Uncoupled excitons in semiconductor microcavities detected in resonant Raman scattering

We present an outgoing resonant Raman-scattering study of a GaAs/AlGaAs based microcavity embedded in a p-i-n junction. The p-i-n junction allows the vertical electric field to be varied, permitting control of exciton-photon detuning and quenching of photoluminescence which otherwise obscures the inelastic light scattering signals. Peaks corresponding to the upper and lower polariton branches are observed in the resonant Raman cross sections, along with a third peak at the energy of uncoupled excitons. This third peak, attributed to disorder activated Raman scattering, provides clear evidence for the existence of uncoupled exciton reservoir states in microcavities in the strong-coupling regime

Three Key Questions on Fractal Conductance Fluctuations: Dynamics, Quantization and Coherence

Recent investigations of fractal conductance fluctuations (FCF) in electron billiards reveal crucial discrepancies between experimental behavior and the semiclassical Landauer-Buttiker (SLB) theory that predicted their existence. In particular, the roles played by the billiard's geometry, potential profile and the resulting electron trajectory distribution are not well understood. We present measurements on two custom-made devices - a 'disrupted' billiard device and a 'bilayer' billiard device - designed to probe directly these three characteristics. Our results demonstrate that intricate processes beyond those proposed in the SLB theory are required to explain FCF.Comment: 17 pages, 4 figures, in press for Physical Review

Cervical length and quantitative fetal fibronectin in the prediction of spontaneous preterm birth in asymptomatic women with congenital uterine anomaly

BACKGROUND: Congenital uterine anomalies (CUA) are associated with late miscarriage and spontaneous preterm birth (sPTB). OBJECTIVES: Our aim was to 1) determine the rate of sPTB in each type of CUA and 2) assess the performance of quantitative fetal fibronectin (qfFN) and transvaginal cervical length (CL) measurement by ultrasound in asymptomatic women with CUA for the prediction of sPTB at <34 and <37 weeks of gestation. STUDY DESIGN: This was a retrospective cohort of women with CUA asymptomatic for sPTB, from four UK tertiary referral centres (2001-2016). CUAs were categorised into fusion (unicornuate, didelphic and bicornuate uteri) or resorption defects (septate, with or without resection and arcuate uteri), based on pre-pregnancy diagnosis. All women underwent serial transvaginal ultrasound CL assessment in the second trimester (16 to 24 weeks' gestation); a subgroup underwent qfFN testing from 18 weeks' gestation. We investigated the relationship between CUA and predictive test performance for sPTB before 34 and 37 weeks' gestation. RESULTS: Three hundred and nineteen women were identified as having CUA within our high-risk population. 7% (23/319) delivered spontaneously <34 weeks, and 18% (56/319) <37 weeks' gestation. Rates of sPTB by type were: 26% (7/27) for unicornuate, 21% (7/34) for didelphic, 16% (31/189) for bicornuate, 13% (7/56) for septate and 31% (4/13) for arcuate. 80% (45/56) of women who had sPTB <37 weeks did not develop a short CL (<25 mm) during the surveillance period (16-24 weeks). The diagnostic accuracy of short CL had low sensitivity (20.3) for predicting sPTB <34 weeks. Cervical Length had ROC AUC of 0.56 (95% CI 0.48 to 0.64) and 0.59 (95% CI 0.55 to 0.64) for prediction of sPTB <34 and 37 weeks' respectively. The AUC for CL to predict sPTB <34 weeks was 0.48 for fusion defects (95% CI 0.39 to 0.57) but 0.78 (95% CI 0.66 to 0.91) for women with resorption defects. Overall quantitative fetal fibronectin had a AUC of 0.63 (95% CI 0.49 to 0.77) and 0.58 (95% CI 0.49 to 0.68) for prediction of sPTB <34 and 37 weeks, respectively. AUC for prediction of sPTB <37 weeks with qfFN for fusion defects was 0.52 (95% CI 0.41 to 0.63), but 0.79 (0.63 to 0.95) for women with resorption defects. Results were similar when women with intervention were excluded. CONCLUSION: Commonly used markers CL and qfFN have utility in prediction of sPTB in resorption congenital uterine defects but not in fusion defects. This is contrary to other high-risk populations. These findings need to be accounted for when planning antenatal care and have potential implications for predictive tests used in sPTB surveillance and intervention

