2,861 research outputs found

    Evacuação de Edifícios – Caso de estudo de um edifício escolar

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    O objetivo deste trabalho é o levantamento dos aspetos que influenciam o tempo de evacuação num edifício escolar, desde o comportamento humano às caraterísticas físicas do edifício e às metodologias possíveis de adotar para a gestão da emergência, com vista a calcular o tempo necessário e disponível para a evacuação do referido edifício. A evacuação de edifícios em situação de incêndio tem como propósito a proteção da vida humana que é inseparável das condições de emergência as quais são afetadas por fatores de difícil determinação e que necessitam de ser definidos para estimar o tempo e as condições de evacuação.info:eu-repo/semantics/publishedVersio

    Development of Flame Retardant and Antibacterial Dual Functionalised Flexible Polyurethane Foam

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    Flexible Polyurethane foam (PUF), with its unique properties, such as lightweight and softness, has been utilised extensively. Nevertheless, owing to the intrinsic high flammability and low ignition temperature, PUF-associated fire risks are always a concern. During PUF’s combustion, excessive heat and toxic gases can be generated, threatening the health and life of human beings and causing huge property loss. Consequently, improving the flame retardancy of the PUF is of importance. Later, the global COVID-19 pandemic broke out in 2019, leading to the public’s increased awareness of maintaining good hygiene conditions. Since PUF products are frequently in contact with humans daily, rendering the PUF with bacterial-killing properties should also be addressed. This dissertation delivers studies on introducing flame retardancy to the PUF via a surface engineering method named the layer-by-layer (LbL) assembly. Due to the consequent COVID-19 situation, this thesis expands the investigations to endow the PUF with antibacterial performances. Preliminary research on fabricating a newly emerged two-dimensional material called MXene (Ti3C2) and chitosan (CH) as flame retardants (FRs) to impart fire safety performances to the PUF was conducted. With only 6.9 wt.% mass added to the PUF, unprecedented fire resistance and smoke suppression properties were received. It was revealed that the FR mechanism was ascribed to the hybrid coating’s excellent barrier and carbonisation effects. Further investigations on improving the PUFs’ biodegradability identified synergistic effects between the MXene with the CH and phytic acid, demonstrating the great potential for reducing the toxicity and improving the eco-friendliness of the PUFs. Additionally, this thesis analysed the FR and antibacterial dual-functionalised PUFs. The synthesised MXene, CH, and silver ion hybridised coating endows the foam with exceptional bactericidal properties with decreases of 99.7 % in gram-negative bacteria and 88.9 % in gram-positive bacteria compared with the unmodified counterpart. Excellent flame retardancy possessed by the dual-functionalised PUFs was discovered. The compatibility of the two functional coatings was evaluated and confirmed. The results manifest the great potential for eradicating the fire risks of PUFs and providing traditional PUF products with antibacterial properties, further expanding PUF’s applications

    Biopolymer photonics: from nature to nanotechnology

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    Biopolymers offer vast potential for renewable and sustainable devices. While nature mastered the use of biopolymers to create highly complex 3D structures and optimized their photonic response, artificially created structures still lack nature's diversity. To bridge this gap between natural and engineered biophotonic structures, fundamental questions such as the natural formation process and the interplay of structural order and disorder must be answered. Herein, biological photonic structures and their characterization techniques are reviewed, focusing on those structures not yet artificially manufactured. Then, employed and potential nanofabrication strategies for biomimetic, bio-templated, and artificially created biopolymeric photonic structures are discussed. The discussion is extended to responsive biopolymer photonic structures and hybrid structures. Last, future fundamental physics, chemistry, and nanotechnology challenges related to biopolymer photonics are foreseen.Peer ReviewedPostprint (published version

    Exoteric effects at nanoscopic interfaces - Uncommon negative compressibility of nanoporous materials and unexpected cavitation at liquid/liquid interfaces

