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The mechanisms of cardiac contraction impairment in salmonids by silver nanoparticles
Get PDFDue mainly to their unique antimicrobial property, silver nanoparticles (nAg) are used in everyday consumer products, such as cosmetics and textiles. It is expected that their use will only increase as the nanotechnology industry grows, resulting in a higher risk of nAg pollution in aquatic ecosystems and higher risk of uptake by fish. Previous studies have shown nAg to be harmful to fish, but little have focused on the cardiac impact these nanoparticles have. Callaghan et al. (2018) showed that nAg decreased cardiac contraction rate and peak contractile force in rainbow trout (Oncorhynchus mykiss) and suggested the nanoparticles induced these effects by impairing important proteins involved in excitation contraction coupling. This study aimed to investigate the mechanisms behind the nAg-induced cardiac contraction effects, determine if these effects were reversible and determine if cell size was influential. Ventricular strips from diploid Arctic char (Salvelinus alpinus) and diploid and triploid brook trout (Salvelinus fontinalis) were mounted in an isometrically contracting muscle physiology system to assess the effects of nAg as well as nifedipine and ryanodine on the force-frequency relationship, peak contractile force and post-rest potentiation (% PRP). nAg treatment of Arctic char strips resulted in a significantly higher mean maximum pacing frequency and lower mean peak force, suggesting nAg-interference with Na+/Ca2+ exchanger. Recovery tests involving the replenishment of saline were not successful, thereby implying nAg cardiac effects to be irreversible. No significant differences in peak force and % PRP of brook trout arose from nAg treatment, either pharmaceutical treatment or ploidy which suggested possible differences between species in excitation contraction coupling and nAg effects. Na+/K+ and total ATPase activity was also assessed in brook trout injected with 700 μg per kg nAg 24 hours before sampling and demonstrated nAg to decrease Na+/K+ ATPase activity significantly in both diploid and triploid fish, leading to the conclusion that nAg may affect cardiac contraction through at least two mechanisms: Na+/Ca2+ exchangers and Na+/K+ ATPases
Synthesizing pseudo-synchronous communication protocols for decentralized discrete-event control
Get PDFAssessment of sediment penetrability as an integrated in situ measure of intertidal soft-sediment conditions
Get PDFInfauna have an intimate relationship with the sediments they inhabit, and any study conducted upon infauna must, at the very least, describe sediment conditions. Common sediment assessments in intertidal systems include particle size distribution, as well as water and organic matter contents. These measures require extracting and processing a sediment core, and this disturbance may result in data that do not necessarily reflect in situ conditions. Sediment penetrability measured in situ by using a penetrometer can circumvent this limitation. However, relationships between sediment penetrability and other sediment variables are poorly understood, especially in coastal systems. We evaluated the relationship between sediment penetrability and other variables – depth to the apparent redox potential discontinuity, mean particle size, organic matter content, and water content – on tidal flats along the Pacific and Atlantic coasts of Canada. We also assessed if adding penetrability into environmental models of the infaunal community 6 improved model performance. We observed that while penetrability is statistically related to other sediment variables, relationships to covariates were weak. Further, inclusion of 8 penetrability with other sediment variables improved the performance of models predicting infaunal community composition. Therefore, penetrability can be considered a separate variable, and contributes to an integrated assessment of environmental conditions experienced by biota. Finally, since we evaluated this method in different soft-sediment intertidal ecosystems (mudflats to sandflats), this method is applicable to a range of systems in other geographical areas.type of work: Research Articlepublication status: Accepted for publicatio
Investigation of wavelength shifting materials in an active helium target and detector calibrations
Get PDFThe strong nuclear force, responsible for binding nucleons and nuclei together, has proved challenging for physicists to study experimentally. Asymptotic freedom allows the strong force to be studied and tested e↵ectively at high energies; however in medium to low energy regimes, it remains to be solved. To establish a deeper understanding of how particles behave at these energy scales, the A2 Collaboration
in Mainz, Germany, studies nucleon polarizabilites, which are fundamental structure constants specific to each nucleon. While these polarizability values are well established for protons, results obtained for the neutron remain unsatisfactory. To gain access to the neutron, the A2 Collaboration is using various helium targets: the cryogenic liquid 4He target that had been employed already, and the planned Active Helium target, set to contain gaseous helium isotopes. One of the main motivations for using the active target is it allows for the collection of scintillation light, which may be used to reduce backgrounds. However, the silicon photomultipliers in the prototype active volume are unable to detect the vacuum ultraviolet light emitted by the helium gas, and thus a wavelength shifting material is required. The work of this thesis examines various materials of this sort, including Tetraphenyl Butadiene, which has shown promising initial results and necessitates further examination.
This thesis also examines detector calibrations in the aforementioned liquid 4He experiment from June of 2019, which include time and analog to digital onversion, setting o↵set values, energy pedestals and energy gains. A brief discussion of the beginnings of polarizability extraction is also touched upon.
