Doctoral Dissertations (FSCI)

Permanent URI for this collectionhttps://hdl.handle.net/10155/402

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Analysis of the volatile organic compounds produced by the decomposition of pig carcasses and human remains
(2013-03-01) Stadler, Sonja; Forbes, Shari; Desaulniers, Jean-Paul
Complex processes of decomposition produce a variety of chemicals as soft tissues and their component parts are degraded. Among others, these decomposition by-products include volatile organic compounds (VOCs) responsible for the odour of decomposition. Human remains detection (HRD) canines utilize this odour signature to locate human remains during police investigations and recovery missions in the event of a mass disaster. Currently, it is unknown which compounds or combinations of compounds are recognized by the HRD canines. In this study decomposition VOCs were collected from the decomposition headspace of pig carcasses and were analyzed using thermal desorption gas chromatography mass spectrometry (TD-GC-MS). The difficulties associated with the non-target analysis of complex samples led to the further analysis of decomposition odour using a novel application of thermal desorption coupled to comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (TD-GCxGC-TOFMS). The additional peak capacity and spectral deconvolution of the GCxGC-TOFMS system generated a characteristic profile of decomposition VOCs across the various stages of soft tissue decomposition. The profile was comprised of numerous chemical families, particularly alcohols, carboxylic acids, aromatics and sulfides. Characteristic compounds identified in this study included 1-butanol, 1-octen-3-ol, 2-and 3-methyl butanoic acid, hexanoic acid, octanal, indole, phenol, benzaldehyde, dimethyl disulfide and trisulfide, which represent potential target compounds of decomposition odour. Currently there is a demand for improved canine training aids and pig carcasses have been proposed as an alternative due to their acceptance as human body analogues. This work investigated the similarities in the decomposition odour profile of pig carcasses and human remains through surface decomposition trials and comparisons to the published literature. It was determined that pig carcasses cannot be eliminated as potential human decomposition odour mimics. Additionally, following the examination of commercially available synthetic training aids, pig carcasses demonstrated a more suitable profile for the training of cadaver dogs. Further investigation into the chemical composition of decomposition odour utilizing TD-GCxGC-TOFMS will aid in determining the signature of human decomposition odour and facilitate the comparisons of these profiles between environments, individuals and species.
The synthesis and in vitro evaluation of siRNAs modified at the backbone with a novel triazole-based internucleotide linkage and abasic alkyl-chain linkages of varying length
(2013-04-01) Efthymiou, Tim; Desaulniers, Jean-Paul
For over a decade, the use of double-stranded short interfering RNAs (siRNAs) to silence the expression of genes associated with disease at the translational level has gained much attention. Using a highly conserved endogenous pathway within cells, siRNA technology displays a high degree of target specificity and potency. However, traits required for the successful design of siRNA-based therapeutics such as resistance to nuclease-mediated degradation, improved cell membrane permeability and reduced off-target toxicity, are compromised by the native structure of duplex RNA′s charged backbone. This study therefore focused on synthesizing novel and neutrally-charged triazole-linked nucleoside dimer analogs which were incorporated throughout siRNA duplexes using DMTphosphoramidite chemistry, in order to attenuate the negative contributions of RNA′s native backbone. In order to further elucidate the mechanism of the RNA interference (RNAi) pathway, additional siRNAs were synthesized containing commercially available abasic alkyl spacers. Through the robust copper(I)-catalyzed Huisgen [3+2] cycloaddition, azide and alkyne nucleic acid monomers were joined through the heterocyclic linkage in nearly quantitative yields, producing the novel triazole-linked uracil-uracil (UtU) and cytosine-uracil (CtU) dimers. Results from cell-based assays indicate that triazole-modified siRNAs are capable of silencing the transiently-expressed reporter gene firefly luciferase and the endogenous gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in a dose-dependent manner. In addition, modifying the 3′- overhangs of siRNAs with the triazole backbone linkage, gave rise to increased nuclease resistance well beyond that of wild-type siRNA. Duplex RNAs containing abasic spacer linkages in the sense strand also maintained activity while targeting the luciferase reporter gene, indicating the capability to tune the efficacy of siRNA constructs by altering their thermodynamic profiles, in addition to providing evidence for an alternative RNAi mechanism. The studies describe herein, emphasize the compatibility of these novel backbone modifications with Watson-Crick interactions and with the RNA pathway.
Determining the impact of carrion decomposition on soil microbial activity levels and community composition.
