The effect of primordial fluctuations on neutrino oscillations

Recent work has shown that neutrino oscillations in matter can be greatly enhanced by flips between mass eigenstates if the medium is fluctuating with a period equal to the neutrino oscillation length. Here we investigate the effect of the primordial fluctuations on the neutrino oscillations in the early universe. We calculate the oscillation probability in the case of a general power law fluctuation spectrum and for a more realistic spectrum predicted by inflation. We also include the effect of the amplification of fluctuations resulting from the QCD phase transition. We find that there is a region of parameter space where this mechanism would be the dominant mechanism for producing sterile neutrinos. However this conclusion does not take account of the damping of fluctuations on the neutrino oscillation scale when the neutrinos decouple from the plasma. We find that this reduces the probability of flips between the mass eigenstates to an unobservable level.Comment: 11 pages, 3 Figure

Radial and rotational velocities of young brown dwarfs and very low-mass stars in the Upper Scorpius OB association and the rho Ophiuchi cloud core

We present the results of a radial velocity (RV) survey of 14 brown dwarfs (BDs) and very low-mass (VLM) stars in the Upper Scorpius OB association (UScoOB) and 3 BD candidates in the rho Ophiuchi dark cloud core. We obtained high-resolution echelle spectra at the Very Large Telescope using Ultraviolet and Visual Echelle Spectrograph (UVES) at two different epochs for each object, and measured the shifts in their RVs to identify candidates for binary/multiple systems in the sample. The average time separation of the RV measurements is 21.6d, and our survey is sensitive to the binaries with separation < 0.1 au. We found that 4 out of 17 objects (or 24^{+16}_{-13} per cent by fraction) show a significant RV change in 4-33d time scale, and are considered as binary/multiple `candidates.' We found no double-lined spectroscopic binaries in our sample, based on the shape of cross-correlation curves. The RV dispersion of the objects in UScoOB is found to be very similar to that of the BD and VLM stars in Chamaeleon I (Cha I). We also found the distribution of the mean rotational velocities (v sin i) of the UScoOB objects is similar to that of the Cha I, but the dispersion of v sin i is much larger than that of the Cha I objects.Comment: 10 pages, 5 figures, accepted for publication in MNRA

‘Without occupation you don't exist’: Occupational engagement and mental illness

This article has been made available through the Brunel Open Access Publishing Fund.This phenomenological study explores the meanings of work for people living with severe and enduring mental health conditions. The participants were three women and seven men who were attending a mental health day centre. Data were collected through up to three depth interviews with each participant over 18 months. The interviews were digitally recorded, transcribed verbatim, and analysed according to phenomenological principles. Two overarching themes were identified. Building and maintaining an occupational identity expressed the ways in which participants used occupations as the building blocks of an evolving identity. Most of the participants wanted to work, and participation in occupations was seen as essential to recovery from mental ill-health. Work and other ways of belonging encapsulated the need to feel connected to others. Many of the participants envisaged working as a way of achieving this. The longitudinal nature of the study facilitated engagement with the developing narratives and exploration of the changes and consistencies in the participants' meaning making about their occupations. Implications for understanding individuals' occupational participation which enhances a sense of self and promotes feelings of belonging are identified

To adopt is to adapt: The process of implementing the ICF with an acute stroke multidisciplinary team in England

Copyright @ 2012 Informa Plc. The article can be accessed from the link below.This article has been made available through the Brunel Open Access Publishing Fund.Purpose: The success of the International Classification of Functioning, Disability and Health (ICF) depends on its uptake in clinical practice. This project aimed to explore ways the ICF could be used with an acute stroke multidisciplinary team and identify key learning from the implementation process. Method: Using an action research approach, iterative cycles of observe, plan, act and evaluate were used within three phases: exploratory; innovatory and reflective. Thematic analysis was undertaken, using a model of immersion and crystallisation, on data collected via interview and focus groups, e-mail communications, minutes from relevant meetings, field notes and a reflective diary. Results: Two overall themes were determined from the data analysis which enabled implementation. There is a need to: (1) adopt the ICF in ways that meet local service needs; and (2) adapt the ICF language and format. Conclusions: The empirical findings demonstrate how to make the ICF classification a clinical reality. First, we need to adopt the ICF as a vehicle to implement local service priorities e.g. to structure a multidisciplinary team report, thus enabling ownership of the implementation process. Second, we need to adapt the ICF terminology and format to make it acceptable for use by clinicians.This study is funded by The Elizabeth Casson Trust. This article is made available through the Brunel Open Access Publishing Fund

