Showing papers by "Concordia University published in 1994"
TL;DR: In this article, a system-focused perspective is considered with regard to the determinants of work performance and the system is seen as an important source of variance affecting performance both indirectly and interactively.
Abstract: Based on recently proposed principles of total quality management (TQM), a system-focused perspective is considered here with regard to the determinants of work performance The system is seen as an important source of variance affecting performance both indirectly and interactively Moreover, the individual is seen as potentially affecting the system Hierarchical level and autonomy are considered as key moderating variables in understanding individual versus system influences on work performance Implications are discussed with regard to performance management processes in organizations
431 citations
TL;DR: DNA-modified electrodes modified by the inclusion of either octadecylamine or stearic acid were used as solid phases to which DNA was covalently bound to study hybridization with analyte poly(dA)4000, and results indicate slow (> or = 1 h) hybridization at low ionic strength and fast (< or = 10 min) hybridized at high ionicstrength.
Abstract: Carbon paste electrodes modified by the inclusion of either octadecylamine or stearic acid were used as solid phases to which DNA was covalently bound. Immobilized DNA was detected by voltammetry of solutions containing submillimolar quantities of Co(bpy)3(ClO4)3, Co(phen)3(ClO4)3, and Os(bpy)3-Cl2 (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline), all of which associate reversibly with immobilized DNA and yield increased peak currents at DNA-modified electrodes. Immobilization onto octadecylamine-modified electrodes was performed using a water-soluble carbodiimide, and at high DNA concentrations in the reaction mixture, it resulted in visible polymerization of DNA on the surface. Optimization of the deoxyguanosine- (dG-) selective immobilization reaction for stearic acid-modified electrodes, using water-soluble carbodiimide and N-hydroxysulfosuccinimide reagents to activate carboxylate groups on the surface, yielded conditions of 4.5% (w/w) stearic acid and 10 micrograms/mL DNA. Polythymidylic acid of 4000-base average length (poly(dT)4000) was immobilized at stearic acid-modified electrodes following enzymatic elongation with dG residues at the 3'-end. These DNA-modified electrodes were used to study hybridization with analyte poly(dA)4000 by in situ voltammetry of 60 microM Co(bpy)3(ClO4)3 at low ionic strength (20 mM NaCl), and by voltammetry of the same complex, following exposure of the electrode to poly(dA)4000 in a separate hybridization step conducted at high ionic strength (0.5 M NaCl). Results indicate slow (> or = 1 h) hybridization at low ionic strength and fast (< or = 10 min) hybridization at high ionic strength.(ABSTRACT TRUNCATED AT 250 WORDS)
420 citations
TL;DR: This article investigated the upper limits of the students' informal processes in the solution of first degree equations in one unknown prior to any instruction and found that the existence of acognitive gap between arithmetic and algebra, a cognitive gap that can be characterized asthe students' inability to operate spontaneously with or on the unknown.
Abstract: Serious attempts are being made to improve the students' preparation for algebra. However, without a clear-cut demarcation between arithmetic and algebra, most of these undertakings merely provide either an earlier introduction of the topic or simply spread it out over a longer period of instruction. The present study investigates the upper limits of the students' informal processes in the solution of first degree equations in one unknown prior to any instruction. The results indicate the existence of acognitive gap between arithmetic and algebra, a cognitive gap that can be characterized asthe students' inability to operate spontaneously with or on the unknown. Furthermore, the study reveals other difficulties of a pre-algebraic nature such as a tendency to detach a numeral from the preceding minus sign in the grouping of numerical terms and problems in the acceptance of the equal symbol to denote a decomposition into a difference as in 23=37−n which leads some students to read such equations from right to left.
359 citations
TL;DR: Pronounced resonances are obtained for the tunneling probability and the conductance of a resonant tunneling device consisting of magnetic barriers created by lithographic patterning of ferromagnetic or superconducting films.
Abstract: New tunneling structures are proposed consisting of magnetic barriers that can be created by lithographic patterning of ferromagnetic or superconducting films. The form of the equivalent potential for such a barrier depends on the wave vector of the incident electron. This renders the transmission through such structures an inherently two-dimensional process since the tunneling probability depends not only on the electron's momentum perpendicular to the tunneling barrier but also on its momentum parallel to the barrier. Pronounced resonances are obtained for the tunneling probability and the conductance of a resonant tunneling device consisting of such magnetic barriers.
