Edge effects in 3D dosimetry: characterisation and correction of the non-uniform dose response of PRESAGE®.

Previous work has shown that PRESAGE® can be used successfully to perform 3D dosimetric measurements of complex radiotherapy treatments. However, measurements near the sample edges are known to be difficult to achieve. This is an issue when the doses at air-material interfaces are of interest, for example when investigating the electron return effect (ERE) present in treatments delivered by magnetic resonance (MR)-linac systems. To study this effect, a set of 3.5 cm-diameter cylindrical PRESAGE® samples was uniformly irradiated with multiple dose fractions, using either a conventional linac or an MR-linac. The samples were imaged between fractions using an optical-CT, to read out the corresponding accumulated doses. A calibration between TPS-predicted dose and optical-CT pixel value was determined for individual dosimeters as a function of radial distance from the axis of rotation. This data was used to develop a correction that was applied to four additional samples of PRESAGE® of the same formulation, irradiated with 3D-CRT and IMRT treatment plans, to recover significantly improved 3D measurements of dose. An alternative strategy was also tested, in which the outer surface of the sample was physically removed prior to irradiation. Results show that for the formulation studied here, PRESAGE® samples have a central region that responds uniformly and an edge region of 6-7 mm where there is gradual increase in dosimeter response, rising to an over-response of 24%-36% at the outer boundary. This non-uniform dose response increases in both extent and magnitude over time. Both mitigation strategies investigated were successful. In our four exemplar studies, we show how discrepancies at edges are reduced from 13%-37% of the maximum dose to between 2 and 8%. Quantitative analysis shows that the 3D gamma passing rates rise from 90.4, 69.3, 63.7 and 43.6% to 97.3, 99.9, 96.7 and 98.9% respectively

Tactical Voting in Plurality Elections

How often will elections end in landslides? What is the probability for a head-to-head race? Analyzing ballot results from several large countries rather anomalous and yet unexplained distributions have been observed. We identify tactical voting as the driving ingredient for the anomalies and introduce a model to study its effect on plurality elections, characterized by the relative strength of the feedback from polls and the pairwise interaction between individuals in the society. With this model it becomes possible to explain the polarization of votes between two candidates, understand the small margin of victories frequently observed for different elections, and analyze the polls' impact in American, Canadian, and Brazilian ballots. Moreover, the model reproduces, quantitatively, the distribution of votes obtained in the Brazilian mayor elections with two, three, and four candidates.Comment: 7 pages, 4 figure

Progressive functional exercise versus best practice advice for adults aged 50 years or over after ankle fracture: protocol for a pilot randomised controlled trial in the UK - the Ankle Fracture Treatment: Enhancing Rehabilitation (AFTER) study

Introduction Ankle fractures result in significant morbidity in adults, with prognosis worsening with increasing age. Previous trials have not found evidence supporting supervised physiotherapy sessions, but these studies have not focused on older adults or tailored the exercise interventions to the complex needs of this patient group. The Ankle Fracture Treatment: Enhancing Rehabilitation study is a pilot randomised controlled trial to assess feasibility of a later definitive trial comparing best-practice advice with progressive functional exercise for adults aged 50 years and over after ankle fracture. The main objectives are to assess: (i) patient engagement with the trial, measured by the participation rate of those eligible; (ii) establish whether the interventions are acceptable to participants and therapists, assessed by intervention adherence levels, participant interviews and a therapist focus group; (iii) participant retention in the trial, measured by the proportion of participants providing outcome data at 6 months; (iv) acceptability of measuring outcomes at 3 and 6 month follow-up. Methods and analysis A multicentre pilot randomised controlled trial with an embedded qualitative study. At least 48 patients aged 50 years and over with an ankle fracture requiring surgical management, or non-operative management by immobilisation for at least 4 weeks, will be recruited from a minimum of three National Health Service hospitals in the UK. Participants will be allocated 1:1 via a central web-based randomisation system to: (i) best-practice advice (one session of face-to-face self-management advice delivered by a physiotherapist and up to two optional additional sessions) or (ii) progressive functional exercise (up to six sessions of individual face-to-face physiotherapy). An embedded qualitative study will include one-to-one interviews with up to 20 participants and a therapist focus group. Ethics and dissemination Hampshire B Research Ethics Committee (18/SC/0281) gave approval on 2nd July 2018. Trial registration number ISRCTN1661233