(2013-12-01) Breton, Heloise; Forbes, Shari; Kirkwood, Andrea
The ubiquitous nature of microorganisms and their specificity to certain locations make them potentially useful for forensic investigators. Advances in microbial profiling techniques have made it possible to compare microbial community profiles obtained from evidence or crime scenes to individuals and vice versa. Profiling microbial communities associated with cadaver decomposition may provide useful information concerning post-mortem intervals and aid in the identification of clandestine graves. Four experiments using pigs as human decomposition analogues were performed over the course of 2011 and 2012 in southern Ontario to document changes in soil microbiology following decomposition. Studies were conducted in the spring and summer to document the effect of environmental conditions on the decomposition process and subsequent changes in gravesoil microbiology. Microbial activity was measured using a fluorescein diacetate assay as a preliminary indicator of changes within the soil microbial population. Both decreases and increases in microbial activity were observed throughout each decomposition experiment indicating that the microbial response to decomposition is complex. It is believed that environmental conditions and decomposition rates play a role in determining how taphonomic events affect soil microbial activity. Fatty acid methyl esters (FAME) profiling was used document community level changes throughout decomposition. Shifts in FAMEs profiles were brought on by the onset of active decay and persisted through to the dry remains stage. The fatty acids 3OH 12:0, 12:0, 16:0 and 18:0 were frequently found in higher amounts in gravesoils and may prove useful as markers of cadaver decomposition. Metagenomic profiles of soil microbial communities were obtained using Illumina® sequencing. Decomposition was associated with changes in microbial community composition. This allowed gravesoil samples to be differentiated from control samples for an extended period of time. Bacteria responsible for the shift in microbial profiles are those commonly associated with cadaver decomposition. Both sets of soil profiles indicated that weather had an effect on microbial community composition. Results highlight the need to document natural changes in microbial communities over seasons and years to establish normal microbial patterns to effectively use soil microbial profiles as post-mortem interval or clandestine grave indicators.
Elucidation of the lipid degradation process in soft tissue and fluid during decomposition, in the presence and absence of insects.
(2014-08-01) Comstock, Jenna; Forbes, Shari; LeBlanc, Helene
Decomposition has been extensively studied in the presence of insects, however the process in the absence of insects has been considerably less documented. In this study, the decomposition process was compared between domestic pig carcasses in the presence and the partial and complete absence of insects during three consecutive summers. Fluid was collected from carcasses, from which pH and conductivity were measured. The fluid was analyzed via attenuated total reflectance- infrared spectroscopy (ATR-IR) and gas chromatography-mass spectrometry (GC-MS) to examine the fatty acid degradation trends, in an attempt to identify potential biomarkers for estimating the post mortem interval (PMI). Tissue was also collected, from which pH was measured and fatty acids extracted and analyzed by GC-MS. All results were compared between the carcass groups to investigate the effect of insects on the decomposition process. Observations of the physical changes exhibited by the exclusion groups required new decomposition stages to be established to better characterize the processes. The fluid analyses indicated that insects influenced the trends observed from the pH and conductivity measurements. The effect of insects on the bands detected by spectroscopic analysis was unclear, however GC-MS results demonstrated that insects accelerated the rate of hydrogenation when they were present in large numbers; evidence of hydrogenation was absent in both exclusion groups. Tissue pH was also influenced by insect activity and significant differences were observed between carcass groups in the amount of individual fatty acids detected during the insect activity stages and following the advanced decay and dry stages. Characteristic fatty acids were not identified that would allow them to be used to estimate PMI. Further research investigating the complete lipid degradation process is required to establish fatty acids of interest which would aid in establishing accurate and objective methods of estimating PMI, to be used in criminal cases.
Forward genetic analysis of cellulose biosynthesis inhibitor resistance and wall hydrolysis sensitivity.
(2014-09-01) Shim, Isaac; Bonetta, Dario T.
The functional analysis of components involved in cellulose biosynthesis is central in understanding cell wall assembly and structure in plants. We conducted screens using the herbicides, isoxaben and flupoxam which inhibit cellulose biosynthesis in higher plants. Mutations resulting in a high degree of resistance to isoxaben (ixr) or flupoxam (fxr) were attributed to single amino acid substitutions in primary wall CESAs. Twelve novel resistance alleles were isolated and no cross-resistance was observed. Point mutations were mostly clustered around the C-terminal regions of CESA1 and CESA3, and CESA3 and CESA6 for fxr and ixr respectively. Resistance to isoxaben was also conferred by modification to the putative catalytic regions of CESA3. This resulted in cellulose deficient phenotypes characterized by reduced crystallinity and dwarfism. These results provide genetic evidence supporting CESA1-CESA3, and CESA3-CESA6 association with flupoxam and isoxaben respectively targeting and disrupting these interactions. The ixr and fxr mutants also exhibited enhanced saccharification under enzymatic degradation schemes which is consistent with the observed reduction in cellulose crystallinity. A second forward genetic screen was performed using mild acid hydrolysis to isolate mutants with enhanced saccharification. This screen identified sixty-three responsive to acid hydrolysis (rah) lines. Unconventional strategies to increase sugar yields from plant biomass where highlighted. These included starch hyper-accumulators such as starch excess 4 (sex4) loss-of-function mutants and the perturbation of polar auxin transport. Disruption of the serine/threonine kinase positive regulator of auxin efflux, PINOID (PID) was found to significantly enhance sugar release in Arabidopsis and similar effects were observed in the maize orthologue, BARREN INFLORESENCE 2 (BIF2). Furthermore, the application of N-1-naphthylphthalamic acid (NPA) in Arabidopsis, maize, Miscanthus and switchgrass phenocopied the enhanced wall saccharification effects of PID. This study attempted to elucidate some of the interactions of seemingly unrelated pathways in the context of wall biosynthesis and saccharification enhancement.
