The conservation of polymeric materials in museum collections using advanced surface science and surface analysis techniques

This thesis describes the research work performed to determine the effect of conservation cleaning treatments on plastics that might be encountered in the museum environment. As part of this work, surface analysis techniques were used to examine the changes occurring to the surfaces of two plastics, polystyrene and poly(methyl methacrylate), following the application of seven different cleaning treatments. Substrates were analysed using optical microscopy, white light interferometry, scanning electron microscopy, atomic force microscopy and time-of-flight secondary ion mass spectrometry in conjunction with principal component analysis of the data. The use of sophisticated analysis techniques enabled the characterisation of surface changes at the sub-micron scale. Experimental data obtained for virgin sheet polystyrene substrates revealed surface damage due to cleaning in the form of scratching, attributed in part to the mechanical action of the cloth over the substrate. Residues from surfactants were also detected and were still present after repeated rinsing. The addition of an artificial carbonaceous soil to the surface was found to result in the appearance of scratches on PMMA and a change in the topography of scratches formed on polystyrene due to abrasion from the soil. Accelerated ageing of the substrates revealed changes to the plastics’ bulk properties and surface chemistry, as well as the appearance of formations on the polystyrene surface. Further indications of damage caused by cleaning also became apparent with ageing. The cleaning behaviour of aged polystyrene substrates was found to be notably different to that of the unaged substrates. Finally, the initial physical and chemical condition of a real-world object was characterised and its cleaning behaviour evaluated, enabling comparison with the virgin polystyrene substrate. The findings from this work provide valuable information regarding the microscopic changes that can occur to plastic substrates as a result of cleaning and the implications for their future stability.Open Acces

Response of Pacific-sector Antarctic ice shelves to the El Niño/Southern Oscillation.

Satellite observations over the past two decades have revealed increasing loss of grounded ice in West Antarctica, associated with floating ice shelves that have been thinning. Thinning reduces an ice-shelf's ability to restrain grounded-ice discharge, yet our understanding of the climate processes that drive mass changes is limited. Here, we use ice-shelf height data from four satellite altimeter missions (1994-2017) to show a direct link between ice-shelf-height variability in the Antarctic Pacific sector and changes in regional atmospheric circulation driven by the El Niño-Southern Oscillation. This link is strongest from Dotson to Ross ice shelves and weaker elsewhere. During intense El Niño years, height increase by accumulation exceeds the height decrease by basal melting, but net ice-shelf mass declines as basal ice loss exceeds lower-density snow gain. Our results demonstrate a substantial response of Amundsen Sea ice shelves to global and regional climate variability, with rates of change in height and mass on interannual timescales that can be comparable to the longer-term trend, and with mass changes from surface accumulation offsetting a significant fraction of the changes in basal melting. This implies that ice-shelf height and mass variability will increase as interannual atmospheric variability increases in a warming climate

Determining Highway Needs and Setting Road Project Priorities in Indiana Counties - An Executive Summary

This Executive Summary is intended to acquaint county officials with the issues involved and the techniques available to set priorities on county highway segments, should a county wish to implement such procedures in-house or contract with a consultant

Fluid and Diffusion Limits for Bike Sharing Systems

Bike sharing systems have rapidly developed around the world, and they are served as a promising strategy to improve urban traffic congestion and to decrease polluting gas emissions. So far performance analysis of bike sharing systems always exists many difficulties and challenges under some more general factors. In this paper, a more general large-scale bike sharing system is discussed by means of heavy traffic approximation of multiclass closed queueing networks with non-exponential factors. Based on this, the fluid scaled equations and the diffusion scaled equations are established by means of the numbers of bikes both at the stations and on the roads, respectively. Furthermore, the scaling processes for the numbers of bikes both at the stations and on the roads are proved to converge in distribution to a semimartingale reflecting Brownian motion (SRBM) in a $N^{2}$-dimensional box, and also the fluid and diffusion limit theorems are obtained. Furthermore, performance analysis of the bike sharing system is provided. Thus the results and methodology of this paper provide new highlight in the study of more general large-scale bike sharing systems.Comment: 34 pages, 1 figure

