Fibrosis is thought to play an important role in formation and maintenance of atrial fibrillation (AF). The propensity of fibrosis to increase AF vulnerability depends not only on its amount, its texture plays a crucial role as well. While the detection of fibrotic tissue patches in the atria with extracellular recordings is feasible based on the analysis of electrogram fractionation, as used in clinical practice to identify ablation targets, the classification of fibrotic texture is a more challenging problem. This study seeks to establish a method for the electro-anatomical characterization of the fibrotic textures based on the analysis of electrogram fractionation. The proposed method exploits the dependency of fractionation patterns on the incidence direction of wavefronts which differs significantly as a function of texture. A histologically detailed computer model of the right atrial isthmus was developed for testing the method. A stimulation protocol was conceived which generated various incidence directions for any given recording site where electrograms were computed. A classification method is derived then for discriminating three types of fibrosis, no fibrosis (control), diffuse and patchy fibrosis. Simulation results showed that electrogram fractionation and amplitudes and their dependency upon incidence direction allow a robust discrimination between different classes of fibrosis. Finally, to minimize the technical effort, sensitivity analysis was performed to identify a minimum number of incidence directions required for robust classification.

Absrmct-A continuing interest exists in the Department of Defense to stress technology wherever it may result in the improvement of a military system. One important area where this is currently occurring is in laser communications. Specifically, an extensive effort is underway to exploit the "BIue/Green" transmission window in the ocean and develop a strategic laser communication system operating between an orbiting satellite and a submerged submarine. In this paper we discuss some of the operational motivations for such a system together with a generic system design.

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The progressive automation and consistent rationalization in production of automotive components requires the use of new sheet materials as well as innovations in press and tool technologies. Sheet metal forming is getting more and more complex. Thus several structural defects like thinning, cracks and creases as well as geometrical imprecisions due to spring back may occur. At the same time, consumer demands are rising concerning product quality and value for money. Therefore optimized processes and efficient methods of quality control are required. As the main objective a 100%-in-process quality control throughout the process chain is demanded in press shops. The aim of the experiments presented here was to detect structural faults in formed body components. Thinning is often considered a failure criterion in the metal forming industry. At high-strained parts even cracks may develop as a result of excessive structural thinning. Especially in advancement of highstrength steels, edge cracking may be a significant failure mode in many sheet metal stamping processes. Furthermore research activities were focused on the quality of formed threads: their presence and accurate shape. Inline measurements by the help of electromagnetic and micromagnetic NDE techniques offer the opportunity for online measurements of physical parameters while feeding acquired data into calibrated regression models. Therefore changes in mechanical material characteristics can be predicted for ferromagnetic magnetorestrictive materials and failures can be discovered. Eddy current testing in conjunction with multivariate analysis methods have been used for quality control on formed body components. The method proved to be suitable to discover cracks and, in some cases, thinning. The results show a significant correlation between eddy current signals and critical amounts of thinning. Future research may investigate how to develop these testing methods for inline control.

In experiments with cardiac tissue, local conduction is described by waveform analysis of the derivative of the extracellular potential Φ(e) and by the loop morphology of the near-field strength E (the components of the electric field parallel and very close to the tissue surface). The question arises whether the features of these signals can be used to quantify the degree of fibrosis in the heart. A computer model allows us to study the behavior of electric signals at the endocardium with respect to known configurations of microstructure which can not be detected during the electrophysiological experiments. This work presents a 2D-computer model with sub-cellular resolution of atrial micro-conduction in the rabbit heart. It is based on the monodomain equations and digitized histographs from tissue slices obtained post-experimentum. It could be shown that excitation spread in densely coupled regions produces uniform and anisotropic conduction. In contrast, zones with parallel fibers separated by uncoupling interstitial space or connective tissue may show uniform or complex signals depending on pacing site. These results suggest that the analysis of Φ(e) and E combined with multi-site pacing could be used to characterize the type and the size of fibrosis.