Light and temperature are two of the most important non-biological signals that plants must be able to sense and respond to. However, it is not just the individual signals, but the interaction between them that is important. In the dark, Arabidopsis has strongly reduced temperature plasticity. The red light photoreceptor phyB and the PIF family of transcription factors have previously been identified as key regulators of this response. Computer modelling was used to study the interaction between the proteins, to explain counter-intuitive behaviour at certain light conditions. A fluence rate dependent response to temperature was uncovered, where high temperature causes a reversal of the normal seedling response to light. In a PIF and phyB dependent manner, increasing light intensity in the warm can lead to an increase in hypocotyl elongation, the opposite of what has been previously published. This was shown to be dependent on an apically derived response to high fluence rates, independent of the Phytochromes. To extend the analysis beyond the seedling stage, the adult phenotypes of light signalling mutants were subsequently characterised at different temperatures. The temperature dependent control of flowering time and leaf growth were both dependent on Phytochrome and the PIFs, but in apparent opposite directions. This demonstrates that the light signalling system in plants is a complex network of signalling factors, affecting each other in a dynamic process to respond to light and temperature.

Increased efficacy of light and laser applications in medicine is achieved by accurate light dosimetry. A minimally invasive technique for the determination of the optical coefficients of tissue involves interstitial measurements of the local fluence rate at two or more points in the tissue using isotropic, fibre optic detectors and application of a diffusion model of light propagation. The diffusion models assume simple, homogeneous tissue geometries, possibly oversimplifying the effect of tissue heterogeneities and boundaries. The primary goals of this study were to investigate the influence of realistic finite geometries on the fluence rate distribution and to quantify the systematic errors in the derived optical properties. A Monte Carlo model was developed to predict the fluence rate distribution in any plane of interest in a medium and was verified by comparison with diffusion theory solutions for simple geometries. Fluence rate measurements were made in optically infinite and semi-infinite phantoms for a wide range of optical properties and it was determined that the optical coefficients were derived accurately for phantoms with ueff> 0.2 mm-1 and 2 < ut'<10 mm-1. Measurements were also made in finite spherical volumes with absorbing (Rd = 0.35) and diffuse reflecting (Rd =0.85) boundaries for three optical phantoms and comparisons of the experimental fluence rates with the predictions of the finite volume Monte Carlo model are presented. Boundary effects were observed to be significant within 4 transport mean free paths (mfp') of the boundary. The optical coefficients were derived by applying a diffusion solution for an infinite medium and it was determined that within 2 mfp' of the boundary, the derived ua was overestimated by 40% and underestimated by 20% for the absorbing and reflecting boundaries, respectively. / Thesis / Master of Science (MS)

Die vorliegende Studie untersucht mittels eines Diodenlaser (808 nm) zur axillären Epilation, inwieweit eine Reduktion der applizierten Einzelenergie mit angepasster Pulsdauer und repetitiver Pulszahl (Low-Fluence) eine Verträglichkeitssteigerung, bei gleichzeitigem Erhalt der Epilationseffektivität, wie er von traditionelle High-Fluence Applikationen bekannt ist, bewirken kann. Es wurden die Axillae von 21 Patienten des Hauttyps eins bis drei nach zwei unterschiedlichen Protokollen im vierwöchigen Intervall behandelt. Auf der linken Seite erfolgte die Therapie sechsmalig mittels Low-Fluence, wohingegen auf der rechten Seite eine Kombination von dreimalig Low-Fluence- und dreimalig High-Fluence-Modus appliziert wurde. Es konnte hinsichtlich der Effektivität kein statistisch signifikanter Unterschied zwischen beiden Behandlungsmethoden nachgewiesen werden. Die Reduktion zeigte sich konstant und lag am Ende der 24-monatigen Gesamtstudiendauer im Mittel bei 45%. Die Ergebnisse stellen sich damit schlechter dar, als bei konventionellen Studien im High-Fluence-Bereich oder anderen Low-Fluence-Konzepten. Als Ursache ist am ehesten eine unzureichende Einzelimpulsdauer und eine zu gering gewählte Pulswiederholungsanzahl zu sehen. Andererseits ergab sich eine deutliche Verträglichkeitssteigerung, vor allem hinsichtlich des Schmerzempfindens und im Auftreten von Pigmentierungsstörungen zu Gunsten der Low-Fluence-Therapie.

