9 research outputs found
The Modified Weighted Slab Technique: Models and Results
In an attempt to understand the source and propagation of galactic cosmic
rays we have employed the Modified Weighted Slab technique along with recent
values of the relevant cross sections to compute primary to secondary ratios
including B/C and Sub-Fe/Fe for different galactic propagation models. The
models that we have considered are the disk-halo diffusion model, the dynamical
halo wind model, the turbulent diffusion model and a model with minimal
reacceleration. The modified weighted slab technique will be briefly discussed
and a more detailed description of the models will be given. We will also
discuss the impact that the various models have on the problem of anisotropy at
high energy and discuss what properties of a particular model bear on this
issue.Comment: LaTeX - AASTEX format, Submitted to ApJ, 8 figures, 20 page
Secondary antiprotons and propagation of cosmic rays in the Galaxy and heliosphere
High-energy collisions of cosmic-ray nuclei with interstellar gas are
believed to be the mechanism producing the majority of cosmic ray antiprotons.
Due to the kinematics of the process they are created with a nonzero momentum;
the characteristic spectral shape with a maximum at ~2 GeV and a sharp decrease
towards lower energies makes antiprotons a unique probe of models for particle
propagation in the Galaxy and modulation in the heliosphere. On the other hand,
accurate calculation of the secondary antiproton flux provides a ``background''
for searches for exotic signals from the annihilation of supersymmetric
particles and primordial black hole evaporation. Recently new data with large
statistics on both low and high energy antiproton fluxes have become available
which allow such tests to be performed. We use our propagation code GALPROP to
calculate interstellar cosmic-ray propagation for a variety of models. We show
that there is no simple model capable of accurately describing the whole
variety of data: boron/carbon and sub-iron/iron ratios, spectra of protons,
helium, antiprotons, positrons, electrons, and diffuse gamma rays. We find that
only a model with a break in the diffusion coefficient plus convection can
reproduce measurements of cosmic-ray species, and the reproduction of primaries
(p, He) can be further improved by introducing a break in the primary injection
spectra. For our best-fit model we make predictions of proton and antiproton
fluxes near the Earth for different modulation levels and magnetic polarity
using a steady-state drift model of propagation in the heliosphere.Comment: Many Updates, 20 pages, 15 ps-figures, emulateapj5.sty. To be
published in ApJ v.564 January 10, 2002 issue. More details can be found at
http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm
A portal of educational resources: providing evidence for matching pedagogy with technology
The TPACK (Technology, Pedagogy and Content Knowledge) model presents the three types of knowledge that are necessary to implement a successful technology-based educational activity. It highlights how the intersections between TPK (Technological Pedagogical Knowledge), PCK (Pedagogical Content Knowledge) and TCK (Technological Content Knowledge) are not a sheer sum up of their components but new types of knowledge. This paper focuses on TPK, the intersection between technology knowledge and pedagogy knowledge â a crucial field of investigation. Actually, technology in education is not just an add-on but is literally reshaping teaching/learning paradigms. Technology modifies pedagogy and pedagogy dictates requirements to technology. In order to pursue this research, an empirical approach was taken, building a repository (back-end) and a portal (front-end) of about 300 real-life educational experiences run at school. Educational portals are not new, but they generally emphasise content. Instead, in our portal, technology and pedagogy take centre stage. Experiences are classified according to more than 30 categories (âfacetsâ) and more than 200 facet values, all revolving around the pedagogical implementation and the technology used. The portal (an innovative piece of technology) supports sophisticated âexploratoryâ sessions of use, targeted at researchers (investigating the TPK intersection), teachers (looking for inspiration in their daily jobs) and decision makers (making decisions about the introduction of technology into schools)