Gap crossing is a regular locomotor activity for arboreal animals. The distance between branches likely plays a role in determining whether an animal is capable of crossing a given gap, and what locomotor behavior it uses to do so. Yet, despite the importance of gap distance as a physical parameter influencing gap crossing behavior, the precise relationships between gap distance and movement kinematics have been explored in only a very small number of species. One particularly interesting group of arboreal inhabitants are the flying snakes (Chrysopelea). This species is able to use a dynamic "J-loop" movement to launch its glides, but it is not known whether it is also capable of using such jumps to cross smaller gaps between tree branches. This dissertation addresses this knowledge gap, and investigates the influence of gap distance on crossing behavior and kinematics in three closely-related species of snake: Chrysopelea paradisi, a species of flying snake, and two species from the sister genus, Dendrelaphis, neither of which can glide. Chapter 2 is a literature review of the biomechanics of gap crossing, specifically focusing on the role played by gap distance, and establishes the context for the rest of the work. Chapter 3 presents a detailed study of how increasing gap size influences the behavior and kinematics of gap crossing in C. paradisi, showing that this species uses increasingly dynamic movements to cross gaps of increasing size. Chapter 4 explores the same relationships between gap size and kinematics in D. punctulatus and D. calligastra, revealing remarkable similarities between the three species, suggesting the possibility that dynamic gap crossing may have evolved prior to gliding in this clade. Finally, chapter 5 addresses the role played by gap distance in limiting the non-dynamic, cantilever movements used by these species to cross small gaps, comparing observed stopping distances to those predicted by various torque-related limitations. / Doctor of Philosophy / To successfully cross a gap, an animal must be able to reach or jump from one side to the other. Animals who live in trees must do this quite frequently, as they live among the branches and there are often not connected paths from one place to another. But we don't know very much about how the distance between two structures (the "gap distance") affects the ways an animal moves between them. In this dissertation, I explore how gap distance changes the way a few special species of snakes cross a gap. The species I am studying are special because one species, the paradise tree snake, can glide. Because this 'flying' snake launches its glides by doing a big jump, it is possible that the snake can also jump between tree branches, but this question has never been examined before. We also don't know how the ability to do big jumps evolved, so I studied how distance affects the way two very closely related species of snake, the common tree snake and the northern tree snake, cross gaps. By looking at all of these species, we can understand more about what kinds of behavior are specific to the flying snakes, and which are present in related species. Finally, I also explore how gap distance limits the way the snakes cross gaps when they are not jumping. When the snakes do not jump, they have to hold themselves out straight off the end of a branch. This requires a lot of muscular effort, which means they can't go as far. The fact that the non-jumping behavior is distance-limited might help explain why the snakes need to jump. Altogether, the projects in this study help us understand how gap distance influences what behavior an animal chooses to cross the gap, and increases our knowledge of how flying snakes and their relatives cross gaps in particular.

<p>Uppsatsen belyser fysikundervisning ur ett kulturperspektiv. En multivariatanalys –</p><p>principalkomponentsanalys – har genomförts för att kartlägga fysikundervisningskulturer på</p><p>tidigare respektive senare år inom grundskolan. Syftet är att undersöka vilka likheter och</p><p>skillnader som finns mellan olika fysikundervisningskulturer för att – med hjälp av tidigare</p><p>forsking och litteratur – se vilka möjligheter och problem som kan uppstå för elever och lärare</p><p>i och med dessa fysikundervisningskulturer. Vi har utgått från begreppet border-crossing för</p><p>att behandla de kulturövergångar som kan uppstå när elever byter lärare och vilka</p><p>konsekvenser detta får för elever och lärare.</p><p>Undersökningen har funnit, beskrivit och jämfört fyra fysikundervisningskulturer:</p><p>’Praktikerna’, ’Ämnesinriktade’, ’Anpassarna’ och ’Återkopplarna’. Dessa</p><p>fysikundervisningskulturer beror inte på kön, ålder, ämnesbehörighet eller erfarenhet. Det</p><p>finns dock ett samband mellan vilka årskurser lärarna undervisar på men detta samband gäller</p><p>endast ’Anpassarna’ och ’Praktikerna’. Undersökningen har funnit att ’Ämnesinriktade’ och</p><p>’Anpassarna’ har inslag av tidigare beskriven vetenskapskultur. Undersökningen fann att</p><p>’Återkopplarna’ är en blandning av de andra tre funna fysikundervisningskulturerna. Eftersom</p><p>det uppstår kulturövergångar mellan dessa fysikundervisningskulturer skapar detta problem i</p><p>form av att elever och lärare inte känner igen varandras kulturer. Dessa kulturövergångar är</p><p>beskrivna ur både elev- och lärarperspektiv i undersökningen.