On the Convenience to Form Coalitions or Partnerships in Simple Games

A partnership in a cooperative game is a coalition that possesses an internal structure and, simultaneously, behaves as an individual member. Forming partnerships leads to a modification of the original game which differs from the quotient game that arises when one or more coalitions are actually formed. In this paper, the Shapley value is used to discuss the convenience to form either coalitions or partnerships. To this end, the difference between the additive Shapley value of the partnership in the partnership game and the Shapley alliance value of the coalition, and also between the corresponding value of the internal and external players, are analysed. Simple games are especially considered. Research partially supported by Grant BFM 2003-01314 of the Science and Technology Spanish Ministry and the European Regional Development Fund.     

Automorphisms and blocking in simple games

Different (proper as well as improper) simple games may share any nonseparating blocking family. An interesting question is whether all such proper games on one hand, and all improper ones on the other, are isomorphic. The answer is given here and the automorphisms of the blocking family help us to understand the structure and links of all such games.     

Drug release system of ibuprofen in PCL-microspheres

Today, the technology of microencapsulation of active principles is on top of biomedical advances, because through it we can solve many of the problems caused by current methods of taking medication. Active principle microencapsulation not only solves the problems of drug intake but also controls its dosage. In this study was carried out the development of a protocol for the microencapsulation of ibuprofen by solvent evaporation method. A subsequent application of those microencapsulates to biofunctional textile substrates (cotton, polyamide, acrylic, and polyester) using a finishing process, and finally a study of the release of active principle in two different media (deionized water and physiological serum) has been carried out using samples of the treated fabrics that were submerged into a thermostatized vessel at semi-infinite bath conditions. The determination of active principles released to the bath was determined by a UV spectrophotometer. These experimental results have been analyzed and evaluated, and have therefore allowed to define a controlled drug release system by Fickian diffusion in different media.     

Coordination Chemistry of Cyclopropenylidene‐Stabilized Phosphenium Cations: Synthesis and Reactivity of Pd and Pt Complexes

A straightforward synthesis of cyclopropenylidene‐stabilized phosphenium cations 1 a – g through the reaction of [(iPr₂N)₂C₃⁺Cl]BF₄ with secondary phosphines is described. Their donor ability was evaluated by analysis of the CO stretching frequency in Rh complexes [RhCl(CO)L₂](BF₄)₂ and electrochemical methods. The cyclopropenium ring induces a phosphite‐type behavior that can be tuned by the other two substituents attached to the phosphorus atom. Despite of the positive charge that they bear, phosphenium cations 1 a – g still act as two‐electron donor ligands, forming adducts with Pd^II and Pt^II precursors. Conversely, in the presence of Pd⁰ species, an oxidative insertion of the Pd atom into the C_carbene–phosphorus bond takes place, providing dimeric structures in which each Pd atom is bonded to a cyclopropenyl carbene while two dialkyl/diaryl phosphide ligands serve as bridges between the two Pd centers. The catalytic performance of the resulting library of Pt^II complexes was tested; all of the cationic phosphines accelerated the prototype 6‐endo‐dig cyclization of 2‐ethynyl‐1,1′‐biphenyl to afford pentahelicene. The best ligand 1 g was used in the synthesis of two natural products, chrysotoxene and epimedoicarisoside A.     

Oxidation of the perchlorotriphenylmethyl radical to the carbocation,and its unique abrupt reversion

A solution of AlCl(3) in CH(2)Cl(2) reacts slowly, at room temperature, with perchlorotriphenylmethyl radical (PTM(*)), an inert carbon free radical, to give perchlorotriphenylmethyl cation (PTM(+)) quantitatively. However, by gradual addition of CH(2)Cl(2) into the resulting solution a point is reached where the PTM(+) reverts to PTM(*) instantaneously and quantitatively. A mechanism for this exceptional phenomenon is suggested. Some PTM(+) reactions, namely hydrolysis yielding quinonoid species and single-electron transfers with hydride ion donors, are reported and discussed.     

Automorphisms and weighted values

The notion of automorphism is an essential tool to capture the meaning of any mathematical structure. We apply this idea to cooperative games and obtain two interesting characterizations of the automorphisms of such a game: the one, in the complete case, as the permutations of players which preserve the (classical) Shapley value; the other, for the general case, as the permutations preservingall weighted Shapley values.Carreras' research supported by project UPV 036321-HA186/92 of the Basque Country University. Owen's research supported by the National Science Foundation, Grant DMS-9116416. This collaboration was made possible by the Polytechnic University of Catalonia, which sponsored Owen's visit to Terrassa.     

Micelle‐Triggered β‐Hairpin to α‐Helix Transition in a 14‐Residue Peptide from a Choline‐Binding Repeat of the Pneumococcal Autolysin LytA

Choline‐binding modules (CBMs) have a ββ‐solenoid structure composed of choline‐binding repeats (CBR), which consist of a β‐hairpin followed by a short linker. To find minimal peptides that are able to maintain the CBR native structure and to evaluate their remaining choline‐binding ability, we have analysed the third β‐hairpin of the CBM from the pneumococcal LytA autolysin. Circular dichroism and NMR data reveal that this peptide forms a highly stable native‐like β‐hairpin both in aqueous solution and in the presence of trifluoroethanol, but, strikingly, the peptide structure is a stable amphipathic α‐helix in both zwitterionic (dodecylphosphocholine) and anionic (sodium dodecylsulfate) detergent micelles, as well as in small unilamellar vesicles. This β‐hairpin to α‐helix conversion is reversible. Given that the β‐hairpin and α‐helix differ greatly in the distribution of hydrophobic and hydrophilic side chains, we propose that the amphipathicity is a requirement for a peptide structure to interact and to be stable in micelles or lipid vesicles. To our knowledge, this “chameleonic” behaviour is the only described case of a micelle‐induced structural transition between two ordered peptide structures.     

Wavelength-dispersive spectral analysis and quantification of monazites by electron-probe microanalysis

The problem of determining the chemical composition of monazite grains through electron probe microanalysis is studied, by using a scanning electron microscope with a wavelength dispersive spectrometer. A careful qualitative analysis is performed with the purpose of determining all the elements present in the samples, the lines to be used in the quantifications trying to minimize interferences, the angular positions and the acquisition times for the measurement of peak and background intensities and the crystals to be used. Particular emphasis is devoted to the analysis of Th, U and Pb, which are used to determine the age of the rock by means of the U-Th-Pb method, commonly used in geochronology. Quantitative determinations of the chemical composition of monazite grains are performed, optimizing the experimental conditions on the basis of the qualitative analysis. The determinations were made under two different criteria of quantification of oxygen, and the dissimilar results obtained are discussed.