bluuebunny/crossref_metadata_2025 huggingface dataset:
The Guanylyl Cyclase Family at Y2K
Authors: Wedel BJ , Garbers DL
Published: July 2002

▪ Abstract  During the 1980s the purification, cloning, and expression of various forms of guanylyl cyclase (GC) revealed that they served as receptors for extracellular signals. Seven membrane forms, which presumably exist as homodimers, and four subunits of apparent heterodimers (commonly referred to as the soluble forms) are known, but in animals such as nematodes, much larger numbers of GCs are expressed. The number of transmembrane segments (none, one, or multiple) divide the GC family into three groups. Those with no or one transmembrane segment bind nitric oxide/carbon monoxide (NO/CO) or peptides. There are no known ligands for the multiple transmembrane segment class of GCs. Mutational and structural analyses support a model where catalysis requires a shared substrate binding site between the subunits, whether homomeric or heteromeric in nature. Because some cyclases or cyclase ligand genes lack specific GC inhibitors, disruption of either has been used to define the functions of individual cyclases, as well as to define human genetic disease counterparts.
On The Cellular and Network Bases of Epileptic Seizures
Authors: McCormick David A , Contreras Diego
Published: July 2002

▪ Abstract  The highly interconnected networks of the mammalian forebrain can generate a wide variety of synchronized activities, including those underlying epileptic seizures, which often appear as a transformation of otherwise normal brain rhythms. The cerebral cortex and hippocampus are particularly prone to the generation of the large, synchronized bursts of activity underlying many forms of seizures owing to strong recurrent excitatory connections, the presence of intrinsically burst-generating neurons, ephaptic interactions among closely spaced neurons, and synaptic plasticity. The simplest form of epileptiform activity in these structures is the interictal spike, a synchronized burst of action potentials generated by recurrent excitation, followed by a period of hyperpolarization, in a localized pool of pyramidal neurons. Seizures can also be generated in response to a loss of balance between excitatory and inhibitory influences and can take the form of either tonic depolarizations or repetitive, rhythmic burst discharges, either as clonic or spike-wave activity, again mediated both by intrinsic membrane properties and synaptic interactions. The interaction of the cerebral cortex and the thalamus, in conjunction with intrathalamic communication, can also generate spike waves similar to those occurring during human absence seizure discharges. Although epileptic syndromes and their causes are diverse, the cellular mechanisms of seizure generation appear to fall into only two categories: rhythmic or tonic “runaway” excitation or the synchronized and rhythmic interplay between excitatory and inhibitory neurons and membrane conductances.
THE DESIGN AND ANALYSIS OF SOCIAL-INTERACTION RESEARCH
Authors: Kenny David A.
Published: July 2002

▪ Abstract  Static models of interacting persons measured at the interval level are reviewed. A discussion of the fundamental sources of variance and key design decisions in social-interaction research is presented. Outlined are the basic designs for social-interaction research and their proper analysis. Multilevel modeling is likely to become the most common data analysis method. Critical issues unique to social-interaction research are examined, particularly the effect of the partner on the interaction actor. Finally, illustrations of analyses from four extended examples are presented.
EVALUATING THE COST-EFFECTIVENESS OF CLINICAL AND PUBLIC HEALTH MEASURES
Authors: Graham John D. , Corso Phaedra S. , Morris Jill M. , Segui-Gomez Maria , Weinstein Milton C.
Published: July 2002

▪ Abstract  Cost-effectiveness analysis, an analytic tool that expresses as a ratio the cost of obtaining an additional unit of health outcome, can help decision makers achieve more health protection for the same or less cost. We characterize the state of the cost-effectiveness analysis literature by reviewing how this technique is applied to various clinical and public health interventions. We describe the results of cost-effectiveness analyses for over 40 interventions to reduce cancer, heart disease, trauma, and infectious disease. The cost-effectiveness ratios for these interventions vary enormously, from interventions that save money to those that cost more than $1 million per year of life gained. The methods used to derive the cost-effectiveness ratios also vary considerably, and we summarize this variation within each health area. Greater uniformity of analytical practice will be necessary if cost-effectiveness analysis is to become a more influential tool in debates about resource allocation.
Direct Costs of Modern Treatment of Aneurysmal Subarachnoid Hemorrhage in the First Year After Diagnosis
Authors: Roos Y.B.W.E.M. , Dijkgraaf M.G.W. , Albrecht K.W. , Beenen L.F.M. , Groen R.J.M. , de Haan R.J. , Vermeulen M.
Published: July 2002

Background and Purpose

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The purpose of this study was to investigate the current direct costs of modern management of patients with aneurysmal subarachnoid hemorrhage in the first year after diagnosis.

