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Identification of Genetic Variants Impacting Fetal Outcomes Following in utero Porcine Reproductive and Respiratory Syndrome Virus Challenge
No full textPorcine reproductive and respiratory syndrome (PRRS) remains one of the most economically damaging viral diseases in swine, causing an estimated annual loss exceeding $1.2 billion in the U.S. alone. While substantial host genetics research has focused on PRRS control in nursery and growing pigs, most notably identifying a QTL on SSC4 (the “WUR” locus) associated with lower viremia, far less is known about the genetic factors influencing fetal responses during late-gestation PRRSV infection. A genome-wide association study (GWAS) conducted by Yang et al. (2016) (trial-1) revealed a significant SNP (DRGA0008048) on SSC7 linked to fetal viability, implicating nearby thyroid-related genes (DIO2 and TSHR) as positional candidates. These genes may affect fetal resilience partly through fetal thyroid hormone metabolism, previously observed to be disrupted under PRRSV infection. Thus, this thesis investigates whether genetic variants in the DIO2–TSHR region and other regions in the fetal genome affect fetal resilience to PRRSV-2 infection in pregnant gilts. First, an independent maternal PRRSV-2 challenge trial (trial-2) focusing on the DRGA SNP near DIO2 showed that although the favorable B allele for fetal viability in the Yang et al.’s GWAS was significantly associated with lower fetal serum T4 level and increased proximal humeral ossification area, it did not consistently predict higher fetal viability. Second, a follow-up study then identified a missense variant (p.Asn91Ser) in DIO2 using targeted Sanger sequencing, but this mutation similarly had minimal effect on fetal PRRS outcomes, albeit it influenced DIO2 mRNA levels in fetal heart and kidney. Third, to understand the apparent discrepancy between the original Yang et al.’s GWAS signal and these negative findings, pooled whole-genome sequencing (Pool-Seq) was used to screen the DIO2–TSHR region for trial-2 gilts. Targeted Sanger sequencing was also conducted for selected DIO2 SNPs for parental animals across trials. This analysis revealed shifts in genotype and haplotype frequencies in the BB (favorable genotype for fetal viability) gilts over time between two trials, likely the result of ongoing selection pressures. This result suggests selection or genetic drift might have disrupted or reduced linkage between the originally discovered DRGA SNP marker and any causal variant(s) in that region.
Finally, integrating fetal genotypes with thymic RNA sequencing data in fetuses categorized by PRRS susceptibility demonstrated that severe fetal infection was related to downregulation of early thymocyte development genes and upregulation of interferon-driven pathways. Interaction eQTL analyses identified genotype by PRRS susceptibility group effects in immune-related genes, such as TMEM98, implicated in T helper 1 (Th1) cell differentiation, highlighting a complex interplay between host genetics and fetal thymic transcriptional responses in reproductive PRRS. These transcriptional responses and associated DNA variants could be applied to predict fetal PRRS susceptibility. Collectively, current evidence indicates that the DIO2 locus is not yet definitively proven for improving fetal resilience in reproductive PRRS. Inconsistencies across trials, potentially driven by selection or genetic drift over the time gap indicate the need for careful experimental design for further validation, finer mapping, or direct functional studies before applying this region in breeding programs. By combining genomic and transcriptomic analyses, this thesis expanded our understanding of fetal pig responses to PRRSV-2 infection at late gestation, ultimately guiding future efforts to identify causal variants and robust biomarkers for enhanced reproductive outcomes in PRRS-challenged sow herds
Airflow Analysis of the Upper Airway in Skeletal Class II Growing Patients with Constricted Maxilla Treated using Twin Block and Hyrax
No full textSleep-breathing disorders (SBD) affect individuals on a global scale, encompassing a spectrum of conditions with obstructive sleep apnea (OSA) and snoring at the extremes. The prevalence of OSA in children is estimated to be between 1-5%. In patients with OSA, episodes of hypopnea (partial breathing cessation) or apnea (complete breathing cessation) can occur multiple times during sleep, leading to chronic hypoxia and various health issues, including hypertension, cardiovascular diseases, impaired growth, behavioral problems, and reduced quality of life. While nocturnal polysomnography is the gold standard for OSA diagnosis, its high cost and long wait times limit accessibility, particularly in Canada, where the demand for testing significantly exceeds capacity.Certain oral anatomical features, such as a high-arched or narrow upper jaw and retruded lower jaw, may be linked to pediatric OSA, making dentists potential early screeners. Treating OSA requires a multidisciplinary approach, with sleep physicians overseeing diagnosis and dentists managing oral appliances that aid treatment in selected cases. Orthodontic interventions, including