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    Vector bundles on toric stacks
    (University of Waterloo, 2026-06-04) Singh, Yash Vardhan
    This thesis is concerned with a generalization of Klyachko's classification of toric vector bundles to toric stacks. The work of Klyachko gave an elegant method of studying toric vector bundles through filtrations of a vector space. We extend these techniques to vector bundles on a toric stack and generalize the aspects of Klyachko's work to a more geometric setting. In particular, we show that the category of reflexive sheaves on a toric stack is equivalent to a category of filtered reflexives sheaves of its largest Deligne-Mumford substack. We then combine this with an equivariant version of Gubeladze's result on the splitting of vector bundles on toric varieties to prove a classification theorem for vector bundles on toric stacks. As an application we reprove a known result on the splitting of rank-$2$ bundles on $[\bP^n/\bG_m]$ for a particular $\bG_m$ action. Our methods involve an extension of Cox's construction of homogeneous coordinates to toric stacks and we incorporate ideas from the classical Rees construction. We also study the Chow ring of toric stacks, and give a presentation of the Chow ring of a smooth toric stack.
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    Information Extraction for Low-Resource Schemas
    (University of Waterloo, 2026-06-04) Xu, Justin
    Information Extraction (IE) is a set of important tasks in the study of creating structured data such as knowledge graphs from unstructured data such as text. The past paradigm of IE focused on models with specialized neural network architectures, usually based on transformer encoders. These models typically focus on a single subtask of IE, following a single schema of entity and relation types, and are trained via supervised learning on large datasets of annotated texts. Meanwhile, the current paradigm of IE, called Universal IE (UIE), involves large language models which can generalize across IE subtasks and to completely unseen schemas, but which lack other abilities such as entity grounding and calibration. We first discuss structural consistency, a new measure of robustness in information extraction based on compositionality. We present structural consistency post-training (SCPT) as a data augmentation method to boost structural consistency for a wide range of model architectures. Besides greatly improving robustness, SCPT significantly reduces the amount of labelled data needed to achieve the same level of performance when training specialized IE models. Second, we use reasoning-based data augmentation techniques to gather AdaIE, a very large collection of human-annotated information extraction schemas. We diverge from UIE and align the dataset with a new task we call Guided Information Extraction (GIE). GIE emphasizes the tight grounding and schema-following requirements which have been largely neglected in UIE. Evaluations of state-of-the-art UIE models reveal that state of the art UIE methods can be surpassed by recent commercial large language models (LLMs). Although those LLMs achieve below human performance on AdaIE, they are rapidly advancing. Overall, we hope that both works presented will steer the IE research community towards unifying the strengths of the old and new IE paradigms, while casting light on their weaknesses.
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    Patterns and predictors of smokeless tobacco use among adults in Bangladesh: Findings from the International Tobacco Control (ITC) Bangladesh survey
    (Public Library of Science, 2014-07-09) Abdullah, Abu S.; Driezen, Pete; Ruthbah, Ummul H.; Nargis, Nigar; Quah, Anne C. K.; Fong, Geoffrey T.
    Background Although smokeless tobacco (SLT) use is prevalent in South Asian countries including Bangladesh, information about the pattern and correlates of SLT use is scarce. This study described the pattern and predictors of SLT use among Bangladeshi adults. Methods The data for this study were derived from the International Tobacco Control Policy Evaluation Bangladesh (ITC BD) Survey, a prospective cohort survey of a nationally representative sample of smokers and non-smokers, conducted during November 2011 and May 2012. The study included 5522 adults aged 15 or above. We used multiple logistic regression models to identify predictors of SLT use. Results Of the respondents (N = 5522), 20% were SLT users. In general, SLT use was significantly higher among women, the illiterate and residents of the Dhaka slums or non-tribal/non-border areas outside Dhaka; SLT use increased with age. Several attitudinal factors were also associated with SLT use. Multivariable logistic regression analyses revealed several predictors of SLT use: being female (OR = 1.96, 95% confidence interval, CI: 1.18–3.24), an increasing age, being a resident of a Dhaka slum (OR = 5.86; 95% CI: 3.73–9.21) or non-tribal/non-border areas outside Dhaka (OR = 3.42; 95% CI: 1.94–6.03), being illiterate (OR = 3.37; 95% CI: 1.99–5.71), holding positive opinion towards societal approval of SLT use (OR = 5.84; 95% CI: 3.38–10.09), holding positive opinion towards SLT use by women (OR = 2.63; 95% CI: 1.53–4.54), believing that SLT is addictive (OR = 2.96; 95% CI: 1.51–5.81), and believing SLT is less harmful than bidi (OR = 2.22; 95% CI: 1.36–3.62). Conclusion The findings suggest that coordinated efforts of governmental and non-governmental organizations, targeting both smoked tobacco and SLT use reduction and cessation, could be modified to reach each level of population including those who are marginalized, female, less educated and elderly. As most tobacco control programs in Bangladesh target mainly cigarette or bidi smoking, coordinated programs are needed that will also include SLT use within the tobacco control policy and prevention strategies.
