Mount Allison University Digital Repository
Not a member yet
368 research outputs found
Sort by
Effect of disruption on wheel-running reinforcement on rates of wheel running and operant lever pressing in rats
Get PDFThe current study investigated the effects of interruptions in wheel running on operant responding for a fixed bout of wheel-running reinforcement. Interruptions in the fixed
bout of reinforcement occurred after rats completed different numbers of wheel revolutions and were designed to vary the local constraint on wheel running, while
holding constant the total number of revolutions per session, the overall constraint. Eleven female Long-Evans rats responded on response-initiated variable interval 15-s
schedules for the opportunity to run for 30 revolutions, with a 4.5-s wheel-brake asserted after 2, 5, 10 or 15 revolutions. After the brake disruption, rats had to complete the
remainder of the 30-wheel turns required for the bout of wheel-running reinforcement. Results showed that wheel-running rates and overall lever-pressing rates followed a
bitonic, inverted-U function for wheel revolutions completed before the 4.5-s interruption. These results suggest that interruptions of wheel-running within a reinforcement opportunity systematically altered wheel-running rates and lever-pressing rates. Notably, similar effects have been obtained when local constraint is manipulated as the number of wheel revolutions per reinforcement. Interruptions of wheel running within fixed bouts of wheel-running reinforcement, however, produced weaker effects than local constraint based on the number of revolutions per reinforcement, likely due to the wheel revolutions after the disruption which were required to complete each reinforcement. In sum, these results support an account based on local constraint on an automatically reinforced behavior rather than reinforcement magnitude to explain how wheel-running and lever-pressing rates change with revolutions per reinforcement
National identity & nationalism on hispaniola: an analysis of the current conflict between Haiti & the Dominican Republic
Get PDFA pathogenic examination of virulent and avirulent aerococcus viridans var homari
Get PDFThe American lobster (Homarus americanus) is the most successful commercial fishery in Canada. The industry creates 7800 jobs in the Atlantic region, making it a pivotal part of the local economy in rural Atlantic Canada. When lobsters are harvested, they are either sent directly to market, or kept in storage to ensure there is a supply of live lobster available for consumers year-round. The lobster fishery experiences periodic post-harvest loss due to an infection called gaffkemia. Gaffkemia is caused by the bacterium Aerococcus viridans var. homari. Large live lobster storage facilities have A. viridans screening procedures in place to limit post-harvest loss, but they are not sensitive enough to differentiate between naturally occurring virulent and avirulent strains. When a shipment tests positive for the bacterium, this creates a financial burden on the facility as they must treat the shipment and it must be sold at a lower value. This project hopes to characterize genomes of virulent and avirulent strains of A. viridans var. homari to identify the factors responsible for virulence in this bacterium. This project uses genomic
approaches to identify variations in the genomes of virulent and avirulent strains of A. viridans var. homari. Genomic polymorphisms were compared between the phenotypes and putative virulence factors and impacted metabolic pathways were identified. No pathways had a significantly different number of polymorphisms between the phenotypes. However, the results of this study do indicate that particular regions of the genome are more prone to mutation than others
Nanotoxicology: The impacts of 5 nm silver nanoparticles on protein synthesis of rainbow trout (oncorhynchus mykiss)
Get PDFSilver nanoparticles (nAg) are becoming increasingly prevalent in consumer products due
to their unique physicochemical properties. This excessive usage is causing nanoparticulate waste
to end up in the water column with the potential to affect aquatic organisms. Previous research has
shown damaging effects of engineered nanomaterials (ENMs) on various fish species with the
current study aimed to identify the impacts of polyvinyl pyrrolidone (PVP) capped 5 nm silver
nanoparticles on biochemical stress indicators and rates of protein synthesis in rainbow trout
(Oncorhynchus mykiss). Fish were exposed to 100 μg L-1 nAg or 0.22 μg L-1 AgNO3 for 48 hours
and tissue samples taken. Biological endpoints analyzed included hematocrit, gill sodium
potassium ATPase, heart acetylcholinesterase, and cortisol and malondialdehyde content.
