Model Theoretic Complexity of Automatic Structures

We study the complexity of automatic structures via well-established concepts from both logic and model theory, including ordinal heights (of well-founded relations), Scott ranks of structures, and Cantor-Bendixson ranks (of trees). We prove the following results: 1) The ordinal height of any automatic well- founded partial order is bounded by \omega^\omega ; 2) The ordinal heights of automatic well-founded relations are unbounded below the first non-computable ordinal; 3) For any computable ordinal there is an automatic structure of Scott rank at least that ordinal. Moreover, there are automatic structures of Scott rank the first non-computable ordinal and its successor; 4) For any computable ordinal, there is an automatic successor tree of Cantor-Bendixson rank that ordinal.Comment: 23 pages. Extended abstract appeared in Proceedings of TAMC '08, LNCS 4978 pp 514-52

Dopaminergic modulation of discounting of delayed punishment

Effective decision-making involves careful consideration of all potential positive and negative outcomes. Importantly, negative outcomes often occur later in time, leading to underestimation, or “discounting,” of these consequences. The Delayed Punishment Decision-making Task (DPDT) was developed to study sensitivity to delayed vs immediate punishment during cost/benefit decision-making in rats. Rats choose between two levers, one resulting in a small, single-pellet reward with no foot shock punishment, and the other resulting in a larger, three-pellet reward followed by a mild foot shock punishment. This punishment is preceded by a systematically increasing delay as the blocks progress (0, 4, 8, 12, 16 s). DPDT revealed that rats choose the punished option more as the delay in punishment increases, which is indicative of discounting of delayed punishment. Here, we examined the effects of systemic administration of catecholaminergic drugs on sensitivity to delayed punishment discounting in male and female adult rats. We found that acute cocaine did not affect choice of rewards with immediate punishment but caused a dose-dependent reduction in choice of delayed punishment. Interestingly, this effect was more prominent in females than males. Neither activation nor blockade of the D1 dopamine receptor affected decision-making. Finally, activation, but not blockade, of the D2 dopamine receptor eliminated the discounting of delayed punishment. Overall, these data demonstrate that dopamine transmission differently modulate sensitivity to delayed vs. immediate punishment

(Un)Decidability Results for Word Equations with Length and Regular Expression Constraints

We prove several decidability and undecidability results for the satisfiability and validity problems for languages that can express solutions to word equations with length constraints. The atomic formulas over this language are equality over string terms (word equations), linear inequality over the length function (length constraints), and membership in regular sets. These questions are important in logic, program analysis, and formal verification. Variants of these questions have been studied for many decades by mathematicians. More recently, practical satisfiability procedures (aka SMT solvers) for these formulas have become increasingly important in the context of security analysis for string-manipulating programs such as web applications. We prove three main theorems. First, we give a new proof of undecidability for the validity problem for the set of sentences written as a forall-exists quantifier alternation applied to positive word equations. A corollary of this undecidability result is that this set is undecidable even with sentences with at most two occurrences of a string variable. Second, we consider Boolean combinations of quantifier-free formulas constructed out of word equations and length constraints. We show that if word equations can be converted to a solved form, a form relevant in practice, then the satisfiability problem for Boolean combinations of word equations and length constraints is decidable. Third, we show that the satisfiability problem for quantifier-free formulas over word equations in regular solved form, length constraints, and the membership predicate over regular expressions is also decidable.Comment: Invited Paper at ADDCT Workshop 2013 (co-located with CADE 2013

Exploring the Standard of Review of Transactions with Controlling Shareholders After In Re MFW Shareholders Litigation (Decided May 29th, 2013)

This Article will begin with a review of the MFW case, followed by a review of the judicial history prior to this decision. Then it will try to analyze, albeit partially, some of the reasons for why this judgment is timely and reasonable considering changes that occurred in the last decades. It will also address some of the courts\u27 reasoning and its persuasiveness

A Regional Approach to Drinking Water Management: NL-BC Comparative Water Systems Study

Water is recognized as a basic human right, a critical service, a fundamental for sustainability, and a building block for resilience. In Canada, rural areas face unique challenges when it comes to drinking water management (e.g., multi-use watersheds, low population density, lack of economies of scale). Not only are these challenges in the present, but these unique issues are also important in terms of future adaptation and can act as barriers to future community and regional resilience. Research indicates that while managing drinking water is a critical issue for rural Canada, current management approaches appear to be ill equipped to address this issue, particularly in the context of regional resilience. In this report we propose a new approach to managing drinking water, using the regional scale and incorporating best practices related to regional development, new regionalism, regional resilience, water management, and sustainable infrastructure

“Social Justice Needs to Be Everywhere”: Imagining the Future of Anti-Oppression Education in Teacher Preparation

This article analyzes a social-justice teacher education project in a larger teacher education program in Western Canada. This program-within-a-program took an anti-oppressive education approach designed to help teacher candidates to understand and challenge various forms of inequity and their interconnections. We review the social justice project first, through a descriptive analysis of our teaching, and second, through hour-long qualitative, semistructured interviews with 20 graduates of our program (all beginning teachers). Our alumni provided examples of teaching against the grain and also spoke to the challenges of implementing critical pedagogies. We conclude by providing four key recommendations and reflecting on the implications for future teacher preparation.Cet article analyse un projet de justice sociale dans le cadre d’un important programme de formation des enseignants dans l’Ouest canadien. Ce « programme à l’intérieur d’un programme » a adopté une approche pédagogique contre l’oppression, conçue pour aider les étudiants en pédagogie à comprendre et à remettre en question diverses formes d’iniquité et les liens entre elles. Nous nous penchons sur le programme de justice sociale, d’abord par une analyse descriptive de notre enseignement, ensuite par des entrevues qualitatives et semi-structurées d’une heure auprès de finissants de notre programme (tous débutant leur carrière d’enseignant). Nos anciens ont fourni des exemples d’enseignement à contre-courant et ont évoqué les défis liés à la mise en oeuvre de pédagogies critiques. Nous concluons en présentant quatre recommandations clés et en réfléchissant aux conséquences pour la formation des enseignants à l’avenir

Unary automatic graphs: an algorithmic perspective

This paper studies infinite graphs produced from a natural unfolding operation applied to finite graphs. Graphs produced via such operations are of finite degree and can be described by finite automata over the unary alphabet. We investigate algorithmic properties of such unfolded graphs given their finite presentations. In particular, we ask whether a given node belongs to an infinite component, whether two given nodes in the graph are reachable from one another, and whether the graph is connected. We give polynomial time algorithms for each of these questions. Hence, we improve on previous work, in which nonelementary or non-uniform algorithms were foun