Dynamic probabilistic network protection in large-scale failure scenarios
(2015-01-01) Izaddoost, Alireza; Heydari, Shahram Shah
Large-scale failure resulting from natural disasters or intentional attacks is now considered a serious risk for communication network infrastructure. In these events, simultaneous damages in several links and nodes may cause substantial loss of information, which can be very costly for governments, subscribers and businesses. The impact of natural disasters generally is probabilistic in nature. Geographical characteristics and the distance of the components to the centre of the disaster may change the failure probability. Considering the probabilistic failure feature in natural disasters and the possible vast area coverage, we aim to develop a probabilistic dynamic model to protect data from failure and maintain undisrupted network services in large-scale failure scenarios. For this purpose, we develop a preventive protection model, which is able to estimate the potential destruction of all the network components in different locations. Using this information, the proposed model has a holistic view of the failure probabilities for the different paths to make a decision to reroute traffic from the endangered routes through the more reliable paths prior to the failure. As the proposed model protects data before failure, the size of damaged traffic will decrease and fewer connections need to be restored. The proposed preventive model is able to adjust rerouting decision parameters in a dynamic way by considering the disaster expansion and available network resources at each decision interval. Our findings show that the proposed preventive protection model significantly reduces the average number of disrupted connections and successfully decreases the required network restoration time. The performance of the proposed model has been examined in software defined networking (SDN), which is one of the emerging technologies in communication networks. We studied the performance of a SDN controller instructed with a considerable amount of data flow updates and the best method of applying preventive rerouting is indicated.
Analysis of resistance nodulation division efflux pumps in Acinetobacter baumannii
(2015-01-01) Fernando, Dinesh Malinda; Kumar, Ayush; Green-Johnson, Julia
Strains from Canadian hospitals were classified as A. baumannii, A. pitti, or A. osocomialis and the most commonly expressed resistance nodulation division (RND) efflux pump was adeFGH. A collection of A. baumannii isolates from the environment showed decreased susceptibility to at least three antibiotics and expression of three RND efflux pumps (adeFGH, adeABC, adeIJK). From the clinical collection two blood isolates, AB030 and AB031, were chosen to evaluate the outcomes of three virulence models. Using Caenorhabditis elegans and Galleria mellonella a statistically significant difference was shown in AB030 the extremely drug resistant strain. Investigation of the physiological role of adeFGH pump revealed its expression may be more important to cell metabolism and independent of factors controlling expression of the other pumps. This was further demonstrated through examination of local regulator knockout (adeL) in ATCC17978 showing expression levels of adeFGH pump increased only 2-fold. Expression in sub-lethal concentrations of chloramphenicol or florfenicol showed >5-fold induction of adeFGH expression as well as adeABC, independently of AdeL. These data show that the AdeFGH pump is likely regulated by AdeL, but more so by another unknown regulatory mechanism that responds to aberrant peptide formation and not DNA synthesis error or nitrosative stress. In addition strain specific differences likely also account for differences in phenotypic observations since nitrosative stress has improved tolerance and induced adeFGH expression in ATCC19606 and AB031. Finally analysis of efflux pumps in two triclosan resistant mutants, AB042 and AB043, revealed overexpression of AdeIJK and mutation in the adeIJK regulator, AdeN. Complementation repressed adeIJK expression levels and increased susceptibility to moxifloxacin and ciprofloxacin. The AB043 strain did not have any mutations in adeN, promoter region or RND operon. Osmotic stress tolerance revealed more C16 fatty acids and less C18 compared to the parent strain. The more triclosan resistant strain AB043, showed biofilm formation exclusively at 30°C. Twitching was observed and caused by mutation in the histone-like nucleoid structuring (HNS) protein but did not affect biofilm formation. Using RNA-seq and proteomic analysis putative targets of AdeIJK regulation were identified.
CORE: a framework for the automatic repair of concurrency bugs
(2015-01-01) Kelk, David; Bradbury, Jeremy; Green, Mark
Desktop computers now contain 2, 4 or even 8 processors. To benefit from them programs must be written to work in parallel. If writing good code is hard, writing good parallel code is much harder. Parallelization adds process communication and synchronization to the list of difficulties faced by programmers. It also adds new kinds of bugs not found in single-threaded code such as deadlocks and data races. In this thesis we develop the CORE (COncurrent REpair) framework. It automatically fixes deadlocks and data races in parallel Java programs. It uses a search-based software engineering approach to mutate and evolve the source code. In these mutants synchronization blocks are added, removed, expanded, shrunk or the synchronization variable is changed. Each potential fix is model checked or run through a thread noising tool that forces different thread interleavings to be explored. Efficiently fixing data races and deadlocks in parallel Java programs is realized by combining two techniques. First, different forms of static and dynamic analyses are brought together to constrain the search space. Second, a genetic algorithm without crossover was implemented that uses both noising and model checking to determine fitness. These techniques are unified in the CORE framework. Different kinds of analysis better constrain the search space of the problem. Intelligent use of noising, model checking and incremental model checking are combined efficiently into a modern framework that help to increase the overall quality of concurrent software. This thesis created three projects within the CORE framework, ARC-OPT, CORE-MC and CORE-IMC. First, static analysis from Chord and dynamic analysis from ConTest with fitness evaluation by thread noising from ConTest were combined in ARC-OPT. Second, JPF was integrated into the framework to analyze the source. Fitness was evaluated by JPF and ConTest. This version was called CORE-MC. Third, function header scanning for in-scope locks and incremental modelling support was added to CORE-MC to create CORE-IMC. Each project builds upon the previous and each was evaluated against a suite of test programs.
