The influence of geomagnetic activity on mesospheric summer echoes in middle and polar latitudes

The dependence of mesospheric VHF radar echoes during summer months on geomagnetic activity has been investigated with observation data of the OSWIN radar in Kühlungsborn (54° N) and of the ALWIN radar in Andenes (69° N). Using daily mean values of VHF radar echoes and of geomagnetic activity indices in superimposed epoch analyses, the comparison of both data sets shows in general stronger radar echoes on the day of the maximum geomagnetic activity, the maximum value one day after the geomagnetic disturbance, and enhanced radar echoes also on the following 2–3 days. This phenomenon is observed at middle and polar latitudes and can be explained by precipitating particle fluxes during the ionospheric post storm effect. At polar latitudes, the radar echoes decrease however during and one day after very strong geomagnetic disturbances. The possible reason of this surprising effect is discussed

A relativistic model for neutrino pion production from nuclei in the resonance region

We present a relativistic model for electroweak pion production from nuclei, focusing on the $\Delta$ and the second resonance region. Bound states are derived in the Hartree approximation to the $\sigma-\omega$ Walecka model. Final-state interactions of the outgoing pion and nucleon are described in a factorized way by means of a relativistic extension of the Glauber model. Our formalism allows a detailed study of neutrino pion production through $Q^2$, $W$, energy, angle and out-of-plane distributions.Comment: 3 pages, 1 figure, poster presented at the NuInt07 conference on few-GeV neutrino physic

Bis[μ-pentane-2,4-dionato(1−)]bis­{aqua­[1,1,1,5,5,5-hexa­fluoro­pentane-2,4-dionato(1−)]cobalt(II)}

The title complex, [Co2(C5HF6O2)2(C5H7O2)2(H2O)2], is centrosymmetric with a crystallographic inversion center in the middle of the mol­ecule. The octa­hedrally coordinated CoII atoms are bridged by two chelating acetyl­acetonate (acac) ligands and two more electron-poor 1,1,1,5,5,5-hexa­fluoro­pentane-2,4-dionato (hfac) ligands are bonded terminally in a solely chelating manner. The coordinated water mol­ecules form inter­molecular O—H⋯O hydrogen bonds with electron-rich acac O atoms of neighboring mol­ecules, leading to strings of mol­ecules along the a axis

New Perspectives on Audience Activity: ‘Prosumption’ and Media Activism as Audience Practices

Until relatively recently, the subject of social relationships, constituted in and through audience practices, has been a minor part of audience research studies. This chapter explores how social relationships and forms of audience agency change and / or evolve, through the usage of both traditional and ‘new’ media. In a media environment where traditional and new media worlds collide, the potential of audience practices to rework, not only media-audience relationships, but also wider social relationships, is now an important research theme. Two key examples of mediated relationships between social actors in conditions brought about through transformations in media culture are considered. We look at the evolution of audience ‘prosumption’ or ‘produsage’ (Bruns 2007), as well as at audience ‘activism’ (de Jong, Shaw and Stammers 2005). These examples are identified as illustrating new dynamics of social interaction, which may have the potential to contribute to larger, integrative social networks that transcend the existing boundaries of the traditional concept of audience. Against the background of traditional approaches to social relationships in the context of audience studies, we examine in both case studies the respective roles of the technologies, the social actors and the emergent social relationships concerned

Signals of predation-induced directional and disruptive selection in the threespine stickleback

Background: Different predation regimes may exert divergent selection pressure on phenotypes and their associated genotypes. Threespine stickleback Gasterosteus aculeatus have a suite of bony structures, which have been shown to be an effective defence against predation and have a well-known genetic basis. Question: Do different predator regimes induce different selective pressures on growth rates and defence phenotypes in threespine stickleback between different habitats across distinct age classes? Hypothesis: In the presence of predation-induced selection, we expect diverging morphological responses between populations experiencing either low or high predation pressure. Study system: Threespine stickleback were sampled from two natural but recently established populations in an invasive range. One site has a high density of fish and insect predators, while at the other site predation pressure is low. Methods: We inferred predator-induced selection on defence traits by comparing the distribution of size classes, defence phenotypes, and an armour-related genotype between different age classes in a high and a low predation regime. Results: Under high predation, there are indications of directional selection for faster growth, whereas lateral plate phenotypes and associated genotypes show indications for disruptive selection. Heterozygotes at the Eda-gene have a lower survival rate than either homozygote. Neither pattern is evident in the low predation regime. Conclusion: Potential evolutionary responses to divergent predation pressures between sites are apparent in a recently established system

Algorithmic Debugging of Real-World Haskell Programs: Deriving Dependencies from the Cost Centre Stack

Existing algorithmic debuggers for Haskell require a transformation of all modules in a program, even libraries that the user does not want to debug and which may use language features not supported by the debugger. This is a pity, because a promising ap- proach to debugging is therefore not applicable to many real-world programs. We use the cost centre stack from the Glasgow Haskell Compiler profiling environment together with runtime value observations as provided by the Haskell Object Observation Debugger (HOOD) to collect enough information for algorithmic debugging. Program annotations are in suspected modules only. With this technique algorithmic debugging is applicable to a much larger set of Haskell programs. This demonstrates that for functional languages in general a simple stack trace extension is useful to support tasks such as profiling and debugging

Accurate evaluation of the interstitial KKR-Green function

It is shown that the Brillouin zone integral for the interstitial KKR-Green function can be evaluated accurately by taking proper care of the free-electron singularities in the integrand. The proposed method combines two recently developed methods, a supermatrix method and a subtraction method. This combination appears to provide a major improvement compared with an earlier proposal based on the subtraction method only. By this the barrier preventing the study of important interstitial-like defects, such as an electromigrating atom halfway along its jump path, can be considered as being razed.Comment: 23 pages, RevTe

Nuclear Physics with Electroweak Probes

In recent years, the italian theoretical Nuclear Physics community has played a leading role in the development of a unified approach, allowing for a consistent and fully quantitative description of the nuclear response to electromagnetic and weak probes. In this paper I review the main achievements in both fields, point out some of the open problems, and outline the most promising prospects.Comment: Invited Talk at the XII Workshop on Theoretical Nuclear Physics in Italy, Cortona, October 8-10, 200