University of Maribor

About: University of Maribor is a education organization based out in Maribor, Slovenia. It is known for research contribution in the topics: Population & KEKB. The organization has 3987 authors who have published 13077 publications receiving 258339 citations. The organization is also known as: Univerza v Mariboru.

Conformity enhances network reciprocity in evolutionary social dilemmas

Abstract: The pursuit of highest payoffs in evolutionary social dilemmas is risky and sometimes inferior to conformity. Choosing the most common strategy within the interaction range is safer because it ensures that the payoff of an individual will not be much lower than average. Herding instincts and crowd behaviour in humans and social animals also compel to conformity in their own right. Motivated by these facts, we here study the impact of conformity on the evolution of cooperation in social dilemmas. We show that an appropriate fraction of conformists within the population introduces an effective surface tension around cooperative clusters and ensures smooth interfaces between different strategy domains. Payoff-driven players brake the symmetry in favour of cooperation and enable an expansion of clusters past the boundaries imposed by traditional network reciprocity. This mechanism works even under the most testing conditions, and it is robust against variations of the interaction network as long as degree-normalized payoffs are applied. Conformity may thus be beneficial for the resolution of social dilemmas.

Ultra‐High Surface Area Functional Porous Polymers by Emulsion Templating and Hypercrosslinking: Efficient Nucleophilic Catalyst Supports

Abstract: 4-Dimethylaminopyridine (DMAP) is a highly efficient and important organocatalyst used for a variety of organic reactions, including the acylation and silylation of hindered alcohols, the Baylis–Hillman reaction and the ringopening polymerisation of lactide and other lactones. Heterogeneous versions supported on soluble and crosslinked polymers as well as inorganic nanoparticles have been described. Soluble catalysts and nanoparticles can show high activities but require extra isolation steps for catalyst recycling. On the other hand, catalysts supported on insoluble polymer beads, whilst being simple to recycle, tend to suffer from a drop in activity compared to the homogeneous catalyst. Furthermore, the performance of catalysts supported on gel-type polymer beads is limited by solvent-dependent access to the reactive sites inside the beads. The use of permanently porous (often referred to as macroporous ) polymer beads overcomes these solvent limitations, however reactions with these supports can be slow as mass transfer to the active sites on the internal surface of the porous bead occurs by diffusion only. The mass transport limitations of permanently porous beads can be overcome by using emulsion-templated porous polymers (polyHIPEs), which possess very large pores (1– 100 mm) permitting mass transfer by convection rather than diffusion. PolyHIPE materials are produced from high internal phase emulsions (HIPEs), where the dispersed phase occupies >74 % of the emulsion volume. PolyHIPEs have been prepared from either oil-in-water (o/w) or water-in-oil (w/o) emulsions and have been used in a flow through manner as scavengers, reagents, solid-phase synthesis supports and chromatography media. For polyHIPEs to function as a heterogeneous catalyst support, a high surface area is required. PolyHIPE materials with surface areas up to 690 m g 1 can be prepared by the addition of an organic porogen to the monomer phase together with careful choice of HIPE stabilising surfactant. However the resulting materials are rather weak mechanically. An alternative approach to introducing high surface areas is the hypercrosslinking method. Hypercrosslinked polymers contain a very high density of crosslinks together with molecular-sized pores (micropores), and exhibit important properties such as an ultra-high surface area (up to 2000 m g ) and the ability to sorb large amounts of both thermodynamically good and poor solvents, due to high matrix rigidity and a much reduced degree of chain entanglement. Hypercrosslinked polystyrene, in the form of beads, can be prepared by Lewis acid catalysed post polymerisation crosslinking of poly(4-vinylbenzyl chloride) (pVBC) (Scheme 1). High surface area polyHIPE materials for gas storage have recently been prepared by this method. Hypercrosslinked polyHIPE is a potentially attractive catalyst support material due to the combination in one material of an interconnected network of macropores, facilitating access of reagents to the surface, with an ultra-high surface area produced by the hypercrosslinking induced microporosity. Furthermore, hypercrosslinking VBC polyHIPEs to less than full conversion would leave residual chloromethyl functionality for the attachment of catalysts. In this work, we demonstrate proof of this concept; the hypercrosslinking of VBC polyHIPEs is controlled to leave unreacted benzyl chloride moieties with which to anchor DMAP, leading to a highly efficient, recyclable nucleophilic catalyst (Scheme 1). [a] J. Wall, Prof. N. R. Cameron Department of Chemistry and Biophysical Sciences Institute Durham University South Road, Durham, DH1 3LE (UK) Fax: (+44) 191-3844737 E-mail : n.r.cameron@durham.ac.uk [b] Dr. I. Pulko, Prof. P. Krajnc Faculty of Chemistry and Chemical Engineering University of Maribor Smetanova 17, 2000 Maribor (Slovenia) Fax: (+386)2-2527-774 E-mail : peter.krajnc@uni-mb.si [c] Dr. I. Pulko Polymer Technology College Pod gradom 4, 2380 Slovenj Gradec (Slovenia) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.200903043.

Observation of a near-threshold D0D̄0π0 enhancement in B→D0D̄0π0K decay

Abstract: Reference EPFL-ARTICLE-154578doi:10.1103/PhysRevLett.97.162002View record in Web of Science Record created on 2010-11-05, modified on 2017-12-10