Showing papers by "Concordia University published in 1999"

A Role for the Bed Nucleus of the Stria Terminalis, But Not the Amygdala, in the Effects of Corticotropin-Releasing Factor on Stress-Induced Reinstatement of Cocaine Seeking

Abstract: We have shown that intracerebroventricular administration of the corticotropin-releasing factor (CRF) receptor antagonist D-Phe CRF(12-41), blocks footshock-induced reinstatement of drug seeking in cocaine-trained rats. We now report that D-Phe acts in the bed nucleus of the stria terminalis (BNST), and not in the amygdala, to block footshock-induced reinstatement of cocaine seeking. In addition, CRF injections in the BNST, and not in the amygdala, are sufficient to reinstate cocaine seeking. Rats were trained to self-administer cocaine intravenously on a fixed ratio (FR-1) schedule of reinforcement. After 5 drug-free days, animals were returned to the self-administration chambers and given daily extinction and reinstatement test sessions. To test the effects of D-Phe CRF(12-41) on stress-induced reinstatement, rats were pretreated with vehicle or D-Phe in either the BNST (10 or 50 ng per side) or amygdala (50 or 500 ng per side) before being exposed to 15 min of intermittent footshock stress. To test whether injections of CRF itself could induce reinstatement, rats were given vehicle or CRF in either the BNST (100 or 300 ng per side) or amygdala (300 ng per side) 15 min before the session. Injections of D-Phe into the BNST completely blocked footshock-induced reinstatement of cocaine seeking; injections of CRF itself in this structure induced reinstatement. Injections of these compounds into the amygdala were without effect. These findings suggest that activation of CRF receptors in the BNST, but not in the amygdala, is critical for footshock-induced reinstatement of cocaine seeking.

Developmental Patterns in Security of Attachment to Mother and Father in Late Childhood and Early Adolescence: Associations with Peer Relations

Abstract: This study examined developmental differences in two dimensions of attachment security (parental availability and child dependency on parents) in late childhood (N = 274) and early adolescence (N = 267) and their association with peer relations. Children's perceptions of mother's availability and boys' perceptions of father's availability did not differ as a function of age. Dependency on parents, however, decreased with age. Findings highlight the importance of distinguishing between parental availability and reliance on parental help when measuring attachment developmentally. Children's reports of positive friendship qualities and lack of conflict in their best friendships were related to attachment to both mother and father, whereas the presence of a reciprocated friendship and popularity were not. Father availability was a particularly important predictor of lower conflict with best friends. Findings indicate that the quality of parent-child attachment generalizes primarily to the quality of children's close peer relations.

Scheduling fixed-priority tasks with preemption threshold

Abstract: In the context of fixed-priority scheduling, feasibility of a task set with non-preemptive scheduling does not imply the feasibility with preemptive scheduling and vice versa. We use the notion of preemption threshold, first introduced by Express Logic, in their ThreadX real-time operating system, to develop a scheduling model that subsumes both preemptive and non-preemptive fixed priority scheduling. Preemption threshold allows a task to only disable preemption of tasks up to a specified threshold priority. Tasks having priorities higher than the threshold are still allowed to preempt. With this new scheduling model, we show that schedulability is improved as compared to both the preemptive and nonpreemptive scheduling models. We develop the equations for computing the worst-case response times, using the concept of level-i busy period. Some useful results about the generalized model are presented and an algorithm for optimal assignment of priority and preemption threshold is designed based on these results.

Social, emotional, and behavioral functioning of children with cancer.

Abstract: Objective. It was hypothesized that children with cancer would have more social problems and difficulties with emotional well-being than case control, same race/gender, similarly aged classmates. Study Design. Using a case controlled design, children with any type of cancer requiring chemotherapy except brain tumors ( n = 76), currently receiving chemotherapy, ages 8 to 15, were compared with case control classroom peers ( n = 76). Peer relationships, emotional well-being, and behavior were evaluated based on peer, teacher, parent, and self-report, and were compared using analysis of variance and structural equation modeling. Results. Relative to case controls, children with cancer were perceived by teachers as being more sociable; by teachers and peers as being less aggressive; and by peers as having greater social acceptance. Measures of depression, anxiety, loneliness, and self-concept showed no significant differences, except children with cancer reported significantly lower satisfaction with current athletic competence. There were also no significant differences in mother or father perceptions of behavioral problems, emotional well-being, or social functioning. Scores on all standardized measures were in the normal range for both groups. Comparisons of the correlation matrices of children with cancer and to the correlation matrix of the comparison children using structural equation modeling suggested they were not significantly different. Conclusions. Children with cancer currently receiving chemotherapy were remarkably similar to case controls on measures of emotional well-being and better on several dimensions of social functioning. These findings are not supportive of disability/stress models of childhood chronic illness and suggest considerable psychologic hardiness.

