bluuebunny/crossref_metadata_2025 huggingface dataset:
GM-CSF Regulates Pulmonary Surfactant Homeostasis and Alveolar Macrophage-Mediated Innate Host Defense
Authors: Trapnell Bruce C. , Whitsett Jeffrey A.
Published: July 2002

▪ Abstract  Recent studies in transgenic mice have revealed important insights into the roles of GM-CSF in regulation of surfactant homeostasis and lung host defense. Interruption of the GM-CSF signaling pathway by targeted ablation of the GM-CSF gene or its receptor (GM−/−or GM Rβc−/−mice, respectively) resulted in pulmonary alveolar proteinosis (PAP) but no hematologic abnormalities. Alveolar macrophages from GM−/−mice have reduced capacity for surfactant catabolism, cell adhesion, phagocytosis, bacterial killing, Toll-receptor signaling, and expression of various pathogen-associated molecular pattern recognition receptors, suggesting arrest at an early stage of differentiation. PAP and abnormalities of alveolar macrophage function were corrected by local expression of GM-CSF in the lung, and expression of the transcription factor PU.1 in alveolar macrophages of GM−/−mice rescued most defects. Recently, a strong association of auto-antibodies to GM-CSF or GM-CSF receptor gene mutations with PAP has implicated GM-CSF signaling abnormalities in the pathogenesis of PAP in humans. Together, these observations demonstrate that GM-CSF has a critical role in regulation of surfactant homeostasis and alveolar macrophage innate immune functions in the lung.
Toward a Psychology of Memory Accuracy
Authors: Koriat Asher , Goldsmith Morris , Pansky Ainat
Published: July 2002

There has been unprecedented interest in recent years in questions pertaining to accuracy and distortion in memory. This interest, catalyzed in part by real-life problems, marks a significant departure from the quantity-oriented approach that has characterized much of traditional memory research. We outline a correspondence metaphor of memory underlying accuracy-oriented research, and show how the features of this metaphor are manifested across the disparate bodies of research reviewed here. These include work in the Gestalt tradition, spatial memory, memory for gist, schema theory, source monitoring, fluency misattributions, false recall and recognition, postevent misinformation, false memories, eyewitness research, and autobiographical memory. In examining the dynamics of memory accuracy, we highlight the importance of metacognitive monitoring and control processes. We end by discussing some of the methodological, theoretical, and metatheoretical issues inherent in accuracy-oriented research, attempting to prepare the groundwork for a more coherent psychology of memory accuracy.
MANAGED CARE DATA AND PUBLIC HEALTH: The Experience of Group Health Cooperative of Puget Sound
Authors: Fishman Paul A. , Wagner Edward H.
Published: July 2002

▪ Abstract  Traditional group and staff model HMOs have contributed to public health investigations for decades. HMOs offer several advantages for this type of research because of their defined population and provider groups and the integrated nature of care delivery in these organizations. Traditional HMOs have also made investments in sophisticated data systems to support evidence-based care that is supported by high-quality clinical data available in automated information systems. This paper reviews why traditional HMOs are ideal places to conduct public health research and analyzes how recent market trends may threaten this role for managed care.
Epidemiology and Prevention of Injuries Among Adolescent Workers in the United States
Authors: Runyan Carol W. , Zakocs Ronda C.
Published: July 2002

▪ Abstract  In the United States, most adolescents are employed at some time during their teen years. Provisions of the Fair Labor Standards Act, the nation's child labor law, address some of the risks of adolescent employment; however, >70 teenage workers are estimated to die from work-related injuries each year, with greater risk among males, whites, and older adolescents. Furthermore, the nonfatal work-related injuries of the ≥64,000 teens who receive emergency department care each year are believed to significantly undercount actual injuries. Many of these nonfatal injuries are severe, with 15%–45% leading to work restriction or permanent disabilities. Significant methodological issues limit the ability of existing surveillance systems to monitor youth worker injury. Risk factor and intervention research is very limited, but does suggest the role of some worker characteristics, management practices, and training issues. However, these factors need more careful study. This review considers existing information about occupational injuries among adolescents and identifies needs for research and policy attention.
IS SOUTH AFRICA DIFFERENT? Sociological Comparisons and Theoretical Contributions from the Land of Apartheid
Authors: Seidman Gay
Published: July 2002

▪ Abstract  For most of the past 50 years, South Africa served as the outlier in sociological discussions of racial inequality: From the late 1940s, when most of the world was moving away from strict racial classification and segregation, apartheid provided social scientists with their most extreme example of the dynamics of racial segregation and exclusion.Yet while apartheid South Africa was unique, social scientists have also used it in comparative studies to explore the underlying dynamics of racial capitalism: Insights from South Africa have offered sociologists new ways to think about migrant labor; the construction of ethnicity; racial exclusion and colonial relationships; relationships between business, white workers and capitalist states; and oppositional social movements. With the end of legal apartheid, South Africa is poised to move into a new position in the annals of social science. From being an outlier, it is increasingly used an an exemplar, in discussions of democratic transitions, development strategies and globalization, and post-colonial transformations. Still to come, perhaps, are comparative studies that draw on insights from other parts of the world to re-examine aspects of South African society that have been left relatively unexplored—ironically including issues around racial identities and changing patterns of race relations as South Africa constructs a new non-racial democracy.
Intimomedial Interface Damage and Adventitial Inflammation Is Increased Beneath Disrupted Atherosclerosis in the Aorta
Authors: Moreno Pedro R. , Purushothaman K. Raman , Fuster Valentin , O’Connor William N.
Published: July 2002

Background

—

Atherosclerotic plaque progression is frequently accompanied by compensatory enlargement to preserve the lumen. These enlarging plaques develop features of vulnerability, however, leading to disruption and lumen obstruction. This complex transition from compensatory expansion to plaque disruption may not derive solely from progressive intimal disease. Concurrent changes at the intimomedial interface and within the tunica media and adventitia may play a role in plaque instability. We tested this hypothesis by investigating whether interface changes, including internal elastic lamina (IEL) rupture, and medial and adventitial changes, including inflammation, fibrosis, and atrophy, more frequently accompany disrupted than nondisrupted atherosclerotic plaques.

Methods and Results

—

Computerized planimetry and ocular micrometry were used for systematic quantification of intimal, medial, and adventitial histopathological features in 598 human aortic plaques according to the AHA classification. Disrupted plaques exhibited larger plaque and lipid pool areas (
P
=0.0001) and a higher incidence of rupture of the IEL (
P
=0.0001). Medial and adventitial inflammation (
P
=0.01), medial fibrosis (
P
=0.0001), and medial atrophy (
P
=0.0001) were also higher in disrupted plaques. Furthermore, medial thickness was reduced in disrupted plaques (
P
=0.0001). Logistic regression analysis identified rupture of the IEL as an independent predictor for fibrous cap disruption (
P
=0.0001).

Conclusions

—

Compared with nondisrupted plaques, disrupted plaques have an increased incidence of IEL rupture, medial and adventitial inflammation, medial fibrosis, and medial atrophy. These intimomedial interface and adventitial changes may play a role in the natural history of complex atherosclerotic lesions. The interaction between medial and adventitial pathology and the intimal atherosclerotic process deserves further investigation.
Plasma Vitamin C Modifies the Association Between Hypertension and Risk of Stroke
Authors: Kurl S. , Tuomainen T.P. , Laukkanen J.A. , Nyyssönen K. , Lakka T. , Sivenius J. , Salonen J.T.
Published: July 2002

Background and Purpose

—

There are no prospective studies to determine whether plasma vitamin C modifies the risk of stroke among hypertensive and overweight individuals. We sought to examine whether plasma vitamin C modifies the association between overweight and hypertension and the risk of stroke in middle-aged men from eastern Finland.

Methods

—

We conducted a 10.4-year prospective population-based cohort study of 2419 randomly selected middle-aged men (42 to 60 years) with no history of stroke at baseline examination. A total of 120 men developed a stroke, of which 96 were ischemic and 24 hemorrhagic strokes.

Results

—

Men with the lowest levels of plasma vitamin C (<28.4 μmol/L, lowest quarter) had a 2.4-fold (95% CI, 1.4 to 4.3;
P
=0.002) risk of any stroke compared with men with highest levels of plasma vitamin C (>64.96 μmol/L, highest quarter) after adjustment for age and examination months. An additional adjustment for body mass index, systolic blood pressure, smoking, alcohol consumption, serum total cholesterol, diabetes, and exercise-induced myocardial ischemia attenuated the association marginally (relative risk, 2.1; 95% CI, 1.2 to 3.8;
P
=0.01). Adjustment for prevalent coronary heart disease and atrial fibrillation did not attenuate the association any further. Furthermore, hypertensive men with the lowest vitamin C levels (<28.4 μmol/L) had a 2.6-fold risk (95% CI, 1.52 to 4.48;
P
<0.001), and overweight men (≥25 kg/m
2
) with low plasma vitamin C had a 2.7-fold risk (95% CI, 1.48 to 4.90;
P
=0.001) for any stroke after adjustment for age, examination months, and other risk factors.

Conclusions

—

Low plasma vitamin C was associated with increased risk of stroke, especially among hypertensive and overweight men.
Computed Tomographic Findings in Patients Undergoing Intra-arterial Thrombolysis for Acute Ischemic Stroke due to Middle Cerebral Artery Occlusion
Authors: Roberts Heidi C. , Dillon William P. , Furlan Anthony J. , Wechsler Lawrence R. , Rowley Howard A. , Fischbein Nancy J. , Higashida Randall T. , Kase Carlos , Schulz Gregory A. , Lu Ying , Firszt Carolyn M.
Published: July 2002

Background and Purpose

—

The purpose of this study was to evaluate the role of noncontrast CT in the selection of patients to receive thrombolytic therapy for acute ischemic stroke and to predict radiological and clinical outcomes.

