Interaction induced dimerization in zigzag single wall carbon nanotubes

We derive a low-energy effective model of metallic zigzag carbon nanotubes at half filling. We show that there are three important features characterizing the low-energy properties of these systems: the long-range Coulomb interaction, umklapp scattering and an explicit dimerization generated by interactions. The ratio of the dimerization induced gap and the Mott gap induced by the umklapp interactions is dependent on the radius of the nanotube and can drive the system through a quantum phase transition with SU(2)_1 quantum symmetry. We consider the physical properties of the phases on either side of this transition which should be relevant for realistic nanotubes.Comment: 8 pages, 5 figure

Strong correlation effects in single-wall carbon nanotubes

We present an overview of strong correlations in single-wall carbon nanotubes, and an introduction to the techniques used to study them theoretically. We concentrate on zigzag nanotubes, although universality dictates that much ofthe theory can also be applied to armchair or chiral nanotubes. We show how interaction effects lead to exotic low energy properties and discuss future directions for studies on correlation effects in nanotubes

Massive vector fields on the Schwarzschild spacetime: quasinormal modes and bound states

We study the propagation of a massive vector or Proca field on the Schwarzschild spacetime. The field equations are reduced to a one-dimensional wave equation for the odd-parity part of the field and two coupled equations for the even-parity part of the field. We use numerical techniques based on solving (scalar or matrix-valued) three-term recurrence relations to compute the spectra of both quasi-normal modes and quasi-bound states, which have no massless analogue, complemented in the latter case by a forward-integration method. We study the radial equations analytically in both the near-horizon and far-field regions and use a matching procedure to compute the associated spectra in the small-mass limit. Finally, we comment on extending our results to the Kerr geometry and its phenomenological relevance for hidden photons arising e.g. in string theory compactifications.Comment: 15 pages, 8 figures; minor corrections, to be published in Phys. Rev.

The effect of a local perturbation in a fermionic ladder

We study the effect of a local external potential on a system of two parallel spin-polarized nanowires placed close to each other. For single channel nanowires with repulsive interaction we find that transport properties of the system are highly sensitive to the transverse gradient of the perturbation: the asymmetric part completely reflects the electrons leading to vanishing conductance at zero temperature, while the flat potential remains transparent. We envisage a possible application of this unusual property in the sensitive measurement of local potential field gradients.Comment: 4+ pages, 2 figures, typos correcte

Pay More Attention : a national mixed methods study to identify the barriers and facilitators to ensuring equal access to high-quality hospital care and services for children and young people with and without learning disabilities and their families

INTRODUCTION: Despite evidence of health inequalities for adults with intellectual disability (ID) there has yet to be a comprehensive review of how well hospital services are meeting the needs of children and young people (CYP) with ID and their families. We do not know how relevant existing recommendations and guidelines are to CYP, whether these are being applied in the paediatric setting or what difference they are making. Evidence of parental dissatisfaction with the quality, safety and accessibility of hospital care for CYP with ID exists. However, the extent to which their experience differs from parents of CYP without ID is not known and the views and experiences of CYP with ID have not been investigated. We will compare how services are delivered to, and experienced by CYP aged 5–15 years with and without ID and their families to see what inequalities exist, for whom, why and under what circumstances. METHODS AND ANALYSIS: We will use a transformative, mixed methods case study design to collect data over four consecutive phases. We will involve CYP, parents and hospital staff using a range of methods; interviews, parental electronic diary, hospital and community staff questionnaire, patient and parent satisfaction questionnaire, content analysis of hospital documents and a retrospective mapping of patient hospital activity. Qualitative data will be managed and analysed using NVivo and quantitative data will be analysed using parametric and non-parametric descriptive statistics. ETHICS AND DISSEMINATION: The study will run from December 2015 to November 2018. We have Health Authority Approval (IRAS project ID: 193932) for phase 1 involving staff only and ethical and Health Authority Approval for phases 2–4 (IRAS project ID: 178525). We will disseminate widely to relevant stakeholders, using a range of accessible formats, including social media. We will publish in international peer-reviewed journals and present to professional, academic and lay audiences through national and international conferences