Effects of dietary fermentable material on innate and adaptive immune measures in male and female rats under resting and immunized conditions
(2015-02-01) Shastri, Padmaja; Green-Johnson, Julia
Sex-based differences in immune parameters are well recognized, and recent evidence suggests differences in microbiota composition between sexes, necessitating assessment of effects of dietary fermentable material (DFM) in both males and females. Effects of consumption of DFM of differing composition (Wheat Bran (WB), Oat Bran (OB), Resistant Starch (RS), Fructooligosaccharides (FOS)) on the immune system were compared under resting and immunized conditions between sexes. The gut microbiota composition and short chain fatty acid profiles differed between rats fed different DFM and also differed between sexes following FOS consumption. Immune parameters were analyzed for the effect of diet, differences between sexes or interactions (diet x sex), to detect the effect of DFM on male and female rats. The kinetics of primary (Day 0, 5, 10, 15) and secondary antibody responses (Day 21) were measured following immunization with a T cell-dependent antigen, Keyhole Limpet Hemocyanin (KLH). Under resting conditions, male rats had more FoxP3+ Treg cells in the mesenteric lymph node (MLN) and spleen than did females. Levels of the regulatory cytokine TGF-β1 also increased in the MLN in a DFM-dependent manner. In contrast, percentages of MLN and splenic CD68+ macrophages and levels of gut tissue IL-10 were higher in females than males. These results suggest immune regulation at the mucosal level is controlled in a differential manner between sexes and was affected by DFM intake only in males. At the systemic level, DFM intake delayed the primary anti-KLH IgG antibody response kinetics in male (control>>WB>OB>RS>FOS) and female (control> FOS>WB>RS>OB) rats. The secondary anti-KLH IgG response in control-fed males was 10-fold higher than in control-fed females. DFM intake in males significantly decreased anti-KLH IgG levels relative to control-fed males. Collectively, these findings demonstrate DFM consumption in males potentially induces systemic immune regulation leading to a delayed response to immune challenge, an effect that was not observed in females.
Towards measuring privacy
(2015-04-01) Kosa, Tracy Ann; El-Khatib, Khalil
The acceptable threshold for privacy is an individual choice, informed by culture, tradition and experience. That it is important, conversely, is self-evident. We use it to moderate personal information disclosure, how we choose to act and dress every day. However, the debate about privacy has struggled because of an incomplete scholarship that often halts with the question ‘what is privacy?’ Similarly, the affirmative statement ‘privacy is dead’ is often made without further explanation of what we have lost. This thesis provides a clarification of privacy by presenting a formal model and tool for precise discussion. It can be implemented, for example, in a mobile application or embedded on a website. The utility of the formal model is supported by survey research of professionals in the field and those with no particular related work experience. The formal model has given us several insights to how privacy behaves enabling progress towards an interdisciplinary understanding of terminology. In particular, it demonstrates and solves for the problem of transitivity in privacy because it can follow each personal information disclosure as it travels beyond the data subject through a network of people, processes and technologies. In addition to the formal model and observations about the behaviour of privacy, a contribution of this thesis is its review of computer science literature specifically for contributions to privacy research, an assessment of current privacy practitioner methods, a study of privacy impact assessment practices at Ontario hospitals, and a detailed exploration of the possibilities of future work.
Dynamic square patterns in two dimensional neural fields
(2015-07-29) Green, Kevin R.; van Veen, Lennaert
The goal of this thesis is to study the emergence of spatiotemporal waves in neural field models. Neural field models aim to describe the activity of populations of neurons at a mesoscopic scale, considering averaged neuronal states dependent on continuous space and time. Mathematically, they are composed of spatial and temporal integral operators on domains of anatomical interest. The cortex is modelled as a two dimensional sheet, and under physiological assumptions for the spatial extent of connectivities, it is shown when the principal transition from resting to active states will result in the formation of waves. This thesis starts with a derivation for the integral operators from a physiological viewpoint. The notion of a dynamical system is then introduced, and theory relevant to the spontaneous emergence of activity is discussed. The thesis progresses to applying the dynamical systems view to neural fields, leading to an understanding of the transitions from inactive resting states to space dependent temporal oscillations - waves. For tractable analysis, the active states are restricted to have square periodic symmetry.
On the potential of intent-based access control (IBAC) in preventing insider threats
(2015-11-01) Almehmadi, Abdulaziz; El-Khatib, Khalil
Existing access control mechanisms are based on the concepts of identity enrollment and recognition, and assume that recognized identity is synonymous with ethical actions. However, statistics over the years show that the most severe security breaches have been the results of trusted, authorized, and identified users who turned into malicious insiders. Therefore, demand exists for designing prevention mechanisms. A non-identity-based authentication measure that is based on the intent of the access request might serve that demand. In this thesis, we test the possibility of detecting intention of access using involuntary electroencephalogram (EEG) reactions to visual stimuli. This method takes advantage of the robustness of the Concealed Information Test to detect intentions. Next, we test the possibility of detecting motivation of access, as motivation level corresponds directly to the likelihood of intent execution level. Subsequently, we propose and design Intent-based Access Control (IBAC), a non-identity-based access control system that assesses the risk associated with the detected intentions and motivation levels. We then study the potential of IBAC in denying access to authorized individuals who have malicious plans to commit maleficent acts. Based on the access risk and the accepted threshold established by the asset owners, the system decides whether to grant or deny access requests. We assessed the intent detection component of the IBAC system using experiments on 30 participants and achieved accuracy of 100% using Nearest Neighbor and SVM classifiers. Further, we assessed the motivation detection component of the IBAC system. Results show different levels of motivation between hesitation-based vs. motivation-based intentions. Finally, the potential of IBAC in preventing insider threats by calculating the risk of access using intentions and motivation levels as per the experiments shows access risk that is different between unmotivated and motivated groups. These results demonstrate the potential of IBAC in detecting and preventing malicious insiders.