Le spectre des neutrons prompts de fission (PFNS) est une donnée très importante pour diverses applications de la physique nucléaire. Cependant, en dehors du spectre de la fission spontanée du 252Cf, qui est reconnu comme un standard international et est utilisé pour la métrologie, le PFNS reste mal connu pour la plupart des noyaux fissionnants. En particulier, pour la fission rapide (induite par un neutron de plus de 100 keV environ), il existe peu de mesures, et les évaluations internationales présentent de fortes contradictions. De plus, il existe très peu de données sur les covariances associées aux diverses évaluations du spectre. Dans cette thèse, trois aspects de l'évaluation du PFNS sont abordés. Le premier aspect est la modélisation du spectre via le code FIFRELIN, développé au CEA Cadarache, qui simule la chaine de désexcitation des fragments de fission par émissions successives de neutrons et gammas prompts par la méthode de Monte-Carlo. Ce code a pour vocation de calculer les observables de fission dans un même calcul cohérent, à partir des distributions en masse, en énergie cinétique et en spin des fragments de fission. FIFRELIN a donc un caractère prédictif que n'ont pas les modèles analytiques utilisés pour décrire le PFNS. Une étude des paramètres de modèle influents, notamment le paramètre de densité de niveaux, est mené afin de tenter de mieux reproduire le spectre. Le deuxième aspect de la thèse concerne l'évaluation du PFNS et de sa matrice de covariance. On propose une méthodologie pour évaluer le spectre et sa matrice de covariance de manière rigoureuse, à travers l'outil CONRAD du CEA Cadarache. Ceci implique la modélisation du spectre à travers des modèles simples, notamment celui de Madland-Nix qui est le plus utilisé dans les évaluations, en ajustant les paramètres de ces modèles afin de reproduire les données expérimentales. La matrice de covariance provient de la propagation rigoureuse des sources d'incertitude qui interviennent dans le calcul. En particulier, les incertitudes systématiques liées au dispositif expérimental sont propagées par des techniques de marginalisation. La marginalisation permet de propager ces incertitudes sur le spectre calculé, en obtenant des incertitudes réalistes sans besoin d'être artificiellement rehaussées comme c'est souvent le cas dans le cadre d'ajustements bayésiens. La propagation de ces incertitudes expérimentales impacte aussi la matrice de corrélation du spectre calculé. On présente les résultats pour la fission induite par neutron thermique de l'235U et du 239Pu. Pour le modèle de Madland-Nix avec section inverse constante, l'énergie moyenne des neutrons prompts obtenue est de 1.979 MeV pour l'235U, et de 2.087 MeV pour le 239Pu. Le dernier aspect de la thèse est l'étude de l'impact du PFNS et de ses covariances sur le calcul du flux neutronique sur la cuve d'un réacteur. L'enjeu est de taille, car l'estimation de la fluence au niveau de la cuve d'un réacteur détermine l'intégrité de celle-ci, et donc la durée de vie du réacteur. On observe l'importance des termes de corrélations du spectre pour calculer notamment l'incertitude sur le flux intégré au-dessus de 1 MeV, de l'ordre de 6% (incertitude due seulement au spectre). / The prompt fission neutron spectrum (PFNS) is very important for various nuclear physics applications. Yet, except for the 252Cf spontaneous fission spectrum which is an international standard and is used for metrology purposes, the PFNS is still poorly known for most of the fissionning nuclides. In particular, few measurements exist for the fast fission spectrum (induced by a neutron whose energy exceeds about 100 keV), and the international evaluations show strong discrepancies. There are also very few data about covariances associated to the various PFNS evaluations. In this work we present three aspects of the PFNS evaluation. The first aspect is about the spectrum modeling with the FIFRELIN code, developed at CEA Cadarache, which simulates the fission fragment de-excitation by successive emissions of prompt neutrons and gammas, via the Monte-Carlo method. This code aims at calculating all fission observables in a single consistent calculation, starting from fission fragment distributions (mass, kinetic energy and spin). FIFRELIN is therefore more predictive than the analytical models used to describe the spectrum. A study of model parameters which impact the spectrum, like the fragment level density parameter, is presented in order to better reproduce the spectrum. The second aspect of this work is about the evaluation of the PFNS and its covariance matrix. We present a methodology to produce this evaluation in a rigorous way, with the CONRAD code, developed at CEA Cadarache. This implies modeling the spectrum through simple models, like the Madland-Nix model which is the most commonly used in the evaluations, by adjusting the model parameters to reproduce experimental data. The covariance matrix arises from the rigorous propagation of the sources of uncertainty involved in the calculation. In particular, the systematic uncertainties arising from the experimental set-up are propagated via a marginalization technique. The marginalization allows propagating these uncertainties on the calculated spectrum, and obtaining realistic uncertainties without having to artificially raise them, as it is sometimes necessary in Bayesian adjustments. The experimental uncertainty propagation also impacts the spectrum correlation matrix. We present the result for thermal neutron-induced fission of 235U and 239Pu. For the Madland-Nix model with constant inverse cross-section, the prompt neutron mean energy is 1.979 MeV for 235U and 2.087 MeV for 239Pu. The last aspect of this work is the calculation of the impact of the PFNS and its covariance matrix on a reactor vessel flux. This calculation is of major importance, since the vessel fluence estimation determines the vessel integrity, and therefore determines the reactor lifetime. We observe the importance of the PFNS correlation terms, to compute in particular the vessel flux uncertainty above 1 MeV, which is of the order of 6% (uncertainty only due to PFNS).

