On the Sensitivity of Massive Star Nucleosynthesis and Evolution to Solar Abundances and to Uncertainties in Helium Burning Reaction Rates

We explore the dependence of pre-supernova evolution and supernova nucleosynthesis yields on the uncertainties in helium burning reaction rates. Using the revised solar abundances of Lodders (2003) for the initial stellar composition, instead of those of Anders & Grevesse (1989), changes the supernova yields and limits the constraints that those yields place on the 12C(a,g)16O reaction rate. The production factors of medium-weight elements (A = 16-40) were found to be in reasonable agreement with observed solar ratios within the current experimental uncertainties in the triple alpha reaction rate. Simultaneous variations by the same amount in both reaction rates or in either of them separately, however, can induce significant changes in the central 12C abundance at core carbon ignition and in the mass of the supernova remnant. It therefore remains important to have experimental determinations of the helium burning rates so that their ratio and absolute values are known with an accuracy of 10% or better.Comment: Accepted for publication by the Astrophysical Journa

Representation of second-order polarisation mode dispersion

A new expansion for the Jones matrix of a transmission medium is used to describe high-order polarisation dispersion. Each term in the expansion is characterised by a pair of principal states and the corresponding dispersion parameters. With these descriptors, a new expression for pulse deformation is derived and confirmed by simulation

OGO-E space vehicle response to transient loading at Atlas booster engine cutoff

Computer program for OGO-E vehicle response analysis to transient loading during Atlas booster burnou

The coevolution of knowledge networks and knowledge creation

Trabajo presentado al 8th European Meeting on Applied Evolutionary Economics celebrado en Sophia Antipolis (Francia) del 10 al 12 de Junio de 2013.Previous research has modeled the evolution of either knowledge creation or knowledge networks, but not their co-evolution. This work presents an agent-based model to cover this gap and challenge the intuition that both phenomena are mutually re-enforcing. The model consists on the rules of partner selection and the rules of knowledge creation by the agents. Agents in the knowledge network choose their partners depending on their previous collaboration history and on their attractiveness. Similarly, the amount of knowledge created by each agent depends on his number of partners and the knowledge he has created earlier. The simulations of the model show a wide variety of scenarios with different policy strategies suitable for each.Peer Reviewe