Biological structures are stabilized by a variety of noncovalent interactions, such as hydrogen bonds, π –stacking, salt bridges or hydrophobic interactions. Besides hydrogen bonds and π– stacking, cation–π interactions between aromatic rings and positively charged groups have emerged as one of the most important interactions in structural biology. Although the role and energetic characteristic...

We have investigated the structure, interaction energy, electronic properties, and IR spectra of the ammonia-water cation (NH(3)H(2)O)(+) using density functional theory (DFT) and high-level ab initio theory. The ammonia-water cation has three minimum-energy structures of (a) H(2)NH(+)...OH(2), (b) H(3)N(+)...OH(2), and (c) H(3)NH(+)...OH. The lowest-energy structure is (a), followed by (c) and...

This paper applies duration calculus to the speciication and ver-iication of a complex robotics task: Fingers grasping an object. We present a model of the relevant features of the mechanical design and provide a speciication for sensors, actuators and a controller. Requirements are then speciied in an assumption commitment style, and it is checked through calculation that the design satisses t...

The notion of \speciication" plays a key role in the developing science of computing. It is typically considered to be the keystone in the software development process. However, there is no single, generally agreed meaning of \speciication" that bears close scrutiny. Instead there is a variety of diierent, although partially interlocking and overlapping interpretations of the term. We catalogue...