Methods

—

One hundred eighty patients with stroke due to middle cerebral artery (MCA) occlusion were randomized 2:1 within 6 hours of onset to receive intra-arterial recombinant prourokinase plus intravenous heparin or intravenous heparin only. Four hundred fifty-four CT examinations were digitized to calculate early infarct changes, infarct volumes, and hemorrhagic changes among the 162 patients treated as randomized (108 recombinant prourokinase–treated patients and 54 control patients). CT changes were correlated with baseline stroke severity, angiographic clot location, collateral vessels, and outcome at 90 days.

Results

—

Baseline CT scans, 120 (75%) of 159, showed early infarct–related abnormalities. The baseline CT abnormality volume was not correlated with the baseline National Institutes of Health Stroke Scale (NIHSS) score (
r
=−0.11) but was correlated weakly with the outcome (
r
=0.17,
P
<0.05). Compared with patients with M2 occlusions, patients with M1 MCA occlusions had significantly higher baseline NIHSS scores (
P
<0.05), more basal ganglia involvement on CT, and larger hypodensity volumes on follow-up CTs. Compared with patients with partial or no collateral supply, patients with full collateral supply had lower baseline NIHSS scores, significantly smaller baseline CT infarct volumes, and less cortical involvement (
P
<0.05).

Conclusions

—

Noncontrast CT is not correlated with baseline stroke severity and does not predict outcome in patients with stroke due to MCA occlusion. However, baseline CT changes, clinical presentation, and the evolution of CT changes are influenced by clot location and the presence of a collateral supply.
The Abstract Organism: Towards a Prehistory for A-Life Art
Authors: Whitelaw Mitchell
Published: July 2002

The author examines historical precedents for contemporary art practice using artificial life, in particular in the work of Paul Klee and Kasimir Malevich. Similarities are identified between artificial life and the philosophical tradition of organicism; specific examples from Klee and Malevich indicate that those artists were engaged in a form of creative organicist thought that imagined the realization of living structures in artificial media.
Leonardo da Vinci's Struggles with Representations of Reality
Authors: Wade Nicholas J. , Ono Hiroshi , Lillakas Linda
Published: July 2002

Virtual reality systems seek to simulate real scenes so that they will be seen as three-dimensional. The issues at the heart of virtual reality are old ones. Leonardo da Vinci struggled with the differences between the perception of a scene and a painting of it, which he reduced to the differences between binocular and monocular vision. He could not produce on canvas what, in the terminology of Ames, was an equivalent configuration. This was provided 300 years after Leonardo by Wheatstone's stereoscope. Modern approaches to virtual reality that can incorporate moving viewpoints would have fascinated Leonardo
The Community Is Watching, and Replying: Art in Public Places and Spaces
Authors: Bray Anne
Published: July 2002

The author describes her public-art projects and installa-tions, in which she has em-ployed various combinations of video, photography, audio, sculpture and performance, often in collaboration with artist Molly Cleator. The pieces spectacularize unresolved conflicts between the artists regarding what is personally truthful as compared to what society dictates, especially concerning the “three deviants”: women, art and nature. The artists question who defines these related realities and how. The author has also offered hundreds of artists a forum called L.A. Freewaves, a media arts organization and festival working in traditional and nontraditional venues throughout Los Angeles, in an effort to disseminate community-empowering public art widely.
The Emptiness of the Lexicon: Reflections on James Pustejovsky's The Generative Lexicon
Authors: Fodor Jerry A. , Lepore Ernie
Published: July 2002

We consider Pustejovsky's account of the semantic lexicon. We discuss and reject his argument that the complexity of lexical entries is required to account for lexical generativity. Finally, we defend a sort of lexical atomism: though, strictly speaking, we concede that lexical entries are typically complex, still we claim that their complexity does not jeopardize either the thesis that lexical meaning is atomistic or the identification of lexical meaning with denotation.
Incremental Construction of Minimal Acyclic Finite-State Automata
Authors: Daciuk Jan , Mihov Stoyan , Watson Bruce W. , Watson Richard E.
Published: July 2002

In this paper, we describe a new method for constructing minimal, deterministic, acyclic finite-state automata from a set of strings. Traditional methods consist of two phases: the first to construct a trie, the second one to minimize it. Our approach is to construct a minimal automaton in a single phase by adding new strings one by one and minimizing the resulting automaton on-the-fly. We present a general algorithm as well as a specialization that relies upon the lexicographical ordering of the input strings. Our method is fast and significantly lowers memory requirements in comparison to other methods.
True But Not False Memories Produce a Sensory Signature in Human Lateralized Brain Potentials
Authors: Fabiani Monica , Stadler Michael A. , Wessels Peter M.
Published: July 2002