Toward High-Precision Measures of Large-Scale Structure

I review some results of estimation of the power spectrum of density fluctuations from galaxy redshift surveys and discuss advances that may be possible with the Sloan Digital Sky Survey. I then examine the realities of power spectrum estimation in the presence of Galactic extinction, photometric errors, galaxy evolution, clustering evolution, and uncertainty about the background cosmology.Comment: 24 pages, including 11 postscript figures. Uses crckapb.sty (included in submission). To appear in ``Ringberg Workshop on Large-Scale Structure,'' ed D. Hamilton (Kluwer, Amsterdam), p. 39

Stellar Population Diagnostics of Elliptical Galaxy Formation

Major progress has been achieved in recent years in mapping the properties of passively-evolving, early-type galaxies (ETG) from the local universe all the way to redshift ~2. Here, age and metallicity estimates for local cluster and field ETGs are reviewed as based on color-magnitude, color-sigma, and fundamental plane relations, as well as on spectral-line indices diagnostics. The results of applying the same tools at high redshifts are then discussed, and their consistency with the low-redshift results is assessed. Most low- as well as high-redshift (z~1) observations consistently indicate 1) a formation redshift z>~3 for the bulk of stars in cluster ETGs, with their counterparts in low-density environments being on average ~1-2 Gyr younger, i.e., formed at z>~1.5-2, 2) the duration of the major star formation phase anticorrelates with galaxy mass, and the oldest stellar populations are found in the most massive galaxies. With increasing redshift there is evidence for a decrease in the number density of ETGs, especially of the less massive ones, whereas existing data appear to suggest that most of the most-massive ETGs were already fully assembled at z~1. Beyond this redshift, the space density of ETGs starts dropping significantly, and as ETGs disappear, a population of massive, strongly clustered, starburst galaxies progressively becomes more and more prominent, which makes them the likely progenitors to ETGs.Comment: To appear on Annual Review of Astronomy & Astrophysics, Vol. 44 (2006). 46 pages with 16 figures. Replaced version includes updated references, few typos less, and replaces Fig. 11 and Fig. 16 which had been skrewed u

Per a Jordi Castellanos

A diferència dels amics que ara m’acompayen a la taula i de molts dels presents aquest vespre a l’IEC, jo no he compartit feina amb Jordi Castellanos ni, de fet, vaig ser-ne alumne. Però és tot just per això que al capdavall no refuso de ser aquí: hi sóc (i n’agraeixo l’oportunitat) simplement per un deute compartit de reconeixement per la feina d’excelència que Jordi Castellanos ha fet al llarg de les quatre darreres dècades. Hem de poder dir què admirem i què ens mereix agraïment, i no podem sinó agrair i admirar aquesta seva feina ineludible per als qui ens dediquem a la docència i la recerca en literatura catalana, una feina sobre la qual Castellanos ha edificat un mestratge de què no pensàvem que haguéssim de prescindir tan aviat. Si m’és permès d’insistir en la primera persona, jo hi comptava si més no d’ençà que el 1976, en el marc d’una escola d’estiu, assistia a unes sessions seves sobre noucentisme en el curs de les quals ens avisava de l’aparició imminent, a la nounada revista Els Marges, d’un article sobre el moviment tan i tan interessant que havia escrit un jove que aleshores era a Alemanya (explicava Castellanos), i que ara tinc al costat: el professor Murgades. La part més personal de l’agraïment que em fa ser aquí em fa memòria d’episodis, allargats en el temps, de la disponibilitat generosa d

Unidimensional scales for fears of cancer recurrence and their psychometric properties : the FCR4 and FCR7