Methods

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During a 1-year period, we studied all admitted patients with subarachnoid hemorrhage from a population of 2 million people. We calculated the direct costs of treatment, which included the costs of medical and nursing care and the related travel expenses of patients. We calculated true costs for all major healthcare resources. National census data, if available, and standard charges were used to determine healthcare resource expenses.

Results

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Hospital admissions and diagnostic and therapeutic interventions in 110 patients accounted for 85% of all costs; 64% of the total direct medical costs during admission were the medical, nursing, and overhead costs alone. Patients discharged directly to home generated 4% of the total budget, whereas admission to a nursing home accounted for the remaining 11% of the total costs. Of the diagnostic and therapeutic costs, 45% was caused by imaging and 42% by surgery or coiling. Angiography alone accounted for 52% of the total imaging costs and 24% of the total diagnostic and therapeutic costs. Prescribed medication accounted for only 3% of the total budget of diagnostic and therapeutic costs.

Conclusions

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Most direct costs during the first year after aneurysmal subarachnoid hemorrhage are caused by the hospital inpatient days, accounting for two thirds of the total costs generated during the first year after the initial bleeding. If new costly treatments succeed in reducing the average length of inpatient hospital stays, then progress in therapy may prove cost effective and might even be cost saving.
Capital Mobility and the Origins of Stock Markets
Authors: Verdier Daniel
Published: July 2002

I illustrate the accepted, though hardly researched, idea that political institutions play a role in locking in factor specificity across sectors, space, and borders. I use the emergence of modern capital markets in the nineteenth century, a process that threatened to redeploy financial resources away from land and traditional sectors to heavy industry, as a test case to ascertain the degree of domestic financial capital mobility in nine advanced industrialized countries. The main finding is that cross-national variations in financial capital mobility, holding constant the level of economic development, reflect the degree of state centralization.
Response to Finnemore and Toope
Authors: Goldstein Judith , Kahler Miles , Keohane Robert O. , Slaughter Anne-Marie
Published: July 2002

Mark Twain has been quoted as saying, “It is admirable to do good. It is also admirable to tell others to do good—and a lot less trouble.” Twain's perhaps apocryphal aphorism could be adapted to contemporary social science scholarship: It is admirable to articulate and seek to apply new concepts. It is also admirable to tell others what is wrong with their concepts—and a lot less trouble.

Martha Finnemore and Stephen Toope, in their comment on our summer 2000 special issue of IO, “Legalization and World Politics,” seem to be following this adaptation of Twain's advice. They think that our definition of legalization focuses too much on formalized constraints, that it does not relate closely to broader concepts of law, that we are too committed to a rational-strategic approach to politics, and that we do not have a theory of what generates obligation. They do not attempt, in their critique, to produce an alternative conceptualization that attains the breadth they seek without sacrificing conceptual and theoretical coherence. We thought that our own argument was both “dynamic” and “process-oriented,” so we look forward with interest to their attempt to improve on our work. We particularly look forward to a carefully designed research program that will evaluate fairly the many empirical claims that they advance.
Slave Naming Patterns: Onomastics and the Taxonomy of Race in Eighteenth-Century Jamaica
Authors: Burnard Trevor
Published: July 2002

An analysis ofthe naming patterns of Jamaican slaves in the mid-eighteenth century shows that whites considered blacks to be entirely different from themselves. The taxonomic differences between European naming practices and slave naming practices were both considerable and onomastically significant. Slaves could be recognized by their names as much as by their color. Slaves reacted to such naming practices by rejecting their slave names upon gaining their freedom, though they adopted methods of bricolage common to other aspects of Afro-Caribbean expressive culture.
New Media as Resistance: Colombia
Authors: Duque Alejandro
Published: July 2002

The author proposes possible ways for artists and cultural activists to use the Internet and other new media to help counter the currently devastating situation in Colombia.
Analytical Photography: Portraiture, from the Index to the Epidermis
Authors: Gonzales-Day Ken
Published: July 2002

The current abundance of scholarship concerning the technological development of photography has coexisted with a proportionate absence of recent critical analysis of photographic images. Given photography's long-standing embrace of technological advances, even predating the portable camera or roll film, this article revisits some early uses of scientific photography in order to clarify the impact of digital technology on contempo-rary photographic practice. The author uses scientific photogra-phy and photographic archives as the groundwork for photo-graphic experiments into what might be called analytical photography. The essay con-cludes with a reconsideration of the photographic portrait.
Phytochromography— Screen Printing with Plants: Research into Alternative Ink Technology
Authors: Shaw Phil
Published: July 2002