mandibular advancement and maxillary expansion, aim to improve localized upper airway dimensions. For instance, the Hyrax appliance facilitates maxillary expansion, potentially enhancing nasal airflow, while the Twin Block appliance positions the mandible forward, which may increase oropharyngeal space. The actual impact of those increases on breathing function is still controversial.This research investigated the relationship between upper airway (UA) dimensions, inspiratory flow, airway resistance, and SBD-related questionnaires in children undergoing maxillary expansion and Class II malocclusion mandibular corrector devices. Additionally, it explored whether UA volume changes correlate with airway resistance changes. The primary objectives included developing a segmentation technique for volumetric analysis of the UA, validating a pressure drop experimental analysis, and assessing airflow changes before and after orthodontic interventions. Additionally, this study aimed to determine whether the order of treatment influences UA and airflow changes, increasing our understanding of the impact of orthodontic treatment on some UA parameters.The research hypotheses posit that mandibular protrusion and maxillary expansion will lead to observable changes in UA dimensions and airflow. The study tested the null hypotheses regarding the lack of airflow changes post-treatment and the absence of correlations among various measured parameters. Ultimately, this work aimed to enhance understanding of orthodontic impacts on upper airway dynamics and airflow resistance, potentially informing better treatment strategies for OSA in children.Thirty-two participants were analyzed, 10 in control, 12 in Hyrax, and 10 in Twin Block groups. The mean age at T1 was 10.4 years of age and at T3 was 12.1 years of age. 75% of the hyrax group was female, 20% of the twin block groups were female and 60% of the control group was female. The mean treatment time was 1.7 years. Results showed that the Hyrax group had a mean decrease in air resistance of 0.4 cmH2O/L/s, a mean increase in peak nasal inspiratory flow of 20 L/min, a mean increase in peak oral inspiratory flow of 51L/min, a mean volume increase of 10.7 cm3, a mean minimal cross-sectional area increase of 86 mm2. All these measurements were statistically significant (p<0.05). The Twin Block group showed statistically significant results in peak oral inspiratory flow with a mean increase of 45L/min and a volumetric mean increase of 11.9cm3. The control group showed statistically significant results in peak nasal inspiratory flow with an increase of 30L/min
Diabetes Distress, Covid Crisis: Stories of Syndemic Suffering
No full textMy master’s thesis examines the syndemic interaction between diabetes and COVID-19 in Dhaka, Bangladesh, exploring how biological, social, and psychological dimensions coalesced to shape the lived experiences, healthcare access, and self-management practices of people with diabetes during the pandemic. Through a qualitative inquiry grounded in interpretivist/constructivist phenomenology, this research utilized illness narrative interviews with ten middle-income participants from Dhaka, Bangladesh who had type II diabetes and had contracted COVID-19 disease between 2020 to 2022.
Drawing on Singer’s syndemic theory and Corbin and Strauss’s illness management work theory, my thesis study highlights the multifaceted challenges faced by people with diabetes. These challenges range from disruptions in access to routine diabetes care, to difficulties in obtaining healthcare for their COVID-19 infection. I also share how self-care practices were impacted, for both diabetes and COVID-19. Additionally, psychological distress was heightened by isolation, fear, and anxiety, while social challenges, such as financial conditions, gender dynamics, or access to social support and telehealth, further shaped their lived experiences of diabetes and COVID-19 disease.
Findings reveal that the COVID-19 pandemic intensified pre-existing disparities in healthcare access, as resources were redirected by the government to manage the pandemic. Lockdowns, transportation bans, the collapse of outpatient services drastically reduced health care access, and this was exacerbated by fears propagated by the media, and the stigma of contracting COVID-19. In response to minimal healthcare services, people with diabetes adapted by modifying self-care practices for diabetes and COVID-19 disease, including diet, exercise, glucose monitoring, medication adherence, oxygen therapy, oxygen monitoring, and following COVID-19 safety protocols. However, they struggled to maintain these adaptations due to inconsistent medical supervision, limited medical resources, and heightened health anxieties, making these illness management tasks increasingly burdensome. The study also highlights the interplay between financial resources, gender dynamics, and social support networks with health experiences. Beyond physical health, the psychological toll of the pandemic on people with diabetes was profound. Fear of infection, social isolation, coupled with stigmatization upon contracting COVID-19 and pandemic-induced anxieties, contributed to participants’ psychological distress.
