Dans le cadre des recherches présentées ici, nous avons tout d'abord étudié les limitations de la fixation d'azote non-symbiotique en nutriments dans les milieux tempérés froids. Des études similaires en milieux tropicaux ont démontré que la fixation d'azote pouvait y être limitée par la présence des nutriments Mo et P. Pour l'étude présentée ici, les milieux tempérés froids ont été divisés en deux catégories, les milieux à couvert végétal majoritairement feuillu et majoritairement résineux. Les résultats ont permis de démontrer que la fixation d'azote et les limitations en nutriments étaient dépendantes du couvert végétal. Nous avons ensuite étudié l'évolution de la limitation de la fixation d'azote au cours d'une saison. En effet, plusieurs études à long-terme (plusieurs saisons) avaient démontré des variations des taux de fixation d'azote, mais peu d'études se concentraient sur l'évolution saisonnière. Les résultats ont démontre qu'une évolution saisonnière était bien présente et qu'elle devait être prise en compte lors de comparaisons entre différentes études, surtout pour les milieux tempérés froids où les saisons sont grandement différentes les unes des autres. Ensuite, nous avons fait l'étude des facteurs influençant la fixation d'azote à court-terme (quelques heures à quelques jours). Plusieurs études avaient déjà démontré que la fixation d'azote était influencée par une modification de paramètres abiotiques. La dynamique de ces variations de taux de fixation d'azote était mal connue. Celle-ci a pu être évaluée grâce à une nouvelle méthode plus sensible de mesure de taux de fixation d'azote en continu, ARACAS. Nous avons montré que la fixation d'azote répondait rapidement à des changements de paramètre abiotiques et qu'il est maintenant possible d'observer ces changements rapides grâce à la méthode d'ARACAS. De plus, nous avons été en mesure d'identifier, grâce à cette méthode plus sensible, une association mousse-cyanobactéries entre Anomodon attenuatus et les cyanobactéries Calothrix sp. et Nostoc sp. , association jusqu'alors inconnue. Des études connexes ont aussi permis de démontrer tout le potentiel de l'étude des fixateurs non-symbiotiques. Ainsi, nous avons démontré qu'il serait possible, grâce à des études futures, de voir de quelle façon la fixation d'azote non-symbiotique des associations mousses-cyanobactéries est limitée. II serait aussi possible d'étudier la fixation non-symbiotique dans un contexte de réchauffement climatique et d'augmentation de la quantité de CO 2 dans l'atmosphère. De plus, les résultats de l'étude du relargage des nutriments au cours d'une saison et en fonction du couvert végétal permettront aussi de comprendre de quelle façon fonctionnent les nitrogénases et comment l'apport en nutriments varie au cours d'une saison. Finalement, l'ensemble des résultats obtenus démontrent que la fixation d'azote non-symbiotique est bien mal évaluée. À cause de leur aire de distribution élevée, les fixateurs d'azote non-symbiotiques pourraient avoir un apport en azote au cycle global beaucoup plus élevé que celui actuellement estimé. Une nouvelle estimation tenant compte des nouveaux et futurs développements pourrait permettre de raffiner les estimations du cycle de l'azote et du budget d'azote global.[symboles non conformes]