Photoassisted Degradation of Dye Pollutants. 8. Irreversible Degradation of Alizarin Red under Visible Light Radiation in Air-Equilibrated Aqueous TiO2 Dispersions

Abstract: Alizarin red undergoes rapid photoassisted decomposition in air-equilibrated aqueous TiO2 dispersions under visible light radiation (λ > 420 nm). Proton NMR, chemical oxygen demand (CODCr), UV−visible, IR, GC−MS, and spin-trapping ESR spectroscopic techniques were employed to obtain details of the photodegradation of alizarin red. Peroxides and carbonyl species are the first intermediates observed during the process. The major component of the peroxides produced is H2O2, and no organoperoxides were detected. We have also confirmed that in addition to CO2 and to smaller carbonyl species the principal intermediate produced is phthalic acid, which is unable to degrade further because it does not absorb the actinic visible light radiation (λ > 420 nm). The photodegradation kinetics are discussed in terms of the Langmuir−Hinshelwood model, a case of saturation type kinetics. A mechanism for the photoassisted degradation of alizarin red mediated by TiO2 particles under visible light radiation is proposed.

TiO2-Assisted Photodegradation of Dyes. 9. Photooxidation of a Squarylium Cyanine Dye in Aqueous Dispersions under Visible Light Irradiation

Abstract: The TiO2-assisted photodegradation of a squarylium cyanine dye (SQ) has been examined under visible light irradiation (λ ≥ 430 nm) by UV−vis, proton-NMR, ESR, and GC-MS spectroscopies, by peroxide assays in the presence of peroxidase and catalase enzymes, and by chemical oxygen demand (COD) methods Significant results were obtained relevant to the mechanism(s) of TiO2-assisted photodegradations The active oxygen species produced first when an aqueous TiO2 dispersion containing SQ is irradiated by visible light is the superoxide radical anion, which is stable in methanol solvent but very unstable in aqueous media, and is readily converted to •OH radicals via formation and subsequent reduction of H2O2 The quantity of H2O2 increased during the photodegradation; though expected, no organoperoxides were detected Of import, cleavage of the cyanine CC double bond in the SQ dye dominated over the whole degradation process yielding 1-sulfopropyl-3,3-dimethyl-5-bromoindolenium-2-one, the predominant component i

An HMM-based approach for off-line unconstrained handwritten word modeling and recognition

Abstract: Describes a hidden Markov model-based approach designed to recognize off-line unconstrained handwritten words for large vocabularies. After preprocessing, a word image is segmented into letters or pseudoletters and represented by two feature sequences of equal length, each consisting of an alternating sequence of shape-symbols and segmentation-symbols, which are both explicitly modeled. The word model is made up of the concatenation of appropriate letter models consisting of elementary HMMs and an HMM-based interpolation technique is used to optimally combine the two feature sets. Two rejection mechanisms are considered depending on whether or not the word image is guaranteed to belong to the lexicon. Experiments carried out on real-life data show that the proposed approach can be successfully used for handwritten word recognition.

Evidence for H2O2 Generation during the TiO2-Assisted Photodegradation of Dyes in Aqueous Dispersions under Visible Light Illumination

Abstract: Photodegradation of a series of dyes (Rhodamine B, Orange II, Sulfo-rhodamine B, Fluorescein, Alizarin red, Squarylium cyanine, and Eosin) in the presence of TiO2 particles under air-equilibrated controlled conditions and visible light illumination led to the formation of hydrogen peroxide. Combined with chemical oxygen demand (COD) measurements and in situ adsorption of added H2O2, the results reveal that H2O2 is a perfidious intermediate species in the process of dye photodegradation. The formation rate of H2O2 depends on the rate of dye degradation. It can also be decomposed by TiO2 particles under visible light irradiation because of a TiO2/H2O2 surface complex. H2O2 was detected because its formation rate was greater than its decomposition rate; failing this, H2O2 would not be observed. Its decomposition rate depends on the amount of substrates or intermediates formed during dye degradation and adsorbed on the surface of the TiO2 particles. The greater the degradation rate of the dye or the greater t...