False memories (e.g., recognition of events that did not occur) are considered behaviorally and subjectively indistinguishable from true memories. We report that brain activity differs when true and false memories are retrieved. Strongly associated lists of words were presented to one or the other cerebral hemisphere at study. This led to lateralized brain activity for these words during a centrally presented recognition test, reflecting their lateralized encoding. This activity was absent for nonstudied but strongly associated words falsely recognized as studied items. These results indicate that studied words leave sensory signatures of study experiences that are absent for false memories. In addition, hemifield effects emerged, including a slower reaction time (RT) for false recognition of nonstudied words whose associated lists were presented to the left hemifield (i.e., right hemisphere). These false recognition responses were accompanied by frontal slow wave activity, which may reflect a differential ability of the two hemispheres with respect to semantic processing.
fMRI Studies of Stroop Tasks Reveal Unique Roles of Anterior and Posterior Brain Systems in Attentional Selection
Authors: Banich Marie T. , Milham Michael P. , Atchley Ruthann , Cohen Neal J. , Webb Andrew , Wszalek Tracey , Kramer Arthur F. , Liang Zhei-Pei , Wright Alexander , Shenker Joel , Magin Richard
Published: July 2002

The brain's attentional system identifies and selects information that is task-relevant while ignoring information that is task-irrelevant. In two experiments using functional magnetic resonance imaging, we examined the effects of varying task-relevant information compared to task-irrelevant information. In the first experiment, we compared patterns of activation as attentional demands were increased for two Stroop tasks that differed in the task-relevant information, but not the task-irrelevant information: a color-word task and a spatial-word task. Distinct subdivisions of dorsolateral prefrontal cortex and the precuneus became activated for each task, indicating differential sensitivity of these regions to task-relevant information (e.g., spatial information vs. color). In the second experiment, we compared patterns of activation with increased attentional demands for two Stroop tasks that differed in task-irrelevant information, but not task-relevant information: a color-word task and color-object task. Little differentiation in activation for dorsolateral prefrontal and precuneus regions was observed, indicating a relative insensitivity of these regions to task-irrelevant information. However, we observed a differentiation in the pattern of activity for posterior regions. There were unique areas of activation in parietal regions for the color-word task and in occipito-temporal regions for the color-object task. No increase in activation was observed in regions responsible for processing the perceptual attribute of color. The results of this second experiment indicate that attentional selection in tasks such as the Stroop task, which contain multiple potential sources of relevant information (e.g., the word vs. its ink color), acts more by modulating the processing of task-irrelevant information than by modulating processing of task-relevant information.
The Influence of Memory Load Upon Delay-Interval Activity in a Working-Memory Task: An Event-Related Functional MRI Study
Authors: Jha Amishi P. , McCarthy Gregory
Published: July 2002

We conducted two fMRI studies to investigate the sensitivity of delay-period activity to changes in memory load during a delayed-recognition task for faces. In Experiment 1, each trial began with the presentation of a memory array consisting of one, two, or three faces that lasted for 3 sec. A 15-sec delay period followed during which no stimuli were present. The delay interval concluded with a one-face probe to which subjects made a button press response indicating whether this face was part of the memory array. Experiment 2 was similar in design except that the delay period was lengthened to 24 sec, and the memory array consisted of only one or three faces. We hypothesized that memory maintenance processes that spanned the delay interval would be revealed by their sensitivity to memory load. Long delay intervals were employed to temporally dissociate phasic activity engendered by the memory array from sustained activity reflecting maintenance. Regions of interest (ROIs) were defined anatomically for the superior frontal gyri (SFG), middle frontal gyri (MFG), and inferior frontal gyri (IFG), intraparietal sulci (IPS), and fusiform gyri (FFG) on a subject-by-subject basis. The mean time course of activity was determined for all voxels within these regions and for that subset of voxels within each ROI that correlated significantly with an empirically determined reference waveform. In both experiments, memory load significantly influenced activation 6-9 sec following the onset of the memory array with larger amplitude responses for higher load levels. Responses were greatest within MFG, IPS, and FFG. In both experiments, however, these load-sensitive differences declined over successive time intervals and were no longer significant at the end of the delay interval. Although insensitive to our load manipulation, sustained activation was present at the conclusion of the delay interval within MFG and other prefrontal regions. IPS delay activity returned to prestimulus baseline levels prior to the end of the delay period in Experiment 2, but not in Experiment 1. Within FFG, delay activity returned to prestimulus baseline levels prior to the conclusion of the delay interval in both experiments. Thus, while phasic processes engendered by the memory array were strongly affected by memory load, no evidence for load-sensitive delay-spanning maintenance processes was obtained.
Episodic Action Memory for Real Objects: An ERP Investigation With Perform, Watch, and Imagine Action Encoding Tasks Versus a Non-Action Encoding Task
Authors: Senkfor Ava J. , Petten Cyma Van , Kutas Marta
Published: July 2002

