Contestability and sunk costs: An analysis of product R&D competition

The paper shows that Bertrand competition and contestability can be reconciled with sunk costs. When average total costs are constant over a range of output, marginal cost pricing does not conflict with the budget constraint faced by firms. Empirical observations support the notion of constant average total costs. When average total costs are constant, there is no trade-off between dynamic economies and static efficiency. The argument is applied to product R&D competition.industrial organization ;

GEO debris and interplanetary dust: fluxes and charging behavior

In September 1996, a dust/debris detector: GORID was launched into the geostationary (GEO) region as a piggyback instrument on the Russian Express-2 telecommunications spacecraft. The instrument began its normal operation in April 1997 and ended its mission in July 2002. The goal of this work was to use GORID's particle data to identify and separate the space debris to interplanetary dust particles (IDPs) in GEO, to more finely determine the instrument's measurement characteristics and to derive impact fluxes. While the physical characteristics of the GORID impacts alone are insufficient for a reliable distinction between debris and interplanetary dust, the temporal behavior of the impacts are strong enough indicators to separate the populations based on clustering. Non-cluster events are predominantly interplanetary, while cluster events are debris. The GORID mean flux distributions (at mass thresholds which are impact speed dependent) for IDPs, corrected for dead time, are 1.35x10^{-4} m^{-2} s^{-1} using a mean detection rate: 0.54 d^{-1}, and for space debris are 6.1x10^{-4} m^{-2} s^{-1} using a mean detection rate: 2.5 d^{-1}. Beta-meteoroids were not detected. Clusters could be a closely-packed debris cloud or a particle breaking up due to electrostatic fragmentation after high charging.Comment: * Comments: 6 pages, 4 postscript figures, in Dust in Planetary Systems 2005, Krueger, H. and Graps, A. eds., ESA Publications, SP in press (2006). For high resolution version, see: http://www.mpi-hd.mpg.de/dustgroup/~graps/dips2005/GrapsetalDIPS2005.pd

Endovascular Treatment of Resistant and Uncontrolled Hypertension Therapies on the Horizon

The treatment of resistant hypertension has undergone remarkable advancements in recent years. Endovascular radio frequency renal sympathetic denervation (RSD) has shown initial success in treating resistant hypertension by targeting the connection between the brain and renal sympathetic nerves. However, the encouraging results of first-generation RSD have been tempered by important procedural limitations and a need for long-term results of safety and efficacy. In an effort to build on early clinical success, several second-generation RSD technologies are now being developed that may improve procedural safety and efficacy. Preliminary evidence for some of the latest technologies is now available. In this review, we summarize the current evidence in support of RSD and consider unique features of several new technologies that are likely to refine the endovascular treatment of resistant hypertension

De agrarische sector in Nederland naar 2020 : perspectieven en onzekerheden

Dit rapport beantwoordt vooral de vraag: wat zijn de perspectieven van de agrarische sector in Nederland op middellange termijn, tot 2020? Met welke ontwikkelingen en onzekerheden moet rekening worden gehouden en welke aandachtspunten voor het beleid vloeien daar uitvoort? Het rapport is gebaseerd op een combinatie van expertkennis en modelberekeningen. De vraagontwikkeling wordt mede bepaald door de tot 2020 met 1% per jaar doorgaande groei van de wereldbevolking. Deze groei, die lager is dan in het vorige decennium, manifesteert zich vooral buiten de EU, met name in Azië. Voor het aanbod van producten is, naast de beschikbare arbeid, kapitaal en grond, de technologische vernieuwing een belangrijke factor. Het aantal in de agrosector werkzame mensen zal vooral blijven afnemen door de technologische vernieuwing, die een verhoging van de productiviteit mogelijk maakt. Dit kan knelpunten opleveren in arbeidsintensieve deelsectoren, zoals in de tuinbouw. Nieuwe technologische doorbraken, zoals robotisering, kunnen hier een oplossing biede