347 citations
TL;DR: Differences in personality support the view that 5-HT systems are involved in modulating impulsive and aggressive personality traits and suggest that5-HT neurotoxicity may be a potential complication of MDMA use.
338 citations
TL;DR: The effective dose of DAMGO--both for establishing and for maintaining the lever-press habit--was 100 times lower than the effective doses for DPDPE and morphine, suggesting that the major contribution of VTA mechanisms to intravenous heroin self- administration involves an action on mu-opioid receptors.
Abstract: Intracranial self-administration of mu- and delta-opioid agonists was demonstrated in male Long-Evans rats. Independent groups were allowed to lever-press for ventral tegmental area (VTA) microinfusions of morphine, the selective mu agonist [D-Ala2,N-Me-Phe4-Gly5-ol]- enkephalin (DAMGO), the selective delta-agonist [D-Pen2,D-Pen5]- enkephalin (DPDPE), or ineffective drug vehicle. Morphine, DAMGO, and DPDPE were each effective in establishing and maintaining lever- pressing habits. Lever-pressing responses were extinguished during a session when vehicle was substituted for drug, and reinstated when drug reinforcement was reestablished. Thus, it appears that VTA mu- and delta-opioid receptors are each involved in reinforcement of opiate self-administration. The effective dose of DAMGO--both for establishing and for maintaining the lever-press habit--was 100 times lower than the effective doses for DPDPE and morphine, suggesting that the major contribution of VTA mechanisms to intravenous heroin self- administration involves an action on mu-opioid receptors.
264 citations
TL;DR: In this review the interplay between the genetic analysis and biochemical characterisation of the catabolic pathway is emphasised, and analysis of the sequences of the pathway proteins suggests new approaches to the study of these generally little-characterised enzymes.
Abstract: Pseudomonas sp. strain CF600 is an efficient degrader of phenol and methylsubstituted phenols. These compounds are degraded by the set of enzymes encoded by the plasmid located dmpoperon. The sequences of all the fifteen structural genes required to encode the nine enzymes of the catabolic pathway have been determined and the corresponding proteins have been purified. In this review the interplay between the genetic analysis and biochemical characterisation of the catabolic pathway is emphasised. The first step in the pathway, the conversion of phenol to catechol, is catalysed by a novel multicomponent phenol hydroxylase. Here we summarise similarities of this enzyme with other multicomponent oxygenases, particularly methane monooxygenase (EC 1.14.13.25). The other enzymes encoded by the operon are those of the well-known meta-cleavage pathway for catechol, and include the recently discovered meta-pathway enzyme aldehyde dehydrogenase (acylating) (EC 1.2.1.10). The known properties of these meta-pathway enzymes, and isofunctional enzymes from other aromatic degraders, are summarised. Analysis of the sequences of the pathway proteins, many of which are unique to the meta-pathway, suggests new approaches to the study of these generally little-characterised enzymes. Furthermore, biochemical studies of some of these enzymes suggest that physical associations between meta-pathway enzymes play an important role. In addition to the pathway enzymes, the specific regulator of phenol catabolism, DmpR, and its relationship to the XylR regulator of toluene and xylene catabolism is discussed.
222 citations
TL;DR: The heuristics and techniques used to overcome back-propagation problems, particularly lack of generalization, are identified and outlined, along with areas of potential improvements to the paradigm.
Abstract: In the past few years, neural networks have emerged as a problem-solving technique with capabilities suited to many civil engineering problems. Among the various neural network paradigms available, back-propagation is by far the most utilized for its relatively simple mathematical proofs and good generalization capabilities. Despite its capabilities, back-propagation suffers from several problems that hinder the development of practical neural network applications. These include slow training, ill-defined knowledge representation and problem structuring, and nonguided design of an optimal network configuration for adequate generalization. This paper represents an effort to guide the process of developing practical neural network applications using back-propagation. The paper starts with a brief description of back-propagation mathematics. Some of the heuristics and techniques used to overcome back-propagation problems, particularly lack of generalization, are identified and outlined, along with areas of potential improvements to the paradigm. An application development methodology is proposed utilizing the identified heuristics and techniques. The methodology provides a structured framework for designing and implementing practical neural network applications with less effort.
