The role of initial density profiles in simulations of coronal wave - coronal hole interaction

Interactions between global coronal waves (CWs) and coronal holes (CHs) reveal many interesting features of reflected waves and coronal hole boundaries (CHB) but have fairly been studied so far. Magnetohydrodynamic (MHD) simulations can help us to better understand what is happening during these interaction events, and therefore, to achieve a broader understanding of the parameters involved. In this study, we perform for the first time 2D MHD simulations of a CW-CH interaction including a realistic initial wave density profile that consists of an enhanced as well as a depleted wave part. We vary several initial parameters, such as the initial density amplitudes of the incoming wave, the CH density, and the CHB width, which are all based on actual measurements. We analyse the effects of different incident angles on the interaction features and we use the corresponding time-distance plots to detect specific features of the incoming and the reflected wave. We found that a particular combination of a small CH density, a realistic initial density profile and a sufficiently small incident angle leads to remarkable interaction features, such as a large density amplitude of the reflected wave with respect to the incoming one. The parameter studies in this paper provide a tool to compare time-distance plots based on observational measurements to those created from simulations and therefore enable us to derive interaction parameters from observed CW-CH interaction events that usually cannot be obtained directly. The simulation results in this study are augmented by analytical expressions for the reflection coefficient of the CW-CH interaction which allows us to verify the simulations results in an additional way. This work is the first of a series of studies aiming to finally reconstruct actual observed CW-CH interaction events by means of MHD-simulations

The effects of acute tryptophan depletion on costly information sampling: impulsivity or aversive processing?

RATIONALE: The neurotransmitter serotonin (5-HT) has been implicated in both aversive processing and impulsivity. Reconciling these accounts, recent studies have demonstrated that 5-HT is important for punishment-induced behavioural inhibition. These studies focused on situations where actions lead directly to punishments. However, decision-making often involves making tradeoffs between small 'local' costs and larger 'global' losses. OBJECTIVE: We aimed to distinguish whether 5-HT promotes avoidance of local losses, global losses, or both, in contrast to an overall effect on reflection impulsivity. We further examined the influence of individual differences in sub-clinical depression, anxiety and impulsivity on global and local loss avoidance. METHODS: Healthy volunteers (N = 21) underwent an acute tryptophan depletion procedure in a double-blind, placebo-controlled crossover design. We measured global and local loss avoidance in a decision-making task where subjects could sample information at a small cost to avoid making incorrect decisions, which resulted in large losses. RESULTS: Tryptophan depletion removed the suppressive effects of small local costs on information sampling behaviour. Sub-clinical depressive symptoms produced effects on information sampling similar to (but independent from) those of tryptophan depletion. Dispositional anxiety was related to global loss avoidance. However, trait impulsivity was unrelated to information sampling. CONCLUSIONS: The current findings are consistent with recent theoretical work that characterises 5-HT as pruning a tree of potential decisions, eliminating options expected to lead to aversive outcomes. Our results extend this account by proposing that 5-HT promotes reflexive avoidance of relatively immediate aversive outcomes, potentially at the expense of more globally construed future losses

An effect of serotonergic stimulation on learning rates for rewards apparent after long intertrial intervals

Serotonin has widespread, but computationally obscure, modulatory effects on learning and cognition. Here, we studied the impact of optogenetic stimulation of dorsal raphe serotonin neurons in mice performing a non-stationary, reward-driven decision-making task. Animals showed two distinct choice strategies. Choices after short inter-trial-intervals (ITIs) depended only on the last trial outcome and followed a win-stay-lose-switch pattern. In contrast, choices after long ITIs reflected outcome history over multiple trials, as described by reinforcement learning models. We found that optogenetic stimulation during a trial significantly boosted the rate of learning that occurred due to the outcome of that trial, but these effects were only exhibited on choices after long ITIs. This suggests that serotonin neurons modulate reinforcement learning rates, and that this influence is masked by alternate, unaffected, decision mechanisms. These results provide insight into the role of serotonin in treating psychiatric disorders, particularly its modulation of neural plasticity and learning.info:eu-repo/semantics/publishedVersio

Euclid preparation: XIII. Forecasts for galaxy morphology with the Euclid Survey using deep generative models

We present a machine learning framework to simulate realistic galaxies for the Euclid Survey, producing more complex and realistic galaxies than the analytical simulations currently used in Euclid. The proposed method combines a control on galaxy shape parameters offered by analytic models with realistic surface brightness distributions learned from real Hubble Space Telescope observations by deep generative models. We simulate a galaxy field of 0.4 deg2 as it will be seen by the Euclid visible imager VIS, and we show that galaxy structural parameters are recovered to an accuracy similar to that for pure analytic Sérsic profiles. Based on these simulations, we estimate that the Euclid Wide Survey (EWS) will be able to resolve the internal morphological structure of galaxies down to a surface brightness of 22.5 mag arcsec-2, and the Euclid Deep Survey (EDS) down to 24.9 mag arcsec-2. This corresponds to approximately 250 million galaxies at the end of the mission and a 50% complete sample for stellar masses above 1010.6 M (resp. 109.6 M) at a redshift z ∼ 0.5 for the EWS (resp. EDS). The approach presented in this work can contribute to improving the preparation of future high-precision cosmological imaging surveys by allowing simulations to incorporate more realistic galaxies

