it is generally recognised that ‘zero’ as we understand the concept today originated in two geographically separated cultures: the maya and indian. however, if zero merely signified a magnitude or a direction separator (i.e. separating those above the zero level from those below the zero level), the egyptian zero, nfr, dating back at least four thousand years, amply served these purposes. if ze...

The readout of morphogen concentrations has been proposed to be an essential mechanism allowing embryos to specify cell identities [Wolpert Trends Genet 12 (1996) 359], but theoretical and experimental results have led to conflicting ideas as to how useful concentration gradients can be established. In particular, it has been pointed out that some models of passive extracellular diffusion exhib...

The identification of direct targets of transcription factors is a key problem in the study of gene regulatory networks. However, the use of high throughput experimental methods, such as ChIP-chip and ChIP-sequencing, is limited by their high cost and strong dependence on cellular type and context. We developed a computational method for the genome-wide identification of functional transcriptio...

It is well known that games with the parity winning condition admit positional determinacy : the winner has always a positional (memoryless) strategy. This property continues to hold if edges rather than vertices are labeled. We show that in this latter case the converse is also true. That is, a winning condition over arbitrary set of colors admits positional determinacy in all games if and onl...

The inherent order within the XML document-centric data model is typically exposed through positional predicates defined over the XPath navigation axes. Although processing algorithms for each axis have already been proposed, the incorporation of positional predicates in them has received very little attention. In this paper, we present techniques that leverage the power of existing, state of t...