L’intégration de la prise de décision visuo-motrice et d’action motrice dans des conditions ambiguës

La prise de décision est un mécanisme qui fait intervenir les structures neuronales supérieures afin d’effectuer un lien entre la perception du signal et l’action. Plusieurs travaux qui cherchent à comprendre les mécanismes de la prise de décision sont menés à divers ni- veaux allant de l’analyse comportementale cognitive jusqu'à la modélisation computationnelle. Le but de ce projet a été d’évaluer d’un instant à l’autre comment la variabilité du signal observé («bruit»), influence la capacité des sujets humains à détecter la direction du mouvement dans un stimulus visuel. Dans ces travaux, nous avons éliminé l’une des sources potentielles de variabilité, la variabilité d’une image à l’autre, dans le nombre de points qui portaient les trois signaux de mouvements cohérents (gauche, droite, et aléatoire) dans les stimuli de Kinématogramme de points aléatoires (KPA), c’est-à-dire la variabilité d’origine périphérique. Les stimuli KPA de type « V6 » étaient des stimuli KPA standard avec une variabilité instantanée du signal, et par contre les stimuli KPA de type « V8 », étaient modifiés pour éliminer la variabilité stochastique due à la variabilité du nombre de pixels d’un instant à l’autre qui portent le signal cohérent. Si la performance des sujets, qui correspond à leur temps de réaction et au nombre de bonnes réponses, diffère en réponse aux stimuli dont le nombre de points en mouvement cohérent varie (V6) ou ne varie pas (V8), ceci serait une preuve que la variabilité d’origine périphérique modulerait le processus décisionnel. Par contre, si la performance des sujets ne diffère pas entre ces deux types de stimuli, ceci serait une preuve que la source majeure de variabilité de performance est d’origine centrale. Dans nos résultats nous avons constaté que le temps de réaction et le nombre de bonnes réponses sont modulés par la preuve nette du mouvement cohérent. De plus on a pu établir qu’en éliminant la variabilité d’origine périphérique définit ci-dessus, on n’observe pas réellement de modification dans les enregistrements. Ce qui nous à amené à penser qu’il n y a pas de distinction claire entre la distribution des erreurs et les bonnes réponses effectuées pour chacun des essais entre les deux stimuli que nous avons utilisé : V6 et V8. C’est donc après avoir mesuré la « quantité d’énergie » que nous avons proposé que la variabilité observée dans les résultats serait probablement d’origine centrale.

Opportunities for improvements in flocking models

Flocking is the capacity of coherent movement between multiple animals, including birds. Prominent research into flocking is presented. Particle Swarm Optimisation (PSO) has been the prominent result from research into flocking. It is considered that opportunities for further research in flocking exist. With the potential for automated traffic systems, it is concluded that flocking should be reinvestigated for this purpose.

(Table 1) Iceberg characteristics and start and end date and location of iceberg buoys in the Weddell Sea

The drift of 52 icebergs tagged with GPS buoys in the Weddell Sea since 1999 has been investigated with respect to prevalent drift tracks, sea ice/iceberg interaction, and freshwater fluxes. Buoys were deployed on small- to medium-sized icebergs (edge lengths ? 5 km) in the southwestern and eastern Weddell Sea. The basin-scale iceberg drift of this size class was established. In the western Weddell Sea, icebergs followed a northward course with little deviation and mean daily drift rates up to 9.5 ± 7.3 km/d. To the west of 40°W the drift of iceberg and sea ice was coherent. In the highly consolidated perennial sea ice cover of 95% the sea ice exerted a steering influence on the icebergs and was thus responsible for the coherence of the drift tracks. The northward drift of buoys to the east of 40°W was interrupted by large deviations due to the passage of low-pressure systems. Mean daily drift rates in this area were 11.5 ± 7.2 km/d. A lower threshold of 86% sea ice concentration for coherent sea ice/iceberg movement was determined by examining the sea ice concentration derived from Special Sensor Microwave Imager (SSM/I) and Advanced Microwave Scanning Radiometer for EOS (AMSR-E) satellite data. The length scale of coherent movement was estimated to be at least 200 km, about half the value found for the Arctic Ocean but twice as large as previously suggested. The freshwater fluxes estimated from three iceberg export scenarios deduced from the iceberg drift pattern were highly variable. Assuming a transit time in the Weddell Sea of 1 year, the iceberg meltwater input of 31 Gt which is about a third of the basal meltwater input from the Filchner Ronne Ice Shelf but spreads across the entire Weddell Sea. Iceberg meltwater export of 14.2 × 103 m3 s?1, if all icebergs are exported, is in the lower range of freshwater export by sea ice.

(Quantum-) critical dynamics of magnetoelectric materials

In this thesis the critical dynamics of several magnetoelectric compounds at their phase transition were examined. Mostly measurements of the dielectric properties in the frequency range of below 1 Hz up to 5 GHz were employed to evaluate the critical exponents for both magnetic field and temperature-dependent measurements. Most of the materials that are part of this work show anomalous behavior, especially at very low temperatures where quantum fluctuations are of the order of or even dominate those induced thermally. This anomalous behavior manifests in different forms. In Dy2Ti2O7 we demonstrate the existence of electric dipoles on magnetic monopoles. Here the dynamics at the critical endpoint located at 0.36K and in a magnetic field of 1T parallel to the [111] direction are of special interest. At this critical endpoint the expected critical slowing down of the dynamics could not only not be observed but instead the opposite, critical speeding-up by several orders of magnitude, could be demonstrated. Furthermore, we show that the phase diagram of Dy2Ti2O7 in this field direction can be reproduced solely from the dynamical properties, for example the resonance frequency of the observed relaxation that is connected to the monopole movement. Away from this point of the phase diagram the dynamics are slowing-down with reduction of temperature as one would expect. Additional measurements on Y2Ti2O7, a structurally identical but non-magnetic material, show only slowing down with reduction of temperature and no additional features. A possible explanation for the observed critical speeding-up is a coherent movement of magnetic monopoles close to the critical field that increases the resonance frequency by reducing the damping of the process. LiCuVO4 on the other hand behaves normally at its phase transition as long as the temperature is higher than 0.4 K. In this temperature regime the dynamics show critical slowing-down analogous to classical ferroelectric materials. This analogy extends also towards higher frequencies where the permittivity displays a ‘dispersion’ minimum that is temperature-dependent but of the order of 2 GHz. Below 0.4K the observed behavior changes drastically. Here we found no longer relaxational behavior but instead an excitation with very low energy. This low energy excitation was predicted by theory and is caused by nearly gapless soliton excitations within the 1D Cu2+ chains of LiCuVO4. Finally, in TbMnO3 the dynamics of the phase transition into the multiferroic phase was observed at roughly 27 K, a much higher temperature compared to the other materials. Here the expected critical slowing-down was observed, even though in low-frequency measurements this transition into the ferroelectric phase is overshadowed by the so-called c-axis relaxation. Therefore, only frequencies above 1MHz could be used to determine the critical exponents for both temperatureand magnetic-field-dependent measurements. This was done for both the peak frequency as well as the relaxation strength. In TbMnO3 an electromagnetic soft-mode with small optical weight causes the observed fluctuations, similar to the case of multiferroic MnWO4.

The Emerging Church Movement: A Sociological Assessment

With so many voices, groups, and organizations participating in the Emerging Church Movement (ECM), few are willing to “define” it, though authors have offered various definitions. Emerging Christians themselves do not offer systematic or coherent definitions, which contributes to frustration in isolating it as a coherent group – especially for sociologists who strive to define and categorize. In presenting our understanding of this movement, we categorize Emerging Christianity as an orientation rather than an identity, and focus on the diverse practices within what we describe as “pluralist congregations” (often called “gatherings,” “collectives” or “communities” by Emerging Christians themselves). This leads us to define the ECM as a creative, entrepreneurial religious movement that strives to achieve social legitimacy and spiritual vitality by actively disassociating from its roots in conservative, evangelical Christianity. Our findings are extensively developed in The Deconstructed Church: Understanding Emerging Christianity (Marti and Ganiel 2014).

Meaning in movement : a gestural design game

This paper describes a design game that we called 'Meaning in Movement'. The purpose was to explore notions of professional dental practice with dental practioners in terms of gestures, actions and movements. The game represents a first step towards involving gestures, actions and movements in a design dialog with practioners for the purpose of designing future interactive systems which are more appropriate to the type of skilful actions and richly structured environments of dentists and dental assistants.

Effect of Pedestrian Movement on MIMO-OFDM Channel Capacity in an Indoor Environment

Effects of pedestrian movement on multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) channel capacity have been investigated using experiment and simulation. The experiment was conducted at 5.2 GHz by a MIMO-OFDM packet transmission demonstrator using four transmitters and four receivers built in-house. Geometric optics based ray tracing technique was used to simulate the experimental scenarios. Changes in the channel capacity dynamic range have been analysed for different number of pedestrian (0-3) and antennas (2-4). Measurement and simulation results show that the dynamic range increases with the number of pedestrian and the number of antennas on the transmitter and receiver array.

Variations in MIMO-OFDM channel capacity due to random human movement in an indoor environment

Channel measurements and simulations have been carried out to observe the effects of pedestrian movement on multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) channel capacity. An in-house built MIMO-OFDM packet transmission demonstrator equipped with four transmitters and four receivers has been utilized to perform channel measurements at 5.2 GHz. Variations in the channel capacity dynamic range have been analysed for 1 to 10 pedestrians and different antenna arrays (2 × 2, 3 × 3 and 4 × 4). Results show a predicted 5.5 bits/s/Hz and a measured 1.5 bits/s/Hz increment in the capacity dynamic range with the number of pedestrian and the number of antennas in the transmitter and receiver array.

A phenomenological explication of dream interpretation among rural and urban Nguni people

Psychologists investigating dreams in non-Western cultures have generally not considered the meanings of dreams within the unique meaning-structure of the person in his or her societal context. The majority of dream studies in African societies are no exception. Researchers approaching dreams within rural Xhosa and Zulu speaking societies have either adopted an anthropological or a psychodynamic orientation. The latter approach particularly imposes a Western perspective in the interpretation of dream material. There have been no comparable studies of dream interpretation among urban blacks participating in the African Independent Church Movement. The present study focuses on the rural Xhosa speaking people and the urban black population who speak one of the Nguni languages and identify with the African Independent Church Movement. The study is concerned with understanding the meanings of dreams within the cultural context in which they occur. The specific aims of the study are: 1. To explicate the indigenous system of dream interpretation as revealed by acknowledged dream experts. 2. To examine the commonalities and the differences between the interpretation of dreams in two groups, drawn from a rural and urban setting respectively. 3. To elaborate upon the life-world of the participants by the interpretations gained from the above investigation. One hundred dreams and interpretations are collected from two categories of participants referred to as the Rural Group and the Urban Group. The Rural Group is made up of amagqira [traditional healers] and their clients, while the Urban Group consists of prophets and members of the African Independent Churches. Each group includes acknowledged dream experts. A phenomenological methodology is adopted in explicating the data. The methodological precedure involves a number of rigorous stages of expl ication whereby the original data is reduced to Constituent Profiles leading to the construction of a Thematic Index File. By searching and reflect ing upon the data, interpretative themes are identified. These themes are explicated to provide a rigorous description of the interpretative-reality of each group. Themes explicated w i thin the Rural Group are: the physiognomy of the dreamer's life-world as revealed by ithongo, the interpretation of ithongo as revealed through action, the dream relationship as an anticipatory mode-of-existence, iphupha as disclosing a vulnerable mode-of-being, human bodiliness as revealed in dream interpretations and the legitimation of the interpretative-reality within the life-world. Themes explicated within the Urban Group are: the phys iognomy of the dreamer's life-world revealed in their dream-existence, the interpretative-reality revealed through the enaction of dreams, tension between the newer Christian-based cosomology and the traditional cultural-based cosmology, a moral imperative, prophetic perception and human bodiliness, as revealed in dream interpretations and the legitimation of the interpretative-reality within the life-world. The essence of the interpretative-reality of both groups is very similar and is expressed in the notion of relatedness to a cosmic mode-of-being. The cosmic mode-of-being includes a numinous dimension which is expressed through divine presence in the form of ancestors, Holy Spirit or God. These notions cannot be apprehended by theoretical constructs alone but may be grasped and given form in meaning-disclosing intuitions which are expressed in the lifeworld in terms of bodiliness, revelatory knowledge, action and healing. Some differences b e tween the two groups are evident and reveal some conflict between the monotheistic Christian cosmology and the traditional cosmology. Unique aspects of the interpetative-reality of the Urban Group are expressed in terms of difficulties in the urban social environment and the notion of a moral imperative. It is observed that cul tural self-expression based upon traditional ideas continues to play a significant role in the urban environment. The apparent conflict revealed between the respective cosmologies underlies an integration of the aditional meanings with Christian concepts. This finding is consistent with the literature suggesting that the African Independent Church is a syncretic movement. The life-world is based upon the immediate and vivid experience of the numinous as revealed in the dream phenomenon. The participants' approach to dreams is not based upon an explicit theory, but upon an immediate and pathic understanding of the dream phenomenon. The understanding is based upon the interpreter's concrete understanding of the life-world, which includes the possibility of cosmic integration and continuity between the personal and transpersonal realms of being. The approach is characterized as an expression of man's primordial attunement with the cosmos. The approach of the participants to dreams may not b e consistent with a Western rational orientation, but neverthele ss, it is a valid approach . The validity is based upon the immediate life-world of experience which is intelligible, coherent, and above all, it is meaning-giving in revealing life-possibility within the context of human existence.

The problem of measurement indeterminacy in complex neurobiological movement systems

In the study of complex neurobiological movement systems, measurement indeterminacy has typically been overcome by imposing artificial modelling constraints to reduce the number of unknowns (e.g., reducing all muscle, bone and ligament forces crossing a joint to a single vector). However, this approach prevents human movement scientists from investigating more fully the role, functionality and ubiquity of coordinative structures or functional motor synergies. Advancements in measurement methods and analysis techniques are required if the contribution of individual component parts or degrees of freedom of these task-specific structural units is to be established, thereby effectively solving the indeterminacy problem by reducing the number of unknowns. A further benefit of establishing more of the unknowns is that human movement scientists will be able to gain greater insight into ubiquitous processes of physical self-organising that underpin the formation of coordinative structures and the confluence of organismic, environmental and task constraints that determine the exact morphology of these special-purpose devices.