The meaning and experience of work in the context of severe and enduring mental health problems: An interpretative phenomenological analysis

This is the author's final version of the article. The final publication is available from the link below. Copyright @ 2013 IOS Press and the Authors.Research into mental health and employment has indicated that work holds multiple meanings for people with mental health problems. This paper reports findings from a phenomenological study which aimed to understand the complexity of these meanings by exploration of the perspectives of one individual who was considering returning to work. Data were gathered through a series of three interviews carried out over a period of 18 months. Three themes were identified – Beliefs and Values about Work, Working with a Mental Health Problem, and Planning for the Future. Analysis and interpretation facilitated understandings of what work represented for the participant. What this study has contributed to the evidence base is a deeper understanding of the multiple meanings of work, and the varied roles that work may play in contributing to meaning and quality of life for people with mental health problems

Z' mass limits and the naturalness of supersymmetry

The discovery of a 125 GeV Higgs boson and rising lower bounds on the masses of superpartners have lead to concerns that supersymmetric models are now fine tuned. Large stop masses, required for a 125 GeV Higgs, feed into the electroweak symmetry breaking conditions through renormalisation group equations forcing one to fine tune these parameters to obtain the correct electroweak vacuum expectation value. Nonetheless this fine tuning depends crucially on our assumptions about the supersymmetry breaking scale. At the same time $U(1)$ extensions provide the most compelling solution to the $\mu$-problem, which is also a naturalness issue, and allow the tree level Higgs mass to be raised substantially above $M_Z$. These very well motivated supersymmetric models predict a new $Z'$ boson which could be discovered at the LHC and the naturalness of the model requires that the $Z'$ boson mass should not be too far above the TeV scale. Moreover this fine tuning appears at the tree level, making it less dependent on assumptions about the supersymmetry breaking mechanism. Here we study this fine tuning for several $U(1)$ supersymmetric extensions of the Standard Model and compare it to the situation in the MSSM where the most direct tree level fine tuning can be probed through chargino mass limits. We show that future LHC $Z'$ searches are extremely important for challenging the most natural scenarios in these models.Comment: 58 pages, 5 figures; typos corrected, references added; matches version to be published in Phys. Rev.

Passive Versus Active Tuberculosis Case Finding and Isoniazid Preventive Therapy Among Household Contacts in a Rural District of Malawi.

SETTING: Thyolo district, rural Malawi. OBJECTIVES: To compare passive with active case finding among household contacts of smear-positive pulmonary tuberculosis (TB) patients for 1) TB case detection and 2) the proportion of child contacts aged under 6 years who are placed on isoniazid (INH) preventive therapy. DESIGN: Cross-sectional study. METHODS: Passive and active case finding was conducted among household contacts, and the uptake of INH preventive therapy in children was assessed. RESULTS: There were 189 index TB cases and 985 household contacts. Human immunodeficiency virus (HIV) prevalence among index cases was 69%. Prevalence of TB by passive case finding among 524 household contacts was 0.19% (191/100000), which was significantly lower than with active finding among 461 contacts (1.74%, 1735/100000, P = 0.01). Of 126 children in the passive cohort, 22 (17%) received INH, while in the active cohort 25 (22%) of 113 children received the drug. Transport costs associated with chest X-ray (CXR) screening were the major reason for low INH uptake. CONCLUSIONS: Where the majority of TB patients are HIV-positive, active case finding among household contacts yields nine times more TB cases and is an opportunity for reducing TB morbidity and mortality. The need for a CXR is an obstacle to the uptake of INH prophylaxis

Songs, stories, rhymes and riddles: African folklore and people's history

Paper presented at the Wits History Workshop: The Making of Class, 9-14 February, 198