The social constitution of Information Technology policies in developing countries

The role of information, communication and knowledge in shaping socio-economic development has become a top concern for African countries. Information technology, however, does not only impose change on industry and market structures, but also changes the political and social structures of a country. Therefore, the development of information technology policies cannot ignore the practices of social agents within society. The user of the information and the information technology cannot be eliminated from the equation. If this is the case, the social agent becomes irrelevant. Current initiatives, however, with regard to the implementation of new information technologies in Africa, are mainly guided by techno-economical aspects, while the target group’s socio-cultural context is hardly taken into account. This result in inappropriate technology, ignorance of the African user and a reinforcement of western elitism. It is the aim of this research to investigate IT policies within developing countries and to suggest a framework for the social constitution of such policies

Analysis of shot noise suppression in mesoscopic cavities in a magnetic field

We present a numerical investigation of shot noise suppression in mesoscopic cavities and an intuitive semiclassical explanation of the behavior observed in the presence of an orthogonal magnetic field. In particular, we conclude that the decrease of shot noise for increasing magnetic field is the result of the interplay between the diameter of classical cyclotron orbits and the width of the apertures defining the cavity. Good agreement with published experimental results is obtained, without the need of introducing fitting parameters.Comment: 5 pages, 3 figures, contents changed (final version

Positive Cross Correlations in a Normal-Conducting Fermionic Beam Splitter

We investigate a beam splitter experiment implemented in a normal conducting fermionic electron gas in the quantum Hall regime. The cross-correlations between the current fluctuations in the two exit leads of the three terminal device are found to be negative, zero or even positive depending on the scattering mechanism within the device. Reversal of the cross-correlations sign occurs due to interaction between different edge-states and does not reflect the statistics of the fermionic particles which `antibunch'.Comment: 4 pages, 4 figure

Dynamic generation of orbital quasiparticle entanglement in mesoscopic conductors

We propose a scheme for dynamically creating orbitally entangled electron-hole pairs through a time-dependent variation of the electrical potential in a mesoscopic conductor. The time-dependent potential generates a superposition of electron-hole pairs in two different orbital regions of the conductor, a Mach-Zehnder interferometer in the quantum Hall regime. The orbital entanglement is detected via violation of a Bell inequality, formulated in terms of zero-frequency current noise. Adiabatic cycling of the potential, both in the weak and strong amplitude limit, is considered.Comment: 4 pages, 2 figures; references update

Full counting statistics of chaotic cavities with many open channels

Explicit formulas are obtained for all moments and for all cumulants of the electric current through a quantum chaotic cavity attached to two ideal leads, thus providing the full counting statistics for this type of system. The approach is based on random matrix theory, and is valid in the limit when both leads have many open channels. For an arbitrary number of open channels we present the third cumulant and an example of non-linear statistics.Comment: 4 pages, no figures; v2-added references; typos correcte

Influence of Five Cutting Frequencies on the Production of Medicago sativa Cultivars in the Boland of South Africa

The use of fixed interval cutting management for lucerne was studied for four cultivars (CUF101, Condor, SA Standard and Alfagraze) of four dormancy classes. Five fixed cutting intervals ranging from two to ten weeks were imposed for three years on irrigated stands at Elsenburg Research Station in the Boland of South Africa. The experimental design was a 4 by 5 split-plot randomised block with three replications. The four main plots were four cultivars split into five subplots containing five cutting treatments. The more winter dormant cultivar, Alfagraze, was least sensitive to cutting frequency and relatively more productive than the other three cultivars at the two- and six-week cutting regime. There was no evidence that cultivars of different dormancy classes require different cutting management to obtain maximum annual dry matter yield. Therefore, a fixed cutting frequency of six weeks throughout the year is an acceptable management compromise for all lucerne grown in the Boland region of the Western Cape

Semiclassical structure of chaotic resonance eigenfunctions

We study the resonance (or Gamow) eigenstates of open chaotic systems in the semiclassical limit, distinguishing between left and right eigenstates of the non-unitary quantum propagator, and also between short-lived and long-lived states. The long-lived left (right) eigenstates are shown to concentrate as $\hbar\to 0$ on the forward (backward) trapped set of the classical dynamics. The limit of a sequence of eigenstates $\{\psi(\hbar)\}_{\hbar\to 0}$ is found to exhibit a remarkably rich structure in phase space that depends on the corresponding limiting decay rate. These results are illustrated for the open baker map, for which the probability density in position space is observed to have self-similarity properties.Comment: 4 pages, 4 figures; some minor corrections, some changes in presentatio

Shot noise of series quantum point contacts intercalating chaotic cavities

Shot noise of series quantum point contacts forming a sequence of cavities in a two dimensional electron gas are studied theoretically and experimentally. Noise in such a structure originates from local scattering at the point contacts as well as from chaotic motion of the electrons in the cavities. We found that the measured shot noise is in reasonable agreement with our theoretical prediction taking the cavity noise into account.Comment: 4 pages, 5 figure