Cognitive research shows that people typically remember actions they perform better than those that they only watch or imagine doing, but also at times misremember doing actions they merely imagined or planned to do (source memory errors). Neural research suggests some overlap between brain regions engaged during action production, motor imagery, and action observation. The present study evaluates the similar-ities/differences in brain activity during the retrieval of various types of action and nonaction memories. Participants study real objects in one of four encoding conditions: performing an action, watching the experimenter perform an action, or imagining an action with an object, or a nonmotoric task of estimating an object's cost. At test, participants view color photos of the objects, and make source memory judgments about the initial encoding episodes. Event-related potentials (ERPs) during test reveal (1) content-specific brain activity depending on the nature of the encoding task, and (2) a hand tag, i.e., sensitivity to the hand with which an object had been manipulated at study. At fronto-central sites, ERPs are similar for the three action-retrieval conditions, which are distinct from those to the cost-encoded objects. At occipital sites ERPs distinguished objects from encoding conditions with visual motion (Perform and Watch) from those without visual motion (Imagine and Cost). Results thus suggest some degree of recapitulation of encoding brain activity during retrieval of memories with qualitatively distinct attributes.
Navigation and Acquisition of Spatial Knowledge in a Virtual Maze
Authors: Gillner Sabine , Mallot Hanspeter A.
Published: July 2002

Spatial behavior in humans and animals includes a wide variety of behavioral competences and makes use of a large number of sensory cues. Here we studied the ability of human subjects to search locations, to find shortcuts and novel paths, to estimate distances between remembered places, and to draw sketch maps of the explored environment; these competences are related to goal-independent memory of space, or cognitive maps. Information on spatial relations was restricted to two types: a visual motion sequence generated by simulated movements in a virtual maze and the subject's own movement decisions defining the path through the maze. Visual information was local (i.e., no global landmarks or compass information was provided). Other position and movement information (vestibular or proprioceptive) was excluded. The amount of visual information provided was varied over four experimental conditions. The results indicate that human subjects are able to learn a virtual maze from sequences of local views and movements. The information acquired is local, consisting of recognized positions and movement decisions associated to them. Although simple associations of this type can be shown to be present in some subjects, more complete configurational knowledge is acquired as well. The results are discussed in a view-based framework of navigation and the representation of spatial knowledge by means of a view graph.
Neuropsychological Evidence of an Integrated Visuotactile Representation of Peripersonal Space in Humans
Authors: Làdavas Elisabetta , Pellegrino Giuseppe di , Farnè Alessandro , Zeloni Gabriele
Published: July 2002

Current interpretations of extinction suggest that the disorder is due to an unbalanced competition between ipsilesional and contralesional representations of space.

The question addressed in this study is whether the competition between left and right representations of space in one sensory modality (i.e., touch) can be reduced or exacerbated by the activation of an intact spatial representation in a different modality that is functionally linked to the damaged representation (i.e., vision). This hypothesis was tested in 10 right-hemisphere lesioned patients who suffered from reliable tactile extinction. We found that a visual stimulus presented near the patient's ipsilesional hand (i.e., visual peripersonal space) inhibited the processing of a tactile stimulus delivered on the contralesional hand (cross-modal visuotactile extinction) to the same extent as did an ipsilesional tactile stimulation (unimodal tactile extinction). It was also found that a visual stimulus presented near the contralesional hand improved the detection of a tactile stimulus applied to the same hand. In striking contrast, less modulatory effects of vision on touch perception were observed when a visual stimulus was presented far from the space immediately around the patient's hand (i.e., extrapersonal space).

This study clearly demonstrates the existence of a visual peripersonal space centered on the hand in humans and its modulatory effects on tactile perception. These findings are explained by referring to the activity of bimodal neurons in premotor and parietal cortex of macaque, which have tactile receptive fields on the hand and corresponding visual receptive fields in the space immediately adjacent to the tactile fields.
Preferences for Visual Stimuli Following Amygdala Damage
Authors: Adolphs Ralph , Tranel Daniel
Published: July 2002

Bilateral damage to the human amygdala impairs retrieval of emotional and social information from faces. An important unanswered question concerns the specificity of the impairment for faces. To address this question, we examined preferences for a broad class of visual stimuli in two subjects with complete bilateral amygdala damage, both of whom were impaired in judgments of faces. Relative to controls, the subjects showed a positive bias for simple nonsense figures, color patterns, three-dimensional-looking objects and landscapes. The impairment was most pronounced in regard to those stimuli that are normally liked the least. The human amygdala thus appears to play a general role in guiding preferences for visual stimuli that are normally judged to be aversive.
Retrieval Properties of a Hopfield Model with Random Asymmetric Interactions
Authors: Chengxiang Zhang , Dasgupta Chandan , Singh Manoranjan P.
Published: July 2002

