Concordia University

About: Concordia University is a education organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Context (language use) & Control theory. The organization has 13565 authors who have published 31084 publications receiving 783525 citations. The organization is also known as: Sir George Williams University & Loyola College, Montreal.

The effects of chronic antidepressant treatment in an animal model of anxiety.

Abstract: We have examined the anxiolytic activity of acute and chronic antidepressant treatment in an animal model of anxiety involving novelty-suppressed feeding. Rats were food deprived for 48 h, placed into a novel environment containing food, and the latency to begin eating was recorded. Chronic (21 days), but not acute injections of desipramine (DMI; 10 mg/kg) and amitriptyline (AMI; 10 mg/kg) significantly reduced the latency to begin eating compared to controls, but the percentage decrease was not as great as that seen with either acute or chronic treatment with diazepam (2 mg/kg) or adinazolam (20 mg/kg). A time course study indicated that at least 2 weeks of treatment was necessary to observe a significant anxiolytic effect of antidepressants. The anxiolytic effect of the antidepressants was specific to the novel environment, as 2 weeks of treatment with either diazepam or DMI did not influence the latency to begin eating in the home cage. Finally, a single dose of the central benzodiazepine receptor antagonist, Ro15-1788 (20 mg/kg), given 15 min prior to testing, did not block the anxiolytic effects of chronic DMI, while it completely eliminated the effect of chronic diazepam treatment. These data suggest that antidepressants acquire anxiolytic properties following chronic administration and that this effect appears to be independent of the benzodiazepine receptor system.

The Life Engagement Test: Assessing Purpose in Life

Abstract: This article describes a 6-item scale, the Life Engagement Test, designed to measure purpose in life, defined in terms of the extent to which a person engages in activities that are personally valued. Psychometric data are presented including information about the scale's factor structure, internal consistency, test-retest reliability, convergent validity, discriminant predictive validity, and norms. The data suggest that the Life Engagement Test is psychometrically sound across different gender, age, and ethnic groups and is appropriate for wider use. Discussion centers on the use of the Life Engagement Test in behavioral medicine and health psychology research and recent associations that have begun to emerge between the scale and health-relevant outcomes.

Performance assessment of active frequency drifting islanding detection methods

Abstract: Islanding detection is a mandatory feature for grid-connected inverters. The effectiveness of passive islanding detection methods (IDMs) is usually demonstrated by means of nondetection zones (NDZs) represented in a power mismatch space (/spl Delta/P versus /spl Delta/Q). Active frequency drifting IDMs have been shown to provide improved performance but their theoretical NDZ cannot be described in the /spl Delta/P versus /spl Delta/Q space for a general RLC load. This paper shows that a load parameter space based on the values of the quality factor and resonant frequency of the local load (Q/sub f/ versus f/sub 0/) can be used in these cases. It employs a single curve to represent the NDZ of frequency drifting IDMs for any RLC loads. Equations that represent NDZs of three common active IDMs in the Q/sub f/ versus f/sub 0/ load parameter space are derived and it is shown that the slip mode frequency shift and the Sandia frequency shift IDMs can be designed to guarantee islanding detection for equivalent RLC loads with a quality factor smaller than a design value. The accuracy of the NDZs is verified with simulation and experimental results.

Learning about danger: chemical alarm cues and local risk assessment in prey fishes

Abstract: An individual's behaviour patterns can be conceptualized as a series of threat-sensitive trade-offs between ambient predation pressure and a suite of fitness-related activities, such as resource defence, foraging and mating. Individuals that can reliably assess local predation risk could increase their fitness potential by exhibiting predator avoidance behaviours only at appropriate times. However, such learned risk assessment requires reliable information regarding current predation risks. A diverse range of prey fishes are known to possess chemical alarm cues, which when detected by conspecifics and some heterospecifics, elicit a variety of overt and covert responses. These chemical cues, either alone or as a part of a predator's dietary odour, provide reliable information regarding local predation risk. In this review, I describe recent works examining the role of chemosensory information in: (i) acquired predator recognition, (ii) predator inspection behaviour and (iii) the use of conspecific and heterospecific cues as social information sources.

ProbView: a flexible probabilistic database system

Abstract: Probability theory is mathematically the best understood paradigm for modeling and manipulating uncertain information. Probabilities of complex events can be computed from those of basic events on which they depend, using any of a number of strategies. Which strategy is appropriate depends very much on the known interdependencies among the events involved. Previous work on probabilistic databases has assumed a fixed and restrictivecombination strategy (e.g., assuming all events are pairwise independent). In this article, we characterize, using postulates, whole classes of strategies for conjunction, disjunction, and negation, meaningful from the viewpoint of probability theory. (1) We propose a probabilistic relational data model and a genericprobabilistic relational algebra that neatly captures various strategiessatisfying the postulates, within a single unified framework. (2) We show that as long as the chosen strategies can be computed in polynomial time, queries in the positive fragment of the probabilistic relational algebra have essentially the same data complexity as classical relational algebra. (3) We establish various containments and equivalences between algebraic expressions, similar in spirit to those in classical algebra. (4) We develop algorithms for maintaining materialized probabilistic views. (5) Based on these ideas, we have developed a prototype probabilistic database system called ProbView on top of Dbase V.0. We validate our complexity results with experiments and show that rewriting certain types of queries to other equivalent forms often yields substantial savings.