Particulate Matter Deposition in Indoor Heritage

This Thesis describes the simulation of particulate matter transport and deposition in indoor heritage spaces using Computational Fluid Dynamics (CFD). The mathematical model follows an Eulerian approach, i.e. particles are simulated as a continuous scalar. Deposition fluxes are implemented as a boundary condition in all the walls, and the diffusive and convective terms are modified to account for gravitational settling, near-wall turbulent diffusivity and thermophoresis. We validate this model experimentally using a test tunnel and most importantly, using data collected in real heritage buildings (Apsley House, Wellington Arch, Wellcome Collection and Hampton Court Palaces). This is the first time a CFD model of indoor deposition is validated against direct measurements of deposition fluxes in actual indoor spaces. We compare the model predictions against measurements of deposited and suspended PM, and we obtain suitable boundary conditions using thermal images, wind data and indoor air velocities. The model successfully predicts deposition of particles from 0.1 to 100 microns under different conditions: natural and mechanical ventilation, filtration through leaks or emission by visitors. We also investigate the effects of deposited PM on organic materials, and show how the model can be combined with chemical information and conservation know-how in order to be used as a powerful tool for risk assessment

BERT-Flow-VAE: A Weakly-supervised Model for Multi-Label Text Classification

Multi-label Text Classification (MLTC) is the task of categorizing documents into one or more topics. Considering the large volumes of data and varying domains of such tasks, fully supervised learning requires manually fully annotated datasets which is costly and time-consuming. In this paper, we propose BERT-Flow-VAE (BFV), a Weakly-Supervised Multi-Label Text Classification (WSMLTC) model that reduces the need for full supervision. This new model (1) produces BERT sentence embeddings and calibrates them using a flow model, (2) generates an initial topic-document matrix by averaging results of a seeded sparse topic model and a textual entailment model which only require surface name of topics and 4-6 seed words per topic, and (3) adopts a VAE framework to reconstruct the embeddings under the guidance of the topic-document matrix. Finally, (4) it uses the means produced by the encoder model in the VAE architecture as predictions for MLTC. Experimental results on 6 multi-label datasets show that BFV can substantially outperform other baseline WSMLTC models in key metrics and achieve approximately 84% performance of a fully-supervised model.Comment: 8 pages, 4 figure

Effect of Polyethylene Glycol Treatment on Acetic Acid Emissions from Wood

Acetic acid is known to be emitted from sound wood and can accelerate damage to heritage materials, particularly metals. However, few studies have investigated the extent of acetic acid emissions from archaeological wood. This research utilised Solid-Phase-Micro-Extraction (SPME) GC–MS and lead coupon corrosion to identify volatile emissions from polyethylene glycol (PEG)-treated archaeological wood from the Mary Rose collection and assess if they could cause accelerated damage. In addition, the effect of PEG treatment on acetic acid emissions was investigated using sound wood samples. For sound wood, the PEG treatment acted as a barrier to acetic acid emissions, with higher-molecular-weight PEGs preventing more emissions. Archaeological wood, despite its age and high-molecular-weight PEG treatment, still emitted detectable concentrations of acetic acid. Moreover, they emitted a wider array of compounds compared to sound wood, including carbon disulphide. Like sound wood, when the archaeological wood samples were in a sealed environment with lead coupons, they caused accelerated corrosion to lead. This evidences that archaeological wood can emit high enough concentrations of volatile compounds to cause damage and further investigation should be performed to evaluate if this can occur inside museum display cases

Measuring the impact of COVID-19 on heritage sites in the UK using social media data

The COVID-19 pandemic has had a profound impact on almost all aspects of society. Cultural heritage sites, which are deeply intertwined with the tourism industry, are no exception. The direct impacts of the virus on the population, as well as indirect impacts, such as government-mandated measures including social distancing, face coverings, and frequent temporary closures of sites, have greatly impacted visitor experiences at heritage sites. To quantitatively evaluate the impact of these measures from the perspective of visitors, we collected 1.4 millions visitor reviews from the Google Maps platform for 775 heritage sites. We analyzed visiting rates using the number of online reviews as a proxy and adopt state-of-the-art natural language processing techniques to more deeply understand visitor perception of preventive measures put in place to control the spread of COVID-19. Our findings reveal that even if visitor focus on COVID-19 has significantly decreased, there may still be notable difference between actual and expected number of reviews, suggesting that visitor involvement (e.g., number of visitors) for cultural heritage sites, especially urban indoor sites, needs more time to recover. Our findings further show that most comments by visitors to sites were associated with negative sentiment toward restricted access, but recognized the necessity of other safeguarding measures (e.g., social distancing and the requirement for face coverings). Moreover, they exhibited negative sentiment towards staff or other visitors who did not adhere to these measures. We make specific recommendations for heritage sites to adapt to the COVID-19 pandemic and a more general observation that the method used to gather information from online reviews in this paper will be effective in measuring visitor perceptions towards specific aspects of heritage sites, particularly in capturing changes in perception before and after unexpected or disruptive events at heritage sites

Modelling and performance evaluation of storage enclosures

A model of moisture and heat transport was used to study the performance of storage enclosures. This paper examines several modelling approaches and presents the benefits and drawbacks of a ‘simple’ model which requires few input parameters. As a result, users do not need to measure many material properties, but some quality of the predictions is lost. The model is used to explore the balance of moisture exchange through ventilation holes and diffusion, the presence of buffering material inside enclosures and the effect of wall thickness. The predictions correspond well to experimental data measured in storage enclosures and a historic building. However, in order to bring modelling to the point where it can be used to engineer better enclosures, further research is needed. Experimental validation needs to be extensive and the limits of applicability of the model need to be clearly identified