</p> / <p>This essay surveys physics science education in the light of cultures. A multivariate analysis –</p><p>principal component analysis – has been used to map out the different cultures in middle</p><p>school and high school. The main purpose of this essay is to examine differences and</p><p>similarities between the different physics educational cultures found in the survey. Through</p><p>examining literature and prior research, it is also the purpose to examine what possibilities</p><p>and problems these physics educational cultures might impose on students and teachers.</p><p>Border-crossing has been a central concept in explaining how possible cultural bordercrossings</p><p>might affect the teachers and pupils.</p><p>The survey has found four different kinds of physics educational cultures which are:</p><p>‘Praktikerna’, ‘Ämnesinriktade’, ‘Anpassarna’ and ‘Återkopplarna’. These physics</p><p>educational cultures are not dependent of sex, age, appropriate teacher education or</p><p>experience. However there is a connection between which grades the teacher educates but</p><p>only for the physics educational cultures ‘Anpassarna’ and ‘Praktikerna’. The survey also</p><p>discovered that the physics educational cultures ‘Ämnesinriktade’ and ‘Anpassarna’ has to</p><p>some degree a connection to earlier examined science-cultures. ‘Återkopplarna’ seems to be a</p><p>mixture of the other three described physics educational cultures. Since cultural bordercrossings</p><p>do occur between the described educational cultures, the problems associated with</p><p>border-crossings also exist. The problems which are associated with border-crossings are: that</p><p>pupils and teachers don’t recognize each other’s physics educational cultures. These bordercrossings</p><p>are described in light of both the teachers’ points of view and the pupils’ points of</p><p>view.</p>

Uppsatsen belyser fysikundervisning ur ett kulturperspektiv. En multivariatanalys – principalkomponentsanalys – har genomförts för att kartlägga fysikundervisningskulturer på tidigare respektive senare år inom grundskolan. Syftet är att undersöka vilka likheter och skillnader som finns mellan olika fysikundervisningskulturer för att – med hjälp av tidigare forsking och litteratur – se vilka möjligheter och problem som kan uppstå för elever och lärare i och med dessa fysikundervisningskulturer. Vi har utgått från begreppet border-crossing för att behandla de kulturövergångar som kan uppstå när elever byter lärare och vilka konsekvenser detta får för elever och lärare. Undersökningen har funnit, beskrivit och jämfört fyra fysikundervisningskulturer: ’Praktikerna’, ’Ämnesinriktade’, ’Anpassarna’ och ’Återkopplarna’. Dessa fysikundervisningskulturer beror inte på kön, ålder, ämnesbehörighet eller erfarenhet. Det finns dock ett samband mellan vilka årskurser lärarna undervisar på men detta samband gäller endast ’Anpassarna’ och ’Praktikerna’. Undersökningen har funnit att ’Ämnesinriktade’ och ’Anpassarna’ har inslag av tidigare beskriven vetenskapskultur. Undersökningen fann att ’Återkopplarna’ är en blandning av de andra tre funna fysikundervisningskulturerna. Eftersom det uppstår kulturövergångar mellan dessa fysikundervisningskulturer skapar detta problem i form av att elever och lärare inte känner igen varandras kulturer. Dessa kulturövergångar är beskrivna ur både elev- och lärarperspektiv i undersökningen. / This essay surveys physics science education in the light of cultures. A multivariate analysis – principal component analysis – has been used to map out the different cultures in middle school and high school. The main purpose of this essay is to examine differences and similarities between the different physics educational cultures found in the survey. Through examining literature and prior research, it is also the purpose to examine what possibilities and problems these physics educational cultures might impose on students and teachers. Border-crossing has been a central concept in explaining how possible cultural bordercrossings might affect the teachers and pupils. The survey has found four different kinds of physics educational cultures which are: ‘Praktikerna’, ‘Ämnesinriktade’, ‘Anpassarna’ and ‘Återkopplarna’. These physics educational cultures are not dependent of sex, age, appropriate teacher education or experience. However there is a connection between which grades the teacher educates but only for the physics educational cultures ‘Anpassarna’ and ‘Praktikerna’. The survey also discovered that the physics educational cultures ‘Ämnesinriktade’ and ‘Anpassarna’ has to some degree a connection to earlier examined science-cultures. ‘Återkopplarna’ seems to be a mixture of the other three described physics educational cultures. Since cultural bordercrossings do occur between the described educational cultures, the problems associated with border-crossings also exist. The problems which are associated with border-crossings are: that pupils and teachers don’t recognize each other’s physics educational cultures. These bordercrossings are described in light of both the teachers’ points of view and the pupils’ points of view.