168 citations
TL;DR: Exosture to mild intermittent stress appeared to enhance the reinforcing efficacy of heroin, and its relation to drug availability may characterize conditions under which stress leads to increased opioid abuse.
Abstract: The effect of a mild footshock on intravenous heroin self-administration was examined in male rats. Animals in the stress condition were exposed to 10 min of intermittent footshock (0.5 mA; 0.5 s on, with a mean off period of 40 s) before each of four daily self-administration sessions. Animals in the control group were not exposed to footshock. Following acquisition of heroin-reinforced behavior (100 micrograms/kg per infusion), during which no group differences emerged, animals were placed on a progressive ratio schedule of reinforcement and were subsequently tested under a decreasing series of doses. Animals exposed to footshock before each drug session had higher rates of lever pressing for heroin and achieved higher final ratios on the progressive ratio schedule than animals in the control group at the higher doses of heroin. Thus, under the conditions of this experiment, exposure to mild intermittent stress appeared to enhance the reinforcing efficacy of heroin. The parameters of footshock used in the present study, and its relation to drug availability may characterize conditions under which stress leads to increased opioid abuse.
167 citations
TL;DR: In this paper, the Hamiltonian structure of the monodromy preserving deformation equations of Jimboet al [JMMS] is explained in terms of parameter dependent pairs of moment maps from a symplectic vector space to the dual spaces of two different loop algebras.
Abstract: The Hamiltonian structure of the monodromy preserving deformation equations of Jimboet al [JMMS] is explained in terms of parameter dependent pairs of moment maps from a symplectic vector space to the dual spaces of two different loop algebras. The nonautonomous Hamiltonian systems generating the deformations are obtained by pulling back spectral invariants on Poisson subspaces consisting of elements that are rational in the loop parameter and identifying the deformation parameters with those determining the moment maps. This construction is shown to lead to “dual” pairs of matrix differential operators whose monodromy is preserved under the same family of deformations. As illustrative examples, involving discrete and continuous reductions, a higher rank generalization of the Hamiltonian equations governing the correlation functions for an impenetrable Bose gas is obtained, as well as dual pairs of isomonodromy representations for the equations of the Painleve transcendentsPV andVI.
156 citations
TL;DR: A robust estimation method with high breakdown point which can tolerate more than 80% of outliers and a substantial improvement over the least median squares method by using histogram approach to inferring residual consensus is presented.
Abstract: This correspondence presents a segmentation and fitting method using a new robust estimation technique. We present a robust estimation method with high breakdown point which can tolerate more than 80% of outliers. The method randomly samples appropriate range image points in the current processing region and solves equations determined by these points for parameters of selected primitive type. From K samples, we choose one set of sample points that determines a best-fit equation for the largest homogeneous surface patch in the region. This choice is made by measuring a residual consensus (RESC), using a compressed histogram method which is effective at various noise levels. After we get the best-fit surface parameters, the surface patch can be segmented from the region and the process is repeated until no pixel left. The method segments the range image into planar and quadratic surfaces. The RESC method is a substantial improvement over the least median squares method by using histogram approach to inferring residual consensus. A genetic algorithm is also incorporated to accelerate the random search. >
TL;DR: In this article, an innovative intensive ESL program in Quebec is described, where some students in grade 5 or grade 6 access to intensive instruction in ESL for 5 months of 1 school year, the students spend virtually full school days engaged in English language activities.
Abstract: An innovative intensive ESL program in Quebec is the focus of this article. As a background to the presentation of research carried out within this program, the context and conditions of ESL teaching in Quebec's French-language schools are briefly described. In these schools, where all subject matter instruction is normally provided in French, the program gives some students in Grade 5 or Grade 6 access to intensive instruction in ESL. For 5 months of 1 school year, the students spend virtually full school days engaged in English language activities. They do not receive subject matter instruction through English but participate in communicative activities and projects whose goal is to develop their ability to understand and speak English. This article reports on the findings of some research in these intensive ESL classes: descriptive studies of patterns of classroom interaction and instruction, the development of fluency and accuracy in learner language, and the long-term effects of the program. In addition, experimental studies have explored the effects of introducing some greater focus on form within or in addition to the communicative activities typical of most of the classes.
