Investigations into incidents involving the kindling chain of materials in high-pressure oxygen atmospheres

This thesis is a thorough examination of high-pressure enriched oxygen system design and analysis focussing on material selection and incident investigation. The aims are to develop a model to predict spontaneous ignition temperatures (SIT), enable the use of more accessible measurement apparatus, and to devise a scientific methodology to investigate oxygen incidents. Chapter 1 contains examples of incidents in high-pressure enriched oxygen and outlines current methods of material selection and incident investigation. The major flaws with the current systems are explored and the objectives of this work are identified. Chapter 2 details the current state of the knowledge in relation to oxygen incidents. Materials flammability is explored, and the importance of correct material selection is established. The criteria, standards and test methods currently used to aid this decision are assessed, and the importance of proper oxygen incident investigation is determined. Chapter 3 shows a programme of experimental work with details on the use of different apparatus for the measurement of SITs. Data acquired from the BS 4N 100 bomb test, and pressurised, and ambient, differential scanning calorimetry are recorded. The use of Thermal Desorption/Gas Chromatography is explored to identify polymer evaporation and degradation products. In Chapter 4 a simple model is developed to adapt SIT allowing calculation of the SIT of a non-metal in any pressure or oxygen concentration. Data obtained in chapter 3, and from the literature, is used to validate this model. Data on metals is also collected from the literature to be incorporated into a methodology demonstrating the kindling chain. Chapter 5 covers the development of a ‘tool kit’ for oxygen incident analysis. Understanding of ignition modes, heat transfer modelling, flow diagrams, and the SIT model are used to examine past oxygen incidents, and understand kindling chains. Chapter 6 examines ‘real life’ incidents and applies the Chapter 5 ‘tool kit’ as a clear scientific methodology, identifying likely incident ignition sources and kindling chains. Finally Chapter 7 gives conclusions, identifying the successes and limitations of this work, and points where difficulties were encountered. Areas where further scientific investigation is required are identified

The diagnosis of clinically significant oesophageal Candida infections: a reappraisal of clinicopathological findings

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154961/1/his14063_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154961/2/his14063.pd

Potential hazard consequences to personnel exposed to the ignition of small volumes of weakly confined stoichiometric hydrogen/air mixture

Many studies have been devoted to understanding the consequence of ignition events that could occur as a result of using hydrogen as an alternative to fossil fuels or when hydrogen is present in large scale industrial or nuclear waste sites. Little attention has however, been given to the effect of explosion in small scale operations: this could involve service work with manual handling and manipulation of gas containing packages or vessels. The purpose of this study is to begin to address this knowledge gap and report the results of an experimental program carried out to simulate the effect of localised and weakly confined small volume hydrogen explosions on personal safety. Three aspects of personal injury consequences are considered; injury from shock loading to the head/brain, skin burns and acoustic/hearing damage. It is concluded from ignition and acoustic noise exposure experiments, carried with stoichiometric hydrogen /air mixtures, that injuries arising from shock loading or burns to the skin are less likely than hearing damage. It is suggested that further work should focus on the noise exposure and hearing damage effects of small scale explosions

Application of Bayesian methods and networks to ignition hazard event prediction in nuclear waste decommissioning operations

The major purpose of the study is to examine how Bayesian networks can be used to represent and understand potential ignition scenarios in nuclear waste decommissioning. This is illustrated using a network to represent a situation with stacked storage boxes containing pyrophoric material removed from waste storage silos. Corrosion of this material during storage produces hydrogen which is released through a filter medium into the gap between the boxes. The probabilistic relationships used to indicate dependence between network nodes are expressed by conditional probability tables or C++ coded equations that relate to UK nuclear industry corrosion and storage data. The study focuses on optimal prediction of the likelihood of a flammable hydrogen atmosphere arising in the gap between stacked boxes and the conditions necessary to exceed the lower flammable limit. It is concluded that the approach offers a useful means of easily determining the manner in which varying the controlling parameters affects the possibility of an ignition event. The effect of data variation can be examined at first hand using the supplementary Bayesian Network that accompanies the article

The detection and quantification of food components on stainless steel surfaces following use in an operational bakery

© 2019 Institution of Chemical Engineers Food preparation areas in commercial bakeries present surfaces for continual organic fouling. The detection of retained food components and microorganisms on stainless steel surfaces situated for one month in the weighing in area, pastry and confectionary production areas of a bakery were investigated using different methods. Scanning electron microscopy demonstrated the morphology of the material on the surfaces from all three areas, with the weighing in area demonstrating a more even coverage of material. Differential staining assays demonstrated a high percentage coverage of organic material heterogeneously distributed across the surfaces. Differential staining also demonstrated that the amount of organic material on the surface from the confectionary area was significantly greater than from both the pastry and weighing in areas. Although, UV at 353 nm did not detect residual surface fouling, performance of the UV detection was optimised and demonstrated that the residual organic material on the weighing in area and the pastry samples was best illuminated at 510–560 nm, and from the confectionary area of the bakery at 590–650 nm. ATP bioluminescence revealed the confectionary production area contained the highest level of biofouling. Contact plates determined that only low microbial counts (≤2 CFU/cm2) were recovered from the surfaces. Changes in the physicochemistry (increased hydrophobicity) demonstrated that all the surfaces were fouled (ΔGiwi −26.8 mJ/m2 to −45.4 mJ/m2). Fourier Transform Infra-Red Spectroscopy (FTIR) demonstrated that all the surfaces had retained fats, carbohydrates and proteins. This work suggests that a range of methods may be needed to fully detect organic and microbial fouling