Quote Disclosure and Price Discovery in Multiple-Dealer Financial Markets

Abstract: We examine the effects of price disclosure on market performance in a continuous experimental multiple-dealer market in which seven professional market makers trade a single security. The dealers trade with one another and with computerized informed and liquidity traders. Our key comparison is between fully public price queues (pretrade transparent market) and bilateral quoting (pretrade opaque). We find that opening spreads are wider and trading volume is lower in the opaque markets due to higher search costs there. More importantly, however, higher search costs also induce more aggressive pricing strategies, so that price discovery is much faster in the opaque markets. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.

Stress reinstates nicotine seeking but not sucrose solution seeking in rats.

Abstract: Rationale: Intermittent footshock stress effectively reinstates extinguished heroin-, cocaine- and alcohol-taking behaviors, but not behaviors previously maintained by food reinforcers. Here we tested further the generality of the phenomenon of stress-induced reinstatement by determining the effect of footshock on reinstatement of operant responding previously maintained by nicotine or palatable sucrose solutions. Methods: Groups of rats were trained to self-administer either nicotine (0.03 mg/kg per infusion, 14 days) or sucrose (10 or 30% w/v, 14–20 days). After extinction of the nicotine- or the sucrose-reinforced behaviors for 5–15 days, the rats were exposed to intermittent footshock stress (5 and 15 min, 0.8 mA) during tests for reinstatement. Results: Footshock reliably reinstated nicotine seeking after extinction of the drug-reinforced behavior. In contrast, the same parameters of footshock stress did not consistently reinstate operant responding previously maintained by sucrose solutions. Conclusions: These and previous data suggest that stressors may be more effective stimuli for reinstatement of behaviors previously maintained by drug reinforcers as compared with non-drug reinforcers.

Students'' approaches to vocabulary learning and their relationship to success

Abstract: Students’ approaches to vocabulary learning were surveyed in two distinct learning environments: one where English was studied as a second language (ESL), and another where it was a foreign language (EFL). A questionnaire, adapted from Sanaoui's (1992) work, was administered to 47 ESL and 43 EFL students. They were asked to indicate, among other things, the amount of time they usually spent on vocabulary learning, the extent to which they engaged in independent language study, the type of vocabulary learning activities they did on a regular basis, the frequency and elaborateness of their note-taking and reviewing efforts, and the frequency and elaborateness with which they used dictionaries. Whereas students in the two settings exhibited significant differences in the use of some of the strategies, other parts of their strategic behaviour were strikingly similar. Cluster analysis, a technique used for finding relatively homogeneous subgroups in a population, identified 8 different profiles of student approaches to lexical learning. Some clusters exhibited a remarkably “flat” profile in that they used either all or none of the strategies. The majority of learners, however, fell into the more saw-toothed profile clusters, exhibiting clear preferences for certain types of strategic behaviour. Analyses were also conducted to determine a possible relationship between strategy use and achievement level. Students’ performance on two tests, a Yes/No test assessing knowledge of academic vocabulary and a cloze test assessing overall English proficiency, were compared for the clusters. More frequent and elaborate strategy use was associated with higher levels of achievement, whereas lack of self-reported effort on the students' part was linked to poor performance. Results also suggested thattimeand learnerindependencewere the two measures most closely related to success in vocabulary learning and higher overall English proficiency.

Photoluminescence and Transient Spectroscopy of Free Base Porphyrin Aggregates

Abstract: Solutions of free base meso-tetraphenylporphyrin (H2TPP), meso-tetra(4-carboxyphenyl)porphyrin (H2TPPC), and meso-tetra(4-pyridyl)porphyrin (H2TPyP) under various conditions generate aggregates whose absorption spectra are characterized by invariant Soret bands with bandwidths that are independent of the preparative method. One of the Soret bands is blue-shifted (H-aggregate) relative to the monomeric porphyrin band; other Soret bands are red-shifted (J-aggregates). The aggregates are characterized by different nonradiative rate constants for excited singlet-state decay and by different efficiencies of singlet−singlet annihilation at the high energies of laser excitation. The quantum yields of fluorescence vary between 10-5 and 10-2, and the corresponding fluorescence lifetimes vary in the range from 10-12 to 10-9 s; they are more than 1 order of magnitude smaller than those of the corresponding monomeric porphyrins. Lifetimes (τ) correlate with the characteristic ground-state absorption recovery times of...