Doubts about the true nature of recently introduced “water-based” screen-printing inks prompted research into the possibility of producing genuinely water-based inks in which both pigment and thickener are derived from vegetable sources. Literature suggests that not only is this possible but it might even be viable as an industrial process. The author's research concentrates primarily on the development of a range of “process,” or “trichromatic,” screen-printing colors from plants, for which the author has coined the term, “Phytochromography.” To complement this work, the author describes the establishment of an “ink garden” capable of supplying quantities of plant material for further research. Issues relating to the environment, occupational health and sustainability are also touched upon. Initial results of this research show considerable cause for optimism, although some problems remain.
On the Need for Visual Formalisms in Music Processing
Authors: Balaban Mira , Elhadad Michael
Published: July 2002

Computer music environments (CMEs) are notoriously difficult to design and implement. As computer programs, they reflect the complex nature of music ontology and must support real-time manipulation of multimedia data. In addition, these programs must be usable by native users, supporting their creative process without obstructing it through technical difficulties. To achieve these goals, the authors argue, CMEs must be provided with a well-defined methodology relying on techniques from the fields of software engineering, artificial intelligence, and knowledge representation. This paper contributes an aspect of this methodology, concentrating on the role of visualizations in CMEs. The authors state that visualization deserves a specialized theory that is based on music ontology and that is independent of the concrete, implemented graphical interface.
Synesthetic Art— An Imaginary Number?
Authors: Hertz Paul
Published: July 2002

Works that fuse the senses are often referred to as “synesthetic art.” Computers, which offer the possibility of controlling and synchronizing different media and implementing highly abstract compositional structures across media, seem an ideal tool for synesthetic art. This essay argues that a structural approach to such an art form is inadequate, and that it must be grounded in its potential symbolic functions. Starting from a brief examination of synesthesia as a neurological phenomenon and a sketch of the origins and influence of Baudelaire's poetics of synesthesia, this essay suggests points of departure for a poetics of multisensory composition.
Modulation of Spatial Orientation Processing by Mental Imagery Instructions: A MEG Study of Representational Momentum
Authors: Amorim Michel-Ange , Lang Wilfried , Lindinger Gerald , Mayer Dagmar , Deecke Lüder , Berthoz Alain
Published: July 2002

Under appropriate conditions, an observer's memory for the final position of an abruptly halted moving object is distorted in the direction of the represented motion. This phenomenon is called “representational momentum” (RM). We examined the effect of mental imagery instructions on the modulation of spatial orientation processing by testing for RM under conditions of picture versus body rotation perception and imagination. Behavioral data were gathered via classical reaction time and error measurements, whereas brain activity was recorded with the help of magnetoence-phalography (MEG). Due to the so-called inverse problem and to signal complexity, results were described at the signal level rather than with the source location modeling. Brain magnetic field strength and spatial distribution, as well as latency of P200m evoked fields were used as neurocognitive markers. A task was devised where a subject examined a rotating sea horizon as seen from a virtual boat in order to extrapolate either the picture motion or the body motion relative to the picture while the latter disappeared temporarily until a test-view was displayed as a final orientation candidate. Results suggest that perceptual interpretation and extrapolation of visual motion in the roll plane capitalize on the fronto-parietal cortical networks involving working memory processes. Extrapolation of the rotational dynamics of sea horizon revealed a RM effect simulating the role of gravity in rotational equilibrium. Modulation of the P200m component reflected spatial orientation processing and a non-voluntary detection of an incongruity between displayed and expected final orientations given the implied motion. Neuromagnetic properties of anticipatory (Contingent Magnetic Variation) and evoked (P200m) brain magnetic fields suggest, respectively, differential allocation of attentional resources by mental imagery instructions (picture vs. body tilt), and a communality of neural structures (in the right centro-parietal region) for the control of both RM and mental rotation processes. Finally, the RM of the body motion is less prone to forward shifts than that of picture motion evidencing an internalization of the implied mass of the virtual body of the observer.
The Emotional Modulation of Cognitive Processing: An fMRI Study
Authors: Simpson Joseph R. , Öngür Dost , Akbudak Erbil , Conturo Thomas E. , Ollinger John M. , Snyder Abraham Z. , Gusnard Debra A. , Raichle Marcus E.
Published: July 2002