Fractional rates of protein synthesis were determined by flooding dose method modified to use a
stable phenylalanine isotope tracer. No significant differences were observed between treatment
groups for any of the biologically relevant endpoints nor protein synthesis rates, although a
decreasing trend was observed for sodium potassium ATPase activity in nAg-exposed fish. Results
suggest that rainbow trout exposed to silver ENMs for 48 hours at the environmentally relevant
point-source exposure concentration tested are not expressing signs of significant damage nor
exhibiting impaired metabolism indicating that under short term conditions 5 nm PVP-capped nAg
at 100 μg L-1 is not acutely toxic. These findings are disputable as previous research has
demonstrated the toxic effects of ENMs on fish physiology, including on the endpoints analyzed
in this study. These results should encourage further research into longer exposure durations and
investigating other potential sublethal effects
Synthesis and characterization of dithiolene complexes of bismuth as green redox active catalysts
Get PDFCatalysts are essential in the majority of chemical reactions, allowing industrial processes to progress with increased efficiency, environmental sustainability and synthetic precision. Conventional catalysts employ transition metals that often have adverse effects on humans, terrestrial and aquatic organisms and ecosystems. Thus, the objective of this study is to develop an effective and environmentally sustainable catalytic complex that is capable of facilitating a two-electron transfer in complex reactions. Bismuth is a viable alternative and candidate for catalysis research as it is less toxic, environmentally benign, and relatively inexpensive. Bismuth, however, is predominantly stable in only the +3- oxidation state, indicative of its limited redox activity. As a remedy, redox active dithiolene ligands may be employed. This allows the metal complex to undergo electron transfer reactions without requiring a change in the oxidation state of the metal center. The goal of this project is to synthesize two molecular arylbismuth dithiolene complexes
[ArBi(dithiolene)], electrochemically characterize their redox potential through cyclic voltammetry, and subsequently test their oxidative potential using diphenyl disulfide. Progress has been made towards the synthesis of the two target compounds [MesBi(L)] (1) and [(4-tBuC6H4)Bi(L)] (2) (L = cis-1,2-dicyano-1,2-ethylenedithiolate). By using a “onepot” synthesis, it is possible to avoid decomposition of the photo- and thermally sensitive RBiCl2 intermediates. Although the formation of both compounds has been suggested via NMR spectroscopy and FT-IR spectroscopy, further purification and characterization of both materials is required
Are disproportionate losses of eastern breeding Semipalmated Sandpipers (Calidris pusilla) driving declines in the upper Bay of Fundy, Canada?
Get PDFLarge numbers of Semipalmated Sandpipers (Calidris pusilla) use the Bay of Fundy, Canada, as a stopover site during their southbound migration from breeding to wintering grounds. The species exhibits a geographic cline in bill length on the breeding grounds (larger in east). Based on a previous analysis of morphometric traits that detected a small temporal decline in bill length, it has been suggested that observed declines in the Semipalmated Sandpiper population staging in the Bay of Fundy were driven by a disproportionate loss from the eastern breeding population. New data collected in the Bay of Fundy has made it possible to reassess this suggestion. We compared new bill length data from the Bay of Fundy (2009–2014) to historical data (1981–1989, 1997–2007) to examine temporal changes in bill length at this stopover site. We also examined count data at a major roost site from 1981 to 2014 to assess temporal changes in migratory passage. Variation in median passage date is explained best by a combination of year and Arctic climate data. Birds are now migrating through the region later in the season; median passage date has advanced approximately 5 d from 1980s values. Our analyses suggest that while there was a small decline in bill length between the 1980s and early 2000s, it has since reversed and bills are now comparable to historical values. Given this reversal in mean bill length, coupled with population estimates that are still low relative to historical values, there is now little evidence to support the hypothesis that the decline between the 1980s and today in birds passing through the Bay of Fundy is linked to disproportionate losses of eastern breeders. We therefore suggest that population declines may be distributed more broadly across the breeding range of birds that use the Bay of Fundy as a stopover site.type of work: Research Articlepublication status: Accepted for publicatio
Staying grounded: Overcoming circularity and conventionalism in MacIntyre's Virtue Ethics
Get PDFIn <i>After Virtue</i>, MacIntyre provides a novel justificatory scheme for his ethical theory - what I have come to call the Tripartite framework. However, his extended discussion in <i>Whose Justice? Which Rationality?</i> opens this framework up to multiple potentially troublesome lines of criticism, some of which he addresses and some of which he ignores. While MacIntyre addresses relativist and perspectivist critiques in <i>Whose Justice? Which Rationality?</i> (WJWR), I have noticed one concern that is left unacknowledged. On the basis of this concern, I will develop what I have called the conventionalist critique
Assessment of alternative methods for analyzing X-ray fluorescence spectra