Funding: Support was received from SUPAC (NCRI) Early Career Fund to complete this study. NCRI Supportive & Palliative Care (SuPaC) Research Collaboratives Capacity Building Grant Scheme: G Ozakinci (PI), G Humphris, M Sharpe.Background:  The assessment of fear of recurrence (FCR) is crucial for understanding an important psychological state in patients diagnosed and treated for cancer. The study aim was to determine psychometric details of a seven question self-report scale (FCR7) and a short form (FCR4) based upon items already used in various extensive measures of FCR. Methods:  Two consecutive samples of patients (breast and colorectal) were recruited from a single specialist cancer centre. The survey instrument contained the FCR7 items, Hospital Anxiety and Depression Scale (HADS), and demographic details. Clinical information was obtained from patient hospital records. Statistical analyses were performed using classical test and item response theory approaches, to demonstrate unidimensional factor structure and testing key parameters. Construct validity was inspected through nomological and theoretical prediction. Results:  Internal consistency was demonstrated by alpha coefficients (FCR4: 0.93 and FCR7: 0.92). Both scales (FCR7 & FCR4) were associated with the HADs subscales as predicted. Patients who experienced chemotherapy, minor aches/pains, thought avoidance of cancer and high cancer risk belief were more fearful. Detailed inspection of item responses profile provided some support for measurement properties of scales. Conclusion: The internal consistency, and pattern of key associations and discriminability indices provided positive psychometric evidence for these scales. The brief measures of FCR may be considered for audit, screening or routine use in clinical service and research investigations.Publisher PDFPeer reviewe

Gravito-electromagnetic analogies

We reexamine and further develop different gravito-electromagnetic (GEM) analogies found in the literature, and clarify the connection between them. Special emphasis is placed in two exact physical analogies: the analogy based on inertial fields from the so-called "1+3 formalism", and the analogy based on tidal tensors. Both are reformulated, extended and generalized. We write in both formalisms the Maxwell and the full exact Einstein field equations with sources, plus the algebraic Bianchi identities, which are cast as the source-free equations for the gravitational field. New results within each approach are unveiled. The well known analogy between linearized gravity and electromagnetism in Lorentz frames is obtained as a limiting case of the exact ones. The formal analogies between the Maxwell and Weyl tensors are also discussed, and, together with insight from the other approaches, used to physically interpret gravitational radiation. The precise conditions under which a similarity between gravity and electromagnetism occurs are discussed, and we conclude by summarizing the main outcome of each approach.Comment: 60 pages, 2 figures. Improved version (compared to v2) with some re-write, notation improvements and a new figure that match the published version; expanded compared to the published version to include Secs. 2.3 and

EquiFACS: the Equine Facial Action Coding System

Although previous studies of horses have investigated their facial expressions in specific contexts, e.g. pain, until now there has been no methodology available that documents all the possible facial movements of the horse and provides a way to record all potential facial configurations. This is essential for an objective description of horse facial expressions across a range of contexts that reflect different emotional states. Facial Action Coding Systems (FACS) provide a systematic methodology of identifying and coding facial expressions on the basis of underlying facial musculature and muscle movement. FACS are anatomically based and document all possible facial movements rather than a configuration of movements associated with a particular situation. Consequently, FACS can be applied as a tool for a wide range of research questions. We developed FACS for the domestic horse (Equus caballus) through anatomical investigation of the underlying musculature and subsequent analysis of naturally occurring behaviour captured on high quality video. Discrete facial movements were identified and described in terms of the underlying muscle contractions, in correspondence with previous FACS systems. The reliability of others to be able to learn this system (EquiFACS) and consistently code behavioural sequences was high—and this included people with no previous experience of horses. A wide range of facial movements were identified, including many that are also seen in primates and other domestic animals (dogs and cats). EquiFACS provides a method that can now be used to document the facial movements associated with different social contexts and thus to address questions relevant to understanding social cognition and comparative psychology, as well as informing current veterinary and animal welfare practices