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    This PhD thesis is devoted to the investigation of some peculiar effects happening at nanoscopic interfaces between immiscible liquids or liquids and solids via molecular dynamics simulations. The study of the properties of interfaces at a nanoscopic scale is driven by the promise of many interesting technological applications, including: a novel technology for developing both eco-friendly energy storage devices in the form of mechanical batteries, as well as energy dissipation systems and, in particular, shock absorbers for the automotive market; biomedical applications related to cavitation, such as High-Intensity Focused Ultrasound (HIFU) ablation of cancer tissues and localised drug delivery, and many more. The kinetics of phenomena taking places at these scales is typically determined by large free-energy barriers separating the initial and final states, and even intermediate metastable states, when they are present. Because of such barriers, the phenomena we are interested in are "rare events", i.e. the system attempts the crossing of the barrier(s) many times before finally succeeding when an energy fluctuation makes it possible. At the same time, the magnitude of the barrier is determined by the energetics and dynamics of atoms, which forces us to model the system by taking into account both the femtosecond atomistic timescale and the timescale of the relevant phenomena, typically exceeding the former by several orders of magnitude. These longer timescales are inaccessible to standard molecular dynamics, so, in order to tackle this issue, advanced MD techniques need to be employed. The thesis is divided into two parts, corresponding to the main lines of research investigated, which are (I) the interfaces between water and complex nanoporous solids, and (II) planar solid-liquid and liquid-liquid interfaces. Anticipating some results, atomistic simulations helped uncovering the microscopic mechanism behind the (incredibly rare!) giant negative compressibility exhibited by the ZIF-8 metal organic framework (MOF) upon water intrusion. Molecular dynamics simulations also supported experimental results showing how it is possible to change the intermediate intrusion-extrusion performance of ZIF-8 by changing its grain morphology and arrangement, from a fine powder to compact monolith. Free-energy MD calculations allowed to explain the exceptional stability of surface nanobubbles in water, at undersaturated conditions, on a surprisingly wide variety of substrates, characterized by disparate hydrophobicities and gas affinities; and yet, how they catastrophically destabilize in organic solvents. Finally, through simulations, some light was shed upon the working mechanism behind the novelly discovered phenomenon of how the interface between two immiscible liquids can act as a nucleation site for cavitation

    Investigating Middle Stone Age foraging behaviour in the Karoo, South Africa

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    The Middle Stone Age (MSA) in Africa ~500- 50 kyr is recognised as a key time-period associated with important developments in hominin evolution, including the appearance of earliest genetic markers for Homo sapiens. Despite advances, our knowledge of the behaviour of hominins during this period is limited, especially for the early MSA (EMSA) pre-160ka. This study presents new data on animal bones recovered at the Bundu Farm site, in the upper Karoo region of the Northern Cape, South Africa, dated to circa ~300ka and found in association with EMSA type lithic facies, burning and hearth-like features. Previous analysis of the Bundu fauna compared the site to a G/wi hunter-gatherer 'biltong' processing locale, implying primary access to animal carcasses and socially complex hunting behaviour, circa 400-300 ka. An interpretation at odds with other interpretations of the EMSA data that suggest limited hunting and social complexity, and which would therefore have significant implications for MSA archaeology. To test the biltong hypothesis my study presents new data on the fracture characteristics of non-fresh animal bone broken by hammerstone and new environmental data for the site from an analysis of ostrich eggshell isotopes. Experimental and environmental data are used to provide a new interpretation of the Bundu fauna and my conclusion is that the data while not supporting the biltong model, does indicate evidence of delayed communal food consumption, use of fire and the transformation of foodstuffs into meals presaging and echoing social and ecological adaptations seen in the later MSA and LSA. The data also highlights a greater role for carnivores in the accumulation of the faunal assemblage and expedient hominin foraging similar to the preceding ESA and brings attention to the ecological relationships between hominins and carnivores in a Pleistocene Karoo environment that was markedly different from that of today. The study therefore rejects the biltong hypothesis for Bundu Farm as both inconsistent with likely EMSA social structures and ecology and instead proposes the site as evidence for novel behaviour indicative of a transition from ESA to MSA lifeways. The Bundu Farm site reflecting a rare archaeological occurrence where the shift in the behavioural trajectory that led to our species is observed

    Pure Pints and Preservative Pyres: Archaeobotanical Investigations at the Brainerd Brewery Site (21CW0337)