Viruses may cause disease in individuals, but pandemics unfold within populations, shaped by structural factors including, economic and social conditions, and government policies. In Bangladesh, COVID-19 created a syndemic with diabetes, as syndemic conditions arise when two diseases interact within a system of disadvantage exacerbating health disparities, fragile healthcare infrastructure, and socio-economic inequities. The existing vulnerabilities in Bangladesh provided a ripe context for a syndemic to emerge—one that profoundly impacted people with diabetes biologically, socially, and psychologically.
My study advocates for equitable and resilient healthcare policies that address the syndemic nature of pandemics, emphasizing the need of systemic reforms to mitigate the intensified impact of infectious and non-communicable diseases, considering all social determinants of health. Through its holistic examination, my research contributes to the growing discourse on syndemics, offering insights into how health crises unfold within structurally vulnerable contexts and urging a shift toward interdisciplinary, equity-driven healthcare preparations for the next pandemic
An Augmented Reality Training Protocol for Myoelectric Control
Get PDFIntroduction: Recent technological progression has led to advancements in myoelectric prostheses, such as multi-articulated hands, multi-degree of freedom, and pattern recognition (PR) control for enhanced functionality and intuitive control. Despite these advancements, prosthesis users often abandon their prostheses due to the struggle to control them efficiently. Achieving success with advanced prostheses control and use requires early and intensive training. Augmented Reality (AR) has recently been explored as a platform for enhancing pre-prosthetic training. AR training is promising as it offers an engaging experience and can allow individuals with limb loss to practice prosthetic control and usage before the fitting, leading to a facilitated transition to physical prosthesis use. However, current research on AR training has not sufficiently explored its effects on individuals with upper limb loss (ULL) since most studies involved able-bodied participants as a proxy for individuals with ULL. As a result, the effectiveness of this training method for individuals with ULL remains unclear.
Objectives: The first objective of this thesis was to develop a structured protocol for individuals with ULL to train on two-degree-of-freedom (2-DoF) PR prosthetic control in AR and test its feasibility. With that protocol developed, the second objective was to implement it to train individuals with ULL and evaluate the training effectiveness. Finally, the third objective of this thesis was to assess the transferability of skills learned during the training to unpracticed tasks within the AR environment.
Methods: To accomplish the first objective of this thesis, the main elements of the protocol were established with input from rehabilitation professionals, and its details were further developed under their guidance. A pilot study with three able-bodied participants was conducted to test the protocol and make adjustments based on the challenges encountered. After that, a case study involving one participant with ULL was carried out to finalize the protocol and further refine it for the targeted population. The second objective was completed by utilizing the finalized protocol to train four individuals with ULL on 2-DoF myoelectric PR control in AR and evaluate their progress throughout the training period. Finally, to achieve the third objective, pre-and-post-training evaluations were conducted. During these evaluations, participants performed a novel task not included in their training, and their performance was compared between both sessions to assess the transferability of their skills to unpracticed tasks.
Results: The research findings in this thesis indicated that some factors make AR training and evaluation sessions differ between able-bodied participants and participants with ULL. These factors include trial completion times, the need for breaks, and strategies for learning control and muscle calibration. These differences highlight the importance of involving the targeted population in this type of research. Additionally, AR confirmed its potential as an effective platform for myoelectric prosthetic training, as participants showed improvements in 2-DoF PR control of the virtual prosthesis throughout the training. Furthermore, notable improvements were observed between the baseline and post-training evaluations, demonstrating that AR training affects skill transferability to unpracticed tasks.
