The effect of sheared diamagnetic flow on turbulent structures generated by the Charney–Hasegawa–Mima equation

The generation of electrostatic drift wave turbulence is modelled by the Charney–Hasegawa–Mima equation. The equilibrium density gradient n0=n0(x) is chosen so that dn0 /dx is nonzero and spatially variable (i.e., v*e is sheared). It is shown that this sheared diamagnetic flow leads to localized turbulence which is concentrated at max(grad n0), with a large dv*e/dx inhibiting the spread of the turbulence in the x direction. Coherent structures form which propagate with the local v*e in the y direction. Movement in the x direction is accompanied by a change in their amplitudes. When the numerical code is initialized with a single wave, the plasma behaviour is dominated by the initial mode and its harmonics

'n Ondersoek na operasionele praktykvoerings en- bestuursriglyne vir stads- en streekbeplanners: Moontlike riglyne vir die privaat praktyk

Die Vryemark-ekonomie moedig die vestiging van nuwe ondememings aan asook die groei van bestaande ondernemings. Hierdie studie het van die standpunt uitgegaan dat talle persone graag ’n eie onderneming wil begin, maar nie werklik die nodige bestuursvaardigheid het nie. Die privaat praktyk kan die vergestalting van ’n wye ondememingstelsel vir die beplanner wees; dit is die vryheid van die individu om vir sy eie voordeel ’n onderneming van sy eie keuse te begin en te bedryf. Die stelsel van mededinging en handel, asook die aanmoediging om nuwe ondernemings te vestig, is tiperend van ’n verskeidenheid ondernemings waarin ook die beplanner i.t.v. geesdrif, inisiatief, vindingrykheid, kreatiwiteit en sy besondere kundigheid, uiting in ’n eie praktyk kan vind

Planning for the upgrading of informal settlements

Planning for the upgrading of informal settlements is still a relatively unknown field for planners in South Africa and it is certain to receive more attention in future. The role of the upgrading of informal settlements in providing low income housing will be discussed, as well as certain factors that play an important role in planning projects of this kind. A "strategy", involving certain alternative solutions available to the planner in the field, will then be put forward. Findings from a study done in Joe Slovo Square, Bloemfontein, will be used to illustrate the article

Russian wheat aphid causes greater reduction in phloem transport capacity of barley leaves than bird cherry-oat aphid

The effects of feeding by the Russian wheat aphid (RWA), Diuraphis noxia Mordvilko and the Bird cherry-oat aphid (BCA), Rhopalosiphum padi L on the transport capacity of barley Hordeum vulgare L leaves were investigated and compared with a view to relating these effects to the visible symptoms shown by the respective infested plants. RWAcauses extensive chlorosis and necrosis on an infested plant whereas BCA causes no observable symptoms. Our results using the xenobiotic, phloem mobile fluorophore, 5, 6 carboxyfluorescein diacetate (5, 6-CFDA) revealed striking differences in damage to the transport of assimilates through the phloem by these two aphids. The result clearly suggests that short-term feeding by RWA causes a reduction in transport of assimilates and a more severe reduction or perhaps even permanent cessation of transport during long-term feeding. In contrast, feeding by BCA does not lead to a marked decrease in transport during short-term feeding period, however, a reduction in the transport was recorded during long-term feeding activities. These results perhaps suggest that damage to transport capacities of the barley leaves appears to be partly responsible for the observed symptoms in RWA-infested plants and the lack of them during BCAinfestations, symptoms such as reduction or cessation in transport of assimilates to growing tissues may lead to such observable symptoms

A study of wool from Merino stud rams

The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Xylem as well as phloem sustains severe damage due to feeding by the Russian wheat aphid

