From the editors

The original publication is available at http://scientiamilitaria.journals.ac.za/pubAn editorial written by the editors of Scientia Militaria, South African Journal of Military Studies, a journal published bi-annually by the Faculty of Military Science of Stellenbosch University, South Africa. It is an accredited, peer reviewed scholarly journal, which investigates a broad spectrum of matters and issues relating to military affairs, and publishes both discipline-based and inter-disciplinary research. This particular editorial introduces the content of Volume 40, number 1 (2012).Publisher's versio

Cytotaxonomic studies in Themeda triandra Forsk. Part II. Aneuploidy in a diploid population

Meiosis was studied in 24 plants from a diploid Themeda triandra Forsk. population. This population was found to include a high proportion of aneuploids (33,3%). Amongst these were trisomics (12,5%), tetrasomics (16,67%) and one possible hexasomic. The effect of the aneuploidy on meiosis is described and the possible causes of such a high proportion of aneuploids in a diploid population is discussed

Comparative characterization of P91 and 10CrMo9-10 creep resistant steel welds

Abstract:Abstract: P91 and 10CrMo9-10 creep resistant steels are critical to the performance of boiler tubes and power generating plants in general. Components made from these materials are mainly joined by welding. This paper reports on the comparative study of the effect of TIG and SMAW welding on the mechanical performance of P91 and 10CrMo9-10. TIG was used for root welding while SMAW was used for weld filling of V-butt joints. Specimens of the two alloys prepared using recommended welding procedures are evaluated using optical microscopy and Vickers micro hardness assessment. Some specimens were post weld heat treated while others were not. Post weld heat treated (PWHT) specimens exhibited similar properties as the corresponding base materials for both steels. TIG welding resulted in significant grain size reduction in both steels. PWHT produced more consistent grain structure, which is favorable

Performance Evaluation of Wireless Communication in a Modular Heliostat Field.

Thesis (MEng)--Stellenbosch University, 2021.ENGLISH ABSTRACT: Concentrating Solar Thermal (CST) is differentiated from other renewable energy technologies by the ability to store large amounts of thermal energy cost-effectively. CST, and especially Central Receiver Systems (CRS), still require further develop- ment to drive down the Levelised Cost of Electricity (LCOE) to remain economi- cally competitive in the renewable energy market. Heliostats are used in CRS to reflect sunlight onto a central receiver. Data trans- mission is required between a central server and Local Control Units (LCUs) to enable high precision tracking, over-the-air calibration updates, and swift emer- gency reaction. Wireless communication technologies have shown both capital cost and construction time saving potential for CST plants, but practical performance knowledge of operation in heliostat fields is limited. The purpose of this study is to evaluate the feasibility of wireless communica- tion within a CST field b y m eans o f p ractical t ests a imed t o d etermine t he influ- ence of interference, dense networks, and transmission range on the network per- formance. The project forms part of the H2020 PREMA project, which aims to advance novel energy systems in the drying and pre-heating of furnace manganese ore. A communication network consisting of 50 LCUs, capable of controlling 300 heliostats, was designed and implemented to simulate data transmission in a CST network. Performance experiments were conducted at the Helio100 site to de- termine the effect of various performance limiting factors. Experimental results showed a high performing, robust wireless communication system with a worst- case polling rate of 0.79 s, which satisfies a m ajor r equirement o f t he communi- cation network. The thesis concludes that wireless communication is feasible in a CST field, which could lead to the reduction of capital costs and construction time, reducing the LCOE of CST plants.AFRIKAANSE OPSOMMING: Gekonsentreerde Sonkrag (GSK) word onderskei van ander hernubare energie tegnologieë deur die vermoë om groot hoeveelhede termiese energie koste effektief te stoor. Gekonsentreerde sonkrag, en veral sentrale ontvangersisteme, benodig nog verdere ontwikkeling om die gelykte koste van elektrisiteit te verlaag om ekonomies kompeterend te bly in die hernubare energie mark. Heliostate word in sentrale ontvangersisteme gebruik om sonlig op ’n sentrale ontvanger te weerkaats. Data-oordrag is nodig tussen ’n sentrale bediener en plaas- like beheer eenhede om hoë akkuraatheid volgingsbeweging, oor die lug kalibrasie- opdaterings en vinnige noodreaksie moontlik te maak. Draadlose kommunikasie- tegnologie het die potensiaal vir kapitaal kostebesparings en konstruksie tydbespa- rings vir GSK-aanlegte getoon, maar praktiese kennis oor die netwerk gedrag in heliostaat velde is beperk. Die doel van hierdie studie is om die uitvoerbaarheid van draadlose kommunika- sie binne ’n sentrale ontvangersisteem te evalueer aan die hand van praktiese toetse om die invloed van interferensie, digte netwerke en die transmissie afstand, op die netwerk werking te bepaal. Die projek vorm deel van die H2020 PREMA-projek, wat streef om nuwe energie stelsels te bevorder vir die droog en voorverhitting pro- ses van mangaanerts. ’n Kommunikasienetwerk bestaande uit 50 plaaslike beheer eenhede, wat 300 heliostate kan beheer, is ontwerp en geïmplementeer om data-oordrag in ’n gekon- sentreerde sonkrag netwerk te simuleer. ’n Eksperimentele ondersoek is op die Helio100-terrein gedoen om die effek van verskillende netwerk beperkende faktore te bepaal. Eksperimentele resultate toon ’n hoë prestasie, robuuste draadlose kommuni- kasiestelsel wat, in die slegste geval, die hele netwerk binne 0.79 s kan bedien en so ’n hoofvereiste van die kommunikasie netwerk bevredig. Die tesis het tot die gevolgtrekking gekom dat draadlose kommunikasie binne ’n GSK heliostaat veld uitvoerbaar is en dat dit moontlik tot ’n verlaging in kapitaal koste en konstruksie tyd in sentrale ontvangersisteme kan lei en die gelykte koste van elektrisiteit van gekonsentreerde sonkrag aanlegte kan verminder.Master