Recommendations: The training protocol developed in this thesis demonstrated that AR training improves prosthesis control and provides an enhanced training experience for individuals with ULL. This protocol can be used in future studies to conduct further research on the effectiveness of AR training and compare it to conventional training methods. It could also be adapted for at-home AR training programs in the future. Further work should investigate the transferability of the control skills acquired during AR training by individuals with ULL to physical prosthesis use in the real-world environment
Surface Interaction Mechanisms Underlying the Aggregation, Adsorption and Fouling Behaviors of Humic Acid in Aqueous Environment
No full textHumic substances are a complex mixture of organic compounds that almost exist in all natural resources of water and soil, which contribute significantly to the organic carbon pool. The structure of humic substances comprises of aliphatic and aromatic hydrocarbon moieties substituted with a variety of polar functional groups, resulting in the complex intermolecular interactions such as hydrogen bonding, hydrophobic force and electrostatic force, which governs the behaviors of humic substances in nature and engineering processes, including self-aggregation, adsorption on soil clays, formation of metal ion-HA complexation, and membrane fouling. This work systematically investigated the interaction mechanisms underlying various interfacial behaviors of humic acid (HA), which is a representative class of humic substances, at the nanoscale. More specifically, the intermolecular forces of HA interacting with surfaces bearing different functional groups, HA in absence/presence of divalent cations, model clay minerals, and zwitterionic monolayers were systemically studied using atomic force microscope (AFM) force measurements, theoretical simulation and many other analytical techniques.
(i) The interaction mechanism of HA with self-assembled monolayers (SAMs) of varied functional groups was investigated, and the average adhesion energy between HA and the SAMs followed the trend as: NH2-SAMs > CH3-SAMs > OH-SAMs > COOH-SAMs in 100 mM NaCl at pH 5.8, indicating a significant role of electrostatic attraction in contributing to HA adhesion, followed by hydrophobic interaction and hydrogen bonding. The adhesion energy was found to be dependent on NaCl concentration, Ca2+ addition and pH. The electrostatic attraction between NH2-SAMs and HA was pH responsive, based on which a recyclable magnetic Fe3O4 nanoparticles coated with (3-aminopropyl)triethoxysilane (APTES) was designed to absorb HA in wastewater.
(ii) The molecular interaction mechanism of HA aggregation with/without divalent cations was also studied. In the absence of divalent cations, the aggregation of HA in water was thermodynamically unfavorable based on free energy calculation, consistent with our force measurement results. Typically, pure repulsive force was detected during two HA surfaces approaching each other in aqueous solution. Divalent cations such as Cu2+, Zn2+, Ca2+ and Mg2+ significantly encouraged the aggregation and adhesion of HA mainly due to the bridging effect, but excess ions (e.g., Ca2+) suppressed such behavior. The adhesion energy followed the trend as: Cu2+ > Zn2+ > Ca2+ > Mg2+. The strong adhesion caused by Cu2+ originated from the synergistic bonding of Cu2+ with both the oxygen and the amine sites of HA, different from the single oxygen bonding for Zn2+, Ca2+ and Mg2+, which was further demonstrated by X-ray photoelectron spectroscopy (XPS) and Density functional theory (DFT) simulation.
(iii) For the adsorption of HA on model mineral surfaces (e.g., hydrophilic mica and hydrophobic talc), our results demonstrated that much stronger adhesion was detected for HA-talc at pH 5.8 compared to HA-mica due to the presence of hydrophobic interaction, which was consistent with our adsorption results. HA-mica adhesion strongly depended on the loading force and contact time, most likely caused by the short-range and time-dependent interfacial hydrogen bonding interaction under confinement.
(iv) The intermolecular interactions between HA and charged, zwitterion-like or zwitterionic surface were quantitatively measured. The adhesion energy in 10 mM NaCl solution at pH 5.8 was as follows: positively charged MTAC (terminated with -N+(CH3)3) > negatively charged SPMA (terminated with -SO3-) > zwitterion-like MTAC/SPMA mixture > zwitterionic MPC (terminated with -O3-PO(CH2)2N+(CH3)3) and DMAPS (terminated with -(CH3)2N+(CH2)3SO3-). The zwitterionic monolayers exhibited the smallest adhesion energy since the vertically oriented dipole moments of zwitterionic molecules were strong enough to induce the formation of a thick hydration layer, which could effectively prevent the adsorption and deposition of HA. It was also found that the adhesion energy for zwitterion-like and zwitterionic surfaces was pH-independent, while that for charged surfaces was pH-dependent.
