High-Speed Rail Versus Air Transportation: Case Study of Madrid–Barcelona, Spain.

Travel time savings, better quality of the supplied services, greater comfort for the users, and improved accessibility are the main factors of success of High Speed Rail(HSR)links. This paper presents the results from a revealed and stated preference survey conducted to both HSR and air transport users in the Madrid Barcelona corridor. The data gathered from the stated preference survey was used to calibrate a modal choice model aiming at explaining competition between HSR and air transportation in the corridor. From the model, the authors obtain that prices and service frequency are the most important variables to compete with the other mode. In addition, they found that check-in and security controls at the airport are a crucial variable for the users in their modal choice. Other policies, such as the improvement of parking facilities at the train stations, play a secondary role

A comparative study of secondary ion yield from model biological membranes using Aun+ and C60+ primary ion sources

Aun+ and C60+ primary ion sources have been used to acquire spectra from phospholipids, symmetric liposomes and asymmetric liposomes. We demonstrate that when using different ion beams different chemical information can be obtained. Symmetric and asymmetric liposomes, with 95% asymmetry, were produced and analysed with Au+, Au3+ and C60+ primary ion beams. C60+ gave the greatest yield from the symmetric liposome but after correcting for the yield effects on the data obtained from the asymmetric liposome it has been shown that C60+ is the most surface sensitive, providing the least information from the inner leaflet of the liposome. Aun+ provides the greatest amount of information from the inner leaflet. The results present the possibility of designing ToF-SIMS experiments that selectively probe specific regions of a (bio)molecular surface

Kiloelectronvolt particle-induced emission and fragmentation of polystyrene molecules adsorbed on silver: Insights from molecular dynamics

Polystyrene oligomers adsorbed on Ag{111} have been used as a model system for a molecular dynamics study of polyatomic fragment ejection from large organic adsorbates on metals. The simulation of the interaction between the incident 500 eV Ar atoms and the sample predicts the nature and kinetic energy of the characteristic fragments observed in the low-mass range of the experimental polystyrene secondary ion mass spectrum (SIMS). This agreement confirms that characteristic molecular fragments can be the result of a collisional emission process. Moreover, the results indicate that the ejection of intact molecules occurs frequently. To understand the mechanisms of emission of fragments and parent molecules, a representative set of trajectories has been analyzed in detail. The ejection of characteristic fragments is primarily due to the direct interaction between the primary particle and the organic adsorbate. In contrast, desorption of intact molecules is induced by collision cascades in the sample surface. The emission of energetic intact molecules is best explained by a cooperative uplifting mechanism in which substrate atoms with similar momenta push the molecule upward. For comparison to the 500 eV bombardment conditions, simulations conducted with 5 keV primary particles show that large-scale simultaneous motions in the substrate may also occur, inducing the emission of many silver atoms and organic molecules in a single high action event