Manifestation visible des cross-overs génétiques, les chiasmata lient les paires de chromosomes homologues afin de les orienter correctement sur le fuseau méiotique en Métaphase et Anaphase I. Ils résultent d'un processus complexe et étroitement régulé impliquant l'induction de cassures double-brins et de leur réparation par l'invasion d'un duplex d'ADN homologue faisant office de modèle. La recombinaison est ainsi essentielle pour le synapsis et la ségrégation correcte des chromosomes méiotiques à la première division méiotique, et pour la génération de la variabilité génétique. Bien que les processus permettant à un chromosome de s'apparier seulement à son homologue ne soient pas complètement élucidés, l'appariement des chromosomes homologues est étroitement lié à la recombinaison catalysée par les enzymes d'échange de brins d'ADN RAD51 et DMC1. Ces deux protéines ont des capacités très similaires in vitro, mais sont fonctionnellement distinctes in vivo.La première partie de ma thèse montre l'impact de l'élimination de l'activité d'échange de brins de RAD51 dans la méiose d'Arabidopsis, tout en conservant sa fonction de facteur accessoire pour l'action de DMC1. La recombinaison peut donner lieu à des cross-over (CO) et non-cross-over (NCO) et la recombinase spécifique de la méiose DMC1 a été jugée particulièrement importante dans la production de CO interhomologue. Des résultats récents suggèrent fortement toutefois que DMC1 est la seule recombinase active dans la méiose et doit donc être responsable des résultats de CO et NCO. Etant donné qu'environ 95% de la recombinaison méiotique homologue dans Arabidopsis n'entraîne pas de cross-overs interhomologues, Arabidopsis est un modèle particulièrement sensible pour tester l'importance relative des deux protéines - même des effets mineurs sur la population d'événements non-cross-over devraient produire des effets détectables sur les cross-overs. DMC1 catalyse la réparation de toutes les cassures d'ADN méiotiques en présence d'une protéine RAD51 catalytiquement inactive (fusion RAD51-GFP), et les résultats de mon travail montrent que cela n'a pas d'effet détectable sur les taux relatifs de recombinaison de CO et de NCO : à la fois localement, à l'échelle du chromosome et du génome. Et non plus sur la progression de la division méiotique. Ce travail a abouti à une publication dans le journal PLoS One (Singh G, Da Ines O, Gallego ME & White CI (2017) Analyse de l'impact de l'absence d'activité d'échange de brins de RAD51 dans la méiose d'Arabidopsis PLoS ONE 12: e0183006- 16).Des publications antérieures montrent une synapsis homologue partielle et incomplète en l'absence de rad51 et xrcc3 dans la méiose d'Arabidopsis. Cela s'accompagne de la présence de nombreuses fibres courtes ZYP1 dans ces noyaux, ce qui pourrait indiquer de faibles longueurs de complèxe synaptonémale (SC). Ce synapsis partielle dépend à la fois de SPO11 et de DMC1 et implique des péricentromères, montrant que DMC1 est capable (au moins partiellement) d'entraîner le synapsis dans les péricentromères en l'absence de RAD51. Afin de mieux caractériser ceci et pour tester l'hypothèse que les fibres ZYP1 courtes montrent la présence d'une initiation de SC à ces sites, j'ai méné des expériences d'immunofluorescence et d'imagerie SIM. Utilisant un coloration DAPI et les antiséra ASY1, ZYP1 et CENH3, j'ai conduite des analyses cytogénétiques de le synapsis dans les mutants rad51, xrcc3 et des plantes sauvages. Ces travaux faisaient l'objet de la deuxième partie de mes travaux de thèse. Dans les plantes mutantes, j'observe effectivement des fibres courtes ZYP1 comprenant des centromères, mais elles ne sont pas la règle, ce qui signifie que le synapsis ne commence pas nécessairement à des centromères ou des péricentromères. (...) / The visible manifestation of genetic crossing-over, chiasmata