Дисертації: "Spatio-temporal control"

1

Rodríguez, Herreros Borja. "Spatio-temporal aspects in the control of the visuomotor system." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/276156.

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The complex voluntary motor behavior of higher primates is often regarded as a consequence of the development of sophisticated and adaptive perceptual and motor systems. Theoretical and behavioral investigations suggest that the control of motor acts involves a sequence of neural operations that select, plan and execute a movement. The visuomotor system integrates visual and proprioceptive signals to exert control on visually-guided actions, which generally allows to efficient localization of the stimuli and generation of the appropriate motor commands. Although the last two decades have witnessed a considerable progress on the understanding of the neural basis of visuomotor control, the shortage of the literature assessing directly this process boost the necessity of developing new spatio-temporal frameworks of how this process might work. The present dissertation is focused on providing strong insights about the neural and behavioral aspects subserving the use of spatio-temporal information through vision and proprioception to accomplish accurate goal-directed actions. This dissertation encloses five different studies to shed some light on these issues, by combining neuroimaging and psychophysical tools. These empirical data are presented in Chapters 3 to 7, in the form of five articles. Two studies (Chapters 3 and 4) addressed object localization in reaching, by investigating the neural and behavioral mechanisms by which the integration of visual motion affects the execution of hand movements. We demonstrate that visual illusory percepts affect the hand trajectory toward a misperceived object, in a form that casts some doubts on the suitability of feedback circuits to sustain early motion-position interaction. Two other independent studies (Chapter 5 and 6) focused on the coding of hand location, by examining how the use of proprioception and the felt position of the arm influenced our temporal and spatial accuracy in interception. We uncover an increase in the weighting of proprioceptive signals when intercepting objects under poor visual conditions. In addition, the study of Chapter 6 reveals that proprioceptive cues of the hand location completely adapted to induced displacements of the visual input of the hand. The last study (Chapter 7) dealt with the online monitoring of a reaching movement. We have indentified a causal structure/function relationship between deficits in online motor control and the induction of inhibitory plastic changes over the medial intraparietal sulcus, suggesting this area as the neural locus in charge of the ability to update a motor command. We have found anatomical differences in white matter parietofrontal pathways responsible for the individual differences in the impairment of the online motor control. Taken together, the research presented here strengthens the idea that our visuomotor system acts as a coordinated system that efficiently encodes relevant spatial and temporal features at different neural levels to ascertain a precise reaching behavior. Moreover, the combination of the sensory inputs that provide this information seems to depend on the reliability of the sensory source. I hope the work presented here will encourage the reader to explore deeper in the many aspects of this part of the brain still unrevealed.
El complejo comportamiento motor voluntario de los primates superiores a menudo se considera como una consecuencia del desarrollo de complejos y adaptativos sistemas perceptuales y motores. Estudios teóricos y conductuales sugieren que el control de los actos motores implica una secuencia de operaciones neuronales que seleccionan, planifican y ejecutan un movimiento. El sistema visomotor integra señales visuales y propioceptivas para ejercer control sobre las acciones guiadas visualmente, permitiendo la localización eficiente de los estímulos y la generación de las órdenes motoras apropiadas. Aunque las dos últimas décadas fueron testigo de un progreso considerable en la comprensión de las bases neuronales del control visomotor, la escasez de bibliografía abordando directamente este proceso impulsa la necesidad de desarrollar nuevos marcos espacio-temporales de cómo podría funcionar el control visomotor. Esta tesis se centra en proporcionar conocimientos robustos sobre los aspectos neurales y conductuales que promueven el uso de información espacio-temporal a través de la visión y la propiocepción, con el fin de realizar certeras acciones dirigidas a objetos. Esta tesis encierra cinco estudios diferentes para arrojar luz sobre estas cuestiones, mediante la combinación de psicofísica y técnicas de neuroimagen. Los datos empíricos se presentan en los capítulos 3 a 7, en forma de cinco artículos. Dos estudios (Capítulos 3 y 4) abordan la localización de objetos en acciones para alcanzarlos, mediante la investigación de los mecanismos neurales y conductuales por los que la integración de movimiento visual afecta la ejecución de movimientos manuales. Demostramos que las percepciones ilusorias visuales afectan la trayectoria de la mano hacia un objeto erróneamente percibido, y también cuestionan la idoneidad de los circuitos ‘feedback’ para explicar la temprana interacción movimiento-posición. Otros dos estudios independientes (Capítulos 5 y 6) se centran en la codificación de la posición de la mano, mediante el examen de como el uso de la propiocepción y la posición sentida del brazo influenciaron nuestra precisión temporal y espacial interceptando un objeto. Descubrimos un aumento en la ponderación de las señales propioceptivas al interceptar objetos bajo pobres condiciones visuales. Además, el estudio del Capítulo 6 revela que las señales propioceptivas de la ubicación de la mano se adaptaron completamente a desplazamientos inducidos de la información visual de la misma. El último estudio (Capítulo 7) se ocupó de la monitorización ‘online’ de un movimiento, mediante la identificación de una relación causal estructura/función entre los déficits en el control motor y la inhibición del surco intraparietal medial, lo que sugiere este área como la zona responsable de la capacidad de actualizar un comando motor. También identificamos diferencias anatómicas en los tractos parietofrontales de materia blanca causantes de las diferencias individuales en el deterioro del control motor. En conjunto, la investigación presentada aquí refuerza la idea de que nuestro sistema visomotor actúa como un sistema coordinado que codifica de manera eficiente las características espaciales y temporales correspondientes a diferentes niveles neuronales para conseguir un preciso comportamiento motor. Además, la combinación de las vías sensoriales que proporcionan esta información parece depender de la fiabilidad de la fuente sensorial. Espero que el trabajo aquí presentado anime al lector a explorar más profundamente en los diversos aspectos de esta parte del cerebro todavía no revelados.

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2

Gaciu, Nicoleta. "Control of spatio-temporal dynamics of bio and optoelectronics systems." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843627/.

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Bio and optoelectronics systems are different systems in their composition and application but they have surprising similarities in terms of their spatio-temporal dynamics and dynamics control. Both systems are complex systems with many degrees of freedom that are spatially structured on micro and nano scales. Their behaviour can easily switch between stable regime to chaos by changing internal and external influencing factors. Historically, optoelectronics systems have been studied for more than 30 years. Due to novel biotechnological applications bio systems have more recently gained importance. Today, many natural and technological systems are composed of mesoscopic bio and optoelectronic devices or elements. In nature, many biological and chemical processes controlling the functioning of a system or a specific process (e.g. photosynthesis) occur in complex cellular and molecular ensembles. In technological systems, improvements in the development and design of novel materials on an atomic level have opened the way to efficient devices suitable for mass production. This work focuses on the control and analysis of two mesoscopic model examples: molecular motors and semiconductor lasers. In recent years they have been of particular importance due to their complex dynamics. These active systems have many features in common. Both are open systems which use an energy source to generate motion or light. Molecular motors are nanometer-scaled functional biomolecular structures that convert chemical energy into directed motion. Semiconductor lasers convert an electrical pump current into coherent light emission. Due to underlying complex interaction processes both systems show instabilities under the influence of parameters. In a molecular motor ensemble, external forces, diffusion of free and bound motors, and geometrical arrangement of the microtubule substrate tend to bring instabilities into the molecular motor system. In semiconductor lasers, the interplay of carrier diffusion, light diffraction and geometrical constraints given by the width of the laser (typically in the ?m regime) lead to complex interplay of longitudinal and transverse modes and to instabilities and chaos. The aim of this work is to fundamentally analyse the mechanism relevant for the complex dynamics of the two active systems and to derive schemes to control them. For this purpose I have performed complex numerical simulations. The theoretical description of the molecular motor systems is based on Fokker-Planck equations. Space-time simulations of the dynamics of molecular motors reveal the influence of the diffusion constant, arrangement of filaments, number and separation between filaments and external forces on the spatio-temporal dynamics of molecular ensemble. The theoretical analysis of semiconductor lasers is done on the basis of multi-mode Maxwell-Bloch equations. Simulations of the spatio-temporal dynamics in this system demonstrate that the application of a delayed optical feedback realised by a suitable external resonator configuration can lead to an efficient emission control. Various feedback configurations are discussed. The thesis is organised as follows. Chapter 1 gives a general introduction to molecular motors and semiconductor lasers. Chapter 2 focuses on molecular motors. This includes a review of theoretical models, molecular motor properties and simulation results on the complex spatio-temporal dynamics of molecular motor complexes. In Chapter 3 of this thesis, broad area semiconductor lasers with delayed optical feedback will be investigated. The analysis will concentrate on laser systems with unstructured and structured delayed optical feedback. Concluding remarks and future work are given in Chapter 4.

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3

Romero, Catalina. "Spatio-temporal control of the cytosolic redox environment in C. elegans." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11122.

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Compartmentalization of redox reactions is essential to all life forms. Protein activity can respond to changes in the local redox environment through the reversible oxidation of cysteine thiols. For the majority of cysteines in the proteome, this interaction takes place through equilibration with the glutathione pool; this raises the question whether this redox pool acts as a buffer, or instead as a sensitive media, transducing information from a local physiological state into protein function.

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4

Pisano, Filippo. "Advanced technologies for spatio-temporal control of neural circuits using optogenetics." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27899.

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The progress of neuroscientific research is linked to the development of technologies able to interface with the complexity of neural circuitry. Remarkable advances in this direction have been achieved in the past decades and it is now possible to optically control the neural activity of genetically targeted cells with techniques known as optogenetic stimulation. The combination of optogenetic stimulation methods with electrophysiological recordings and advanced optical imaging is leading to promising approaches aiming at obtaining information on spiking activity, morphology and genetic identity of the many constituents of neural networks. This PhD research project focussed on the development of an experimental tool to exploit this possibility combining micro-electrode array (MEA) electrophysiological recordings with a custom two-photon microscope and optogenetic stimulation system based on a Î¼LED array. This thesis reports on the construction, validation and application of this tool, that was employed in retinal recordings to link the precisely-timed spike signals detected by the MEA with the anatomical and genetic identity of the spiking neurons. The combination of large-scale MEA recordings with spatio-temporal Î¼LED optogenetic stimulation led to a novel method to link anatomy to functional and genetic identity in genetically-targeted retinal ganglion cells (RGCs) with a large scale approach. This method is a versatile approach that can be applied to characterise the many molecular types of RGCs. The integration of two-photon imaging and MEA recordings proved to be more arduous, yet applicable. Retinal ganglion cells were imaged in two-photon mode while mounted on the MEA and electrophysiological identification of spiking units was demonstrated notwithstanding large laser-induced artifacts. Optimisation of the system will allow to fully exploit the advantages offered by non-linear excitation.