TL;DR: In this paper, a new Hebbian-type learning algorithm for the total least squares parameter estimation is presented, which allows the weight vector of a linear neuron unit to converge to the eigenvector associated with the smallest eigenvalue of the correlation matrix of the input signal.
Abstract: In this paper, a new Hebbian-type learning algorithm for the total least-squares parameter estimation is presented. The algorithm is derived from the classical Hebbian rule. An asymptotic analysis is carried out to show that the algorithm allows the weight vector of a linear neuron unit to converge to the eigenvector associated with the smallest eigenvalue of the correlation matrix of the input signal. When the algorithm is applied to solve parameter estimation problems, the converged weights directly yield the total least-squares solution. Since the process of obtaining the estimate is optimal in the total least-squares sense, its noise rejection capability is superior to those of the least-squares-based algorithms. It is shown that the implementations of the proposed algorithm have the simplicity of those of the LMS algorithm. The applicability and performance of the algorithm are demonstrated through computer simulations of adaptive FIR and IIR parameter estimation problems. >
TL;DR: A survey on the techniques and problems involved in automatic knowledge acquisition through document processing is presented, and the basic concept of document structure and its measurement based on entropy analysis is introduced.
Abstract: The knowledge acquisition bottleneck has become the major impediment to the development and application of effective information systems. To remove this bottleneck, new document processing techniques must be introduced to automatically acquire knowledge from various types of documents. By presenting a survey on the techniques and problems involved, this paper aims at serving as a catalyst to stimulate research in automatic knowledge acquisition through document processing. In this study, a document is considered to have two structures: geometric structure and logical structure. These play a key role in the process of the knowledge acquisition, which can be viewed as a process of acquiring the above structures. Extracting the geometric structure from a document refers to document analysis; mapping the geometric structure into logical structure is regarded as document understanding. Both areas are described in this paper, and the basic concept of document structure and its measurement based on entropy analysis is introduced. Logical structure and geometric models are proposed. Both top-down and bottom-up approaches and their entropy analyses are presented. Different techniques are discussed with practical examples. Mapping methods, such as tree transformation, document formatting knowledge and document format description language, are described. >
TL;DR: In this paper, the authors examined project leadership behavior, championing, and effectiveness in 40 research and development (R&D) project groups and found that there is little association between project-level leadership or championing and project effectiveness, however, leadership exhibited at higher organizational levels is significantly correlated with effectiveness.
TL;DR: Shoes with thick-soft soles, similar to modern athletic footwear and 'walking shoes', destabilize men, and shoes with thin-hard soles provide superior stability, which concludes that both athletic performance and public safety could be enhanced through stability optimized footwear.
Abstract: Stable equilibrium during locomotion is required for both superior performance of sports and prevention of injuries from falls. A recent report indicated that currently available athletic footwear impairs stability in older men. Since this discovery, if confirmed, seems important to both competitive athletes and the physically active general public, we performed an experiment using similar methods on a younger population. We tested the hypothesis that midsole thickness is negatively, and hardness positively related to dynamic equilibrium, in 17 healthy adult men (mean(s.d.) age 33(11.13) years) via a balance beam method. Subjects walked along a 9-m long beam at 0.5 m s-1 once barefoot and six times wearing identical pairs of experimental shoes which differed only in midsole hardness and thickness which spanned the respective ranges currently available in footwear. Falls from the beam (balance failures) were quantified. Balance failures varied significantly in relation to midsole hardness and thickness, and there was a strong trend toward interaction of these variables (P = 0.09). Midsole hardness was positively related to stability, and midsole thickness was negatively related, which confirms the previous report. Hence, shoes with thick-soft soles, similar to modern athletic footwear and 'walking shoes', destabilize men, and shoes with thin-hard soles provide superior stability. The pair with the poorest stability (A 15-thick; 12.34 balance failures per 100 m) produced 217% more balance failures than those associated with the best stability (A 50-thin; 3.89 balance failures per 100 m). Since most types of athletic footwear and many other shoes incorporate midsoles with hardness and thickness associated with poor stability, we conclude that both athletic performance and public safety could be enhanced through stability optimized footwear.
TL;DR: It is suggested that spice finches can alter their allocation to each foraging alternative by experience and that the producer-scrounger game is a realistic model for predicting group foraging decisions.