>Magister Scientiae - MSc / A (5 cm × 5 cm) cylindrical NE213 liquid organic scintillator and a (2.5 cm × 2.5 cm)cylindrical NE230 liquid organic scintillator were used as spectrometers. A series of measurements was made with both the NE213 and NE230 spectrometers, with the time-of- flight technique used for neutron energy selection. Pulse height spectra for quasi- monoenergetic neutron beams of ~5-64 MeV produced by bombarding either a (1 mm) lithium metal target, or a (10 mm) beryllium target, or a (10 mm) graphite target with 66 MeV proton beam were measured with both spectrometers. Deuteron events identified by pulse shape discrimination were selected for measurements with the NE230 spectrometer while proton events were selected for measurements with the NE213 spectrometer. Response of the scintillator to protons using NE213 and deuterons using NE230 were obtained from the measured pulse height spectra. Detector efficiency of the NE213 spectrometer as a function of neutron energy was determined for n-p elastic scattering. The detector efficiency of the NE230 was determined relative to the well-known efficiency of the NE213 spectrometer, selecting either all or n-d elastic events in the pulse height spectra measured with the NE230 spectrometer. The detection efficiency of the NE230 spectrometer was also determined from the available cross-section for n-d elastic scattering as exploratory work. Neutron fluence spectra could be determined using the appropriate neutron detection efficiency for each spectrometer and were compared with each other. The results showed good comparison and encouragement demonstrating the reliability of neutron fluence spectral measurements withthe NE230 spectrometer using the time-of-flight technique.

Il existe aujourd’hui un large consensus sur le fait que le système cognitif est capabled’avoir des activités sur lui-même, on parle de métacognition. Si plusieurs travaux se sontintéressés aux mécanismes qui sous-tendent cette métacognition, à notre connaissance,aucun ne l’a fait dans une perspective « sensorimotrice et intégrative » du fonctionne-ment cognitif comme celle que nous proposons. Ainsi, la thèse que nous défendons dansce travail est la suivante : l’information métacognitive, notamment la fluence, possèdestrictement le même statut que l’information cognitive (i.e., sensorielle et motrice). Dansun premier chapitre, nous proposons un modèle de la cognition respectant ce principe.Ensuite, dans les deux chapitres suivants, nous mettons à l’épreuve notre hypothèse parle biais d’expériences et de simulations effectuées à l’aide du modèle mathématique quenous avons élaboré. Ces travaux ont porté plus précisément sur des phénomènes liés à troispossibilités originales prédites par notre hypothèse : la possibilité de méta-métacognition,la possibilité d’intégration entre information sensorielle et information métacognitive, etla possibilité d’abstraction métacognitive. / There is today a broad consensus that the cognitive system is capable of having acti-vities on itself, we are talking about metacognition. Although several studies have focusedon the mechanisms underlying this metacognition, to our knowledge, none has done so ina "sensorimotor and integrative" perspective of cognitive functioning such as the one wepropose. Thus, the thesis we defend in this work is the following : metacognitive infor-mation, especially fluency, has strictly the same status as any cognitive information (i.e.,sensory and motor). In a first chapter, we propose a model of cognition respecting thisprinciple. Then, in the next two chapters, we test our hypothesis through experimentsand simulations using the mathematical model we have developed. This work focusedmore specifically on phenomena related to three original possibilities predicted by ourhypothesis : the possibility of meta-metacognition, the possibility of integration betweensensory information and metacognitive information, and the possibility of metacognitiveabstraction.