Tableau techniques for querying information sources through global schemas

Abstract: The foundational homomorphism techniques introduced by Chandra and Merlin for testing containment of conjunctive queries have recently attracted renewed interest due to their central role in information integration applications. We show that generalizations of the classical tableau representation of conjunctive queries are useful for computing query answers in information integration systems where information sources are modeled as views defined on a virtual global schema. We consider a general situation where sources may or may not be known to be correct and complete. We characterize the set of answers to a global query and give algorithms to compute a finite representation of this possibly infinite set, as well as its certain and possible approximations. We show how to rewrite a global query in terms of the sources in two special cases, and show that one of these is equivalent to the Information Manifold rewriting of Levy et al.

Dopamine Fluctuations in the Nucleus Accumbens during Maintenance, Extinction, and Reinstatement of Intravenous d-Amphetamine Self-Administration

Abstract: Moment-to-moment fluctuations of nucleus accumbens dopamine (DA) were determined in rats self-administering or passively receiving "yoked" intravenous infusions of D-amphetamine. The initial lever presses of each session caused elevations in DA concentration, usually to an initial peak that was not maintained throughout the rest of the session. As the initial ("loading") injections were metabolized, DA levels dropped toward baseline but were sustained at elevated plateaus by subsequent lever pressing that was spaced throughout the remainder of the 3 hr sessions. During this period, DA levels fluctuated phasically, time-locked to the cycle of periodic lever pressing. Consistent with the known pharmacological actions and dynamics of amphetamine, peak DA elevations were seen approximately 10-15 min after each injection, and the mean DA level was at a low point in the phasic cycle at the time of each new lever press. During extinction periods when saline was substituted for amphetamine, DA levels dropped steadily toward baseline levels despite a dramatic increase in (now-unrewarded) lever pressing. Noncontingent injections during extinction reinstated lever-pressing behavior and increased nucleus accumbens DA concentrations. These data are consistent with the hypothesis that under the conditions of this experiment-during periods of amphetamine intoxication in well-trained animals-the timing of amphetamine self-administration comes primarily under the control of extracellular DA concentrations. The probability of lever pressing during the maintenance phase is highest when DA concentrations fall near a characteristic trigger point, a trigger point that is significantly elevated above baseline, and falls as DA concentrations fall below or increase above that trigger point.

Terminology, relative photonic efficiencies and quantum yields in heterogeneous photocatalysis. part ii: experimental determination of quantum yields†

Abstract: In the preceding article [Pure Appl. Chem. 71, 303–320 (1999)] we examined two principal features of heterogeneous photocatalysis that demanded scrutiny: (i) description of photocatalysis and (ii) description of process efficiencies. For the latter we proposed a protocol relative photonic efficiency which could subsequently be converted to quantum yields. A difficulty in expressing a quantum yield in heterogeneous photochemistry is the very nature of the system, either solid/liquid or solid/gas, which places severe restrictions on measurement of the photon flow absorbed by the light harvesting component, herein the photocatalyst TiO2, owing to non-negligible scattering by the particulates. It was imperative therefore to examine the extent of this problem. Extinction and absorption spectra of TiO2 dispersions were determined at low titania loadings by normal absorption spectroscopy and by an integrated sphere method, respectively, to assess the extent of light scattering. The method is compared to the one reported by Grela et al. [J. Phys. Chem. 100, 16 940 (1996)] who used a polynomial extrapolation of the light scattered in the visible region into the UV region where TiO2 absorbs significantly. This extrapolation underestimates the scattering component present in the extinction spectra, and will no doubt affect the accuracy of the quantum yield data. Further, we report additional details in assessing limiting photonic efficiencies and quantum yields in heterogeneous photocatalysis.

Immigrant Assimilation and Welfare Participation: Do Immigrants Assimilate Into or Out of Welfare?