link homologous chromosome pairs to permit them to properly orient on the meiotic Anaphase I spindle. They are the result of an intricate and tightly regulated process involving induction of DNA double- strand breaks and their repair through invasion of a homologous template DNA duplex. Recombination is thus essential for the synapsis and accurate segregation of meiotic chromosomes at the first meiotic division, and in doing so, generates genetic variation. Although the processes permitting a chromosome to pair only with its homologue are not fully understood, successful pairing of homologous chromosomes is tightly linked to recombination catalysed by the DNA strand exchange enzymes RAD51 and DMC1. Both proteins share very similar capabilities in vitro, but are functionally distinct in vivo. The first part of my thesis shows the impact of eliminating the strand exchange activity of RAD51 in Arabidopsis meiosis, while retaining its function as an accessory factor for the action of DMC1. Recombination can give rise to both crossover (CO) and non-crossover (NCO) outcomes and the meiosis-specific recombinase DMC1 has been thought to be of particular importance in the production of inter-homolog CO. Recent results however suggest strongly that that DMC1 is the only active recombinase in wild-type meiosis and thus must be responsible for both CO and NCO outcomes. Approximately 95% of meiotic homologous recombination in Arabidopsis does not result in inter-homologue crossovers and Arabidopsis is thus a particularly sensitive model for testing the relative importance of the two proteins - even minor effects on the non-crossover event population should produce detectable effects on crossing-over. DMC1 catalyses repair of all meiotic DNA breaks in the presence of the catalytically inactive RAD51 (RAD51-GFP fusion) and the results of my work show that this has no detectable effect on the relative rates of CO and NCO recombination, both locally and chromosome- and genome-wide, nor on the progression of the meiotic division. This work has resulted in a publication in the journal PLoS One (Singh G, Da Ines O, Gallego ME & White CI (2017) Analysis of the impact of the absence of RAD51 strand exchange activity in Arabidopsis meiosis. PLoS ONE 12: e0183006–16).Previous publications show partial, incomplete homolog synapsis in the absence of rad51 and xrcc3 in Arabidopsis meiosis. This is accompanied by the presence of many short ZYP1 fibres in these nuclei, possibly indicating short stretches of Synaptonemal Complex (SC). The partial synapsis is both SPO11- and DMC1-dependent and involves peri-centromeres, showing that DMC1 is able to (at least partially) drive synapsis in peri-centromeres in the absence of RAD51. In an effort to better characterize this and to test the hypothesis that the short ZYP1 fibres show the presence of initiation of SC at these sites, immunofluorescence and SIM imaging with DAPI staining and ASY1, ZYP1 and CENH3 antisera were carried out for cytogenetic analyses of synapsis in rad51 and xrcc3 mutants and the WT in the second part of my thesis work. Although I do observe short ZYP1 fibres including centromeres in the mutants, these are not the rule, so synapsis does not necessarily begin at centromeres or peri-centromeres. The superresolution imaging does confirm the presence of stretches of 4-chromatid fibres in xrcc3 plants and this approach will be extended in future work of the group to probe the nature of the RAD51-independent partial meiotic chromosome synapsis.Finally, I have designed and built CRISPR/CAS9 constructs with the aim of creating meiotic DSB hotspots at specific genomic loci. Taking advantage of single nucleotide polymorphism data, these constructs were designed to specifically cleave sites in the Arabidopsis Col-0 ecotype, and not in Ler-0 plants. (...)

