Showing papers by "Florida Atlantic University published in 1994"

Interpersonal conflict during adolescence.

Abstract: Interpersonal conflict is considered within various frameworks of adolescent development. Conflict, defined as behavioral opposition, is distinguished from related constructs. Differences between adolescent relationships and across age groups are reviewed in the incidence and intensity, resolution, and outcome of conflict. Influences of setting on conflict behaviors and effects are emphasized. The evidence does not reveal dramatic shifts in conflict behavior as a function of age or maturation. Consistent differences do emerge, however, when adolescent relationships and conflict settings are considered. It is argued that a social relational model based on principles of interdependence and equity provides an alternative to psychoanalytic, sociobiological, and cognitive-developmental accounts of conflict behavior during adolescence.

A Reexamination of Auditor versus Model Accuracy within the Context of the Going-Concern Opinion Decision*

Abstract: . The Cohen Commission and previous research have suggested that auditors' opinions are inferior indicators of bankruptcy relative to the predictions of statistical models. This research reexamines this question in light of two important considerations that make the comparison between audit opinions and model predictions considerably more reflective of the auditors' real-world decision environment. First, the sample is partitioned into stressed and nonstressed observations and the importance of doing so is demonstrated; second, the statistical models and the forecast errors are adjusted so that they reflect the proportion of bankrupt firms actually faced by auditors. The empirical results provide convincing evidence suggesting that the notion established in previous research that auditors' opinions are interior to models in predicting bankruptcy is unfounded. It should be noted, however, that neither the auditors' opinions nor the bankruptcy prediction model are very good predictors of bankruptcy when population proportions, differences in misclassification costs, and financial stress levels are considered. Resume. Les travaux de recherche de la Commission Cohen et d'autres travaux qui les ont precedes semblent indiquer que les opinions des verificateurs sont des indicateurs de faillite moins efficaces que les predictions des modeles statistiques. Les auteurs se penchent a leur tour sur cette question, a la lumiere de deux elements importants qui font en sorte que la comparaison entre les opinions des verificateurs et les modeles previsionnels s'inscrit beaucoup plus dans le contexte decisionnel veritable dans lequel travaillent les verificateurs. D'abord, l'echantillon est scinde en deux groupes d'observations selon la presence ou l'absence de contrainte financiere, partage dont les auteurs expliquent l'importance; ensuite, les modeles statistiques et les erreurs previsionnelles sont ajustes de maniere & refleter la proportion des societes dont la faillite a ete envisagee par le verificateur. Les resultats empiriques demontrent de facon probante que les conclusions tirees des travaux precedents selon lesquelles les opinions des verificateurs sont moins efficaces que les modeles en matiere de prevision des faillites ne sont pas fondees. Il convient de noter, cependant, que ni les opinions des verificateurs ni les modeles previsionnels ne sont des predicteurs tres efficaces des faillites si l'on tient compte des proportions de la population, des differences dans le cout des erreurs de classification et du niveau de contrainte financiere.

Empathy as a cognitive inhibitor of interpersonal aggression

Abstract: The studies presented in this paper examined empathy, especially perspective taking, as a potential inhibitor of interpersonal aggression. The theoretical rationale for these investigations derived from Zillmann's [(1988): Aggressive Behavior 14: 51–64] cognitive excitation model. Study 1 revealed that dispositional empathy correlates negatively with self-reported aggression and with conflict responses that reflect little concern for the needs of the other party. Empathy also was positively related to constructive responses to interpersonal conflict (i. e., those that do involve concern for the needs of the other party). In Study 2, perspective taking was manipulated with instructions to subjects prior to participation in a reaction-time task designed to measure aggression. When threat was relatively low, subjects who were instructed to take the perspective of the target responded less aggressively than did those who had been instructed to focus on the task. Study 3 examined the effect of dispositional perspective taking on verbal aggression. Threat was manipulated in terms of the combination of provocation and gender of the interactants. As predicted, perspective taking related to aggression inhibition under conditions of moderate threat–for males under low provocation and females under high provocation. These effects were predicted and explained in the context of the cognitive-excitation model. © 1994 Wiley-Liss, Inc.

