CD8(+) cytotoxic and CD4(+) helper/inducer T cells develop from common thymocyte precursors that express both CD4 and CD8 molecules. Upon T cell receptor signaling, these cells initiate a differentiation program that includes complex changes in CD4 and CD8 expression, allowing identification of transitional intermediates in this developmental pathway. Little is known about regulation of these e...

Introduction.-Living systems consist of relatively few common chemical elements,' yet have unique properties which set them aside from the rest of matter: they are able to control their exchanges with the surrounding medium and to respond to changes therein; they can transform energy and metabolize matter; and especially they are capable of self-duplication. These remarkable properties, express...

BACKGROUND It has become increasingly apparent that the trophectoderm (TE) at blastocyst stage is much more mosaic than has been appreciated. Whether preimplantation genetic screening (PGS), utilizing a single TE biopsy (TEB), can reliably determine embryo ploidy has, therefore, increasingly been questioned in parallel. METHODS We for that reason here established 2 mathematical models to asse...

‎Let $G$ be a finite group‎. ‎We say that an element $g$ in $G$ is a vanishing element if there exists some irreducible character $chi$ of $G$ such that $chi(g)=0$‎. ‎In this paper‎, ‎we classify groups whose set of vanishing elements is exactly a conjugacy class‎.