The process of pattern retrieval in a Hopfield model in which a random antisymmetric component is added to the otherwise symmetric synaptic matrix is studied by computer simulations. The introduction of the antisymmetric component is found to increase the fraction of random inputs that converge to the memory states. However, the size of the basin of attraction of a memory state does not show any significant change when asymmetry is introduced in the synaptic matrix. We show that this is due to the fact that the spurious fixed points, which are destabilized by the introduction of asymmetry, have very small basins of attraction. The convergence time to spurious fixed-point attractors increases faster than that for the memory states as the asymmetry parameter is increased. The possibility of convergence to spurious fixed points is greatly reduced if a suitable upper limit is set for the convergence time. This prescription works better if the synaptic matrix has an antisymmetric component.
Minimal Feedforward Parity Networks Using Threshold Gates
Authors: Fung Hon-Kwok , Li Leong Kwan
Published: July 2002

This article presents preliminary research on the general problem of reducing the number of neurons needed in a neural network so that the network can perform a specific recognition task. We consider a single-hidden-layer feedforward network in which only McCulloch-Pitts units are employed in the hidden layer. We show that if only interconnections between adjacent layers are allowed, the minimum size of the hidden layer required to solve the n-bit parity problem is n when n ≤ 4.
Gaussian Process Approach to Spiking Neurons for Inhomogeneous Poisson Inputs
Authors: Amemori Ken-ichi , Ishii Shin
Published: July 2002

This article presents a new theoretical framework to consider the dynamics of a stochastic spiking neuron model with general membrane response to input spike. We assume that the input spikes obey an inhomogeneous Poisson process. The stochastic process of the membrane potential then becomes a gaussian process. When a general type of the membrane response is assumed, the stochastic process becomes a Markov-gaussian process. We present a calculation method for the membrane potential density and the firing probability density. Our new formulation is the extension of the existing formulation based on diffusion approximation. Although the single Markov assumption of the diffusion approximation simplifies the stochastic process analysis, the calculation is inaccurate when the stochastic process involves a multiple Markov property. We find that the variation of the shape of the membrane response, which has often been ignored in existing stochastic process studies, significantly affects the firing probability. Our approach can consider the reset effect, which has been difficult to deal with by analysis based on the first passage time density.
The Whitney Reduction Network: A Method for Computing Autoassociative Graphs
Authors: Broomhead D. S. , Kirby M. J.
Published: July 2002

This article introduces a new architecture and associated algorithms ideal for implementing the dimensionality reduction of an m-dimensionalmanifold initially residing in an n-dimensional Euclidean space where n m. Motivated by Whitney's embedding theorem, the network is capable of training the identity mapping employing the idea of the graph of a function. In theory, a reduction to a dimension d that retains the differential structure of the original data may be achieved for some d ≤ 2m + 1. To implement this network, we propose the idea of a good-projection, which enhances the generalization capabilities of the network, and an adaptive secant basis algorithm to achieve it. The effect of noise on this procedure is also considered. The approach is illustrated with several examples.
Computational Studies of Lateralization of Phoneme Sequence Generation
Authors: Reggia James A. , Goodall Sharon , Shkuro Yuri
Published: July 2002

The mechanisms underlying cerebral lateralization of language are poorly understood. Asymmetries in the size of hemispheric regions and other factors have been suggested as possible underlying causal factors, and the corpus callosum (interhemispheric connections) has also been postulated to play a role. To examine these issues, we created a neural model consisting of paired cerebral hemispheric regions interacting via the corpus callosum. The model was trained to generate the correct sequence of phonemes for 50 monosyllabic words (simulated reading aloud) under a variety of assumptions about hemispheric asymmetries and callosal effects. After training, the ability of the full model and each hemisphere acting alone to perform this task was measured. Lateralization occurred readily toward the side having larger size, higher excitability, or higher learning-rate parameter. Lateralization appeared most readily and intensely with strongly inhibitory callosal connections, supporting past arguments that the effective functionality of the corpus callosum is inhibitory. Many of the results are interpretable as the outcome of a “race to learn” between the model's two hemispheric regions, leading to the concept that asymmetric hemispheric plasticity is a critical common causative factor in lateralization. To our knowledge, this is the first computational model to demonstrate spontaneous lateralization of function, and it suggests that such models can be useful for understanding the mechanisms of cerebral lateralization.
Fixed-Point Attractor Analysis for a Class of Neurodynamics
Authors: Feng Jianfeng , Brown David
Published: July 2002

Nearly all models in neural networks start from the assumption that the input-output characteristic is a sigmoidal function. On parameter space, we present a systematic and feasible method for analyzing the whole spectrum of attractors—all-saturated, all-but-one-saturated, all-but-twosaturated, and so on—of a neurodynamical system with a saturated sigmoidal function as its input-output characteristic. We present an argument that claims, under a mild condition, that only all-saturated or all but-one-saturated attractors are observable for the neurodynamics. For any given all-saturated configuration [Formula: see text] (all-but-one-saturated configuration [Formula: see text]) the article shows how to construct an exact parameter region R([Formula: see text])([Formula: see text]([Formula: see text])) such that if and only if the parameters fall within R([Formula: see text])([Formula: see text]([Formula: see text])), then [Formula: see text]([Formula: see text]) is an attractor (a fixed point) of the dynamics. The parameter region for an all-saturated fixed-point attractor is independent of the specific choice of a saturated sigmoidal function, whereas for an all-but-one-saturated fixed point, it is sensitive to the input-output characteristic.

