University of Windsor
  • Windsor, Ontario, Canada
Recent publications
Migrant farm workers recruited under Canada’s temporary employment programs work in difficult environments, under poor working conditions, and live in unsafe housing in remote rural communities. Fearful of repatriation or replacement, many accept their working and living conditions as part of a necessary sacrifice to improve their living conditions and those of their families in the countries of origin. At the same time, some migrant farm workers assert their agency by escaping from farms, subverting regulations, or challenging various forms of discipline used to control their bodies and activities. Following Isin and Nielsen (2008), we refer to these actions as “acts of citizenship.” Drawing on research conducted among migrant farm workers during the COVID-19 pandemic in the province of Quebec, Canada, we situate these acts, particularly the tendency to escape from abusive and exploitative working relationships, in a particular space and time shaped by the COVID-19 pandemic. More specifically, we demonstrate the link between these acts and certain conditions and opportunities that arose at that time, such as increased support for migrant farmworkers by a non-governmental organization and the facilitation of movement of migrant farmworkers across the Canada-U.S.-border by the “migration industry.”
The COVID-19 pandemic has created severe challenges for public transit systems. This article examines its impact on six Ontario transit systems. Using qualitative data from fourteen interviews with public transit officials and data from municipal documents and public announcements, the article examines whether measures introduced by the transit authorities addressed the issue of transit equity in the pandemic’s first year. The findings show that transit officials were aware of transit inequity—transit service cuts disproportionately affected the most vulnerable. Transit officials also raised issues relating to transit equity in their appeals to senior governments for more funding. It is, however, important not to overstate the prevalence of transit equity at this time. Transit officials and transit documents rarely used the term transit equity and there is limited evidence that considerations of procedural equity influenced decision-making in the period studied. Transit systems were forced to prioritize the maintenance of some level of reduced service during the pandemic with almost no capacity to introduce measures to advance transit equity.
The emergence of blockchain creates a new possibility to solve the fraudulent problem of financial supply chain. We construct a game model to verify the strategic choice of the financial supply chain in an uncertain environment. We derive the equilibrium results and investigate the strategic choice of blockchain service for the financial supply chain. We also study the product price, product quantity, financing interest rate, and supply chain risk transmission, respectively. Specifically, when the blockchain is not considered, the financial model of supply chain led by core enterprises depends on firms’ reputation. The retail and wholesale prices increase when fraud occurs or consideration payment increases. Besides, the market stability reduces price performance. In the blockchain environment, the strategic choices are divided into two cases: when choosing the core enterprise model and the third-party service model, the third-party service model is the equilibrium strategy; when choosing the third-party service model and the platform model, the platform model is the equilibrium strategy.
Background: This paper highlights the formulation of a solid THC-loaded ingestible prepared from pure THC distillate. A THC ethanol-assisted cannabinoid nanoemulsion (EACNE) was created without the need for specialized emulsification equipment such as a high-pressure homogenizer or a microfluidizer. Stress-testing was performed on the EACNE to evaluate its chemical and colloidal stability under the influence of different environmental factors, encompassing both physical and chemical stressors. Subsequently, the EACNE was converted to a solid powdery material while still retaining its THC potency, and suited for “microdosing” applications. Methods: An ethanol-assisted emulsification method was used to generate a THC nanoemulsion. The EACNE was fully characterized, imaged, and subjected to stress-tests. The EACNE was then mixed with a solid matrix material post facto and lyophilized to create a solid ingestible substance. Upon ball-milling, a dense powdery material was obtained. Flow properties and thermal properties of this material were recorded. Potency of the material was evaluated in triplicate using HPLC and correlated with the potency of the starting EACNE. Results: EACNE had an average lipid droplet size of ca. 190 nm, with a polydispersity index (PDI) of 0.15, and an average droplet zeta potential of -49±10 mV. The nanoemulsion was colloidally stable for at least 6 weeks, with no meaningful change in cannabinoid potency over the experimental period, as determined by HPLC analysis. The EACNE remained stable when subjected to physical stresses such as heat, freeze/thaw cycles, carbonation, dilution to beverage concentrations, high sucrose concentrations, and a pH range between 5-8. The effect of undesirable events during the lyophilization of the EACNE were minimized by ball-milling the resulting solid. The microencapsulated EACNE demonstrated limited free-flowing behaviour but was freely redispersible in water without any visible phase separation. Conclusions: A solvent-mediated emulsification protocol creates a THC-loaded nanoemulsion that can subsequently be converted to a water-soluble powder. These materials are particularly suited for THC “microdosing”, a practice that might decouple the health benefits of THC from its psychotropic effects.
