Showing papers by "Concordia University published in 2000"

Fast, efficient generation of high‐quality atomic charges. AM1‐BCC model: I. Method

Abstract: The AM1-BCC method quickly and efficiently generates high-quality atomic charges for use in condensed-phase simulations. The underlying features of the electron distribution including formal charge and delocalization are first captured by AM1 atomic charges for the individual molecule. Bond charge corrections (BCCs), which have been parameterized against the HF/6-31G* electrostatic potential (ESP) of a training set of compounds containing relevant functional groups, are then added using a formalism identical to the consensus BCI (bond charge increment) approach. As a proof of the concept, we fit BCCs simultaneously to 45 compounds including O-, N-, and S-containing functionalities, aromatics, and heteroaromatics, using only 41 BCC parameters. AM1-BCC yields charge sets of comparable quality to HF/6-31G* ESP-derived charges in a fraction of the time while reducing instabilities in the atomic charges compared to direct ESP-fit methods. We then apply the BCC parameters to a small “test set” consisting of aspirin, d-glucose, and eryodictyol; the AM1-BCC model again provides atomic charges of quality comparable with HF/6-31G* RESP charges, as judged by an increase of only 0.01 to 0.02 atomic units in the root-mean-square (RMS) error in ESP. Based on these encouraging results, we intend to parameterize the AM1-BCC model to provide a consistent charge model for any organic or biological molecule. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 132–146, 2000

Robust adaptive control of a class of nonlinear systems with unknown backlash-like hysteresis

Abstract: Deals with adaptive control of a class of nonlinear dynamic systems preceded by unknown backlash-like hysteresis nonlinearities, where the hysteresis is modeled by a differential equation. By exploiting solution properties of the differential equation and combining those properties with adaptive control techniques, a robust adaptive control algorithm is developed without constructing a hysteresis inverse. The new control law ensures global stability of the adaptive system and achieves both stabilization and tracking to within a desired precision. Simulations performed on a nonlinear system illustrate and clarify the approach.

Modulation of brain reward circuitry by leptin.

Abstract: Leptin, a hormone secreted by fat cells, suppresses food intake and promotes weight loss. To assess the action of this hormone on brain reward circuitry, changes in the rewarding effect of lateral hypothalamic stimulation were measured after leptin administration. At five stimulation sites near the fornix, the effectiveness of the rewarding electrical stimulation was enhanced by chronic food restriction and attenuated by intracerebroventricular infusion of leptin. In contrast, the rewarding effect of stimulating neighboring sites was insensitive to chronic food restriction and was enhanced by leptin in three of four cases. These opposing effects of leptin may mirror complementary changes in the rewarding effects of feeding and of competing behaviors.

Learning and design of principal curves

Abstract: Principal curves have been defined as "self-consistent" smooth curves which pass through the "middle" of a d-dimensional probability distribution or data cloud. They give a summary of the data and also serve as an efficient feature extraction tool. We take a new approach by defining principal curves as continuous curves of a given length which minimize the expected squared distance between the curve and points of the space randomly chosen according to a given distribution. The new definition makes it possible to theoretically analyze principal curve learning from training data and it also leads to a new practical construction. Our theoretical learning scheme chooses a curve from a class of polygonal lines with k segments and with a given total length to minimize the average squared distance over n training points drawn independently. Convergence properties of this learning scheme are analyzed and a practical version of this theoretical algorithm is implemented. In each iteration of the algorithm, a new vertex is added to the polygonal line and the positions of the vertices are updated so that they minimize a penalized squared distance criterion. Simulation results demonstrate that the new algorithm compares favorably with previous methods, both in terms of performance and computational complexity, and is more robust to varying data models.

