Numerical methods in lubrication modelling

Over the past two decades, many numerical schemes have been developed to solve elasto-hydrodynamic lubrication problems. New schemes are continuously being sought with the aim of improving efficiency and robustness. The two main issues of concern when solving these problems are large computational costs and numerical instabilities. The multigrid method, first used by Lubrecht et al. [68] when solving these problems, has proved to be very successful in dealing with the issue of computational costs. Venner [97] took this work further and developed a relaxation scheme which dealt with the issue of instability. However, Venner’s scheme is not only difficult to understand because it is not presented in its entirety but also difficult to implement due its complexity. Hence, a new easy to understand and simple relaxation scheme will be developed and employed in this work, [74], to solve elasto-hydrodynamic lubrication problems. The aim of this work is to present an efficient, robust and general purpose numerical solver for isothermal (Newtonian) elasto-hydrodynamic lubrication circular contact problems. The solver will be based on the FDMG Multigrid Software [92] and the new relaxation scheme. Elasto-hydrodynamic lubrication problems are very important in engineering applications and there is a need for general purpose solvers for industrial applications. The multigrid solver will be used to solve both steady-state and time dependent (transient) problems. A wide range of steady-state problems will be solved and the obtained solutions will be compared with those obtained using other numerical methods, [75]. Up to this date, transient problems are constantly being solved using fixed time step methods where the step sizes are chosen arbitrarily. We will present solutions to both fixed and variable time step methods. The governing equations of transient problems will be written as a system of differential algebraic equations and methods from this area will be employed in variable-step time integration and convergence testing, [90]

High-order discontinuous Galerkin method for elastohydrodynamic lubrication line contact problems

In this paper a high-order discontinuous Galerkin method is used to solve steady-state isothermal line contact elastohydrodynamic lubrication problems. This method is found to be stable across a wide range of loads and is shown to permit accurate solutions using just a small number of degrees of freedom provided suitable grids are used. A comparison is made between results obtained using this proposed method and those from a very large finite difference calculation in order to demonstrate excellent accuracy for a typical highly loaded test problem

A grid-enabled problem solving environment for parallel computational engineering design

This paper describes the development and application of a piece of engineering software that provides a problem solving environment (PSE) capable of launching, and interfacing with, computational jobs executing on remote resources on a computational grid. In particular it is demonstrated how a complex, serial, engineering optimisation code may be efficiently parallelised, grid-enabled and embedded within a PSE. The environment is highly flexible, allowing remote users from different sites to collaborate, and permitting computational tasks to be executed in parallel across multiple grid resources, each of which may be a parallel architecture. A full working prototype has been built and successfully applied to a computationally demanding engineering optimisation problem. This particular problem stems from elastohydrodynamic lubrication and involves optimising the computational model for a lubricant based on the match between simulation results and experimentally observed data

Barriers in phase I cancer clinical trials referrals and enrollment: five-year experience at the Princess Margaret Hospital

BACKGROUND: There is a paucity of literature on the referral outcome of patients seen in phase I trial clinics in academic oncology centres. This study aims to provide information on the accrual rate and to identify obstacles in the recruitment process. METHODS: A retrospective chart review was performed for all new patients referred and seen in the phase I clinic at the Princess Margaret Hospital between January 2000 and June 2005. Data on their demographics, medical history, and details of trial participation or non-entry were recorded. RESULTS: A total of 667 new phase I referrals were seen during the stated period. Of these patients, 197 (29.5%) patients were enrolled into a phase I trial, and 64.5% of them started trial within 1 month of the initial visit. About a quarter (165 of 667) of the patients referred were deemed ineligible at their first visit, with the most frequent reasons for ineligibility being poor performance status, unacceptable bloodwork, too many prior treatments and rapid disease progression. The remaining 305 patients (45.7%) were potentially eligible at their initial visit, but never entered a phase I trial. The main reasons for their non-entry were patient refusal, other treatment recommended first, and lack of available trials or trial spots. CONCLUSION: This study provides information on the clinical realities underlying a referral to a phase I clinic and eventual trial enrollment. Better selection of patients, appropriate education of referring physicians, and opening phase I trials with fewer restrictions on some criteria such as prior therapy may enhance their recruitment rates

Participants’ understanding of informed consent in clinical trials over three decades: systematic review and meta-analysis

Objective To estimate the proportion of participants in clinical trials who understand different components of informed consent. Methods Relevant studies were identified by a systematic review of PubMed, Scopus and Google Scholar and by manually reviewing reference lists for publications up to October 2013. A meta-analysis of study results was performed using a random-effects model to take account of heterogeneity. Findings The analysis included 103 studies evaluating 135 cohorts of participants. The pooled proportion of participants who understood components of informed consent was 75.8% for freedom to withdraw at any time, 74.7% for the nature of study, 74.7% for the voluntary nature of participation, 74.0% for potential benefits, 69.6% for the study’s purpose, 67.0% for potential risks and side-effects, 66.2% for confidentiality, 64.1% for the availability of alternative treatment if withdrawn, 62.9% for knowing that treatments were being compared, 53.3% for placebo and 52.1% for randomization. Most participants, 62.4%, had no therapeutic misconceptions and 54.9% could name at least one risk. Subgroup and meta-regression analyses identified covariates, such as age, educational level, critical illness, the study phase and location, that significantly affected understanding and indicated that the proportion of participants who understood informed consent had not increased over 30 years. Conclusion The proportion of participants in clinical trials who understood different components of informed consent varied from 52.1% to 75.8%. Investigators could do more to help participants achieve a complete understanding

Dimethyl fumarate in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Dimethyl fumarate (DMF) inhibits inflammasome-mediated inflammation and has been proposed as a treatment for patients hospitalised with COVID-19. This randomised, controlled, open-label platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing multiple treatments in patients hospitalised for COVID-19 (NCT04381936, ISRCTN50189673). In this assessment of DMF performed at 27 UK hospitals, adults were randomly allocated (1:1) to either usual standard of care alone or usual standard of care plus DMF. The primary outcome was clinical status on day 5 measured on a seven-point ordinal scale. Secondary outcomes were time to sustained improvement in clinical status, time to discharge, day 5 peripheral blood oxygenation, day 5 C-reactive protein, and improvement in day 10 clinical status. Between 2 March 2021 and 18 November 2021, 713 patients were enroled in the DMF evaluation, of whom 356 were randomly allocated to receive usual care plus DMF, and 357 to usual care alone. 95% of patients received corticosteroids as part of routine care. There was no evidence of a beneficial effect of DMF on clinical status at day 5 (common odds ratio of unfavourable outcome 1.12; 95% CI 0.86-1.47; p = 0.40). There was no significant effect of DMF on any secondary outcome

Space, Ritual, and Religious Experience and the Ottoman hajj, c. 994/1586–1194/1780

This dissertation examines the confessional, devotional, and spatial aspects of the hajj and Ottoman religiosity between 994-1194/1586-1780. It probes the place of the hajj in debates about correct belief and practice after the late sixteenth century and the boundaries within which the hajj itself eventually came to be understood and practiced in this time. It investigates the lived experiences of the thousands of Ottoman pilgrims who undertook the hajj every year, as well as how the hajj was celebrated and memorialised by ḥajjīs and Muslim men and women in locations throughout the Empire. The dissertation further examines how the construction, interpretation, and experience of sacred space in Mecca and Medina evolved across the seventeenth and eighteenth centuries, both correlatively and causatively with other developments in the Empire’s religious landscape. By bringing together questions of confession, devotion, and sacred space in relation to the hajj, the dissertation breaks new ground in our understanding of Ottoman Islam, as well as the history of Muslim religious practice more generally. The dissertation applies a novel methodology to a range of sources that have typically been examined separately, including guidebooks, pilgrimage narratives, and hajj-related objects and images, in order to track the impact of the hajj on multiple registers of Ottoman Islam and vice versa. The dissertation shows that the hajj was as much an arena of confessional polarisation as it was a platform of confessional ambiguity; while a range of actors in the Empire sought to bring hajj practice into line with their own vision of Sunni Islam, others were less concerned with these questions, and were more preoccupied with the opportunities offered by the hajj for varied devotional practice. The dissertation also shows that the increased circulation of pilgrims and objects between the Holy Cities and locations throughout the Empire also resulted in the greater prominence of hajj- and Kaʿba-based piety beginning in the late sixteenth century. Finally, the dissertation shows that the seventeenth century saw a greater emphasis on the sacrality of Mecca itself, especially as aspects of the hajj and the Prophetic ziyāra became localised and as other cities like Cairo and Damascus became more popular sites for sacred practice.Arts and Humanities Research Council (AHRC); Clare College, Cambridge; Scientific and Technological Research Council of Turkey (TÜBİTAK)