In this work we introduce PARETO, a multiobjective optimization tool that simultaneously optimizes beam angles and fluence patterns in intensity-modulated radiation therapy (IMRT) treatment planning using a powerful genetic algorithm. We also investigate various objective functions and compare several parameterizations for modeling beam fluence in terms of fluence map complexity, solution quality, and run efficiency. We have found that the combination of a conformity-based Planning Target Volume (PTV) objective function and a dose-volume histogram or equivalent uniform dose -based objective function for Organs-At-Risk (OARs) produced relatively uniform and conformal PTV doses, with well-spaced beams. For two patient data sets, the linear gradient and beam group fluence parameterizations produced superior solution quality using a moderate and high degree of modulation, respectively, and had comparable run times. PARETO promises to improve the accuracy and efficiency of treatment planning by fully automating the optimization and producing a database of non-dominated solutions for each patient.

In this work we introduce PARETO, a multiobjective optimization tool that simultaneously optimizes beam angles and fluence patterns in intensity-modulated radiation therapy (IMRT) treatment planning using a powerful genetic algorithm. We also investigate various objective functions and compare several parameterizations for modeling beam fluence in terms of fluence map complexity, solution quality, and run efficiency. We have found that the combination of a conformity-based Planning Target Volume (PTV) objective function and a dose-volume histogram or equivalent uniform dose -based objective function for Organs-At-Risk (OARs) produced relatively uniform and conformal PTV doses, with well-spaced beams. For two patient data sets, the linear gradient and beam group fluence parameterizations produced superior solution quality using a moderate and high degree of modulation, respectively, and had comparable run times. PARETO promises to improve the accuracy and efficiency of treatment planning by fully automating the optimization and producing a database of non-dominated solutions for each patient.

No description available.

Die vorliegende Studie untersucht mittels eines Diodenlaser (808 nm) zur axillären Epilation, inwieweit eine Reduktion der applizierten Einzelenergie mit angepasster Pulsdauer und repetitiver Pulszahl (Low-Fluence) eine Verträglichkeitssteigerung, bei gleichzeitigem Erhalt der Epilationseffektivität, wie er von traditionelle High-Fluence Applikationen bekannt ist, bewirken kann. Es wurden die Axillae von 21 Patienten des Hauttyps eins bis drei nach zwei unterschiedlichen Protokollen im vierwöchigen Intervall behandelt. Auf der linken Seite erfolgte die Therapie sechsmalig mittels Low-Fluence, wohingegen auf der rechten Seite eine Kombination von dreimalig Low-Fluence- und dreimalig High-Fluence-Modus appliziert wurde. Es konnte hinsichtlich der Effektivität kein statistisch signifikanter Unterschied zwischen beiden Behandlungsmethoden nachgewiesen werden. Die Reduktion zeigte sich konstant und lag am Ende der 24-monatigen Gesamtstudiendauer im Mittel bei 45%. Die Ergebnisse stellen sich damit schlechter dar, als bei konventionellen Studien im High-Fluence-Bereich oder anderen Low-Fluence-Konzepten. Als Ursache ist am ehesten eine unzureichende Einzelimpulsdauer und eine zu gering gewählte Pulswiederholungsanzahl zu sehen. Andererseits ergab sich eine deutliche Verträglichkeitssteigerung, vor allem hinsichtlich des Schmerzempfindens und im Auftreten von Pigmentierungsstörungen zu Gunsten der Low-Fluence-Therapie.