Abstract: Group foraging allows the co-existence of a strategy (producer) that involves searching for food, and its alternative (scrounger) exploiting the food of the producer. The use of producer and scrounger strategies has been modelled as an alternative-option scramble which assumes strong negative frequency-dependence of the scrounger's pay-offs. We tested this assumption in a flock feeding situation by manipulating the proportion of scroungers in flocks of spice finches, Lonchura punctulata. In a first experiment we found that: (1) the food intake of scroungers, and to a lesser extent producers, was negatively affected by an increase in the proportion of scroungers; (2) the food intake of producers and scroungers was equal when the proportion of scroungers was small, suggesting that producers, who exploited 35.4% of their patches by scrounging were opportunistically adjusting their use of the strategies until the pay-offs equalized. In a second experiment we tested whether finches could vary their use of the two strategies in response to changes in foraging conditions brought about by an increase in the cost of producing. As predicted by the game, finches reduced their use of the producer strategy and increased their use of the scrounger strategy when the cost of producing increased. These results suggest that spice finches can alter their allocation to each foraging alternative by experience and that the producer-scrounger game is a realistic model for predicting group foraging decisions.
TL;DR: A procedure for the design of equiripple digital differentiators and Hilbert transformers using a weighted least-squares technique is described, used in conjunction with prediction techniques for the DD and HT lengths to design DDs and HTs, respectively, satisfying prescribed specifications.
Abstract: A procedure for the design of equiripple digital differentiators (DDs) and Hilbert transformers (HTs) using a weighted least-squares technique is described. This procedure involves an iterative algorithm in which the appropriate frequency-dependent weighting function that yields an equiripple design is determined. Our procedure is used in conjunction with prediction techniques for the DD and HT lengths to design DDs and HTs, respectively, satisfying prescribed specifications. >
01 Jan 1994
TL;DR: In this paper, a finite element model of infinitely long track is developed to study the dynamic interactions between the railway vehicle and track, where the track is represented by a Timoshenko beam on discrete pad-tie-ballast supports.
Abstract: To study the dynamic interactions between the railway vehicle and track, a finite element model of infinitely long track is developed. The track is represented by a Timoshenko beam on discrete pad-tie-ballast supports. The non-linear factors such as loss of wheel-rail contact, rail lift-off from the tie and tie lift-off from the ballast are taken into account. A multi-point wheel-rail contact model is also proposed. The dynamic forces on the track and the strains on the rail are directly calculated from the model. The vehicle could travel on the track forever with an arbitrary time-dependent speed. The steady-state response of a vehicle-track system for a perfect wheel carrying a constant load and travelling at a constant speed over a track with no irregularities is studied using the finite element model and is presented. The impact loads due to wheel flats are also studied with this model. The results show a good correlation with the experimental data available in the literature. Influences of system par...
09 Oct 1994
TL;DR: The intention of this research is to analyze the foundations of the majority vote method in order to gain a deeper understanding and new results about its mode of operation.
Abstract: Recently, it has been demonstrated that combining the decisions of several classifiers can lead to improved recognition results. The combination can be implemented using a variety of strategies, among which majority vote is by far the simplest, yet it has been found to be just as effective as more complicated schemes. However, all the results reported thus far on combinations of classifiers have been experimental in nature. The intention of this research is to analyze the foundations of the majority vote method in order to gain a deeper understanding and new results about its mode of operation.
TL;DR: The N-terminal sequence of the 29-kDa and 31-k da proteins demonstrated the closest homologies with internal sequences from anEscherichia coli trigger factor protein (TIG.ECOLI) out of nine other lactobacilli and not with the other species tested.
Abstract: Collagen type-I-binding proteins of Lactobacillus reuteri NCIB 11951 were purified. The cell surface proteins were affinity purified on collagen Sepharose and eluted with an NaCl gradient. Two protein bands were eluted from the column (29 kDa and 31 kDa), and both bound radio-labeled collagen type I. Rabbit antisera raised against the 29 kDa and 31 kDa protein reacted with the affinity-purified proteins in a Western blot with whole-cell extract used as antigen. The N-terminal sequence of the 29-kDa and 31-kDa proteins demonstrated the closest homologies with internal sequences from an Escherichia coli trigger factor protein (TIG.ECOLI). Out of nine other lactobacilli, the antisera reacted only with the L. reuteri and not with the other species tested.
