Multi-site H-bridge breathers in a DNA--shaped double strand

We investigate the formation process of nonlinear vibrational modes representing broad H-bridge multi--site breathers in a DNA--shaped double strand. Within a network model of the double helix we take individual motions of the bases within the base pair plane into account. The resulting H-bridge deformations may be asymmetric with respect to the helix axis. Furthermore the covalent bonds may be deformed distinctly in the two backbone strands. Unlike other authors that add different extra terms we limit the interaction to the hydrogen bonds within each base pair and the covalent bonds along each strand. In this way we intend to make apparent the effect of the characteristic helicoidal structure of DNA. We study the energy exchange processes related with the relaxation dynamics from a non-equilibrium conformation. It is demonstrated that the twist-opening relaxation dynamics of a radially distorted double helix attains an equilibrium regime characterized by a multi-site H-bridge breather.Comment: 27 pages and 10 figure

Regulation and Incentives in European Aviation

We study the effect of liberalization on costs and competition in the European airline industry. We construct and estimate a model that includes demand, capacity, and cost equations. The latter accounts for inefficiency and cost-reducing effort. We show that failure to account for the choice of effort would lead to biased estimates of efficiency and competition in the industry. We also find that the last European Union package of deregulatory measures has led to significant efficiency improvements and has fostered competition.Publicad

The effects of airline alliances: What do the aggregate data say?

We consider an empirical model of worldwide airline alliances that we apply to a large set of companies for the period 1995-2000. Using observations at the companies level, we estimate a cost, capacity, and demand system that accounts for cross-price elasticities. From the estimates, we shed light on the fact that many airlines involved in the same alliances are potential substitutes. We also test for the effects of alliances on airlines’ fares and suggest that airlines inside alliances cut prices by 5% on average compared to airlines outside alliances. Finally, we construct price-cost margins for each airlines and suggest that current pricing habits are not uniform and vary from one alliance to another.alliances, airline, cross-price elasticities, Nash behavior

Multimarket Contact in Pharmaceutical Markets

The purpose of this paper is to analyze the effect of multimarket contact on the behavior of pharmaceutical firms controlling for different levels of regulatory constraints using IMS MIDAS database. Theoretically, firms that meet in several markets are expected to be capable of sustaining implicitly more profitable out- comes, even if perfect monitoring is not possible. Firms may find it profitable to redistribute their market power among markets where they are operating. We present evidence for nine OECD countries with different degrees of regulation and show that regulation affects the importance of economic forces on firms' price setting behavior. Furthermore, our results confirms the presence of the predictions of the multimarket theory for more market friendly countries (U.S. and Canada) and less regulated ones (U.K., Germany, Netherlands), in contrast, for highly regulated countries (Japan, France, Italy and Spain) the results are less clear with some countries beingPharmaceutical prices, Multimarket Contact, Regulation

Multimarket contact in pharmaceutical markets

We analyze the effect of multimarket contact on the pricing behavior of pharmaceutical firms controlling for different levels of regulatory constraints using the IMS MIDAS database for the industry. Theoretically, under product differentiation, firms may find it profitable to allocate their market power among markets where they are operating, specifically from more collusive to more competitive ones. We present evidence for nine OECD countries suggesting the existence of a multimarket effect for more market friendly countries (U.S. and Canada) and less regulated ones (U.K., Germany, Netherlands), while the results are more unstable for highly regulated countries with some countries being consistent with the theory (France) while others contradicting it (Japan, Italy and Spain). A key result indicates that in the latter countries, price constraints are so intense, that there is little room for allocating market power. Thus equilibrium prices are expected in general to be lower in regulated countries.Pharmaceutical prices, Multimarket Contact, Regulation

Liberalización y competencia en los mercados aéreos europeos

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Productivity Differences in the Airline Industry: Partial Deregulation versus Short Run Protection

This paper specifies and estimates a production function for the airline industry, identifying firms' network characteristics and efficiency as the main determinants of their productivity. The application of this analysis to the European market shows that productivity differences among flag carriers could explain the governments' different views about deregulation at the beginning of the eighties. The introduction of liberal bilateral agreements by some European governments has given their flag carriers incentives to start adjusting their structure in anticipation of future liberalization in the European market while other European flag carriers have delayed this adjustment.Financial support from the Generalitat Valenciana (GV-3140/95) is gratefully acknowledgedPublicad

Liberalización y Competencia en el Sector Eléctrico

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El problema de la garantía de suministro en los mercados liberalizados de electricidad

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Reducing sample variance: halo biasing, non-linearity and stochasticity

Comparing clustering of differently biased tracers of the dark matter distribution offers the opportunity to reduce the cosmic variance error in the measurement of certain cosmological parameters. We develop a formalism that includes bias non-linearities and stochasticity. Our formalism is general enough that can be used to optimise survey design and tracers selection and optimally split (or combine) tracers to minimise the error on the cosmologically interesting quantities. Our approach generalises the one presented by McDonald & Seljak (2009) of circumventing sample variance in the measurement of $f\equiv d \ln D/d\ln a$. We analyse how the bias, the noise, the non-linearity and stochasticity affect the measurements of $Df$ and explore in which signal-to-noise regime it is significantly advantageous to split a galaxy sample in two differently-biased tracers. We use N-body simulations to find realistic values for the parameters describing the bias properties of dark matter haloes of different masses and their number density. We find that, even if dark matter haloes could be used as tracers and selected in an idealised way, for realistic haloes, the sample variance limit can be reduced only by up to a factor $\sigma_{2tr}/\sigma_{1tr}\simeq 0.6$. This would still correspond to the gain from a three times larger survey volume if the two tracers were not to be split. Before any practical application one should bear in mind that these findings apply to dark matter haloes as tracers, while realistic surveys would select galaxies: the galaxy-host halo relation is likely to introduce extra stochasticity, which may reduce the gain further.Comment: 21 pages, 13 figures. Published version in MNRA