A method is proposed by which the power consumption of a biologically detailed digital neuron implementation can be reduced without modification to the digital neuron’s hardware architecture and independent of the neuron model. This method results in substantial power savings by causing the neuron to enter a quasi-functional state when low input stimulus is received. This approach is analogous to the function of real biological neurons as they enter a low-activity state for low stimulus. The shifts in neuronal activity created by the novel method allow for the membrane potential to remain uncorrupted over a large domain of input synaptic current, while avoiding unnecessary computations and switching activity. The digital hardware implementation results are presented and discussed, and it is shown that the behaviour of the neuron is unaffected using the novel method. The power consumption of the implemented digital neurons is compared with traditional implementations, and considerable power savings are shown.
Background Animal movement data are regularly used to infer foraging behaviour and relationships to environmental characteristics, often to help identify critical habitat. To characterize foraging, movement models make a set of assumptions rooted in theory, for example, time spent foraging in an area increases with higher prey density. Methods We assessed the validity of these assumptions by associating horizontal movement and diving of satellite-telemetered ringed seals (Pusa hispida)—an opportunistic predator—in Hudson Bay, Canada, to modelled prey data and environmental proxies. Results Modelled prey biomass data performed better than their environmental proxies (e.g., sea surface temperature) for explaining seal movement; however movement was not related to foraging effort. Counter to theory, seals appeared to forage more in areas with relatively lower prey diversity and biomass, potentially due to reduced foraging efficiency in those areas. Conclusions Our study highlights the need to validate movement analyses with prey data to effectively estimate the relationship between prey availability and foraging behaviour.
Detection of hazardous toxic gases for air pollution monitoring and medical diagnosis has attracted the attention of researchers in order to realize sufficiently sensitive gas sensors. In this paper, we fabricated and characterized a Titanium dioxide (TiO2)-based gas sensor enhanced using the gold nanoparticles. Thermal oxidation and sputter deposition methods were used to synthesize fabricated gas sensor. X-ray diffraction analysis was used to determine the anatase structure of TiO2 samples. It was found that the presence of gold nanoparticles on the surface of TiO2 enhances the sensitivity response of gas sensors by up to about 40 %. The fabricated gas sensor showed a sensitivity of 1.1, 1.07 and 1.03 to 50 ppm of acetone, methanol and ethanol vapors at room temperature, respectively. Additionally, the gold nanoparticles reduce 50 seconds of response time (about 50% reduction) in the presence of 50 ppm ethanol vapor; and we demonstrated that the recovery time of the gold decorated TiO2 sensor is less than 40 seconds. Moreover, we explain that the improved performance depends on the adsorption-desorption mechanism, and the chemical sensitization and electronic sensitization of gold nanoparticles. Detection of hazardous toxic gases for air pollution monitoring and medical diagnosis has attracted the attention of researchers in order to realize sufficiently sensitive gas sensors. In this paper, we fabricated and characterized a Titanium dioxide (TiO2)-based gas sensor enhanced using the gold nanoparticles. X-ray diffraction analysis was used to determine the anatase structure of TiO2 samples. It was found that the presence of gold nanoparticles on the surface of TiO2 enhances the sensitivity response of gas sensors by up to about 40 %. The fabricated gas sensor showed a sensitivity of 1.1, 1.07 and 1.03 to 50 ppm of acetone, methanol and ethanol vapors at room temperature, respectively. Additionally, the gold nanoparticles reduce 50 seconds of response time (about 50% reduction) in the presence of 50 ppm ethanol vapor; and we demonstrated that the recovery time of the gold decorated TiO2 sensor is less than 40 seconds. Moreover, we explain that the improved performance depends on the adsorption-desorption mechanism, and the chemical sensitization and electronic sensitization of gold nanoparticles.
