Localization of algebras over coloured operads

We give sufficient conditions for homotopical localization functors to preserve algebras over coloured operads in monoidal model categories. Our approach encompasses a number of previous results about preservation of structures under localizations, such as loop spaces or infinite loop spaces, and provides new results of the same kind. For instance, under suitable assumptions, homotopical localizations preserve ring spectra (in the strict sense, not only up to homotopy), modules over ring spectra, and algebras over commutative ring spectra, as well as ring maps, module maps, and algebra maps. It is principally the treatment of module spectra and their maps that led us to the use of coloured operads (also called enriched multicategories) in this context.

Preference intensities and risk aversion in school choice: a laboratory experiment

We experimentally investigate in the laboratory two prominent mechanisms that are employed in school choice programs to assign students to public schools. We study how individual behavior is influenced by preference intensities and risk aversion. Our main results show that (a) the Gale-Shapley mechanism is more robust to changes in cardinal preferences than the Boston mechanism independently of whether individuals can submit a complete or only a restricted ranking of the schools and (b) subjects with a higher degree of risk aversion are more likely to play "safer" strategies under the Gale-Shapley but not under the Boston mechanism. Both results have important implications for the efficiency and the stability of the mechanisms.

Usabilitat d'una llibreria virtual

L'àrea escollida per aquest treball de fi de carrera és l'estudi de la usabilitat de llocsweb orientats al comerç electrònic, concretament ens centrarem en l'estudi d'una llibreria virtual.

A simple access pricing rule to achieve the Ramsey outcome for interconnected networks

This paper considers a general and informationally efficient approach to determine the optimal access pricing rule for interconnected networks. It shows that there exists a simple rule that achieves the Ramsey outcome as the unique equilibrium when networks compete in linear prices without network-based price discrimination. The approach is informationally efficient in the sense that the regulator is required to know only the marginal cost structure, i.e. the marginal cost of making and terminating a call. The approach is general in that access prices can depend not only on the marginal costs but also on the retail prices, which can be observed by consumers and therefore by the regulator as well. In particular, I consider the set of linear access pricing rules which includes any fixed access price, the Efficient Component Pricing Rule (ECPR) and the Modified ECPR as special cases. I show that in this set, there is a unique rule that implements the Ramsey outcome as the unique equilibrium independently of the underlying demand conditions.

Capillarity and fibre types in locomotory muscles of wild yellow-legged gulls (Larus cachinnans)

This study analyzes the capillarity and fibre-type distribution of six locomotory muscles of gulls. The morphological basis and the oxygen supply characteristics of the skeletal muscle of a species with a marked pattern of gliding flight are established, thus contributing to a better understanding of the physiology of a kind of flight with low energetic requirements. The four wing muscles studied (scapulotriceps, pectoralis, scapulohumeralis, and extensor metacarpi) exhibited higher percentages of fast oxidative glycolytic fibres (>70%) and lower percentages of slow oxidative fibres (<16%) than the muscles involved in nonflight locomotion (gastrocnemius and iliotibialis). Capillary densities ranged from 816 to 1,233 capillaries mm(-2), having the highest value in the pectoralis. In this muscle, the fast oxidative glycolytic fibres had moderate staining for succinate dehydrogenase and relatively large fibre sizes, as deduced from the low fibre densities (589-665 fibres mm(-2)). All these findings are seen as an adaptive response for gliding, when the wing is held outstretched by isometric contractions. The leg muscles studied included a considerable population of slow oxidative fibres (>14% in many regions), which suggests that they are adapted to postural activities. Regional variations in the relative distributions of fibre types in muscle gastrocnemius may reflect different functional demands placed on this muscle during terrestrial and aquatic locomotion. The predominance of oxidative fibres and capillary densities under 1,000 capillaries mm(-2) in leg muscles is probably a consequence of an adaptation for slow swimming and maintenance of the posture on land rather than for other locomotory capabilities, such as endurance or sprint activities.