The functional neuroanatomy of visual processing of surface features of emotionally valenced pictorial stimuli was examined in normal human subjects using functional magnetic resonance imaging (fMRI). Pictorial stimuli were of two types: emotionally negative and neutral pictures. Task performance was slower for the negatively valenced than for the neutral pictures. Significant blood oxygen level dependent (BOLD) increases occurred in the medial and dorsolateral prefrontal cortex, midbrain, substantia innominata, and/or amygdala, and in the posterior cortical visual areas for both stimulus types. Increases were greater for the negatively valenced stimuli. While there was a small but significant BOLD decrease in the subgenual prefrontal cortex, which was larger in response to the negatively valenced pictures, there was an almost complete absence of other decreases prominently seen during the performance of demanding cognitive tasks [Shulman, G. L., Fiez, J. A., Corbetta, M., Buckner, R. L., Miezin, F. M., Raichle, M. E., & Petersen, S. E. (1997). Common blood flow changes across visual tasks: II. Decreases in cerebral cortex. Journal of Cognitive Neuroscience, 9, 648-663]. These results provide evidence that the emotional valence and arousing nature of stimuli used during the performance of an attention-demanding cognitive task are reflected in discernable, quantitative changes in the functional anatomy associated with task performance.
The Effects of Case Mixing on Word Recognition: Evidence from a PET Study
Authors: Mayall Kate , Humphreys Glyn W. , Mechelli Andrea , Olson Andrew , Price Cathy J.
Published: July 2002

The early stages of visual word recognition were investigated by scanning participants using PET as they took part in implicit and explicit reading tasks with visually disrupted stimuli. CaSe MiXiNg has been shown in behavioral studies to increase reaction times (RTs) in naming and other word recognition tasks. In this study, we found that during both an implicit (feature detection) task and an explicit word-naming task, mixed-case words compared to same-case words produced increased activation in an area of the right parietal cortex previously associated with visual attention. No effect of case was found in this area for pseudowords or consonant strings. Further, lowering the contrast of the stimuli slowed RTs as much as case mixing, but did not lead to the same increase in right parietal activation. No significant effect of case mixing was observed in left-hemisphere language areas. The results suggest that reading mixed-case words requires increased attentional processing. However, later word recognition processes may be relatively unaffected by the disruption in presentation.
Similarity in Perception: A Window to Brain Organization
Authors: Solan Zach , Ruppin Eytan
Published: July 2002

This paper presents a neural model of similarity perception in identification tasks. It is based on self-organizing maps and population coding and is examined through five different identification experiments. Simulating an identification task, the neural model generates a confusion matrix that can be compared directly with that of human subjects. The model achieves a fairly accurate match with the pertaining experimental data both during training and thereafter. To achieve this fit, we find that the entire activity in the network should decline while learning the identification task, and that the population encoding of the specific stimuli should become sparse as the network organizes. Our results, thus, suggest that a self-organizing neural model employing population coding can account for identification processing while suggesting computational constraints on the underlying cortical networks.
Dissociable Processes for Learning the Surface Structure and Abstract Structure of Sensorimotor Sequences
Authors: Dominey Peter F. , Lelekov Taïssia , Ventre-Dominey Jocelyne , Jeannerod Marc
Published: July 2002

A sensorimotor sequence may contain information structure at several different levels. In this study, we investigated the hypothesis that two dissociable processes are required for the learning of surface structure and abstract structure, respectively, of sensorimotor sequences. Surface structure is the simple serial order of the sequence elements, whereas abstract structure is defined by relationships between repeating sequence elements. Thus, sequences ABCBAC and DEFEDF have different surface structures but share a common abstract structure, 123213, and are therefore isomorphic. Our simulations of sequence learning performance in serial reaction time (SRT) tasks demonstrated that (1) an existing model of the primate fronto-striatal system is capable of learning surface structure but fails to learn abstract structure, which requires an additional capability, (2) surface and abstract structure can be learned independently by these independent processes, and (3) only abstract structure transfers to isomorphic sequences.

We tested these predictions in human subjects. For a sequence with predictable surface and abstract structure, subjects in either explicit or implicit conditions learn the surface structure, but only explicit subjects learn and transfer the abstract structure. For sequences with only abstract structure, learning and transfer of this structure occurs only in the explicit group. These results are parallel to those from the simulations and support our dissociable process hypothesis. Based on the synthesis of the current simulation and empirical results with our previous neuropsychological findings, we propose a neuro-physiological basis for these dissociable processes: Surface structure can be learned by processes that operate under implicit conditions and rely on the fronto-striatal system, whereas learning abstract structure requires a more explicit activation of dissociable processes that rely on a distributed network that includes the left anterior cortex.
Second-Order Learning Algorithm with Squared Penalty Term
Authors: Saito Kazumi , Nakano Ryohei
Published: July 2002

This article compares three penalty terms with respect to the efficiency of supervised learning, by using first- and second-order off-line learning algorithms and a first-order on-line algorithm. Our experiments showed that for a reasonably adequate penalty factor, the combination of the squared penalty term and the second-order learning algorithm drastically improves the convergence performance in comparison to the other combinations, at the same time bringing about excellent generalization performance. Moreover, in order to understand how differently each penalty term works, a function surface evaluation is described. Finally, we show how cross validation can be applied to find an optimal penalty factor.
On Synchrony of Weakly Coupled Neurons at Low Firing Rate
Authors: Neltner L. , Hansel D.
Published: July 2002