La recombinaison méiotique produite par les Crossing Overs (COs) est un facteur limitant pour l’efficacité de la sélection variétale. Une possibilité pour produire des plantes hyper-recombinantes serait d’exploiter la variabilité intraspécifique pour les fréquences de recombinaison. L’identification des polymorphismes causaux, liés à la séquence ou l’expression, représente un travail de longue haleine. Une approche alternative serait de produire des mutants pour des régulateurs négatifs des fréquences de recombinaison. Chez le colza, jeune allotétraploïde (AACC, 2n=38), il est possible de jouer sur ces 2 approches. Dans un premier temps j’ai cherché à vérifier dans quelle mesure pouvait varier le transcriptome méiotique entre 2 variétés ayant servi à cartographier un QTL pour le contrôle de la recombinaison entre chromosome homoéologues (hérités des génomes parentaux). Ce transcriptome méiotique s’est révélé de façon inattendue très variable ; les principales sources de cette variation étant notamment la nature du génome (A ou C) ainsi que l’effet variété. J’ai montré que les HEs (le remplacement d’une région chromosomique par la duplication de la région homoéologue) contribuent de façon importante aux différences d’expression observées à la fois entre variétés ou au sein d’un même génotype. Dans un second temps, j’ai vérifié que FANCM décrit chez Arabidopis thaliana comme un régulateur négatif pour les fréquences de recombinaison avait bien la même fonction chez les Brassica. Chez Brassica rapa j’ai vérifié qu’un mutant fancm complémente comme attendu un mutant déficient pour la voie majoritaire de formation des COs. Chez Brassica napus j’ai observé une faible augmentation à la fois des fréquences de recombinaison entre chromosomes homologues et homoéologues. Ce travail souligne l’importance de la caractérisation des HEs chez les allopolyploïdes. Au-delà de leurs impacts sur le contenu et l’expression génique, les HEs ont très certainement des conséquences phénotypiques. Cette étude présente aussi un exemple de biologie translationnelle pour un trait important en amélioration des plantes. / Meiotic recombination driven by Crossing-Over (CO) is a limiting factor for the efficiency of plant breeding. One way to produce hyper-recombinant plants is to use the existing interspecific variability for recombination frequencies. Identification of the causal polymorphisms, either link to gene sequence or expression, represents a long-term endeavour. Another possibility is to mutate anti-meiotic CO genes. In rapeseed, a young allotetraploid species (AACC, 2n=38), both of these approaches are possible. First I wanted to check how much varies the meiotic transcriptome between 2 varieties that differ in term of recombination between homoeologous chromosomes (inherited from parental genomes). Unexpectedly, the meiotic transcriptome turned out to be very variable, the main source of this variation being notably the origin of the genome (A or C) and the variety. I also showed that homoeologous exchanges (HEs; the replacement of one chromosomal region with a duplicate of the homeologous region) contributed to this variation and led to large changes in expression both between and within varieties. Then I assessed whether FANCM, an anti-CO protein identified in Arabidopis thaliana had the same function in the Brassica genus. In Brassica rapa, a fancm mutant complements as expected a meiosis mutant defective in the main formation pathway for the formation of meiotic COs. In Brassica napus, I observed a slight increase in both homologous and homoeologous recombination frequencies. This work emphasizes the importance of characterizing HEs in allopolyploids species. Beyond their impact on gene content and expression, HEs most have likely phenotypic consequences. This study also presents an example of translational biology for an important trait in crop breeding.

Level crossing times and their applications in finance are of importance, given certain threshold levels that represent the "desirable" or "sell" values of a stock. In this thesis, we make use of Wald's lemmas and various deep results from renewal theory, in the context of finance, in modelling the growth of a portfolio of stocks. Several models are employed .