This paper’s thesis is that the fallacies should not be taught to undergraduates. Besides some bad influences, this is not only because doing so steals time more valuably spent elsewhere, but also because the field is now so complex (overlapping concepts, theories and disciplines), that we lack knowledgeable instructors and sophisticated students. The study of theories involving fallacies, however, remains viable.
Constraint programming (CP) has been recently in the spotlight after new CP-based procedures have been incorporated into state-of-the-art solvers, most notably the CP Optimizer from IBM. Classical CP solvers were only capable of guaranteeing the optimality of a solution, but they could not provide bounds for the integer feasible solutions found if interrupted prematurely due to, say, time limits. New versions, however, provide bounds and optimality guarantees, effectively making CP a viable alternative to more traditional mixed-integer programming (MIP) models and solvers. We capitalize on these developments and conduct a computational evaluation of MIP and CP models on 12 select scheduling problems. ¹ We carefully chose these 12 problems to represent a wide variety of scheduling problems that occur in different service and manufacturing settings. We also consider basic and well-studied simplified problems. These scheduling settings range from pure sequencing (e.g., flow shop and open shop) or joint assignment-sequencing (e.g., distributed flow shop and hybrid flow shop) to pure assignment (i.e., parallel machine) scheduling problems. We present MIP and CP models for each variant of these problems and evaluate their performance over 17 relevant and standard benchmarks that we identified in the literature. The computational campaign encompasses almost 6,623 experiments and evaluates the MIP and CP models along five dimensions of problem characteristics, objective function, decision variables, input parameters, and quality of bounds. We establish the areas in which each one of these models performs well and recognize their conceivable reasons. The obtained results indicate that CP sets new limits concerning the maximum problem size that can be solved using off-the-shelf exact techniques. History: Accepted by Pascal Van Hentenryck, Area Editor for Computational Modeling: Methods & Analysis. Supplemental Material: The software that supports the findings of this study is available within the paper and its Supplemental Information ( ) as well as from the IJOC GitHub software repository ( ) at ( ).
This paper considers the stabilization problem for a class of nonlinear systems in the presence of mismatched disturbances. To achieve this, a differentiator is defined using virtual controls and modified error compensation signals, and the output of the system is asymptotically stabilized by a command-filtered backstepping control scheme combined with a mismatched finite-time disturbance observer. In the employed disturbance observer, the imposed external disturbances are identified precisely within the finite-time period. This produces a better transient performance compared to the Lyapunov parameter estimation method. In addition, a wider range of disturbances can be included as the common restrictive condition is no longer applied to the first derivatives of disturbances. Apart from the functionalities of the employed disturbance observer, the proposed control scheme addresses the problem of the explosion of complexity caused by higher-order differentiation. As a result, when applied to a more complicated system, this method can significantly reduce the complexity of calculation. In the final step, by means of the common Lyapunov function, the finite-time estimation process of the disturbance observer and the asymptotic stability of the given control scheme is shown. Finally, a simulation example is provided to show the effectiveness of the theoretical developments.
In this paper, we introduce the Setup Carryover Assignment Problem (SCAP), which consists of determining the setup carryover plan of multiple items for a given lot size over a finite planning horizon with the objective of maximizing setup cost savings. This problem is an extension of the standard Capacitated Lot Sizing Problem (CLSP). We show that the straightforward linear programming (LP) formulation of the problem provides a fractional solution. However, we propose an alternative integer linear program (ILP) and show that it has a totally unimodular property and thus yields an integer solution. Therefore, SCAP is solvable in polynomial time.