TL;DR: In this article, a simple measure of "enjoyable aspects of caregiving" was used in a large longitudinal Canadian study of dementia care in the community, and the measure attained significant test-retest reliability and significantly correlated with caregiver burden and health.
Abstract: This paper reviews the different concepts and measures of positive aspects of caregiving that have been used in previous studies. It describes the use of a simple measure of “enjoyable aspects of caregiving” used in a large longitudinal Canadian study of dementia care in the community. The measure attained significant test-retest reliability and significantly correlated with caregiver burden and health. It also predicted caregiver desire to institutionalize the care recipient at three different time periods but not actual institutionalization. The paper calls for greater use of measures related to positive aspects of caregiving and a better understanding of how these measures relate to one another and to outcomes.
02 Oct 1994
TL;DR: In this article, two PWM pattern generators for current source converters were investigated, namely the modified dead-band technique and the space vector-based technique, where the advantage is taken of the extra zero state available in current sources.
Abstract: On-line PWM pattern generators for current source converters offer a number of control advantages over off-line optimized patterns. However, when implemented using the principles applying to voltage source inverter PWM pattern generators, the switching frequency is equal to: (a) the carrier frequency in standard carrier-based implementations and to (b) 2/3 the cycle frequency in space vector implementations. This paper shows that this frequency can be reduced to 1/2 of the respective frequencies. Two pattern generators are investigated: (a) a carrier based technique, namely the modified dead-band technique; (b) a space vector based technique, where the advantage is taken of the extra zero state available in current source converters. It is shown that a significant reduction of AC line current distortion is obtained with the modified dead-band technique for modulation indices greater than 0.4. Furthermore, with the two proposed pattern generators, there is no penalty on the distortion of the DC bus voltage. The principles of operation of the proposed schemes are explained. DSP implementation algorithms of the space vector scheme are given. Experimental results on a 5 kVA current rectifier and a 5 kVA current source inverter confirm the feasibility of the proposed pattern generators, and illustrate the input and output frequency spectra obtained. >
TL;DR: Contextual and developmental factors that may Flsult in same-sex peer preferences may be observed among two-year-olds prior to the emergence of gender segregation as a dominant pattern in their playgroups.
Abstract: Contextual and developmental factors that may Flsult in same-sex peer preferences may be observed among two-year-olds prior to the emergence of gender segregation as a dominant pattern in their playgroups.
TL;DR: Personality traits and most other study variables demonstrated significant continuity across time for caregivers continuing home care, while appraising the dependent as more troublesome increased negative outcomes initially.
Abstract: This study tested predictions specifying the influence of caregiver personality traits on negative outcomes of caregiving, health complaints and burden. Two-hundred and thirteen caregivers, who were caring for family members with dementia, were interviewed and their relatives were assessed on cognitive status and aggression. At follow-up conducted twenty-four months later, forty-five caregivers were still continuing to provide home care for their dependents. Caregivers who scored higher on a measure of neuroticism experienced higher levels of burden and health complaints both at initial and follow-up assessment. Caregiver extraversion-introversion did not influence the experience of caregiving. At both initial and final assessment, the ability to enjoy some aspects of caregiving, recreational activities, and satisfaction with social support from family and friends mitigated negative outcomes of caregiving, while appraising the dependent as more troublesome increased negative outcomes. Caring for more cognitively impaired and more aggressive dependents and being female increased negative outcomes initially. Personality traits and most other study variables demonstrated significant continuity across time for caregivers continuing home care.
Journal Article•
TL;DR: The sensitivity to nicotine of the reinforcing actions of both lateral hypothalamic and medial mesencephalic brain stimulation is consistent with evidence that suggests that stimulation at these two sites activates common reinforcement-related brain circuitry.