The dynamics of a pair of weakly interacting conductance-based neurons, firing at low frequency, v, is investigated in the framework of the phase-reduction method. The stability of the antiphase and the in-phase locked state is studied. It is found that for a large class of conductance-based models, the antiphase state is stable (resp., unstable) for excitatory (resp., inhibitory) interactions if the synaptic time constant is above a critical value τcs, which scales as |logv| when v goes to zero.
The Influence of Limit Cycle Topology on the Phase Resetting Curve
Authors: Oprisan Sorinel A. , Canavier Carmen C.
Published: July 2002

Understanding the phenomenology of phase resetting is an essential step toward developing a formalism for the analysis of circuits composed of bursting neurons that receive multiple, and sometimes overlapping, inputs. If we are to use phase-resetting methods to analyze these circuits, we can either generate phase-resetting curves (PRCs) for all possible inputs and combinations of inputs, or we can develop an understanding of how to construct PRCs for arbitrary perturbations of a given neuron. The latter strategy is the goal of this study.

We present a geometrical derivation of phase resetting of neural limit cycle oscillators in response to short current pulses. A geometrical phase is defined as the distance traveled along the limit cycle in the appropriate phase space. The perturbations in current are treated as displacements in the direction corresponding to membrane voltage. We show that for type I oscillators, the direction of a perturbation in current is nearly tangent to the limit cycle; hence, the projection of the displacement in voltage onto the limit cycle is sufficient to give the geometrical phase resetting. In order to obtain the phase resetting in terms of elapsed time or temporal phase, a mapping between geometrical and temporal phase is obtained empirically and used to make the conversion. This mapping is shown to be an invariant of the dynamics. Perturbations in current applied to type II oscillators produce significant normal displacements from the limit cycle, so the difference in angular velocity at displaced points compared to the angular velocity on the limit cycle must be taken into account. Empirical attempts to correct for differences in angular velocity (amplitude versus phase effects in terms of a circular coordinate system) during relaxation back to the limit cycle achieved some success in the construction of phase-resetting curves for type II model oscillators. The ultimate goal of this work is the extension of these techniques to biological circuits comprising type II neural oscillators, which appear frequently in identified central pattern-generating circuits.
Competition for Neurotrophic Factors: Mathematical Analysis
Authors: Elliott T. , Shadbolt N. R.
Published: July 2002

Neurotrophic factors, particularly the neurotrophin gene family of neurotrophic factors, are implicated in activity-dependent anatomical plasticity in the visual cortex and at the neuromuscular junction. Accumulating evidence implicates neurotrophic factors as possible mediators of activity-dependent competition between afferents, leading to the segregation of afferents' arbors on the target space. We present a biologically plausible mathematical model of competition for neurotrophic factors. We show that the model leads to anatomical segregation, provided that the levels of neurotrophic factors released in an activity-independent manner, or the levels available by exogenous infusion, are below a critical value, which we derive. Above this critical value, afferent segregation breaks down. We also show that the model segregates afferents even in the presence of very highly correlated patterns of afferent activity. The model is therefore ideally suited for application to the development of ocular dominance columns in the kitten visual cortex.
Spatial Decorrelation in Orientation-Selective Cortical Cells
Authors: Dimitrov Alexander , Cowan Jack D.
Published: July 2002

We propose a model for the lateral connectivity of orientation-selective cells in the visual cortex. We study the properties of the input signal to the visual cortex and find new statistical structures that have not been processed in the retino-geniculate pathway. Using the idea that the system performs redundancy reduction of the incoming signals, we derive the lateral connectivity that will achieve this for a set of orientation-selective local circuits, as well as the complete spatial structure of a network composed of such circuits. We compare the results with various physiological measurements.
Category Learning Through Multimodality Sensing
Authors: de Sa Virginia R. , Ballard Dana H.
Published: July 2002

Humans and other animals learn to form complex categories without receiving a target output, or teaching signal, with each input pattern. In contrast, most computer algorithms that emulate such performance assume the brain is provided with the correct output at the neuronal level or require grossly unphysiological methods of information propagation. Natural environments do not contain explicit labeling signals, but they do contain important information in the form of temporal correlations between sensations to different sensory modalities, and humans are affected by this correlational structure (Howells, 1944; McGurk & MacDonald, 1976; MacDonald & McGurk, 1978; Zellner & Kautz, 1990; Durgin & Proffitt, 1996). In this article we describe a simple, unsupervised neural network algorithm that also uses this natural structure. Using only the co-occurring patterns of lip motion and sound signals from a human speaker, the network learns separate visual and auditory speech classifiers that perform comparably to supervised networks.
A Hierarchical Model of Binocular Rivalry
Authors: Dayan Peter
Published: July 2002