Narwhals (Monodon monoceros) are increasingly exposed to anthropogenic disturbances that may increase their stress levels with unknown consequences for the overall population dynamics. The validation and measurement of chronic stress biomarkers could contribute toward improved understanding and conservation efforts for this species. Dehydroepiandrosterone (DHEA) and its sulfated metabolite DHEA-S are collectively referred to as DHEA(S). Serum DHEA(S) concentrations combined in ratios with cortisol [cortisol/DHEA(S)] have been shown to be promising indicators of chronic stress in humans, domestic animals, and wildlife. During field tagging in 2017 and 2018 in Baffin Bay, Nunavut, Canada, 14 wild narwhals were sampled at the beginning and end of the capture-tagging procedures. Serum DHEA(S) were measured with commercially available competitive enzyme-linked immunosorbent assays (ELISA) developed for humans. A partial validation of the ELISA assays was performed by the determination of the intra-assay coefficient of variation, confirmation of the DHEA(S) dilutional linearity, and the calculation of the percentage of recovery. Mean values (nanograms per milliliter ± standard error of the mean) of narwhal serum cortisol, DHEA(S), and cortisol/DHEA(S) ratios, at the beginning and at the end of handling, respectively, are reported (cortisol = 30.74 ± 4.87 and 41.83 ± 4.83; DHEA = 1.01 ± 0.52 and 0.99 ± 0.50; DHEA-S = 8.72 ± 1.68 and 7.70 ± 1.02; cortisol/DHEA = 75.43 ± 24.35 and 84.41 ± 11.76, and cortisol/DHEA-S = 4.16 ± 1.07 and 6.14 ± 1.00). Serum cortisol and cortisol/DHEA-S were statistically higher at the end of the capture (P= 0.024 and P= 0.035, respectively). Moreover, serum cortisol at the end of handling was positively correlated to total body length (P = 0.042) and tended to be higher in males (P = 0.086). These assays proved easy to perform, rapid, and suitable for measuring serum DHEA(S) of narwhals and that calculated cortisol/DHEA(S) are potential biomarkers for chronic stress in narwhals and possibly other cetaceans.
Laser cladding is a directed energy deposition process and can lead to high residual stresses, which can compromise the quality of the specimen. As a result, it is crucial to accurately predict and investigate the residual stress distribution in cladded parts and understand the formation mechanisms. In this study, a thermo-mechanical metallurgical simulation model of the laser cladding process was developed for three different deposition sequences for a thin wall hexagon with inner junctions to investigate the formation of residual stress and distortion. The study was performed for single and multilayer scenarios. Two types of computational techniques, the detailed transient approach and the imposed thermal cycle approach, were performed and comparisons conducted. Consistent results were observed when comparing the resultant stress patterns for the single layer; subsequently, the imposed thermal cycle method was applied for the five-layer models. A preheat scenario is explored. This reduced the computational cost significantly, but the stress patterns were not similar. This indicates that building up worn regions at the top of a thin-walled component, such as a roll die, needs to be investigated further as unique issues have been highlighted. The differences between the implemented computational techniques are described as well as the advantages and disadvantages of each. Knowledge obtained from these case studies provides a foundation for efficient and rapid optimization of laser cladding processes, with the aim of minimizing residual stress in both simple and complex laser cladding structures.
