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Modelling and Control of Airship with Slung Payload
No full textThis study explores the modelling and control of a multibody system comprising an airship, gondola, and a slung payload. Lighter-than-air vehicles undergo inertial forces that are often neglected in heavier-than-air vehicles. These inertial forces are modelled using added mass and added inertia and there can be significant discrepancies between the values obtained empirically and those of the actual vehicle. The dynamics of the multibody system were first modelled using the Udwadia-Kalaba method. The resulting equation of motion was used to identify the added mass, added inertia, and inertia of the airship through system identification procedure. The proposed system identification method utilizes semidefinite programming with equality and inequality constraints to find any unknown parameters in the mass matrix of the multibody system. Three experiments were carried out to perform the system identification and validate the dynamic model. A comparison of reconstructed trajectories before and after applying system identification shows that the identified mass matrix produces more accurate results with 35% lower root mean squared error of position when compared with the trajectories simulated before carrying out system identification. Aerodynamic coefficients, including lift and drag coefficients, were calculated for a full-scale airship prototype using the Reynold's averaged Navier-Stokes with Spalart-Allmaras turbulence model.
Using the nonlinear dynamic model of the multibody system, two fuzzy logic controllers were developed to attenuate the payload's oscillations and maintain the payload at a desired position. Two more fuzzy logic controllers were designed to navigate the airship-gondola-slung-payload system in the longitudinal plane to a target location. An additional fuzzy logic controller was developed to deliver the payload by means of controlling the altitude. The proposed control method addresses a gap in the literature, which lacks experimental studies on airships with slung payloads using fuzzy logic control. The controller was evaluated under wind disturbance through simulations and in outdoor experiments. Despite the adverse weather conditions, the navigation fuzzy logic controller operated as intended, effectively responding to inputs and attempting to correct errors while adhering to the upper and lower bounds of the thrusters
Engaging, recruiting, and retaining pregnant people from marginalized communities in environmental health cohort studies: a scoping review
No full textAbstract Objectives To identify barriers to and strategies for improving the representation of pregnant people from marginalized communities in pregnancy cohort studies that measure environmental chemicals. Methods Guided by the Arksey O’Malley and Levac Frameworks, we conducted a scoping review of peer-reviewed literature published between 2000 and 2022. Included studies discussed barriers and/or strategies related to engaging, recruiting, and retaining pregnant participants or participants of reproductive age from marginalized communities into environmental health research. Results Twenty-nine peer-reviewed articles were included in the review. Overall, 31% (9/29) of the studies reported on engagement, recruitment, and retention of participants from racialized communities, 10% (3/29) reported on involvement of participants identifying as Indigenous, and 10% (3/29) of studies reported on participants living in households or areas of low socioeconomic status. We identified four key barriers: participant burden, social inequities, lack of trust, and lack of cultural relevance. We reported identified strategies to mitigate these barriers. Conclusion Although there is limited coverage in the literature on strategies to effectively engage people from marginalized communities in environmental health pregnancy cohort studies, our findings suggest that applying a health equity and social justice lens to research may help address barriers that exist at the individual, interpersonal, community, institutional, and policy levels. Findings from this review may have important implications for planning future pregnancy cohort studies and ensuring that communities who are disproportionately affected by environmental chemical exposures may be better represented in research and considered in policy decisions
Guidelines for the content of statistical analysis plans in clinical trials: protocol for an extension to cluster randomized trials