Based on a similar idea, the role of weight normalization realized by a saturated sigmoidal function in competitive learning is discussed. A necessary and sufficient condition is provided to distinguish two kinds of competitive learning: stable competitive learning with the weight vectors representing extremes of input space and being fixed-point attractors, and unstable competitive learning.

We apply our results to Linsker's model and (using extreme value theory in statistics) the Hopfield model and obtain some novel results on these two models.
Symphony Orchestras and Artist-Prophets: Cultural Isomorphism and the Allocation of Power in Music
Authors: Osborne William
Published: July 2002

The Vienna Philharmonic is the paradigm of the symphony orchestra. No other orchestra in the world has been so intimately involved with the composers and cultural developments that have defined the genre. Despite recent protests against the orchestra, it still excludes women and visible members of racial minorities based on its belief that gender and ethnic uniformity give it aesthetic superiority. The Vienna Philharmonic thus provides an interesting case study for the allocation of power in Western art music. In this article, the author documents the orchestra's ideologies and relates them to a general theory that the allocation of power in artistic expression is often culturally isomorphic with the larger values of the society in which that expression occurs. He then discusses how cultural isomorphism affects concepts of power allocation in the modernist and postmodernist mind-sets.
Images of Armageddon: Japan's 1980s Theatre Culture
Authors: Tadashi Uchino
Published: July 2002

After the collapse of the “bubble economy” in the early 1990s and the 1995 Aum Shinri-kyō's terrorist gas attack, the Japanese wrestled once more with the question of their national identity. What links connect today's Japan with the pre-WWII empire, Hiroshima and Nagasaki, and the early postwar years? How is theatre implicated in the national project of memory and forgetting?
Presence in Shared Virtual Environments and Virtual Togetherness
Authors: Durlach Nat , Slater Mel
Published: July 2002

This Forum article discusses the relationships among people, their avatars, and their virtual environment workstations in a shared virtual environment. It introduces the notion of togetherness, the sense of people being together in a shared space, which is the counterpart for shared VEs to the presence of an individual in a VE. The role of tactual communication is emphasized as being fundamental to togetherness.
Effects of Stereoscopic Presentation, Image Motion, and Screen Size on Subjective and Objective Corroborative Measures of Presence
Authors: IJsselsteijn Wijnand , Ridder Huib de , Freeman Jonathan , Avons S. E. , Bouwhuis Don
Published: July 2002

Recently, we reported that group subjective measures of presence as well as observers' postural responses are sensitive to increasing the realism of a display with motion content, by the addition of stereoscopic information, using a 20-inch stereoscopic screen with an effective horizontal field of view of 28 deg. (Freeman, Avons, Meddis, Pearson, & IJsselsteijn, 2000). The experiment presented here employed a large projection display with a 50 deg. horizontal field of view showing a rally car traversing a curved track at speed. The independent variables included image motion and stereoscopic presentation as within-subjects factors and screen size as a between-subjects factor. Dependent variables included subjective measures of presence, vection, involvement, and sickness, as well as observers' lateral postural responses, which served as a candidate objective corroborative measure of presence. Results demonstrated a noisy yet positive effect of stereoscopic presentation on the lateral postural responses. Post-test subjective ratings revealed a significant effect of stereoscopic presentation on the subjective judgments of presence, but not on those of vection, involvement, or sickness. Image motion had a large and significant effect on the subjective judgments of presence, vection, and involvement. The effect of image motion was considerably larger than that of stereoscopic viewing. By comparing results between experiments, a large effect of screen size on subjective presence ratings could be demonstrated, but only for the video stimulus that contained motion. The postural response measure did not differentiate between screen sizes, thus limiting its utility as an objective corroborative measure of presence, although further research is required to be able to be more firm in our conclusion regarding this issue.
Components for Distributed Virtual Environments
Authors: Oliveira Manuel , Crowcroft Jon , Slater Mel
Published: July 2002

A virtual environment (VE) presents a complex problem with interesting nontrivial challenges for software development. The problems increase when considering VEs that are both distributed and shared among multiple participants. The majority of existing systems supporting large-scale VEs (LSVEs) are based on monolithic architectures, making maintenance and software reuse difficult at best. These problems have begun to be addressed by recent VE systems that employ software engineering principles in their design. Although modularity is addressed, many other issues remain unsolved, such as interoperability between different systems.

