The Taming of Closed Time-like Curves

We consider a $R^{1,d}/Z_2$ orbifold, where $Z_2$ acts by time and space reversal, also known as the embedding space of the elliptic de Sitter space. The background has two potentially dangerous problems: time-nonorientability and the existence of closed time-like curves. We first show that closed causal curves disappear after a proper definition of the time function. We then consider the one-loop vacuum expectation value of the stress tensor. A naive QFT analysis yields a divergent result. We then analyze the stress tensor in bosonic string theory, and find the same result as if the target space would be just the Minkowski space $R^{1,d}$, suggesting a zero result for the superstring. This leads us to propose a proper reformulation of QFT, and recalculate the stress tensor. We find almost the same result as in Minkowski space, except for a potential divergence at the initial time slice of the orbifold, analogous to a spacelike Big Bang singularity. Finally, we argue that it is possible to define local S-matrices, even if the spacetime is globally time-nonorientable.Comment: 37 pages, LaTeX2e, uses amssymb, amsmath and epsf macros, 8 eps and 3 ps figures; (v2): Two additional comments + one reference added; (v3): corrections in discussion of CTCs + some clarification

Does backreaction enforce the averaged null energy condition in semiclassical gravity?

The expected stress-energy tensor of quantum fields generically violates the local positive energy conditions of general relativity. However, may satisfy some nonlocal conditions such as the averaged null energy condition (ANEC), which would rule out traversable wormholes. Although ANEC holds in Minkowski spacetime, it can be violated in curved spacetimes if one is allowed to choose the spacetime and quantum state arbitrarily, without imposition of the semiclassical Einstein equation G_{ab} = 8 \pi . In this paper we investigate whether ANEC holds for solutions to this equation, by studying a free, massless scalar field with arbitrary curvature coupling in perturbation theory to second order about the flat spacetime/vacuum solution. We "reduce the order" of the perturbation equations to eliminate spurious solutions, and consider the limit in which the lengthscales determined by the incoming state are much larger than the Planck length. We also need to assume that incoming classical gravitational radiation does not dominate the first order metric perturbation. We find that although the ANEC integral can be negative, if we average the ANEC integral transverse to the geodesic with a suitable Planck scale smearing function, then a strictly positive result is obtained in all cases except for the flat spacetime/vacuum solution. This result suggests --- in agreement with conclusions drawn by Ford and Roman from entirely independent arguments --- that if traversable wormholes do exist as solutions to the semiclassical equations, they cannot be macroscopic but must be ``Planck scale''. A large portion of our paper is devoted to the analysis of general issues concerning the nature of the semiclassical Einstein equation and of prescriptions for extracting physically relevant solutions.Comment: 54 pages, 3 figures, uses revtex macros and epsf.tex, to appear in Phys Rev D. A new appendix has been added showing consistency of our results with recent results of Visser [gr-qc/9604008]. Some corrections were made to Appendix A, and several other minor changes to the body of the paper also were mad

Help-seeking pathways in early psychosis

INTRODUCTION: Understanding the help-seeking pathways of patients with a putative risk of developing psychosis helps improving development of specialised care services. This study aimed at obtaining information about: type of health professionals contacted by patients at putative risk for psychosis on their help-seeking pathways; number of contacts; type of symptoms leading to contacts with health professionals; interval between initial contact and referral to a specialised outpatient service. METHOD: The help-seeking pathways were assessed as part of a prospective study in 104 patients with suspected at-risk states for psychosis. RESULTS: The mean number of contacts prior to referral was 2.38. Patients with psychotic symptoms more often contacted mental health professionals, whereas patients with insidious and more unspecific features more frequently contacted general practitioners (GPs). CONCLUSIONS: GPs have been found to under-identify the insidious features of emerging psychosis (Simon et al. (2005) Br J Psychiatry 187:274–281). The fact that they were most often contacted by patients with exactly these features calls for focussed and specialised help for primary care physicians. Thus, delays along the help-seeking pathways may be shortened. This may be of particular relevance for patients with the deficit syndrome of schizophrenia

Affordances, constraints and information flows as ‘leverage points’ in design for sustainable behaviour

Copyright @ 2012 Social Science Electronic PublishingTwo of Donella Meadows' 'leverage points' for intervening in systems (1999) seem particularly pertinent to design for sustainable behaviour, in the sense that designers may have the scope to implement them in (re-)designing everyday products and services. The 'rules of the system' -- interpreted here to refer to affordances and constraints -- and the structure of information flows both offer a range of opportunities for design interventions to in fluence behaviour change, and in this paper, some of the implications and possibilities are discussed with reference to parallel concepts from within design, HCI and relevant areas of psychology

HES5 silencing is an early and recurrent change in prostate tumourigenesis.