Evolution and Classification of Myosins, a Paneukaryotic Whole-Genome Approach

notes: PubMed ID: 24443438© The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.Myosins are key components of the eukaryotic cytoskeleton, providing motility for a broad diversity of cargoes. Therefore, understanding the origin and evolutionary history of myosin classes is crucial to address the evolution of eukaryote cell biology. Here, we revise the classification of myosins using an updated taxon sampling that includes newly or recently sequenced genomes and transcriptomes from key taxa. We performed a survey of eukaryotic genomes and phylogenetic analyses of the myosin gene family, reconstructing the myosin toolkit at different key nodes in the eukaryotic tree of life. We also identified the phylogenetic distribution of myosin diversity in terms of number of genes, associated protein domains and number of classes in each taxa. Our analyses show that new classes (i.e., paralogs) and domain architectures were continuously generated throughout eukaryote evolution, with a significant expansion of myosin abundance and domain architectural diversity at the stem of Holozoa, predating the origin of animal multicellularity. Indeed, single-celled holozoans have the most complex myosin complement among eukaryotes, with paralogs of most myosins previously considered animal specific. We recover a dynamic evolutionary history, with several lineage-specific expansions (e.g., the myosin III-like gene family diversification in choanoflagellates), convergence in protein domain architectures (e.g., fungal and animal chitin synthase myosins), and important secondary losses. Overall, our evolutionary scheme demonstrates that the ancestral eukaryote likely had a complex myosin repertoire that included six genes with different protein domain architectures. Finally, we provide an integrative and robust classification, useful for future genomic and functional studies on this crucial eukaryotic gene family.LeverhulmeBBSRCERCMINECONERCGordon and Betty Moore Foundatio

The effect of particulate matter on paper degradation

Background: In this work we explore the chemical effects of particulate matter on paper. We exposed paper made of pure cellulose to the environment in different locations in central London, outdoors (in sheltered conditions) and indoors, for a period of up to 6 months. We monitored particulate matter (PM) deposition by counting the particles deposited every month with a scanning electron microscope. We analysed elemental composition of the deposited particles using inductively coupled plasma mass spectrometry. After accelerated degradation of the exposed samples, we determined the degree of polymerisation using viscometry. Results: We observed higher deposition rates and higher metal concentration outdoors than indoors. Elemental analysis of the deposited particles revealed the presence of some transition metals (Fe, Cu, Cr) that can contribute to the degradation of cellulose fibres through the Fenton reaction. By comparing the degree of polymerisation of pro‑ tected, unprotected and unexposed samples we could determine the relative contribution of PM deposition on the increase of the degradation rate. We found that the surface concentration of iron correlates with the reduction in the degree of polymerisation of the exposed paper. Conclusions: The results suggest that the presence of Fenton metals in PM has a significant effect on the accelera‑ tion of the degradation of cellulose. However, we estimate that this will unlikely occur at the levels of area coverage by PM that are typically avoided in indoor heritage through preventive maintenance and cleaning

Accumulation of wear and tear in archival and library collections. Part I: exploring the concepts of reliability and epidemiology

Wear and tear is the outcome of degradation most frequently reported in assessments of archival and library collections. It is also problematic to study in controlled experiments, due to the difficulty in reproducing the conditions in which original objects are kept and used in archives and libraries. Hence, data collected from actual collections, for instance during surveys, could provide the evidence on how wear and tear occurs. However, to be useful, such data need to be purposely collected and analysed: unlike the usual collection surveys, the aim is not to quantify the prevalence of a certain damage type but to provide evidence on how such damage occurs. In this paper we explore whether two approaches used in other disciplines could be useful: reliability engineering, the method that deals with failure in complex systems, and epidemiology, which explores diseases in defined populations. We show that based on reliability engineering we can decide which data related to the causes of mechanical failure should be collected during collection surveys, while using epidemiology we can develop the study design and the data analysis needed to study the relationship between mechanical failure, and the factors that might affect the degree of failure. The results of epidemiological studies in heritage collections could provide quantitative evidence of patterns of decay in collections, and corroborate the qualitative analysis provided by reliability. The results can directly support collection management decisions or can be used in mathematical models in which the effect of preservation measures is explored

BIM for heritage science: a review

Building Information Modelling (BIM) is a new process that is spreading in the Architecture, Engineering and Construction field. It allows the creation of virtual building models, which can be linked to numerical data, texts, images, and other types of information. Building components, such as walls, floors, etc. are modelled as “smart objects”, i.e. they are defined by numerical parameters, such as dimensions, and are embedded with other kinds of information, such as building materials and properties. Stored data are accessible and modifiable by all different professionals involved in the same project. The BIM process has been developed for new buildings, and it allows to plan and manage the whole building life-cycle. BIM for built heritage has started to be researched recently, and its use is still not widespread. Indeed, built heritage is characterised by complex morphology and non-homogeneous features, which clash with BIM’s standardised procedures. Moreover, to date, BIM does not allow fully automated procedures to model heritage buildings. This review focuses on the survey and digitisation phases, which can be seen as the initial phases of application of BIM in conservation projects. It also briefly covers the modelling stage. Here we present the main methodologies developed for BIM for built heritage. Issues about digitisation are also highlighted, principally in connection with the unavailability of automated processes. During the last 10 years, research has led to promising results; for example, videogame interfaces have been used to simulate virtual 3D tours that display in a single interface the 3D model and the database containing metadata, and new software plug-ins have been developed, to easily create “smart objects”. Nevertheless, further research is needed to establish how BIM can support the practice of building conservation. There is a gap in BIM’s information holding capacities, namely the storage of cultural and historical documentation, as well as monitored and simulated data relevant for preventive conservation. Future work should focus on the development of new tools that will be able to store and share all the relevant metadata