gravity wave energy if sufficiently large; and (iii) the equivalent-weights term, which leads to the particles having equivalent significance in the posterior PDF, produces a change in gravity wave energy comparable to the stochastic model error. Thus, the scheme does not produce significant spurious gravity wave energy and so has potential for application in real high-dimensional geophysical applications.

Rethinking disability theory and practice: challenging essentialism

This edited volume argues that even in recent Critical Disability Studies which have sought to critique essentialist assumptions in relation to Disability, nevertheless essentialisms remain which predetermine and predirect definitions and arguments in the field. This volume analyses such essentialisms in a wide range of areas such as childhood, gender, sexuality, reproduction, ADHD, autism, the animal, d/Deafness, hirsutism, the body, and vision. Particularly issues such as 'agency', 'voice' and 'body' are explored in terms of their political implications.

Twin experiments with the equivalent weights particle filter and HadCM3

This paper investigates the use of a particle filter for data assimilation with a full scale coupled ocean–atmosphere general circulation model. Synthetic twin experiments are performed to assess the performance of the equivalent weights filter in such a high-dimensional system. Artificial 2-dimensional sea surface temperature fields are used as observational data every day. Results are presented for different values of the free parameters in the method. Measures of the performance of the filter are root mean square errors, trajectories of individual variables in the model and rank histograms. Filter degeneracy is not observed and the performance of the filter is shown to depend on the ability to keep maximum spread in the ensemble.

Effects of forage source and extruded linseed supplementation on methane emissions from growing dairy cattle of differing body weights

Changes in diet carbohydrate amount and type (i.e., starch vs. fiber) and dietary oil supplements can affect ruminant methane emissions. Our objectives were to measure methane emissions, whole-tract digestibility, and energy and nitrogen utilization from growing dairy cattle at 2 body weight (BW) ranges, fed diets containing either high maize silage (MS) or high grass silage (GS), without or with supplemental oil from extruded linseed (ELS). Four Holstein-Friesian heifers aged 13 mo (BW range from start to finish of 382 to 526 kg) were used in experiment 1, whereas 4 lighter heifers aged 12 mo (BW range from start to finish of 292 to 419 kg) were used in experiment 2. Diets were fed as total mixed rations with forage dry matter (DM) containing high MS or high GS and concentrates in proportions (forage:concentrate, DM basis) of either 75:25 (experiment 1) or 60:40 (experiment 2), respectively. Diets were supplemented without or with ELS (Lintec[AU1: Add manufacturer name and location.]; 260 g of oil/ kg of DM) at 6% of ration DM. Each experiment was a 4 × 4 Latin square design with 33-d periods, with measurements during d 29 to 33 while animals were housed in respiration chambers. Heifers fed MS at a heavier BW (experiment 1) emitted 20% less methane per unit of DM intake (yield) compared with GS (21.4 vs. 26.6, respectively). However, when repeated with heifers of a lower BW (experiment 2), methane yield did not differ between the 2 diets (26.6 g/kg of DM intake). Differences in heifer BW had no overall effect on methane emissions, except when expressed as grams per kilogram of digestible organic matter (OMD) intake (32.4 vs. 36.6, heavy vs. light heifers). Heavier heifers fed MS in experiment 1 had a greater DM intake (9.4 kg/d) and lower OMD (755 g/kg), but no difference in N utilization (31% of N intake) compared with heifers fed GS (7.9 kg/d and 799 g/kg, respectively). Tissue energy retention was nearly double for heifers fed MS compared with GS in experiment 1 (15 vs. 8% of energy intake, respectively). Heifers fed MS in experiment 2 had similar DM intake (7.2 kg/d) and retention of energy (5% of intake energy) and N (28% of N intake), compared with GS-fed heifers, but OMD was lower (741 vs. 765 g/kg, respectively). No effect of ELS was noted on any of the variables measured, irrespective of animal BW, and this was likely due to the relatively low amount of supplemental oil provided. Differences in heifer BW did not markedly influence dietary effects on methane emissions. Differences in methane yield were attributable to differences in dietary starch and fiber composition associated with forage type and source.

Care, disability and HIV in Africa: diverging or interconnected concepts and practices?

Recent research and policy have recognised the central role of unpaid care-givers (often women and girls) in the global South. Disability rights perspectives, however, challenge the language of ‘care’ and ‘dependence’. Drawing on qualitative research with women living with HIV and children caring for them in Tanzania, and on learning from the National Community of Women Living with HIV and AIDS in Uganda (NACWOLA), this paper explores the divergences and interconnections between the concepts and practices of care, disability and HIV in the context of East Africa. Despite the development of interdependent caring relations, both care-givers and people living with HIV in Tanzania experience ‘diminished autonomy’. The participation of people living with HIV, including disabled people, in home-based care and in peer support groups, however, can enhance ‘relational autonomy’ for both care-givers and care-recipients. We reflect on opportunities and challenges for mutual learning and cross-movement advocacy by disabled people, people living with HIV and care-givers.