Characterization of neurons of the supramammillary nucleus and mammillary body that discharge rhythmically with the hippocampal theta rhythm in the rat

Abstract: We examined the activity of single cells of the supramammillary nucleus (SUM), the mammillary body (MB), and adjacent regions of the diencephalon with respect to the hippocampal electroencephalogram (EEG) in urethane-anesthetized rats. Twenty-nine of 170 cells were found to discharge synchronously with the theta rhythm of the hippocampus (theta-related neurons). All of the 29 theta-related cells were localized to the SUM or MB. A subset of theta-related cells of SUM and MB discharged in short-duration bursts comparable to the pyramidal complex spike cells of the hippocampus. In contrast to hippocampal complex spikes, however, which predominantly exhibit this mode of firing during non-theta states, the burst firing of SUM/MB cells was strongly correlated with the theta rhythm. The proportion of bursting neurons was higher in MB than in SUM. Using partial coherence analysis, we examined the relationship between SUM/MB theta-related cells and the two generators of theta of the dorsal hippocampus. The theta-related cells of MB showed a stronger correlation with "CA1" than with "dentate" theta, whereas no such asymmetry was found in the relationship between neuronal firing of SUM cells and the two generators of theta in the hippocampus. The foregoing suggests that the theta-related cells of MB are driven by descending projections from the hippocampal formation (CA1), whereas those of the SUM are not. The SUM and MB are intimately connected with the hippocampal formation--the SUM mainly via ascending projections to the dentate gyrus, and the MB via direct descending projections from the subiculum. Theta-related SUM/MB cells may be directly involved in the generation of theta and/or the transfer of theta rhythmicity to various parts of the limbic system and forebrain.

Simultaneous robot/world and tool/flange calibration by solving homogeneous transformation equations of the form AX=YB

Abstract: The paper presents a linear solution that allows a simultaneous computation of the transformations from robot world to robot base and from robot tool to robot flange coordinate frames. The flange frame is defined on the mounting surface of the end-effector. It is assumed that the robot geometry, i.e., the transformation from the robot base frame to the robot flange frame, is known with sufficient accuracy, and that robot end-effector poses are measured. The solution has applications to accurately locating a robot with respect to a reference frame, and a robot sensor with respect to a robot end-effector. The identification problem is cast as solving a system of homogeneous transformation equations of the form A/sub i/X=YB/sub i/,i=1, 2, ..., m. Quaternion algebra is applied to derive explicit linear solutions for X and Y provided that three robot pose measurements are available. Necessary and sufficient conditions for the uniqueness of the solution are stated. Computationally, the resulting solution algorithm is noniterative, fast and robust. >

Projections of the dorsal raphe nucleus to the brainstem: PHA‐L analysis in the rat

Abstract: Early studies that used older tracing techniques reported exceedingly few projections from the dorsal raphe nucleus (DR) to the brainstem. The present report examined DR projections to the brainstem by use of the anterograde anatomical tracer Phaseolus vulgaris leucoagglutinin (PHA-L). DR fibers were found to terminate relatively substantially in several structures of the midbrain, pons, and medulla. The following pontine and midbrain nuclei receive moderate to dense projections from the DR: pontomesencephalic central gray, mesencephalic reticular formation, pedunculopontine tegmental nucleus, medial and lateral parabrachial nuclei, nucleus pontis oralis, nucleus pontis caudalis, locus coeruleus, laterodorsal tegmental nucleus, and raphe nuclei, including the central linear nucleus, median raphe nucleus, and raphe pontis. The following nuclei of the medulla receive moderately dense projections from the DR: nucleus gigantocellularis, nucleus raphe magnus, nucleus raphe obscurus, facial nucleus, nucleus gigantocellularis-pars alpha, and the rostral ventrolateral medullary area. DR fibers project lightly to nucleus cuneiformis, nucleus prepositus hypoglossi, nucleus paragigantocellularis, nucleus reticularis ventralis, and hypoglossal nucleus. Some differences were observed in projections from rostral and caudal parts of the DR. The major difference was that fibers from the rostral DR distribute more widely and heavily than do those from the caudal DR to structures of the medulla, including raphe magnus and obscurus, nucleus gigantocellularis-pars alpha, nucleus paragigantocellularis, facial nucleus, and the rostral ventrolateral medullary area. A role for the dorsal raphe nucleus in several brainstem controlled functions is discussed, including REM sleep and its events, nociception, and sensory motor control.