Preliminary investigation into the cause of acid mine water induced seismicity in Johannesburg

A preliminary investigation was done into the possible causes of the increased seismic activity in the Witwatersrand Basin. The paper focuses on approximated underground mining areas, groundwater mobility, rock types and the proximity of fault lines to seismic events. These parameters were mapped and correlated with observed seismicity in the area. There is some indication that the presence of underground mining areas has a positive relationship with the occurrence of seismic events. The other parameters exhibit a negative relationship with seismic activity. However, more detailed investigations are required before final conclusions can be drawn. An approach to risk assessment of possible earthquake scenarios in the City of Johannesburg (CoJ) is proposed. The approach aims to assess potential damage to infrastructure and loss of life in the case of an earthquake. The results of such an assessment may provide justification for more detailed investigations

Influence of Apple stem grooving virus on Malus sieboldii-derived apple proliferation resistant rootstocks

Apple stem grooving virus (ASGV, Capillovirus) is widely spread in apple growing regions. As it causes no symptoms on most cultivated apple varieties and rootstocks it is considered latent in Malus x domestica. In Asia, however, ASGV has been found associated with topworking disease of apple rootstocks originating from Malus sieboldii. Recently, M. sieboldii and its hybrids have gained new interest in Europe as they confer resistance to apple proliferation (AP) disease. A new breeding program aiming to develop AP-resistant rootstocks of agronomic value for modern apple culture, reported unexpected tree decline which was to be associated with ASGV. As little information is available on the variability of ASGV isolates in Germany, the complete genome of a German isolate of ASGV associated with tree decline was cloned and sequenced. Sequence comparisons with available ASGV isolates revealed two regions of high variability in the genome. The genetic variability of additional isolates from Germany and other countries were collected and the variable areas characterised. In addition ASGV was successfully maintained in micropropagated apple trees and could be transmitted by in vitro grafting to various genotypes, making it possible to study in vitro the effect of the virus and virus/phytoplama combination on M. sieboldii-derived genotypes. Keywords: Latent apple viruses, Candidatus Phytoplasma mali, micropropagation, in vitro grafting, genetic variabilit

Decomposing diversification effect: evidence from the U.S. property-liability insurance industry

Prior literature suggests that diversified property-liability (P/L) insurers underperform their focused counterparts. While most studies focus on insurers’ overall performance, there is an absence of evidence regarding whether the underperformance is driven by underwriting or investment profitability. The authors develop and test hypotheses of diversification’s separate effect on underwriting and investing in the U.S. property-liability (P/L) insurance industry. It is found that diversified insurers outperform their focused counterparts in terms of investment return, but that they underperform in terms of underwriting profitability. The results are robust to corrections for endogeneity bias and a matched sample analysis

Compounded laxative formulations for substituting phenolphthalein with sennosides A & B in solid dosage forms

Purpose: Following the discovery of the carcinogenicity of phenolphthalein and the subsequent ban of this compound in several countries this study was undertaken to develop compounded formulations of laxative products containing the stimulant laxatives sennosides A and B. Methods: DSC and HPLC analysis was used to determine the compatibility of sennosides with commonly used excipients before compounding capsules, tablets and effervescent tablets containing sennosides A & B. The physical and chemical stability and release properties of these dosage forms were determined for 12 weeks at increased temperature and relative humidity. Results: Sennosides A & B were compatible with a wide variety of powdered excipients. However, these were incompatible with propyl paraben, sodium carbonate, stearic acid, citric acid, PEG, and sugar derivatives such as lactose, glucose and sorbitol when granulated with water. Not withstanding these interactions, it was possible to compound simple capsule, tablet and even an effervescent tablet formulations containing sennosides A & B that complied with pharmacopeial specifications. However, all these formulations were sensitive to moisture because when stored at increased temperature and relative humidity, disintegration times increased and dissolution rates decreased. Conclusion: Based on compatibility and stability studies simple, stable and elegant solid dosage forms containing sennosides A & B were compounded that can be used to replace phenolphthalein in a variety of solid dosage forms. Keywords: Compounding; Sennosides A & B; Phenolphthalein replacement; Drug-Excipient Compatibility > Tropical Journal of Pharmaceutical Research Vol. 3 (1) 2004: pp. 265-27