No full textAbstract Background Guidance exists to inform the content of statistical analysis plans in clinical trials. Though not explicitly stated, this guidance is generally focused on clinical trials in which the randomization units are individual patients and not groups of patients. There are critical considerations for the analysis of cluster randomized trials, such as accounting for clustering, the risk of imbalances between the arms due to post-randomization recruitment, and the need to use small sample corrections when the number of clusters is small. Methods This paper outlines the protocol for the development of a set of reporting guidelines for the content of statistical analysis plans for cluster randomized trials (including variations such as the stepped wedge cluster randomized trial and other cluster cross-over designs) by extending the minimum reporting analysis requirements as previously defined for individually randomized trials to cluster randomized trials. The guideline will be developed using a consensus-based approach, modifying existing reporting items from the guideline for individually randomized trials and extending to include new items. Discussion The guideline will be developed so it can be used independently of the guideline for individually randomized designs. The consensus guidelines will be published in an open-access journal, including key guidance as well as exploration and elaboration
Authenticity in Influencer Marketing, Building Trust and Addressing Distrust: A Case Study of Sadaf Beauty
No full textSocial media influencers are subject to an important - and constraining - paradox. On the one hand, they attract followers by presenting themselves as authentic while, on the other hand, they simultaneously use their popularity to promote products, as an act perceived by some followers as "inauthentic". Managing this contradiction and creating trust are crucial in their success and affects the number of people they reach. Successful influencer marketers negotiate this contradiction to inspire their followers' trust. However, while relying on these success factors, sometimes influencers lose control and cannot manage this contradiction which leads to followers feeling betrayed and losing trust. In this research, qualitative method based on case study of a successful Iranian Influencer, Sadaf Masaeli (Sadaf Beauty), assisted to observe how influencers lose control in managing different success factors and to analyze which factors make influencers to lose followers' trust. Sadaf was chosen as the second most influential beauty influencer of 2019 and the most influential luxury cosmetics influencer of 2019 in the world by Forbes (Claudel, 2019). She gained millions of followers from 2019 to 2022. However, in 2022 she lost thousands of followers. This research argues that incautious authenticity (indiscretion) and not setting concrete boundaries, especially in regard to sensitive topics, can cause distrust in followers
Simulating Action Potential Initiation and Propagation in Physically Detailed Damaged and Healthy Neurons
No full textThis thesis presents single-compartment and multi-compartmental neuron models. We simulated injury-induced pathological spiking patterns, as well as heterogeneous ion channel distributions in the axon initial segment (AIS) and their impact on backpropagation. In neurons, voltage-gated sodium and potassium ion channels (ᵥs and ᵥs, respectively) regulate ionic currents across the cell membrane in the production of action potentials (APs). As such, channel dynamics feature throughout this thesis. The starting point was the Coupled left-shift () model of cellular damage, wherein the gating properties of ᵥs are thrown "out of tune" by injury (left-shift, ), such that the subpopulation of affected channels () no longer responds correctly to homeostatic membrane potentials. We simulated a single-compartment neuron with -type damage and systematically mapped out its excitability regimes in the - plane. Next, we added temperature sensitivity to the ᵥ and ᵥ gating kinetics and maximal conductances, the Nernst potentials, and the Na⁺/K⁺ pump. We compared the neuron's ability to cope with damage when temperature effects were added one by one, to the case where all effects act together as they would in nature. The former "knock-in/knock-out" simulations revealed the importance of (i.e. model sensitivity to) each temperature-driven change in the ionic currents that govern excitability. Our multicompartmental pyramidal cell models indicate that the pattern of ion channels in the AIS affects feedback sent to synapses in the soma and dendrites. Inserting a set of hypothetical ᵥ distributions into the AIS, we found that the impact of ᵥ subtypes on the neuron's backpropagation threshold depends on the mode of stimulation (orthodromic or antidromic). Both modes are used by experimentalists, and our results should inform comparative studies as well as the design of neural prosthetics, as the AIS is a logical target for multielectrode arrays used in brain-computer interfaces. Coupled left-shift in the AIS produced axonal hypersensitivity, decoupled the somatic backpropagation threshold from the AP threshold, and modified backpropagation in a manner resembling polarity reversal of the AIS sodium channel pattern. Below the ectopic threshold, may interfere with homeostatic intracellular signalling and learning via the putative role of spike-timing-dependent plasticity in the dendrites
