Gas Explosions in Dwellings: The Effects of Interconnected Rooms and Obstacles, and the Interpretation of Thermal Damage

There are, on average, over twenty-five accidental gas explosions every year in the UK, each requiring an investigation to determine the origin and cause, in order to satisfy regulatory requirements, or for the purposes of criminal or civil litigation. The most important conclusion to be drawn from the investigation is the identification of the source of the gas release. This is most often determined through interpretation of the severity of pressure and thermal damage to the building and its contents. Guidance in reference books states that gas explosions exhibit characteristic pressure and thermal damage dependent upon the concentration of the fuel/air mixture prior to ignition. It is believed that a number of investigations have resulted in the incorrect apportion of blame as a consequence of the misinterpretation of forensic evidence. The key objectives of the study were to answer three questions. Firstly, can ignition of a fuel lean or fuel rich mixture cause significant structural damage to a building? Secondly, is it possible to determine the gas concentration in a building, prior to ignition, from the severity of the thermal damage? Thirdly, do materials exposed to a transient flame front always exhibit thermal damage? The results of four experimental programmes, and over one hundred and fifty explosion tests, are reported in this thesis. Explosion tests were conducted in explosion chambers ranging from 1 m3 to 180 m3. Experiments were conducted in single and interconnected enclosures, with and without obstacles (including furniture) and with a number of ‘marker’ boards to assess the severity of thermal damage. A number of parameters were varied; including, fuel type, concentration, distribution of gas, congestion, ignition position and vent size and failure pressure. The results demonstrate that under the right conditions, fuel lean and fuel rich explosions can cause overpressures that have the potential to structurally damage buildings (> 200 mbar). A number of mechanisms have been proposed, detailing the manner in which gas explosions propagate from one room to another. This knowledge provides a valuable new insight into how complex a vented explosion in a typical building can be, and how the design and construction of a building can affect the magnitude of the explosion. Several causes of the development of high overpressures have been identified; the ignition of a flammable cloud outside the vent opening(s), the sudden increase in mass combustion as a turbulent mixture in a secondary compartment is ignited by a propagating flame front passing through an interconnecting doorway, and the highly turbulent ‘jetting’ expanding flame, driven by the venting process, propagating through a doorway and towards a vent opening in a secondary enclosure. Evidence is presented that shows it is possible to generate pressures capable of causing structural damage to buildings with volume blockages of as little as 0.57%, if vent openings do not allow sufficient outflow. However, the obstacle geometry, and its location to other obstacles and the enclosure, were found to be critical in the development, or otherwise, of damaging overpressures. The experiments have demonstrated that it is possible to use the severity and extent of thermal damage to wall coverings and wood surfaces, sustained during a gas explosion, to provide useful information on the gas concentration, its distribution throughout the building prior to ignition and the depth of any flammable layer. It is demonstrated that it is possible to assess the severity of the thermal damage to various materials in order to estimate the natural gas concentration prior to the explosion to the nearest 2%. The most suitable materials, in terms of forensic indicators, appear to be softwood covered with either gloss varnish or white oil based gloss paint. Such surfaces are common in buildings as door frames, window frames, etc. However, it is shown that quick drying paints are less susceptible to thermal damage and may cause the misinterpretation of evidence which could lead to an incorrect diagnosis of the origin and cause of an explosion. In tests where a flammable gas/air layer was present, thermal damage may be observed above the nominal layer boundary (for natural gas), down to the lowest level where the concentration was originally above 8% ± 1%. It is shown to be possible to estimate the layer depth from the damage to an accuracy of approximately 15 cm. The results of the experimental programmes presented in this thesis, provide new knowledge and understanding of the development of gas explosions in buildings and how this knowledge may be used to better interpret forensic evidence found in a gas explosion

L’état des études internationales au Canada : un survol de la recherche scientifique

This article depicts the configuration of approaches to the scientific study of foreign policy and international politics in Canada, as represented in a systematic survey of research written in Canada and published in forty scholarly journals, some from as early as 1945 up to 1975. Scientific studies found in this sample were analyzed along four dimensions : theoretical basis ; issue area ; units upon which the investigation is based ; and method of analysis. Scientific study of international relations emerged as a largely recent yet growing phenomenon of the last decade. It constitutes a unique subfield outside the mainstream of research, and is concentrated among a relatively small group of individuals and even fewer institutions. Études internationales emerged as the single most important channel of communication for this subfield in Canad

