Intrinsic Variability and Field Statistics for the Vela Pulsar: 2. Systematics and Single-Component Fits

Individual pulses from pulsars have intensity-phase profiles that differ widely from pulse to pulse, from the average profile, and from phase to phase within a pulse. Widely accepted explanations do not exist for this variability or for the mechanism producing the radiation. The variability corresponds to the field statistics, particularly the distribution of wave field amplitudes, which are predicted by theories for wave growth in inhomogeneous media. This paper shows that the field statistics of the Vela pulsar (PSR B0833-45) are well-defined and vary as a function of pulse phase, evolving from Gaussian intensity statistics off-pulse to approximately power-law and then lognormal distributions near the pulse peak to approximately power-law and eventually Gaussian statistics off-pulse again. Detailed single-component fits confirm that the variability corresponds to lognormal statistics near the peak of the pulse profile and Gaussian intensity statistics off-pulse. The lognormal field statistics observed are consistent with the prediction of stochastic growth theory (SGT) for a purely linear system close to marginal stability. The simplest interpretations are that the pulsar's variability is a direct manifestation of an SGT state and the emission mechanism is linear (either direct or indirect), with no evidence for nonlinear mechanisms like modulational instability and wave collapse which produce power-law field statistics. Stringent constraints are placed on nonlinear mechanisms: they must produce lognormal statistics when suitably ensemble-averaged. Field statistics are thus a powerful, potentially widely applicable tool for understanding variability and constraining mechanisms and source characteristics of coherent astrophysical and space emissions.Comment: 11 pages, 12 figures. Accepted by Monthly Notices of the Royal Astronmical Society in April 200

Intrinsic Variability and Field Statistics for the Vela Pulsar: 3. Two-Component Fits and Detailed Assessment of Stochastic Growth Theory

The variability of the Vela pulsar (PSR B0833-45) corresponds to well-defined field statistics that vary with pulsar phase, ranging from Gaussian intensity statistics off-pulse to approximately power-law statistics in a transition region and then lognormal statistics on-pulse, excluding giant micropulses. These data are analyzed here in terms of two superposed wave populations, using a new calculation for the amplitude statistics of two vectorially-combined transverse fields. Detailed analyses show that the approximately power-law and lognormal distributions observed are fitted well at essentially all on-pulse phases by Gaussian-lognormal and double-lognormal combinations, respectively. These good fits, plus the smooth but significant variations in fit parameters across the source, provide strong evidence that the approximately power-law statistics observed in the transition region are not intrinsic. Instead, the data are consistent with normal pulsar emission having lognormal statistics at all phases. This is consistent with generation in an inhomogeneous source obeying stochastic growth theory (SGT) and with the emission mechanism being purely linear (either direct or indirect). A nonlinear mechanism is viable only if it produces lognormal statistics when suitably ensemble-averaged. Variations in the SGT fit parameters with phase imply that the radiation is relatively more variable near the pulse edges than near the center, as found in earlier work. In contrast, Vela's giant micropulses come from a very restricted phase range and have power-law statistics with indices ($6.7 \pm 0.6$) not inconsistent with nonlinear wave collapse. These results imply that normal pulses have a different source and generation mechanism than giant micropulses, as suggested previously on other grounds.Comment: 10 pages and 14 figures. Accepted by Monthly Notices of the Royal Astronomical Society in April 200

Educating children with life limiting and life threatening conditions

There are about 49,000 children and young people in the UK with a life limiting or life threatening condition; very many are in mainstream schools and the numbers are rising. Conditions include cancer, cerebral palsy, brain injury and Duchenne muscular dystrophy. This workshop shared the findings from research which sought to understand teachers' views and experiences of working with children with these conditions, and to identify the support that they need. The multi-disciplinary research team used the findings to write a practical handbook for teachers and school-based staff. It aims to address teachers' concerns about; medical care, responding to government policies, children's emotional and behavioural needs, bereavement, how to communicate with children, families and professionals, teaching and learning strategies, and a school culture that includes support for teachers. We will share the book and try to answer your questions

Tunneling between single and multi-centered black hole configurations

We find a gravitational instanton that connects an initial state corresponding to a single-centered extremal Reissner-Nordstrom (ERN) black hole configuration, to a final state corresponding to a multi-centered configuration. This instanton is interpreted as describing quantum tunneling between the two different black hole solutions. We evaluate the Euclidean action for this instanton and find that the amplitude for the tunneling process is equal to half the difference in entropy between the initial and final configurations.Comment: 8 pages, 4 figures. v4: final version accepted for publication in Phys. Rev.

Some exact solutions with torsion in 5-D Einstein-Gauss-Bonnet gravity

Exact solutions with torsion in Einstein-Gauss-Bonnet gravity are derived. These solutions have a cross product structure of two constant curvature manifolds. The equations of motion give a relation for the coupling constants of the theory in order to have solutions with nontrivial torsion. This relation is not the Chern-Simons combination. One of the solutions has a $AdS_2\times S^3$ structure and is so the purely gravitational analogue of the Bertotti-Robinson space-time where the torsion can be seen as the dual of the covariantly constant electromagnetic field.Comment: 19 pages, LaTex, no figures. References added, notation clarified. Accepted for publication on Physical Review

Graviton-Graviton Scattering, Bel-Robinson and Energy (Pseudo)-Tensors

Motivated by recent work involving the graviton-graviton tree scattering amplitude, and its twin descriptions as the square of the Bel-Robinson tensor, B_{\m\n\a\b}, and as the "current-current interaction" square of gravitational energy pseudo-tensors t_{\a\b},we find an exact tensor-square root equality B_{\mn\a\b} = \pa^2_\mn t_{\a\b}, for a combination of Einstein and Landau-Lifschitz t_\ab, in Riemann normal coordinates. In the process, we relate, on-shell, the usual superpotential basis for classifying pseudo-tensors with one spanned by polynomials in the curvature.Comment: 7 page

The Bell-Szekeres Solution and Related Solutions of the Einstein-Maxwell Equations

A novel technique for solving some head-on collisions of plane homogeneous light-like signals in Einstein-Maxwell theory is described. The technique is a by-product of a re-examination of the fundamental Bell-Szekeres solution in this field of study. Extensions of the Bell-Szekeres collision problem to include light-like shells and gravitational waves are described and a family of solutions having geometrical and topological properties in common with the Bell-Szekeres solution is derived.Comment: 18 pages, Latex fil

Community-based trial of screening for Chlamydia trachomatis to prevent pelvic inflammatory disease: the POPI (prevention of pelvic infection) trial.

BACKGROUND: Pelvic inflammatory disease (PID) is common and can lead to tubal factor infertility, ectopic pregnancy or chronic pelvic pain. Despite major UK government investment in the National Chlamydia Screening Programme, evidence of benefit remains controversial. The main aim of this trial was to investigate whether screening and treatment of chlamydial infection reduced the incidence of PID over 12 months. Secondary aims were to conduct exploratory studies of the role of bacterial vaginosis (BV) in the development of PID and of the natural history of chlamydial infection. DESIGN: Randomised controlled trial with follow up after 12 months. SETTING NON-HEALTHCARE: Common rooms and lecture theatres at 20 universities and further education colleges in Greater London. PARTICIPANTS: 2500 sexually active female students were asked to complete a questionnaire on sexual health and provide self-administered vaginal swabs and smears. INTERVENTION: Vaginal swabs from intervention women were tested for chlamydia by polymerase chain reaction (PCR) and those infected referred for treatment. Vaginal swabs from control women were stored and analysed after a year. Vaginal smears were Gram stained and analysed for BV. MAIN OUTCOME MEASURE: Incidence of clinical PID over 12 months in intervention and control groups. Possible cases of PID will be identified from questionnaires and record searches. Confirmation of the diagnosis will be done by detailed review of medical records by three independent researchers blind to whether the woman is in intervention or control group. TRIAL REGISTRATION: Clinical Trials NCT 00115388

Elevated PSA is associated with decreased physical function in men with prostate cancer

Studies have reported an association between cortisol and fatigue in multiple clinical populations, including prostate cancer (PCa). Treatment options for men with PCa, such as androgen deprivation therapy (ADT), come with a wide variety of adverse effects, including cancer-related fatigue, which greatly impacts quality of life (QoL). PURPOSE: Conduct a preliminary analysis on the association between cortisol, fatigue and QoL in men with PCa. METHODS: This study is part of an ongoing study to determine the impact of PCa and PCa treatment on fatigue and QoL approved by the University of Texas Health Science Center at San Antonio Intuitional Review Board. Twenty-one men (age: 69.1±11.55; BMI 28.99±4.78) with PCa were recruited from the Urology Clinic at the Medical Arts and Research Center in San Antonio, Texas. Participants provided ~2 mL of saliva for cortisol quantification using the passive drool technique. Saliva was immediately placed on ice and transferred within 4 hours to a freezer at -80oC until analysis. Cortisol was quantified using a commercially available salivary cortisol ELISA assay kit (Salimetrics, College Park, PA). Participants also completed three questionnaires: the Brief Fatigue Inventory, the Functional Assessment of Chronic Illness Therapy-Fatigue, and the SF-36. Pearson product moment correlation was performed to determine association between outcome variables. Student t-test was used to determine differences in cortisol, fatigue and QoL between men treated with ADT and men not treated with ADT. Significance was set at pRESULTS: Of the 21 participants, 9.5% (n=2) of participants had metastatic PCa, 4.8% (n=1) had castration-resistant PCa, 4.8% (n=1) had high-grade prostatic intraepithelial neoplasia, and 81% (n=17) had localized PCa. Twelve of the participants were being treated with ADT (57.14%). Significant correlation was observed between prostate specific antigen (PSA) and physical function (r=-0.728; p=.001), physical health (r=-0.729; p=.001), and emotional problems (r=-0.765; p=.001). No correlation was found between fatigue and cortisol levels. A comparison between groups revealed no significant difference in fatigue level between those on ADT versus those not on ADT. However, men not on ADT had a 28% higher average general health score. CONCLUSION: The results of this study suggest cortisol is not a strong physiological measure of fatigue in men with PCa. Furthermore, these preliminary data suggest that advanced cancer, as evident by elevated PSA, significantly impacts physical function and QoL in men with PCa. Further study for a more reliable biomarker of fatigue and interventions to improve QoL in men with PCa is warranted