Given the growing ecological footprint of anthropomorphic activities, considering the environmental impacts of any process is becoming increasingly important. This is especially true for the healthcare industry, whose objective of maintaining human health standards is impeded by its own unsustainable practices. To this end, life cycle analysis is particularly helpful. There have not been many life cycle analyses performed on a healthcare device or on medical procedures. Many medical devices are single use, which leads to a significant waste management problem, particularly as plastic is widely used in their composition. The objective of this study is to present a life-cycle-thinking-based approach to compare the environmental impacts associated with single-use electrophysiological catheters with the sterilization of reusable electrophysiological catheters using hydrogen peroxide, ethylene oxide, and peracetic acid. A life cycle assessment was conducted considering different use, disinfection, and disposal scenarios for electrophysiological catheters, using ReCiPe midpoint and endpoint analysis with the SimaPro software. The findings indicate that using single-use disposable electrophysiological catheters, instead of sterilizing a single catheter using either ETO or hydrogen peroxide and reusing multiple times, is preferable from a purely environmental perspective. However, the costs reduce drastically when equipment is sterilized and reused instead of disposing them after using one time. This in turn illustrates that depending on the process, sanitizing and reusing medical devices may not always be more resource-efficient than single device usage. From a cost perspective, ETO sterilization has the lowest costs, and yet it leads to an aggregate environmental impact of over 20 times compared to the single-use scenario, mainly due to the required detoxification process. The outcomes of this research will assist the health care industry in identifying the most suitable operational procedures considering patient safety, economics, and environmental stewardship, and in developing policies and guidelines for a more sustainable healthcare sector.
Groundwater contributions to streamflow significantly influence the structure and function of riverine ecosystems, particularly in glacierized catchments where there are marked differences in water sources and subsurface flow paths. Here, we investigated spatial and temporal variation in relationships between water sources, flow paths, physical and chemical processes, organic matter, microbial biofilms, and macroinvertebrates across groundwater-fed streams in the glacierized Toklat River catchment of Denali National Park, Alaska. Streams fed predominantly by seepage from the valley sides were perennial, whereas streams sustained by glacial meltwater seepage were ephemeral. Differences in environmental conditions between flow regimes appeared to influence spatial and temporal patterns of organic matter, linking to macroinvertebrate community dynamics. Macroinvertebrates in perennial streams were supported by fine particulate organic matter from subsurface flow paths during summer, transitioning to a combination of fine particulate matter and leaf litter in autumn. In comparison, macroinvertebrates inhabiting ephemeral streams, which only flowed during autumn, were supported by leaf litter. Some macroinvertebrate taxa were unaffected by turnover in organic matter, indicating potential plasticity in organic matter resource use. Findings highlight the importance of considering spatial and temporal variation in groundwater-fed streams, considering that projected hydrological changes under a changing climate may have significant implications for these systems.
In recent years, vaping has increased in both popularity and ease of access. This has led to an outbreak of a relatively new condition known as e-cigarette/vaping-associated lung injury (EVALI). This injury can be caused by physical interactions between the pulmonary surfactant (PS) in the lungs and toxins typically found in vaping solutions, such as medium chain triglycerides (MCT). MCT has been largely used as a carrier agent within many cannabis products commercially available on the market. Pulmonary surfactant ensures proper respiration by maintaining low surface tensions and interface stability throughout each respiratory cycle. Therefore, any impediments to this system that negatively affect the efficacy of this function will have a strong hindrance on the individual's quality of life. Herein, neutron spin echo (NSE) and Langmuir trough rheology were used to probe the effects of MCT on the mechanical properties of pulmonary surfactant. Alongside a porcine surfactant extract, two lipid-only mimics of progressing complexity were used to study MCT effects in a range of systems that are representative of endogenous surfactant. MCT was shown to have a greater biophysical effect on bilayer systems compared to monolayers, which may align with biological data to propose a mechanism of surfactant inhibition by MCT oil.
This paper investigates whether restrictive immigration policy affects earnings among White, African-American, and Latinx US citizens. Incorporating sociological theories of race that point to state surveillance of Black and Latinx bodies as a linchpin of racial inequality, we ask: Do immigration policies that expand the reach of law enforcement spill over to lower or to raise earnings of employed US citizens? If so, are the effects of these policies greater for Latinx and African-American citizens compared to their White counterparts? Are the effects of these policies stronger among Latinx and African-American men—who are more directly targeted by surveillance policing as a function of their gender—than for co-ethnic women? To investigate these questions, we combine two nationally representative longitudinal datasets—the 1979 National Longitudinal Survey of Youth and the 1997 National Longitudinal Survey of Youth. We find that immigration policies that expand the reach of law enforcement raise wages among native-born Whites. However, we also find that state policies enhancing immigration law enforcement decrease wages among Latinx and African-American citizens compared to Whites. We find no gender/race interactions influencing spillover effects of immigration policy on earnings.