Chronic Toxicity of Lithium to the Water Flea Daphnia pulex and Fingernail Clam Pisidium dubium
No full textLithium (Li), a metal used in batteries and pharmaceuticals, is increasingly in demand as part of a greener economy. However, its extraction, use, and disposal may elevate environmental concentrations, raising concerns about aquatic ecosystems. This study assessed Li chronic toxicity and bioaccumulation in two freshwater invertebrates: Pisidium dubium (28-day exposure) and Daphnia pulex (21-day exposure). Organisms were exposed to environmentally relevant Li concentrations (0.05-10 mg/L for P. dubium; 0.5-3 mg/L for D. pulex). Results showed reduced survival (EC₅₀ = 1.37 mg/L) and impaired burrowing behavior (EC₅₀ = 1.59 mg/L) in P. dubium, with tissue analysis suggesting internal Li regulation. In D. pulex, reproduction (EC₅₀ = 1.77 mg/L) and growth (EC₅₀ = 3.01 mg/L) were significantly affected. While natural Li levels in surface waters are usually below these thresholds, elevated concentrations near mining and urban areas could harm aquatic invertebrates, highlighting the need for improved waste management strategies
Versatile Application of Iron Oxide Nanoparticles in Environmental Challenges: From Trace Sulfur Dioxide Adsorption to Waste Glycerol Valorisation
No full textNanomaterials and nanoparticles are now largely investigated for various applications due to their unique properties. Iron oxide nanoparticles are increasingly popular due to their non- toxicity, affordability and versatility as well as iron abundance. Their potential magnetism is a valuable property in the field of heterogeneous catalysis as it allows for an easy recovery of the catalyst. In this project, iron oxide nanoparticles were designed and synthesized using green approaches as well as more traditional coprecipitation approaches and investigated for environmental applications. The nanoparticles were used for the adsorption of trace concentration of SO2 and revalorisation of waste glycerol produced from the biodiesel production.
Low concentrations of SO2 are present in industrial gaseous effluents even after flue gas desulfurization. Trace SO2 capture is challenging, and even low concentrations (ppm levels) of SO2 can deactivate or poison catalysts used in processes aiming to revalorise the desulfurized gas. In this work, cellulose-based adsorbents modified with iron oxide nanoparticles are proposed as a solution to remove trace SO2. Cellulose is selected as it is sustainable, abundant, and innocuous, has a high surface area and contains hydroxyl groups on its surface which facilitate nanoparticles deposition. The iron oxide nanoparticles were obtained from a plant-based reduction process using green tea extract. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to assess the nanoparticle deposition and characterize the adsorbents. It was observed that the deposition process was more effective on microcrystalline cellulose than on nanocrystalline cellulose. The amount of reducing agent used had an impact on the chemical speciation of the iron oxide deposited on the cellulose and the degree of particle agglomeration.
Breakthrough capture experiments were conducted at room temperature using an inlet stream containing 25 ppm SO2 in argon. The impact on the adsorption capacity of the adsorbents synthesis parameters, such as the type of cellulose used, the deposition time, the iron loading on the adsorbent and the amount of reducing agent used for the deposition, were evaluated. Microcrystalline cellulose modified with iron oxide nanoparticles showed a significantly higher affinity for the SO2 than modified nanocrystalline cellulose, or both types of pristine cellulose.
The optimal iron oxide nanoparticle deposition time on the microcrystalline cellulose was observed to be 72 hours. The adsorption capacity was directly related to the iron content in the adsorbent and increased from 0.017 mgSO2/gadsorbent to 0.45 mgSO2/gadsorbent when the iron content was increased from 0.16 wt% to 2.71 wt%. The chemical speciation of the iron also had a significant impact on the adsorption with Fe3O4 nanoparticles performing the best. Future work will focus on including CO2, O2 and H2O in the inlet gaseous stream and performing other modification to cellulose to increase its adsorption.
