Corticosterone and foraging behaviour in a pelagic seabird

Because endocrine mechanisms are thought to mediate behavioral responses to changes in the environment, examining these mechanisms is essential for understanding how long-lived seabirds adjust their foraging decisions to contrasting environmental conditions in order to maximize their fitness. In this context, the hormone corticosterone (CORT) deserves specific attention because of its major connections with locomotor activities. We examined for the first time the relationships between individual CORT levels and measurements of foraging success and behavior using satellite tracking and blood sampling from wandering albatrosses (Diomedea exulans) before (pretrip CORT levels) and after (posttrip CORT levels) foraging trips during the incubation period. Plasma CORT levels decreased after a foraging trip, and the level of posttrip CORT was negatively correlated with individual foraging success, calculated as total mass gain over a foraging trip. Pretrip CORT levels were not linked to time spent at sea but were positively correlated with daily distance traveled and maximum range at sea. In this study, we were able to highlight the sensitivity of CORT levels to variation in energy intake, and we showed for the first time that individual CORT levels can be explained by variation in foraging success. Relationships between pretrip CORT levels and daily distance traveled and maximum range were independent of pretrip body mass, suggesting that slight elevations in pretrip CORT levels might facilitate locomotor activity. However, because both foraging behavior and pretrip CORT levels could be affected by individual quality, future experimental studies including manipulation of CORT levels are needed to test whether CORT can mediate foraging decisions according to foraging conditions

Development of High Fidelity Soot Aerosol Dynamics Models using Method of Moments with Interpolative Closure

The method of moments with interpolative closure (MOMIC) for soot formation and growth provides a detailed modeling framework maintaining a good balance in generality, accuracy, robustness, and computational efficiency. This study presents several computational issues in the development and implementation of the MOMIC-based soot modeling for direct numerical simulations (DNS). The issues of concern include a wide dynamic range of numbers, choice of normalization, high effective Schmidt number of soot particles, and realizability of the soot particle size distribution function (PSDF). These problems are not unique to DNS, but they are often exacerbated by the high-order numerical schemes used in DNS. Four specific issues are discussed in this article: the treatment of soot diffusion, choice of interpolation scheme for MOMIC, an approach to deal with strongly oxidizing environments, and realizability of the PSDF. General, robust, and stable approaches are sought to address these issues, minimizing the use of ad hoc treatments such as clipping. The solutions proposed and demonstrated here are being applied to generate new physical insight into complex turbulence-chemistry-soot-radiation interactions in turbulent reacting flows using DNS

Alcohol-induced damage to the fimbria/fornix reduces hippocampal-prefrontal cortex connection during early abstinence

[EN] IntroductionAlcohol dependence is characterized by a gradual reduction in cognitive control and inflexibility to contingency changes. The neuroadaptations underlying this aberrant behavior are poorly understood. Using an animal model of alcohol use disorders (AUD) and complementing diffusion-weighted (dw)-MRI with quantitative immunohistochemistry and electrophysiological recordings, we provide causal evidence that chronic intermittent alcohol exposure affects the microstructural integrity of the fimbria/fornix, decreasing myelin basic protein content, and reducing the effective communication from the hippocampus (HC) to the prefrontal cortex (PFC). Using a simple quantitative neural network model, we show how disturbed HC-PFC communication may impede the extinction of maladaptive memories, decreasing flexibility. Finally, combining dw-MRI and psychometric data in AUD patients, we discovered an association between the magnitude of microstructural alteration in the fimbria/fornix and the reduction in cognitive flexibility. Overall, these findings highlight the vulnerability of the fimbria/fornix microstructure in AUD and its potential contribution to alcohol pathophysiology.Fimbria vulnerability to alcohol underlies hippocampal-prefrontal cortex dysfunction and correlates with cognitive impairment.The authors acknowledge funding from the European Union Horizon 2020 research and innovation program under Grant Agreement No. 668863 (SyBil-AA), and the Spanish Ministerio de Ciencia e Innovación, Agencia Estatal de Investigación (PID2021-128158NB-C21 [to S.C.] and PID2021-128909NA-I00 [to S.D.S.]) and Programs for Centres of Excellence in R&D Severo Ochoa (CEX2021-001165-S [to S.C. and S.D.S.]), the Spanish Generalitat Valenciana Government (PROMETEO/2019/015 [to SC] and CIDEGENT/2021/015 [to SDS]), the Spanish Ministerio de Sanidad, Servicios Sociales e Igualdad (#2021I082). W.H.S., F.K. and P.K. further acknowledge funding by the Deutsche Forschungs Gesellschaft through the Collaborative research Center grant TRR265 EnCoDe [138]. F.K. and P.K. also acknowledge funding by the Deutsche Forschungs Gesellschaft through the Collaborative Research Center SFB636 (Project D6). Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.Pérez-Cervera, L.; De Santis, S.; Marcos, E.; Ghorbanzad-Ghaziany, Z.; Trouvé-Carpena, A.; Selim, MK.; Pérez-Ramírez, Ú.... (2023). Alcohol-induced damage to the fimbria/fornix reduces hippocampal-prefrontal cortex connection during early abstinence. Acta Neuropathologica Communications. 11(1):1-21. https://doi.org/10.1186/s40478-023-01597-812111