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5

Schneider, Isabelle Anne Nicole [Verfasser]. "Spatio-temporal feedback control of partial differential equations / Isabelle Anne Nicole Schneider." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1122111118/34.

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6

Hockham, Natalie. "Spatio-temporal control of acoustic cavitation during high-intensity focused ultrasound therapy." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:1dd3c105-6b6e-49e0-a948-0fa7c07fc642.

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High-intensity focused ultrasound (HIFU) is rapidly emerging as a viable alterna- tive to conventional therapies in the treatment of deep-seated, solid tumours. In contrast to surgical methods, extracorporeal HIFU transducers non-invasively tar- get pathogenic tissue deep beneath the skin, inducing thermal necrosis of a volume of tissue typically coincident with the ultrasound focus. More recently, cavitation activity has been observed to enhance focal heating, whilst providing a unique op- portunity for real-time treatment monitoring. Unfortunately, the stochastic nature of cavitation makes it difficult to initiate and sustain the level of cavitation activity required for enhanced heating, and to confine the spatial extent of cavitation to the focal volume. The overall aim of this thesis is to design and implement a real-time, closed- loop controller for sustaining thermally relevant cavitation within the HIFU focal region. This is intended to improve the speed and reproducibility of tissue ablation, whilst providing clinicians with real-time feedback as to the extent and location of the ablated region. A quantitative relationship between the level of cavitation activity and asso- ciated temperature rise is first sought experimentally, by investigating cavitation- enhanced heating in two different tissue-mimicking materials (TMM) that yield dif- ferent levels of cavitation for the same HIFU exposure conditions. It is found that a minimum level of inertial cavitation activity is required for cavitation-enhanced heating to dominate the heating process, which is achieved in the first material but not the second. However, the introduction of exogenous, artificial nuclei to the second material is seen to augment cavitation levels to the extent that cavitation- enhanced heating becomes dominant. Subsequently, HIFU experimentation is extended to non-perfused, ex vivo bovine liver, into which a variety of cavitation nuclei are introduced to augment cav- itation levels, and hence heating. Commercially available lipid-shelled microbub- bles are contrasted with custom-made sonosensitive nanoparticles for their ability to seed cavitation events, culminating in an empirical relationship between iner- tial cavitation and heating that is common to both types of exogenous nuclei, and which agrees with the in vitro results. Moreover, the abnormally large lesions pro- duced are found to correlate with a broad spatial distribution of inertial cavitation events, as seen on two-dimensional passive acoustic maps. Based on these encouraging results, a novel negative-feedback, real-time con- trol system is implemented to sustain inertial cavitation within the focal region for extended periods of time. The controller is designed to be both asymmetric and adaptive, deploying different feedback gains to adjust the peak rarefactional focal pressure (PRFP), depending on whether cavitation activity is above or below the level required for cavitation-enhanced heating. With active cavitation control in vitro, the associated focal temperature elevation is maintained at a cytotoxic level for 20 seconds using less than half the energy input required in the absence of cavi- tation control. In order to test the applicability of the novel controller to a near-physiological environment, HIFU exposures are eventually performed in a unique normothermic perfused liver model that accounts for both heat advection and nuclei replenish- ment. Following preliminary experimentation, the controller is modified to account for the inherent variability in the cavitation threshold of perfused tissue, whilst the cavitation demand is also increased to account for heat advection. Following these modifications, use of the controller is found to enable greatly improved re- producibility of HIFU-induced lesions compared to those achieved without cavita- tion control, with a lesion size that is directly related to the cavitation demand. A cost-effective method for enabling caviation-enhanced, cavitation-controlled and cavitation-monitored HIFU therapy has thus been developed, which enables suc- cessful tissue ablation at acoustic energies lower than in current clinical use.

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7

Mounaix, Mickaël. "Matricial approaches for spatio-temporal control of light in multiple scattering media." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066562/document.

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L’imagerie optique à travers des milieux diffusants, comme des milieux biologiques ou de la peinture blanche, reste un challenge car l’information spatiale portée par la lumière incidente est mélangée par les évènements multiples de diffusion. Toutefois, les modulateurs spatiaux de lumière (SLM) disposent de millions de degrés de liberté pour contrôler le profil spatial de la lumière en sortie du milieu, en forme de tavelure (speckle), avec des techniques de modulation du front d’onde. Cependant, si le laser génère une impulsion brève, le signal transmis s’allonge temporellement, car le milieu diffusant répond différemment pour les diverses composantes spectrales de l’impulsion. Nous avons développé, au cours de cette thèse, des méthodes de contrôle du profil spatiotemporel d’une impulsion brève transmise à travers un milieu diffusant. En mesurant la Matrice de Transmission Multi-Spectrale ou Résolue-Temporellement, la propagation de l’impulsion peut être totalement décrite dans le domaine spectral ou temporel. Avec des techniques de manipulation du front d’onde, les degrés de libertés spectraux/temporel peuvent être ajustés avec un unique SLM via la diversité spectrale du milieu diffusant. Nous avons démontré, de manière déterministe, la focalisation spatio-temporelle d’une impulsion brève après propagation dans un milieu diffusant, avec une compression temporelle proche de la durée initiale de l’impulsion, à différentes positions de l’espace-temps. Nous avons également démontré un façonnage contrôlé du profil temporel de l’impulsion, notamment avec la génération d’impulsions doubles. Nous exploitons cette focalisation spatio-temporelle pour exciter un processus optique non-linéaire, la fluorescence à deux photons. Cette approche ouvre des perspectives intéressantes pour le contrôle cohérent, l’étude de l’interaction lumière-matière ainsi que l’imagerie multi-photonique
Optical imaging through highly disordered media such as biological tissue or white paint remains a challenge as spatial information gets mixed because of multiple scattering. Nonetheless, spatial light modulators (SLM) offer millions of degrees of freedom to control the spatial speckle pattern at the output of a disordered medium with wavefront shaping techniques. However, if the laser generates a broadband ultrashort pulse, the transmitted signal becomes temporally broadened as the medium responds disparately for the different spectral components of the pulse. We have developed methods to control the spatio-temporal profile of the pulse at the output of a thick scattering medium. By measuring either the Multispectral or the Time- Resolved Transmission Matrix, we can fully describe the propagation of the broadband pulse either in the spectral or temporal domain. With wavefront shaping techniques, one can control both spatial and spectral/temporal degrees of freedom with a single SLM via the spectral diversity of the scattering medium. We have demonstrated deterministic spatio-temporal focusing of an ultrashort pulse of light after the medium, with a temporal compression almost to its initial time-width in different space-time position, as well as different temporal profile such as double pulses. We exploit this spatio-temporal focusing beam to enhance a non-linear process that is two-photon excitation. It opens interesting perspectives in coherent control, light-matter interactions and multiphotonic imaging

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8

Lo, Wai Bun. "Physical modelling and H[infinity] filtering for robust spatio-temporal estimation /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20LO.

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Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2003.
On t.p. "[infinity]" appears as the infinity symbol. Includes bibliographical references (leaves 88-92). Also available in electronic version. Access restricted to campus users.

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9

Coughlan, Matthew Anthony. "Controlling Light-Matter Interactions and Spatio-Temporal Properties of Ultrashort Laser Pulses." Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/186215.

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Chemistry
Ph.D.
The SPECIFIC method a fast and accurate method for generating shaped femtosecond laser pulses. The femtosecond pulses are user specified from pulse parameters in the temporal domain. The measured spectral and recovered temporal phase and amplitudes from SEA TADPOLE are compared with the theoretical pulse profile from the user specified input. The SPECIFIC method has been shown to be a technique that can generate a diverse array of spectral/temporal phase and amplitude as well as polarization pulse shapes for numerous scientific applications. The spatio -temporal -spectral properties of focusing femtosecond laser pulses are studied for several pulse shapes that are important for non-linear spectroscopic studies. We have shown with scanning SEA TADPOLE that the spatio-spectral phase of focusing double pulse profile changes across the laterally across the beam profile. The spectral features of the sinusoidal spectral phase shaped pulse has been shown to tilt at with a changing angle away from the focus of the lens. Using spatio-spectral coupling, we have shown that multiple spatio-temporal foci can be generated along and perpendicular to the focusing direction of a femtosecond laser pulse. The spatial position of the spatio-temporal foci is controlled optically. Using sinusoidal spectral phase modulated pulse trains fragment ion production from Benzonitrile parent molecule can be controlled. A spectral transmission window perturbed the temporal pulse amplitudes resulting in fragment ion production dependant on spectral window position. The spectral window ion production was shown to also be dependant on temporal phase sequence.
Temple University--Theses

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10

Grönlund, Christer. "Spatio-temporal processing of surface electromyographic signals : information on neuromuscular function and control." Doctoral thesis, Umeå universitet, Institutionen för strålningsvetenskaper, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-958.

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During muscle contraction, electrical signals are generated by the muscle cells. The analysis of those signals is called electromyography (EMG). The EMG signal is mainly determined by physiological factors including so called central factors (central nervous system origin) and peripheral factors (muscle tissue origin). In addition, during the acquisition of EMG signals, technical factors are introduced (measurement equipment origin). The aim of this dissertation was to develop and evaluate methods to estimate physiological properties of the muscles using multichannel surface EMG (MCsEMG) signals. In order to obtain accurate physiological estimates, a method for automatic signal quality estimation was developed. The method’s performance was evaluated using visually classified signals, and the results demonstrated high classification accuracy. A method for estimation of the muscle fibre conduction velocity (MFCV) and the muscle fibre orientation (MFO) was developed. The method was evaluated with synthetic signals and demonstrated high estimation precision at low contraction levels. In order to discriminate between the estimates of MFCV and MFO belonging to single or populations of motor units (MUs), density regions of so called spatial distributions were examined. This method was applied in a study of the trapezius muscle and demonstrated spatial separation of MFCV (as well as MFO) even at high contraction levels. In addition, a method for quantification of MU synchronisation was developed. The performance on synthetic sEMG signals showed high sensitivity on MU synchronisation and robustness to changes in MFCV. The method was applied in a study of the biceps brachii muscle and the relation to force tremor during fatigue. The results showed that MU synchronisation accounted for about 40 % of the force tremor. In conclusion, new sEMG methods were developed to study muscle function and motor control in terms of muscle architecture, muscle fibre characteristics, and processes within the central nervous system.