Objectives: To verify the necessity for special surgical techniques or clips for fixation of the electrode cable of a cochlea implant against dislocation, and to test the stability of postoperative biologic cicatrization as the sole and solid anchoring of the cable. Material: Temporal bone experiments with a simulated connective tissue sheath around conventional (Med El Combi 40+) and prototype (profiled surface) electrode cables. Results and Conclusions: The electrode cable is anchored securely in a sheath of scar tissue, since unphysiologic loads are needed for pulling it out of its anchorage. The drag during one extraction trial with a profiled cable even resulted in the rupture of the cable. These results confirm our confidence in this biologic fixation of the electrode cable inside its postoperative cicatric tissue sheath. More than 80 cochlea implantations with the electrode simply imbedded in a drop of fibrin glue in the posterior tympanotomy never demonstrated a shift of the electrodes in the last 8 years. Therefore, special fixation of the electrode cable with clips or surgical techniques is not necessary. / Fragestellung: Muss das Elektrodenkabel eines Kochlearimplantats durch spezielle operative Techniken oder Halterungen gegen ein Herausrutschen aus der Kochlea gesichert werden, oder genügt die Einscheidung in dem postoperativ sich ausbildenden Narbengewebe für eine ausreichend stabile Fixierung? Material: Felsenbeinexperimente mit einer Simulation der narbigen Einbettung konventioneller und modifizierter (geriffelter Oberfläche) Elektrodenkabel eines Kochlearimplantats (Med El Combi 40+). Ergebnisse und Schlussfolgerungen: Ein Herausziehen eines in simuliertem Narbengewebe eingescheideten Elektrodenkabels gelang erst bei erheblichen, unphysiologischen Kräften; eine Rifflung der Oberfläche des Silikonkabels erhöhte den Reibungswiderstand über die Reissfestigkeit des Kabels. Das Vertrauen in die biologische Fixierung des Elektrodenkabels durch die Verankerung im Narbengewebe ist somit gerechtfertigt, und wird auch durch unsere klinische Erfahrung bestätigt: in über 80 Operationen, bei denen das Kabel des Kochlearimplantats nur durch Einbettung in Fibrinkleber am Rahmen der posterioren Tympanotomie gesichert worden war, liess sich in den letzten 8 Jahren in keinem Fall eine Elektrodenverlagerung nachweisen. Eine gezielte Fixation des Elektrodenkabels durch künstliche Halterungen oder spezielle OP-Techniken erscheint somit nicht erforderlich. / Problématique: Afin d’éviter tout glissement de l’électrode de l’implant cochléaire, est-il préférable d’en assurer la fixation par une technique opératoire particulière ou bien est-il suffisant de gainer l’électrode dans les tissus cicatriciels qui se forment après l’opération? Méthode: Nous avons procédé à des expériences sur le rocher en simulant une inclusion cicatricielle d’un câble-électrode classique (Med El Combi 40+), d’une part, et modifié (surface cannelée), d’autre part. Résultats et conclusion: Une force dépassant les réalités physiologiques a été nécessaire pour retirer le câble-électrode gainé dans les tissus cicatriciels simulés. Le câble avec la surface cannelée s’avérait encore plus résistant: il déchirait même lorsqu’on a essayé de le retirer. Ceci vient donc conforter la confiance que nous avons dans la fixation biologique, c’est-à-dire dans l’ancrage de l’électrode dans les tissus cicatriciels. Une confiance qui est d’ailleurs confirmée par les expériences que nous avons pu faire dans notre clinique. Ainsi, en 8 ans, sur 80 opérations, au cours desquelles le câble de l’implant a été fixé en étant simplement placé dans de la fibrine, dans le cadre d’une tympanotomie postérieure, aucun déplacement de l’électrode n’a été constaté. Par conséquent, il ne s’avère pas nécessaire d’avoir recours à une fixation artificielle ou à une technique opératoire particulière pour assurer le bon maintien de l’électrode / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Various researchers have found that visual problems can contribute to clumsiness in children with DCD. One cause of motor development shortfalls that contribute to a DCD classification seems to be weak eye muscle functions. The visual system as well as well-developed eye muscle functions, play an important role in die development of balance, spatial orientation, body awareness and coordination (hand-eye, foot-eye, hand-foot-eye coordination). It also emerges from the literature that children with DCD do not usually outgrow their problems, although controversy still surrounds this aspect. The aim of this study was twofold. The first aim was to determine, as established by eye muscle functions, what the nature and scope of visual problems are, that is associated with DCD in 7 and 8 year-old children in Potchefstroom. The second aim was to determine whether 7 and 8 year-old Potchefstroom children will outgrow their DCD status without any motor intervention, and what the relationship between vision and the lasting effects of DCD status is. Thirty-two children (20 boys and 12 girls) with an average age of 95.66 months engaged in the study. During a follow-up study after a year of baseline testing at 83.33 months, the researcher wanted to determine whether the subjects diagnosed with DCD had possibly outgrown their DCD status. The Movement Assessment Battery for Children (MABC) (Henderson & Sugden, 1992) was applied for this purpose. The Sensory Input Screening Test (Pyfer, 1987), and the "Quick Neurological Screening Test" (QNST) (Mutti et al., 1998) test batteries were employed to determine the visual status of the children. The "Statistica for Windows 2008" computer software was used to analyse the data. Correlation coefficients as well as two-way variance tables were used for objective one to analyse the relationship between DCD and vision. The results confirmed correlations between DCD and eye muscle functions. Relationships were found between different eye muscle functions (fixation, visual pursuit, left and right eye, ocular alignment right eye) and the MABC total. Significant correlations, with small practical significance (p 10.2) was found between fine motor skills and fixation with both eyes, and with the left eye separately, visual pursuit with the right eye, as well as ocular alignment with the right eye, while a correlation with moderate practical significance (p 10.5) was found with fixtion with the right eye. All six eye muscle functions showed significant correlations with small practical significance (p 10.2) with ball skills. Static and dynamic balance also showed significant correlations with small practical significance (p 10.2) with fixation with both eyes, the left and right eye separately as well as with ocular alignment with the right eye. The results further indicated that in most cases where children have been diagnosed with serious DCD, they were classified in Class 3 (where more than three visual deviations occurred in the subject) regarding their vision. These percentages varied from 36.67% to 83.33%, with the highest percentage problems found in visual pursuit with the right eye. For objective 2, a dependent t-test was employed to determine the state of the children's DCD after a year has lapsed since diagnosis. The differences between the testing showed that most of the children have not outgrown their DCD status, but that the motor performance of a majority of the children has deteriorated over a period of one year (p 10.00). Furthermore, the percentage visual problems in the group with sustained DCD ranged from 71,87% - 100% (visual pursuit, fixation and ocular alignment), with the most visual problems found in fixation and visual pursuit skills. It can be concluded from the results that a significant relationship exists between DCD and a variety of visual functions, as determined by the different eye muscle functions. This evidence also indicated that most children will not outgrow their DCD status without any motor intervention programme. Intervention of children who are diagnosed with DCD should therefor include visual therapy. / Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2009.