The nonlinear dynamics of speech categorization.

Abstract: Little is known about the processes underlying the nonlinear relationship between acoustics and speech perception. In Experiment 1, we explored the effects of systematic variation of a single acoustic parameter (silent gap duration between a natural utterance of s and a synthetic vowel ay) on judgements of speech category. The resulting shifts in category boundary between say and stay showed rich dynamics, including hysteresis, contrast, and critical boundary effects. We propose a dynamical model to account for the observed patterns. Experiment 2 evaluated one prediction of the model, that changing the relative stability of the two percepts allows categorical switching. In agreement with the model; an increase in the number of stimulus repetitions maximized the frequency of judgments of category change near the boundary. Thus, a dynamical approach affords the rudiments for a theory of the effects of temporal context on speech categorization.

Multimedia systems: an overview

Abstract: Advances in distributed multimedia systems have begun to significantly affect the development of on-demand multimedia services. Researchers are working within established computer areas to transform existing technologies and develop new ones. Multimedia is shown as the merging of computing, communications, and broadcasting. >

Measuring emergent social phenomena: Dynamism, polarization, and clustering as order parameters of social systems.

Abstract: We derive three system order parameters: dynamism, polarization, and clustering, to describe global states of attitude distribution and change for human social systems. Dynamism (f) captures the rate of change in a system, while polarization (Pt) refers to the increase or decrease of a minority position over time. Clustering (e) defines the spatial segregation of opinion based on system topography. These measures suggest a conception of human systems rooted in time and space that is distinct from other approaches. Their utility is illustrated through computer simulations showing that under a wide variety of circumstances, social influence models incorporating spatial distributions lead to unexpected outcomes of incomplete polarization and clustering, with alternative theories of how individuals encode information leading to quantitatively distinct results. A second set of simulations describes the intrusion of temperature, or unexplained randomness into these systems. Surprisingly, the self-organizational tendencies emerging from the iteration of simple laws of individual attitude change derived from Latane's (1981) metatheory of social impact appear to increase with moderate levels of randomness. We consider other approaches for measuring group level processes, among them network analysis-inspired indices and spatial autocorrelation, and suggest how our system order parameters could be used to predict political elections.

Workspace evaluation of Stewart platforms

Abstract: The workspace and the dexterity of a Stewart platform are affected by the choice of its major dimensions, actuator stroke and the kinematic constraints of its joints An investigation of the effects of these parameters on workspace volume of the platform is presented The obtained results were normalized so that they could be used as a design tool for the selection of dimensions, joints and actuators

A theoretical model of phase transitions in the human brain.

Abstract: An experiment using a multisensor SQUID (superconducting quantum interference device) array was performed by Kelso and colleagues (1992) which combined information from three different sources: perception, motor response, and brain signals. When an acoustic stimulus frequency is changed systematically, a spontaneous transition in coordination occurs at a critical frequency in both motor behavior and brain signals. Qualitatively analogous transitions are known for physical and biological systems such as changes in the coordination of human hand movements (Kelso 1981, 1984). In this paper we develop a theoretical model based on methods from the interdisciplinary field of synergetics (Haken 1983, 1987) and nonlinear oscillator theory that reproduces the main experimental features very well and suggests a formulation of a fundamental biophysical coupling.

