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Potchefstroom, South Africa

The North-West University is a newly merged institution from 1 January 2004 onwards with three campuses at Potchefstroom, Mahikeng and Vanderbijlpark, South Africa. The Potchefstroom Campus is the largest, and the head office of the University is situated at this location. With its merged status, the North-West University became one of the largest universities in South Africa and has 64 081 students .The universities that merged to form this institution are the Potchefstroom University for Christian Higher Education and the University of North-West . These two campuses form the main hubs of the university, with the Potchefstroom campus catering to Afrikaans speakers and the Mahikeng campus being broader in orientation. Wikipedia.

Babalola O.O.,North West University South Africa
Biotechnology Letters | Year: 2010

The rhizosphere is the soil-plant root interphase and in practice consists of the soil adhering to the root besides the loose soil surrounding it. Plant growth-promoting rhizobacteria (PGPR) are potential agents for the biological control of plant pathogens. A biocontrol strain should be able to protect the host plant from pathogens and fulfill the requirement for strong colonization. Numerous compounds that are toxic to pathogens, such as HCN, phenazines, pyrrolnitrin, and pyoluteorin as well as, other enzymes, antibiotics, metabolites and phytohormones are the means by which PGPR act, just as quorum sensing and chemotaxis which are vital for rhizosphere competence and colonization. The presence of root exudates has a pronounced effect on the rhizosphere where they serve as an energy source, promoting growth and influencing the root system for the rhizobacteria. In certain instances they have products that inhibit the growth of soil-borne pathogens to the advantage of the plant root. A major source of concern is reproducibility in the field due to the complex interaction between the plant (plant species), microbe and the environment (soil fertility and moisture, day length, light intensity, length of growing season, and temperature). This review listed most of the documented PGPR genera and discussed their exploitation. © 2010 Springer Science+Business Media B.V. Source

Burger R.A.,North West University South Africa
Astrophysical Journal | Year: 2012

Drift along the wavy heliospheric neutral sheet is believed to play an important role in cosmic-ray modulation and can explain the peaked versus flat intensity profiles during consecutive solar magnetic epochs. Modulation models are becoming more and more realistic and in order to determine the role of the wavy neutral sheet more accurately, we revisit a previous calculation for drift along it. While mathematically correct, we argue that the previous expression for neutral sheet drift, which follows naturally from the standard expression for gradient and curvature drift, must be adapted in order for the drift speed to be less than particle speed. We compare the effect of both the previous and the current more accurate version of neutral sheet drift on cosmic-ray modulation with results obtained by other methods. © 2012. The American Astronomical Society. All rights reserved. Source

Potgieter M.S.,North West University South Africa
Living Reviews in Solar Physics | Year: 2013

This is an overview of the solar modulation of cosmic rays in the heliosphere. It is a broad topic with numerous intriguing aspects so that a research framework has to be chosen to concentrate on. The review focuses on the basic paradigms and departure points without presenting advanced theoretical or observational details for which there exists a large number of comprehensive reviews. Instead, emphasis is placed on numerical modeling which has played an increasingly significant role as computational resources have become more abundant. A main theme is the progress that has been made over the years. The emphasis is on the global features of CR modulation and on the causes of the observed 11-year and 22-year cycles and charge-sign dependent modulation. Illustrative examples of some of the theoretical and observational milestones are presented, without attempting to review all details or every contribution made in this field of research. Controversial aspects are discussed where appropriate, with accompanying challenges and future prospects. The year 2012 was the centennial celebration of the discovery of cosmic rays so that several general reviews were dedicated to historical aspects so that such developments are briefly presented only in a few cases. Source

Loots D.T.,North West University South Africa
Antimicrobial Agents and Chemotherapy | Year: 2014

The most common form of drug resistance found in tuberculosis (TB)-positive clinical samples is monoresistance to isoniazid. Various genomics and proteomics studies to date have investigated this phenomenon; however, the exact mechanisms relating to how this occurs, as well as the implications of this on the TB-causing organisms function and structure, are only partly understood. Considering this, we followed a metabolomics research approach to identify potential new metabolic pathways and metabolite markers, which when interpreted in context would give a holistic explanation for many of the phenotypic characteristics associated with a katG mutation and the resulting isoniazid resistance in Mycobacterium tuberculosis. In order to achieve these objectives, gas chromatography-time of flight mass spectrometry (GCxGC-TOFMS)-generated metabolite profiles from two iso-niazid- resistant strains were compared to a wild-type parent strain. Principal component analyses showed clear differentiation between the groups, and the metabolites best describing the separation between these groups were identified. It is clear from the data that due to a mutation in the katG gene encoding catalase, the isoniazid-resistant strains experience increased susceptibility to oxidative stress and have consequently adapted to this by upregulating the synthesis of a number of compounds involved in (i) increased uptake and use of alkanes and fatty acids as a source of carbon and energy and (ii) the synthesis of a number of compounds directly involved in reducing oxidative stress, including an ascorbic acid degradation pathway, which to date hasn't been proposed to exist in these organisms. Copyright © 2014 American Society for Microbiology. All Rights Reserved. Source

Potgieter M.S.,North West University South Africa
Space Science Reviews | Year: 2013

The global modulation of galactic cosmic rays in the inner heliosphere is determined by four major mechanisms: convection, diffusion, particle drifts (gradient, curvature and current sheet drifts), and adiabatic energy losses. When these processes combine to produce modulation, the complexity increases significantly especially when one wants to describe how they evolve spatially in all three dimensions throughout the heliosphere, and with time, as a function of solar activity over at least 22 years. In this context also the global structure and features of the solar wind, the heliospheric magnetic field, the wavy current sheet, and of the heliosphere and its interface with the interstellar medium, play important roles. Space missions have contributed significantly to our knowledge during the past decade. In the inner heliosphere, Ulysses and several other missions have contributed to establish the relative importance of these major mechanisms, leading to renewed interest in developing more sophisticated theories and numerical models to explain these observations, and to understand the underlying physics that determines galactic cosmic ray modulation at Earth. An overview is given of some of the observational and modeling highlights over the past decade. © 2011 Springer Science+Business Media B.V. Source

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