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Coil embolization offers a new approach to treat aneurysms. This medical procedure is namely less invasive than an open-surgery as it relies on the deployment of very thin platinum-based wires within the aneurysm through the arteries. When performed intracranially, this procedure must be particularly accurate and therefore carefully planned and performed by experienced radiologists. A simulator of the coil deployment represents an interesting and helpful tool for the physician by providing information on the coil behavior. In this paper, an original modeling is proposed to obtain interactive and accurate simulations of coil deployment. The model takes into account geometric nonlinearities and uses a shape memory formulation to describe its complex geometry. An experimental validation is performed in a contact-free environment to identify the mechanical properties of the coil and to quantitatively compare the simulation with real data. Computational performances are also measured to insure an interactive simulation. [ABSTRACT FROM AUTHOR]

Helical springs are usually made from a metal wire of circular cross-section. The use of both a hollow circular section and composite material could reduce the spring mass substantially1. The design of a composite material tubular helical spring is not straightforward. The definition of many parameters (design variables) is required in order to get both the desired technical specifications and the best compromise among spring objective functions. In other words, given the technical specifications, (e.g. stiffness, maximum deflection, maximum acting load, etc.), the designer is charged to find the spring geometrical and mechanical parameters (diameter of the helical coil, number of coils, number of laminae of the tubular element, orientation of fibres, etc.) in order to gain the best compromise among the many different spring objective functions (minimum mass, minimum production cost, etc.). [ABSTRACT FROM AUTHOR]

Neurofilaments belong to the Class IV family of Intermediate filaments and are neuron-specific. They are classed into three distinct groups according to their molecular masses; NF-H (heavy chain), NF-M (middle-chain) and NF-L (light chain). Together with microtubules and their associated proteins, neurofilaments make up the dynamic axonal cytoskeleton. Neurofilaments comprise a central alpha helical coil-coiled domain flanked by an amino terminal head domain and in the case of NF-H and NF-M, a hypervariable carboxy-terminal tail domain. Neurofilaments participate in dynamic properties of the axonal cytoskeleton such as axon outgrowth, axonal transport and the control of axonal caliber. They contain multiple phosphorylation sites in their amino-head and carboxy-tail domains that are phosphorylated topographically by a number of kinases and the phosphorylation of neurofilaments is related to their functions. Expression and phosphorylation of neurofilaments is developmentally regulated and most of the phosphorylation occurs in the tail domains in the mature nervous system. Kinases that have been found to phosphorylate neurofilaments include PKA, CKI, CKII CaMK and the proline directed kinases. The proline directed kinases such as Cdk5, members of the MAP kinase family (p38, SAPK and ERK1/2) and GSK3 phosphorylate the KSP repeats found in NF-M and NF-H tail domains. Aberrant hyperphosphorylation of neurofilaments in dendrites and cell bodies are seen in neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Alzheimer's disease, Parkinson's disease, Pick's disease and Dementia with Lewy bodies. Thus, defects in compartmentalization of cytoskeletal protein phosphorylation may contribute to pathology seen in these diseases. Neurofilament phosphorylation is affected by signal transduction pathways. Calcium influx into neurons causes the phosphorylation of NF-M through the activation of the ERK1/2. Integrin mediated signaling also causes the phosphorylation of NF-H through the activation of Cdk5 activity. Recent studies have also shown that kinase cascades can be affected by myelin associated glycoprotein (MAG), a major glial protein found in periaxonal membranes of glial cells. MAG appears to be involved in bi-directional signaling affecting axonal properties such as axonal caliber, phosphorylation of neurofilaments and mediating the activity of ERK1/2 and Cdk5. Thus, signal transduction pathways are involved in the phosphorylation of the KSP repeats found in NF-M and NF-H. [ABSTRACT FROM AUTHOR]