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    The Brainerd Brewery, located in Brainerd, MN, was first opened in 1872 and was shut down in 1914. The numerous owners of this brewery were all first- or second-generation German immigrants who brought the German tradition of brewing beer to the City of Brainerd. The goal of the research at this brewery was to determine if the German American brewery owners were following traditional German brewing practices that followed the German Purity Law of 1516, or Reinheitsgebot, which states only water, barley and hops shall be used to make beer. To make this determination a combined methodology of using archaeological excavations and historical research was implemented. The excavations focused on the recovery of barley grains, and/or any adjuncts used to make beer and consisted of eight shovel tests and two excavation units. The historical research involved accessing historical newspapers, census records, County Recorder’s Office property owner records, and Sanborn Fire Insurance Maps. The archaeological investigation at the brewery recovered 65 charred grain kernels and one charred rachis as well as numerous artifacts associated with the brewery such as glass, nails, dishware, building materials, and a clay pipestem. The historical documents were used for the historical background of the brewery owners and the brewery as well as to determine what the German American brewery owner’s experience was in America, and to identify how beer was being made in the late 1800s. The archaeological evidence combined with the historical research indicates the Brainerd Brewery owners were likely not brewing beer according to Reinheitsgebot but were still practicing the German tradition of brewing beer

    Computational and experimental studies of selected magnesium and ferrous sulfate hydrates: implications for the characterisation of extreme and extraterrestrial environments

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    Magnesium sulfate hydrates are considered important rock-forming minerals on the outer three Galilean moons of Jupiter (i.e., Europa, Ganymede, Callisto) and, alongside ferrous sulfate hydrates, are promising candidate minerals for the widespread sulfate deposits that occur in the equatorial region of Mars. In such extraterrestrial environments, these minerals experience extreme high-pressure conditions in the interiour of the Galilean moons and low temperature conditions on the surface of these moons and Mars. The aim of this thesis is to understand the structural stability, compressibility, and thermal expansion of these compounds in such extreme environments and aid their identification in ongoing and future space missions. Most magnesium sulfate hydrates lack accurate reference elastic tensors, which hinders their seismological identification in lander missions on the icy moons of the outer solar system, as envisioned for the near future. In this thesis, the accuracy of recent advancements in density functional theory to predict the compressibility and elastic constants of icy satellite candidate minerals (i.e., epsomite (MgSO₄·7H₂O), gypsum (CaSO₄·2H₂O), carbon dioxide (CO₂), and benzene (C₆H₆)) was assessed by benchmarking them against experimental reference data from the literature. Key findings are that density functional theory calculations do not yield elastic constants accurate enough to be used as a reference for the seismic exploration of icy moons. However, the bulk compressibility of such materials is very accurately reproduced by density functional theory, which was therefore used to predict the compressibility of the icy satellite candidate minerals starkeyite (MgSO₄·4H₂O) and cranswickite (MgSO₄·4H₂O). Knowledge of the compressibility of such minerals is critical to model mantle processes (e.g., salt diaprisim, plate tectonics, subduction) and the density structure of the outer three Galilean moons. The thermal expansion and structural stability of three sulfate minerals (i.e., rozenite (FeSO₄·4H₂O), starkeyite, and cranswickite) was characterised for the first time using neutron diffraction. Cranswickite transforms to starkeyite at 330 K, well above the maximum surface temperature of 308 K hitherto reported on Mars. Starkeyite likely undergoes a structural phase transition at around 245 K. The structure of this proposed low-temperature polymorph could not be determined but would be of great interest since the temperature drops below 245 K on equatorial Mars at night-time. Starkeyite was also studied by means of synchrotron X-ray diffraction but suffered radiation damage. No phase transition was observed in rozenite from 290 – 21 K, which contrasts with Raman data reported in the literature, where sharpening of vibrational modes upon cooling was misinterpreted as mode splitting and evidence for two phase transitions at temperatures relevant to the Martian surface. First-principles phonon frequency calculations provide evidence supporting the absence of vibrational mode splitting. A workflow to obtain reliable reference Raman spectra for space exploration was proposed and an optical centre stick for the simultaneous acquisition of neutron diffraction and Raman spectroscopy data at the HRPD instrument was commissioned. Lastly, the structure of a polymorph of hexahydrite (MgSO₄·6H₂O), most recently proposed in the literature, was shown to be unambiguously wrong

    Biophysical Insights into Peptide and Alcohol Perturbations on Biomimetic Membranes