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11

Grönlund, Christer. "Spatio-temporal processing of surface electromyographic signals : information on neuromuscular function and control /." Umeå : Umeå universitet, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-958.

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12

Bouaru, Adrian. "Control of spatio-temporal pattern formation governed by geometrical models of interface evolution." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/11698/.

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Numerous natural phenomena are characterized by spatio-temporal dynamics which give rise to time evolving spatial patterns. Although studies that address the problem of modelling these complex dynamics exist, a model based control approach for such systems is still a challenging task. The work in this thesis is concerned with the development of control methods for such spatio-temporal systems, where interface growth is represented using a geometric evolution law. In particular, the focus is set on the control of dendritic crystal growth and wind-aided wildfire spread.

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13

Guzmán, Vendrell Mercè. "Spatio-temporal control of cell division in fission yeast by Cdr2 medial cortical nodes." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112179/document.

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Le but de ces travaux de thèse est d’apporter une meilleure compréhension des mécanismes de régulation contrôlant la division cellulaire au niveau moléculaire. La division cellulaire est composée de la mitose et la cytocinèse. Les deux processus doivent être coordonnés étroitement afin de garantir la stabilité du génome. La division cellulaire doit aussi s’équilibrer avec la croissance cellulaire pour que les cellules conservent une taille constante au cours des cycles successifs. La levure S. pombe est un organisme modèle simple très utilisé pour des études de cycle cellulaire et de cytocinèse. Dans ce modèle, nous avons focalisé ce travail de thèse sur les nœuds corticaux médians, des structures protéiques complexes, qui ont une fonction double dans l’engagement en mitose et dans le positionnement du plan de division. Les nœuds médians corticaux sont organisés par la kinase SAD Cdr2. Leur localisation et leur fonction sont régulées négativement pour la DYRK kinase Pom1 qui forme des gradients émanant des extrémités de la cellule. Les nœuds corticaux médians contiennent une voie d’inhibition pour Wee1 qui promeut l’entrée en mitose. Cette voie implique la kinase SAD Cdr1, un inhibiteur direct de Wee1 et pourrait coupler l’entrée en mitose à la taille de la cellule par levée progressive de l’inhibition exercée par Pom1 quand les cellules s’allongent. Cdr2 recrute aussi l’anillin Mid1 sur les nœuds corticaux médians ainsi qu’une série de composants additionnels, Blt1, Gef2, Nod1 et Klp8, pour former des précurseurs médians de l’anneau contractile de cytocinèse qui se compactent en un anneau fin pendant la mitose. La localisation médiane des nœuds, contrôlée négativement par les gradients polaires de Pom1 prédéfinit ainsi le plan de division au centre géométrique de la cellule. Dans la première partie de ma thèse, j’ai étudié la protéine des nœuds corticaux médians Blt1 dont la fonction restait énigmatique. Nous avons montré que Blt1 promeut une association robuste de Mid1 avec les nœuds corticaux. Blt1 interagit avec Mid1 via le RhoGEF Gef2 pour stabiliser les nœuds au cortex cellulaire durant les premiers stades de l’assemblage de l’anneau contractile. L’extrémité N-terminale de Blt1 est nécessaire à sa localisation ainsi qu’à sa fonction, tandis que son extrémité C-terminale favorise sa localisation au cortex en interagissant avec des phospholipides. Dans des cellules dans lesquelles ni Mid1 ni Blt1 ne peuvent s’attacher à la membrane, les nœuds se détachent du cortex et génèrent des anneaux contractiles de cytocinèse aberrants. Nous en avons conclu que Blt1 agit comme une protéine d’échafaudage pour les précurseurs de l’anneau contractile, et que Blt1 et Mid1 constituent des ancres membranaires redondantes pour le positionnement du plan de division. Dans une deuxième partie de ma thèse, j’ai étudié comment Cdr2 organise les différents composants des nœuds en voies fonctionnelles qui favorisent l’entrée en mitose et la division médiane. J’ai montré que l’interaction de Cdr2 avec Wee1 et Mid1 dépend du domaine UBA de Cdr2 de manière dépendante de l’activité kinase. En revanche, Cdr1 s’associe avec l’extrémité C-terminale de Cdr2, composée des domaines basique et KA1 d’association aux lipides membranaires. De manière intéressante, Mid1 interagit également avec l’extrémité C-terminale de Cdr2 et pourrait ponter les parties N- et C-terminales de Cdr2, alors que Blt1 s’associe à la région centrale de Cdr2. Nous faisons l’hypothèse que l’association des effecteurs de Cdr2 avec différents domaines de Cdr2 pourraient contraindre Cdr1 et Wee1 spatialement pour promouvoir l'inhibition de Wee1 quand la kinase Cdr2 est active
The aim of this PhD work is to bring a better understanding of the regulatory mechanism controlling cell division in space and time at the molecular level. Cell division is composed of mitosis and cytokinesis. Both processes need to be perfectly coordinated in order to guarantee genome integrity. Cell division also needs to be properly balanced with cell growth to maintain cell size constant during successive cell cycles. Temporal and spatial regulatory mechanisms ensure the coordination of these events. The fission yeast Schizosaccharomyces pombe is a simple rod-shaped model organism well-known for cell cycle and cytokinesis studies. In this model, we focused the work of this thesis on the medial cortical nodes, complexe protein structures that have a dual role in mitotic commitment and in division plane positioning. Medial cortical nodes are organized by the SAD kinase Cdr2. Their localization and function is negatively regulated by the DYRK kinase Pom1 that forms a gradient emanating from the cell tips. Medial cortical nodes contain an inhibitory pathway for Wee1, promoting mitotic entry. This pathway involves the SAD kinase Cdr1, a direct inhibitor of Wee1 and has been proposed to couple mitotic entry to cell size by progressive alleviation of Pom1 inhibition when cells grow longer. Cdr2 also recruits to medial nodes the anillin Mid1 as well as a series of four additional components, Blt1, Gef2, Nod1 and Klp8, to form medial precursors for the cytokinetic contractile ring that compact into a tight ring during mitosis. Nodes medial localization, negatively controlled by Pom1 gradients, predefines thereby the division plane in the cell geometrical center. In a first part of my thesis, I studied the previously enigmatic cortical node protein Blt1. We showed that Blt1 promotes the robust association of Mid1 with cortical nodes. Blt1 interacts with Mid1 through the RhoGEF Gef2 to stabilize nodes at the cell cortex during the early stages of contractile ring assembly. The Blt1 N terminus is required for localization and function, while the Blt1 C terminus promotes cortical localization by interacting with phospholipids. In cells lacking membrane binding by both Mid1 and Blt1, nodes detach from the cell cortex and generate aberrant cytokinetic rings. We conclude that Blt1 acts as a scaffolding protein for precursors of the cytokinetic ring and that Blt1 and Mid1 provide overlapping membrane anchors for proper division plane positioning. In the second part of my thesis, I studied how Cdr2 scaffolds various nodes components to organize them in functional pathways promoting mitotic commitment and medial division. I showed that Cdr2 interaction with Wee1 and Mid1, depends on Cdr2 UBA domain in a kinase activity dependent manner. In contrast, Cdr1 associates with Cdr2 C-terminus composed of basic and KA-1 lipid-binding domains. Interestingly, Mid1 also interacts with Cdr2 C-terminus and may the bridge N- and C-terminal domains of Cdr2 while Blt1 associates with the central spacer region. We propose that the association of Cdr2 effectors with different Cdr2 domains may constrain Cdr1 and Wee1 spatially to promote Wee1 inhibition upon Cdr2 kinase activation

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14

Garcia, De Las Bayonas Alain. "Spatio-temporal and quantitative control of Rho1 activity by GPCR signaling during tissue morphogenesis." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0548/document.

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La constriction apicale des cellules du mésoderme et l'intercalation des cellules de l'ectoderme sont contrôlées par des réseaux contractiles d'acto-myosine dans l'embryon de Drosophile. Le niveau d'activation et la polarisation du cytosquelette d'acto-myosine détermine la nature des déformations cellulaires observées. Nous montrons que le GPCR Smog et les protéines G (Gα,Gβγ) en aval, activent la signalisation Rho1 et donc la Myosine-II dans les deux tissus. Dans l'ectoderme, Gα12/13 active Rho1 à la membrane apicale (aussi appelé compartiment médio-apical) tandis que les sous-unités Gβ13F-Gγ1 activent Rho1 en médio-apical et aux jonctions cellulaires. Les mécanismes contrôlant l’activation polarisée de Rho1 dans ce tissu demeurent incompris. Nous montrons ici que deux RhoGEFs, RhoGEF2 et une nouvelle RhoGEF Wireless/p114RhoGEF, activent Rho1 sous le contrôle des protéines G dans l’ectoderme. RhoGEF2 stimule Rho1 en médio-apical sous la dépendance de Gα12/13 alors que Wireless/p114RhoGEF contrôle l’activité de Rho1 aux jonctions avec Gβ13F-Gγ1. RhoGEF2 est présente aux jonctions et en médio-apical tandis que Wireless/p114RhoGEF est uniquement jonctionnelle où elle est recrutée par Gβ13F-Gγ1. Pour finir, Wireless/p114RhoGEF est absente des jonctions dans les cellules du mésoderme. En résumé, des GPCRs contrôlent l’activité spatio-temporelle de Rho1 au moyen de deux modules régulatoires dans l’ectoderme. Les protéines G transduisent le signal en recrutant et en activant deux RhoGEFs complémentaires en médio-apical et aux jonctions. Une variation dans la nature des GPCRs, protéines G ou des RhoGEFs détermine le contrôle tissu-spécifique de Rho1 au cours de la morphogenèse
Cell apical constriction in the mesoderm and cell intercalation in the ectoderm are controlled by contractile actomyosin networks in the developing Drosophila embryo. The extent of both actomyosin activation and polarization determines the nature of these cell deformations. We find that the GPCR Smog and the downstream G proteins (Gα,Gβγ) activate Rho1 signaling and thereby myosin-II in both tissues. In the ectoderm, Gα12/13 activates Rho1 at the apical membrane (also called medial-apical compartment) while Gβ13F-Gγ1 subunits promote Rho1 activity at the apical membrane and at cell junctions. How such a polarized activation of Rho1 is achieved remains unclear. Here, we show that two RhoGEFs, RhoGEF2 and a previously uncharacterized RhoGEF Wireless/p114RhoGEF, control Rho1 activity downstream of G proteins in the ectoderm. RhoGEF2 activates medial-apical Rho1 under control of Gα12/13 and Wireless/p114RhoGEF is required to mediate Gβ13F-Gγ1-dependent activation of Rho1 at junctions. RhoGEF2 is present both at junctions and at the apical membrane. In contrast, Wireless/p114RhoGEF only localizes at junctions together with Gβ13F-Gγ1 which recruit the GEF. Finally, we show that Wireless/p114RhoGEF is absent from junctions in the mesoderm. Collectively, GPCRs shape Rho1 activity through distinct biochemical modules in the ectoderm. Heterotrimeric G proteins transduce the signal by recruiting and activating two complementary RhoGEFs apically and at junctions. Variation in type of GPCRs, G proteins or RhoGEFs underlie the tissue-specific control of Rho1 signaling during morphogenesis

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15

Dufourd, Claire Chantal. "Spatio-temporal mathematical models of insect trapping : analysis, parameter estimation and applications to control." Thesis, University of Pretoria, 2016. http://hdl.handle.net/2263/58471.

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This thesis provides a mathematical framework for the development of efficient control strategies that satisfy the charters of Integrated Pest Management (IPM) which aims to maintain pest population at a low impact level. This mathematical framework is based on a dynamical system approach and comprises the construction of mathematical models, their theoretical study, the development of adequate schemes for numerical solutions and reliable procedures for parameter identification. The first output of this thesis is the construction of trap-insect spatio-temporal models formulated via advection-diffusion-reaction processes. These models were used to simulate numerically trapping to compare with field data. As a result, practical protocols were identified to estimate pest-population size and distribution as well as its dispersal capacity and parameter values related to the attractiveness of the traps. The second major output of this thesis is the prediction of the impact of a specific control method: mating disruption using a female pheromone and trapping. A compartmental model, formulated via a system of ordinary differential equations, was built based on biological and mating behaviour knowledge of the pest. The theoretical analysis of the model yields threshold values for the dosage of the pheromone above which extinction of the population is ensured. The practical relevance of the results obtained in this thesis shows that mathematical modelling is an essential supplement to experiments in optimizing control strategies.
Thesis (PhD)--University of Pretoria, 2016.
Mathematics and Applied Mathematics
PhD
Unrestricted

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16

Marshall, J. Brooke. "Prospective Spatio-Temporal Surveillance Methods for the Detection of Disease Clusters." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/29639.

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In epidemiology it is often useful to monitor disease occurrences prospectively to determine the location and time when clusters of disease are forming. This aids in the prevention of illness and injury of the public and is the reason spatio-temporal disease surveillance methods are implemented. Care must be taken in the design and implementation of these types of surveillance methods so that the methods provide accurate information on the development of clusters. Here two spatio-temporal methods for prospective disease surveillance are considered. These include the local Knox monitoring method and a new wavelet-based prospective monitoring method. The local Knox surveillance method uses a cumulative sum (CUSUM) control chart for monitoring the local Knox statistic, which tests for space-time clustering each time there is an incoming observation. The detection of clusters of events occurring close together both temporally and spatially is important in finding outbreaks of disease within a specified geographic region. The local Knox surveillance method is based on the Knox statistic, which is often used in epidemiology to test for space-time clustering retrospectively. In this method, a local Knox statistic is developed for use with the CUSUM chart for prospective monitoring so that epidemics can be detected more quickly. The design of the CUSUM chart used in this method is considered by determining the in-control average run length (ARL) performance for different space and time closeness thresholds as well as for different control limit values. The effect of nonuniform population density and region shape on the in-control ARL is explained and some issues that should be considered when implementing this method are also discussed. In the wavelet-based prospective monitoring method, a surface of incidence counts is modeled over time in the geographical region of interest. This surface is modeled using Poisson regression where the regressors are wavelet functions from the Haar wavelet basis. The surface is estimated each time new incidence data is obtained using both past and current observations, weighing current observations more heavily. The flexibility of this method allows for the detection of changes in the incidence surface, increases in the overall mean incidence count, and clusters of disease occurrences within individual areas of the region, through the use of control charts. This method is also able to incorporate information on population size and other covariates as they change in the geographical region over time. The control charts developed for use in this method are evaluated based on their in-control and out-of-control ARL performance and recommendations on the most appropriate control chart to use for different monitoring scenarios is provided.
Ph. D.

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17

Gütlich, Björn. "Control of nonlinear optical structures from the guiding of dissipative solitons to spatio-temporal synchronisation." Göttingen Cuvillier, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016214833&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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18

Menendez, Guillermo. "Spatio-temporal control of neurotrophin trafficking and signalling in primary neurons cultured inside microfluidic chambers." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6417.

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My PhD project was aimed at applying microfluidics technology to the study of longrange neurotrophin signalling. Neurotrophins are target-derived growth and survival factors that, among other functions, prevent innervating neurons from undergoing apoptosis. Neurotrophins and their receptors have been shown to be transported retrogradely in axons of spinal cord neurons, following a pathway they share with the tetanus neurotoxin binding fragment (TeNT Hc), and which is controlled by the small GTPase Rab7. The Rab7-dependent pathway is thought to trigger downstream signalling events such as the phosphorylation of the transcription factor CREB, important in promoting neuronal survival and differentiation, but direct evidence for this had not yet been provided. To provide direct evidence of this functional relationship between Rab7 activity and CREB phosphorylation, I established microfluidic cultures of spinal cord motor and sensory neurons, in which axonal networks can be treated independently of cell bodies. I used a microfabrication technique known as soft lithography to produce microfluidic chambers. They consist of two parallel compartments interconnected by an array of microgrooves. In this culture system, dorsal root ganglia (DRG) neurons cultured in one of the compartments (somato-dendritic side) can be chemoattracted by gradients of nerve growth factor (NGF) to grow their axons preferentially into the other compartment (axonal side). Control studies by immunofluorescence confocal microscopy of CREB phosphorylation following direct stimulation of DRG cell bodies with NGF in mass cultures and in microfluidic chambers showed no significant differences between these two systems, confirming that the signalling cascade remains unmodified in microfluidic cell cultures. Time-course analysis of CREB phosphorylation in DRG neurons prepared from E18.5 embryos surprisingly revealed a lack of response following NGF stimulation of axon terminals in microfluidic cultures. I tried DRG cultures from E14.5 embryos because a fraction of the total population of DRG neurons during development undergo apoptosis at around E15-E16 if they fail to reach their target tissues. In these cultures, CREB phosphorylation could be observed when stimulating axons with NGF in microfluidic chambers. These results suggest that this long-range signalling pathway is active during a period of development when DRG neurons depend critically on their supply of targetderived neurotrophins, but it is down-regulated at later developmental stages. To gain some further insight into the mechanisms controlling this long range signalling response, and specifically to study the role of Rab7 in this context, I infected E14.5 DRG neurons with lentivirus carrying wild type or a dominant negative mutant of Rab7 (Rab7T22N) coupled to a fluorescent tag. Overexpression of mCherry Rab7T22N affected CREB phosphorylation, significantly reducing the signal generated in distal axons. To confirm this result, I prepared lentivirus carrying shRNA sequences targeting Rab7, and analysed the response to axonal NGF after knocking down the endogenous protein. This different approach also abolished CREB phosphorylation after NGF stimulation of the axonal network in microfluidic chambers. My results provide a direct link between Rab7 activity and downstream effects of the signalling cascade initiated by neurotrophins at axonal networks in compartmentalised microfluidic chambers.

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19

Sharma, Balaji R. "Real-time Monitoring and Estimation of Spatio-Temporal Processes Using Co-operative Multi-Agent Systems for Improved Situational Awareness." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382950922.

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20

Schürholz, Anne-Kathrin [Verfasser], and Jan [Akademischer Betreuer] Lohmann. "Spatio-temporal control of cell wall propterties and signalling networks in Arabidopsis meristems / Anne-Kathrin Schürholz ; Betreuer: Jan Lohmann." Heidelberg : Universitätsbibliothek Heidelberg, 2019. http://d-nb.info/119237312X/34.

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21

Schürholz, Anne-Kathrin [Verfasser], and Jan U. [Akademischer Betreuer] Lohmann. "Spatio-temporal control of cell wall propterties and signalling networks in Arabidopsis meristems / Anne-Kathrin Schürholz ; Betreuer: Jan Lohmann." Heidelberg : Universitätsbibliothek Heidelberg, 2019. http://nbn-resolving.de/urn:nbn:de:bsz:16-heidok-269083.

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22

Crespo-Yapur, Diego Alfonso. "Cooperative behavior of micro-objects under electrochemical control." Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAF028.

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De nombreux systèmes électrochimiques sont composés d'un grand nombre d'éléments électroactifs en interaction. Si la réaction électrochimique possède une cinétique non linéaire, des comportements coopératifs complexes peuvent émerger suivant la nature et l’intensité des interactions entre les éléments du système. L'objectif de cette thèse est de comprendre l'influence de la taille finie de l’électrode et des interactions entre les microélectrodes sur le comportement coopératif d'un groupe de microélectrodes de platine soumis à un couplage global. Les réactions choisies pour cette étude sont l’électrooxydation du monoxyde de carbone (CO), une réaction avec une cinétique bistable et l’électrooxydation du formaldéhyde (HCHO), qui présente des oscillations de potentiel sous contrôle galvanostatique. Au cours de l’électrooxydation galvanodynamiques du CO sur une seule microélectrode de Pt, la branche S-NDR a pu être mise en évidence contrairement au comportement observé sur une macroélectrode de Pt. En outre, les nouveaux comportements coopératifs comme l'activation séquentielle des microélectrodes, des oscillations de courant et de potentiel spontanées et un régime de commutation dynamique entre les électrodes ont été découverts pour cette réaction lorsque quatre électrodes ont été couplées globalement. Pendant l’électrooxydation de HCHO, l'introduction du couplage global à deux électrodes conduit à des oscillations de courant en opposition de phase
Many electrochemical systems are composed of a large number of interacting electroactive elements. If the reaction taking place on them has nonlinear kinetics and their interactions allow them to exchange information, complex cooperative behaviors can emerge. The objective of this thesis is to understand the influence of finite-size effects and cooperative phenomena on the global behavior of a group of coupled Pt microelectrodes. The reactions chosen for this study were CO electrooxidation, a reaction with current bistability, and HCHO electrooxidation, which exhibits oscillations under galvanostatic control. During the galvanodynamic electrooxidation of CO on a single microelectrode the S-NDR branch could be evidenced, on macroelectrodes this is not possible due to the formations of stationary domains. Additionally, novel cooperative behaviors (i.e., sequential activation, oscillations and complex switching) were discovered for this reaction when four electrodes were globally coupled. During HCHO electrooxidation the introduction of global coupling to two electrodes led to anti-phase current oscillations

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23

Gagic, Vesna [Verfasser], Teja [Akademischer Betreuer] Tscharntke, Stefan [Akademischer Betreuer] Vidal, and Ulrich [Akademischer Betreuer] Brose. "Agricultural intensification, biological pest control and spatio-temporal changes in food web structure / Vesna Gagic. Gutachter: Teja Tscharntke ; Stefan Vidal ; Ulrich Brose. Betreuer: Teja Tscharntke." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2011. http://d-nb.info/1042641765/34.

