Supramolecular Wiring of Benzo‐1,3‐chalcogenazoles through Programmed Chalcogen Bonding Interactions

The high‐yielding synthesis of 2‐substituted benzo‐1,3‐tellurazoles and benzo‐1,3‐selenazoles through a dehydrative cyclization reaction has been reported, giving access to a large variety of benzo‐1,3‐chalcogenazoles. Exceptionally, these aromatic heterocycles proved to be very stable and thus very handy to form controlled solid‐state organizations in which wire‐like polymeric structures are formed through secondary N???Y bonding interactions (SBIs) engaging the chalcogen (Y=Se or Te) and nitrogen atoms. In particular, it has been shown that the recognition properties of the chalcogen centre at the solid state could be programmed by selectively barring one of its σ‐holes through a combination of electronic and steric effects exerted by the substituent at the 2‐position. As predicted by the electrostatic potential surfaces calculated by quantum chemical modelling, the pyridyl groups revealed to be the stronger chalcogen bonding acceptors, and thus the best ligand candidate for programming the molecular organization at the solid state. In contrast, the thiophenyl group is an unsuitable substituent for establishing SBIs in this molecular system as it gives rise to chalcogen–chalcogen repulsion. The weaker chalcogen donor properties of the Se analogues trigger the formation of feeble N???Se contacts, which are manifested in similar solid‐state polymers featuring longer nitrogen–chalcogen distances.     

Percolation and the Existence of a Soft Phase in the Classical Heisenberg Model

We present the results of a numerical investigation of percolation properties in a version of the classical Heisenberg model. In particular we study the percolation properties of the subsets of the lattice corresponding to equatorial strips of the target manifold ². As shown by us several years ago, this is relevant for the existence of a massless phase of the model. Our investigation yields strong evidence that such a massless phase does indeed exits. It is further shown that this result implies lack of asymptotic freedom in the massive continuum limit. A heuristic estimate of the transition temperature is given which is consistent with the numerical data.     

Forward quark jets from protons shattering the color glass condensate

We consider the single-inclusive minijet cross section in pA at forward rapidity within the color glass condensate model of high energy collisions. We show that the nucleus appears black to the incident quarks except for very large impact parameters. A markedly flatter p(t) distribution as compared to QCD in the dilute perturbative limit is predicted for transverse momenta about the saturation scale, which could be as large as Q(2)(s) approximately 10 GeV2 for a gold nucleus boosted to rapidity approximately 10 (as at the BNL-RHIC).     

From Planning Board to Welding Hall: A Case-Study in O.R./Client Involvement

Danish shipyard building supertankers was faced with a production-planning problem in one of its welding-halls, where the bow and stern sections were fabricated. The mandatory constraint of completing each section by a specified day in the production cycle was complicated by a number of other practical constraints. A trial exercise demonstrated that human skills were unbeatable in solving aspects of planning concerned with fitting shapes into spaces-and that the major planning problems were keeping track of planning-progress and computing the labour load. An interactive planning computer-system was devised which gave full rein to the complementary skills of planner and computer. This system had the merit, from management's point of view, that the fullest use could be made of existing planning expertise. The system was designed and implemented in stages over about four months: training sessions at each stage provided valuable input for the design of the next stage.