Carbon sequestration in the deep Atlantic enhanced by Saharan dust

sinking rates of particulate organicmatter. Here we present a two-year time series of sediment trap observations of particulate organic carbon flux to 3,000m depth, measured directly in two locations: the dust-rich central North Atlantic gyre and the dust-poor South Atlantic gyre. We find that carbon fluxes are twice as high and a higher proportion of primary production is exported to depth in the dust-rich North Atlantic gyre. Low stable nitrogen isotope ratios suggest that high fluxes result from the stimulation of nitrogen fixation and productivity following the deposition of dust-borne nutrients. Sediment traps in the northern gyre also collected intact colonies of nitrogen-fixing Trichodesmium species. Whereas ballast in Enhanced atmospheric input of dust-borne nutrients and minerals to the remote surface ocean can potentially increase carbon uptake and sequestration at depth. Nutrients can enhance primary productivity, and mineral particles act as ballast, increasing the southern gyre is predominantly biogenic, dust-derived mineral particles constitute the dominant ballast element during the enhanced carbon fluxes in the northern gyre. We conclude that dust deposition increases carbon sequestration in the North Atlantic gyre through the fertilization of the nitrogen-fixing community in surface waters and mineral ballasting of sinking particles

Laser treatment in diabetic retinopathy

Diabetic retinopathy is a leading cause of visual impairment and blindness in developed countries due to macular edema and proliferative diabetic retinopathy (PDR). For both complications laser treatment may offer proven therapy: the Diabetic Retinopathy Study demonstrated that panretinal scatter photocoagulation reduces the risk of severe visual loss by >= 50% in eyes with high-risk characteristics. Pan-retinal scatter coagulation may also be beneficial in other PDR and severe nonproliferative diabetic retinopathy (NPDR) under certain conditions. For clinically significant macular edema the Early Treatment of Diabetic Retinopathy Study could show that immediate focal laser photocoagulation reduces the risk of moderate visual loss by at least 50%. When and how to perform laser treatment is described in detail, offering a proven treatment for many problems associated with diabetic retinopathy based on a high evidence level. Copyright (c) 2007 S. Karger AG, Basel

The detection of the imprint of filaments on cosmic microwave background lensing

Galaxy redshift surveys, such as 2dF, SDSS, 6df, GAMA and VIPERS, have shown that the spatial distribution of matter forms a rich web, known as the cosmic web. The majority of galaxy survey analyses measure the amplitude of galaxy clustering as a function of scale, ignoring information beyond a small number of summary statistics. Since the matter density field becomes highly non-Gaussian as structure evolves under gravity, we expect other statistical descriptions of the field to provide us with additional information. One way to study the non-Gaussianity is to study filaments, which evolve non-linearly from the initial density fluctuations produced in the primordial Universe. In our study, we report the first detection of CMB (Cosmic Microwave Background) lensing by filaments and we apply a null test to confirm our detection. Furthermore, we propose a phenomenological model to interpret the detected signal and we measure how filaments trace the matter distribution on large scales through filament bias, which we measure to be around 1.5. Our study provides a new scope to understand the environmental dependence of galaxy formation. In the future, the joint analysis of lensing and Sunyaev-Zel'dovich observations might reveal the properties of `missing baryons', the vast majority of the gas which resides in the intergalactic medium and has so far evaded most observations

Large Scale Structure of the Universe

Galaxies are not uniformly distributed in space. On large scales the Universe displays coherent structure, with galaxies residing in groups and clusters on scales of ~1-3 Mpc/h, which lie at the intersections of long filaments of galaxies that are >10 Mpc/h in length. Vast regions of relatively empty space, known as voids, contain very few galaxies and span the volume in between these structures. This observed large scale structure depends both on cosmological parameters and on the formation and evolution of galaxies. Using the two-point correlation function, one can trace the dependence of large scale structure on galaxy properties such as luminosity, color, stellar mass, and track its evolution with redshift. Comparison of the observed galaxy clustering signatures with dark matter simulations allows one to model and understand the clustering of galaxies and their formation and evolution within their parent dark matter halos. Clustering measurements can determine the parent dark matter halo mass of a given galaxy population, connect observed galaxy populations at different epochs, and constrain cosmological parameters and galaxy evolution models. This chapter describes the methods used to measure the two-point correlation function in both redshift and real space, presents the current results of how the clustering amplitude depends on various galaxy properties, and discusses quantitative measurements of the structures of voids and filaments. The interpretation of these results with current theoretical models is also presented.Comment: Invited contribution to be published in Vol. 8 of book "Planets, Stars, and Stellar Systems", Springer, series editor T. D. Oswalt, volume editor W. C. Keel, v2 includes additional references, updated to match published versio

Formation of regulatory modules by local sequence duplication

Turnover of regulatory sequence and function is an important part of molecular evolution. But what are the modes of sequence evolution leading to rapid formation and loss of regulatory sites? Here, we show that a large fraction of neighboring transcription factor binding sites in the fly genome have formed from a common sequence origin by local duplications. This mode of evolution is found to produce regulatory information: duplications can seed new sites in the neighborhood of existing sites. Duplicate seeds evolve subsequently by point mutations, often towards binding a different factor than their ancestral neighbor sites. These results are based on a statistical analysis of 346 cis-regulatory modules in the Drosophila melanogaster genome, and a comparison set of intergenic regulatory sequence in Saccharomyces cerevisiae. In fly regulatory modules, pairs of binding sites show significantly enhanced sequence similarity up to distances of about 50 bp. We analyze these data in terms of an evolutionary model with two distinct modes of site formation: (i) evolution from independent sequence origin and (ii) divergent evolution following duplication of a common ancestor sequence. Our results suggest that pervasive formation of binding sites by local sequence duplications distinguishes the complex regulatory architecture of higher eukaryotes from the simpler architecture of unicellular organisms