30921 research outputs found
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Zombies and survivors on graph classes
No full textZombies and Survivors is a two-player graph game introduced by Fitzpatrick et al. as a variant of Cops and Robbers. These games can be used to model situations involving pursuit-evasion or search-and-rescue. Two players take turns to move their pieces in a given graph, with the condition that the zombie pieces must move toward the survivor along a shortest path during the zombie player’s turn. The minimum number of zombies that is sufficient to catch the survivor is called the graph's zombie number.
First, we give a construction of graphs with zombie number equal to any given k, and extend the result to a construction of graphs that simultaneously have zombie number equal to any given k and cop number equal to any given m. Then, we investigate specific graph classes. We determine the exact zombie number of the Cartesian product of a cycle and a path, and show that this quantity depends on the parity of the cycle. Upper bounds on the zombie number for strong products, Cartesian products and lexicographic products are given. We also show that the throttling numbers of Cartesian products and strong products of two paths are asymptotic to a sublinear polynomial in the length of the path. Finally, the class of graphs formed by a set of cycles with one common center vertex is investigated, and we give a characterization of such graphs that have zombie number 1 or 2.May 202
Arthropod Diversity Within The Three Sisters Cropping System
No full textThe Three Sisters is an indigenous cropping method that dates back hundreds of years. It is comprised of the simultaneous planting of corn, bean, squash, and sometimes sunflower. However, there has been no published research into arthropod communities and interactions with this cropping system. My study examined arthropod abundance and taxa to the family level at three areas: uncultivated, fields planted with The Three Sisters, and field edges. This was done at three sites in Manitoba: Ian N. Morrison Research Farm near Carman, Glenlea Research Station near Glenlea, and Brokenhead Ojibway First Nations Reserve. I placed 8 sticky cards within each area at each site starting in July 2023, and had 4 bi-weekly sampling rounds. The number of samples collected and processed was 288. I conducted a perMANOVA test, and ran multiple negative binomial generalized linear mixed models, testing the abundance and number of taxa present in relation to the site, area type, date, colour, and using trap number as a random effect. All sites were significantly different from each other. Glenlea had the highest diversity, and Carman had the least diversity. The uncultivated areas differed from both the field and edge areas, and the fields and edges also differed from each other at all sites. The field and edges had higher diversity than the uncultivated areas. The most important finding of my study was that The Three Sisters is an agricultural method that can allow for higher diversity of arthropods than uncultivated areas
Response of soil fungal communities associated with different soil fractions to tillage practices and crop rotation
No full textThis thesis investigates the effects of agricultural practices on soil microbial communities, with a specific focus on understanding how different tillage practices and crop rotation impact soil fungal communities within the distinct soil fractions. A two consecutive year study (2021 and 2022) was conducted in three fields located in Manitoba, Canada, each undergoing a different phase a crop rotation cycle that included corn, canola, and soybean. Additionally, the research examined multiple tillage practices that included conventional tillage, deep tillage, vertical tillage, and raised bed practice. To comprehensively assess soil fungal microbial communities, next-generation sequencing of the internal transcribed spacer region within nuclear ribosomal DNA was employed. Our study confirmed that tillage practices and crop rotation shape the structure of the soil fungal communities within the different soil fractions. In both years, Ascomycota and Basidiomycota were recognized as the prevailing fungal phyla in all tillage practices and crop rotations. These two phyla are widely recognized as the primary classical fungal decomposers and pathotrophs in soils. Furthermore, while tillage practices did not exert a significant impact on soil fungal alpha diversity, the highest predicted average fungal richness, as measured by Observed, Shannon, and Simpson alpha diversity indices, was associated with vertical tillage in 2021 and conventional tillage in 2022. Moreover, there was a significant difference in soil fungal alpha diversity among plots within different fields in 2021. Predictions based on both Shannon and Simpson indices indicated that plots in soybean in 2021 and plots in corn in 2022 were anticipated to exhibit the highest average fungal richness. We also noted a significant difference in soil fungal alpha diversity among different soil fractions in both years of our study. The relative abundance of numerous amplicon sequence variants exhibited significant difference in response to both tillage practices and crop rotation. Specifically, soils subjected to conventional tillage practices demonstrated a significantly lower relative abundance of plant pathogens within the phylum Ascomycota and a higher relative abundance of saprotrophic fungi. Our investigation further revealed that the relative abundance of beneficial soil fungi, particularly arbuscular mycorrhizal fungi, was higher in soils under the vertical tillage practice. In plots within the corn field, we also noted a markedly higher relative abundance of arbuscular mycorrhizal fungi. Conversely, plots within canola fields exhibited a higher relative abundance of saprotrophic fungi, including members of the phyla Ascomycota, Basidiomycota, and Mortierellomycota. Our results suggest that tillage and crop rotation influence soil fungal community distribution. This study provides insights into the intricate relationships between agricultural practices and soil fungal communities, shedding light on the dynamics of these critical components of agricultural ecosystems in Manitoba.February 202
Doxycycline vs azithromycin in patients with scrub typhus: a systematic review of literature and meta-analysis
No full textIntroduction
Scrub typhus is a bacterial mite-borne disease associated with poor clinical outcomes if not treated adequately. The study aimed to compare the time to defervescence, clinical failure, mortality and treatment-related adverse effects of two common drugs (doxycycline and azithromycin) used for its treatment.
Methodology
This was a systematic review and meta-analysis. All studies up to 20.03.2023 were screened for eligibility in Pubmed and Embase using a search string containing terms related to scrub typhus, doxycycline and azithromycin. After two phases of screening, all comparative studies where doxycycline and azithromycin were used to treat scrub typhus were included. The studies were critically appraised using standardised tools, and a meta-analysis was performed for time to defervescence (primary outcome), clinical failure, mortality and treatment-related adverse effects.
Results
Of 744 articles from two databases, ten were included in the meta-analysis. All but two studies had a high risk of bias. The meta-analysis for time to defervescence had a high heterogeneity and did not show any significant difference between doxycycline and azithromycin arms [Mean difference of -3.37 hours (95%CI: -10.31 to 3.57), p=0.34]. When the analysis was restricted to studies that included only severe scrub typhus, doxycycline was found to have a shorter time to defervescence [mean difference of -10.15 (95%CI: -19.83 to -0.46) hours, p=0.04]. Additionally, there was no difference between the two arms concerning clinical failure, mortality and treatment-related adverse effects.
Conclusion
The current data from studies with a high risk of bias did not find statistically significant differences in clinical outcomes between doxycycline and azithromycin for scrub typhu
Transcriptomic, small RNA, and epigenetic atlas of the Brassica napus seed
No full textThe diversification of flowering plants has been described as the “abominable mystery” of evolutionary biology for decades. Angiosperms diversified at unprecedented rates in the early Cretaceous, rapidly occupying new niches and pervading much of the earth’s terrestrial landscape. This speciation was accompanied by dramatic genome evolution as well — more than 75% of extant angiosperm species are believed to have originated from genome duplication events. These duplications are most often in the form of endogenous chromosomal duplication (autopolyploidy) or, more frequently, via interspecific hybridization (allopolyploidy). Consequently, dynamics of polyploidy within flowering plants are of interest to the fields of plant genetics and evolution. One of the world’s most important oilseeds is Brassica napus L. (“canola”), an allopolyploid species derived from two progenitors (B. rapa and B. oleracea). B. napus has two relatively complete diploid genomes from each progenitor, but also shares a whole genome triplication (autopolyploidization) with the rest of the Brassicaceae. These factors constitute B. napus as an informative model to study the consequences of polyploidization. Within this thesis, I describe the transcriptional and epigenetic profiles throughout B. napus seed development. Therein, I utilize laser microdissection, histological analysis, and bioinformatic tools to describe the transcriptional profiles of the seed. The subgenomes constituting B. napus contribute to gene expression within the seed asymmetrically, with many homlogs being more expressed in one subgenome than the other. Additionally, I provide evidence for striking differences in epigenetic structure of the fractionated genomes depending on genomic context. The works detailed within this thesis serve to explain the transcriptional landscapes of the B. napus seed, particularly through the lens of polyploidy, and the exceptional complexity of angiosperm genomes.May 202
Incidence of gasoline taxes in Canada: an event study approach to estimating pass-through
No full textThis study investigates the city-level pass-through rates of provincial and carbon tax changes on wholesale and retail gasoline prices in Canada from 1998 to 2024. Focusing on tax increases and decreases, the analysis measures pass-through rates to explore the impact of tax policies on gasoline prices across Canada. This study also analyses the tax incidence of medium/small cities and large cities separately to examine regional pass-through rates. Data is collected from Kent Marketing Ltd and Statistics Canada to create panel datasets for an event-based difference-in-difference model. Event plots show an immediate response in retail gasoline prices following tax changes; however, retail prices begin to adjust even before the implementation of tax policies. The estimated pass-through rate of gasoline tax increases on retail prices is 100% in the 9-week window and 88% in the 17-week window. For tax decreases, the pass-through rates are even higher, at 120% in the 9-week window and 140% in the 17-week window. The analysis also reveals the significant impact of tax changes on retail prices in medium/small cities and large cities. However, the study finds that the impact of gasoline tax changes on wholesale prices is statistically insignificant for both the 9-week and 17-week windows. Additionally, results from the 9-week window gasoline tax analysis without fixed effects and covariates are insignificant, underscoring the importance of accounting for these factors. In conclusion, the findings of this study emphasize the crucial role of provincial and carbon tax policies in shaping retail gasoline prices, while highlighting the limited impact on wholesale prices in Canada.February 202
Remediation of aquaculture wastewater using wetland plants
No full textThe aquaculture industry is among the fastest growing food production sectors globally. Land-based aquaculture operations discharge aquaculture wastewater (AWW) high in nitrogen and phosphorus, which require effective management to mitigate environmental impacts. Constructed wetlands (CWs) are treatment technologies used for the remediation of nutrient-rich wastewaters, while nitrogenous wastes like ammonia and urea in AWW are viable fertilizers for biomass production in flooded soils. This research involved a series of four studies evaluating the performance of CW systems treating AWW. Model CW systems were constructed in mesocosms (~1500 L of water) and had a gradient of nutrient loading treatments applied through repeated AWW additions. In the first study, cattail (Typha spp.) CWs achieved >95% total phosphorus (TP) removal from water within 33 days of treatment, although elevations of TP (>0.2 mg L-1) occurred for 3–4 weeks under TP loadings of 1.02–1.64 mg m-2 d-1. The second, third, and fourth studies utilized CWs planted with northern wild rice (Zizania palustris L.) and emulated established wetlands, managed natural stands, and flooded paddies, respectively. In the second study, TP concentrations increased to >0.25 mg L-1 under TP loadings of 4.66–9.25 mg m-2 d-1, whereas biofilm growth dominated at 14.46 mg m-2 d-1 and resulted in the removal of TP from the water column. In the third study, low wild rice biomass resulted in fewer plant nutrient sinks, facilitating algal growth. The fourth study achieved a 70% TP reduction in CW water within the first 27 days. However, among higher TP loadings (>54.63 mg m-2 d-1), water quality degradations occurred throughout the subsequent 42 days. Wild rice biomass in flooded paddies contributed to ~3.8 g m-2 of phosphorus uptake over 90 days. These findings provide insights into the operational timelines of cattail and wild rice CW systems treating AWW. The discharge of CW effluents should be coordinated with periods of low TP concentrations. Further assessments could evaluate the effectiveness of various fertilizer regimes, explore strategies for optimizing different biomass production systems, and investigate the practical integration of agronomy systems into a circular economy model.February 202
Cognitive control and emotion regulation: effort, efficacy, and choice
No full textRegulating our emotions in an adaptive way is important for our well-being and social relationships and is thought to be related to cognitive control, which is our ability to act in a goal-directed manner. For instance, the dual mechanisms of control (DMC) framework is proposed as one way to categorize and understand emotion regulation. This research aimed at discerning differences in emotion regulation efficacy and choice through the two modes of cognitive control in the DMC framework. Two experiments were conducted to test the hypotheses that emotion regulation is more effective in proactive contexts compared to reactive contexts overall, and that individuals will choose to use certain emotion regulation strategies more when they are in a proactive context compared to reactive and others in reactive