Surface study of the (100) and (010) faces of the quasicrystalapproximant Al4(Cr, Fe)

Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) results are used to study the pseudo-6-fold nature of the (100) surface of the orthorhombic quasicrystal approximant Al4(Cr, Fe). LEED patterns are also presented from the pseudo-10-fold (010) surface of this material. In each case the results are compared with the known bulk structure of this complex metallic alloy

Politics meets Science: The case of neonicotinoid insecticides in Europe

In April 2013, based on reviews by the European Food Safety Authority (EFSA), the European Commission announced a two-year ban on the use of three insecticides in the neonicotinoid group on certain flowering crops, as well as on certain crops that are not attractive to bees at certain times of the year. Although there was strong lobbying against the proposed ban by the multinational chemical companies that produce the insecticides, along with farmer’s groups, strong lobbying in support of the ban came from environmental groups, beekeeping organizations and the general public. Even after two rounds of voting, the European parliament did not reach a consensus, forcing the European Commission to exercise its rights and impose the ban – based especially on the evidence presented in a review of relevant scientific data produced by the European Union’s own European Food Safety Authority. Various reports suggest that, on the one hand, some European governments were persuaded to support the position of the multinational chemical companies rather than be persuaded by the review of research data, while on the other hand, environmental groups over-played the risks posed by the insecticides in question and the potential benefits of the proposed ban. This case study report briefly reviews the background data on recent reported declines in bee populations; cites some of the evidence put forward by EFSA and others in support of and against the ban; reports on the process of the legislation as it proceeded through the European parliament as well as the lobbying that went on during the votes, including an analysis of the roles of key players and commentators; and proposes a way forward to resolve the apparent dichotomy between the pesticide producers and those who support the ban

The implementation of a LAN

Includes bibliography.The subject of this thesis concerns the development of a Local Area Network (LAN) for the Department of Electrical and Electronic Engineering at the University of Cape Town. Motivation for this project was as a result of the ever increasing demands placed on the department's micro-computer training facilities by larger student intakes. The original training system consisted of a PDP 11/23 mini-computer connected via 9600 baud asynchronous links to 11 U.C.T. built micro-computers. This network topology was limiting in three ways: 1. It was slow because of the 9600 baud links and because the PDP was doing a large proportion of the processing.2. High-leve 1 software development tools for the PDP were too expensive and would over-load the computer. Because the micro-computers have no operating system but only an "in-house" monitor program which is not able to support any high-level language utility, all high-level software tools would have to be individually developed for this particular environment. 3. Switching was impractical. Because the PDP was the hub of the network all communication between computers had. to pass through it. This switching would lead to a greater processing load on the PDP, thus further degrading its performance. A two pronged attack was used to overcome these weaknesses: firstly, by designing a high-speed (1 Mbps) LAN to provide communications between a PDP 11/23 and up to 30 U.C.T. built micro-computers, faster inter-computer communication as well as switching and resource sharing was facilitated. Secondly, by customizing an operating system for the micro-computers, standard high-level software development tools could be used on these computers, consequently reducing the PDP's processing load