Hospice palliative care volunteers' attitudes, experiences, and perceived needs for training regarding medical assistance in dying
Get PDFTwo separate studies were conducted to investigate hospice palliative care (HPC) volunteers’ attitudes towards medical assistance in dying (MAiD), their thoughts about current controversies surrounding MAiD, and their perceived need for training regarding MAiD. In Study One, a focus group was held with three HPC volunteers. All three volunteers were in favour of MAiD and supported their patients’ right to request MAiD, as long as they were mentally competent. None of the volunteers knew whether their HPC program had a policy for volunteers about how to manage inquiries about MAiD from patients, patients’ family members or caregivers. In Study Two, 27 HPC volunteers from two different programs responded to an in-depth survey. Their responses indicated that they were supportive of MAiD and in favour of some of the proposed changes to the current MAiD legislation (e.g., advanced requests for MAiD for patients in the early stages of dementia). More than two-thirds (68%) of the volunteers did not know if their HPC program had a MAiD policy specifically for volunteers. The majority (83%) of the volunteers reported that if one of their patients decided to pursue MAiD and requested their presence when MAiD was being administered, they would feel comfortable attending. Limitations of this research, suggestions for future research are discussed, as well as recommendations for HPC volunteer policy and MAiD training
New measures for hot executive function
Get PDFThe purpose of the current study was to examine whether two new preschool-friendly versions of Delayed Match to Sample (DMS) and Delayed Non-Match to Sample (DNMS) could be used as measures for hot executive function. Ninety-four children completed three tasks: match to sample tasks (DMS and DNMS), Preschool Gambling Task (PGT), and an empathy task. The findings of the study indicated that there was a significant age difference in the performance of children in both DMS and DNMS tasks where four-year-old children overall performed better on both the tasks. It was also found that children overall performed better on DMS when compared to DNMS, which suggested that children were good at learning the matching rule. The findings also indicated that both DMS and DNMS were associated with PGT. More specifically, DNMS was related to the learning phase (first 30 cards) of PGT, while the DMS was related to the awareness phase (last block) of PGT. These results indicated that ‘conceptual’ scores on DMS were predictive of PGT awareness scores and the ‘learning’ scores on DNMS were predictive of PGT learning of index. Therefore, it was concluded that the results were indicative of having two distinct processes of decision making. Finally, it was also found that DNMS and DMS were positively associated with the empathy task
Does complexity matter? Visual and haptic identification of complex objects
Get PDFEncoding specificity, the phenomenon where performance is best when encoding and retrieval are similar, applies to object recognition. Individuals who learn to recognize objects by sight are better at visual identification than haptic identification. However, learning to recognize objects by touch leads to similar performance across haptic and visual identification, violating the principle of encoding specificity. Further, recent studies have found that object representations may rely on a verbal encoding process, but this may be attributable to the visual simplicity of the objects used. I therefore evaluated whether learning to recognize complex novel objects would generate similar performance as learning to recognize simple novel objects. Participants completed learning trials where they explored each object by sight or by touch, and test trials where they identified objects by sight and by touch. Bayesian analyses indicated similar erformance across object types: similar objects were confused more often than distinct objects, and participants who learned to identify objects by touch demonstrated a violation of encoding specificity. Further, an interaction between learning condition and stimulus type emerged: participants who visually learned to identify simple objects made fewer errors than those who haptically learned to identify simple objects. In contrast, identification performance for participants who visually or haptically learned to identify complex objects was comparable. The violation of encoding specificity therefore appears to be a more general consequence of object processing independent of stimulus complexity
A novel task contrasting visual object and scene perception in young adults
Get PDFYoung adults outperform older adults on memory tasks that require spatial, but not object, processing. Some research suggests that these spatial deficits extend to other types of cognitive processing, not just memory, and that deficits associated with all of these are caused by degradation of spatial relational representations. To address this in future studies, I designed a task that encompassed both object and spatial perception using the same task and same stimuli, going beyond previous paradigms which employed different tasks and stimuli. In a pilot study, nine young adult participants (age = 19.89, edu = 14.44) viewed a scene and a floor plan simultaneously, side-by-side, and judged whether object identity or location matched between the two. Across trials, the scene either matched the floor plan, the identity of an object differed from the floor plan, or the location of an object differed from the floor plan. Scenes were presented from a centre or off-centre viewpoint. Results revealed that accuracy rates were neither too high nor too low to make meaningful comparisons in task performance. While there were trade-offs between speed and accuracy, combining both measures showed that performance was well-matched across conditions. Viewpoint manipulation affected performance, with participants making more errors on location mismatch scenes presented from an off-centre viewpoint. These results suggest that the floor plan task is well-suited for comparing the differing processes involved in object and scene perception. Future studies will be able to compare performance between object and spatial conditions as well as between age groups
Optimizing equilibration time to enhance post-thaw viability of cryopreserved zebrafish (Danio rerio) ovarian fragments
Get PDFGermplasm cryobanks are a vital ex situ conservation strategy for preserving the genetic material of endangered species, as the process of cryopreservation enables living material to be stored without deteriorating almost indefinitely. However, cryopreservation protocols yielding a high post-thaw viability of germ cells are difficult to develop, as there are several interconnected steps that can significantly alter the outcome. The purpose of my study was to optimize the equilibration time for the cryopreservation of zebrafish (Danio rerio) ovarian fragments, since previous studies often neglected this step and instead utilized an arbitrary equilibration time. Using a repeated-measures design, ovarian fragments were exposed to an equilibration treatment (control, 15, 30, 45, or 60 minutes in experiment 1; 30, 60, 90, or 120 minutes in experiment 2) and cryopreserved via slow-cooling. Post-thaw viability was assessed using a Trypan Blue exclusion assay. A 60 minute equilibration yielded the highest viability of ovarian cells in
experiment 1 (55.68 ± 1.74%), whereas a 30 minute equilibration yielded the highest viability in experiment 2 (75.86 ± 2.44%), but was not significantly different from the 60 minute equilibration in experiment 2 (75.58 ± 2.04%) (p=0.9983). Equilibration as a factor alone accounted for a 48.71% increase in viability, confirming this step should not be overlooked. The method employed in this study can be used to calculate the optimal equilibration time for any fish species, a necessary step in developing effective cryopreservation protocols to preserve the genetic diversity of endangered species