A framework for privacy-preserving data sharing in smart grid
(2016-01-01) Alharbi, Khalid; Lin, Xiaodong
While smart grid introduces a lot of enhancements to the traditional power grid and improves managing and controlling consumers demands, it also introduces security and privacy issues. Therefore, failure to address them will hinder the flourish of smart grid. In this thesis, we propose a novel framework for privacy-preserving data sharing in smart grid using a combination of homomorphic encryption and proxy re-encryption. The proposed framework allows distributed energy resources to be able to analyze the consumers data while preserving the consumers privacy. To the best of our knowledge, the proposed framework is first attempt to consider an important problem concerning data sharing in smart grid. Furthermore, in order to effectively collect consumer (or household) electricity consumption data, we also propose an efficient lightweight privacy- preserving data aggregation scheme, called ELPDA, for smart grid. The proposed scheme aims at resolving the power consumption data security and residential consumer privacy by employing one-time masking technique to protect consumers privacy while achieving lightweight data aggregation. Moreover, we study the situation in which gateways aggregating consumers’ data become malicious. Then, we propose a security-enhanced data aggregation scheme for smart grid communications from a homomorphic cryptosystem, trapdoor hash functions and homomorphic authenticators. The distinctive feature of our scheme achieves data confidentiality and integrity against the malicious aggregator (e.g. gateway), meaning that the aggregator is not able to learn the privacy of users or corrupt the power consumption reports during the aggregation process. In addition to the above schemes for smart grid upnlink communications, we propose an efficient and privacy-preserving scheme in order to protect smart grid in downlink communications. Specifically, we propose an efficient identity based signcryption, called EIBSC, providing privacy preservation in downlink communication for smart grids. The proposed scheme is characterized by employing the concealing destination technique on the tree-based network to protect consumer privacy in downlink communication. Furthermore, the proposed scheme employs identity based signcryption to efficiently achieve downlink message source authentication, data integrity and confidentiality. Additionally, compared to other identity-based signcryption schemes, the proposed scheme is more efficient in regards to computational overhead and ciphertext size. Furthermore, security analysis demonstrates that the proposed scheme is resilient against various security threats to smart grids.
The modification of fuel cell-based breath alcohol sensor materials to improve water retention of sensing performance
(2016-03-01) Allan, Jesse; Easton, E. Bradley
Fuel cell based breath alcohol sensors (BrASs) are one of the most important tools used by law enforcement today. While these devices are used globally, they all suffer from a common deficiency: reliance on water. The ability of the fuel cell sensor to manage water content is one of the greatest fundamental challenges facing this technology today. A next-generation fuel cell was designed specifically for sensor testing along with a test station that allowed for rapid response and sensor characteristics of a given material. The in-house design was validated against a commercial cell to provide feedback on how materials in the in-house cell would behave in a commercial designed unit. The results showed that our cell with a commercial membrane electrode assembly (MEA) behaved identically to a commercial cell with the same MEA. Membranes were for their role in senor performance. Membranes for power generation, such as Nafion, were investigated and while they showed good performance in high humidity, performance suffered in low humidity. This is due to the thin characteristics of the material. Poly-vinyl chloride (PVC) membranes showed improved performance over Nafion, while composites of PVC and sulfonated silica showed performance that matched that of the commercial PVC, whilst using significantly less water. Finally, the catalyst layer and gas diffusion layer (GDL) were investigated. For the catalyst layer, platinum black and 20% platinum supported on carbon achieved similar results. The choice of catalyst was less of an issue than the choice of GDL. It was found that using carbon fiber paper GDLs lead to greater retention of water in the MEA compared to carbon cloth GDLs due to the lower air permeability. This came at a cost however in that with a lower air permeability, less ethanol vapour would reach the catalytic sites, reducing sensing performance.