Abstract: The effects of nicotine (0.025-0.8 mg/kg s.c.) were assessed daily for 10 days on lever pressing maintained by reinforcement of lateral hypothalamic or midline mesencephalic brain stimulation in rats. Similar effects were seen but slightly higher doses were needed with lateral hypothalamic stimulation. With each stimulation site, the lower doses produced parallel leftward shifts in the rate-frequency functions. The higher doses produced sedative effects and cessation of responding in some animals on the first 2 or 3 days of testing but tolerance to this effect was seen. Parallel leftward shifts were produced from day 4 on. Although there was tolerance to the sedative effects, there was neither tolerance nor sensitization to the ability of nicotine to produce leftward shifts in the rate-frequency functions of performing animals. The sensitivity to nicotine of the reinforcing actions of both lateral hypothalamic and medial mesencephalic brain stimulation is consistent with evidence that suggests that stimulation at these two sites activates common reinforcement-related brain circuitry. The fact that nicotine causes parallel leftward shifts in the brain stimulation rate-frequency functions suggests synergism of a nicotinic action with the reinforcing action of the brain stimulation.
Book•
15 Sep 1994TL;DR: Introduction to Networks Queuing Systems and Transport Layer Protocols Switching Techniques and Fast-Packet Switching.
Abstract: Introduction to Networks Queuing Systems The Data Link Layer and X.25 Flow and Congestion Control Multiple Access Communication Protocols Local Area Network Protocols and Standards Transport Layer Protocols Switching Techniques and Fast-Packet Switching.
TL;DR: In this article, the authors proposed macromodels to simulate three-phase power converters on such packages, which are suited for steady state and large signal transient analysis at system level.
Abstract: Static power converters can be analyzed by means of widely available circuit simulation software packages such as PSPICE. However, they are usually modeled as a set of real switches, which results in long execution times and possible convergence problems in the case of complex circuits. This paper proposes macromodels to simulate three-phase power converters on such packages. The proposed macromodels are based on converter switching functions rather than actual circuit configuration, and they are suited for steady state and large signal transient analysis at system level. In this approach, voltage source inverters (VSI), current source inverters (CSI), and controlled rectifiers (CR) are simulated as multiport networks avoiding the physical nonlinear micromodels of the power switches. Computer memory and the run-times required for the simulation are thereby minimized. Complete examples of VSI, CSI and CR, with different PWM techniques, are given with specific reference to the PSPICE software to illustrate the effectiveness of the proposed models. >
TL;DR: The treatment addressed in the chapter stimulates use and exploration of the Kurz approach to analyzing transition state stabilization, and there are some examples involving catalysis by acids and bases, metal ions, micelles, amylose, catalytic antibodies, and enzymes to give an idea about the ways Kurz's approach may be usefully applied to other catalysts.
Abstract: Publisher Summary This chapter describes the stabilization of transition states by cyclodextrins and other catalysts. It deals with a particular aspect of the chemistry of cyclodextrins: the effects that they can have on organic reactions by virtue of their abilities to bind to many organic and inorganic species. The main emphasis of this chapter is on catalysis, because this is of greater interest, the Kurz method can also be applied to retardation. In fact, the smooth transition from retardation, through inactivity, to full catalysis can be quantified and analyzed in relation to the structure of the species concerned. Moreover, there are some examples involving catalysis by acids and bases, metal ions, micelles, amylose, catalytic antibodies, and enzymes to give an idea about the ways Kurz's approach may be usefully applied to other catalysts. This chapter concludes that the treatment addressed in the chapter stimulates use and exploration of the Kurz approach to analyzing transition state stabilization.
TL;DR: Heterogeneous Photocatalysis (HP) has been examined and explored as a potentially viable alternative technology to classical “best” technologies in both environmental detoxification and in energy production as mentioned in this paper.
Abstract: Heterogeneous Photocatalysis (HP) has been examined and explored as a potentially viable alternative technology to classical “best” technologies in both environmental detoxification and in energy production. Both fundamental and applied investigations have been pursued over the last decade (1983–1993). This novel technology employs illuminated semiconductor materials as photocatalysts such as CdS and TiO2 to produce both reducing and highly oxidizing species on the particle surface, poised to unleash redox reactions in aqueous media some of which are not possible by normal chemical means. Our laboratory has been involved in this area and has made a significant contribution in (i) demonstrating the generality of the techniques to mineralize a large variety of environmental organics to carbon dioxide together with disposing of trace and toxic metals from aqueous media, and in (ii) understanding the events taking place initially when the light photons interact with the photocatalysts and later when the mineralization process proceeds to its pathological conclusion(s). In this paper we briefly review some of the salient features of our work in Heterogeneous Photocatalysis over the last decade.