Age-related differences in motor skill transfer with brief memory reactivation

Motor memories can be strengthened through online practice and offline consolidation. Offline consolidation involves the stabilization of memory traces in post-practice periods. Following initial consolidation of a motor memory, subsequent practice of the motor skill can lead to reactivation and reconsolidation of the memory trace. The length of motor memory reactivation may influence motor learning outcomes; for example, brief, as opposed to long, practice of a previously learned motor skill appears to optimize intermanual transfer in healthy young adults. However, the influence of aging on reactivation-based motor learning has been scarcely explored. Here, the effects of brief and long motor memory reactivation schedules on the retention and intermanual transfer of a visuomotor tracing task are explored in healthy older adults. Forty older adults practiced a virtual star-tracing task either three ( brief reactivation ) or ten ( long reactivation ) times per session over a two-week period. Comparison with a previously reported group of younger adults revealed significant age-related differences in the effect of the motor memory reactivation schedule on the intermanual transfer of the motor task. In older adults, unlike younger adults, no significant between-group differences were found by practice condition in the speed, accuracy, or skill of intermanual task transfer. That is, motor task transfer in healthy younger, but not older, adults appears to benefit from brief memory reactivation. These results support the use of age-specific motor training approaches and may inform motor practice scheduling, with possible implications for physical rehabilitation, sport, and music

Fluoride in the diet of 2-years-old children

Objectives This study aimed to calculate the fluoride concentrations of commonly consumed foods and beverages for 2-years-old children utilizing market basket information for the US Midwest region. Methods Total Diet Study food lists were cross-referenced with National Health and Nutrition Examination Survey—What We Eat in America data to determine the foods and beverages to be included. Fluoride concentrations were determined using a modification of the hexamethyldisiloxane microdiffusion technique. Fluoride concentrations were summarized for each of the food categories. Daily dietary fluoride intake was estimated using a simulation analysis. Results Food and beverage fluoride concentrations varied widely, ranging from nondetectable for some oils and dairy products to more than 3.0 μgF/g food for some processed meats, fish and fruits. The estimated mean (±SD) daily dietary fluoride intake, excluding dentifrice and supplements, was 412±114 μgF/d. The estimated average ingestion for a 2-years-old weighing 12.24 kg was 0.034±0.009 mg/kg/d. A diet based on foods and beverages in the fifth percentile of fluoride intake distribution for an average child would result in 247 μgF/d or 0.020 mg/kg/d, while a diet with foods and beverages in the 95th percentile would result in a total intake of 622 μgF/d or 0.051 mg/kg/d. Conclusions The fluoride concentrations of foods and beverages vary widely, and, if items in the 95th percentile of fluoride intake distribution are ingested, children could consume more fluoride than the recommended 0.05 mg/kg/d. Fluoride intake calculated in this study was higher than historically reported dietary levels

A new Late Pliocene large provannid gastropod associated with hydrothermal venting at Kane Megamullion, Mid-Atlantic Ridge

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Taylor & Francis for personal use, not for redistribution. The definitive version was published in Journal of Systematic Palaeontology 10 (2012): 423-433, doi:10.1080/14772019.2011.607193.A new gastropod, Kaneconcha knorri gen et sp. nov., was found in marlstone dredged from the surface of Adam Dome at Kane Megamullion on the flank of the Mid-Atlantic Ridge in an area of former hydrothermal activity. The snail is interpreted as a large provannid similar to the chemosymbiotic genera Ifremeria and Alviniconcha. This is the first record of presumably chemosymbiotic provannids from the Atlantic Ocean and also the first fossil record of such large provannids associated with hydrothermal venting. Extant Alviniconcha and Ifremeria are endemic to hydrothermal vents in the Pacific and Indian oceans. Kaneconcha differs from Ifremeria in having no umbilicus and a posterior notch, and it differs from Alviniconcha in having the profile of the whorl slightly flattened and having no callus on the inner lip. A dark layer covering the Kaneconcha shell is interpreted here as a fossilized periostracum. The shell/periostracum interface shows fungal traces attributed to the ichnospecies Saccomorpha clava. We hypothesize that large chemosymbiotic provannids (i.e., Kaneconcha, Ifremeria, and Alviniconcha) form a clade that possibly diverged from remaining provannids in the Late Jurassic, with the Late Jurassic/Early Cretaceous Paskentana being an early member.R/V Knorr Cruise 180- 2 to Kane Megamullion was supported by National Science Foundation grant OCE- 0118445. A. Kaim acknowledges support from the Alexander von Humboldt Foundation. B. Tucholke acknowledges support from an Andrew W. Mellon Foundation Award for Innovative Research and from the Deep Ocean Exploration Institute at Woods Hole Oceanographic Institution

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy