Alternating Signed Bipartite Graphs and Difference-1 Colourings

We investigate a class of 2-edge coloured bipartite graphs known as alternating signed bipartite graphs (ASBGs) that encode the information in alternating sign matrices. The central question is when a given bipartite graph admits an ASBG-colouring; a 2-edge colouring such that the resulting graph is an ASBG. We introduce the concept of a difference-1 colouring, a relaxation of the concept of an ASBG-colouring, and present a set of necessary and sufficient conditions for when a graph admits a difference-1 colouring. The relationship between distinct difference-1 colourings of a particular graph is characterised, and some classes of graphs for which all difference-1 colourings are ASBG-colourings are identified. One key step is Theorem 3.4.6, which generalises Hall's Matching Theorem by describing a necessary and sufficient condition for the existence of a subgraph $H$ of a bipartite graph in which each vertex $v$ of $H$ has some prescribed degree $r(v)$

Controls on Fluvial Geomorphology in the Canadian Rocky Mountains

The Canadian Rocky Mountains record a dynamic history of erosion. Presently, bedrock rivers interact with the lithology and structural architecture of a large fold-and-thrust belt. Because the alpine landscape has been modified by Pleistocene and Holocene glaciation, rivers are also influenced by relict glacial landscape features. Here, we use topographic analysis and rock erodibility data to test the impact of lithology and glacial influence on fluvial form and incision potential in the headwaters of the Athabasca River Watershed. For 30 streams, we identify spikes in normalized channel steepness (ksn) where fluvial incision is focused. Results show that proximity to major lithologic contacts is not a predictor of knickzone location. Instead, bedrock channels are most perturbed from equilibrium where they flow over convexities at the intersection between hanging valleys and mainstem valley walls. These results suggest that glacial imprinting--mediated by variations in bedrock geology--controls Holocene erosion in this region.Master of Scienc

How to Host a Data Competition: Statistical Advice for Design and Analysis of a Data Competition

Data competitions rely on real-time leaderboards to rank competitor entries and stimulate algorithm improvement. While such competitions have become quite popular and prevalent, particularly in supervised learning formats, their implementations by the host are highly variable. Without careful planning, a supervised learning competition is vulnerable to overfitting, where the winning solutions are so closely tuned to the particular set of provided data that they cannot generalize to the underlying problem of interest to the host. This paper outlines some important considerations for strategically designing relevant and informative data sets to maximize the learning outcome from hosting a competition based on our experience. It also describes a post-competition analysis that enables robust and efficient assessment of the strengths and weaknesses of solutions from different competitors, as well as greater understanding of the regions of the input space that are well-solved. The post-competition analysis, which complements the leaderboard, uses exploratory data analysis and generalized linear models (GLMs). The GLMs not only expand the range of results we can explore, they also provide more detailed analysis of individual sub-questions including similarities and differences between algorithms across different types of scenarios, universally easy or hard regions of the input space, and different learning objectives. When coupled with a strategically planned data generation approach, the methods provide richer and more informative summaries to enhance the interpretation of results beyond just the rankings on the leaderboard. The methods are illustrated with a recently completed competition to evaluate algorithms capable of detecting, identifying, and locating radioactive materials in an urban environment.Comment: 36 page

Where Would You Turn For Help? Older Adults’ Knowledge and Awareness of Community Support Services

Community support services (CSSs) enable persons coping with health or social problems to maintain the highest possible level of social functioning and quality of life. Access to these services is challenging because of the multiplicity of small agencies providing these services and the lack of a central access point. A review of the literature revealed that most service awareness studies are marred by acquiescence bias. To address this issue, service providers developed a series of 12 vignettes to describe common situations faced by older adults for which CSSs might be appropriate. In a telephone interview, 1152 older adults were presented with a series of vignettes and asked what they would do in that situation. They were also asked about their most important sources of information about CSSs. Findings show awareness of CSSs varied by the situation described and ranged from a low of 1% to 41%. The most important sources of information about CSSs included informational and referral sources, the telephone book, doctor’s offices, and through word of mouth.Community Support Services, awareness, knowledge, acquiencence bias, vignette methodology

Where Would You Turn For Help? Older Adults’ Knowledge and Awareness of Community Support Services

Community support services (CSSs) enable persons coping with health or social problems to maintain the highest possible level of social functioning and quality of life. Access to these services is challenging because of the multiplicity of small agencies providing these services and the lack of a central access point. A review of the literature revealed that most service awareness studies are marred by acquiescence bias. To address this issue, service providers developed a series of 12 vignettes to describe common situations faced by older adults for which CSSs might be appropriate. In a telephone interview, 1152 older adults were presented with a series of vignettes and asked what they would do in that situation. They were also asked about their most important sources of information about CSSs. Findings show awareness of CSSs varied by the situation described and ranged from a low of 1% to 41%. The most important sources of information about CSSs included informational and referral sources, the telephone book, doctor’s offices, and through word of mouth.Community Support Services, awareness, knowledge, acquiencence bias, vignette methodology

Where Would You Turn for Help? Older Adults’ Awareness of Community Support Services

Previous findings on older adults’ awareness of community support services (CSSs) have been inconsistent and marred by acquiescence or over-claiming bias. To address this issue, this study used a series of 12 vignettes to describe common situations faced by older adults for which CSSs might be appropriate. In telephone interviews, 1,152 adults aged 50 years and over were read a series of vignettes and asked if they were able to identify a community organization or agency that they may turn to in that situation. They were also asked about their most important sources of information about CSSs. The findings show that, using a vignette methodology, awareness of CSSs is much lower than previously thought. The most important sources of information about CSSs included information and referral sources, the telephone book, doctors’ offices, and word of mouth.aging, community support services, awareness, knowledge, acquiescence bias, vignette methodology

Where Would You Turn for Help? Older Adults’ Awareness of Community Health and Support Services for Dementia Care

Previous findings on older adults’ awareness of community support services (CSSs) have been inconsistent and marred by acquiescence or over-claiming bias. To address this issue, this study used a series of 12 vignettes to describe common situations faced by older adults for which CSSs might be appropriate. In telephone interviews, 1,152 adults aged 50 years and over were read a series of vignettes and asked if they were able to identify a community organization or agency that they may turn to in that situation. They were also asked about their most important sources of information about CSSs. The findings show that, using a vignette methodology, awareness of CSSs is much lower than previously thought. The most important sources of information about CSSs included information and referral sources, the telephone book, doctors’ offices, and word of mouth.aging, community support services, awareness, knowledge, acquiescence bias, vignette methodology

Binary Interval Search (BITS): A Scalable Algorithm for Counting Interval Intersections

Motivation: The comparison of diverse genomic datasets is fundamental to understanding genome biology. Researchers must explore many large datasets of genome intervals (e.g., genes, sequence alignments) to place their experimental results in a broader context and to make new discoveries. Relationships between genomic datasets are typically measured by identifying intervals that intersect: that is, they overlap and thus share a common genome interval. Given the continued advances in DNA sequencing technologies, efficient methods for measuring statistically significant relationships between many sets of genomic features is crucial for future discovery. Results: We introduce the Binary Interval Search (BITS) algorithm, a novel and scalable approach to interval set intersection. We demonstrate that BITS outperforms existing methods at counting interval intersections. Moreover, we show that BITS is intrinsically suited to parallel computing architectures such as Graphics Processing Units (GPUs) by illustrating its utility for efficient Monte-Carlo simulations measuring the significance of relationships between sets of genomic intervals