The midline posterior hypothalamic region comprises a critical part of the ascending brainstem hippocampal synchronizing pathway

Abstract: Electrical stimulation and microinfusion techniques were utilized in acute experiments on urethane-anesthetized rats in order to evaluate the hypothesis that the posterior hypothalamic and supramammillary nuclei comprise a critical part of the ascending brainstem pathway for producing synchronous hippocampal formation (HPC) field activity (theta). Given confirmation of this hypothesis a second objective was to determine the nature of the contribution made by this midline posterior hypothalamic region (PH) to the frequency and amplitude components of HPC theta field activity. The cholinergic nature of the ascending pathway was also examined. Reversible inactivation of the PH was achieved by microinfusion of the local anesthetic procaine hydrochloride. The efficacy of and recovery from procaine inactivation of the PH was quantitatively analyzed either by electrical stimulation of the nucleus pontis oralis (PO) (two experiments) or the PH (four experiments). The results are summarized under the following three headings: (1) The first is the effect of procaine inactivation of the PH on HPC theta elicited caudal to, at the level of, or rostral to the PH. All HPC theta induced caudal to the PH (spontaneous theta, tail pinch-induced theta, and theta produced by electrical stimulation of the PO) was totally abolished for a minimum 10-min period. HPC theta induced rostral to the PH by the intrahippocampal infusion of carbachol was unaffected, while HPC theta induced by infusions of carbachol into either the medial septum (MS) or PH was reduced in amplitude with no effect on frequency. (2) Next are comparisons of pre- and post-PH procaine trials of electrical stimulation of the PO and PH. In all experiments, regardless of the anatomical locus or technique used to induce HPC theta, pre-and post-PH procaine comparisons of the PO and PH stimulation trials revealed that frequency modulation of HPC theta recovered significantly more slowly than amplitude. (3) Last is the effect of electrical stimulation of the PO and PH on HPC theta induced by carbachol infusions at the level of the HPC, MS, or PH. In all experiments, electrical stimulation of both the PO and PH, at appropriate intensities, resulted in increasing HPC theta frequencies above the frequency induced by the infusion of carbachol into the HPC, MS, and PH. In addition, the post-carbachol HPC theta frequencies induced by electrical stimulation were significantly higher than those produced in the pre-carbachol conditions. The data supported the following conclusions: (1) The PH region (posterior hypothalamic and supramammillary nuclei) comprises a critical part of the ascending brainstem pathway for producing HPC theta field activity. Inputs ascending from the brainstem caudal to the PH contribute primarily to the frequency of HPC theta and secondarily to the amplitude of HPC theta; (2) a portion of the neural components of the ascending brainstem pathway, up to and including the HPC, are cholinergic, cholinoceptive, or both. © 1994 Wiley-Liss, Inc.

Nonprobabilistic, convex-theoretic modeling of scatter in material properties

Abstract: Nonprobabilistic, convex modeling of uncertain material properties for viscoelastic structures is developed in this paper. In particular, the problem of forced vibrations of viscoelastic beams is studied. First the analytic solution by Inman is generalized for a deterministic set of variables, describing material properties. Next, these variables are treated as varying in a solid "ball" in the four-dimensional space, thus modeling the scatter in material properties. The least favorable response needed for the design of the structure is determined.

Elementary Coordination Dynamics

Abstract: Publisher Summary This chapter discusses elementary coordination dynamics that contain no coordination, absolute coordination, and relative coordination. For coordination to be functional, it must adapt and change over time according to external or internal conditions. Basic laws of coordination are not structure specific or dependent on physicochemical processes per se. The theoretical strategy is to map empirically stable patterns of coordination on to attractors of the collective variable dynamics. Transitions between regimes add rich behavioral complexity and are an expression of the principle of self-organization. The existence of a small set of bifurcation structures argues strongly for cooperative effects that simplify the control problem in multidegree-of-freedom systems. The collective dynamics can be derived from the component level where the various coordination patterns arise as self-organized states because of nonlinear coupling among the components involved.