versus proactive. Understanding the temporal dynamics of emotion regulation will benefit the scientific community, in terms of elucidating the theoretical mechanisms underlying emotion regulation, and potentially help inform therapeutic interventions for individuals with emotion regulation difficulties. Experiment 1 demonstrated some evidence suggesting emotion regulation is more effective in proactive conditions but did not provide support for our interaction hypotheses regarding specific strategies in proactive versus reactive contexts. Experiment 2 did not replicate the effect of proactive emotion regulation being better than reactive emotion regulation, and further suggested that strategy choice was not influenced by proactive versus reactive contexts. I discuss the implications of my results, limitations of the current study, and provide suggestions for future research.University of Manitoba Department of PsychologyOctober 202
What if the sun didn't rise: a photographic research creation on light, color and time
No full textThis thesis presents the results of the research that led to the exhibition What if the Sun Didn't Rise, presented at the School of Art Gallery of the University of Manitoba from May 17 to June 21, 2024. Drawing on sociological research on the social acceleration of contemporary societies, my research-creation led me to reduce the photographic medium in such a way as to challenge current photographic norms in relation to the multiplication of images and the installation of images in a white cube, proposing a space of resonance fostered by slowing down and an unusual phenomenological engagement. The work seeks to revisit the landscape photography tradition by the use of cameraless techniques where the landscape creates the photograph, rather than is photographed. The work of art is in dialogue with the history of photography, but also with the history of painting with an esthetic that tends toward the concept of sublime, as it was experienced in romanticist paintings aesthetic (Friedrich, Turner) and abstract expressionism (Rothko).
What If the Sun Didn't Rise traces the evolution of the desire to slow down and deepen my relationship with the world. By simply using sheets of photosensitive paper layered with natural plant material and exposing them to sunlight and the elements for extended hours, I develop a long-form conversation with the environment in which I find myself. This process contrasts sharply with the rapid consumption and multiplication of digital imagery, advocating for a more contemplative, sustained engagement with our surroundings. In that mindset, I produced a durational video installation in which I present the brief hours of sunshine in my studio while it quietly transform the colours of a photosensitive paper laid over a photograph of the Winnipeg sky.
By addressing those questions and offering a space to slow down, this minimalistic exhibition seeks to offer viewers a potential of resonance, whether directly in relation to the work or in everyday moments, like the sight of a ray of sunshine.October 202
Improving calibration and multi-frequency inversion in microwave imaging with machine learning
No full textThis thesis explores two unique ways of using machine learning to improve or facili-
tate microwave imaging. The first contribution provides a means of calibration under
the assumption of an uncooperative imaging system, a term indicating that it is im-
possible or impractical to have any control over the region of interest, which means
no known targets are available for calibration. The approach uses a method of style
transfer provided by Cycle Generative Adversarial Networks. Cycle Generative Ad-
versarial Networks are capable of learning arbitrary transformations between two sets
of data in which there exists no paired samples across the two domains. In the case
of calibration the two domains are synthetic field data and raw S-parameters from
a physical imaging setup. The method is shown to be nearly as good as calibration
with a known target for a 2D TM experimental imaging setup.
The second contribution of this thesis focuses on how multi-frequency data should
best be used in a machine learning model to solve the inverse problem. This work
introduces two novel architectures capable of using multi-frequency data and testing
the results on experimental data. The first method uses a system of sequential U-
Nets referred to as the cascaded multi-frequency approach. This method turned out
to be very similar to a recurrent neural network which inspired the creation of a novel
LSTM-like architecture - the second method. These two methods were compared
i
to single frequency inversions and a ‘naive’ multi-frequency inversion which collapse
the frequency data into the channels of the single frequency inversion. The models
were tested on the same 2D TM experimental imaging setup in which labeled data
was acquired through an automated target positioning system. Both multi-frequency
approaches show significant improvement over the single frequency counter part and
the naive approach.October 202