Lettre du président

Éditorial: Lettre ouverte, pieds mouillés, au Président

Uncollected Short Stories: Lettre du Cimetière

Ecole Normale Supérieure de Cachan 61 , avenue du Président Wilson 94235 Cachan Cedex France

Well-structured transition systems (WSTS's) are a general class of innnite state systems for which decidability results rely on the existence of a well-quasi-ordering between states that is compatible with the transitions. In this article, we provide an extensive treatment of the WSTS idea and show several new results. Our improved deenitions allow many examples of classical systems to be seen ...

Jean-Pierre Ramis, président,

Cytochemical fractionation of the Lettre-Ehrlich ascites tumor.

SUMMARY A method for cytochemical fractionation of the Lettré-Ehrlich ascites tumor has been presented. The cells were exposed to dilute Ringer solution which increased the cell size and rigidity and allowed them to be homogenized in 0.44 M sucrose with the use of the Dounce all-glass "ball and cylinder" homogenizer. Nuclear, mitochondrial, and microsome + "soluble" fractions were obtained and...