Automated vehicles (AVs) will be integrated into our society at some point in the future, but when is still up for debate. An extensive amount of research is being completed to understand the communication methods between AVs and other road users sharing the environment to prepare for this future. Currently, researchers are working to understand how different forms of external communication on the AVs will impact vulnerable road user (VRU) interaction. However, within the last 10 years, VRU casualty rates have continued to rise for all classifications of VRUs. Unfortunately, there is no suggestion that pedestrian fatality rates will ever decrease without some intervention. This dissertation aims at understanding the impacts of eHMI across real-world, complex scenarios with AVs and how researchers can apply those future findings to improve VRUs' judgments to today. A series of studies evaluated the necessity and impact of eHMI on AV–VRU interaction, assessed how the visual components of eHMI influenced VRU crossing decisions, and how variations in a real-world environment (multiple vehicles and scenario complexity) impact crossing decision behavior. Two studies examined how eHMI will impact future interactions between AVs and VRUs. Specifically, to understand how to advance the design of these future devices to avoid unintended consequences that may result. Results from these studies found that the presence and condition of eHMI did not influence participants' willingness to cross. Participants primarily relied on the speed and distance of the vehicle to make their crossing decision. It was difficult for participants to focus on the eHMI when multiple vehicles competed for their attention. Participants typically prioritized their focus on the vehicle that was nearest and most detrimental to their crossing path. Additionally, the type of scenario caused participants to make more cautious crossing decisions. However, it did not influence their willingness to cross. The last study applied the learnings from the first two studies to a foundational perception study for current legacy vehicles. These results showed a significant increase in judgment accuracies with a display. Through analysis across overall conclusions from the 3 studies, five critical findings were identified when addressing eHMI and 3 design recommendations, which are discussed in the penultimate section of this work. The results of this dissertation indicate that eHMI improved VRUs' accuracy of perception of change in vehicle speed. eHMI did not significantly impact VRUs crossing decisions. However, the complexity of the traffic scenarios affected the level of caution participants exhibited in their crossing behavior. / Doctor of Philosophy / An extensive amount of research is being completed to understand the communication methods between AVs and other road users sharing the environment to prepare for this future. Currently, researchers are working to understand how different forms of external communication on the AVs will impact vulnerable road user (VRU) interaction. However, within the last 10 years, VRU casualty rates have continued to rise for all classifications of VRUs. Unfortunately, there is no suggestion that pedestrian fatality rates will ever decrease without some intervention. This dissertation aims at understanding the impacts of eHMI across real-world, complex scenarios with AVs and how researchers can apply those future findings to improve VRUs' judgments to today. A series of studies evaluated the necessity and impact of eHMI on AV–VRU interaction, assessed how the visual components of eHMI influenced VRU crossing decisions, and how variations in a real-world environment (multiple vehicles and scenario complexity) impact crossing decision behavior.

We are concerned with the probability that a standard Brownian motion W(t) crosses a curved boundary c(t) on a finite interval [0, T]. Let this probability be denoted by Q(c(t); T). Due to recent advances in research a new way of estimating Q(c(t); T) seems feasible: Monte Carlo Simulation. Wang and Pötzelberger (1997) derived an explicit formula for the boundary crossing probability of piecewise linear functions which has the form of an expectation. Based on this formula we proceed as follows: First we approximate the general boundary c(t) by a piecewise linear function cm(t) on a uniform partition. Then we simulate Brownian sample paths in order to evaluate the expectation in the formula of the authors for cm(t). The bias resulting when estimating Q(c_m(t); T) rather than Q(c(t); T) can be bounded by a formula of Borovkov and Novikov (2005). Here the standard deviation - or the variance respectively - is the main limiting factor when increasing the accuracy. The main goal of this dissertation is to find and evaluate variance reducing techniques in order to enhance the quality of the Monte Carlo estimator for Q(c(t); T). Among the techniques we discuss are: Antithetic Sampling, Stratified Sampling, Importance Sampling, Control Variates, Transforming the original problem. We analyze each of these techniques thoroughly from a theoretical point of view. Further, we test each technique empirically through simulation experiments on several carefully chosen boundaries. In order to asses our results we set them in relation to a previously established benchmark. As a result of this dissertation we derive some very potent techniques that yield a substantial improvement in terms of accuracy. Further, we provide a detailed record of our simulation experiments. (author's abstract)