Looking back, moving forward: drama, disability and social justice

The aim of this chapter is to briefly outline how disability has been represented in theatre, what access disabled people have had to drama and theatre in the past, and what might be achieved in the pursuit of social justice with young people in relation to awareness of and provision for disability. It will focus in particular on how disability has been addressed in drama education and what assumptions have been made regarding drama and disability in education. In considering such issues one might perceive manifestations of what Freebody and Finneran (2013) recognise as an overlapping and ‘somewhat artificially created dichotomy between drama for social justice and drama about social justice.’ This chapter will examine some examples of how drama has been used to give students in mainstream schools insights into disability, and the philosophy that underpins the drama curriculum of one special school where the focus is on drama as social justice: the argument being that in some cases simply doing drama is, in effect, a manifestation of social justice. Finally, some of the progress made in recent years regarding access and engagement will be addressed through specific reference to the authors’ on-going work into ‘performing social research’ (Shah, 2013) and how theatres are increasingly attempting to give more access to disabled young people and their families by offering ‘relaxed performances.’

Disability [sport] and discourse: stories within the Paralympic legacy

This paper aims to encourage critical reflection on what are key and pressing social and political issues surrounding the Paralympics Games. The focus of the paper is personal narratives of six current elite Paralympic athletes who have participated in at least one Paralympic Games. In response to critical stimuli presented in the form of five ‘unfinished stories’, the self-reflexive, personal, compelling narrative reflections of these individuals were (re)presented for each of the stories as a composite narrative. The stories expose questions over fear, despair, freedom, hope, love, oppression, hatred, hurt, terror, (in)equality, peace, performance and impairment. To really learn from London and reflect for Rio, we need academic work that can understand sport, sporting bodies and physical activity as important ‘sites’ through which social forces, discourses, institutions and processes congregate, congeal and are contested in a manner that contributes to the shaping of human relations, subjectivities, and experiences in particular, contextually contingent ways.

The use and usefulness of a parent questionnaire to help schools identify disability

The Equality Act 2010 will be implemented in full in 2011, and schools in the UK will have to provide special aids or services for children with disabilities where this provision is considered reasonable. This paper reports on staff perspectives on the use and usefulness of a parental questionnaire on disability from a sample of 49 schools (mainstream and special) located in 12 local authorities. Most schools found the process of administering the parent questionnaire undemanding; just under half of the sample indicated that they would take some action as a result of the data collected from the parental questionnaire (e.g., to inform plans for targeting or monitoring support for children, and to contact parents and follow-up issues they had mentioned); and about one-third of schools recorded unanticipated findings from the parental questionnaire, that is, the identification of children whose disabilities were not previously known to the school. Implications for schools are discussed.

Collecting disability data from parents

This article describes the development and national trial of a methodology for collecting disability data directly from parents, enabling schools and local authorities to meet their obligations under the Disability Discrimination Act (DDA; 2005) to promote equality of opportunity for all children. It illustrates the complexities around collecting this information and also highlights the dangers of assuming that special educational needs (SENs) equate to disability. The parental survey revealed children with medical and mental health needs, but no SENs, who were unknown to schools. It also revealed children with a recorded SEN whose parents did not consider that they had a disability in line with the DDA definition. It identified a number of children whose disability leads to absences from school, making them vulnerable to underachievement. These findings highlight the importance of having appropriate tools with which to collect these data and developing procedures to support their effective use. We also draw attention to the contextual nature of children’s difficulties and the importance of retaining and respecting the place of subjective information. This is central to adopting a definition of disability that hinges on experience or impact.

Testing of disability identification tool for schools

There has been an ongoing concern about the lack of reliable data on disabled children in schools. To date there has been no consistent way of identifying and categorising disabilities. Schools in England are currentlyrequired to collect data on children with Special Educational Need (SEN), but this does not capture information about all disabled children. The lack of this information may seriously restrict capacity at all levels of policy and practice to understand and respond to the needs of disabled children and their families in line with Disability Discrimination Act (2005) and the single Equality Act (2010). The aim of the project was to test the draft tools for identifying disability and accompanying guidance in a sample of all types of maintained schools in order to assess their usability and reliability and whether they resulted in the generation of robust and consistent data that could reliably inform school returns for the annual School Census.

Disability data collection for children's services

Schools need to identify disabled pupils in accordance with their Disability Equality Duty. This research assisted in the development of suitable tools to allow them to identify disabled children in accordance with the definition set out in the Disability Discrimination Act (DDA) by surveying parents and, via the use of purpose-designed activities, the children themselves.

The recuperated materiality of disability and animal studies

This chapter considers a perhaps unexpected connection between disability and animal studies, given disability studies' understandable reluctance to be associated with animal liberation/rights struggles. It finds that both fields remain rooted in ideas of experience and feeling, or the notion of an essential embodied experience, even while they offer up critiques of the way essentialism operates more broadly to disenfranchise or disadvantage the groups they represent. The chapter goes on to analyse what the implications are of this notion of 'embodiment' and the materialism that accompanies it, it foregrounds the contradictions that ensue, and then discusses what this means for the way political action is (and can be) conceived of.

Implicit equal-weights particle filter

Filter degeneracy is the main obstacle for the implementation of particle filter in non-linear high-dimensional models. A new scheme, the implicit equal-weights particle filter (IEWPF), is introduced. In this scheme samples are drawn implicitly from proposal densities with a different covariance for each particle, such that all particle weights are equal by construction. We test and explore the properties of the new scheme using a 1,000-dimensional simple linear model, and the 1,000-dimensional non-linear Lorenz96 model, and compare the performance of the scheme to a Local Ensemble Kalman Filter. The experiments show that the new scheme can easily be implemented in high-dimensional systems and is never degenerate, with good convergence properties in both systems.