Saltation thresholds and entrainment of fine particles at Earth and Martian pressures

An open circuit wind tunnel designed to operate in a large vacuum chamber was built at NASA-Ames to investigate saltation threshold, flux, deflation rates, and other aeolian phenomena on the planet Mars. The vacuum chamber will operate at pressures as low as 4 mbar, and the tunnel operates at windspeeds as high as 150 m/sec. Either air or CO2 can be used as a working fluid. It was found that, to a first order approximation, the same dynamic pressure was required at Martian pressure to entrain or saltate particles as was required on Earth, although wind and particle speed are considerably higher at Martian pressure. A 2nd wind tunnel, designed to operate aboard the NASA KC-135 0-g aircraft to obtain information on the effect of gravity on saltation threshold and the interparticle force at 0-g, is also described and test data presented. Some of the experiments are summarized and various aspects of low pressure aeolian entrainment for particles 12 to 100 micron in diameter are discussed, some of them unique to low pressure testing and some common in Earth pressure particle transport testing. The facility, the modes of operation, and the materials used are described

The correct understanding of the Business Judgment Rule in Section 76(4) of the Companies Act 71 of 2008: avoiding the American mistakes

Includes bibliographical references.The South African law concerning directors' duties is intricate under both the common law and the Companies Act. This is an area of corporate law which allows for a wealth of practical and theoretical difficulty. I aim to deconstruct the intricacy of the American experience of the business judgment rule, with particular reference to the rule in Delaware, so as to present what I perceive to be the correct practical application of the rule in South African corporate law. This dissertation does not address the wisdom of the decision to transplant and codify the American business judgment rule within the Companies Act

American Education Reform and the Humanism of Mathematics, 1890-1940

In the early 20th century, mathematicians and math teachers became interested in the connections between mathematics and areas of humanistic interest such as philosophy, aesthetics, music, and especially history. This thesis narrates how this interest came about and explains mathematics educators\u27 motivation and understanding of mathematics as a humanistic discipline. Math educators reacted to an attack on their subject from progressive educators who argued that math education was inefficient or useless to children. In response, math educators stressed the cultural value of the subject, portraying it as an important part of human culture and an essential subject in the school curriculum

'MMR talk' and vaccination choices: an ethnographic study in Brighton

In the context of the high-profile controversy that has unfolded in the UK around the measles, mumps and rubella (MMR) vaccine and its possible adverse effects, this paper explores how parents in Brighton, southern England, are thinking about MMR for their own children. Research focusing on parents’ engagement with MMR has been dominated by analysis of the proximate influences on their choices, and in particular scientific and media information, which have led health policy to focus on information and education campaigns. This paper reports ethnographic work including narratives by mothers in Brighton.Our work questions such reasoning in showing how wider personal and social issues shape parents’ immunisation actions. The narratives by mothers show how practices around MMR are shaped by personal histories, by birth experiences and related feelings of control, by family health histories, by their readings of their child’s health and particular strengths and vulnerabilities, by particular engagements with health services,by processes building or undermining confidence,and by friendships and conversations with others,which are themselves shaped by wider social differences and transformations. Although many see vaccination as a personal decision which must respond to the particularities of a child’s immune system, ‘MMR talk’, which affirms these conceptualisations, has become a social phenomenon in itself. These perspectives suggest ways in which people’s engagements with MMR reflect wider changes in their relations with science and the state

Design and implementation of a local area network utilizing Intel 310/80286 systems

The goal of this work was to provide the foundation for a course in networking by developing the hardware and software for a token ring Local Area Network (LAN). Any course work in networking would focus on the emerging International Standards Organization (ISO) Open Systems Interconnections (OSI) model. This model provides a seven layered structure, where each layer performs some logical aspect of the communication process. Thus, the software developed would have to provide the functionality of a multiple layered design, implying multiple tasks communicating by operating system primitives. Also, a simplified design would minimize the time for those students trying to assimilate the basic work prior to embarking on the design of their own work. Within an Intel 310 system running the iRMX operating system, the LAN hardware and software were developed. The package allows reliable transfer of files to the other nodes on a token ring LAN via access by user programs to lower layers. In addition, the user has a reasonable interface to interact with the file system of the home node. Once the physical configuration of the LAN is established, the software is self-initializing and self monitoring for pathological cases. The software runs as an application task on each node, thus maintaining each Intel 310 as a general purpose development environment