Various researchers have found that visual problems can contribute to clumsiness in children with DCD. One cause of motor development shortfalls that contribute to a DCD classification seems to be weak eye muscle functions. The visual system as well as well-developed eye muscle functions, play an important role in die development of balance, spatial orientation, body awareness and coordination (hand-eye, foot-eye, hand-foot-eye coordination). It also emerges from the literature that children with DCD do not usually outgrow their problems, although controversy still surrounds this aspect. The aim of this study was twofold. The first aim was to determine, as established by eye muscle functions, what the nature and scope of visual problems are, that is associated with DCD in 7 and 8 year-old children in Potchefstroom. The second aim was to determine whether 7 and 8 year-old Potchefstroom children will outgrow their DCD status without any motor intervention, and what the relationship between vision and the lasting effects of DCD status is. Thirty-two children (20 boys and 12 girls) with an average age of 95.66 months engaged in the study. During a follow-up study after a year of baseline testing at 83.33 months, the researcher wanted to determine whether the subjects diagnosed with DCD had possibly outgrown their DCD status. The Movement Assessment Battery for Children (MABC) (Henderson & Sugden, 1992) was applied for this purpose. The Sensory Input Screening Test (Pyfer, 1987), and the "Quick Neurological Screening Test" (QNST) (Mutti et al., 1998) test batteries were employed to determine the visual status of the children. The "Statistica for Windows 2008" computer software was used to analyse the data. Correlation coefficients as well as two-way variance tables were used for objective one to analyse the relationship between DCD and vision. The results confirmed correlations between DCD and eye muscle functions. Relationships were found between different eye muscle functions (fixation, visual pursuit, left and right eye, ocular alignment right eye) and the MABC total. Significant correlations, with small practical significance (p 10.2) was found between fine motor skills and fixation with both eyes, and with the left eye separately, visual pursuit with the right eye, as well as ocular alignment with the right eye, while a correlation with moderate practical significance (p 10.5) was found with fixtion with the right eye. All six eye muscle functions showed significant correlations with small practical significance (p 10.2) with ball skills. Static and dynamic balance also showed significant correlations with small practical significance (p 10.2) with fixation with both eyes, the left and right eye separately as well as with ocular alignment with the right eye. The results further indicated that in most cases where children have been diagnosed with serious DCD, they were classified in Class 3 (where more than three visual deviations occurred in the subject) regarding their vision. These percentages varied from 36.67% to 83.33%, with the highest percentage problems found in visual pursuit with the right eye. For objective 2, a dependent t-test was employed to determine the state of the children's DCD after a year has lapsed since diagnosis. The differences between the testing showed that most of the children have not outgrown their DCD status, but that the motor performance of a majority of the children has deteriorated over a period of one year (p 10.00). Furthermore, the percentage visual problems in the group with sustained DCD ranged from 71,87% - 100% (visual pursuit, fixation and ocular alignment), with the most visual problems found in fixation and visual pursuit skills. It can be concluded from the results that a significant relationship exists between DCD and a variety of visual functions, as determined by the different eye muscle functions. This evidence also indicated that most children will not outgrow their DCD status without any motor intervention programme. Intervention of children who are diagnosed with DCD should therefor include visual therapy. / Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2009.

No description available.

eSeeTrack, an eye-tracking visualization, facilitates exploration and comparison of sequential gaze orderings in a static or a dynamic scene. It extends current eyetracking data visualizations by extracting patterns of sequential gaze orderings, displaying these patterns in a way that does not depend on the number of fixations on a scene, and enabling users to compare patterns from two or more sets of eye-gaze data. Extracting such patterns was difficult, if not impossible, with previous visualization techniques. eSeeTrack combines a timeline and a tree-structured visual representation to embody three aspects of eye-tracking data that users are interested in: duration, frequency and orderings of fixations. eSeeTrack allows ordering of fixations to be rapidly queried, explored and compared. Two case studies on surgical simulation and retail store chain to assert the capabilities of eSeeTrack are discussed in this thesis. Furthermore, eSeeTrack provides an effective and efficient mechanism to determine the pattern outliers. This approach can be effective for behavior analysis in a variety of domains that are also described.

Maximum wheat (Triticum aestivum L.) yields in Zambia were obtained with weekly irrigation at 85% of class A pan evaporation during the whole irrigation interval and split application of urea N of which the initial portion of the fertilizer was either broadcast and incorporated or broadcast after the crop had established itself. This corresponded with maximum utilization of fertilizer N. The proportion of N derived from fertilizer was independent of fertilizer placement at various water regimes and N utilization was primarily a function of water availability. / Two nonnodulating soybean (Glycine max L.) cultivars, Clark RJ1 and N77, or in their absence Pearl millet (Panicum glaucum L.) were judged to be appropriate reference crops for estimating N$ sb2$ fixation by soybeans using $ sp{15}{ rm N}$ isotope dilution techniques. A local soybean cultivar, Magoye, was rated highest among three cultivars tested for its ability to support N$ sb2$ fixation by Bradyrhizobium japonicum and contributed biologically fixed N$ sb2$ to a subsequent wheat crop.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 48-53). / viii, 53 leaves, bound ill. (some col.) 29 cm

Typescript / Bibliography: leaves [137]-[157] / xx, 136 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy, Waite Agricultural Research Institute, 1987

Coral reefs are experiencing increasing levels of stress due to climate change, overfishing, coastal development and nutrient runoff from agriculture to name a few. They are however, economically vital ecosystems in terms of both their income generating capacity and as a source of food for millions of people around the world. This predicament emphasises the need for effective ecosystem management to be able to balance the benefits of coral reefs with the inherent stressors associated with people utilising their resources. It is particularly important given the potential large scale impacts associated with climate change such as mass coral bleaching events. Similarly, much of the need for direct management of coral reefs exists in developing countries where the resources, information, and technology are limited or unavailable for such a task. This places them, in particular, at the high end of management uncertainty and impact vulnerability. Accordingly, there is a pronounced need to improve this capacity to understand coral reef ecosystem function and to use this to better predict the overall systems level outcome of management options. This thesis has sought to improve our understanding of key ecological elements of coral reef ecosystems and to build on this new knowledge to produce a widely applicable ecosystem model that will allow managers to better understand and predict the outcomes of their actions. Coral reef ecosystem behaviour is far from understood in its entirety and there are many facets that require detailed further investigations to be able to more confidently predict ecosystem response to any given disturbance. To enhance the current understanding of coral reef ecosystems prior to the model development, investigations were undertaken into the dynamics of nitrogen on a coral reef following bleaching induced coral mortality. The results showed that the rates of nitrogen fixation on surfaces made available due to a coral mortality event increased dramatically in the three months following coral mortality, potentially acting as a driving force for the ecosystem to pass through a phase shift to algal dominance. Application of these nitrogen dynamics to entire coral reef ecosystems required a methodology for scaling these sub coral colony processes to entire reefs. This scaling issue is particularly pertinent given the improved understanding of the overwhelming significance of micro-scale processes to community dynamics. The surface index (SI) concept, relating the two-dimensional projected area to the three-dimensional area of corals was refined and developed for variations of gross coral morphologies. This allowed for the scaling of nitrogen flux estimates to be made over entire reef systems, enabling the incorporation of these fluxes into an ecosystem scale model. One of the key factors associated with the potential for a coral reef to recover from a mass coral mortality event is the potential for new corals to successfully recruit. The process of coral recovery could potentially be enhanced if recruitment is viable in the immediate aftermath of a mortality event. Although investigations in this area were inconclusive, extensive herbivore action on turf assemblages up to eight months old indicated that recruitment may be inhibited through the high palatability of turf assemblages in this age bracket. Integrating these processes with the many other published dynamics of coral reefs allowed for the development of the dynamic systems model. By constraining the model structure to known relationships between the modelling parameters, the model can be calibrated to replicate the dynamics of any coral reef ecosystem. This allows the model to be applied to systems where limited data and/or resources are available, making it widely implementable in developing countries such as the small island states scattered around the tropics. The model is ideally suited to the adaptive management framework whereby managers can continually assess the potential future outcomes of management interventions. In addition, due to the spatially inexplicit and generic nature of the model, it can be easily adapted and integrated into large scale regional modelling frameworks or combined with other modelling packages such as socio-economic or fisheries models to provide enhanced management packages. The culmination of the targeted research and integration of existing knowledge has allowed for the development of an ecosystem model for coral reefs that can be easily adopted by coral reef managers throughout the world. It is however, by no means a definitive coral reef ecosystem model and there are many facets that can and should continue to be refined to enhance the reliability of the model.