Towards a new edition of the Ogam inscriptions

The need of a new edition fo the Ogam inscriptions has been felt by Celticists for some forty years now, R.A.S. Macalister’s "Corpus Inscriptionum Insularum Celticarum" not having proved a sufficient treatise of the material. ..

Bifurcation in epigenetics: implications in development, proliferation and diseases

Cells often exhibit different and stable phenotypes from the same DNA sequence. Robustness and plasticity of such cellular states are controlled by diverse transcriptional and epigenetic mechanisms, among them the modification of biochemical marks on chromatin. Here, we develop a stochastic model that describes the dynamics of epigenetic marks along a given DNA region. Through mathematical analysis, we show the emergence of bistable and persistent epigenetic states from the cooperative recruitment of modifying enzymes. We also find that the dynamical system exhibits a critical point and displays, in presence of asymmetries in recruitment, a bifurcation diagram with hysteresis. These results have deep implications for our understanding of epigenetic regulation. In particular, our study allows to reconcile within the same formalism the robust maintenance of epigenetic identity observed in differentiated cells, the epigenetic plasticity of pluripotent cells during differentiation and the effects of epigenetic misregulation in diseases. Moreover, it suggests a possible mechanism for developmental transitions where the system is shifted close to the critical point to benefit from high susceptibility to developmental cues.Comment: accepted in Physical Review E as a Rapid Communicatio

Report on a conference about the use of computers in comparative linguistics : held at the University of Bamberg, June 12 - 14, 1992

The here reported conference consisted of the following sections: a) Questions of encoding, norming and transfer of data across system boundaries b) Problems of text processing in Indo-European studies c) Discussion of principles and methods concerning an Indo-European text data base. ..

A Macaulay2 package for characteristic classes and the topological Euler characteristic of complex projective schemes

The Macaulay2 package CharacteristicClasses provides commands for the computation of the topological Euler characteristic, the degrees of the Chern classes and the degrees of the Segre classes of a closed subscheme of complex projective space. The computations can be done both symbolically and numerically, the latter using an interface to Bertini. We provide some background of the implementation and show how to use the package with the help of examples.Comment: 6 page