Precision calculation of energy levels for four-valent Si I

We report results of the calculation of the low-lying levels of neutral Si using a combination of the configuration interaction and many-body perturbation theory (CI+MBPT method). We treat Si I as an atom with four valence electrons and use two different starting approximations, namely $V^{N-2}$ and $V^{N-4}$. We conclude that both approximations provide comparable accuracy, on the level of 1%

Hemiparasitic plant impacts animal and plant communities across four trophic levels

1.Understanding the impact of species on community structure is a fundamental question in ecology. There is a growing body of evidence that suggests that both sub-dominant species and parasites can have a disproportionately large impact. 2.Here we report the impacts of an organism that is both subdominant and parasitic, the hemiparasite Rhinanthus minor. Whilst the impact of parasitic angiosperms on their hosts and, to a lesser degree, co-existing plant species, have been well characterized, much less is known about their impacts on higher trophic levels. 3.We experimentally manipulated field densities of the hemiparasite Rhinanthus minor in a species rich grassland, comparing the plant and invertebrate communities in plots where it was removed, at natural densities or at enhanced densities. 4.Plots with natural and enhanced densities of R. minor had lower plant biomass than plots without the hemiparasite, but enhanced densities almost doubled the abundance of invertebrates within the plots across all trophic levels, with effects evident in herbivores, predators and detritivores. 5.The hemiparasite R. minor, despite being a sub-dominant and transient component within plant communities that it inhabits, has profound effects on four different trophic levels. These effects persist beyond the life of the hemiparasite, emphasizing its role as a keystone species in grassland communitie

A comparison of rail liberalisation levels across four European countries

The paper presents the results of a research on railway regulation and liberalisation in Italy, France, Germany and Spain. The analysed fields of regulation are the relationship between the State and the rail companies, network access conditions by operators, slot allocating and pricing schemes and how public service obligations are defined, paid and regulated. The aim of the paper is to give a comparative overview of the rail regulation from a critical point of view, rather than descriptive. The regulatory frameworks are outlined and then assessed according to their implications on the liberalisation level and on the effective market opening. The conclusions are that the actual level of liberalisation is still scarce and only in some cases the opening level is increasing. Market penetration of newcomers is significant only in niche markets. An issue emerging from the work is the opposing attitude of incumbent railways against liberalisation and the role of decision makers in backing this behaviour. The strategies followed to limit the outcomes of the liberalisation process are different across the country sample. However, all the incumbents argue with the self-referential declaration of efficiency, public service obligations and they claim to be under an excessive and unfair foreign competition. These arguments are yet embedded in legislative, organisational and economic settings supporting these positions like the common ownership of network and services, the permanence of dominant positions and favourable financial conditions.railways; liberalisation; regulation; Europe; Italy; France, Germany; Spain

Multi-ancestry study of blood lipid levels identifies four loci interacting with physical activity.

Many genetic loci affect circulating lipid levels, but it remains unknown whether lifestyle factors, such as physical activity, modify these genetic effects. To identify lipid loci interacting with physical activity, we performed genome-wide analyses of circulating HDL cholesterol, LDL cholesterol, and triglyceride levels in up to 120,979 individuals of European, African, Asian, Hispanic, and Brazilian ancestry, with follow-up of suggestive associations in an additional 131,012 individuals. We find four loci, in/near CLASP1, LHX1, SNTA1, and CNTNAP2, that are associated with circulating lipid levels through interaction with physical activity; higher levels of physical activity enhance the HDL cholesterol-increasing effects of the CLASP1, LHX1, and SNTA1 loci and attenuate the LDL cholesterol-increasing effect of the CNTNAP2 locus. The CLASP1, LHX1, and SNTA1 regions harbor genes linked to muscle function and lipid metabolism. Our results elucidate the role of physical activity interactions in the genetic contribution to blood lipid levels

Leveling the Field: Talking Levels in Cognitive Science

Talk of levels is everywhere in cognitive science. Whether it is in terms of adjudicating longstanding debates or motivating foundational concepts, one cannot go far without hearing about the need to talk at different ‘levels’. Yet in spite of its widespread application and use, the concept of levels has received little sustained attention within cognitive science. This paper provides an analysis of the various ways the notion of levels has been deployed within cognitive science. The paper begins by introducing and motivating discussion via four representative accounts of levels. It then turns to outlining and relating the four accounts using two dimensions of comparison. The result is the creation of a conceptual framework that maps the logical space of levels talk, which offers an important step toward making sense of levels talk within cognitive science

Effects of Nitrogen Fertilization on Monoterpenes of Jack Pine Seedlings and Weight Gain of Jack Pine Budworm (Lepidoptera: Tortricidae)

Nine-month old jack pine (Pinus banksiana) seedlings were grown in a greenhouse under four nitrogen fertilization regimes. Levels of total nitrogen and five monoterpenes in new foliage were measured. Fertilization resulted in four significantly different levels of foliar nitrogen; means ranged from 1.8-4.5 percent dry weight. Contrary to predictions of resource availability theory, seedlings grown under the highest fertilization regime had higher foliar monoterpene levels than seedlings in the other treatments. Newly molted, sixth-instar female jack pine budworm (Choristoneura pinus pinus [Lepidoptera: Tortricidae]) larvae were allowed to feed for four days on new foliage of the seedlings. Larvae that fed on low-nitrogen seedling gained less weight and process more vegetation than did larvae on high- nitrogen seedlings. Larval weight gain was positively related to foliar nitrogen