Introduction: Reactive arthritis (ReA) is a joint inflammation that follows an infection at a distant site, often in the gastrointestinal or urogenital tract. Since the emergence of COVID-19 in January 2020, several case reports have suggested a relation between reactive arthritis and severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), due to the novelty of the disease, most findings were reported in the form of case reports or case series, and a comprehensive overview is still lacking. Methods: We searched PubMed/Medline and Embase to identify studies addressing the association between ReA and COVID-19. The following terms were used: ["Reactive Arthritis" OR "Post-Infectious Arthritis" OR "Post Infectious Arthritis"] AND ["COVID-19" OR "SARS-CoV-2" OR "2019-nCoV"]. Results: A total number of 35 reports published up to February 16th, 2022, were included in this study. A wide range of ages was affected (mean 41.0, min 4 max 78), with a higher prevalence of males (61.0%) from 16 countries. The number and location of the affected joints were different in included patients, with a higher prevalence of polyarthritis in 41.5% of all cases. Cutaneous manifestations and visual impairments were found as the most common associated symptoms. Most patients (95.1%) recovered, with a mean recovery time of 24 days. Moreover, arthritis induced by COVID-19 seems to relieve faster than ReA, followed by other infections. Conclusion: ReA can be a possible sequel of COVID-19 infection. Since musculoskeletal pain is a frequent symptom of COVID-19, ReA with rapid onset can easily be misdiagnosed. Therefore, clinicians should consider ReA a vital differential diagnosis in patients with post-COVID-19 joint swelling. Additional studies are required for further analysis and to corroborate these findings.
Monophosphine-ligated nickel compounds e.g., [Ni(PPh3)4] are relevant as active catalysts across a broad range of reactions. This report expands upon the coordi-nation chemistry of this family, offering the reactivity of allyl- and vinyl-substituted diphenylphosphine (PPh2R) with [Ni(COD)2] (COD = 1,5-cyclooctadiene). These reac-tions provide three-coordinate dinickelacycles that are intermolecularly tethered through adjacent {Ni}-olefin interactions. The ring confirmation of such cycles has been studied in the solid-state and using theoretical calcula-tions. Here, a difference in reaction outcome is linked to the presence of an allyl vs. vinyl group, where the former is observed to undergo rearrangement, bringing about challenges in clean product isolation.
Quartz Crystal Microbalance (QCM) operates based on a shift in its resonant frequency due to addition of mass in its mass loading area. QCM has been widely used in detecting microgram level surface mass changes in both liquid and gas phase. The conventional QCM structure possesses a circular electrode configuration which uniformly disperses the mass loading area across its surface. However, due to the energy trapping effect, the radial distribution of mass sensitivity is found to be unequal and diminished towards the edges of the electrode. In this paper, the influence of the energy trapping effect is investigated to identify effective regions on the electrode contributing to the frequency shift. From this analysis, a novel topology is proposed by designing a unique distributed electrode configuration to effectively utilize energy trapping effect and enhance the device mass sensitivity while utilizing smaller mass loading area. This proposed electrode configuration is contrasted with the conventional circular electrode and ring-dot electrode configurations based on their mass sensitivity and uniformity distribution. The conducted analysis revealed that the novel electrode topology attains a noticeably higher mass sensitivity and a comparable uniformity distribution in contrast to the conventional circular and ring-dot electrode configurations.
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Kathryn Anne Pfaff
  • Faculty of Nursing
Carlin Miller
  • Department of Psychology
Alan Scoboria
  • Department of Psychology
Dale Rajacich
  • Faculty of Nursing
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