Combined space-variant maps for optical-flow-based navigation

A robot navigating in an unstructured environment needs to avoid obstacles in its way and determine free spaces through which it can safely pass. We present here a set of optical-flow-based behaviors that allow a robot moving on a ground plane to perform these tasks. The behaviors operate on a purposive representation of the environment called the “virtual corridor” which is computed as follows: the images captured by a forward-facing camera rigidly attached to the robot are first remapped using a space-variant transformation. Then, optical flow is computed from the remapped image stream. Finally, the virtual corridor is extracted from the optical flow by applying simple but robust statistics. The introduction of a space-variant image preprocessing stage is inspired by biological sensory processing, where the projection and remapping of a sensory input field onto higher-level cortical areas represents a central processing mechanism. Such transformations lead to a significant data reduction, making real-time execution possible. Additionally, they serve to “re-present” the sensory data in terms of ecologically relevant features, thereby simplifying the interpretation by subsequent processing stages. In accordance with these biological principles we have designed a space-variant image transformation, called the polar sector map, which is ideally suited to the navigational task. We have validated our design with simulations in synthetic environments and in experiments with real robots. Received: 1 July 1999 / Accepted in revised form: 20 March 2000     

Responses to non-locomotive prey models by the praying mantis,Tenodera angustipennis Saussure

Adult females of the praying mantisTenodera angustipennis were presented with computer-generated images, and the attractiveness of “non-locomotive” prey models was examined. Mantises fixated and struck the “body and leg” model (consisting of an immobile black square on a white background with 2 black lines oscillating randomly at its sides) more frequently than the “leg” model (only oscillating lines) or the “body” model (static square only). This indicates that the model consisting of a static object and moving lines effectively elicits mantis strike behavior, although it is “non-locomotive.”     

Elements for a general memory structure: properties of recurrent neural networks used to form situation models

We study how individual memory items are stored assuming that situations given in the environment can be represented in the form of synaptic-like couplings in recurrent neural networks. Previous numerical investigations have shown that specific architectures based on suppression or max units can successfully learn static or dynamic stimuli (situations). Here we provide a theoretical basis concerning the learning process convergence and the network response to a novel stimulus. We show that, besides learning “simple” static situations, a nD network can learn and replicate a sequence of up to n different vectors or frames. We find limits on the learning rate and show coupling matrices developing during training in different cases including expansion of the network into the case of nonlinear interunit coupling. Furthermore, we show that a specific coupling matrix provides low-pass-filter properties to the units, thus connecting networks constructed by static summation units with continuous-time networks. We also show under which conditions such networks can be used to perform arithmetic calculations by means of pattern completion.     

On-line feedback-based automatic resource configuration for distributed applications

A key problem in executing performance critical applications on distributed computing environments (e.g. the Grid) is the selection of resources. Research related to “automatic resource selection” aims to allocate resources on behalf of users to optimize the execution performance. However, most of current approaches are based on the static principle (i.e. resource selection is performed prior to execution) and need detailed application-specific information. In the paper, we introduce a novel on-line automatic resource selection approach. This approach is based on a simple control theory: the application continuously reports the Execution Satisfaction Degree (ESD) to the middleware Application Agent (AA), which relies on the reported ESD values to learn the execution behavior and tune the computing environment by adding/replacing/deleting resources during the execution in order to satisfy users’ performance requirements. We introduce two different policies applied to this approach to enable the AA to learn and tune the computing environment: the Utility Classification policy and the Desired Processing Power Estimation (DPPE) policy. Each policy is validated by an iterative application and a non-iterative application to demonstrate that both policies are effective to support most kinds of applications.     

Social Defeat or Social Resistance? Reaction to Fear of Crime and Violence Among People with Severe Mental Illness Living in Urban ‘Recovery Communities’

This article is propelled by recent theory positing that ‘social defeat’ is a common experience for people with severe mental illness, potentially affecting course and outcome. The primary objective is to investigate how far fear of crime and violence contributes toward ‘social defeat’ among people with mental illness. This is done through examining 6 years of ethnographic data collected from a sample of urban-dwelling people with severe mental illness, all securely-housed in apartments located in small scale “recovery communities.” Findings suggest that many participants living in the highest crime neighborhoods report that they deliberately restrict their temporal and spatial movement as a consequence of such crime. This hinders aspects of their recovery. Nevertheless, participants actively confront the nefarious affects of neighborhood crime by engaging in various empowering strategies of resistance. These include confronting disruptive people, fortifying homes, moving around the neighborhood in small groups and carrying objects such as umbrellas and canes that can be used in self-defense. Some reported that fear of crime directly contributed to the development of a rich and gratifying domestic life, centered on hospitality and religion. I conclude that participants partake in valiant and durable “social resistance,” and may better be perceived as imaginative and resourceful resistors, rather than passive victims of “social defeat.” An influential factor fostering such resistance is the “recovery community’ itself, which creates secure and reliable housing within a micro-community in which participants could thrive.     

Overcoming Obstacles to Evolution Education: In the Beginning

Science teachers are on the front lines of the evolution wars, not only in prominent court cases but also in everyday classroom situations. Owing both to religious opposition to and common misconceptions about evolution, science teachers are in need of support and sometimes guidance. Staff from the National Center for Science Education are looking forward to contributing a regular column, “Overcoming obstacles to evolution education,” to Evolution: Education and Outreach, which will discuss a variety of obstacles to effective evolution education and suggest ways of overcoming them.     

Spatial organization of receptive fields and dynamic peculiarities of neurons of the extrastriate area 21a of the cat cerebral cortex

In neurons of the extrastriate area 21a of the cat cortex, we examined the mode of initiation and peculiarities of inhibitory components in responses of these units to visual stimulation. About 31% of the studied neurons generated complex responses to mobile visual stimuli; the parameters of inhibitory components in these responses (location and duration) were different and depended on the contrast, dimension, and shape of the visual stimuli presented. We compared in detail the stationary spatial organization of receptive fields (RFs) and parameters of neuronal responses to presentation of moving stimuli in order to estimate the correlation between static and dynamic characteristics of the activity generated by the studied neurons. Our experiments showed that in most cases the neurons possessing identical homogeneous static characteristics of the RFs with off, on-off, and on responses could demonstrate quite different patterns of responses to moving stimuli, which differed from each other both in localization of inhibitory zones and discharge centers within the RFs and in time parameters of the components of these responses. The obtained data allow us to hypothesize that the dynamic characteristics of visually sensitive neurons in the extrastriate associative cortical regions are formed due to complex processes of spatial interaction between their “classic” RFs and the surrounding visual space. Neirofiziologiya/Neurophysiology, Vol. 40, No. 2, pp. 119–129, March–April, 2008.     

Competitive dominance among sessile marine organisms in a high Arctic boulder community

In most hard substrate environments, space is a limiting resource for sessile organisms. Competition for space is often high and is a structuring force within the community. In the Beaufort Sea’s Boulder Patch, crustose coralline red algae are major space occupiers. This research determined if coralline algae were competitively dominant over other sessile organisms. To test this hypothesis, overgrowth was documented in terms of “winners” and “losers” on the contact borders between different species. Crustose corallines occurred in over 80% of the observed interactions but were only winners in approximately half of them. Most frequently, bryozoans, tunicates, and sponges were superior competitors over crustose corallines, while at the same time these invertebrate groups were among the least abundant space occupiers.     

Self-assembly of neural networks viewed as swarm intelligence

While self-assembly is a fairly active area of research in swarm intelligence, relatively little attention has been paid to the issues surrounding the construction of network structures. In this paper we extend methods developed previously for controlling collective movements of agent teams to serve as the basis for self-assembly or “growth” of networks, using neural networks as a concrete application to evaluate our approach. Our central innovation is having network connections arise as persistent “trails” left behind moving agents, trails that are reminiscent of pheromone deposits made by agents in ant colony optimization models. The resulting network connections are thus essentially a record of agent movements. We demonstrate our model’s effectiveness by using it to produce two large networks that support subsequent learning of topographic and feature maps. Improvements produced by the incorporation of collective movements are also examined through computational experiments. These results indicate that methods for directing collective movements can be adopted to facilitate network self-assembly.     

Estimation of relative contribution of “mobile phycobilisome” and “energy spillover” in the light–dark induced state transition in Spirulina platensis

Previously, it was clarified that phycobilisome (PBS) mobility and energy spillover were both involved in light-to-dark induced state transitions of intact Spirulina platensis cells. In this work, by taking advantage of the characteristic fluorescence spectra of photosystem I (PSI) trimers and monomers as indicators, the relative contributions for the “mobile PBS” and “energy spillover” are quantitatively estimated by separating the fluorescence contribution of PBS mobility from that of PSI oligomeric change. Above the phase transition temperature (T _PT) of the membrane lipids, the relative proportion of the contributions is invariable with 65% of “mobile PBS” and 35% of “energy spillover”. Below T _PT, the proportion for the “mobile PBS” becomes larger under lowering temperature even reaching 95% with 5% “energy spillover” at 0°C. It is known that lower temperature leads to a further light state due to a more reduced or oxidized PQ pool. Based on the current result, it can be deduced that disequilibrium of the redox state of the PQ pool will trigger PBS movement instead of change in the PSI oligomeric state.     

Deductive biology—Some cautious steps

For certain environments, the Darwinian model allows unique prediction of a function that any surviving system adapted to such an environment has to perform. This is the case for those environments that determine a “survival functional” of position in space-time of known shape. Purely temporal survival functionals can be distinguished from spatial and mixed ones. In each case, there exists an optimum path in combined physical and (reduced) metabolic space. Dependent on the admissible error, approximate solutions of different complexity are sufficient. All solutions possess an afferent, a central, and an efferent part. Within this general frame, specific, “probably simplest”, solutions are proposed for adaptive chemotaxis, insect locomotion, lower vertebrates locomotion, higher vertebrates locomotion, chronobiological systems, and immune systems, respectively—or rather, for the underlying functionals. Presented at the Society for Mathematical Biology Meeting, University of Pennsylvania, Philadelphia, August 19–21, 1976.     

Modulation of Visually Evoked Postural Responses by Contextual Visual,Haptic and Auditory Information: A ‘Virtual Reality Check’

Externally generated visual motion signals can cause the illusion of self-motion in space (vection) and corresponding visually evoked postural responses (VEPR). These VEPRs are not simple responses to optokinetic stimulation, but are modulated by the configuration of the environment. The aim of this paper is to explore what factors modulate VEPRs in a high quality virtual reality (VR) environment where real and virtual foreground objects served as static visual, auditory and haptic reference points. Data from four experiments on visually evoked postural responses show that: 1) visually evoked postural sway in the lateral direction is modulated by the presence of static anchor points that can be haptic, visual and auditory reference signals; 2) real objects and their matching virtual reality representations as visual anchors have different effects on postural sway; 3) visual motion in the anterior-posterior plane induces robust postural responses that are not modulated by the presence of reference signals or the reality of objects that can serve as visual anchors in the scene. We conclude that automatic postural responses for laterally moving visual stimuli are strongly influenced by the configuration and interpretation of the environment and draw on multisensory representations. Different postural responses were observed for real and virtual visual reference objects. On the basis that automatic visually evoked postural responses in high fidelity virtual environments should mimic those seen in real situations we propose to use the observed effect as a robust objective test for presence and fidelity in VR.     

Inertial electrostatic confinement and nuclear fusion in the interelectrode plasma of a nanosecond vacuum discharge. I: Experiment

Properties of an aerosol substance with a high power density in the interelectrode space of a nano- second vacuum discharge are studied. The possibilities of emission and/or trapping of fast ions and hard X-rays by ensembles of clusters and microparticles are analyzed. The possibility of simultaneous partial trapping (diffusion) of X-rays and complete trapping of fast ions by a cluster ensemble is demonstrated experimentally. Due to such trapping, the aerosol ensemble transforms into a “dusty” microreactor that can be used to investigate a certain class of nuclear processes, including collisional DD microfusion. Operating regimes of such a microreactor and their reproducibility were studied. On the whole, the generation efficiency of hard X-rays and neutrons in the proposed vacuum discharge with a hollow cathode can be higher by two orders of magnitude than that in a system “high-power laser pulse-cluster cloud.” Multiply repeated nuclear fusion accompanied by pulsating DD neutron emission was reproducibly detected in experiment. Ion acceleration mechanisms in the interelectrode space and the fundamental role of the virtual cathode in observed nuclear fusion processes are discussed.     

Criminal Law as It Pertains to Patients Suffering from Psychiatric Diseases

The McNaughton rules for determining whether a person can be successfully defended on the grounds of mental incompetence were determined by a committee of the House of Lords in 1843. They arose as a consequence of the trial of Daniel McNaughton for the killing of Prime Minister Sir Robert Peel’s secretary. In retrospect it is clear that McNaughton suffered from schizophrenia. The successful defence of McNaughton on the grounds of mental incompetence by his advocate Sir Alexander Cockburn involved a profound shift in the criteria for such a defence, and was largely based on the then recently published “scientific” thesis of the great US psychiatrist Isaac Ray, entitled A Treatise on the Medical Jurisprudence of Insanity. Subsequent discussion of this defence in the House of Lords led to the McNaughton rules, still the basis of the defence of mental incompetence in the courts of much of the English-speaking world. This essay considers one of these rules in the light of the discoveries of cognitive neuroscience made during the 160 years since Ray’s treatise. A major consideration is the relationship between “the power of self-control” and “irresistible impulse” as conceived by Cockburn on the one hand, and by cognitive neuroscience on the other. The essay concludes with an analysis of the notion of “free will” and of the extent to which a subject can exert restraint in the absence of particular synaptic connections in the brain.     

Saprotrophic cord systems: dispersal mechanisms in space and time

In natural terrestrial environments, nutrients are often patchily and sparsely distributed, and the microclimate is constantly changing both temporally and spatially. To survive, fungi must be able to transfer to a new resource before the nutrient supplies in their current food base are exhausted. While the majority of fungi propagate as spores, some basidiomycetes can grow out of a resource as mycelium in search of new resources. The mycelium of these fungi typically aggregates to form linear organs, termed cords or rhizomorphs, that ramify at the soil-litter interface in forests, interconnecting disparate litter components to form extensive (many square meters or even hectares), long-lived (many years) systems. These mycelial systems form effective dispersal mechanisms in space and time. This article reviews the two main, but not mutually exclusive, mycelial dispersal (resource capture) strategies: (1) a “sit and wait” strategy, whereby a large mycelial network waits for resources to land on it and then actively colonises those resources; and (2) growing and searching actively for new resources. The way in which mycelia balance exploration and nutrient transport, and robustness to damage, against “cost” of production and speed with which an area can be colonised, is explored using techniques borrowed from graph theory and statistical mechanics.     

Voiceprint identification and its application to sociological studies of wild Japanese monkeys (Macaca fuscata yakui)

Japanese monkeys often exchange the particular vocal sound, “coo,” especially when they feed or move as a group. It was considered that the “coo” sound had no positive social meaning, perhaps because the “coo” sound network and its function were hidden behind other behavioral observations. For identification of the vocalizer only from hearing the “coo” sound, three phonetic values, i.e., the “fundamental,” “duration,” and “formants,” plus other characteristics were used as indices of voiceprints. The results indicated that these were effective for identifying the vocalizer in two-thirds of the adults in the study troop which was composed of 12 adults and 16 immature members. The “coo” sound exchange network among the troop members (adults) was drawn on the basis of the voiceprint identification. The network showed three characteristics as follows: (1) matriarchs of the kin-groups frequently exchanged “coo” sounds with each other; (2) the other females exchanged “coo” sounds mostly within their own kin-groups; and (3) males seldom participated in the “coo” sound exchange. This suggests that “coo” sound exchange plays a central role for the matriarch of kin-groups in binding each kin-group and, ultimately, in binding all members together into an organized troop.     

Generic properties of combinatory maps: Neutral networks of RNA secondary structures

Random graph theory is used to model and analyse the relationship between sequences and secondary structures of RNA molecules, which are understood as mappings from sequence space into shape space. These maps are non-invertible since there are always many orders of magnitude more sequences than structures. Sequences folding into identical structures formneutral networks. A neutral network is embedded in the set of sequences that arecompatible with the given structure. Networks are modeled as graphs and constructed by random choice of vertices from the space of compatible sequences. The theory characterizes neutral networks by the mean fraction of neutral neighbors (λ). The networks are connected and percolate sequence space if the fraction of neutral nearest neighbors exceeds a threshold value (λ>λ*). Below threshold (λ<λ*), the networks are partitioned into a largest “giant” component and several smaller components. Structure are classified as “common” or “rare” according to the sizes of their pre-images, i.e. according to the fractions of sequences folding into them. The neutral networks of any pair of two different common structures almost touch each other, and, as expressed by the conjecture ofshape space covering sequences folding into almost all common structures, can be found in a small ball of an arbitrary location in sequence space. The results from random graph theory are compared to data obtained by folding large samples of RNA sequences. Differences are explained in terms of specific features of RNA molecular structures. Deicated to professor Manfred Eigen     

Engrained experience—a comparison of microclimate perception schemata and microclimate measurements in Dutch urban squares

Acceptance of public spaces is often guided by perceptual schemata. Such schemata also seem to play a role in thermal comfort and microclimate experience. For climate-responsive design with a focus on thermal comfort it is important to acquire knowledge about these schemata. For this purpose, perceived and “real” microclimate situations were compared for three Dutch urban squares. People were asked about their long-term microclimate perceptions, which resulted in “cognitive microclimate maps”. These were compared with mapped microclimate data from measurements representing the common microclimate when people stay outdoors. The comparison revealed some unexpected low matches; people clearly overestimated the influence of the wind. Therefore, a second assumption was developed: that it is the more salient wind situations that become engrained in people’s memory. A comparison using measurement data from windy days shows better matches. This suggests that these more salient situations play a role in the microclimate schemata that people develop about urban places. The consequences from this study for urban design are twofold. Firstly, urban design should address not only the “real” problems, but, more prominently, the “perceived” problems. Secondly, microclimate simulations addressing thermal comfort issues in urban spaces should focus on these perceived, salient situations.     

From “Lists of Traits” to “Open-Mindedness”: Emerging Issues in Cultural Competence Education

The incorporation of “culture” into U.S. biomedicine has been increasing at a rapid pace over the last several decades. Advocates for “cultural competence” point to changing patient demographics and growing health disparities as they call for improved educational efforts that train health providers to care for patients from a variety of backgrounds. Medical anthropologists have long been critical of the approach to “culture” that emerges in cultural competence efforts, identifying an essentialized, static notion of culture that is conflated with racial and ethnic categories and seen to exist primarily among exotic “Others.” With this approach, culture can become a “list of traits” associated with various racial and ethnic groups that must be mastered by health providers and applied to patients as necessary. This article uses an ethnographic examination of cultural competence training to highlight recent efforts to develop more nuanced approaches to teaching culture. I argue that much of contemporary cultural competence education has rejected the “list of traits” approach and instead aims to produce a new kind of health provider who is “open-minded,” willing to learn about difference, and treats each patient as an individual. This shift, however, can ultimately reinforce behavioral understandings of culture and draw attention away from the social conditions and power differentials that underlie health inequalities.