Finite-temperature phase transition in a class of four-state Potts antiferromagnets

We argue that the four-state Potts antiferromagnet has a finite-temperature phase transition on any Eulerian plane triangulation in which one sublattice consists of vertices of degree 4. We furthermore predict the universality class of this transition. We then present transfer-matrix and Monte?Carlo data confirming these predictions for the cases of the Union Jack and bisected hexagonal lattices.     

A column generation approach for solving the patient admission scheduling problem

This paper addresses the Patient Admission Scheduling (PAS) problem. The PAS problem entails assigning elective patients to beds, while satisfying a number of hard constraints and as many soft constraints as is possible, and arises at all planning levels for hospital management. There exist a few, different variants of this problem. In this paper we consider one such variant and propose an optimization-based heuristic building on branch-and-bound, column generation, and dynamic constraint aggregation to solve it. We achieve tighter lower bounds than previously reported in the literature and, in addition, we are able to produce new best known solutions for five out of twelve instances from a publicly available repository.     

Charged particle spectra in16O induced nuclear collisions at the CERN SPS

Charged particle multiplicity distributions and pseudo-rapidity density distributions from¹⁶O induced nuclear collisions at 200 and 60A GeV are presented. The data were taken, using a minimumbias trigger, with the WA80 set-up at the CERN SPS. In this presentation we focus on how the yield of charged particles depends on the projectile energy, the mass number of the target nucleus and the energy measured in a uranium-plastic sampling calorimeter covering angles close to zero degrees. The data are compared to simulations from the event generator FRITIOF.     

Amino acids attached to 2'-amino-LNA: synthesis and excellent duplex stability

The synthesis of 2'-amino-LNA (the 2'-amino derivative of locked nucleic acid) has opened up a number of exciting possibilities with respect to modified nucleic acids. While maintaining the excellent duplex stability inferred by LNA-type oligonucleotides, the nitrogen in the 2'-position of 2'-amino-LNA monomers provides an excellent handle for functionalisation. Herein, the synthesis of amino acid functionalised 2'-amino-LNA derivatives is described. Following ON synthesis, a glycyl unit attached to the N2'-position of 2'-amino-LNA monomers was further acylated with a variety of amino acids. On binding to DNA/RNA complements, the modified ONs induce a marked increase in thermal stability, which is particularly apparent in a buffer system with a low salt concentration. The increase in thermal stability is thought to be caused, at least in part, by decreased electrostatic repulsion between the negatively charged phosphate backbones when positively charged amino acid residues are appended. Upon incorporation of more than one 2'-amino-LNA modification, the effects are found to be nearly additive. For comparison, 2'-amino-LNA derivatives modified with uncharged groups have been synthesised and their effect on duplex thermal stability likewise investigated.     

Enhancement of muramyldipeptide (MDP) immunostimulatory activity by controlled multimerization on dendrimers

Peptidoglycan is a widespread bacterial PAMP molecule and a powerful initiator of innate immune responses. It consists of repeating units of MDP, which as a monomer is only weakly immunostimulatory. Here, MDP-coupled dendrimers were prepared and investigated for stimulation of pig blood mononuclear cells. Compared to monomeric MDP, MDP-dendrimers induced a markedly enhanced production of IL-12 p40, IL-1β and IL-6 and completely down-regulated surface expression of B7 and MHC class II. These results suggest a possible novel strategy based on controlled multimerization of minimal PAMP motifs on dendrimers for preparing molecularly defined immunostimulators with predictable bioactivities.     

Complexation of tauro- and glyco-conjugated bile salts with α-cyclodextrin and hydroxypropyl-α-cyclodextrin studied by affinity capillary electrophoresis and molecular modelling

The interaction of the bile salts taurocholate, taurodeoxycholate, taurochenodeoxycholate, glycocholate, glycodeoxycholate, and glycochenodeoxycholate present in man, dog, and rat with α-cyclodextrin and 2-hydroxypropyl-α-cyclodextrin was investigated by mobility shift affinity capillary electrophoresis. The cyclodextrins are applied as excipients for solubilisation of drug substances with poor aqueous solubility. Accurate determination of stability constants is challenging for weak analyte-ligand interactions such as the conjugated bile salt α-cyclodextrin interactions. A new approach for correction of medium effects due to the high additive concentrations in the background electrolyte was introduced. The use of prostaglandin A(1) as an interacting marker molecule offered a more satisfactory approach for correction than the commonly employed methods based on viscosity or current ratios. The interacting marker was chosen over a non-interacting marker to avoid the difficult validation of the non-interacting properties. The investigated bile salts all interacted with α-cyclodextrin and 2-hydroxypropyl-α-cyclodextrin. Stability constants ranging from 14 to 95 M(-1) were obtained with slightly higher affinities toward the substituted cyclodextrin. Molecular modelling demonstrated that the interaction between the two species involves the side chain of the bile salt. All together, these results indicate minor bile salt-mediated displacement of substances from α-cyclodextrin complexes in the small intestine.