Demand for private health insurance: Is there a quality gap?

Quality of care is qualified as a main determinant of the demand for voluntary private health insurance (PHI) in National Health Systems (NHS). This paper provides new evidence on the influence of the quality gap between public and private health insurance and other demand determinants in the demand for PHI in Catalonia. The demand for PHI is modelled as a demand for health care quality. Unlike previous studies, the database employed allows for the development of a link between the theoretical and the empirical model dealing with unobserved heterogeneity and endogeneity issues. Results suggest that a rise in PHI quality enhances an equivalent influence in the demand for PHI as an equal reduction of NHS quality. Income and price elasticity estimates are consistent with the observed feature that PHI appears to be a luxury good and individuals tend to be relatively insensible to tax relief's and monetary co-payments in insurance contracts.Private health insurance, health care quality, insurance premium

Semi-inclusive radiative decays of Upsilon 1S

We discuss in detail the photon spectrum of radiative Upsilon 1S decays taking into account a number of results that have recently appeared in the literature. In particular, we show how to consistently combine expressions which are valid in the upper end-point region, where NRQCD factorization breaks down, with those of the central region, where NRQCD factorization holds. An excellent description of data is achieved, but theoretical errors are large.Comment: 18 pages, 7 figures. Minor modifications. References added and corrected. Journal versio

Radiative decays and the nature of heavy quarkonia

We argue that the photon spectra in radiative decays of various heavy quarkonium states provide important information on their nature. If two of these states are in the strong coupling regime, we are able to produce a parameter-free model independent formula, which holds at next-to-leading order and includes both direct and fragmentation contributions. When the formula is checked against recent CLEO data it favors Upsilon (2S) and Upsilon (3S) in the strong coupling regime and disfavors Upsilon (1S) in it.Comment: 5 pages, 3 figures. Clarifications introduced, including extra curve in plots. Journal versio

One point functions for black hole microstates

We compute one point functions of chiral primary operators in the D1-D5 orbifold CFT, in classes of states corresponding to microstates of two and three charge black holes. Black hole microstates describable by supergravity solutions correspond to coherent superpositions of states in the orbifold theory and we develop methods for approximating one point functions in such superpositions in the large N limit. We show that microstates built from long strings (large twist operators) have one point functions that are suppressed by powers of N. Accordingly, even when these microstates admit supergravity descriptions, the characteristic scales in these solutions are comparable to higher derivative corrections to supergravity.Comment: 74 page

Opportunities for asteroid retrieval missions

Asteroids and comets are of strategic importance for science in an effort to uncover the formation, evolution and composition of the Solar System. Near-Earth Objects (NEOs) are of particular interest because of their accessibility from Earth, but also because of their speculated wealth of material resources. The exploitation of these resources has long been discussed as a means to lower the cost of future space endeavours. In this chapter, we analyze the possibility of retrieving entire objects from accessible heliocentric orbits and moving them into the Earth’s neighbourhood. The asteroid retrieval transfers are sought from the continuum of low energy transfers enabled by the dynamics of invariant manifolds; specifically, the retrieval transfers target planar, vertical Lyapunov and halo orbit families associated with the collinear equilibrium points of the Sun-Earth Circular Restricted Three Body problem. The judicious use of these dynamical features provides the best opportunity to find extremely low energy transfers for asteroidal material. With the objective to minimise transfer costs, a global search of impulsive transfers connecting the unperturbed asteroid’s orbit with the stable manifold phase of the transfer is performed. A catalogue of asteroid retrieval opportunities of currently known NEOs is presented here. Despite the highly incomplete census of very small asteroids, the catalogue can already be populated with 12 different objects retrievable with less than 500 m/s of Δv. All, but one, of these objects have an expected size in the range that can be met by current propulsion technologies. Moreover, the methodology proposed represents a robust search for future retrieval candidates that can be automatically applied to a growing survey of NEOs

Near-Earth asteroid resource accessibility and future capture mission opportunities

In-Situ Resource Utilization (ISRU) has always been suggested for ambitious space endeavours; and asteroids and comets in particular are generally agreed to be ideal sources, both in terms of its accessibility and wealth. The future utilisation of asteroid resources is here revisited by, firstly, providing an estimate of the total amount of accessible resources in the Earth’s neighbourhood and, secondly, by envisaging a series of missions in order to retrieve resources from the most accessible objects known today. An analytical multi-impulsive transfer model is proposed in order to define the region in Keplerian space from which resources are accessible, and mapped subsequently into a near-Earth asteroid model, to understand the availability of material. This estimate shows a substantial amount of resources can be accessible at relatively low energy-cost; on the order of 1014 kg of material could potentially be accessed at an energy cost lower than that required to access the resources in the Moon. Most of this material is currently undiscovered, but the current surveyed population of near-Earth asteroid provides a good starting point for a search for future capture opportunities. The possibility of capturing, i.e., placing the asteroid into an orbit in permanent close proximity to Earth, a small-size NEO or a segment from a larger object would be of great scientific and technological interest in the coming decades. A systematic search of capture candidates among catalogued NEOs is presented, which targets the L2 region as the destination for the captured material. A robust methodology for systematic pruning of candidates and optimisation of capture trajectories through the stable manifold of planar Lyapunov orbits around L2 has been implemented and tested. Five possible candidates for affordable asteroid retrieval missions have been identified among known NEOs, and the transfers to the L2 region calculated. These transfers enable the capture of bodies with 2-8 meters diameter with modest propellant requirements. Because of the optimal departure dates, two of them have been identified as attractive targets for capture missions in the 2020-2030 time frame

El pensament de Karl R. Popper

Es poden establir les proposicions científiques amb plena certesa? Popper ho nega. Però no sembla pas que apliqui aquest criteri quan estudia els sistemes social