A sociocultural analysis of the development of pre-service and beginning teachers’ pedagogical identities as users of technology

This paper reports on a study that investigated the pedagogical practices and beliefs of pre-service and beginning teachers in integrating technology into the teaching of secondary school mathematics. A case study documents how one teachers modes of working with technology changed over time and across different school contexts, and identifies relationships between a range of personal and contextual factors that influenced the development of his identity as a teacher. This analysis views teachers learning as increasing participation in sociocultural practices, and uses Valsiners concepts of the Zone of Proximal Development, Zone of Free Movement, and Zone of Promoted Action to offer a dynamic way of theorising teacher learning as identity formation

The energy spectrum of cosmic rays beyond the turn-down around 10^17 eV as measured with the surface detector of the Pierre Auger Observatory

We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays

A Mechanically Verified Compiling Specification for a Lisp Compiler

We report on an ongoing effort in mechanically proving correct a compiling specification for a bootstrap compiler from ComLisp (a subset of ANSI Common Lisp suciently expressive to serve as a compiler implementation language) to binary Transputer code using the PVS system. The compilation is carried out in four steps through a series of intermediate languages. This paper focuses on the first phase, namely, the compilation of ComLisp to the stack-intermediate language SIL, where parameter passing is implemented by a stack technique. The context of this work is the joint research effort Verifix aiming at developing methods for the construction of correct compilers for realistic programming languages