Alloy catalysts for fuel cell-based alcohol sensors
(2016-05-01) Zamanzad Ghavidel, Mohammadreza; Easton, Brad
Direct ethanol fuel cells (DEFCs) are attractive from both economic and environmental standpoints for generating renewable energy and powering vehicles and portable electronic devices. The cost and performance of the DEFCs are mainly controlled by the Pt-base catalysts used at each electrode. In addition to energy conversion, DEFC technology is commonly employed in the fuel-cell based breath alcohol sensors (BrAS). BrAS is a device commonly used to measure blood alcohol concentration (BAC) and enforce drinking and driving laws. The BrAS is non-invasive and has a fast respond time. However, one of the most important drawback of the commercially available BrAS is the very high loading of Pt employed. One well-known and cost effective method to reduce the Pt loading is developing Pt-alloy catalysts. Recent studies have shown that Pt-transition metal alloy catalysts enhanced the electroactivity while decreasing the required loadings of the Pt catalysts. In this thesis, carbon supported Pt-Mn and Pt-Cu electrocatalysts were synthesized by different methods and the effects of heat treatment and structural modification on the ethanol oxidation reaction (EOR) activity, oxygen reduction reaction (ORR) activity and durability of these samples were thoroughly studied. Finally, the selected Pt-Mn and Pt-Cu samples with the highest EOR activity were examined in a prototype BrAS system and compared to the Pt/C and Pt3Sn/C commercial electrocatalysts. Studies on the Pt-Mn catalysts produced with and without additives indicate that adding trisodium citrate (SC) to the impregnation solution improved the particle dispersion, decreased particle sizes and reduced the time required for heat treatment. Further studies show that the optimum weight ratio of SC to the metal loading in the impregnation solution was 2:1 and optimum results achieved at pH lower than 4. In addition, powder X-ray diffraction (XRD) analyses indicate that the optimum heat treatment temperature was 700°C where a uniform ordered PtMn intermetallic phase was formed. Although the electrochemical active surface area (ECSA) decreased due to the heat treatment, the EOR activity of Pt-Mn samples was improved. Moreover, it was shown that the heat-treated samples prepared in the presence of SC showed superior the EOR activity compared to the samples made without SC. The Pt-Cu/C alloys were produced by three different methods: impregnation, impregnation in the presence of sodium citrate and microwave assisted polyol methods. These studies showed that the polyol method was the optimum method to produce the Pt-Cu alloy. The XRD analysis indicates that the heat treatment at 700 °C developed catalysts rich in the PtCu and PtCu3 ordered phases. The highest EOR activity was measured for the Pt-Cu/C-POL (sample made by the polyol method) and heat treated at 700°C for 1h. Comparing the EOR activity of the Pt-Cu and Pt-Mn samples also demonstrates that the heat treated Pt-Cu/C-POL sample showed higher EOR activity compared to the Pt-Mn samples. These results indicate that the benefits of thermally treating alloy nanoparticles could outweigh any activity losses that may occur due to the particle size growth and the ECSA loss. Besides, accelerated stress tests (ASTs) illustrate that the heat treatment improved the durability of the Pt-Mn and Pt-Cu samples. The durability and EOR activity of the heat treated Pt-Mn and Pt-Cu samples was similar or better than commercial samples. On the other hand, the ORR activity of Pt-Mn and Pt-Cu after the heat treatment was slightly lower than the commercial samples but the ORR activity loss can be compensated by the economic benefits from using the lower Pt loading. Finally, studying the alcohol sensing characteristic of different samples shows that the heat treated Pt-Mn and Pt-Cu catalysts could be used for the ethanol sensing. Additionally, among the different commercial samples tested for ethanol sensing, Pt-Sn/C showed the highest sensitivity but with slightly higher standard deviation. Further studies on the Pt- Cu/C and Pt-Mn/C samples indicate that the heat treatment improved the sensitivity of these samples and the highest normalized sensitivity among all the samples belonged to the Pt-Cu/C-POL (sample produced by polyol method) and heat treated at 700°C. It can be concluded that the heat treated Pt-Mn and Pt-Cu samples could be used as an alternative to replace Pt black in commercial sensors which would dramatically decrease the Pt loading. This could reduce the price and increase the sensitivity of commercial alcohol sensors.
Cognitive function during exertional heat stress assessed using traditional and serious game technology
(2016-06-01) Williams-Bell, F. Michael; Murphy, Bernadette; McLellan, Tom
Firefighting is a physically demanding occupation requiring intermittent bouts of work resulting in increased levels of cardiovascular and thermal strain, while making decisions requiring higher order cognitive abilities e.g. working memory, sustained attention, reaction time, spatial awareness, and information processing. These activities can take place in dangerous conditions with elevated temperatures imposing external stressors on physiological and cognitive function. Previous research has examined the impact of heat stress on cognitive function in general, but the specific influence on firefighters wearing personal protective equipment (PPE) and self-contained breathing apparatus (SCBA) is not well understood. Specific domains of cognitive function can be assessed using computer-based neuropsychological testing batteries, such as the Cambridge Neuropsychological Automated Testing Battery (CANTAB). The CANTAB automatically records the response measures for each test and provides consistent feedback in between trials. Although the CANTAB is well established the cognitive domains it tests may not adequately capture the complexity of the specific decision making required of firefighters while on-duty. The use of serious game technology provides a possible solution to develop a more ecologically valid assessment tool capable of evaluating the specific decision making tasks required of firefighters at an emergency scenario. Thus, the current thesis aimed to evaluate the effects of exercise-induced heat stress on cognitive function in firefighters using the CANTAB testing battery and a recently developed serious game simulating the decision making tasks required of firefighters in a two-storey residential fire while walking on a treadmill. Additionally, the reliability of repeated CANTAB administrations during treadmill walking was measured and found to have reasonable overall reliability. Decrements in cognitive function (working memory and executive function were observed at a core temperature of 38.5°C and restored following an active cooling recovery protocol. However, when decision making was evaluated using the serious game scenario, task specific performance deficits were not seen during treadmill walking but impairment in memory recall was found following the active cooling recovery protocol. These findings provide fire service personnel with information regarding the cognitive implications of heat stress and the potential use of serious games to evaluate and train cognitive function during exposure to environmental stressors.