The potential of distributed generation to provide ancillary services

Abstract: The growing concerns regarding electric power quality and availability have led to the installation of more and more distributed generation. In parallel and in the context of an accelerating trend towards deregulation of the electric industry, the unbundling of services, many grouped under ancillary services, should create a market for some of these services. This paper discusses the potential of distributed generation (DG) to provide some of these services. In particular, DG can serve locally as the equivalent of a spinning reserve and voltage support of the AC bus. The main types of distributed generation with emphasis on the power electronic interface and the configurations appropriate to provide ancillary services are reviewed. The flexibility and features provided by the power electronic interface are illustrated. In addition to control of the real power, other functions can be incorporated into the design of the interface to provide services, such as reactive power, and resources associated with power quality. These include voltage sag compensation and harmonic filtering. The implications on the design of the power converter interface are discussed.

Treatment of GAD. Targeting intolerance of uncertainty in two types of worry.

Abstract: This study evaluates the efficacy of a cognitive-behavioral treatment for generalized anxiety disorder (GAD) that addresses two types of worries: (a) those about situations that are amenable to problem solving, and (b) those about situations that are not. The treatment's goal is to help patients become more tolerant of uncertainty by discriminating between both types of worry and applying the correct strategy to each type. A multiple baseline design was used and subjects were 4 adults with a primary diagnosis of GAD. Treatment outcome was assessed with daily self-monitoring, self-report questionnaires, and standardized clinician ratings. At posttest and 6-month follow-up, 3 of 4 subjects no longer met diagnostic criteria for GAD and had attained high end-state functioning. At 12-month follow-up, none of the subjects met GAD diagnostic criteria but end-state functioning was variable. The results also show that treatment outcome was highly related to change in intolerance of uncertainty.

Toeholds, Bid Jumps, and Expected Payoffs in Takeovers

Abstract: We estimate sequentially outcome probabilities and expected payoffs associated with first, second, and final bids in a large sample of tender offer contests. Rival bids arrive quickly and produce large bid jumps. Greater bidder toeholds (prebid ownership of target shares) reduce the probability of competition and target resistance and are associated with both lower bid premiums and lower prebid target stock price runups. The expected payoff to target shareholders is increasing in the bid premium and in the probability of competition, but decreasing in the bidder's toehold. The initial bidder's expected payoff is significantly positive in the "rival-bidder-win" outcome, in part reflecting gains from the pending toehold sale. Despite these dramatic toehold effects, only half of the initial bidders acquire toeholds. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.

On Assessing Individual Differences in Rumination on Sadness

Abstract: The Rumination on Sadness Scale (RSS), an individual-difference measure of rumination on sadness, was developed as an alternative to the Ruminative Responses scale of the Response Styles Questionnaire (RRRSQ; Nolen-Hoeksema & Morrow, 1991). Research has shown the RRRSQ to consist of multiple, not highly intercorrelated factors; only I factor explicitly addresses rumination. In Study 1, a 1-factor solution to a principal components analysis was shown to hold for responses to the RSS. The RSS was also shown to be reliable. In Study 2, convergent and discriminant validity of the RSS were assessed. In Study 3, individuals with high RSS scores exhibited more distress regarding current concerns with the introduction of a delay period (to allow them to ruminate) after a sad mood induction.

Photooxidation Pathway of Sulforhodamine-B. Dependence on the Adsorption Mode on TiO2 Exposed to Visible Light Radiation

Abstract: The temporal course of the photooxidation of sulforhodamine-B (SRB) in aqueous media illuminated by visible wavelengths in the presence of TiO2 has been examined to determine the nature of the intermediate species produced and to explore the operative reaction pathway(s). Two pathways are described to account for the differences in the final photooxidation products whose nature depends on the different modes of adsorption of the dye on the metal-oxide mediator. In the SRB/TiO2 system, when SRB is adsorbed on the positively charged TiO2 particle surface through a sulfonate group cleavage of the SRB chromophore structure predominates and N-de-ethylation occurs only to a slight extent with the major photooxidation products being diethylamine and carbon dioxide. In the presence of the anionic dodecylbenzenesulfonate surfactant DBS, when SRB is near the negatively charged DBS/TiO2 interface through the positive diethylamine group N-de-ethylation occurs preferentially before destruction of the structure with th...

Variations in patterns of attraction to same- and other-sex peers during early adolescence.