The Java Adaptive Dynamic Environment (JADE) is presented as an alternative to the traditional approach for developing a core infrastructure for VE systems. JADE consists of a component framework along with a lightweight cross-platform kernel that permits system evolution at runtime and enables cross-system integration.
Multioperator Teleoperation of Multirobot Systems with Time Delay: Part I—Aids for Collision-Free Control
Authors: Chong Nak Young , Kawabata Shun'ichi , Ohba Kohtaro , Kotoku Tetsuo , Komoriya Kiyoshi , Takase Kunikatsu , Tanie Kazuo
Published: July 2002

In this paper, various coordinated control schemes are explored in Multioperatormultirobot (MOMR) teleoperation through a communication network with time delay. Over the past decades, problems and several notable results have been reported mainly in the Single-Operator–Single-Robot (SOSR) teleoperation system. Recently, the need for cooperation has rapidly emerged in many possible applications such as plant maintenance, construction, and surgery, because multirobot cooperation would have a significant advantage over a single robot in such cases. Thus, there is a growing interest in the control of multirobot systems in remote teleoperation, too. However, the time delay over the network would pose a more difficult problem to MOMR teleoperation systems and seriously affect their performance. In this work, our recent efforts devoted to the coordinated control of the MOMR teleoperation is described. First, we build a virtual experimental test bed to investigate the cooperation between two telerobots in remote environments. Then, different coordinated control aids are proposed to cope with collisions arising from delayed visual feedback from the remote location. To verify the validity of the proposed schemes, we perform extensive simulations of various planar rearrangement tasks employing local and remote graphics simulators over an ethernet LAN subject to a simulated communication delay.
Use of Virtual Environments for Acquiring Configurational Knowledge about Specific Real-World Spaces: I. Preliminary Experiment
Authors: Koh Glenn , Wiegand Thomas E. von , Garnett Rebecca Lee , Durlach Nathaniel I. , Shinn-Cunningham Barbara
Published: July 2002

A relatively simple architectural space was modeled and used to compare the effects of spatial training in simulations versus training in the real world. Thirty-five subjects were trained in one of the following conditions: real world (RW), virtual environment (VE), nonimmersive virtual environment (NVE), and model (Mod). The VE condition made use of a head-mounted display to view the simulated environment, while the NVE condition used a desktop monitor. In the Mod condition, the subject viewed and could manipulate a 3-D model of the space, viewed from a desktop display. The training-transfer tasks, performed after brief unstructured exposure to the actual space or to one of the simulations, consisted of estimating the bearing and range to various targets in the real space from various spatially distributed stations, each such pair of estimates constituting a subtask of the overall transfer task. Results obtained from each of the four training conditions proved to be roughly the same. Training in any one of the simulations was comparable to training in the real world. Independent of training condition, there was a strong tendency among subjects to underestimate range. Variability in range errors was dominated by differences among subjects, whereas variability in bearing errors was dominated by differences among subtasks. These results are discussed in the context of plans for future work.
The Emerging Debate on the Need for a World Environment Organization: A Commentary
Authors: Biermann Frank
Published: July 2002

The debate on institutional reform of international environmental policy-making has gained momentum. This article discusses whether the United Nations Environment Programme (UNEP) should be replaced with a stronger world environment organization. First, it outlines different models of a world environment organization. It argues that the best option for the next decade would be to upgrade UNEP to a full-fledged international organization while maintaining the current system of decentralized, issue-specific international environmental regimes. In the long run, however, a world environment organization should lead to a closer integration and coordination of the myriad environmental treaties in the same manner in which the World Trade Organization has integrated the major trade agreements. Second, the article comments on the writings of both advocates and opponents of a world environment organization, with a focus on the contributions to this inaugural issue of Global Environmental Politics.
'ISRAEL IS LAID WASTE; HIS SEED IS NO MORE': WHAT IF MERNEPTAH'S SCRIBES WERE TELLING THE TRUTH?
Authors: Whitelam Keith
Published: July 2002

The reference to Israel in the Merneptah stele plays a pivotal role in the debate on Israel's emergence in Late Bronze-Iron Age Palestine. Most scholars ignore 'the plain sense of the text' which suggests that Israel has been wiped out. Recent research on ethnicity undermines the essentialist notion that there is a direct connection between Merneptah's 'Israel' and later entities of the same name. The article explores the implications of accepting the claim of Merneptah's scribes that 'Israel' had been destroyed
MULĀZAMA OR HARASSMENT OF RECALCITRANT DEBTORS IN ISLAMIC LAW
Authors: Ziadeh Farhat
Published: July 2002

The institution of mulāzama, or the harassment of the debtor through the constant pursuit of him, could obtain in three situations: (a) the pursuit of a penniless debtor who has been released from prison and declared bankrupt by a judge, (b) the pursuit of a debtor capable of paying his debt, and (c) the pursuit of a debtor before trial, lest he flee, pending the production of witnesses. Only Abū Hanīfa, and, following him, the dominant opinion of his school, supported the first. Some later Hanafīs as well as jurists of other schools supported the other two in varying degrees, until relatively modern times when the institution was declared inoperative or has been completely ignored. The harshness of the early Hanafī position suggests an origin in a preceding civilization: possibly the Roman, because of similarities in terminology; possibly the Indo-Iranian, because of the provenance of early Hanafīs in territories influenced by that civilization; or both.