Sex determination from the tibia: standards for contemporary Japan

Abstract: It is vital that skeletal biologists and forensic anthropologists observe populations over time so that changes can be detected and monitored. The purpose of this study is to determine if temporal changes are manifest in the skeleton and, if so, develop appropriate standards to determine sex from the tibia in the contemporary inhabitants of Japan. Osteometric data were obtained from 84 recent Japanese skeletons located at Jikei Medical University, Tokyo. The collection was assembled from the anatomy dissecting room between 1960-1970. With a mean age of about 56 years for males and 51 for females, this sample represents individuals who lived through WWII. Seven tibial measurements were taken and subjected to SPSS-X discriminant function analysis. Results indicated that proximal and distal breadth measurements were selected by the stepwise procedure as the most discriminating. In addition, a number of combinations of measurements were used to develop formulae that would be suitable for fragmentary bones. Average prediction accuracy ranged from 80% from minimum shaft circumference to 89% with proximal epiphyseal breadth. Classification accuracy was higher in males (96%) than in females (79%). Compared with earlier studies of the Japanese, Jikei tibiae are longer, especially in females and thus exhibit less sexual dimorphism. The present research provides new standards that better reflect the Japanese people of today. Furthermore, unlike earlier length based formulae, these results allow sexing from fragmentary bones.

A model for evaluation and administration of security in object-oriented databases

Abstract: The integration of object-oriented programming concepts with databases is one of the most significant advances in the evolution of database systems. Many aspects of such a combination have been studied, but there are few models to provide security for this richly structured information. We develop an authorization model for object-oriented databases. This model consists of a set of policies, a structure for authorization rules, and algorithms to evaluate access requests against the authorization rules. User access policies are based on the concept of inherited authorization applied along the class structure hierarchy. We propose also a set of administrative policies that allow the control of user access and its decentralization. Finally, we study the effect of class structuring changes on authorization. >

The Coordination Dynamics of Learning: Theoretical Structure and Experimental Agenda

Abstract: Publisher Summary This chapter presents a research agenda that could lead to the experimental verification of explicit theoretical predictions regarding the dynamics of the learning process itself. Learning, development, and evolution are separate fields that are studied largely in isolation of each other. Learning, though central to psychology and biology, remains a concept characterized by a variety of definitions, approaches, theories, and experimental methods. It occurs as specific modifications of the coordination dynamics in the direction of the behavioral pattern to be learned. Theoretically, the degree of competition between learning requirements and coordination dynamics determines the rate of learning. The present approach to learning as a pattern-formation process in complex systems stems from the concepts of self-organization in nonequilibrium systems, and it uses the tools of nonlinear dynamical systems. The chapter discusses the dynamical mechanisms and principles in the case of learning that are independent of the characteristic level of description, time scale, and substrate of the phenomenon under investigation.

Long-term valuation effects of bank acquisitions

Abstract: This study measures the abnormal performance of banks subsequent to their acquisitions of other banks. We find a strong negative share price reaction following the acquisition, which tends to continue over a 36-month period. The results suggest that banks generally do not realize the potential benefits from acquisitions, or that any advantages are offset. The long-run valuation effects across the acquiring banks were found to be more favorable for banks that (1) made acquisitions within their existing markets, (2) experienced relatively poor pre-acquisition performance, and (3) had relatively low pre-acquisition growth.

Flexible Manufacturing Systems: An Overview

Abstract: Global competition has made it necessary for many firms to introduce such advanced technologies as Flexible Manufacturing Systems (FMS). However, the extent of such technology applications varies from industry to industry and has met various degrees of success. Reviews the impetus for the introduction of FMS and the conceptual aspects of such systems. Analyses the state of research on FMS, explores problems faced by the firms in implementing FMS and discusses the benefits ensuing from successful implementation of FMS. Includes a relatively extensive bibliography.