Prostate cancer is the most common cancer in men, resulting in over 10 000 deaths/year in the UK. Sequencing and copy number analysis of primary tumours has revealed heterogeneity within tumours and an absence of recurrent founder mutations, consistent with non-genetic disease initiating events. Using methylation profiling in a series of multi-focal prostate tumours, we identify promoter methylation of the transcription factor HES5 as an early event in prostate tumourigenesis. We confirm that this epigenetic alteration occurs in 86-97% of cases in two independent prostate cancer cohorts (n=49 and n=39 tumour-normal pairs). Treatment of prostate cancer cells with the demethylating agent 5-aza-2'-deoxycytidine increased HES5 expression and downregulated its transcriptional target HES6, consistent with functional silencing of the HES5 gene in prostate cancer. Finally, we identify and test a transcriptional module involving the AR, ERG, HES1 and HES6 and propose a model for the impact of HES5 silencing on tumourigenesis as a starting point for future functional studies.The authors are grateful to study volunteers for their participation and staff at the Welcome Trust Clinical Research Facility, Addenbrooke’s Clinical Research Centre, Cambridge. They also thank the NIHR Cambridge Biomedical Research Centre, the DOH HTA (ProtecT grant), and the NCRI/MRC (ProMPT grant) for help with the bio-repository, The University of Cambridge, Hutchison Whampoa Limited and Cancer Research UK for funding. They are grateful to the CRUK Cambridge Institute Genomics and Bioinformatics Core Facilities. Cross-validation of HES5 methylation includes the use of data generated by the TCGA Research Network.This is the final version of the article. It was originally published in the Endocrine-Related Cancer, April 1, 2015 22 131-144 doi: 10.1530/ERC-14-0454

Measurement of Angular Distributions and R= sigma_L/sigma_T in Diffractive Electroproduction of rho^0 Mesons

Production and decay angular distributions were extracted from measurements of exclusive electroproduction of the rho^0(770) meson over a range in the virtual photon negative four-momentum squared 0.5< Q^2 <4 GeV^2 and the photon-nucleon invariant mass range 3.8< W <6.5 GeV. The experiment was performed with the HERMES spectrometer, using a longitudinally polarized positron beam and a ^3He gas target internal to the HERA e^{+-} storage ring. The event sample combines rho^0 mesons produced incoherently off individual nucleons and coherently off the nucleus as a whole. The distributions in one production angle and two angles describing the rho^0 -> pi+ pi- decay yielded measurements of eight elements of the spin-density matrix, including one that had not been measured before. The results are consistent with the dominance of helicity-conserving amplitudes and natural parity exchange. The improved precision achieved at 47 GeV, reveals evidence for an energy dependence in the ratio R of the longitudinal to transverse cross sections at constant Q^2.Comment: 15 pages, 15 embedded figures, LaTeX for SVJour(epj) document class Revision: Fig. 15 corrected, recent data added to Figs. 10,12,14,15; minor changes to tex

Looking for the women in Baron and Taylor's (1969) Educational administration and the social sciences

A search for women in Baron and Taylor's (1969) Educational administration and the social sciences [London: The Athlone Press] using feminist poststructural discourse analysis (FPDA) has revealed a changing discourse about gendered educational administration over the course of 50 years. Whilst few women are featured in the text itself, citations of women's writing surface the historical contributions of women as headmistresses and public servants. Women who have cited the text since its publication have challenged gendered theory and academic writing conventions. FPDA is used to explore the gendered educational administration discourse through the intertextuality of academic writing. Fluctuations between powerfulness and powerlessness are revealed depending on the socio-political context and women's circumstances

Development and Validation of an OMERACT MRI Whole-Body Score for Inflammation in Peripheral Joints and Entheses in Inflammatory Arthritis (MRI-WIPE)

Objective: To develop a whole-body MRI-scoring system for peripheral arthritis and enthesitis. Methods: After consensus on definitions/locations of MRI pathologies, four multi-reader exercises were performed. Eighty-three joints were scored 0-3 separately for synovitis and osteitis, thirty-three entheses 0-3 separately for soft tissue inflammation and osteitis. Results: In the last exercise, reliability was moderate-good for musculoskeletal radiologists and rheumatologists with previously demonstrated good scoring proficiency. Median pairwise single-measure/average-measure ICCs were 0.67/0.80 for status scores and 0.69/0.82 for change scores; kappas ranged 0.35-0.77. Conclusion: WBMRI scoring of peripheral arthritis and enthesitis is reliable which encourages further testing and refinement in clinical trials