Gevolgen ontkoppeling slachtpremies voor de vleeskalversector

Dit rapport geeft de mogelijke gevolgen aan van ontkoppeling van de slachtpremie voor de kalfs- en vleessector in Nederland. Of ontkoppeling zal leiden tot een aanzienlijke vermindering van de productie is sterk afhankelijk van de externe omstandigheden, de voorwaarden die zullen worden gesteld en de reactie van de kalverintegratie

Tracking the Temporal-Evolution of Supernova Bubbles in Numerical Simulations

The study of low-dimensional, noisy manifolds embedded in a higher dimensional space has been extremely useful in many applications, from the chemical analysis of multi-phase flows to simulations of galactic mergers. Building a probabilistic model of the manifolds has helped in describing their essential properties and how they vary in space. However, when the manifold is evolving through time, a joint spatio-temporal modelling is needed, in order to fully comprehend its nature. We propose a first-order Markovian process that propagates the spatial probabilistic model of a manifold at fixed time, to its adjacent temporal stages. The proposed methodology is demonstrated using a particle simulation of an interacting dwarf galaxy to describe the evolution of a cavity generated by a Supernov

Spectropolarimetric investigation of the propagation of magnetoacoustic waves and shock formation in sunspot atmospheres

Velocity oscillations in sunspot umbrae have been measured simultaneously in two spectral lines: the photospheric Silicon I 10827 A line and the chromospheric Helium I 10830 A multiplet. From the full Stokes inversion of temporal series of spectropolarimetric observations we retrieved, among other parameters, the line of sight velocity temporal variations at photospheric and chromospheric heights. Chromospheric velocity oscillations show a three minute period with a clear sawtooth shape typical of propagating shock wave fronts. Photospheric velocity oscillations have basically a five minute period, although the power spectrum also shows a secondary peak in the three minute band which has proven to be predecessor for its chromospheric counterpart. The derived phase spectra yield a value of the atmospheric cut-off frequency around 4 mHz and give evidence for the upward propagation of higher frequency oscillation modes. The phase spectrum has been reproduced with a simple model of linear vertical propagation of slow magneto-acoustic waves in a stratified magnetized atmosphere that accounts for radiative losses through Newton's cooling law. The model explains the main features in the phase spectrum, and allows us to compute the theoretical time delay between the photospheric and chromospheric signals, which happens to have a strong dependence on frequency. We find a very good agreement between this and the time delay obtained directly from the cross-correlation of photospheric and chromospheric velocity maps filtered around the 6 mHz band. This allows us to infer that the 3-minute power observed at chromospheric heights comes directly from the photosphere by means of linear wave propagation, rather than from non-linear interaction of 5-minute (and/or higher frequency) modes.Comment: aastex preprint, 32 pages, 12 figure

A New Framework for Understanding Memories and Preference for Music

What can musical memories tell us about preference, and what can musical preferences tell us about memory? In this article we contrast the two perspectives using a dialogic conversation, drawing on insights brought into relief at the recent Music and Lifetime Memories conference. We use dialogue to present two different bodies of relevant background literature and theory and consider their overlaps, interactions, and contradictions in depth. We then compare our two different approaches to the same dataset – the Desert Island Discs archive – which provide complementary perspectives and insights. We interpret each other’s analyses from our own perspectives, and finally conclude with reflections on future directions for the field

A paucigranulocytic asthma host environment promotes the emergence of virulent influenza viral variants

Influenza virus has a high mutation rate, such that within one host different viral variants can emerge. Evidence suggests that influenza virus variants are more prevalent in pregnant and/or obese individuals due to their impaired interferon response. We have recently shown that the non-allergic, paucigranulocytic subtype of asthma is associated with impaired type I interferon production. Here, we seek to address if this is associated with an increased emergence of influenza virus variants. Compared to controls, mice with paucigranulocytic asthma had increased disease severity and an increased emergence of influenza virus variants. Specifically, PB1 mutations exclusively detected in asthmatic mice were associated with increased polymerase activity. Furthermore, asthmatic host-derived virus led to increased disease severity in wild-type mice. Taken together, these data suggest that at least a subset of patients with asthma may be more susceptible to severe influenza and may be a possible source of new influenza virus variants