A Weyl-Dirac Cosmological Model with DM and DE

In the Weyl-Dirac (W-D) framework a spatially closed cosmological model is considered. It is assumed that the space-time of the universe has a chaotic Weylian microstructure but is described on a large scale by Riemannian geometry. Locally fields of the Weyl connection vector act as creators of massive bosons having spin 1. It is suggested that these bosons, called weylons, provide most of the dark matter in the universe. At the beginning the universe is a spherically symmetric geometric entity without matter. Primary matter is created by Dirac's gauge function very close to the beginning. In the early epoch, when the temperature of the universe achieves its maximum, chaotically oriented Weyl vector fields being localized in micro-cells create weylons. In the dust dominated period Dirac's gauge function is giving rise to dark energy, the latter causing the cosmic acceleration at present. This oscillatory universe has an initial radius identical to the Plank length = 1.616 exp (-33) cm, at present the cosmic scale factor is 3.21 exp (28) cm, while its maximum value is 8.54 exp (28) cm. All forms of matter are created by geometrically based functions of the W-D theory.Comment: 25 pages. Submitted to GR

Active Galactic Nuclei at the Crossroads of Astrophysics

Over the last five decades, AGN studies have produced a number of spectacular examples of synergies and multifaceted approaches in astrophysics. The field of AGN research now spans the entire spectral range and covers more than twelve orders of magnitude in the spatial and temporal domains. The next generation of astrophysical facilities will open up new possibilities for AGN studies, especially in the areas of high-resolution and high-fidelity imaging and spectroscopy of nuclear regions in the X-ray, optical, and radio bands. These studies will address in detail a number of critical issues in AGN research such as processes in the immediate vicinity of supermassive black holes, physical conditions of broad-line and narrow-line regions, formation and evolution of accretion disks and relativistic outflows, and the connection between nuclear activity and galaxy evolution.Comment: 16 pages, 5 figures; review contribution; "Exploring the Cosmic Frontier: Astrophysical Instruments for the 21st Century", ESO Astrophysical Symposia Serie

Making Sense Through Participation

In this chapter we discuss the issue of social differences in relation to learning. In theories on co-operative learning or collaborative learning social differences are treated as characteristics of individual learners. The focus on learning as a social process is primarily elaborated in terms of interaction between pupils and the combined construction of knowledge. Sociocultural theory (Vygotsky, Lave & Wenger), however, understands ‘social’ not only in terms of knowledge/meaning being constructed in interaction with others, but also in terms of the cultural practices/activities informing these interaction processes. Learning can be understood as increasing participating in communities of practice. As social differences are an intrinsic part of the culture in which students are learning to participate, these are also an inherent aspect of learning processes in schools. Students learn to participate in practices in different ways, depending on their social position, and thus develop distinguished cultural identities. In this chapter we elaborate on this tenet, using examples from various empirical research projects on learning in secondary education. We not only show how social differences in the cultural practices that underpin learning influence what is learned by whom, but also explore the consequences of this perspective for the pedagogical space of the school

Analysis of genomic sequences of 95 papillomavirus types: Uniting typing, phylogeny, and taxonomy

Journal of Virology6953074-3083JOVI