Otherwise, biodiesel production has increased significantly over recent years to provide an alternative fuel. 10% w/w of glycerol is produced as a byproduct from the biodiesel production, and this has led to a saturation of the glycerol market, making it a waste material. Glycerol can however be valorized into platform chemicals through various reactions such as oxidation. We therefore propose a Fe3O4-based catalyst to perform this oxidation in both a Fenton-like system and a photocatalytic system to produce dihydroxyacetone which has a higher economical value. The Fe3O4 nanoparticles were obtained from two different methods: coprecipitation and steel revalorisation, and further compared to FeCl3 catalytic system. Both were doped with Ag nanoparticles using NaBH4 or green tea extract as reducing agents. The catalysts were characterized by dynamic light scattering (DLS), XRD, TEM and their band gap was measured using diffuse reflectance spectroscopy (DRS) and the Tauc method. Both types of Fe3O4 showed a nearly identical size distribution, but more nanoparticle agglomeration was observed on the revalorised Fe3O4. The Ag doping was confirmed by XRD and the bandgaps of all the doped catalysts were smaller than their non-doped counterparts.
The catalysts were compared to a traditional Fenton oxidation of glycerol and the reaction was monitored by 1H NMR. Parameters such as the hydrogen peroxide to glycerol ratio, the doping, the type of Fe3O4 and the mass of catalyst were investigated. All the Fe3O4 based catalysts showed a higher dihydroxyacetone selectivity than the FeCl3, but a lower conversion. Dihydroxyacetone selectivity as high as 94% was measured when using Fe3O4 nanoparticles doped with Ag by using NaBH4. However, the conversions remained between 6% and 19% for the Fe3O4 catalysts. In the photocatalytic system, the intensity of the light, the pH and the temperature were investigated. Future work will focus on improving the conversion in the Fenton-like system, transitioning to only revalorisation Fe3O4 and performing more photocatalytic studie
Sexual and Romantic Relationships Among People Experiencing Homelessness
No full textIn Canada, individuals experiencing homelessness face ongoing marginalization, with many of their essential needs frequently ignored. This issue is exacerbated by structural challenges within homelessness services, including the design of single-sex shelters and a lack of private spaces, which impedes the initiation and sustainment of sexual or romantic partnerships. Academic studies have predominantly concentrated on addressing mental health, addiction, housing, and financial needs while providing minimal attention to the sexual and romantic relationship needs of the homeless population. Moreover, while much of the existing research categorizes sexual behaviour primarily as a risk factor for poor sexual health outcomes among people experiencing homelessness, there's a dearth of studies examining how romantic partnerships could offer support and contribute to stability. For this dissertation, I conducted three studies to explore the effects of sexual and romantic relationships on the lives and overall well-being of individuals experiencing homelessness and to assess how these relationships might influence their housing stability.
Study 1 was a scoping review that aimed to (a) characterize the nature of research that has examined sexual and romantic relationships among people who are homeless and (b) identify and synthesize the findings of studies that examined romantic and sexual relationships among people experiencing homelessness. We found that the majority of existing studies predominantly focused on the potential risks linked with sexual activity, including victimization and the risk of sexually transmitted infections. Among the studies that substantially investigated consensual sexual or romantic relationships, we identified prevalent themes, including love, romance, and emotional support; the transactional nature of partner relationships; obstacles to forming partner relationships; and aspects of casual sex and pleasure.
Study 2 was a scoping review that examined the consent and sexual agency implications of survival sex. Survival sex is the exchange of sex for material goods required for survival (i.e., shelter, food, drugs) and, in Western contexts, almost exclusively occurs among people experiencing homelessness. We identified three themes associated with the consent and sexual agency implications of survival sex: power, coercion, and sexual agency. Additionally, we recognized five factors that contribute to increased vulnerability to engage in survival sex, which we termed 'push factors': hunger, patriarchy, poverty, substance use, and insecure housing. Each of these factors contributes to a coercive environment that diminishes individuals' capacity to freely consent to sex, thereby limiting their ability to exercise sexual agency.