Abstract: Differences in attraction to same- and other-sex peers as a function of sex, age, individual characteristics (i.e., aggression), and context were examined in a longitudinal study of early adolescent boys and girls (N = 217) that covered the transition from elementary school (Time 1) to middle school (Times 2 and 3). Consistent with T. Moffitt's (1993) concept of the "maturity gap," attraction to aggressive peers, especially attraction to aggressive boys among girls, increased with age and upon entry to middle school, as did attraction to peers who stood out in the peer group in easily observable ways. Attraction to peers who presented features associated with good classroom-based behavior decreased. These patterns are discussed in terms of the developmental needs served by associating with particular peers.

Applications of evolutionary psychology in marketing

Abstract: Evolutionary psychology is an emerging paradigm in psychological science. The current article introduces this framework to marketing scholars and presents evidence for its increasing acceptance within the social science community. As a result, a case is made for the application of evolutionary psychology to marketing, and especially consumer behavior. Application of the evolutionary framework in studying gender-related consumption behavior is illustrated by comparing the evolutionary predictions with results obtained from previous studies, by supporting these predictions with market-level consumption data, and by proposing new hypotheses based on this framework. Also discussed are the potential applications of evolutionary psychology to other consumption-related phenomena like evaluation of endorser attractiveness in advertising, biologically driven consumption choices among women, consumer-experienced emotions in service encounters, and consumption choices as inclusive fitness maximization rather than utility maximization. 2000 John Wiley & Sons, Inc.

Anatomy of a merger: behavior of organizational factors and processes throughout the pre‐ during‐ post‐stages (part 1)

Abstract: The multiple organizational factors impacting on a merger as well as those processes being impacted on throughout the merger process will be examined. First, the issue of constant and lucid communication and its importance throughout the merger and acquisition (MA during the merger; post‐merger.

Gender differences in information search strategies for a Christmas gift

Abstract: Examines the underlying determinants of in‐store information search for a Christmas clothing gift, specifically focusing on gender differences. Two non‐personal (general and specific) and one personal (sales clerk assistance) in‐store information search domains were obtained from the results of a survey of actual consumers carried out shortly after the Christmas season. Consistent with the predictions of the selectivity model, females appeared to comprehensively acquire in‐store information, whereas males appeared to heuristically limit their search to a smaller subset of in‐store information. More specifically, females scored significantly higher than males on indices of both general and specific information search. Females, compared to males, were also found to start Christmas shopping much earlier, purchase more gifts, and embark on a greater number of shopping trips. Other observed gender differences are discussed.

Chemical Stimulation of the Ventral Hippocampus Elevates Nucleus Accumbens Dopamine by Activating Dopaminergic Neurons of the Ventral Tegmental Area

Abstract: Dual-probe microdialysis (with HPLC and electrochemical detection) in freely moving rats and single-unit recording in anesthetized rats were used to study the extent to which impulse flow through the ventral tegmental area (VTA) contributes to elevations in nucleus accumbens (NAS) dopamine (DA) evoked by stimulation of the ventral subiculum (VS). During perfusion of artificial extracellular fluid into the VTA, injections of 0.74 microgram of the excitatory amino acid NMDA into the VS elevated accumbens DA to >150% of basal values. During intra-VTA perfusion of either 1 microM tetrodotoxin (which blocks impulse flow) or 1 mM kynurenic acid (which blocks excitatory glutamate receptors), injections of NMDA into the VS failed to elevate accumbens DA. Thus, increased impulse flow through VTA DA neurons, mediated by excitatory glutamate inputs to this region, appears critical for VS stimulation to elevate NAS DA. Increased impulse flow through VTA DA neurons was confirmed using single-unit recording in anesthetized rats. Intra-VS NMDA injections increased the firing rates of 45% (14 of 31), decreased the firing rates of 13% (4 of 31), and had no effect on 42% (13 of 31) of VTA DA neurons. Increases in firing rates were evident within 15 min of NMDA injections, a time at which VS NMDA injections elevate accumbens DA in awake animals. The results of the present experiments identify the VTA as a critical site through which outputs from the VS modulate NAS dopaminergic neurotransmission.