Binocular rivalry is the alternating percept that can result when the two eyes see different scenes. Recent psychophysical evidence supports the notion that some aspects of binocular rivalry bear functional similarities to other bistable percepts. We build a model based on the hypothesis (Logothetis & Schall, 1989; Leopold & Logothetis, 1996; Logothetis, Leopold, & Sheinberg, 1996) that alternation can be generated by competition between top-down cortical explanations for the inputs, rather than by direct competition between the inputs. Recent neurophysiological evidence shows that some binocular neurons are modulated with the changing percept; others are not, even if they are selective between the stimuli presented to the eyes. We extend our model to a hierarchy to address these effects.
A Self-Organizing Neural Network Architecture for Navigation Using Optic Flow
Authors: Cameron Seth , Grossberg Stephen , Guenther Frank H.
Published: July 2002

This article describes a self-organizing neural network architecture that transforms optic flow and eye position information into representations of heading, scene depth, and moving object locations. These representations are used to navigate reactively in simulations involving obstacle avoidance and pursuit of a moving target. The network's weights are trained during an action-perception cycle in which self-generated eye and body movements produce optic flow information, thus allowing the network to tune itself without requiring explicit knowledge of sensor geometry. The confounding effect of eye movement during translation is suppressed by learning the relationship between eye movement outflow commands and the optic flow signals that they induce. The remaining optic flow field is due to only observer translation and independent motion of objects in the scene. A self-organizing feature map categorizes normalized translational flow patterns, thereby creating a map of cells that code heading directions. Heading information is then recombined with translational flow patterns in two different ways to form maps of scene depth and moving object locations. Most of the learning processes take place concurrently and evolve through unsupervised learning. Mapping the learned heading representations onto heading labels or motor commands requires additional structure. Simulations of the network verify its performance using both noise-free and noisy optic flow information.
Optimal Detection of Flash Intensity Differences Using Rod Photocurrent Observations
Authors: Steinmetz Peter N. , Winslow Raimond L.
Published: July 2002

The rod photocurrent contains two noise components that may limit the detectability of flash intensity increments. The limits imposed by the low- and high-frequency noise components were assessed by computing the performance of an optimal detector of increments in flash intensity. The limits imposed by these noise components depend on the interval of observation of the photocurrent signal. When the entire photocurrent signal, lasting 3 or more seconds, is observed, the low-frequency component of the photocurrent noise (attributed to the quantal noise of the incoming light, as well as random isomerizations of enzymes within the phototransduction cascade) is the most significant limitation on detectability. When only the first 380 ms or less is observed, the high-frequency component of the noise (due to the thermal isomerizations of the cGMP-gated channel) presents a significant limit on the detectability of flashes.
A Fast, Compact Approximation of the Exponential Function
Authors: Schraudolph Nicol N.
Published: July 2002

Neural network simulations often spend a large proportion of their time computing exponential functions. Since the exponentiation routines of typical math libraries are rather slow, their replacement with a fast approximation can greatly reduce the overall computation time. This article describes how exponentiation can be approximated by manipulating the components of a standard (IEEE-754) floating-point representation. This models the exponential function as well as a lookup table with linear interpolation, but is significantly faster and more compact.
Uncle Tom's Cabin: Before and After the Jim Crow Era
Authors: Wallace Michele
Published: July 2002

Despite Uncle Tom's Cabin's “extraordinary and global importance as novel, performance, and film”, it is rarely read or taken seriously, except as a negative. But studying Uncle Tom's Cabin can provide a key to “the issues and images of black performance at the turn of the century”—and beyond.
The Debate with Space
Authors: Novarina Valère
Published: July 2002

The French avantgardist's act of writing is a performance. Here he ruminates about his processes of composition. “I write not facing the spectacle but under the theatre, under the boards. Buried as if through a mole's work.”
Evaluation of Personal Agent-Oriented Virtual Society—PAW
Authors: Matsuda Kouichi
Published: July 2002

In recent years, communication networks and computer technologies make it possible to create a cyberspace on the Internet. Recently, several 3-D shared virtual spaces and worlds have been realized in which users can share the same experience in a shared virtual environment. The next important step is to extend these environments into a virtual society.

To realize a virtual society, it is important to obtain a large number of users in a virtual world and evaluate what kind of functions (especially, social functions) and interface should be supported. For this purpose, we constructed a personal agent-oriented virtual society called PAW (Personal Agent World) based on our Community Place system.

PAW is a 3-D personal agent-oriented virtual society. PAW has improved upon past virtual spaces based on avatar and text communication by providing autonomous personal agents that interact with users plus a social and environmental infrastructure. Each user owns a personal agent that acts as user's partner and a mediator in the shared space. PAW was available on the Internet for eight months, during which it attracted hundreds of simultaneous user accesses and thousands of accumulated user accesses. In this paper, we give an architectural and design outline of PAW and the results of a questionnaire survey.
Integrating Sounds and Motions in Virtual Environments
Authors: Hahn James K. , Fouad Hesham , Gritz Larry , Lee Jong Won
Published: July 2002

Sounds are often the result of motions of virtual objects in a virtual environment. Therefore, sounds and the motions that caused them should be treated in an integrated way. When sounds and motions do not have the proper correspondence, the resultant confusion can lessen the effects of each. In this paper, we present an integrated system for modeling, synchronizing, and rendering sounds for virtual environments. The key idea of the system is the use of a functional representation of sounds, called timbre trees. This representation is used to model sounds that are parameterizable. These parameters can then be mapped to the parameters associated with the motions of objects in the environment. This mapping allows the correspondence of motions and sounds in the environment. Representing arbitrary sounds using timbre trees is a difficult process that we do not address in this paper. We describe approaches for creating some timbre trees including the use of genetic algorithms. Rendering the sounds in an aural environment is achieved by attaching special environmental nodes that represent the attenuation and delay as well as the listener effects to the timbre trees. These trees are then evaluated to generate the sounds. The system that we describe runs parallel in real time on an eight-processor SGI Onyx. We see the main contribution of the present system as a conceptual framework on which to consider the sound and motion in an integrated virtual environment.
An Architecture to Support Large Numbers of Computer-Generated Actors for Distributed Virtual Environments
Authors: Stytz Martin R. , Banks Sheila B. , Hutson Larry J. , Santos Eugene
Published: July 2002

A variety of challenges exist in the design of systems that can be used to host a wide variety of computer-generated actors (CGAs) that possess believable behaviors. The challenges arise in the areas of system architecture and design, knowledge-base design, decision-making mechanisms, and the distributed virtual environment (DVE) network interface. These challenges are especially significant if the DVE is to be used for training, because accurate training is essential to the ready application of training experience to real-world situations. The project described in this paper was undertaken to improve the quality of threat CGAs in DVEs utilized for aircrew training. In this paper, we describe the system and the reasons for its genesis. We present the system requirements, system architecture, component-wise decomposition of the system design, and structure of the major components of the decision mechanism. We conclude with a summary of our results to date and recommendations for further research.
Collaborative Task Performance for Learning Using a Virtual Environment
Authors: Bystrom Karl-Erik , Barfield Woodrow
Published: July 2002

This paper describes a study on the sense of presence and task performance in a virtual environment as affected by copresence (one subject working alone versus two subjects working as partners), level of control (control of movement and control of navigation through the virtual environment), and head tracking. Twenty subjects navigated through six versions of a virtual environment and were asked to identify changes in locations of objects within the environment. After each trial, subjects completed a questionnaire designed to assess their level of presence within the virtual environment. Results indicated that collaboration did not increase the sense of presence in the virtual environment, but did improve the quality of the experience in the virtual environment. Level of control did not affect the sense of presence, but subjects did prefer to control both movement and navigation. Head tracking did not affect the sense of presence, but did contribute to the spatial realism of the virtual environment. Task performance was affected by the presence of another individual, by head tracking, and by level of control, with subjects performing significantly more poorly when they were both alone and without control and head tracking. In addition, a factor analysis indicated that questions designed to assess the subjects' experience in the virtual environment could be grouped into three factors: (1) presence in the virtual environment, (2) quality of the virtual environment, and (3) task difficulty.
Assisting the Teleoperation of an Unmanned Underwater Vehicle Using a Synthetic Subsea Scenario
Authors: Lin Qingping , Kuo Chengi
Published: July 2002

Virtual reality (VR) systems serve as a tool for users to become immersed in a virtual world, navigate through it, and interact with the synthetic objects in real time. Successful applications of VR can be found in many fields outside entertainment ranging from science and engineering to education. In this paper, we present our research work on using a synthetic subsea scenario to assist the navigation of a remotely operated vehicle (ROV) in and around an offshore installation. Our approach takes the ROVs position and orientation data from a sonar-based underwater positioning unit and generates a 3-D synthetic subsea navigation scenario that is based on a geometrical model of the offshore installation. It incorporates the “ROV safety domain” concept to ensure that the synthetic subsea scenario conveys sufficient accuracy for ROV navigation. Our research results have positively demonstrated the feasibility of assisting ROV navigation using a synthetic subsea scenario in combination with the ROV safety domain.
Multiobjective Evolutionary Algorithms: Analyzing the State-of-the-Art
Authors: Veldhuizen David A. Van , Lamont Gary B.
Published: July 2002

Solving optimization problems with multiple (often conflicting) objectives is, generally, a very difficult goal. Evolutionary algorithms (EAs) were initially extended and applied during the mid-eighties in an attempt to stochastically solve problems of this generic class. During the past decade, a variety of multiobjective EA (MOEA) techniques have been proposed and applied to many scientific and engineering applications. Our discussion's intent is to rigorously define multiobjective optimization problems and certain related concepts, present an MOEA classification scheme, and evaluate the variety of contemporary MOEAs. Current MOEA theoretical developments are evaluated; specific topics addressed include fitness functions, Pareto ranking, niching, fitness sharing, mating restriction, and secondary populations. Since the development and application of MOEAs is a dynamic and rapidly growing activity, we focus on key analytical insights based upon critical MOEA evaluation of current research and applications. Recommended MOEA designs are presented, along with conclusions and recommendations for future work.
SHAME AND PROPHECY: APPROACHES PAST AND PRESENT
Authors: Stiebert Johanna
Published: July 2002

Shame is widely discussed both in the literature of psychology (in contradistinction to guilt) and social anthropology (in binary opposition with honour, where it is associated particularly with women and public loss of status). Recently, the honour–shame model has been used as heuristic pattern for analysing biblical texts. The focus has been primarily on the patriarchal narratives and Deuteronomistic history; yet the preponderance of shame vocabulary occurs in the prophetic corpus. Here the model proves to be ill fitting. One reason is that it tends to apply to static societies, whereas insofar as social contexts are implied in the Prophets these tend to be depicted as marked by turmoil and chaos attending the exile. In the absence of discussions using models constructed for the purposes of examining situations of social upheaval (such as revolutions or millenarian eruptions) three new approaches are proposed and discussed with regard to Ezekiel 16. The purpose is to probe their suitability for elucidating this baffling text as well as to redress the paucity of prophetic shame studies. The first examines antilanguages; the second grotesque language and the third, deviance amplification.
WHAT DOES 'IT' MEAN? INTERPRETATION AT THE POINT OF NO RETURN IN AMOS 1-2
Authors: Linville James
Published: July 2002

This paper interprets the expression (lit. 'I will not cause him/it to return', Amos 1:3, 6, 9, 11, 13; 2:1, 4, 6) as the result of deliberate ambiguity that forms a rhetorical trap for the reader. This extends not only to the meaning of the individual terms employed and especially the referent of the pronoun suffix, but also to whether the formula is to be read as an assertion or a rhetorical question. The reader may easily agree to any number of complementary readings which look toward the punishment of the six foreign nations, only to be trapped into offering a similar judgment against Judah and Israel. This is complicated by the need to reconcile this with the promise of restoration with which the book closes. Many interpretations of the expression are reviewed and the level of contextual support for each is discussed. Many have strong contextual support in each of the eight cases, while some 'secondary' nuances are recognised. A number of readings construe the expression as denying some form of 'return' to the accused nations, e.g., from exile, or a return to the divine presence for punishment (or salvation). Alternatively, Yahweh may be speaking of the withdrawal of his word of punishment, the impending punishment, or some other related concept. To these numerous popular and plausible readings are added some less familiar ones. The reader's grappling with his or her own interpretation of the expression and the moral implications of Yahweh's severe punishment can be related to the character Amos's own described experiences. Prophecy is inevitable (Amos 3:8). Yet, Amos intercedes successfully (7:1-6). Yahweh's manipulative word games soon reassert the prophecy of destruction (7:7-9; 8:1-2). In the end, however, Yahweh relents (9:11-15). These reversals are already intimated in the instability of . This instability provides a 'trap' to keep the readers fascinated with the divine word and the nature of the bond between Yahweh and Israel.
HADĪTH IN THE RESPONSES OF ISHĀQ B. RĀHWAYH
Authors: Spectorsky Susan
Published: July 2002

The Khorasanian scholar Ibn Rāhwayh (d. 238/853) is known mainly as a traditionist. His teachers were prominent traditionists, he was a colleague of Ibn Hanbal's, he is the author of a Musnad, and his students include Bukharī, Muslim, Abū Dāwūd, Nasā'ī and Tirmidhī. However, he was also a jurist, and his jurisprudence can be studied in a masā'il collection compiled by Ishāq b. Ibrāhīm al-Kawsaj (251/865) who was a younger contemporary of Ibn Rāhwayh's and also one of his students. Below, I analyze a number of Ibn Rāhwayh's responses to show how he actually uses hadīths in his jurisprudence. It turns out that despite his reputation as a traditionist, he does not use hadīths methodically. Although he uses them in his discussion of issues concerning which a body of ikhtilāf had grown up, he depends more on the authority of the Successors and the scholarly community than he does on hadīths from the Prophet.