Despite recent progress in conventional therapeutic approaches, the vast majority of glioblastoma recur locally, indicating that a more aggressive local therapy is required. Interstitial photodynamic therapy (iPDT) appears as a very promising and complementary approach to conventional therapies. However, an optimal fractionation scheme for iPDT remains the indispensable requirement. To achieve that major goal, we suggested following iPDT tumor response by a non-invasive imaging monitoring. Nude rats bearing intracranial glioblastoma U87MG xenografts were treated by iPDT, just after intravenous injection of AGuIX® nanoparticles, encapsulating PDT and imaging agents. Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS) allowed us an original longitudinal follow-up of post-treatment effects to discriminate early predictive markers. We successfully used conventional MRI, T2 star (T2*), Diffusion Weighted Imaging (DWI) and MRS to extract relevant profiles on tissue cytoarchitectural alterations, local vascular disruption and metabolic information on brain tumor biology, achieving earlier assessment of tumor response. From one day post-iPDT, DWI and MRS allowed us to identify promising markers such as the Apparent Diffusion Coefficient (ADC) values, lipids, choline and myoInositol levels that led us to distinguish iPDT responders from non-responders. All these responses give us warning signs well before the tumor escapes and that the growth would be appreciated.
The identification of the aerodynamic coefficients, based on free flight measurements, remains a difficult task for flying vehicles like space vehicles, munitions, UAV. This is mainly due to the nonlinear structure of the mathematical model describing the behavior of the vehicle in flight, the absence of an input signal, the unknown initial conditions and the nonlinear dependence of the aerodynamic coefficients on several state variables. Under these conditions, the estimation of the model parameters must be processed with caution.In this paper, we propose a new procedure for the identification of the aerodynamic coefficients, and more precisely the pitch damping coefficient, Cmq of a re-entry space vehicle. This approach is based on system identification techniques and several steps are required, like the polynomial description of the coefficient as a function of the Mach number and the total angle of attack, the a priori and a posteriori identifiability study, followed by the estimation of the parameters in question based on real experimental free flight measurements. This model-based method improves the accuracy of the estimated coefficient.
To cite this version:Magalie Thomassin, Rachid Malti. Abstract: The aim of this paper is to develop a subspace method for state-space identification of continuous-time systems using fractional commensurate models. As compared to the classical state-space representation, the commensurate differentiation order must be estimated besides the state-space matrices. The latter are estimated with conventional subspace-based techniques using QR and singular value decompositions, whereas the commensurate order is estimated using nonlinear programming. This is the first method developed for multi-input multi-output system identification of fractional models. The performances are demonstrated by simulations at various signal-to-noise ratios assuming a known then an unknown commensurate order.
International audienceThis paper deals with parameter selection and estimation of large and complex simulation models. This estimation problem is addressed in the case of passive observation, i.e. when no controlled experiment is possible. Given the lack of information in the data, an appropriate methodology is proposed to select and estimate some physical parameters of the model. Its implementation is based on a new software: Diffedge which makes it possible to symbolically determine model output sensitivity functions of block diagrams. An application to a winding prototype is developed to illustrate the effectiveness of such an approach in practice
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