Clonidine blocks stress-induced reinstatement of heroin seeking in rats: an effect independent of locus coeruleus noradrenergic neurons.

Abstract: Using a reinstatement procedure, it has been shown that intermittent footshock stress reliably reinstates extinguished drug-taking behaviour in rats. Here we studied the role of noradrenaline (NE), one of the main brain neurotransmitters involved in responses to stress, in reinstatement of heroin seeking. We first determined the effect of clonidine, an alpha-2 adrenergic receptor agonist that decreases NE cell firing and release, on stress-induced reinstatement of heroin seeking. Rats were trained to self-administer heroin (0.1 mg/kg per infusion, IV, three 3-h sessions per day) for 9-10 days. Extinction sessions were given for up to 11 days during which saline was substituted for the drug. Tests for reinstatement were then conducted after exposure to intermittent footshock (5, 15 and 30 min, 0.5 mA). During testing, clonidine was injected systemically (10-40 microgram/kg, i.p.) or directly into the lateral or fourth ventricles (1-3 microram). Clonidine (1-2 microgram per site) or its charged analogue, 2-[2, 6-diethylphenylamino]-2-imidazole (ST-91, 0.5-1 microgram per site), was also injected bilaterally into the locus coeruleus (LC), the main noradrenergic cell group in the brain. Clonidine blocked stress-induced reinstatement of drug seeking when injected systemically or into the cerebral ventricles. In contrast, neither clonidine nor ST-91 consistently altered stress-induced reinstatement when injected into the locus coeruleus. We therefore studied the effect of lesions of the lateral tegmental NE neurons on stress-induced reinstatement. 6-Hydroxydopamine (6-OHDA) lesions performed after training for heroin self-administration had no effect on extinction of heroin-taking behaviour, but significantly attenuated reinstatement induced by intermittent footshock. These data suggest that: (i) clonidine prevents stress-induced relapse to heroin seeking by its action on neurons other than those of the locus coeruleus; and (ii) activation of the lateral tegmental NE neurons contributes to stress-induced reinstatement of heroin seeking.

Efficient mining of constrained correlated sets

Abstract: Studies the problem of efficiently computing correlated item sets satisfying given constraints. We call them valid correlated item sets. It turns out that constraints can have subtle interactions with correlated item sets, depending on their underlying properties. We show that, in general, the set of minimal valid correlated item sets does not coincide with that of minimal correlated item sets that are valid, and we characterize classes of constraints for which these sets coincide. We delineate the meaning of these two spaces and give algorithms for computing them. We also give an analytical evaluation of their performance and validate our analysis with a detailed experimental evaluation.

Direct evidence for ribonucleolytic activity of a PR-10-like protein from white lupin roots.

Abstract: An abundant 17 kDa protein which was isolated and characterized from 10-day old healthy root tissue of white lupin (Lupinus albus) proved to have a high sequence similarity to pathogenesis-related proteins found in other species. Subsequently, a corresponding clone (LaPR-10) was identified in a cDNA library prepared from the same tissue that exhibited a high amino acid sequence similarity to a number of the PR-10 family proteins. The clone contains an open reading frame encoding a polypeptide of 158 amino acids, with a predicted molecular mass of 16 905 Da and an isoelectric point of 4.66. Southern blot analysis indicates that LaPR-10 is likely a single-copy gene, or a member of a small gene family. The clone was expressed in Escherichia coli, and its protein product was purified to near homogeneity. Both the native and the recombinant proteins were immunorecognized by antibodies raised against pea PR-10 proteins, and exhibited a ribonucleolytic activity against several RNA preparations, including lupin root total RNA. Characterization of its enzymatic properties indicates that the LaPR-10 protein belongs to the class II ribonucleases. We present evidence that the white lupin 17 kDa protein is constitutively expressed during all stages of root development and, to a lesser extent, in other plant parts. In addition, we demonstrate the presence, in the LaPR-10 amino acid sequence, of a number of motifs that are common to most PR-10 proteins, as well as a RGD motif that is shared only with the alfalfa SRG1 sequence.