Extrinsic modulation of medial septal cell discharges by the ascending brainstem hippocampal synchronizing pathway.

Abstract: Single cells or simultaneously recorded cell pairs in the medial septum (MS) vertical limb of the diagonal band of Broca (vDBB) in the urethane-anesthetized rat were initially classified as either theta-on or non-related according to the system of Colom and Bland (1987, Brain Res 422:277-286) Subgroups of these cells were then studied under various test conditions that included electrical stimulation of the nucleus pontis oralis (PO) or posterior hypothalamus (PH), microinfusion of carbachol into the PO or PH, and the microinfusion of atropine sulfate or procaine hydrochloride into the PH Electrical stimulation of either the PO or PH induced theta (theta) activity in the hippocampal formation (HPC), and electrical stimulation of the PO resulted in a simultaneous increase in the discharge rate of all MS/vDBB theta-on cells tested, compared to the rates recorded during HPC large-amplitude irregular activity (LIA) Five of the MS/vDBB theta-on cells were tested consecutively with electrical stimulation of the PO and PH, and were shown to be activated in a similar manner in either condition Microinfusion of carbachol into either the PO or PH resulted in the induction of HPC theta field activity and the simultaneous intense activation of all MS/vDBB theta-on cells tested Following the microinfusion of either atropine sulfate or procaine into the PH, electrical stimulation of the PO failed to induce HPC theta field activity or the concomitant rhythmic discharges of all MS/vDBB phasic theta-on cells tested Microinfusing procaine into the PH also abolished the coupling between all MS/vDBB cell pairs during HPC theta field activity including that between two cell pairs that were coupled during HPC LIA The data support the following conclusions: 1) The brainstem HPC synchronizing pathway originating in the pons region ascends to the medial septum via the midline posterior hypothalamic region; 2) the present results taken together with previous work suggest that a major component of the ascending synchronizing pathway, up to and including the hippocampal formation, is cholinergic, cholinoceptive, or both, and the receptors involved are primarily muscarinic; 3) the midline posterior hypothalamic region is an important source of inputs to the medial septum and their major contribution is to provide frequency-coded inputs to the MS/vDBB for relay into the hippocampal formation

Non-linear buckling of a column with initial imperfection via stochastic and non-stochastic convex models

Abstract: Buckling of initial imperfection sensitive structure — column on a non-linear elastic foundation — is investigated. A criterion based on the concept of “modal buckling load” is proposed to determine which modes should be included in the analysis when the weighted residuals method is utilized to calculate the limit load — maximum load the structure can support — for a given initial deflection. For stochastic analysis, a random field model is suggested for the uncertain initial imperfection, and Monte Carlo simulations are performed to obtain the probability density of the buckling load and the reliability of the column. Finally, a non-stochastic convex model of uncertainty is employed to describe a situation when only limited information is available on uncertain initial deflection, and the minimum buckling load is obtained for this model. The results from both the stochastic and the non-stochastic approaches are derived and critically contrasted.

Optimal selection of measurement configurations for robot calibration using simulated annealing

Abstract: Measuring robot positions and orientations is a crucial step in a robot calibration process. Off-line optimal selection of measurement configurations can significantly improve the accuracy of kinematic identification. Since the dimension of the parameter space is very large and the cost function is highly nonlinear, this selection process could be well beyond the capacity of today's computers if a global optimal solution is sought by an exhaustive search. On the other hand, gradient-based algorithms are often trapped into local minima. A simulated annealing (SA) approach is adopted in this paper to obtain optimal or near optimal measurement configurations for robot calibration. Simulated annealing is capable of overcoming local minimum points. It is also very convenient for the inclusion of joint travel limits. The SA algorithm is costly computationally; however, since optimal configuration selection can be performed off-line, this may not be a serious problem. To accelerate the convergence rate, a suitable cooling schedule is devised. Practical implementation considerations are discussed. Experimental results are presented to demonstrate the feasibility of the proposed approach. >