Euclid preparation XIII. Forecasts for galaxy morphology with the Euclid Survey using deep generative models

We present a machine learning framework to simulate realistic galaxies for the Euclid Survey, producing more complex and realistic galaxies than the analytical simulations currently used in Euclid. The proposed method combines a control on galaxy shape parameters offered by analytic models with realistic surface brightness distributions learned from real Hubble Space Telescope observations by deep generative models. We simulate a galaxy field of 0.4 deg2 as it will be seen by the Euclid visible imager VIS, and we show that galaxy structural parameters are recovered to an accuracy similar to that for pure analytic Sérsic profiles. Based on these simulations, we estimate that the Euclid Wide Survey (EWS) will be able to resolve the internal morphological structure of galaxies down to a surface brightness of 22.5 mag arcsec−2, and the Euclid Deep Survey (EDS) down to 24.9 mag arcsec−2. This corresponds to approximately 250 million galaxies at the end of the mission and a 50% complete sample for stellar masses above 1010.6 M⊙ (resp. 109.6 M⊙) at a redshift z ∼ 0.5 for the EWS (resp. EDS). The approach presented in this work can contribute to improving the preparation of future high-precision cosmological imaging surveys by allowing simulations to incorporate more realistic galaxies

Prise en compte de l'ionisation et du rayonnement dans la modélisation des écoulements de rentrée terrestre et martienne

Ce travail porte sur la simulation numérique des écoulements de rentrée martienne et terrestre. Parmi les phénomènes physico-chimiques complexes mis en jeu, les points abordés concernent plus particulièrement l'ionisation du gaz dans la couche de choc et l'effet du rayonnement sur les flux thermiques pariétaux. Le traitement de l'ionisation repose sur l'approche de Coquel-Marmignon permettant d écrire le système d équations sous forme conservative. L'approche numérique est basée sur le schéma de Roe et elle est validée sur trois cas d'épreuve pour des vitesses allant jusqu à 11km/s. Un schéma de relaxation, plus simple de mise en œuvre et mieux adapté, est également proposé. Le traitement du rayonnement dépend du cas d application. Pour les applications terrestres, le modèle de propriétés radiatives est de type raie-par-raie et la méthode de résolution de l'équation de transfert radiatif est la méthode des plans tangente. Les champs hydrodynamique et radiatif sont couplés par une méthode itérative. La comparaison avec les mesures en vol de la campagne FIRE II montre que l'approche est satisfaisante, excepté lorsque l'approximation liée aux plans tangente n est plus valable (faible rayon de nez, loin de la région d arrêt). Au point d arrêt, le rayonnement participe jusqu'à 40% à l'échauffement pariétal. Pour les applications martiennes, le modèle de propriétés radiatives, limité aux contributions des espèces CO et CO[indice 2] dans l'infrarouge, est de type statistique à bandes étroites et la méthode numérique de type Monte Carlo. La méthode de couplage hydrodynamique/rayonnement est similaire au cas terrestre. Les calculs, menés sur un véhicule générique typique de la mission Mars Premier, montrent qu au niveau de l'arrière-corps, le rayonnement contribue de manière signi cative à l'échauffement pariétal.TOULOUSE-ISAE (315552318) / SudocSudocFranceF

Actualité bibliographique en échographie du tractus digestif chez le chien et le chat

Cette thèse dresse un bilan des données bibliographiques publiées durant ces dix dernières années en ce qui concerne l échographie du tractus digestif des carnivores domestiques (chiens et chats). Elle débute par un bref rappel des principes de base nécessaires à la réalisation de cet examen. Elle présente ensuite une analyse critique des publications récentes faisant référence à l aspect échographique normal du tractus digestif. Les articles concernant les pathologies digestives et les modifications échographiques qu elles engendrent sont abordés dans un deuxième temps. Enfin, la dernière partie de ce travail porte sur l intérêt diagnostique et les limites de l échographie, en comparaison aux autres techniques d imagerie actuellement à la disposition du vétérinaire praticien (radiographie, tomodensitométrie).TOULOUSE-EN Vétérinaire (315552301) / SudocTOULOUSE3-BU Santé-Centrale (315552105) / SudocSudocFranceF

Apprendre à lire grâce à l'hypertexte

MONTPELLIER-BU Lettres (341722103) / SudocSudocFranceF

La croissance mandibulaire (données de la littérature et réalités cliniques)

MONTROUGE-BUFR Odontol.PARIS5 (920492101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF