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Section: Contracts and Grants with Industry

Grant with Curie Institute on membrane transport/traffic estimation

Participants : Charles Kervrann, Thierry Pécot.

no. xxx, duration 11 months.

This contract started in July 2008 is associated with the supervision of T. Pécot's thesis funded by Curie Institute for 11 months (previously INRA & INRIA). It concerns the problem of traffic estimation and membrane transport modeling in cell biology. In this study, we have investigated an alternative approach to conventional tracking methods and based on the concept of Network Tomography (NT) (Vardi, 1996). In this approach a dynamic scene made up moving particles along a dense microtubule set, is modeled as a network of interconnected regions of interest. In such a network, a connection between two nodes is called a path and each path consists of one or more unidirectional or bidirectional links. Each link can represent a chain of physical links (microtubules) connected by intermediate routers. Broadly speaking, network inference involves estimating network performance parameters based on traffic measurements at a limited subset of the nodes. In traffic intensity estimation, the measurements consist of counts of objects that pass through nodes in the network. Based on these measurements, the goal is to estimate how particles traffic originated from a source node to a destination node along a path which generally passes through several nodes. In this approach, it is not necessary to track an object through a dynamic scene, just to determine when an object reaches a node, something that is generally easier than estimating a continuous trajectory. This approach simplifies the tracking process because it only requires detection of an object as it moves from one region to another. In exchange, it gives up the ability to estimate an object's state as the motion occurs. Instead, it determines mean traffic intensities based on statistics accumulated over a period of time. It only provides the total number of trips made for which statistics were collected. The measurements are usually the number of vesicles successfully detected at each destination region receiver or the vesicle time between the source and each destination. The inherent randomness in both link-level and path-level measurements motivates the adoption of statistical methodologies.


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