Comment on "Including Systematic Uncertainties in Confidence Interval Construction for Poisson Statistics"

The incorporation of systematic uncertainties into confidence interval calculations has been addressed recently in a paper by Conrad et al. (Physical Review D 67 (2003) 012002). In their work, systematic uncertainities in detector efficiencies and background flux predictions were incorporated following the hybrid frequentist-Bayesian prescription of Cousins and Highland, but using the likelihood ratio ordering of Feldman and Cousins in order to produce "unified" confidence intervals. In general, the resulting intervals behaved as one would intuitively expect, i.e. increased with increasing uncertainties. However, it was noted that for numbers of observed events less than or of order of the expected background, the intervals could sometimes behave in a completely counter-intuitive fashion -- being seen to initially decrease in the face of increasing uncertainties, but only for the case of increasing signal efficiency uncertainty. In this comment, we show that the problematic behaviour is due to integration over the signal efficiency uncertainty while maximising the best fit alternative hypothesis likelihood. If the alternative hypothesis likelihood is determined by unconditionally maximising with respect to both the unknown signal and signal efficiency uncertainty, the limits display the correct intuitive behaviour.Comment: Submitted to Physical Review

Unbiased cut selection for optimal upper limits in neutrino detectors: the model rejection potential technique

We present a method for optimising experimental cuts in order to place the strongest constraints (upper limits) on theoretical signal models. The method relies only on signal and background expectations derived from Monte-Carlo simulations, so no bias is introduced by looking at actual data, for instance by setting a limit based on expected signal above the ``last remaining data event.'' After discussing the concept of the ``average upper limit,'' based on the expectation from an ensemble of repeated experiments with no true signal, we show how the best model rejection potential is achieved by optimising the cuts to minimise the ratio of this ``average upper limit'' to the expected signal from the model. As an example, we use this technique to determine the limit sensitivity of kilometre scale neutrino detectors to extra-terrestrial neutrino fluxes from a variety of models, e.g. active galaxies and gamma-ray bursts. We suggest that these model rejection potential optimised limits be used as a standard method of comparing the sensitivity of proposed neutrino detectors.Comment: 18 pages, 7 figures, submitted to Astroparticle Physic

Desymmetrisation reactions of cyclohexa-1,4-dienes and marine natural product synthesis

This thesis describes novel diastereoselective group selective processes for the desymmetrisation of cyclohexa-1,4-dienes, and their application to target synthesis of the cladiellin diterpenes. In addition, an enantioselective approach to batzelladine C methyl ester is described, permitting stereochemical assignment of batzelladine C. Chapter 1 describes the use of diastereoselective iodocyclisation reactions for the desymmetrisation of cyclohexa-1,4-dienes, and also details a novel epoxidation-cyclisation transformation, enabling the formation of up to six contiguous stereogenic centres, selectively, in a single step. Chapter 2 introduces the cladiellin diterpenes and describes the application of novel diastereoselective Prins chemistry for the synthesis of a model of the cladiellin core. Chapter 3 describes our attempts at elaborating the cladiellin model to approach the cladiellin framework and discusses an unexpected but interesting Prins cyclisation/rearrangement process. Chapter 4 describes an enantioselective synthesis of batzelladine C methyl ester, permitting assignment of the relative and absolute stereochemistry of batzelladine C.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

“The stress can be unbearable, but the good times are like finding gold”: A phase one modelling survey to inform the development of a self-help positive reappraisal coping intervention for caregivers of those with autism spectrum disorder

Caregivers of individuals with ASD can experience various practical, psychological, and social demands and need effective ways of coping to ameliorate the negative effects of caregiving. Numerous coping strategies are available, but the literature shows that caregivers can still struggle to cope, suggesting that interventions to support coping efforts could be beneficial. The MRC framework advocates the systematic development and evaluation of interventions, and this study was conducted to inform the future development of a self-help Positive Reappraisal Coping Intervention (PRCI) for these caregivers. The aim was to establish whether positive reappraisal coping strategies were used and associated with greater psychological wellbeing, prior to developing such an intervention. Method. Caregivers of individuals with ASD (N = 112) responded to items from an existing PRCI (Lancastle, 2006; Lancastle & Boivin, 2008), by writing about aspects of caregiving that reflected the meaning of each item. They also completed questionnaires assessing resilience, caregiving burden, and positive and negative emotions. Results. Participants provided significantly more positive responses than negative responses to PRCI items, demonstrating their use of positive reappraisal coping. Thematic analyses showed that positive responses focused on factors such as their loved one’s personality and achievements, the contributions caregivers had made to this person’s progress, the support received, and their own personal development. Positive reappraisal coping was associated with greater resilience, more positive and less negative emotions, and a lesser sense of caregiver burden. Conclusion. This modelling study suggests that positive reappraisal strategies were used by caregivers and associated with greater psychological wellbeing. The findings will inform the development of a self-help PRCI for the caregivers of those with ASD. Future studies will systematically evaluate that PRCI to determine the nature of intervention effects and mediators and moderators of effects