Abstract: This paper analyzes differences in welfare utilization between immigrants and natives in Sweden using a large panel data set, LINDA, for the years 1990 to 1996. Both welfare expenditures and immigration increased substantially in Sweden in the 1990's. We find that immigrants use welfare to a greater extent than natives and that non-refugee immigrants utilize social assistance less than refugee immigrants. Differences in welfare participation and number of months on welfare between immigrants and natives cannot be explained by observable socioeconomic characteristics. Using a random effects probit model, we find that immigrants lower their participation rates in welfare with time spent in Sweden. Refugees display substantially higher public assistance participation rates upon arrival in Sweden compared to non-refugee immigrants, but they assimilate out of welfare at a faster rate than non-refugee immigrants. Neither immigrant group is predicted to reach the participation rates of native households within a 20 year period in Sweden. A fixed effects logit model supports these findings. The predicted differences in the length of social assistance spells follow a very similar pattern. Simulations of the move to a national uniform benefits structure in 1998 show a decrease in the participation rate and in expenditures.

Empowerment: power, culture and leadership – a strategy or fad for the millennium?

Abstract: Since 1990, the number of empirical and applied research dealing with employee empowerment has proliferated. This article will examine four dimensions of power: various resources to influence the outcome of decision‐making; controlling access to those processes; through hegemonic process to legitimize power through culture and norms; and determining the limits of power. A critical perspective from other behavioral sciences will present various designs. Foucauldian Theory will challenge the devolution of power via prior research attempts. Contemporary research on organization culture and structure will be examined via the validation of six hypotheses. Organizational characteristics facilitating empowerment such as vision, openness and teamwork, discipline and control, support and security will be discussed, along with the impact of leadership on an empowered workforce. Psychological dimensions of empowerment: choice, competence, meaningfulness and progress are examined in addition to trust issues. Some conclusions and recommendations will integrate the diverse theories.

Adaptive multistage parallel interference cancellation for CDMA

Abstract: Although the multistage interference cancellation detector is simple in structure, its performance degrades when the number of active users becomes large. In some cases, the performance is even worse than that without cancellation, due to the lack of the exact knowledge of the interfering signal in cancellation. Partial interference cancellation suggested by Divsalar and Simon (see IEEE Trans. Commun., vol.46, p.258-68, 1998) tries to remedy this weakness by reducing the cost of a wrong interference estimation through a weight in each stage. This paper presents an adaptive multistage structure based on the partial interference cancellation approach. In this structure, the weights are obtained by minimizing the mean-square error between the received signal and its estimate through a least mean square (LMS) algorithm. The resulting weights contain reliability information for the hard decisions made in the previous stage. Neither a training sequence nor a pilot signal is needed in the proposed scheme, and its complexity is much lower than that of linear multiuser detectors. Simulation results show that the proposed scheme can outperform some of the existing interference cancellation methods in both the additive white Gaussian noise (AWGN) and the multipath fading channels.

Injections of N-methyl-D-aspartate into the ventral hippocampus increase extracellular dopamine in the ventral tegmental area and nucleus accumbens.

Abstract: The nucleus accumbens septi receives inputs from dopaminergic neurons of the ventral tegmental area (VTA) and glutamatergic neurons of the ventral subiculum (VS). The convergence of these inputs in the NAS is important for the normal expression of exploratory locomotion; stimulation of the VS by injection of the glutamate receptor agonist N-methyl-D-aspartate (NMDA) causes dopamine-dependent increases in locomotion. In the present study, in vivo microdialysis in conjunction with high-performance liquid chromatography and electrochemical detection (HPLC-EC) was used to estimate changes in extracellular dopamine in the VTA and NAS in response to intra-VS injections of NMDA (0.074, 0.28, 0.74 microg). NMDA injections caused dose-dependent elevations in extracellular dopamine in each region. Each dose of NMDA clearly increased extracellular dopamine in the NAS, whereas only the two higher doses increased dopamine significantly in the VTA. The highest dose of NMDA elevated extracellular dopamine to approximately 180% of baseline in each region. Whereas elevations in NAS dopamine might be induced by impulse-independent local mechanisms, elevations of dopamine in the VTA are presumed to reflect increased somatodendritic release associated with increased impulse flow through dopamine neurons. Thus, the present study suggests that the modulation of dopaminergic neurotransmission by the ventral subiculum results from a trans-synaptic activation of dopamine cell bodies in the VTA.

Analysis of class separation and combination of class-dependent features for handwriting recognition

Abstract: In this paper, we propose a new approach to combine multiple features in handwriting recognition based on two ideas: feature selection-based combination and class dependent features. A nonparametric method is used for feature evaluation, and the first part of this paper is devoted to the evaluation of features in terms of their class separation and recognition capabilities. In the second part, multiple feature vectors are combined to produce a new feature vector. Based on the fact that a feature has different discriminating powers for different classes, a new scheme of selecting and combining class-dependent features is proposed. In this scheme, a class is considered to have its own optimal feature vector for discriminating itself from the other classes. Using an architecture of modular neural networks as the classifier, a series of experiments were conducted on unconstrained handwritten numerals. The results indicate that the selected features are effective in separating pattern classes and the new feature vector derived from a combination of two types of such features further improves the recognition rate.

Systematic effects in the rating of second-language speaking ability: test method and learner discourse:

Abstract: Major differences exist in two approaches to the study of second-language performance. Second-language-acquisition (SLA) research examines effects upon discourse, and is typically unconcerned with scores. Language-testing (LT) research investigates effects upon scores, generally without reference to discourse. Within a general framework of test taking and scoring, we report research from these two fields as it relates to questions of systematic effects on second-language tests. We then examine findings incidental to a test-development project.The findings were consistent with LT research into systematic effects of task and rater on ratings, and with SLA research into systematic effects of task on discourse. Using empirically derived scales as indicators of salient features of discourse, we infer that task type influences strategies for assessing language performance. Explanations for these joint findings are not afforded by either standard LT or SLA perspectives. There is no theory of method to explain ho...

Hardy spaces, BMO, and boundary value problems for the Laplacian on a smooth domain in ^{}

Abstract: We study two different local Hp spaces, 0 < p ≤ 1, on a smooth domain in Rn, by means of maximal functions and atomic decomposition. We prove the regularity in these spaces, as well as in the corresponding dual BMO spaces, of the Dirichlet and Neumann problems for the Laplacian. 0. Introduction Let Ω be a bounded domain in R, with smooth boundary. The L regularity of elliptic boundary value problems on Ω, for 1 < p < ∞, is a classical result in the theory of partial differential equations (see e.g. [ADN]). In the situation of the whole space without boundary, i.e. where Ω is replaced by R, the results for L, 1 < p < ∞, extend to the Hardy spaces H when 0 < p ≤ 1 and to BMO. Thus it is a natural question to ask whether the L regularity of elliptic boundary value problems on a domain Ω has an H and BMO analogue, and what are the H and BMO spaces for which it holds. This question was previously studied in [CKS], where partial results were obtained and were framed in terms of a pair of spaces, hr(Ω) and h p z(Ω). These spaces, variants of those defined in [M] and [JSW], are, roughly speaking, the “largest” and “smallest” h spaces that can be associated to a domain Ω. Our purpose here is to substantially extend the previous results by determining those h spaces on Ω which are particularly applicable to boundary value problems. These spaces allow one to prove sharp results (preservation of the appropriate h spaces) for all values of p, 0 < p ≤ 1, as well as the preservation of corresponding spaces of BMO functions. 0.1. Motivation and statement of results. There are two approaches to defining the appropriate Hardy spaces on Ω. Recall that the spaces H(R), for p < 1, are spaces of distributions. Thus one approach is to look at the problem from the point of view of distributions on Ω. If we denote by D(Ω) the space of smooth functions with compact support in Ω, and by D′(Ω) its dual, we can consider the space of distributions in D′(Ω) which are the restriction to Ω of distributions in H(R) (or in h(R), the local Hardy spaces defined in [G].) These spaces were studied in [M] (for arbitrary open sets) and in [CKS] (for Lipschitz domains), where they were denoted hr(Ω) (the r stands for “restriction”.) While one is able to prove regularity results for the Dirichlet problem for these spaces when p is near 1 (see [CKS]), these spaces are no longer appropriate when p Received by the editors September 5, 1996 and, in revised form, March 20, 1997. 1991 Mathematics Subject Classification. Primary 35J25, 42B25; Secondary 46E15, 42B30. c ©1999 American Mathematical Society