A Bayesian approach to the estimation of maps between riemannian manifolds

Let \Theta be a smooth compact oriented manifold without boundary, embedded in a euclidean space and let \gamma be a smooth map \Theta into a riemannian manifold \Lambda. An unknown state \theta \in \Theta is observed via X=\theta+\epsilon \xi where \epsilon>0 is a small parameter and \xi is a white Gaussian noise. For a given smooth prior on \Theta and smooth estimator g of the map \gamma we derive a second-order asymptotic expansion for the related Bayesian risk. The calculation involves the geometry of the underlying spaces \Theta and \Lambda, in particular, the integration-by-parts formula. Using this result, a second-order minimax estimator of \gamma is found based on the modern theory of harmonic maps and hypo-elliptic differential operators.Comment: 20 pages, no figures published version includes correction to eq.s 31, 41, 4

Challenging empowerment: AIDS-affected southern African children and the need for a multi-level relational approach

Critics of empowerment have highlighted the concept's mutability, focus on individual transformation, one-dimensionality and challenges of operationalisation. Relating these critiques to children's empowerment raises new challenges. Drawing on scholarship on children's subjecthood and exercise of power, alongside empirical research with children affected by AIDS, I argue that empowerment envisaged as individual self-transformation and increased capacity to act independently offers little basis for progressive change. Rather it is essential to adopt a relational approach that recognises the need to transform power relationships at multiple levels. This analysis has implications for our wider understanding of empowerment in the 21st century. © The Author(s) 2013.This research was funded by DFID

Subjectivation and performative politics—Butler thinking Althusser and Foucault: intelligibility, agency and the raced-nationed-religioned subjects of education

Judith Butler is perhaps best known for her take-up of the debate between Derrida and Austin over the function of the performative and her subsequent suggestion that the subject be understood as performatively constituted. Another important but less often noted move within Butler‘s consideration of the processes through which the subject is constituted is her thinking between Althusser‘s notion of subjection and Foucault‘s notion of subjectivation. In this paper, I explore Butler‘s understanding of processes of subjectivation; examine the relationship between subjectivation and the performative suggested in and by Butler‘s work, and consider how the performative is implicated in processes of subjectivation – in =who‘ the subject is, or might be, subjectivated as. Finally, I examine the usefulness of understanding the subjectivating effects of discourse for education, in particular for educationalists concerned to make better sense of and interrupt educational inequalities. In doing this I offer a reading of an episode of ethnographic data generated in an Australian high School. I suggest that it is through subjectivating processes of the sort that Butler helps us to understand that some students are rendered subjects inside the educational endeavour, and others are rendered outside this endeavour or, indeed, outside student-hood

Trouble at the top: The construction of a tenant identity in the governance of social housing organizations

The project of citizen governance has transformed the social housing sector in England where 20,000 tenants now sit as directors on the boards of housing associations, but the entrance of social housing tenants to the boardroom has aroused opposition from the chief executives of housing companies and triggered regulatory intervention from government inspectors. This paper investigates the cause of these tensions through a theoretical framework drawn from the work of feminist philosopher Judith Butler. It interprets housing governance as an identificatory project with the power to constitute tenant directors as regulated subjects, and presents evidence to suggest that this project of identity fails to completely enclose its subject, allowing tenant directors to engage in ‘identity work’ that threatens the supposed unity of the board. The paper charts the development of antagonism and political tension in the board rooms of housing companies to present an innovative account of the construction and contestation of identities in housing governance

'When I click "ok" I become Sassy – I become a girl.' Young people and gender identity: Subverting the ‘body’ in massively multi-player online role-playing games

This article is available open access through the publisher’s website through the link below. Copyright @ 2012 Taylor & Francis.This article explores young people's practices in the virtual spaces of online gaming communities. Based on a five-year ethnographic study of virtual worlds, it considers how young people construct and maintain identities within virtual social systems. In particular, the article discusses digital gender practices and considers the potential that these games offer for their young users to engage in alternate gender identities. We argue that these digital spaces offer spaces for the imagination and can enhance agency and, potentially, resistance. However, digital identity is simultaneously no ‘liberated space’ and it incorporates norms and practices that often mirror those of the material world. We argue that this ‘porosity’ is an important tool through which young people come to understand gender identity

Measuring surface-area-to-volume ratios in soft porous materials using laser-polarized xenon interphase exchange NMR

We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables determination of the surface-area-to-volume ratio (S/V) of soft porous materials from measurements of the diffusive exchange of laser-polarized 129Xe between gas in the pore space and 129Xe dissolved in the solid phase. We apply this NMR technique to porous polymer samples and find approximate agreement with destructive stereological measurements of S/V obtained with optical confocal microscopy. Potential applications of laser-polarized xenon interphase exchange NMR include measurements of in vivo lung function in humans and characterization of gas chromatography columns.Comment: 14 pages of text, 4 figure

The Photophysical Properties of CdTe/ZnS Core/Shell Quantum Dots

The distinctive fluorescent properties of semiconductor nanocrystal quantum dots (QDs) make them advantageous for use in optoelectronic and biological applications. We report on experiments done to characterize the optical properties and the general photostability of CdTe QDs with varying ZnS shell thicknesses. Steady-state and time-resolved absorption and fluorescence spectroscopy measurements indicate that increasing the ZnS shell thickness results in longer absorption and emission wavelengths, increased quantum yield, and improved photostability.Faculty Sponsor: Dr. James J. Butler and Dr. David Corde

Social media, protest cultures and political subjectivities of the Arab spring

This article draws on phenomenological perspectives to present a case against resisting the objectification of cultures of protest and dissent. The generative, self-organizing properties of protest cultures, especially as mobilized through social media, are frequently argued to elude both authoritarian political structures and academic discourse, leading to new political subjectivities or ‘imaginaries’. Stemming from a normative commitment not to over-determine such nascent subjectivities, this view has taken on a heightened resonance in relation to the recent popular uprisings in the Middle East and North Africa. The article argues that this view is based on an invalid assumption that authentic political subjectivities and cultures naturally emerge from an absence of constraint, whether political, journalistic or academic. The valorisation of amorphousness in protest cultures and social media enables affective and political projection, but overlooks politics in its institutional, professional and procedural forms