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    Gd^3+ and calcium sensitive, sodium leak currents are features of weak membrane-glass seals in path clamp recordings
    (Public Library of Science, 2014-06-19) Boone, Adrienne N.; Senatore, Adriano; Chemin, Jean; Monteil, Arnaud; Spafford, J. David
    The properties of leaky patch currents in whole cell recording of HEK-293T cells were examined as a means to separate these control currents from expressed sodium and calcium leak channel currents from snail NALCN leak channels possessing both sodium (EKEE) and calcium (EEEE) selectivity filters. Leak currents were generated by the weakening of gigaohm patch seals by artificial membrane rupture using the ZAP function on the patch clamp amplifier. Surprisingly, we found that leak currents generated from the weakened membrane/glass seal can be surprisingly stable and exhibit behavior that is consistent with a sodium leak current derived from an expressible channel. Leaky patch currents differing by 10 fold in size were similarly reduced in size when external sodium ions were replaced with the large monovalent ion NMDG+. Leaky patch currents increased when external Ca2+ (1.2 mM) was lowered to 0.1 mM and were inhibited (>40% to >90%) with 10 µM Gd3+, 100 µM La3+, 1 mM Co2+ or 1 mM Cd2+. Leaky patch currents were relatively insensitive (<30%) to 1 mM Ni2+ and exhibited a variable amount of block with 1 mM verapamil and were insensitive to 100 µM mibefradil or 100 µM nifedipine. We hypothesize that the rapid changes in leak current size in response to changing external cations or drugs relates to their influences on the membrane seal adherence and the electro-osmotic flow of mobile cations channeling in crevices of a particular pore size in the interface between the negatively charged patch electrode and the lipid membrane. Observed sodium leak conductance currents in weak patch seals are reproducible between the electrode glass interface with cell membranes, artificial lipid or Sylgard rubber.
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    The public and professionals reason similarly about the management of non-native invasive species: A quantitative investigation of the relationship between beliefs and attitudes
    (Public Library of Science, 2014-08-29) Fischer, Anke; Selge, Sebastian; van der Wal, Rene; Larson, Brendon M. H.
    Despite continued critique of the idea of clear boundaries between scientific and lay knowledge, the ‘deficit-model’ of public understanding of ecological issues still seems prevalent in discourses of biodiversity management. Prominent invasion biologists, for example, still argue that citizens need to be educated so that they accept scientists’ views on the management of non-native invasive species. We conducted a questionnaire-based survey with members of the public and professionals in invasive species management (n = 732) in Canada and the UK to investigate commonalities and differences in their perceptions of species and, more importantly, how these perceptions were connected to attitudes towards species management. Both native and non-native mammal and tree species were included. Professionals tended to have more extreme views than the public, especially in relation to nativeness and abundance of a species. In both groups, species that were perceived to be more abundant, non-native, unattractive or harmful to nature and the economy were more likely to be regarded as in need of management. While perceptions of species and attitudes towards management thus often differed between public and professionals, these perceptions were linked to attitudes in very similar ways across the two groups. This suggests that ways of reasoning about invasive species employed by professionals and the public might be more compatible with each other than commonly thought. We recommend that managers and local people engage in open discussion about each other’s beliefs and attitudes prior to an invasive species control programme. This could ultimately reduce conflict over invasive species control.