353 research outputs found
The role of the school in inculcating citizenship values in South Africa: theoretical and international comparative perspectives
In view of the serious moral decay in South African society, this article reports on our research regarding the role of the school in the inculcation of citizenship values (as part of the brief of South African education). We regard a set of citizenship values consonant with a democratic dispensation to be a core component of a moral order essential for South Africa. Using a combination of interpretive-constructivist and comparative approaches, we examine and evaluate the experiences of other post-conflict societies in using education to inculcate citizenship values. We conclude that schools can be successful with respect to the inculcation of citizenship values, provided that the curriculum itself does not discriminate against any group or category of people. Desegregation can only be beneficial in the absence of negative depiction (including criminalisation) or the unequal treatment of any particular societal grouping. Our research suggests that active citizenship education is needed in schools. For this reason, we contend that teacher education has to form an integral part of a moral revival project. Lastly, we highlight the importance of finding democratically agreed-upon ways to continually engage with parents, legal caregivers and other stakeholders and role-players before and during the execution of any such project
Time dependence of the proton flux measured by PAMELA during the July 2006 - December 2009 solar minimum
The energy spectra of galactic cosmic rays carry fundamental information
regarding their origin and propagation. These spectra, when measured near
Earth, are significantly affected by the solar magnetic field. A comprehensive
description of the cosmic radiation must therefore include the transport and
modulation of cosmic rays inside the heliosphere. During the end of the last
decade the Sun underwent a peculiarly long quiet phase well suited to study
modulation processes. In this paper we present proton spectra measured from
July 2006 to December 2009 by PAMELA. The large collected statistics of protons
allowed the time variation to be followed on a nearly monthly basis down to 400
MV. Data are compared with a state-of-the-art three-dimensional model of solar
modulation.Comment: 17 pages, 5 figures, 1 table, to appear in Astrophysical Journal.
Corrected two elements of Table
Time dependence of the e^- flux measured by PAMELA during the July 2006 - December 2009 solar minimum
Precision measurements of the electron component in the cosmic radiation
provide important information about the origin and propagation of cosmic rays
in the Galaxy not accessible from the study of the cosmic-ray nuclear
components due to their differing diffusion and energy-loss processes. However,
when measured near Earth, the effects of propagation and modulation of galactic
cosmic rays in the heliosphere, particularly significant for energies up to at
least 30 GeV, must be properly taken into account. In this paper the electron
(e^-) spectra measured by PAMELA down to 70 MeV from July 2006 to December 2009
over six-months time intervals are presented. Fluxes are compared with a
state-of-the-art three-dimensional model of solar modulation that reproduces
the observations remarkably well.Comment: 40 pages, 18 figures, 1 tabl
Time dependence of the electron and positron components of the cosmic radiation measured by the PAMELA experiment between July 2006 and December 2015
Cosmic-ray electrons and positrons are a unique probe of the propagation of
cosmic rays as well as of the nature and distribution of particle sources in
our Galaxy. Recent measurements of these particles are challenging our basic
understanding of the mechanisms of production, acceleration and propagation of
cosmic rays. Particularly striking are the differences between the low energy
results collected by the space-borne PAMELA and AMS-02 experiments and older
measurements pointing to sign-charge dependence of the solar modulation of
cosmic-ray spectra. The PAMELA experiment has been measuring the time variation
of the positron and electron intensity at Earth from July 2006 to December 2015
covering the period for the minimum of solar cycle 23 (2006-2009) till the
middle of the maximum of solar cycle 24, through the polarity reversal of the
heliospheric magnetic field which took place between 2013 and 2014. The
positron to electron ratio measured in this time period clearly shows a
sign-charge dependence of the solar modulation introduced by particle drifts.
These results provide the first clear and continuous observation of how drift
effects on solar modulation have unfolded with time from solar minimum to solar
maximum and their dependence on the particle rigidity and the cyclic polarity
of the solar magnetic field.Comment: 11 pages, 2 figure
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
Ultra-High Energy Neutrino Fluxes: New Constraints and Implications
We apply new upper limits on neutrino fluxes and the diffuse extragalactic
component of the GeV gamma-ray flux to various scenarios for ultra high energy
cosmic rays and neutrinos. As a result we find that extra-galactic top-down
sources can not contribute significantly to the observed flux of highest energy
cosmic rays. The Z-burst mechanism where ultra-high energy neutrinos produce
cosmic rays via interactions with relic neutrinos is practically ruled out if
cosmological limits on neutrino mass and clustering apply.Comment: 10 revtex pages, 9 postscript figure
TB Hackathon: Development and Comparison of Five Models to Predict Subnational Tuberculosis Prevalence in Pakistan
Pakistan’s national tuberculosis control programme (NTP) is among the many programmes worldwide that value the importance of subnational tuberculosis (TB) burden estimates to support disease control efforts, but do not have reliable estimates. A hackathon was thus organised to solicit the development and comparison of several models for small area estimation of TB. The TB hackathon was launched in April 2019. Participating teams were requested to produce district-level estimates of bacteriologically positive TB prevalence among adults (over 15 years of age) for 2018. The NTP provided case-based data from their 2010–2011 TB prevalence survey, along with data relating to TB screening, testing and treatment for the period between 2010–2011 and 2018. Five teams submitted district-level TB prevalence estimates, methodological details and programming code. Although the geographical distribution of TB prevalence varied considerably across models, we identified several districts with consistently low notification-to-prevalence ratios. The hackathon highlighted the challenges of generating granular spatiotemporal TB prevalence forecasts based on a cross-sectional prevalence survey data and other data sources. Nevertheless, it provided a range of approaches to subnational disease modelling. The NTP’s use and plans for these outputs shows that, limitations notwithstanding, they can be valuable for programme planning
Launch of the Space experiment PAMELA
PAMELA is a satellite borne experiment designed to study with great accuracy
cosmic rays of galactic, solar, and trapped nature in a wide energy range
protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study
of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50
MeV-270 GeV) and search for antimatter with a precision of the order of 10^-8).
The experiment, housed on board the Russian Resurs-DK1 satellite, was launched
on June, 15, 2006 in a 350*600 km orbit with an inclination of 70 degrees. The
detector is composed of a series of scintillator counters arranged at the
extremities of a permanent magnet spectrometer to provide charge,
Time-of-Flight and rigidity information. Lepton/hadron identification is
performed by a Silicon-Tungsten calorimeter and a Neutron detector placed at
the bottom of the device. An Anticounter system is used offline to reject false
triggers coming from the satellite. In self-trigger mode the Calorimeter, the
neutron detector and a shower tail catcher are capable of an independent
measure of the lepton component up to 2 TeV. In this work we describe the
experiment, its scientific objectives and the performance in the first months
after launch.Comment: Accepted for publication on Advances in Space Researc
The Interstellar Environment of our Galaxy
We review the current knowledge and understanding of the interstellar medium
of our galaxy. We first present each of the three basic constituents - ordinary
matter, cosmic rays, and magnetic fields - of the interstellar medium, laying
emphasis on their physical and chemical properties inferred from a broad range
of observations. We then position the different interstellar constituents, both
with respect to each other and with respect to stars, within the general
galactic ecosystem.Comment: 39 pages, 12 figures (including 3 figures in 2 parts
Competition and Vertical/Agglomeration Effects in Media Mergers: Bagging Bundle Benefits
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