Chiroptera | EPFL Graph Search

Les Chiroptères (Chiroptera), appelés couramment chauves-souris (ou chauvesouris), sont un ordre de mammifères placentaires comptant près de , soit un cinquième de près de de mammifères connues ; avec regroupés en . C'est le groupe de mammifères le plus important après celui des rongeurs. Ces animaux nocturnes volants sont souvent capables d'écholocation (capacité surtout développée chez les microchiroptères insectivores ; essentiellement actifs la nuit, ils se dirigent dans l'obscurité en émettant des ultrasons dont ils captent la réflexion, écholocalisant ainsi leurs proies et les obstacles. Les mégachiroptères, quant à eux, se fient plus à leur vue et à leur odorat). Les chiroptères sont les seuls mammifères doués du vol actif, à distinguer du vol plané que pratiquent les écureuils volants, les phalangers ou les galéopithèques. Ils se déplacent dans les airs grâce à une aile formée d'une membrane de peau entre le corps, les membres et les doigts. La p

Thermal microsensors for in vitro and in vivo monitoring of chemical and biological processes

Rima Padovani

Metabolism is a highly coordinated biochemical cellular activity indispensable for sustaining life, and is often related to mitochondrial functioning. Innovative technological approaches allowing the study of the thermal signature of chemical and metabolic processes are presented in this thesis. In particular, two solutions are proposed: (i) a nanocalorimetric platform enabling measurements of biochemical heat production in vitro, and (ii) a method for localized in vivo temperature measurements in mice using implantable miniaturized sensors. First, the design and development of the nanocalorimetric platform is presented. In particular, this platform is built around a commercial thermopile-based sensor chip, on which an open-well reservoir holding a sample with a volume of a few tens of microliter is directly positioned. Both components are embedded into an isothermal housing providing an excellent temperature stability (± 1 mK), which is a prerequisite for accurate heat power measurements. Furthermore, the platform is characterized by a fast thermalization time to the target temperature (less than 30 minutes) and a fast sensing response time (a few seconds). Numerical simulations, which allowed the optimization of the platform design, are also reported. Electrical calibration of the platform was carried out using resistive heaters positioned either on the sensor chip or in the sample reservoir. A heat power limit of detection of 70 nW was estimated. Then, two reactions for the validation of the nanocalorimetric platform were investigated: (i) the mixing of 1-propanol in water, and (ii) the oxidation of glucose catalyzed by glucose oxidase. The results showed good agreement with literature, confirming that our versatile platform may be applied to many thermochemical studies, including thermodynamic analysis and kinetic reaction analysis. Furthermore, localized in vivo temperature measurements in mice by means of implantable miniaturized sensors are presented. The aim was to monitor mouse metabolism during cold exposure, and to record possible temperature differences between the body temperature measured in the abdomen and the temperature of the brown adipose tissue (BAT) situated in the interscapular area. This approach is of biological interest as it may help unravelling the question whether biochemical activation of BAT is associated with local increase in metabolic heat production. Specifically, the preparation and calibration of miniaturized thermistor sensors are reported and the surgical procedure is also described. Temperature measurements, carried out on mice during cold exposure (6 °C) for a maximum duration of 6 hours, are presented and analyzed. Control measurements with a conventional probe confirmed the good performance of the implanted sensors. Moreover, analysis of the experimental results allowed the identification of two different mouse phenotypes, distinguishable in terms of their metabolic resistance to cold exposure. This difference was investigated from the thermal point of view by computational simulations. A simple physical model of the mouse body allowed to reproduce the global evolution of hypothermia and to explain qualitatively the temperature difference between abdomen and BAT locations. While with this approach, we have demonstrated the importance and feasibility of localized temperature measurements on mice, further optimization of this technique is foreseen to better identify local metabolism variations.

EPFL2016

Investigation of effective processes parameters on lead (II) adsorption from wastewater by biochar in mild air oxidation pyrolysis process

Farzaneh Talebkeikhah, Mohsen Talebkeikhah

This study evaluates and compares several machine learning methods on the effects of different parameters in lead adsorption capacity. pH, contact time, adsorbent dosage and initial lead concentration were considered as inputs and adsorption capacity was regarded as output. For analysing the input parameters, the response surface methodology was used for experimental designs and the obtained results were utilised here as training sets. Various data mining approaches like support vector machine (SVM), group method of data handling (GMDH), decision tree, random forest, radial basis function (RBF), adaptive neuro-fuzzy inference system (ANFIS) and multilayer perceptron (MLP) neural network were implemented to model the problem and two different optimisation techniques named bat algorithm (BAT) and Grasshopper Optimisation Algorithm (GOA) were employed with MLP and ANFIS model for optimising. By comparing different statistical parameters such as Average Absolute Relative Deviation (AARD), coefficient of determination (R-2), Root Mean Square Error (RMSE) and Standard Deviation (SD), it is found out that SVM method has a considerably better performance relative to other methods for estimating adsorption capacity parameter. Furthermore, coupling of MLP and ANFIS with GOA increases the accuracy of these models.

TAYLOR & FRANCIS LTD2020

Aeroelastic characterisation of a bio-inspired flapping membrane wing

Alexander Gehrke, Karen Ann J Mulleners, Jules Ange Philippe Richeux, Esra Uksul

Natural fliers like bats exploit the complex fluid-structure interaction between their flexible membrane wings and the air with great ease. Yet, replicating and scaling the balance between the structural and fluid-dynamical parameters of unsteady membrane wings for engineering applications remains challenging. In this study, we introduce a novel bio-inspired membrane wing design and systematically investigate the fluid-structure interactions of flapping membrane wings. The membrane wing can passively camber, and its leading and trailing edges rotate with respect to the stroke plane. We find optimal combinations of the membrane properties and flapping kinematics that out-perform their rigid counterparts both in terms of increased stroke-average lift and efficiency, but the improvements are not persistent over the entire input parameter space. The lift and efficiency optima occur at different angles of attack and effective membrane stiffnesses which we characterise with the aeroelastic number. At optimal aeroelastic numbers, the membrane has a moderate camber between 15% and 20% and its leading and trailing edges align favourably with the flow. Higher camber at lower aeroelastic numbers leads to reduced aerodynamic performance due to negative angles of attack at the leading edge and an over-rotation of the trailing edge. Most of the performance gain of the membrane wings with respect to rigid wings is achieved in the second half of the stroke when the wing is decelerating. The stroke-maximum camber is reached around mid-stroke but is sustained during most of the remainder of the stroke which leads to an increase in lift and a reduction in power. Our results show that combining the effect of variable stiffness and angle of attack variation can significantly enhance the aerodynamic performance of membrane wings and has the potential to improve the control capabilities of micro air vehicles.