Invariant higher-order variational problems II

Motivated by applications in computational anatomy, we consider a second-order problem in the calculus of variations on object manifolds that are acted upon by Lie groups of smooth invertible transformations. This problem leads to solution curves known as Riemannian cubics on object manifolds that are endowed with normal metrics. The prime examples of such object manifolds are the symmetric spaces. We characterize the class of cubics on object manifolds that can be lifted horizontally to cubics on the group of transformations. Conversely, we show that certain types of non-horizontal geodesics on the group of transformations project to cubics. Finally, we apply second-order Lagrange--Poincar\'e reduction to the problem of Riemannian cubics on the group of transformations. This leads to a reduced form of the equations that reveals the obstruction for the projection of a cubic on a transformation group to again be a cubic on its object manifold.Comment: 40 pages, 1 figure. First version -- comments welcome

Approximations of Shape Metrics and Application to Shape Warping and Empirical Shape Statistics

International audienceThis chapter proposes a framework for dealing with two problems related to the analysis of shapes: the definition of the relevant set of shapes and that of defining a metric on it. Following a recent research monograph by Delfour and Zolésio [8], we consider the characteristic functions of the subsets of ℝ2 and their distance functions. The L 2 norm of the difference of characteristic functions and the L∞ and the W 1,2 norms of the difference of distance functions define interesting topologies, in particular that induced by the well-known Hausdorff distance. Because of practical considerations arising from the fact that we deal with image shapes defined on finite grids of pixels, we restrict our attention to subsets of ℝ2 of positive reach in the sense of Federer [12], with smooth boundaries of bounded curvature. For this particular set of shapes we show that the three previous topologies are equivalent. The next problem we consider is that of warping a shape onto another by infinitesimal gradient descent, minimizing the corresponding distance. Because the distance function involves an inf, it is not differentiable with respect to the shape. We propose a family of smooth approximations of the distance function which are continuous with respect to the Hausdorff topology, and hence with respect to the other two topologies. We compute the corresponding Gâteaux derivatives. They define deformation flows that can be used to warp a shape onto another by solving an initial value problem. We show several examples of this warping and prove properties of our approximations that relate to the existence of local minima. We then use this tool to produce computational de.nitions of the empirical mean and covariance of a set of shape examples. They yield an analog of the notion of principal modes of variation. We illustrate them on a variety of examples

Large-Eddy Simulation of Turbulent Flames in Syn-Gas Fuel-Air Mixtures

Combustion characteristics of synthetic gaseous fuels (H2 and CO mixture) have been investigated in laminar and turbulent flow congurations with special emphasis on flame structure and propagation characteristics of CO-rich and H2-rich premixed flames. Two reduced CO H2 mechanisms (10-step and 5-step) are first investigated and it is shown that the 10-step mechanism is quite accurate over a wide range of equivalence ratios and with and without CO2 dilution. The 10-step mechanism is then used for both laminar and turbulent premixed flame calculations of both CO-rich and H2-rich mixtures. The effect of a single isolated vortex interacting with a laminar flame and of a pair of counter rotating vortices with a turbulent premixed \ud flame front are investigated for different turbulence levels. It is shown that H2 reaction zone is much thinner than the CO reaction zone, and that they do not overlap physically. Under certain conditions, the H2 reaction rate contours can become broken even when the CO reaction rate contours remains contiguous. Flame structure and propagation (burning) speed are substantially different depending upon the syn-gas (COH2) composition. Flame-vortex interaction creates large-scale flame wrinkling, the scale of which also depends on the initial fuel composition. Flame-vortex interactions also causes local enhancement and dissipation of vorticity depending on the local baroclinic torque and dilatation effects