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24

Xue, Kai. "Modal filtering for active control of floor vibration under impact loading." Kyoto University, 2018. http://hdl.handle.net/2433/232024.

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25

Jansen, Remco. "Costly victories? : The dynamics of territorial control and insurgent violence against civilians within civil war." Thesis, Uppsala universitet, Institutionen för freds- och konfliktforskning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353896.

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Limited systematic research has investigated how conflict events shape the spatial-temporal variation of insurgent violence against civilians. Although previous research has investigated how degrees of territorial control relate to general levels of violence against civilians, it remains largely an open question how the dynamics within territorial control determine violence against civilians by insurgents. This study aims to address this gap by hypothesizing that (1) insurgents become more likely to commit fatal violence against civilians, and (2) kill more civilians in contested areas when they lose territorial control. The Armed Conflict Location and Event Dataset (ACLED) was used along with Peace Research Institute Oslo’s (PRIO) GRID Dataset to create a novel data frame of all territorially contested area-weeks on the African continent between 1997 and 2017 (n = 3035). Contrary to theoretical expectations, logistic regressions indicate a lower risk of insurgent violence against civilians in contested areas following an insurgent territorial loss than following a break-even. Zero-inflated negative binomial regressions moreover tentatively indicate that insurgents kill more civilians following territorial wins in the short-term, and following territorial loss in the long-term. These results suggest that proactive counterinsurgency campaigns are in the interest of civilians in civil war.

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26

Vuran, Mehmet Can. "Correlation-based Cross-layer Communication in Wireless Sensor Networks." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16135.

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Wireless sensor networks (WSN) are event based systems that rely on the collective effort of densely deployed sensor nodes continuously observing a physical phenomenon. The spatio-temporal correlation between the sensor observations and the cross-layer design advantages are significant and unique to the design of WSN. Due to the high density in the network topology, sensor observations are highly correlated in the space domain. Furthermore, the nature of the energy-radiating physical phenomenon constitutes the temporal correlation between each consecutive observation of a sensor node. This unique characteristic of WSN can be exploited through a cross-layer design of communication functionalities to improve energy efficiency of the network. In this thesis, several key elements are investigated to capture and exploit the correlation in the WSN for the realization of advanced efficient communication protocols. A theoretical framework is developed to capture the spatial and temporal correlations in WSN and to enable the development of efficient communication protocols. Based on this framework, spatial Correlation-based Collaborative Medium Access Control (CC-MAC) protocol is described, which exploits the spatial correlation in the WSN in order to achieve efficient medium access. Furthermore, the cross-layer module (XLM), which melts common protocol layer functionalities into a cross-layer module for resource-constrained sensor nodes, is developed. The cross-layer analysis of error control in WSN is then presented to enable a comprehensive comparison of error control schemes for WSN. Finally, the cross-layer packet size optimization framework is described.

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27

Jebali, Syrine. "Vers un traitement superhydrophobe, durable et respectueux de l’environnement pour le textile : la solution de la polymérisation plasma." Thesis, Mulhouse, 2021. http://www.theses.fr/2021MULH4345.

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L'industrie textile s’intéresse depuis longtemps aux propriétés superhydrophobes et auto-nettoyantes. Le dépôt de composés fluorés à longues chaînes carbonées à la surface des textiles est actuellement le moyen le plus efficace d’obtenir de telles propriétés. En raison de leurs effets néfastes sur la santé et l'environnement, ces composés doivent être remplacés conformément à la réglementation REACH. Dans cette thèse, la polymérisation plasma a été choisie pour concevoir des traitements de surface durables, superhydrophobes et respectueux de l'environnement pour textiles. Dans ce contexte, la possibilité de contrôler temporellement et spatialement la cinétique de polymérisation plasma d'un précurseur modèle largement étudié à l'IS2M, à savoir l'anhydride maléique, a été démontrée dans un réacteur original d'un mètre de long. De plus, la possibilité de contrôler les propriétés chimiques et morphologiques des films polymères a été abordée. Suivant une méthodologie expérimentale similaire, le contrôle de la polymérisation plasma d'un précurseur organosiliconé, à savoir l’hexaméthyldisiloxane (HMDSO) a été étudié pour obtenir un revêtement superhydrophobe vert. L'accent a été mis sur la compréhension de la résistance au lavage de ces revêtements en caractérisant la cohésion du revêtement et de son adhérence à la fibre. Enfin, un second précurseur non fluoré a été testé en tant qu’alternative innovante à l’HMDSO. En contrôlant finement les paramètres temporels et spatiaux de la décharge plasma, les performances de superhydrophobie des polymères plasma et leurs durabilités ont pu être modifiées, soulignant l’approche tout à fait pertinente développée dans ce travail de thèse
The textile industry has been interested for long in water-repellency and self-cleaning properties. Deposition of fluorinated compounds with long carbon chains on the surface of textiles is currently the most efficient solution to reach such properties. Because of their harmful effects on health and environment, these chemicals have to be replaced in accordance with REACH specifications. During this PhD work, plasma polymerization process has been chosen as a good candidate to engineer durable, superhydrophobic and eco-friendly surface treatments for textiles. In this context, we successfully demonstrated the possibility to control temporally and spatially plasma polymerization kinetics of a model precursor widely studied at the IS2M, namely maleic anhydride, in an original one-meter long reactor. More than that, the possibility to control the chemical and morphological properties of plasma coatings was particularly addressed. Following a similar experimental methodology, the control of plasma polymerization of an organosilicon precursor, namely hexamethyldisiloxane (HMDSO), was investigated to get eco-friendly superhydrophobic coating. A focus was made on the understanding of thin film resistance to washing by characterizing coating cohesion and adhesion to the textile fiber. Finally, a second fluorine-free precursor was tested as an innovative alternative to HMDSO to engineer eco-friendly superhydrophobic coatings. By a fine tuning of temporal and spatial parameters of the plasma discharge, water-repellency performances of plasma polymer coatings and their durability could be significantly modified, highlighting the interesting approach developed during this PhD work

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28

Stockinger, Michael Paul [Verfasser]. "Streamwater transit time distributions at the catchment scale: constraining uncertainties through identification of spatio-temporal controls / Michael Paul Stockinger." Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1103135163/34.

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29

Ciardo, Diletta. "Quantitative analysis of the regulation of the DNA replication program by the intra-S phase checkpoint in Xenopus embryos Checkpoint control of the spatio-temporal regulation of DNA replication in Xenopus early embryos Polo-like kinase 1 (Plk1) is a positive regulator of DNA replication in the Xenopus in vitro system On the Interplay of the DNA Replication Program and the Intra-S Phase Checkpoint Pathway Genome wide decrease of DNA replication eye density at the midblastula transition of Xenopus laevis Polo like kinase 1 promotes dispersed replication origin firing during S phase." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS478.