A dynamic visual analytics framework for complex temporal environments
(2016-08-01) Kamaleswaran, Rishikesan; McGregor, Carolyn
Introduction: Data streams are produced by sensors that sample an external system at a periodic interval. As the cost of developing sensors continues to fall, an increasing number of data stream acquisition systems have been deployed to take advantage of the volume and velocity of data streams. An overabundance of information in complex environments have been attributed to information overload, a state of exposure to overwhelming and excessive information. The use of visual analytics provides leverage over potential information overload challenges. Apart from automated online analysis, interactive visual tools provide significant leverage for human-driven trend analysis and pattern recognition. To facilitate analysis and knowledge discovery in the space of multidimensional big data, research is warranted for an online visual analytic framework that supports human-driven exploration and consumption of complex data streams. Method: A novel framework was developed called the temporal Tri-event parameter based Dynamic Visual Analytics (TDVA). The TDVA framework was instantiated in two case studies, namely, a case study involving a hypothesis generation scenario, and a second case study involving a cohort-based hypothesis testing scenario. Two evaluations were conducted for each case study involving expert participants. This framework is demonstrated in a neonatal intensive care unit case study. The hypothesis generation phase of the pipeline is conducted through a multidimensional and in-depth one subject study using PhysioEx, a novel visual analytic tool for physiologic data stream analysis. The cohort-based hypothesis testing component of the analytic pipeline is validated through CoRAD, a visual analytic tool for performing case-controlled studies. Results: The results of both evaluations show improved task performance, and subjective satisfaction with the use of PhysioEx and CoRAD. Results from the evaluation of PhysioEx reveals insight about current limitations for supporting single subject studies in complex environments, and areas for future research in that space. Results from CoRAD also support the need for additional research to explore complex multi-dimensional patterns across multiple observations. From an information systems approach, the efficacy and feasibility of the TDVA framework is demonstrated by the instantiation and evaluation of PhysioEx and CoRAD. Conclusion: This research, introduces the TDVA framework and provides results to validate the deployment of online dynamic visual analytics in complex environments. The TDVA framework was instantiated in two case studies derived from an environment where dynamic and complex data streams were available. The first instantiation enabled the end-user to rapidly extract information from complex data streams to conduct in-depth analysis. The second allowed the end-user to test emerging patterns across multiple observations. To both ends, this thesis provides knowledge that can be used to improve the visual analytic pipeline in dynamic and complex environments.
Influence of dietary interventions on the immune system: an investigation of the impact of omega-3 fatty acids, dietary fermentable materials and high energy diets
(2016-12-01) Clarke, Sandra T.; Green-Johnson, Julia
Dietary interventions vary in ability to influence immune activity. Separate investigations were conducted to determine the immune impact of omega-3 fatty acids, dietary fermentable materials (DFM) and high energy (HE) diets. Omega-3 fatty acid impact on bovine immunity was examined by comparing effects of fish oil and microalgae dietary supplements in the context of different feed management systems (pasture versus confinement). Cattle consuming microalgae had higher antibody production and cattle in the pasture system had higher anti-keyhole limpet hemocyanin (KLH) and total antibody responses on all diets. Overall, effects of omega-3 supplements on bovine immunity were influenced by feed management system with heightened impact on antibody production observed with a pasture system. A double-blind placebo-controlled, randomized crossover clinical trial involving 30 healthy adults was conducted to examine impacts of β2-1 fructans on immunity. Subjects consumed an oligofructose-enriched inulin or maltodextrin supplement for a 28-day period (5 g, 3× daily with meals). β2-1 fructan supplementation significantly increased serum endotoxin and IL-4 concentrations, circulating percentages of CD282+/TLR2+ myeloid Dendritic cells (mDC) and ex vivo responsiveness to a Toll-like receptor 2 (TLR2) agonist, while serum IL-10 concentrations decreased. A rat trial was designed to examine effects of a HE diet supplemented with varied DFM (7% wheat bran, oat bran, resistant starch type II, or fructooligosaccharide (FOS)) on obesity-associated biomarkers in male Sprague-Dawley rats. After 2 weeks of HE diet consumption, rats were segregated into obese-prone and obese-resistant phenotypes and shifted to DFM-supplemented HE diets for an additional 11-12 weeks. Obese-prone rats had higher serum insulin and leptin concentrations than obese-resistant rats. FOS-fed rats had decreased splenic percentages of B cells, natural killer cells, T lymphocytes, memory T cells and cytotoxic T cells compared to rats on the control diet. High-energy diets had differential impacts on systemic and mucosal cytokines in both phenotypes; however, DFM had relatively less influence on cytokine and adipokine profiles associated with diet-induced obesity. Taken together, dietary interventions are capable of subtly influencing varied immune outcomes in animal models and in human subjects, however the interpretation of these dietary influences may be context-dependent.