Get PDFWhen analyzing characteristic peaks in X-ray fluorescence (XRF) spectra, the peak area is the value most often used to quantify peak size. However, some studies have reported the amplitude of the peak instead of the area. When the width of the peak is allowed to vary from trial to trial in order to provide the best possible fit to the data, these two alternative methods can yield slightly different results. In the current study, these two approaches to peak analysis are compared for data obtained from bone reference materials having certified lead concentrations of 1.09 ± 0.03 μg/g, 16.1 ± 0.3 μg/g, 13.2 ± 0.3 μg/g, and 31.5 ± 0.7 μg/g. Measurements were made with an Olympus Innov-X Delta Premium portable XRF system. Using both the area and amplitude methods, lines of best fit were constructed for the lead Lα and lead Lβ signals as a function of lead concentration. Additionally, coefficients of variation were calculated for each reference material and condition of analysis. To assess possible variations over time, the procedure was performed at two points separated by about one year. The amplitude and area methods were found to produce results which were consistent and proportional. Using either method, lead XRF signal plotted as a function of known lead concentration produced adjusted r2 values of ~0.99. The amplitude method provided slightly higher adjusted r2 values overall. Coefficients of variation were generally very similar between the two methods, although more pronounced differences emerged from measurements of the lowest concentration reference material.This work was supported by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada
Distribution and habitat use of the invasive Carcinus maenas L. (European Green Crab) and the native Cancer irroratus (Say) (Rock Crab) in intertidal zones in the Upper Bay of Fundy, Canada
Get PDFCarcinus maenas (European Green Crab) is an invasive marine portunid crab that has established populations globally outside of its native range and has been implicated in declines of benthic invertebrates in invaded ecosystems. Observations of Green Crab on intertidal mudflats in the upper Bay of Fundy have increased in recent years. We assessed the distribution and relative abundance of crab populations in Chignecto Bay, an arm of the upper Bay of Fundy, by trapping Green Crab and native Cancer irroratus (Say) (Rock Crab) at mudflats and in rocky intertidal zones in 2013 and 2014. Spatial distribution of Green Crabs indicated a preference for rocky intertidal habitats and greater abundance geographically lower in the Bay, which would correspond with an initial introduction at the mouth of the Bay and subsequent inward expansion. Abundance declined drastically from 2013 to 2014, suggesting that Green Crab may not yet be well established in Chignecto Bay. Carapace width indicated that crab age may be less variable further into the Bay, suggesting these sites may only be colonized in years with favorable environmental conditions. The population may be vulnerable under poorer conditions in other years, like 2014, when high overwintering mortality is a possible cause for the observed decline. There was not a corresponding decline in native Rock Crab. While Green Crab abundance is currently relatively low in Chignecto Bay, and their impact on mudflats likely minimal, prolonged favorable environmental conditions could lead to an increased presence.The publisher, Eagle Hill Institute, reserves the copyright to all its publications. Any reproduction, other than for an individual's own personal and private use, or distribution of journal content is prohibited without written permission from Eagle Hill Institute.
Authors of articles published in the Northeastern Naturalist are allowed to post the pdf reprints of their articles on their own website or on the website or in the repository of their affiliated institution, as well as personally distribute copies to their colleagues, provided they do so along with a clear statement of the Institute's copyright policy as stated above
Feasibility of measuring zinc in human nails using portable x-ray fluorescence
Get PDFA variety of adverse health effects have been identified as resulting from zinc deficiency. Zinc supplementation may therefore be indicated for certain individuals or populations. A rapid and straightforward means of assessing zinc status in humans would be of considerable medical benefit. In this study, the feasibility of measuring zinc levels in human fingernails or toenails using a portable x-ray fluorescence technique was assessed. Whole nail models (or phantoms) were constructed from resin, and dosed with various concentrations of zinc. These different concentration “nails” were cut into small slices of 4.4 ± 0.2 mm width. The combination of these various slices into different arrangements allowed the modeling of different time-dependent zinc exposure scenarios. A portable x-ray fluorescence device was tested using an “open beam” configuration having a beam diameter of ~9 mm, and using a “weld mask” configuration with the beam width reduced to 2.9 mm. Minimum detection limits were determined to be 0.15 ± 0.01 ppm for the open beam, and 1.13 ± 0.08 ppm when using the weld mask. By scanning across the length of the model nails, it was demonstrated that differences in zinc levels deposited over time could be detected, and that the weld mask configuration was better suited to resolving spatial changes. The x-ray fluorescence approach was found to be highly sensitive for detecting zinc in nail, and capable of differentiating patterns of zinc uptake over time.This work was supported by a Discovery Grant (261523) from the Natural Sciences and Engineering Research Council of Canada.This is an accepted manuscript made available under a CC BY-NC-ND license. The published journal article is available at https://doi.org/10.1016/j.jtemb.2018.04.02