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Dans les organismes multicellulaires, plusieurs millier d’origines initient la réplication de l'ADN. Elles sont regroupées en domaines qui se répliquent tôt ou tard au cours de la phase S (origines précoces ou tardives). L'un des mécanismes régulant le programme de réplication est un point de contrôle intra phase S qui dépend des kinases ATR et Chk1. Cette voie est activée par un stress réplicatif engendré par le blocage des fourches de réplication aux origines précoces, en retour elle inhibe l’activation des origines tardives. Il a été proposé, que la protéine Polo-Like-Kinase 1 (Plk1) soit responsable du déclenchement des origines situées à proximité des fourches bloquées en cas de stress réplicatif. Cependant, aucune analyse de l’activation des origines n’a jamais été réalisée au cours d’une phase S non perturbée lorsque Plk1 est absente. Pour avoir une vue globale et unifiée du processus de réplication de l'ADN, des modèles numériques et analytiques ont été construits dans le passé, mais aucun d'eux n'intègrent le rôle de Chk1 et Plk1. L'objectif de ma thèse était d’étudier expérimentalement et analytiquement de quelle manière Chk1 peut réguler le déclenchement des origines dans l'espace et dans le temps. En particulier, de comprendre si Plk1 pouvait être impliquée dans cette régulation pendant une phase S non perturbée, à cette fin, j'ai utilisé le système réplicatif des extraits d’œuf de Xénopes. En premier lieu, j'ai intégré dans un modèle numérique l’action de Chk1 pour reproduire le programme de réplication du système Xénope. J'ai testé différents scénarios puis j’ai utilisé des données de peignage d'ADN obtenues précédemment dans des conditions d'inhibition de la kinase Chk1. Les simulations Monte Carlo obtenues ont été ajustées aux données expérimentales en optimisant les valeurs des paramètres libres des modèles. J'ai trouvé qu'il fallait ajouter deux hypothèses aux modèles de réplication développés précédemment: 1) la présence d’une forte inhibition du déclenchement des origines par Chk1 à partir du début de la phase S 2) la présence de domaines génomiques répliquant précocement et qui échappent à cette inhibition. Deuxièmement, j'ai montré expérimentalement que, Plk1 actif est recrutée sur la chromatine avant le début de la phase S non perturbée et qu'en l'absence de Plk1, la réplication de l'ADN est ralentie. De plus, l’absence de Plk1 entraîne une augmentation de la phosphorylation de Chk1 et une diminution de l’activité de la kinase Cdk2, ce qui suggère que Plk1 inhibe Chk1. En réalisant des expériences de peignage d’ADN, j'ai démontré qu’en l’absence de Plk1 on observe une baisse du niveau d’activation des origines. L'analyse de ces données par mon modèle numérique suggère que Plk1 régule négativement l’action de Chk1 levant ainsi son action inhibitrice sur l’activation globale des origines. Cet effet concorde avec mes observations expérimentales. Il semble cependant que Plk1 n’agisse pas à proximité directe des fourches de réplication, comme cela avait été proposé précédemment. Enfin, en assimilant le processus de réplication à un processus de nucléation et de croissance unidimensionnel, j'ai développé une nouvelle approche quantitative pour étudier la régulation du programme de réplication. Cette approche lie la similarité entre les profils spatiaux de réplication d'une molécule unique et les processus de régulation de la réplication de l'ADN. En analysant les données de peignage d'ADN, j'ai montré que le programme de réplication de l'ADN des embryons précoces de Xénope est régulé par deux processus exclusifs dans l'espace et dans le temps. L’un avec une fréquence faible d’activation des origines et une vitesse apparente de fourches élevée et un second, régulé par Plk1, présentant une fréquence d’activation élevée des origines avec une vitesse apparente de fourches faible
The initiation of DNA replication in multicellular organisms starts from several thousand genomic loci called replication origins. They are grouped into domains which replicate early or late during S phase. The firing of a replication origin creates two diverging replication forks that replicate flanking DNA. One of the mechanisms regulating DNA replication program is the ATR/Chk1 dependent intra-S phase checkpoint. This pathway is activated by replicative stress due to stalled replication forks at early firing origins and in turn, inhibits the late firing of origins. It has been proposed that the checkpoint recovery kinase Plk1 (Polo-Like-Kinase 1) could be responsible for allowing origin firing close to stalled forks in replication stress conditions. However, origin firing has not been analysed after Plk1 inhibition or depletion during unperturbed S phase. To assemble a comprehensive and unified view of the DNA replication process numerical and analytical models have been built in the past, but none of them integrates the role of checkpoint pathways. The goal of my thesis was to investigate experimentally and analytically how the checkpoint regulates the firing of origins in space and time and, in particular, whether the Plk1 is implicated in the regulation of origin firing during unperturbed S phase. To this end, I used the Xenopus in vitro system. First, I integrated in a numerical model the checkpoint pathway to describe the replication program in the Xenopus in vitro system. I tested different scenarios and used DNA combing data previously obtained by the laboratory after the inhibition of the checkpoint kinase Chk1. Monte Carlo simulated data were fitted to experimental data by optimizing the values of free parameters of models using a genetic algorithm. I found that two new hypothesis should be added to formerly built replication models: 1) a strong inhibition of origin firing by Chk1 from the beginning of S phase 2) the presence of early replicating genomic domains that evade the origin firing inhibition. Second, I experimentally showed that during unperturbed S phase active Plk1 is recruited to chromatin before the start of S phase and that in the absence of Plk1, DNA replication is slowed down. Moreover, Plk1 depletion led to an increase in Chk1 phosphorylation (p-Chk1) and a decrease of Cdk2 activity, suggesting that Plk1 inhibits the intra-S phase checkpoint. Performing DNA combing, I demonstrated that Plk1 depletion leads to a decrease in origin firing level. Analysis of the combing data by the developed numerical model suggested that during unchallenged S phase Plk1 down regulates the global origin firing inhibitory action of Chk1, consistent with the experimental observation of increased level of p-Chk1 in Plk1 depleted Xenopus egg extract. However, Plk1 does not seem to act close to replication forks as was proposed earlier. Finally, by considering replication process as a one-dimensional nucleation and growth process and using statistical methods, I developed a new quantitative approach to study the regulation of replication program. This approach links the similarity between single molecule replication patterns to DNA replication regulating processes. By analyzing DNA combing data, I showed that DNA replication program in Xenopus early embryos is regulated by two spatially and temporally exclusive processes. One with low frequency of origin firing and high apparent fork speed and a second, controlled by PlK1, with a high frequency of origin firing and a low apparent fork speed. Altogether my results demonstrate that Plk1 positively regulates replication origin firing during normal S phase by down regulating the replication checkpoint. The numerical model predicts the existence of replication timing domains in the Xenopus model system. Future work will show whether Plk1 regulates the replication program at the level of genomic domains

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Zgheib, Taline. "Trajectoires du risque avalancheux résultant de changements sociaux-environnementaux dans les hautes vallées des Alpes françaises." Thesis, Université Grenoble Alpes, 2021. http://www.theses.fr/2021GRALU010.

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Les avalanches de neiges sont répandues dans les zones montagneuses. Elles menacent les personnes, détruisent les bâtiments et bloquent les routes. Historiquement, les approches visant à réduire le risque d’avalanche étaient basées seulement sur l’aléa, qui est une composante du risque. Récemment, des analyses de risques plus complètes ont émergé associant aléas, exposition et vulnérabilité. Cependant, leurs applications restent le plus souvent statiques. En effet, elles négligent les évolutions à long terme du risque résultantes des évolutions simultanées de ses trois composantes. Elles ignorent également les variations spatio-temporelles, à l’échelle locale, des systèmes sociaux et naturels (par exemple, dynamique des populations, économie, évolution des écosystèmes, changement climatique) ainsi que leurs interactions (par exemple, l’exploitation forestière). Par conséquent, la variabilité locale des trajectoires de risque d’avalanche ne peut pas être prise en compte. Enfin, les estimations de risque générées dans un cadre d’analyse quantitatives négligent généralement les changements d’occupation des sols. En particulier l’évolution du couvert forestier qui peut potentiellement modifier l’activité des avalanches et par conséquent le risque d’avalanche. Ainsi, l’objectif de cette thèse est tout d’abord de développer une approche qualitative intégrative. Cette approche combine les informations issues des sciences naturelles et sociales pour évaluer l’évolution à long terme du risque d’avalanche et de toutes ses composantes (aléa, vulnérabilité et exposition), en fonction de l’évolution des facteurs socio-économiques, environnementaux et climatiques. Ensuite le second objectif est d’étudier dans quelle mesure les particularités socio-économiques et environnementales locales peuvent entraîner des disparités spatiales et temporelles dans les trajectoires de risque. Enfin, le dernier objectif est de proposer des estimations quantitatives du risque d’avalanche qui prennent en compte les changements du couvert forestier dans les trajectoires d’avalanche. La thèse se focalise sur les Alpes Françaises, pendant la période 1860-2017, qui est une zone d’avalanche très active et qui a connu d’importants changements socio-économiques et environnementaux aux fils des années
Snow avalanches are prevalent processes in mountain areas, threatening people, destroying buildings and blocking roads. Historically, approaches to reduce avalanche risk were based on the sole hazard component of risk. Recently, more comprehensive risk analyses emerged that couple hazard, exposure and vulnerability. However, existing implementations remain more often than not static, neglecting long term changes in the risk resulting from the simultaneous evolution of its three components. They also ignore the small-scale spatio-temporal patterns in the social (e.g. population dynamics, economy) and natural systems (e.g. evolution ofecosystems, climate change) as well as in their interactions (e.g. forest logging). Consequently, local variability in avalanche risk trajectories cannot be accounted for. Eventually, risk estimates generated within a quantitative risk framework generally neglect land cover changes, notably forest cover evolution, that can potentially alter avalanche activity and, hence, avalanche risk.On this basis, the aims of this PhD are to (i) develop an integrative qualitative approach combining knowledge from natural and social sciences to assess long term changes in avalanche risk and in all its components, hazard, vulnerability and exposure, as function of changes in their socio-economic and environmental drivers, (ii) investigate to which extent local socioeconomic, land cover and climatic peculiarities may lead to spatial and temporal disparities in risk trajectories and (iii) propose quantitative avalanche risk estimates that take into account changes in forest cover within avalanche paths. Herein, the focus is on the high mountains of the French Alps for the 1860-2017 period, a highly active avalanche area that witnessed important socio-economic and environmental changes over the years. All in all, this PhD illustrates how strongly snow avalanche risk evolves in space and time, as function of changes in its components and drivers. Ultimately, the work proposed may be of great interest for stakeholders looking to elaborate effective risk protection strategies that consider the complex dynamics of the human and natural systems

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Biard, Romain. "Dépendance et événements extrêmes en théorie de la ruine : étude univariée et multivariée, problèmes d'allocation optimale." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00539886.

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Cette thèse présente de nouveaux modèles et de nouveaux résultats en théorie de la ruine, lorsque les distributions des montants de sinistres sont à queue épaisse. Les hypothèses classiques d'indépendance et de stationnarité, ainsi que l'analyse univariée sont parfois jugées trop restrictives pour décrire l'évolution complexe des réserves d'une compagnie d'assurance. Dans un contexte de dépendance entre les montants de sinistres, des équivalents de la probabilité deruine univariée en temps fini sont obtenus. Cette dépendance, ainsi que les autres paramètres du modèle sont modulés par un processus Markovien d'environnement pour prendre en compte des possibles crises de corrélation. Nous introduisons ensuite des modèles de dépendance entre les montants de sinistres et les temps inter-sinistres pour des risques de type tremblements de terre et inondations. Dans un cadre multivarié, nous présentons divers critères de risques tels que la probabilité de ruine multivariée ou l'espérance de l'intégrale temporelle de la partie négative du processus de risque. Nous résolvons des problèmes d'allocation optimale pour ces différentes mesures de risque. Nous étudions alors l'impact de la dangerosité des risques et de la dépendance entre les branches sur cette allocation optimale

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Bellot, Benoit. "Améliorer les connaissances sur les processus écologiques régissant les dynamiques de populations d'auxiliaires de culture : modélisation couplant paysages et populations pour l'aide à l'échantillonnage biologique dans l'espace et le temps." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1B008/document.

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Une alternative prometteuse à la lutte chimique pour la régulation des ravageurs de culture consiste à favoriser les populations de leurs prédateurs en jouant sur la structure du paysage agricole. L'identification de structures spatio-temporelles favorables aux ennemis naturels peut se faire par l'exploration de scénarios paysagers via une modélisation couplée de paysages et de dynamiques de population. Dans cette approche, les dynamiques de populations sont simulées sur des paysages virtuels aux propriétés structurales contrôlées, et l'observation des motifs de populations associés permet l'identification de structures favorables. La modélisation des dynamiques de populations repose cependant sur une connaissance fine des processus écologiques et de leur variabilité entre les différentes unités du paysage. L'état actuel des connaissances sur les mécanismes écologiques régissant les dynamiques des ennemis naturels de la famille des carabidés demeure l'obstacle majeur à la recherche in silico de scénarios paysagers favorables. La littérature sur les liens entre motifs de population de carabes et variables paysagères permet de formuler un ensemble d'hypothèses en compétition sur ces mécanismes. Réduire le nombre de ces hypothèses en analysant les convergences entre les motifs de population qui leur sont associés, et étudier la stabilité de ces convergences le long d'un gradient paysager apparaît comme une première étape nécessaire vers l'amélioration de la connaissance sur les processus écologiques. Dans une première partie, nous proposons une heuristique méthodologique basée sur la simulation de modèles de réaction-diffusion porteurs de ces hypothèses en compétition. L'étude des motifs de population a permis d'effectuer une typologie des modèles en fonction de leur réponse à une variable paysagère, via un algorithme de classification, réduisant ainsi le nombre d’hypothèses en compétition. La sélection de l'hypothèse la plus plausible parmi cet ensemble irréductible doit s'effectuer sur la base d'une observation des motifs de population sur le terrain. Cela implique que ces derniers soient caractérisés à des résolutions spatiales et temporelles suffisantes pour sélectionner une unique hypothèse parmi celles en compétition. Dans la deuxième partie, nous proposons une heuristique méthodologique permettant de déterminer a priori des stratégies d'échantillonnage maximisant la robustesse de la sélection d'hypothèses écologiques. Dans un premier temps, la simulation de modèles de réaction-diffusion représentatifs des hypothèses écologiques en compétition permet de générer des données biologiques virtuelles en tout point de l'espace et du temps. Ces données biologiques sont ensuite échantillonnées suivant des protocoles différant dans l'effort total d'échantillonnage, le nombre de dates, le nombre de points par unité d'espace et le nombre de réplicats de paysages. Les motifs des populations sont caractérisés à partir de ces échantillons. Le potentiel des stratégies d'échantillonnage est évalué via un algorithme de classification qui classe les modèles biologiques selon les motifs de population associés. L'analyse des performances de classification, i.e. la capacité de l'algorithme à discriminer les processus écologiques, permet de sélectionner un protocole d'échantillonnage optimal. Nous montrons également que la manière de distribuer l'effort d'échantillonnage entre ses composantes spatiales et temporelles est un levier majeur sur l'inférence des processus écologiques. La réduction du nombre d'hypothèses en compétition et l'aide à l'échantillonnage pour la sélection de modèles répondent à un besoin fort dans le processus d'acquisition de connaissances écologiques pour l'exploration in silico de scénarios paysagers favorisant des services écosystémiques. Nous discutons dans une dernière partie des implications de nos travaux et de leurs perspectives d'amélioration
A promising alternative to the chemical control of pests consists in favoring their natural enemies populations by managing the agricultural landscape structure. Identifying favorable spatio-temporal structures can be performed through the exploration of landscape scenarios using coupled models of landscapes and population dynamics. In this approach, population dynamics are simulated on virtual landscapes with controlled properties, and the observation of population patterns allows for the identification of favorable structures. Population modeling however relies on a good knowledge about the ecological processes and their variability within the landscape elements. Current state of knowledge about the ecological mechanisms underlying natural enemies’ of the carabid family population dynamics remains a major obstacle to in silico investigation of favorable landscape scenarios. Literature about the relationship between carabid population and landscape properties allows the formulation of competing hypotheses about these processes. Reducing the number of these hypotheses by analyzing the convergence between their associated population patterns and investigating the stability of their convergence along a landscape gradient appears to be a necessary tep towards a better knowledge about ecological processes. In a first step, we propose a heuristic method based on the simulation of reaction-diffusion models carrying these competing hypotheses. Comparing the population patterns allowed to set a model typology according to their response to the landscape variable, through a classification algorithm, thus reducing the initial number of competing hypotheses. The selection of the most likely hypothesis from this irreducible set must rely on the observation of population patterns on the field. This implies that population patterns are described with spatial and temporal resolutions that are fine enough to select a unique hypothesis among the ones in competition. In the second part, we propose a heuristic method that allows determining a priori sampling strategies that maximize the robustness of ecological hypotheses selection. The simulation of reaction-diffusion models carrying the ecological hypotheses allows to generate virtual population data in space and time. These data are then sampled using strategies differing in the total effort, number of sampling locations, dates and landscape replicates. Population patterns are described from these samples. The sampling strategies are assessed through a classification algorithm that classifies the models according to the associated patterns. The analysis of classification performances, i.e. the ability of the algorithm to discriminate the ecological processes, allows the selection of optimal sampling designs. We also show that the way the sampling effort is distributed between its spatial and temporal components is strongly impacting the ecological processes inference. Reducing the number of competing ecological hypotheses, along with the selection of sampling strategies for optimal model inference both meet a strong need in the process of knowledge improvement about the ecological processes for the exploration of landscape scenarios favoring ecosystem services. In the last chapter, we discuss the implications and future prospects of our work

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33

Schweizer, Nina Nicole. "Spatio-temporal control of mitotic fidelity by the Spindle Matrix." Doctoral thesis, 2015. https://repositorio-aberto.up.pt/handle/10216/100926.

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Schweizer, Nina Nicole. "Spatio-temporal control of mitotic fidelity by the Spindle Matrix." Tese, 2015. https://repositorio-aberto.up.pt/handle/10216/100926.

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Chitzanidi, Ioanna [Verfasser]. "Control of noise-induced spatio-temporal dynamics in superlattices / von Ioanna Chitzanidi." 2008. http://d-nb.info/987923145/34.

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Lan, Xiaodong. "Learning and monitoring of spatio-temporal fields with sensing robots." Thesis, 2015. https://hdl.handle.net/2144/13640.

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This thesis proposes new algorithms for a group of sensing robots to learn a para- metric model for a dynamic spatio-temporal field, then based on the learned model trajectories are planned for sensing robots to best estimate the field. In this thesis we call these two parts learning and monitoring, respectively. For the learning, we first introduce a parametric model for the spatio-temporal field. We then propose a family of motion strategies that can be used by a group of mobile sensing robots to collect point measurements about the field. Our motion strategies are designed to collect enough information from enough locations at enough different times for the robots to learn the dynamics of the field. In conjunction with these motion strategies, we propose a new learning algorithm based on subspace identification to learn the parameters of the dynamical model. We prove that as the number of data collected by the robots goes to infinity, the parameters learned by our algorithm will converge to the true parameters. For the monitoring, based on the model learned from the learning part, three new informative trajectory planning algorithms are proposed for the robots to collect the most informative measurements for estimating the field. Kalman filter is used to calculate the estimate, and to compute the error covariance of the estimate. The goal is to find trajectories for sensing robots that minimize a cost metric on the error covariance matrix. We propose three algorithms to deal with this problem. First, we propose a new randomized path planning algorithm called Rapidly-exploring Random Cycles (RRC) and its variant RRC* to find periodic trajectories for the sensing robots that try to minimize the largest eigenvalue of the error covariance matrix over an infinite horizon. The algorithm is proven to find the minimum infinite horizon cost cycle in a graph, which grows by successively adding random points. Secondly, we apply kinodynamic RRT* to plan continuous trajectories to estimate the field. We formulate the evolution of the estimation error covariance matrix as a differential constraint and propose extended state space and task space sampling to fit this problem into classical RRT* setup. Thirdly, Pontryagin’s Minimum Principle is used to find a set of necessary conditions that must be satisfied by the optimal trajectory to estimate the field. We then consider a real physical spatio-temporal field, the surface water temper- ature in the Caribbean Sea. We first apply the learning algorithm to learn a linear dynamical model for the temperature. Then based on the learned model, RRC and RRC* are used to plan trajectories to estimate the temperature. The estimation performance of RRC and RRC* trajectories significantly outperform the trajectories planned by random search, greedy and receding horizon algorithms.

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Gagic, Vesna. "Agricultural intensification, biological pest control and spatio-temporal changes in food web structure." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-AE38-6.

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Iddrisu, Abdul-Karim. "Bayesian hierarchical spatial and spatio-temporal modeling and mapping of tuberculosis in Kenya." Thesis, 2013. http://hdl.handle.net/10413/10279.

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Global spread of infectious disease threatens the well-being of human, domestic, and wildlife health. A proper understanding of global distribution of these diseases is an important part of disease management and policy making. However, data are subject to complexities by heterogeneity across host classes and space-time epidemic processes [Waller et al., 1997, Hosseini et al., 2006]. The use of frequentist methods in Biostatistics and epidemiology are common and are therefore extensively utilized in answering varied research questions. In this thesis, we proposed the Hierarchical Bayesian approach to study the spatial and the spatio-temporal pattern of tuberculosis in Kenya [Knorr-Held et al., 1998, Knorr-Held, 1999, L opez-Qu lez and Munoz, 2009, Waller et al., 1997, Julian Besag, 1991]. Space and time interaction of risk (ψ[ij]) is an important factor considered in this thesis. The Markov Chain Monte Carlo (MCMC) method via WinBUGS and R packages were used for simulations [Ntzoufras, 2011, Congdon, 2010, David et al., 1995, Gimenez et al., 2009, Brian, 2003], and the Deviance Information Criterion (DIC), proposed by [Spiegelhalter et al., 2002], used for models comparison and selection. Variation in TB risk is observed among Kenya counties and clustering among counties with high TB relative risk (RR). HIV prevalence is identified as the dominant determinant of TB. We found clustering and heterogeneity of risk among high rate counties and the overall TB risk is slightly decreasing from 2002-2009. Interaction of TB relative risk in space and time is found to be increasing among rural counties that share boundaries with urban counties with high TB risk. This is as a result of the ability of models to borrow strength from neighbouring counties, such that near by counties have similar risk. Although the approaches are less than ideal, we hope that our formulations provide a useful stepping stone in the development of spatial and spatio-temporal methodology for the statistical analysis of risk from TB in Kenya.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

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Rai, Mamta. "Spatio-Temporal Control Of Drosophila Indirect Flight Muscle Development And Maintenance By The Transcription Factor Erect Wing." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2525.