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    Biological membranes exist in every domain of life. Life exists due to the presence of these special structures for which we take for granted. They are composed of fatty lipids and workhorse proteins and act as the premier interface of biological processes. Due to the sheer quantity and complexity within their thin boundary, studying their actions and properties pose challenges to researchers. As a result, simplified biomembrane mimics are employed regularly. We will use several types of biomembrane mimics to understand fundamental properties of membranes. In the present thesis, we also attempt to move beyond the canonical structure-based theories upon which a majority of biophysical studies are predicated upon. This has been the case as structural quantities still greatly inform on the conditions of the bilayer system, yet the exact lipid distribution and movement are less studied. We will focus upon the movement and organization of phospholipids using a bounty of biophysical techniques, such as small angle neutron scattering, molecular dynamics, and more. The results will be interpreted to show how phospholipid mobility fits into the greater membrane framework

    Representing Reactive attachment disorder in contemporary fiction: creating new paths for neurodiverse characters

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    The first element of this work is a novel titled June in the Garden, which follows a neurodiverse protagonist with a diagnosis of reactive attachment disorder. The next section of the exegesis will provide insight into her atypical profile, particularly her traits of social disinhibition, an absence of emotion, affected cognitive processing and reasoning skills, and an inability to initiate and maintain relationships with others. The second element will include two parts: (1) a critical analysis of key diagnostic terms used in the clinical field to describe disorders relating to social-emotional detachment and disengagement, specifically reactive attachment disorder (RAD); (2) discussions on the current depiction of social-emotional detachment and, more broadly, of neurodiversity in contemporary fiction. This second part will argue that the two main pathways to depict a detachment disorder, like RAD, is heterogeneous characterisation, defined by common patterns that are exhibited in the novels selected, and typography, defined by unconventional text arrangement or a presence of visuals on the printed page. Aspects of typography will include deconstruction of the standard print form to allow for creative formatting, such as increased spacing, incomplete sentences, blank pages, and bolding of words. Another aspect will include the addition of specific visuals, such as conceptual word sharks (The Raw Shark Texts, Steven Hall, 2007), black and white photographs (Extremely Loud and Incredibly Close, Jonathan Safran Foer, 2005), and mathematical formulas and blueprints (The Curious Incident of the Dog in the Night-Time, Mark Haddon, 2003). These two methods, heterogeneous characterisation and typography, will explain my creative process for developing a neurodiverse protagonist, showing connections between my work and the work of other fiction writers. However, primarily this research will convey a new pathway for an atypical protagonist with a disorder relatively unknown in the wider community, to recontextualise the presentation of social-emotional detachment in fiction. I also hope to highlight the gaps in RAD research, particularly at the adult level, and to show how RAD can be portrayed realistically in a contemporary novel, without being too ‘gimmicky’

    Developing a novel and versatile approach to study populations of microbes on surfaces

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    Spatial structure, for example regarding antibiotic gradients, is an important topic of investigation in microbial ecology and evolution. Experiments investigating pop- ulation dynamics in spatially-structured environments are often performed on agar plates. Whilst inexpensive and straightforward, these provide only rudimentary temporal and spatial control of environmental conditions. In chemostats and microfluidic devices, for well-mixed and micrometre-scale environments, respectively, regulating media inflow and outflow enables environ- mental control. We combine proven use of agar surfaces with such flow-enabled control in a novel, low-cost fluidic device; the device comprises an elastomer supporting base with a thin agar sheet on top on which microbes grow. Indented channels in the base allow flow of media/antibiotics below the agar surface. A Raspberry-Pi-operated camera allows for time-lapse imaging suitable for quantita- tive image analysis. As a proof of principle, we used our device for extended and robust growth of non-motile E. coli and motile P. aeruginosa maintaining the initial speed with which colonies propagate over three days, whilst a continual speed decrease occurred on agar plates. Guided by simulations of flow and diffusion, we then used the device to create stable antibiotic gradients within the agar. Along these gradients, we found P. aeruginosa exhibit unique microbial growth patterns with local adaptations. Because flow below the agar surface can be controlled spatially and temporally, the device promises a range of applications for studying microbial ecology and evolution in spatially continuous environments at a substrate-air interface.Engineering and Physical Sciences Research Council (EPSRC
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