As a pedestrian at the roadside, the two most informative cues as to the distance and rate of closure of a vehicle are its optical size and the rate of expansion of the optical image. In addition, the time to arrival of an approaching vehicle can be perceptually estimated by the ratio of these two variables, referred to as tau (Lee, 1976). Sensitivity to optic expansion is critical for collision avoidance and was measured in populations of adults, typically developing children, and in children with Developmental Coordination Disorder (DCD), an idiopathic condition characterised by marked impairments in motor coordination that negatively impact on activities of daily living. A central tendency was found in adults (n = 193) between 18 to 59 years of age to make significant errors in judging the approach rates of two vehicles. Inflated errors were observed in children (n = 136) between 6 to 17 years of age, with decreased sensitivity in the youngest age group (6 to 11 years). Furthermore, a significant decrement was found in children (n = 9) with DCD between 6 to 11 years of age. Across all groups, a systematic vehicle size bias was found, whereby faster small vehicles were perceived as travelling slower than larger vehicles. This pattern of results suggest that in general, observers are not utilising tau in judgments of relative approach rates for speeds typically encountered at the roadside, but instead rely on optical expansion that does not compensate for image size. Errors due to a reliance on optic size were inflated in children with DCD, potentially placing them at significantly greater risk at the roadside. To examine the decreased sensitivity observed in DCD, thresholds for detecting visual looming were measured in children (n = 11) with DCD between 6 to 11 years of age. A significant deficit was found when vehicles were presented in perifoveal vision, whereby children with DCD may perceive vehicles that are 5 seconds away as stationary if they are travelling any faster than ~14 mph. This demonstration of a low-level visual processing deficit could suggest an immaturity in the dorsal stream network and explain some of the difficulties that characterise DCD. Critically, perceptual judgments at the roadside are inextricably linked to the motoric capability of the observer. If a pedestrians crossing time is greater than the time available, collision will occur. Crossing gap thresholds were measured and compared to walking times for a single vehicle approaching at varying speeds. Children (n = 9) with DCD between 6 to 11 years of age left considerably longer temporal crossing gaps than their action capabilities necessitated. However, when children with DCD were presented with multiple vehicles in a virtual reality environment, they accepted crossing gaps at all approach speeds that were shorter than the time it would take them to cross. This suggests that children with DCD may not have the perceptual accuracy to predict their required action gaps in a road crossing situation. One explanation for these findings could be a difference in DCD in how vision is dynamically allocated to facilitate the preparation of goal-directed actions. Dynamic allocation of visual attention was assessed in a series of experiments that measured eye movement latencies and hand movement accuracy in children (n = 5) with DCD between 6 to 11 years of age. Both measures were found to be comparable in DCD with their typically developing peers regardless of task complexity, indicating that the allocation of visual attention is not deficient in children with DCD. The prospective control of movement in our everyday lives is critically depended on estimating the immediacy of approaching objects. Combined, these results indicate that children with DCD may be particularly vulnerable at the roadside due to a visual motion processing deficit, consistent with atypical function across broad neural structures such as the dorsal stream.

Each of us has knowledge but it is not complete. When we come together to listen, we learn, we grow in understanding and we can analyze better the course that needs to be taken. One thing I learned over the past several years is that words and their interpretation have power. Grand Bayou community member This dissertation examines the question of change in the non-community people who have interacted or come into contact with the Grand Bayou Participatory Action Research (PAR) project. Who Changes?, a book on institutionalizing participation in development, raises the issu of "where is the change?" in a participatory project (Blackburn1998). Fischer (2000), Forester (1992), and Wildavsky (1979) indicate that a participatory process is beneficial to all stages of planning policy development, and analysis. However, planners, academics, and practitioners who work with high risk communities are often of different cultures, values, and lived experience than those of the community. Despite the best intentions of these professionals, these differences may at times cause a disconnect from or a dismissal of the community's knowledge, values or validity claims as the participatory process transpires. The outside experts often fail to learn from the local communities or use the community's expertise. The Grand Bayou Participatory Action Research (PAR) project, funded in part by a National Science Foundation (NSF) grant, investigated the viability of PAR in a post-disaster recovery project. The NSF report revealed that the community did gain agency and political effectiveness; the study and evaluation, however, did not focus on the outside collaborators and their change. Freirian and Habermasian theories of conscientization and critical hermeneutics would assume that those engaged with the project have changed in some way through their learning experience and that change may be emancipatory. The change builds on a core tenet of PAR in developing relational knowledge while honoring the other. This study used a case study methodology utilizing multiple sources of evidence to explore the answer to this question. A better understanding of the change in outside collaborators in a PAR project can be helpful in developing a more holistic participatory community planning process.