Classifier Combinations: Implementations and Theoretical Issues

Abstract: Much work has been done in the past decade to combine decisions of multiple classifiers in order to obtain improved recognition results. Many methodologies have been designed and implemented for this purpose. This article considers some of the current developments according to the structure of the combination process, and discusses some issues involved in each structure. In addition, theoretical investigations that have been performed in this area are also examined, and some related issues are discussed.

“Substance Abuse” and “Dysfunctionalism”: Current Trends in Phonology

Abstract: Dans cette note, l'A. se penche sur les relations entre la forme et la substance dans le domaine de la phonologie, en procedant tout d'abord a une definition des notions de forme et de substance, puis a une critique des travaux recents portant explicitement ou implicitement sur les relations entre ces deux notions. Il montre ainsi que les tendances actuelles en phonologie sont incompatibles a la fois avec une definition coherente de la forme et de la substance et avec les principes scientifiques de base. Il pense en effet que les generalisations qui reposent sur des patrons de la substance phonetique ne sont pas pertinents pour la theorie phonologique au sens strict, et suggere que l'objectif de la theorie phonologique devrait consister a decouvrir le noyau de proprietes formelles (ex : organisation en syllabes et en pieds, processus de diffusion des traits) independantes de la modalite et de la substance phonetique

Dynamic recovery: sufficient mechanism in the hot deformation of Al (<99.99)

Abstract: A recent OIM study of the substructure in hot compressed Al has observed an increase in the fraction of boundaries both of 15–20° and above 20° as strain rises from 0.9 to 1.5. This was interpreted as evidence of continuous dynamic recrystallization being the mechanism for the steady state deformation. However, when the original grain boundaries and transition boundaries between deformation bands are discounted, the fraction of 15–20° boundaries is reduced to less than 20% and would be much lower if subboundaries less than 0.5° visible in TEM were taken into account. The present authors argue that dynamic recovery maintains the subgrains of constant size, low misorientation and equiaxed to produce a steady state and can permit a limited number of discrete segments with higher misorientation notably as temperature falls. Moreover, continuous dynamic recrystallization is not appropriate terminology because it is far from reaching the completion observed in other instances of continuous recrystallization.

Feedback Stabilization and Lyapunov Functions

Abstract: Given a locally defined, nondifferentiable but Lipschitz Lyapunov function, we employ it in order to construct a (discontinuous) feedback law which stabilizes the underlying system to any given tolerance. A converse result shows that suitable Lyapunov functions of this type exist under mild assumptions. We also establish that the feedback in question possesses a robustness property relative to measurement error, despite the fact that it may not be continuous.

Job stress and burnout among Canadian managers and nurses: An empirical examination

Abstract: This study examined the relationship of job stress with burnout and its three dimensions (emotional exhaustion, lack of accomplishment and depersonalization), job satisfaction, organizational commitment and psychosomatic health problems. Data were collected by means of a structured questionnaire from Canadian managers (N = 67) and nurses (N = 173). Pearson correlation and moderated multiple regression were used to analyze the data. Job stress was significantly correlated with overall burnout and its three dimensions and job satisfaction in both samples. In the nursing sample, job stress was also significantly correlated with psychosomatic health problems and organizational commitment. Moderated multiple regression only marginally supported the role of gender as a moderator of stress-burnout relationship.

Enhancing Team Mental Model Measurement with Performance Appraisal Practices

Abstract: Little dispute exists with regard to the conceptual and practical contributions of team mental models (TMMs) to team-related research and applications, yet the measurement of TMMs poses great challenges for researchers and practitioners. Borrowing from performance appraisal practices, this article presents a new method for assessing TMMs that is user-friendly and allows for the measurement of both TMM accuracy and similarity. The extent to which TMM similarity and accuracy indices predict team performance in a field setting is examined. Contributions to team research and practice are discussed.