Desymmetrisation reactions of cyclohexa-1,4-dienes and marine natural product synthesis

This thesis describes novel diastereoselective group selective processes for the desymmetrisation of cyclohexa-1,4-dienes, and their application to target synthesis of the cladiellin diterpenes. In addition, an enantioselective approach to batzelladine C methyl ester is described, permitting stereochemical assignment of batzelladine C. Chapter 1 describes the use of diastereoselective iodocyclisation reactions for the desymmetrisation of cyclohexa-1,4-dienes, and also details a novel epoxidation-cyclisation transformation, enabling the formation of up to six contiguous stereogenic centres, selectively, in a single step. Chapter 2 introduces the cladiellin diterpenes and describes the application of novel diastereoselective Prins chemistry for the synthesis of a model of the cladiellin core. Chapter 3 describes our attempts at elaborating the cladiellin model to approach the cladiellin framework and discusses an unexpected but interesting Prins cyclisation/rearrangement process. Chapter 4 describes an enantioselective synthesis of batzelladine C methyl ester, permitting assignment of the relative and absolute stereochemistry of batzelladine C

An unexpected Prins desymmetrisation reaction driven by silyl migration

Prins desymmetrisation reactions of cyclohexa-1,4-diene derivatives have been investigated as a route to the core of the cladiellin diterpenes. During the course of this work, we observed the formation of a partially-reduced benzofuran 18, which is clearly derived from oxocarbenium ion 21. This can only be rationalised by an unexpected primary to secondary silyl group migration

FUSE Measurements of Far Ultraviolet Extinction. I. Galactic Sight Lines

We present extinction curves that include data down to far ultraviolet wavelengths (FUV; 1050 - 1200 A) for nine Galactic sight lines. The FUV extinction was measured using data from the Far Ultraviolet Spectroscopic Explorer. The sight lines were chosen for their unusual extinction properties in the infrared through the ultraviolet; that they probe a wide range of dust environments is evidenced by the large spread in their measured ratios of total-to-selective extinction, R_V = 2.43 - 3.81. We find that extrapolation of the Fitzpatrick & Massa relationship from the ultraviolet appears to be a good predictor of the FUV extinction behavior. We find that predictions of the FUV extinction based upon the Cardelli, Clayton & Mathis (CCM) dependence on R_V give mixed results. For the seven extinction curves well represented by CCM in the infrared through ultraviolet, the FUV extinction is well predicted in three sight lines, over-predicted in two sight lines, and under-predicted in 2 sight lines. A Maximum Entropy Method analysis using a simple three component grain model shows that seven of the nine sight lines in the study require a larger fraction of grain materials to be in dust when FUV extinction is included in the models. Most of the added grain material is in the form of small (radii < 200 A) grains.Comment: Accepted for publication in the Astrophysical Journal. 31 pages with 7 figure

Rotational velocities of A-type stars I. Measurement of vsini in the southern hemisphere

Within the scope of a Key Programme determining fundamental parameters of stars observed by HIPPARCOS, spectra of 525 B8 to F2-type stars brighter than V=8 have been collected at ESO. Fourier transforms of several line profiles in the range 4200-4500 A are used to derive vsini from the frequency of the first zero. Statistical analysis of the sample indicates that measurement error is a function of vsini and this relative error of the rotational velocity is found to be about 6% on average. The results obtained are compared with data from the literature. There is a systematic shift from standard values from Slettebak et al. (1975), which are 10 to 12% lower than our findings. Comparisons with other independent vsini values tend to prove that those from Slettebak et al. are underestimated. This effect is attributed to the presence of binaries in the standard sample of Slettebak et al., and to the model atmosphere they used.Comment: 17 pages, includes 18 figures, accepted in A&