Study 3 used romantic satisfaction to differentiate between higher-quality and more problematic relationships when examining their impact on housing stability. Using four years of data from the longitudinal Health and Housing in Transition (HHiT) study, participants were grouped by homelessness patterns (chronic, episodic, transitional, and vulnerably housed) and classified by partnership status and romantic satisfaction. Two clusters emerged: 'low romantic satisfaction, low partner status frequency' and 'high romantic satisfaction, high partner status frequency'. We examined how the relationship pattern clusters were associated with days homeless over the four-year period and homelessness patterns and did not find a statistically significant result. We developed three path analysis models to explore the relationship between partner status (independent variable) and housing stability (dependent variable), with romantic satisfaction as a mediator. In each model, all variables were measured at one time point, with the dependent variables being measured in the subsequent year. While we hypothesized a significant indirect path in all three panels, full mediation was only observed in Panel 3 (Y3-Y4). Our results indicate a potential positive link between satisfactory partner relationships and increased housing stability. Future research can build on the three studies presented in this dissertation to examine the potential impact of partner relationships on housing stability or their role in helping individuals cope with homelessness
SPDEs with Infinite-Variance Lévy Noise
No full textThis thesis is devoted to the study of the existence and uniqueness of solutions for stochastic partial differential equations (SPDEs) driven by Lévy noise. The main contributions of this work are contained in the recent publications [32] and [5]. Article [32] focuses on a stochastic wave equation with multiplicative Lévy noise. We establish the existence and uniqueness of a random field solution, relying only on the integrability of the Lévy measure on the region |z| ≤ 1. Furthermore, we show that this solution has finite moments up to a certain stopping time, which depends on a bounded region of space. Article [5] studies a broader class of SPDEs driven by heavy-tailed Lévy noise, which includes the Parabolic Anderson Model (PAM) and the Hyperbolic Anderson Model (HAM). Specifically, we demonstrate the existence of solutions for SPDEs driven by symmetric α-stable Lévy noise. Using the Lepage representation of the noise and techniques borrowed from the theory of multiple stable integrals, we construct a solution that has a series representation which depends only on the points of the jump measure associated with the noise
In Vivo Dendritic Dynamics of Somatostatin-Expressing Interneurons (SST-INs) in the Primary Motor Cortex (M1) During Motor Learning
No full textThe primary motor cortex (M1) is critical for motor learning. Within M1, excitatory pyramidal neurons (PyrNs) undergo network re-organizations, forming task-specific ensembles. This process was recently discovered to be modulated by a functionally distinct ensemble of somatostatin-expressing inhibitory neurons (SST-INs) in M1 that predominantly express neuronal PAS domain 4 (NPAS4) upon motor learning. NPAS4+ SST-INs reduced inhibition onto postsynaptic PyrNs, facilitating circuit reorganization, and thus, motor learning. NPAS4+SST-IN ensemble hints at learning-associated input integration in SST-INs, however, the underpinning of this process remains unclear. To investigate this, I employ in vivo two photon Ca²⁺ imaging in awake mice to chronically monitor dendritic and synaptic activity of SST-INs throughout training for head-restrained bi-directional disk task, followed by identification of NPAS4+ SST-IN ensemble in M1. Building upon finding of branch-specific Ca²⁺ spikes on layer 5 PyrNs' apical dendrites in M1during motor learning, which induces potentiation of learning-related spines, I hypothesize that motor learning-induced dendritic Ca²⁺ activity will trigger and maintain experience-dependent synaptic plasticity in dendrites of NPAS4+ SST-INs. We observed two distinct SST-IN populations during motor training: neurons showing increased ('positive') or decreased ('negative') dendritic activity. Task-specific NPAS4+ SST-INs displayed a nuanced pattern of synaptic integration. In the early training phase, these neurons exhibited broader, non-specific synaptic engagement, characterized by higher spine-dendrite co-activity. As training progressed, we observed a selective refinement of synaptic connections, suggesting an active mechanism of circuit optimization. Overall, this research elucidates dendritic and synaptic plasticity of SST-INs during motor learning, offering insights into neural plasticity and potential therapeutic strategies for neurological injury rehabilitation