Publisher: Richard S. Nicholson Editor-in-Chief: Floyd E. Bloom W lnds of Change Editor: Ellis Rubinstein Managing Editor: Monica M. Bradford Deputy Editors: Philip H. Abelson (Engineering and ApBEIJING, CHINA-A broad path runs straight north from Tiananmen Square through arch plied Sciences); John I. Brauman (Physical Sciences); Thomas R. Cech (Biological Sciences) afterarch, splitting the For...

If (X ′, τ ′,≤′) is an ordered compactification of the partially ordered topological space (X, τ,≤) such that ≤′ is the smallest order that renders (X ′, τ ′,≤′) a T2-ordered compactification of X, then X ′ is called a Nachbin(or order-strict) compactification of (X, τ,≤). If (X ′, τ ′,≤∗) is a finite-point ordered compactification of (X, τ,≤), the Nachbin order ≤′ for (X ′, τ ′) is described i...

J1J2 of the Tetrahymena ribozyme, a sequence of three A residues, connects the RNA-binding site to the catakflic core. Addition or deletion of bases from J1/2 improves turnover and substrate specificity in the site-specific endonuclease reaction catalyzed by this ribozyme: G2CCCUCUA5 (S) + G + GzCCCUCU (P) + GAS. These paradoxical enhancements are caused by decreased affinity of the ribozyme fo...

We construct compact examples of D-manifolds for type IIB strings. The construction has a natural interpretation in terms of compactification of a 12 dimensional ‘F-theory’. We provide evidence for a more natural reformulation of type IIB theory in terms of Ftheory. Compactification of M-theory on a manifold K which admits elliptic fibration is equivalent to compactification of F-theory on K ×S...

‎For a given measure space $(X,{mathscr B},mu)$ we construct all measure spaces $(Y,{mathscr C},lambda)$ in which $(X,{mathscr B},mu)$ is embeddable‎. ‎The construction is modeled on the ultrafilter construction of the Stone--v{C}ech compactification of a completely regular topological space‎. ‎Under certain conditions the construction simplifies‎. ‎Examples are given when this simplification o...

We present new definitions for and give a comprehensive treatment of the canonical compactification of configuration spaces due to Fulton-MacPherson and Axelrod-Singer in the setting of smooth manifolds, as well as a simplicial variant of this compactification. Our constructions are elementary and give simple global coordinates for the compactified configuration space of a general manifold embe...

We consider Kapranov’s Chow quotient compactification of the moduli space of ordered n-tuples of hyperplanes in P r−1 in linear general position. For r = 2, this is canonically identified with the Grothendieck-Knudsen compactification of M0,n which has, among others, the following nice properties: (1) modular meaning: stable pointed rational curves; (2) canonical description of limits of one-pa...

Using stable log maps, we introduce log twisted differentials extending the notion of abelian differentials to the Deligne-Mumford boundary of stable curves. The moduli stack of log twisted differentials provides a compactification of the strata of abelian differentials. The open strata can have up to three connected components, due to spin and hyperelliptic structures. We prove that the spin p...