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Muscle development involves concerted action of a repertoire of mechanisms governing myoblast proliferation, migration, fusion and differentiation. Subsequently, there are cellular events administrating proper muscle function and maintenance of muscle integrity. Chapter 1 covers what is known about muscle development, building up of mass and maintenance in vertebrates and Drosophila, highlighting the myogenic programs and factors that play a role in them. The formation of vertebrate skeletal muscles can be recapitulated in Drosophila indirect flight muscles (IFMs), making IFMs an interesting model to dissect and understand the mechanisms of muscle development and maintenance. The cellular and developmental events that occur during IFM development have been discussed in detail along with their genetic control which encompasses both cell autonomous and cell non-autonomous mechanisms. The fly resources and tools used for experimentations have been described in Chapter 2. One of the hallmark events during muscle development is myoblast fusion. Myoblasts are kept in undifferentiated state until they fuse through a balanced action of anti-differentiation and pro-differentiation factors. The swarming myoblasts are in semi-differentiated state and just prior to fusion should exit cell cycle to achieve terminal differentiation. The mechanisms of cyclin/CDK complexes and their regulation via CKI (CDK inhibitor) are known in a cell. However, tissue specific factors exerting additional control on molecules that participate in cell cycle have been proposed but have not been shown in vivo. Chapter 3 uncovers a novel role played by the transcription factor, Erect wing (Ewg) in IFM development and patterning. Despite the fact that Ewg is known to express in fusing myoblasts and nuclei of developing IFMs and has long been used as a nuclear marker for IFMs, the mechanism(s) behind Ewg‟s function has remained enigmatic. Historical perspective of Ewg has been presented in Chapter 1. One set of IFMs; dorsal longitudinal muscles (DLMs) require larval templates for their formation and the other set; dorsal ventral muscles (DVMs) form de novo. Chapter 3 shows that Ewg is required in a spatio-temporal fashion to initiate myoblast fusion process. In the absence of Ewg, the number of fusion events in a given time is reduced. In addition de novo fusion is observed in the region of DLM development just like DVM and overall IFM development is delayed resulting in an aberrant adult IFM pattern. Genetic studies undertaken reveal a requirement for Ewg in exerting a temporal control on myoblast fusion. This is achieved by down-regulating Cyclin E levels, as a result of which the myoblasts exit cell cycle at G1/S stage. Through this study the proposal for DLM development and pattern has been put forth as follows: i) appropriate progression of DLM development commences on synchronous exit of myoblasts from cell cycle. This function is facilitated by Ewg expression in fusing myoblasts assisting symmetrical DLM formation in hemithoraces. ii) DLM pattern of six muscles in each hemithorax is dependent on template survival which requires fusion of enough myoblasts and further subsequent fusion events to support the splitting of three larval templates or presumptive DLM. The muscles that develop should preserve their structural integrity for efficient functional output. Muscles perform extensive activities warranting high energy requirements. IFMs are widely utilised for thorax movements that aid flight. IFMs are exclusively oxidative in nature with upto 40% mass contributed by large mitochondria themselves. Chapter 4 describes yet another novel finding for Ewg function in IFM maintenance. Vertebrate homolog of Ewg is nuclear respiratory factor 1 (NRF1) known for its role in mitochondrial biogenesis. This prompted an investigation on the role of Ewg, if any, in mitochondrial function and IFM maintenance. In this chapter, Ewg null adult IFMs are shown to undergo degeneration. Mitochondria in these muscles show rounder and smaller phenotype. Mitochondria morphology is traced throughout Drosophila pupal DLM development and extensive fusion is observed in last one-fourth of pupal phase. In Ewg null condition transcripts of Opa1-like required for inner mitochondrial membrane fusion is found to be absent, suggesting lack of mitochondrial fusion behind the smaller mitochondrial morphology. This emerged as an intriguing problem since Ewg expression follows until sarcomerogenesis (formation of sarcomeres) initiates at mid pupal stage. Developmentally extending Ewg‟s expression beyond mid pupal stage is not observed to increase Opa1-like levels pointing an indirect regulation by Ewg. However, Opa1-like knock-down beyond mid pupal stage is not observed to result in any muscle or flight defect. It is thus proposed that Ewg expression early during muscle development helps to up-regulate Opa1-like levels needed to support mitochondrial growth and fusion. In addition, this chapter provides additional data on requirement of Opa1-like for maintenance of mitochondrial as well as muscle integrity. This is the first ever report of tissue specific temporal regulation of Opa1-like by Ewg. Chapter 3 and Chapter 4 conclude spatially segregated functional requirements of Ewg which are also mechanistically distinct. Expression in fusing myoblasts channelizes fusing myoblasts to exit cell cycle and undergo timely fusion saving the larval template, subsequent fusion assists template splitting thus forming the appropriate adult DLM pattern. On the other hand expression until mid pupal stage up-regulates Opa1-like expression, facilitating mitochondrial fusion during the late pupal stage. This as a result helps maintain structural integrity of muscles in the adult. Vertebrate skeletal muscle contains multiple muscle fibres that provide appropriate mass and size to muscles. As DLM share similarity in development to that of the vertebrate skeletal muscle, DLM organisation is studied to get insights into the mechanisms which regulate the process. Chapter 5 discusses role of nuclear number and nuclear activity in determining the DLM organisation. In order to alter nuclear number, myoblast population is reduced to amounts lesser than that of the wild type and to alter nuclear activity, two nuclear encoded genes Opa1-like and Marf , involved in inner and outer mitochondrial membrane fusion respectively have been knocked down in IFMs. First, the DLM organisation is established by comparing it to the vertebrate skeletal muscle organisation. This organisation is affected on lowering the number of myoblasts destined to fuse and form IFMs, without affecting the differentiation. On the other hand, when nuclear encoded mitochondrial fusion genes are knocked down, not only DLM organisation but their differentiation is also affected. A proposal for achieving DLM organisation has been presented which should also apply to vertebrate skeletal muscle given their developmental similarity. In conclusion, the studies decipher a novel mechanism by which a transcription factor, Ewg exerts a temporal control on myoblast fusions directly influencing progression of DLM formation, and thereby, symmetry and pattern. Moreover, Ewg is also shown here to regulate mitochondrial fusion during later pupal stages helping muscles to attain greater function and maintain structural integrity. Discovery of such regulatory mechanisms controlling mitochondrial dynamics in vertebrates can open up new avenues to understand and design new therapeutic approaches to tackle mitochondrial diseases. Additionally, myoblast fusion and hence myonuclear number and their efficient functioning are shown to be important determinants of muscle organisation. This has further implications in understanding and using stem cell science in dystrophic or atrophic or ageing related muscle loss and therapy.

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40

Roffe, Sarah Jane. "An investigation into the spatio-temporal patterns of modelling SO2, NOx and surface O3 across the Highveld priority area, South Africa." Thesis, 2017. http://hdl.handle.net/10539/23542.

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A thesis submitted to the Faculty of Science, University of the Witwatersrand, in fulfillment of the requirements for the degree of Master of Science. Johannesburg, 2017.
The Highveld is identified as an air pollution ‘hotspot’ area where pollutant concentrations are elevated due to the high density of industrial and non-industrial air pollution sources. To enhance air quality across the Highveld, it was declared a priority area to manage and monitor pollutants to reduce their negative impact on the environment and society. Hence, the aim of this study was to investigate ambient air pollution across the Highveld Priority Area (HPA), using ground-level SO2, NOx and surface O3 concentrations, meteorological parameters and Moderate resolution imaging spectroradiometer (MODIS) atmosphere products, for January to December 2011, to develop new modelling techniques to aid in the management of air pollution. Results show the annual mean trace gas concentrations of SO2, NOx and surface O3 were 12.14, 14.75 and 28.77 ppb, respectively. SO2 and NOx concentrations were highest during winter at an average of 17.56 and 20.96 ppb, where surface O3 concentrations were highest during spring at an average of 32.82 ppb. Diurnal patterns of SO2 and surface O3 were similar, where a midday peak occurred. NOx concentrations instead showed peaks during traffic hours. Ambient air temperature, solar radiation, relative humidity, wind speed and rainfall levels peaked during summer. Atmospheric pressure was relatively stable throughout the year. Winds typically ranged from N to E up to April and from S to NW from May. Very little variation in SO2 and NOx concentrations was explainable by meteorology, 4 to 29 % and 5 to 23 %, while the influence of meteorology on surface O3 concentrations was more significant, 23 to 53 %. Spatial multiple regression statistical models using a cross validation approach for model validation were made over a number of temporal scales. The model fitting and validation processes indicated that the models were not a good fit as only up to 69, 74 and 58 % of SO2, NOx and surface O3 concentrations with high root means square error (RMSE) values of up to 22.10, 15.56 and 18.59 ppb, respectively, could be explained by the models. This process revealed the potential to model pollutants across the HPA, and as a pilot study future work can be based on this study. It is clear that spatial modelling for pollution estimation and management is necessary as seen by the frequent exceedances of the national and international ambient air quality standards.
XL2017

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41

Bader, Benjamin M. [Verfasser]. "Spatio-temporal control of Wnt-β-catenin [Wnt-beta-catenin] signaling during fate commitment of human neural progenitor cells / vorgelegt von: Benjamin Bader". 2010. http://d-nb.info/1010575481/34.

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42

Gölling, Burkhard. "Experimentelle Untersuchungen des laminar-turbulenten Überganges der Zylindergrenzschichtströmung." Doctoral thesis, 2001. http://hdl.handle.net/11858/00-1735-0000-0006-B5AF-5.

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43

Joshi, Champa. "Understanding Spatio-Temporal Variability and Associated Physical Controls of Near-Surface Soil Moisture in Different Hydro-Climates." Thesis, 2013. http://hdl.handle.net/1969.1/149547.

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Near-surface soil moisture is a key state variable of the hydrologic cycle and plays a significant role in the global water and energy balance by affecting several hydrological, ecological, meteorological, geomorphologic, and other natural processes in the land-atmosphere continuum. Presence of soil moisture in the root zone is vital for the crop and plant life cycle. Soil moisture distribution is highly non-linear across time and space. Various geophysical factors (e.g., soil properties, topography, vegetation, and weather/climate) and their interactions control the spatio-temporal evolution of soil moisture at various scales. Understanding these interactions is crucial for the characterization of soil moisture dynamics occurring in the vadose zone. This dissertation focuses on understanding the spatio-temporal variability of near-surface soil moisture and the associated physical control(s) across varying measurement support (point-scale and passive microwave airborne/satellite remote sensing footprint-scale), spatial extents (field-, watershed-, and regional-scale), and changing hydro-climates. Various analysis techniques (e.g., time stability, geostatistics, Empirical Orthogonal Function, and Singular Value Decomposition) have been employed to characterize near-surface soil moisture variability and the role of contributing physical control(s) across space and time. Findings of this study can be helpful in several hydrological research/applications, such as, validation/calibration and downscaling of remote sensing data products, planning and designing effective soil moisture monitoring networks and field campaigns, improving performance of soil moisture retrieval algorithm, flood/drought prediction, climate forecast modeling, and agricultural management practices.

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44

Specht, Sebastian [Verfasser]. "The small heat shock protein Hsp42 controls the spatio-temporal organization of aggregated proteins in Saccharomyces cerevisiae / presented by Sebastian Specht." 2010. http://d-nb.info/1005444811/34.

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