Our studies provide systematic, quantitative information on the molecular interaction mechanism underlying various interfacial behaviors of humic substances, with useful implications for developing effective strategies to modulate the aggregation, adsorption, transport, antifouling and removal behaviors of humic substances in water for both natural and engineering applications
The vorticity field (left) and the SLA field (right) in the Labrador Sea from the CMEMS satellite altimetry: 2005-2020
No full textThe relative vorticity normalized by f field (left) and the Sea Level Anomaly (SLA) field (right) in the Labrador Sea from the CMEMS satellite altimetry from 2005 to 2020. The black arrows represent the geostrophic surface circulation. The anticyclones are indicated by the blue color in the vorticity field, corresponding with the positive SLA. And the cyclones are in red with the negative SLA
Numerical and Experimental Investigation of Solar Thermochemical Gasification of Solid Fuels in a Hybrid Porous Media Reactor
No full textWithin the framework of the ANID/FONDECYT/1241030 project, an experimental and numerical investigation was performed on the thermochemical gasification of solid fuels in a hybrid porous media reactor exposed to concentrated solar energy and in a chemically reacting fixed-bed for hydrogen (H2) and syngas production.
An up-to-date literature review on H2 and syngas production by thermochemical processes, including filtration combustion, porous media combustion, and hybrid filtration combustion (HFC), is presented from an experimental and numerical perspective. Incorporating solar energy and biomass, two of the most important Chilean renewable resources, is discussed as a key element for allothermal gasification. Building on the current state of the art in thermochemical gasification, this thesis aims to address key gaps in understanding the fundamentals of heat and mass transfer inside inert and hybrid porous media reactors.
In particular, this work aims to develop new permeability-based models, including intrinsic reacting particles using a porous media model (PMM) approach. The assessment of Reynolds number, inflow gas tempearture and oxidative atmosphere, and the feasibility of a 2D axisymmetric porous media numerical model to represent a 3D particle-resolved approach of carbon char gasification are investigated. The novelty of this research is tailoring a PMM approach, making results close to those obtained using a PRS model, opening new perspectives for the simulation of chemically reacting fixed-beds.
Due to the complexity and the lack of literature regarding the use of biomass as a solid fuel for solar-driven gasification, all numerical studies were performed using carbon char particles. In this regard, a comprehensive study of the gasification of carbon char particles inside a fixed-bed reactor was performed using a three-dimensional model to analyze the effect of the inflow gas temperature, oxidative atmosphere (Y_O2_in = 0.05, 0.11, and 0.233), and Reynolds number (Re_in = 10, 50, 75, and 100). This work is next extended using a 2D axisymmetric geometry and a continuum approach to investigate the use of simplified models to represent complex multiphysics reactive processes. Also, a macro-pore-resolved approach was studied against a PMM using a single carbon char particle. These studies were performed to better understand the heat and mass transfer behavior of the phenomenon, specially at a pore-scale level, where porosity, tortuosity, effective diffusivity, dispersion, and thermal conductivity play a crucial role.
Regarding experimental-specific goals, this work aims to perform experiments in a hybrid porous media reactor exposed to concentrated solar energy, focusing on hydrogen and syngas production, and identify the most significant operational parameters according to experimental and numerical results to propose improvements to the processes for further research. In this regard, experimental research was conducted on the interaction of different mixtures of solid fuels inside a solar-driven gasifier for H2 and syngas production at low temperatures (600 K). Since the ultimate numerical approach is the simulation of the solar-driven gasification reactor, a 3D-CFD based porous media model including char reacting particles treated as porous and inert solid particles is mathematically described.
Finally, an extension of this thesis and future recommendations are given regarding experiment designing, chemical kinetics, use of new solid and gaseous fuels, and key aspects to achieve a continuous operation of the system
Navigating Institutional Change in Higher Education: Leadership Challenges
No full textLike all higher education institutions, universities face tremendous pressures to continuously reform as a result of ever-changing conditions in both their internal and external environments. For example, neoliberal policies by many governments have led to the marketization of universities and cuts in government funding, which are among the factors putting pressure on both public and private universities to undergo institutional reform. The purpose of this paper is to examine leadership behaviors that are most effective in supporting universities to drive the needed institutional change in response to the increasing pressures to reform. The literature synthesis revealed that university leaders who demonstrate transformational leadership are more effective in leading these change efforts. Their ability to clearly communicate a compelling vision, serve as charismatic role models, encourage bold and innovative thinking, and show personal care for their followers during the transformation process is highly impactful. Leaders who optimally combine vision, focus, and implementation are more successful at carrying out change initiatives, often adopting a more flexible, emergent approach to change rather than a linear one