Synthesis and characterization of Pt/TiO2/C composite catalysts for fuel cells prepared using a glucose modifier
(2017-03-01) Odetola, Christopher; Easton, Brad; Trevani, Liliana
Catalysts in the electrodes of polymer exchange membrane fuel cells (PEMFCs) serve a critical function in reactions which can be used to generate electrical energy from chemical fuels. Pt nanoparticles are commonly dispersed on a conductive support and used as electrode materials in these devices because of their exceptional catalytic activity and electrochemical active surface area. The performance and stability of these electrodes strongly depend on the characteristics of the support. Catalysts supported on high surface area carbon black are widely used in low-temperature fuel cells. In PEMFCs, these catalyst materials can be exposed to high potential and low pH values, resulting in irreversible loss of activity that will limit the useful lifetime of the cell, ultimately leading to its failure. Pt is a noble metal which has good intrinsic stability, but carbon is not thermodynamically stable resulting in the corrosion of the catalyst support under these conditions. The design of more resilient platinum catalyst supports to carry out the successful reaction in a fuel cell’s catalyst layer is required to extend the lifetime of PEMFCs degradation. In this thesis, two approaches were used to synthesize robust catalyst support materials for fuel cell applications. In the first case, carbon surfaces were functionalised to enhance their interactions with the catalyst and secondly, stable metal oxide was combined with modified carbon substrates, to maximise contacts within the composite electrocatalysts and to prevent carbon corrosion of a single phase carbon support catalyst. TiO2 NPs, were first chemically bonded to the surfaces of Vulcan carbon to help anchor the Pt catalyst nanoparticles through strong metal-support interactions. Validation of a dual phase catalyst support is an important goal of this research. Each material phase offers a unique advantage that can only be recognized by the preparation of a composite electrocatalyst. Pristine Vulcan (PV) was functionalised with glucose hydroxyl functional groups that react with the base titanium metal alkoxide in a sol-gel reaction and then calcined to form a more chemically crystalline surface. This is followed by impregnation reduction process to deposit the nanostructured Pt catalyst. Material characterization data of synthesized materials were used to correlate the effects of support structure and composition on resilient performance. Advantages from the TiO2/C supports toward performance and durability were contrasted against a set of control samples and demonstrated ex situ. The prepared composite catalysts showed substantial enhancements toward oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) as well as improved stability of the Pt-TiO2 heterogeneous interface formed between catalyst and support. The enhanced performance and durability of these composite catalysts is improved by applying the science of materials and interfaces to the synthesis of composite supports, thus serving as an example for further progress and optimization. Irradiation of these composite catalysts with UV-visible light also showed ~ 171 % photo enhanced activity for MOR, which clearly demonstrates a synergistic effect between the photo- and electrocatalysts. The comparison between the prepared catalysts indicates that there is an appropriate ratio of carbon and TiO2 to obtain the best performance of these photoelectroactive materials. These results demonstrate that methanol oxidation is achieved by electro- and photoelectrocatalysis using a simple and affordable method. This procedure can be conveniently exploited to enhance the response of direct methanol fuel cell electrodes.
Nanostructured materials for photovoltaics and microwave electronics: methods and applications
(2017-04-01) Quaranta, Simone; Gaspari, Franco
Nanoscale particles and thin layers are today used for a variety of applications to make industrial products lighter, stronger or more conductive. This study investigates synthesis, characterization and application of nanostructured materials for “low-cost” photovoltaics and high frequency (microwaves) analog electronics. Indeed, the two areas investigated demonstrate the enormous potential for diverse applications of nanostructured materials. The initial research stage focused on the optimization of titanium dioxide morphology for Dye Sensitized Solar Cells (DSSCs) applications. Four different combined sol-gel/solvothermal synthetic approaches were adopted and six different anatase phase mesoporous titanias were prepared and tested as photoanodes in DSSCs. Superior light scattering properties, stemming from their sub-micrometric mesoporous structure, were proved for TiO2 beads synthesized by using the exadecylamine method. An energy conversion efficiency ŋ = 7.0 % was achieved. The second stage of the research aimed at further DSSC performances’ improvements by introducing trivalent rare earth dopants (Pr, Nd, Sm, Gd, Er and Yb) into the “standard” TiO2 beads. Rare earth ions’ dimension was found to affect TiO2 average crystallites size through nucleation control and ultimately electron recombination lifetime through TiO2 natural oxygen defectivity and electron-impurity scattering control. While the largest (i.e. the lightest) ions of the lanthanide series (Pr3+ and Nd3+) suppress DSSCs performances, cations heavier than Sm 3+ produce an energy conversion increase compared to pure anatase. The best performances were obtained for a rare earth dopants concentration of 0.2 % erbium atoms (ŋ = 8.7 %, 20% efficiency improvement compared to un-doped TiO2). The third research step investigated materials capable of modulating TiO2 optoelectronic and interfacial properties at once, e.g. chirality separated Single Walled Carbon Nanotubes (SWCNTs). Chirality selection allowed for tuning the energy barrier at the TiO2/SWCNTs/FTO interface, electronic conductivity enhancement and reduced SWCNTs-Ruthenium dye competition for light absorption resulting in a 81 % ŋ improvement compared to mixed chirality cells. Besides, certain SWCNTs chiralities were ruled out as useful materials for DSSCs applications. By taking advantages of high porosity TiO2 beads, titania affinity for phosphate based moieties and group 8 metals coordination behavior toward pyridyl ligands (like Ruthenium in the N-719 dye used for DSSCs), a high sensitivity (0.3 ppm by naked eye), reusable, Fe2+ colorimetric sensor was developed. A terpyridine based ligand, L (2,2’:6’,2”-terpyridin-4’-phosphonic acid), was used as iron sensitive molecule, whereas screen printed TiO2 beads as scaffold material. Furthermore, L-functionalized Indium Tin Oxide (ITO) thick films were proved to be reliable electrochromic materials and possible candidates for trivalent iron detection predicated on microwaves antennas’ resonant frequency shift. Finally, Multiwalled Carbon Nanotubes (MWCNTs) and Graphene films for resonant frequency tuning of copper etched printed circuit boards antennas were produced and electrically characterized over a large range of operating frequencies.

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