Interaction Effects in a One-Dimensional Constriction

We have investigated the transport properties of one-dimensional (1D) constrictions defined by split-gates in high quality GaAs/AlGaAs heterostructures. In addition to the usual quantized conductance plateaus, the equilibrium conductance shows a structure close to $0.7(2e^2/h)$, and in consolidating our previous work [K.~J. Thomas et al., Phys. Rev. Lett. 77, 135 (1996)] this 0.7 structure has been investigated in a wide range of samples as a function of temperature, carrier density, in-plane magnetic field $B_{\parallel}$ and source-drain voltage $V_{sd}$. We show that the 0.7 structure is not due to transmission or resonance effects, nor does it arise from the asymmetry of the heterojunction in the growth direction. All the 1D subbands show Zeeman splitting at high $B_{\parallel}$, and in the wide channel limit the $g$-factor is $\mid g \mid \approx 0.4$, close to that of bulk GaAs. As the channel is progressively narrowed we measure an exchange-enhanced $g$-factor. The measurements establish that the 0.7 structure is related to spin, and that electron-electron interactions become important for the last few conducting 1D subbands.Comment: 8 pages, 7 figures (accepted in Phys. Rev. B

Moving Beyond Christianity: Islam, Judaism, Hinduism and Mental Health

To date the literature on religion and mental health has focused upon Christianity. We cannot assume that these findings can be transposed onto other faith groups. In this paper I focus upon Islam, Judaism and Hinduism and discuss understandings of mental illness and the relationships between central beliefs and mental health. I discuss implications for clinical work and psychotherapy

Revisiting the relevance of economic theory to hotel revenue management education and practice in the era of Big Data

Abstract This paper explores the role of economics in hospitality education and industry practice, with a particular focus on revenue management, and puts forward an argument for a return to the inclusion of economic theory in UK hospitality education, not seen since the 1990s. Given the increasing amounts of pricing data available to both managers and customers and the consequent market complexities now seen, developing economic literacy is demonstrated to be a crucial skill required for future hospitality graduates, allowing them to make successful revenue decisions and sense-check with confidence the decisions made by automated revenue systems. Economic literacy is defined as a balanced understanding of economic theory that can be applied in real-life business scenarios, extending beyond simple consideration of supply and demand to a mixture of neoclassical and behavioural approaches to economics

Contemporary Asian Artistic Expressions and Tourism – An Introduction

This introductory chapter presents and critically discusses the various themes underpinning this book. Firstly, it provides an examination of the notion of ‘contemporary art’, including an overview of the existing definitions and debates in the current literature. Secondly, this chapter discusses the nexus between tourism and contemporary art by providing an overview of the past studies conducted on cultural and heritage tourism. In this section, the various themes underpinning the different parts of the literature on art tourism (e.g. identity, authenticity, commoditisation and capitalism) are considered. Thirdly, a discussion on the relationship between tourism and Asian contemporary art is presented, which also includes a part problematising and questioning terms like ‘Asia’ and ‘Asian art’. Finally, an overview of the different chapters that constitute the backbone of this collection is offered alongside the four themes around which the book is structured

Tourism culture(s): The Hospitality Dimension

The focus of the paper is on tourism culture as it operates where commercial hospitality is on offer, especially at hotels and resorts in developing countries. It is suggested that three quite distinct perspectives can assist in helping us understand this aspect of tourism culture, which emerges where worker and tourist roles inevitably converge and interact. In themselves, such perspectives are not new, but they rarely seem to have been applied in the context of hotels and resorts. The first perspective, derived from the work of Homi Bhabha, conceives of tourism culture as hybrid in nature, operating in a ‘third space’ between tourist and ‘host,’ and directs attention to the uncertain and negotiated aspects of tourism culture. In the second, that of the socio-technical system, tourism culture is seen as an interface between, on the one hand, the formal operational rules and procedures designed to deliver an organisation’s mission and, on the other hand, the on-going and lived-in cultures brought into the ‘system’ by tourists and the hospitality providers. The third perspective, that of the total institution, derived from Goffman, focuses to the social and physical boundaries that separate the hotel or resort from the outside world and on the cultural practices that serve to further differentiate it and its population from the outside. It is suggested that use of these perspectives can further our understanding of the nature of tourism at different destinations and the ways hotels and similar institutions impact on both staff members and holidaymakers. As a consequence, they are theoretically, empirically relevant and politically important