Air Navigation

Contains a report on a research project

Advection, diffusion and delivery over a network

Many biological, geophysical and technological systems involve the transport of resource over a network. In this paper we present an algorithm for calculating the exact concentration of resource at any point in space or time, given that the resource in the network is lost or delivered out of the network at a given rate, while being subject to advection and diffusion. We consider the implications of advection, diffusion and delivery for simple models of glucose delivery through a vascular network, and conclude that in certain circumstances, increasing the volume of blood and the number of glucose transporters can actually decrease the total rate of glucose delivery. We also consider the case of empirically determined fungal networks, and analyze the distribution of resource that emerges as such networks grow over time. Fungal growth involves the expansion of fluid filled vessels, which necessarily involves the movement of fluid. In three empirically determined fungal networks we found that the minimum currents consistent with the observed growth would effectively transport resource throughout the network over the time-scale of growth. This suggests that in foraging fungi, the active transport mechanisms observed in the growing tips may not be required for long range transport.Comment: 54 pages including appendix, 10 figure

Conceptualising and teaching biomedical uncertainty to medical students: an exploratory qualitative study

Introduction Certainty/uncertainty in medicine is a topic of popular debate. This study aims to understand how biomedical uncertainty is conceptualised by academic medical educators and how it is taught in a medical school in the UK. Methods This is an exploratory qualitative study grounded in ethnographic principles. This study is based on 10 observations of teaching sessions and seven semi-structured qualitative interviews with medical educators from various biomedical disciplines in a UK medical school. The data set was analysed via a thematic analysis. Results Four main themes were identified after analysis: (1) ubiquity of biomedical uncertainty, (2) constraints to teaching biomedical uncertainty, (3) the ‘medic filter’ and (4) fluid distinction: core versus additional knowledge. While medical educators had differing understandings of how biomedical uncertainty is articulated in their disciplines, its presence was ubiquitous. This ubiquity did not translate into teaching due to time-constraints and assessment strategies. The ‘medic filter’ emerged as a strategy that educators employed to decide what to include in their teaching. They made distinctions between core and additional knowledge which were defined in varied ways across disciplines. Additional knowledge often encapsulated biomedical uncertainty. Discussion Even though the perspective that knowledge is socially constructed is not novel in medical education, it is neither universally valued nor universally applied. Moving beyond situativity theories and into broader debates in social sciences provides new opportunities to discuss the nature of scientific knowledge in medical education. We invite a move away from situated learning to situated knowledge

IoTRec: The IoT Recommender for Smart Parking System

This paper proposes a General Data Protection Regulation (GDPR)-compliant Internet of Things (IoT) Recommender (IoTRec) system, developed in the framework of H2020 EU-KR WISE-IoT (Worldwide Interoperability for Semantic IoT) project, which provides the recommendations of parking spots and routes while protecting users’ privacy. It provides recommendations by exploiting the IoT technology (parking and traffic sensors). The IoTRec provides four-fold functions. Firstly, it helps the user to find a free parking spot based on different metrics (such as the nearest or nearest trusted parking spot). Secondly, it recommends a route (the least crowded or the shortest route) leading to the recommended parking spot from the user’s current location. Thirdly, it provides the real-time provision of expected availability of parking areas (comprised of parking spots organized into groups) in a user-friendly manner. Finally, it provides a GDPR-compliant implementation for operating in a privacy-aware environment. The IoTRec is integrated into the smart parking use case of the WISE-IoT project and is evaluated by the citizens of Santander, Spain through a prototype, but it can be applied to any IoT-enabled locality. The evaluation results show the citizen’s satisfaction with the quality, functionalities, ease of use and reliability of the recommendations/services offered by the IoTRec