Dampened motivation as a side effect of contemporary educational policy: a self-determination theory perspective

It has been suggested that features of contemporary educational policy create and encourage teaching and learning practices that dampen human motivation. This paper sought to analyse and extend this discussion through the lens of self-determination theory (SDT). Key questions are discussed such as (1) what is human motivation from a self-determination theory perspective, and (2) how and why is it dampened by features of contemporary educational policy? The discussion is then extended to explore the extent to which dampened human motivation from an SDT perspective might be considered unjust if they systematically dampen motivation

Dampened motivation as a side effect of contemporary educational policy: a self-determination theory perspective

It has been suggested that features of contemporary educational policy create and encourage teaching and learning practices that dampen human motivation. This paper sought to analyse and extend this discussion through the lens of self-determination theory (SDT). Key questions are discussed such as (1) what is human motivation from a self-determination theory perspective, and (2) how and why is it dampened by features of contemporary educational policy? The discussion is then extended to explore the extent to which dampened human motivation from an SDT perspective might be considered unjust if they systematically dampen motivation

A gradual separation from the world:commentary on a qualitative exploration of existential loneliness in old age

Aims and methods: Loneliness is a prevalent and significant issue. It has been identified as a particularly important physical and mental health risk for older people. This article critically explores and discusses a recent study that sought to qualitatively explore the lived experiences of existential loneliness in a large sample of older people living in retirement community contexts. Findings: The data pointed to complex, multilayered challenges, often brought about by ageing, that give rise to unique experiences of existential loneliness for many older people. Conclusions: For clinical practitioners, understanding how older people experience existential loneliness is essential if we are to develop support mechanisms that compassionately and empathically respond to them.</p

Superconductivity and Charge Density Wave in a Quasi-One-Dimensional Spin Gap System

We consider a model of spin-gapped chains weakly coupled by Josephson and Coulomb interactions. Combining such non-perturbative methods as bosonization and Bethe ansatz to treat the intra-chain interactions with the Random Phase Approximation for the inter-chain couplings and the first corrections to this, we investigate the phase diagram of this model. The phase diagram shows both charge density wave ordering and superconductivity. These phases are seperated by a line of critical points which exhibits an approximate an SU(2) symmetry. We consider the effects of a magnetic field on the system. We apply the theory to the material Sr_2 Ca_12 Cu_24 O_41 and suggest further experiments.Comment: 14 pages, 7 figure; submitted to PRB; Revised with new version: references added; section on the flux state remove

Education Policy and mental weakness:a response to a mental health crisis

Educationalists have been concerned with the labelling and treatment of children with mental health difficulties in the education system in England for some time (Timimi 2002; Rose 2005; Jull 2008, Cole 2015). These concerns have centred on the role of policy in ‘othering’ such students as deviant learners. The unprecedented number of children suffering from mental illnesses, has forced policymakers to address children’s mental health difficulties. This has involved the identification of a sub-set of the school population experiencing ‘less-severe’ mental health issues, to be addressed through a suite of policy interventions delivered by whole-school approaches, but targeted towards children situated as mentally ‘weak’. Drawing upon a Foucauldian theory of governmentality that addresses children’s behavioural motivations (Rose 1989; Millar and Rose 1990; Foucault 2001; 2008; Popkewitz 2012) an in-depth analysis of a number of educational policy initiatives related to mental health, is conducted, that it is argued are fundamentally flawed. This analysis is followed by a discussion of the performative culture of High Stakes Testing in contributing to children’s mental health difficulties. Here it is argued that a narrative of mental weakness serves to justify a neoliberal rationality towards the treatment of children for whom the performative logic assumed to motivate all learners, fails