Most approaches to the problem of source separation use the assumption of statistical independence. To capture statistical independence higher order statistics are required. In this chapter we will demonstrate how higher order criteria, such as maximum kurtosis, arise naturally from the property of non-stationarity. We will also show that source separation of non-stationary signals can be based...

The mechanisms that regulate NK cell function as a first line of defense against infection and transformation have exceeded our expectations in terms of their sophistication and complexity. Quiescent, circulating NK cells can be activated by either soluble mediators, such as interferons and cytokines, or by direct cell–cell contact. Activation occurs during contact not only when NK cells sense ...