4 results on '"Letchford, Nicholas"'
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2. Modelling the COVID-19 pandemic in context: an international participatory approach
- Author
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Aguas, Ricardo, White, Lisa, Hupert, Nathaniel, Shretta, Rima, Pan-Ngum, Wirichada, Celhay, Olivier, Moldokmatova, Ainura, Arifi, Fatima, Mirzazadeh, Ali, Sharifi, Hamid, Adib, Keyrellous, Sahak, Mohammad Nadir, Franco, Caroline, Coutinho, Renato, Ariana, Proochista, Hancock, Penny, Kraenkel, Roberto A, Saralamba, Sompob, Luangasanatip, Nantasit, Silal, Sheetal Prakash, Norman, Jared, Hounsell, Rachel, Tun, Sai, Aung, Yu Nandar, Emmanuel, A Bakare, Getachew, Biniam, Adele, Sandra, Omoleke, Semeeh A, Zaman, Rashid U, Letchford, Nicholas, Parker, Daniel M, Pokharel, Sunil, Lata, Dipti, Chen, Siyu, Kyaw, Shwe Sin, Lubis, Inke ND, Alona, Ivana, Medina, John Robert C, Mercado, Chris Erwin G, Eybpoosh, Sana, Mamadu, Ibrahim, Marzouk, Manar, de Colombi, Nicole Feune, Suárez-Idueta, Lorena, Obando, Francisco, Freitas, Luzia, Klein, Michael G, Scales, David, Aizhan, Dooronbekova, Zhumalieva, Chynar, Estebesova, Aida, Mukambetov, Aibek, Ibragimov, Shamil, Kubatova, Aisuluu, Chanthavialy, Phetsavanh, Salim, Amel H, Venkatesan, Sudhir, Sarin, KC, Shrestha, Priyanka, Saeedzai, Sayed Ataullah, Hsieh, Jenny, Soukavong, Mick, Yunanda, Yuki, Harsono, Handoyo, Fariba, Mahnaz Hossain, Mabombo, Viviana, Advani, Nicole, Jabin, Nusrat, Naidoo, Reshania, Wattanasri, Parinda, Nwosu, Amen-Patrick, and Obiesie, Sopuruchukwu
- Subjects
Health Services and Systems ,Public Health ,Health Sciences ,Generic health relevance ,Good Health and Well Being ,COVID-19 ,Culture ,Delivery of Health Care ,Global Health ,Health Policy ,Humans ,Internationality ,Models ,Theoretical ,Pandemics ,Research ,SARS-CoV-2 ,Social Class ,Uncertainty ,health policy ,respiratory infections ,control strategies ,SARS ,CoMo Consortium ,Health services and systems ,Public health - Abstract
The SARS-CoV-2 pandemic has had an unprecedented impact on multiple levels of society. Not only has the pandemic completely overwhelmed some health systems but it has also changed how scientific evidence is shared and increased the pace at which such evidence is published and consumed, by scientists, policymakers and the wider public. More significantly, the pandemic has created tremendous challenges for decision-makers, who have had to implement highly disruptive containment measures with very little empirical scientific evidence to support their decision-making process. Given this lack of data, predictive mathematical models have played an increasingly prominent role. In high-income countries, there is a long-standing history of established research groups advising policymakers, whereas a general lack of translational capacity has meant that mathematical models frequently remain inaccessible to policymakers in low-income and middle-income countries. Here, we describe a participatory approach to modelling that aims to circumvent this gap. Our approach involved the creation of an international group of infectious disease modellers and other public health experts, which culminated in the establishment of the COVID-19 Modelling (CoMo) Consortium. Here, we describe how the consortium was formed, the way it functions, the mathematical model used and, crucially, the high degree of engagement fostered between CoMo Consortium members and their respective local policymakers and ministries of health.
- Published
- 2020
3. Cavitation in lubricating films
- Author
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Letchford, Nicholas, Vella, Dominic, Breward, Chris, and Howell, Peter
- Subjects
621.8 - Abstract
Wear and friction are signicant problems in machinery. A particularly harsh environment is the space between the piston ring and cylinder wall of a combustion engine. Lubricant lms are commonly used to mitigate these eects, separating metal to metal contact. The experiments of Zhu and Granick (Langmuir, 18, 2002) attempt to understand how surfactants change the behaviour of lubricating lms. They claim surfactants that have adsorbed onto a solid surface cause the uid to slip past the surface. We hypothesize that their observations could instead be caused by the liquid cavitating. We develop a mushy region model, based on the work of Ockendon, Howison, and Lacey (Q J Mech Appl Math, 56, 2003), to represent the cavitated region which we assume is composed of liquid, vapour, and gas. We show that the normal force predicted by the model gives a good t to experimental observations. We also model experiments of Professor J. Nouri, who investigated the formation of gaseous cavities in a slider bearing, again using a mushy region model. We present a detailed asymptotic analysis of the model and show how the solution changes from being quasi-steady to dynamic as the velocity of the bottom surface changes sign. We show that numerical solutions of the model are in good qualitative agreement with experimental measurements, yet several persistent discrepancies remain. We suggest possible causes of these discrepancies, and estimate the eects that various physical phenomena might have on the experiments. By modifying the mushy region model to study the impact of various additional processes on the lm, we attempt to explain specic dierences between the model and the experimental results. We also extend the model to include other eects so it is more representative of the operating conditions experienced by lubricants in engines.
- Published
- 2016
4. INVISCID AND VISCOUS MODELS OF AXISYMMETRIC FLUID JETS OR PLUMES
- Author
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LETCHFORD, NICHOLAS A., primary, FORBES, LAWRENCE K., additional, and HOCKING, GRAEME C., additional
- Published
- 2012
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