Investigation of comparative effects of feeding damage by the Russian wheat aphid (RWA, biotype SA1, Diuraphis noxia Mordvilko) on leaf blades of susceptible and resistant wheat cultivars (Triticum aestivum L. var Betta and Betta-Dn1 respectively) were carried out to establish the level of ultrastructural damage caused by this aphid and the possible limitation of damage induced which could be ascribed to the resistance gene Dn1 over the susceptible cultivar. Ultrastructurally, Betta-Dn1 sustained less damage to the vascular tissue as well as to the mesophyll during the experimental period. Both inter- and intracellular probes resulted in considerable saliva deposition as the aphids probed for suitable feeding sites. Salivary tracks were observed between and within mesophyll, bundle sheath cells as well as the vascular tissue, including the xylem. Disruption of organelles and cytoplasm resulted from cell probing and sheath deposition. Cell and organelle damage was more evident in the non-resistant Betta cultivar. The aphids probed for and fed from thin-walled sieve tubes preferentially. Few thick-walled sieve tubes showed evidence of either aphid probing or feeding-related damage. Saliva was deposited when the aphids probed inter- and intracellularly for feeding sites. The aphids appeared preferentially to probe for and feed from thin-walled sieve tubes, as few thick-walled sieve tubes showed evidence of damage. Vessels, apparently probed for water, contained watery saliva that encased the secondary walls and sealed pit membranes between probed vessels and xylem parenchyma. The xylem probed by the RWA was rendered non-functional, probably contributing to symptoms of leaf roll, chlorosis and necrosis, which were observed within two weeks of infestation in the susceptible Betta cultivar. This damage was limited in the resistant Betta-Dn1 cultivar during the same time frame

Potential for genetic improvement of sugarcane as a source of biomass for biofuels

Sugarcane (Saccharum spp. hybrids) has great potential as a major feedstock for biofuel production worldwide. It is considered among the best options for producing biofuels today due to an exceptional biomass production capacity, high carbohydrate (sugar + fiber) content, and a favorable energy input/output ratio. To maximize the conversion of sugarcane biomass into biofuels, it is imperative to generate improved sugarcane varieties with better biomass degradability. However, unlike many diploid plants, where genetic tools are well developed, biotechnological improvement is hindered in sugarcane by our current limited understanding of the large and complex genome. Therefore, understanding the genetics of the key biofuel traits in sugarcane and optimization of sugarcane biomass composition will advance efficient conversion of sugarcane biomass into fermentable sugars for biofuel production. The large existing phenotypic variation in Saccharum germplasm and the availability of the current genomics technologies will allow biofuel traits to be characterized, the genetic basis of critical differences in biomass composition to be determined, and targets for improvement of sugarcane for biofuels to be established. Emerging options for genetic improvement of sugarcane for the use as a bioenergy crop are reviewed. This will better define the targets for potential genetic manipulation of sugarcane biomass composition for biofuels

Anaerobic ammonium oxidation in the old trickling filters at Daspoort Wastewater Treatment Works

The century-old trickling filters at the Daspoort Wastewater Treatment Works in Pretoria (Gauteng, South Africa) are known for their remarkable removal of nitrogen from municipal wastewater. Our study was conducted to identify the microbiological processes responsible for this phenomenon and to establish whether anammox bacteria may be involved. An aerobic and anaerobic bench top reactor, both inoculated with biofilm-covered stones from one of the filters, were spiked with ammonia-nitrogen  (NH4+-N) and nitrite-nitrogen (NO2.-N). These reactors were subsequently monitored by conducting stoichiometric analyses of chemical oxygen demand (COD), NH4+-N, NO2.-N, and nitrate-nitrogen (NO3.-N). In the aerobic reactor, the COD concentration decreased over the 56 h batch reaction period and nitrification was revealed by a decrease in NH4+-N and NO2.-N concentrations. However, the NO3.-N concentration showed no  notable decrease. In contrast, in the anaerobic reactor the concentrations of COD, NH4+-N, NO2¡¥-N, NO3¡¥-N, as well as total nitrogen decreased during the batch reaction period. The decrease of both the NH4+-N and NO2.-N concentrations, the latter to zero under anaerobic conditions,   suggested that, in addition to heterotrophic denitrification, anaerobic ammonium oxidation (anammox) may also occur in the trickling filter biofilm. This was highlighted by the observation that ammonium removal in the anaerobic reactor stopped as soon as the nitrite concentration  became zero. The ratio of nitrite:ammonium removal was 1.33 on  average, which conforms to anammox behaviour. Gene sequence analysis was used to test for the possible presence of anammox bacteria in the  trickling filter biofilm. Genomic DNA was extracted from trickling filter  humus sludge and the polymerase chain reaction (PCR) was used to  amplify taxonomically informative 16S rRNA gene sequences, using  primers specific for selected anammox species. Subsequent sequence analysis, including using the online Basic Local Alignment Search Tool (BLAST), and constructing a phylogenic tree using a heuristic search  strategy for Maximum Parsimony analysis, confirmed the presence of an anammox bacterium closely related to Candidatus ¡®Brocadia  anammoxidans¡¯ and Candidatus ¡®Brocadia fulgida¡¯ on the biofilm-covered stones of the Daspoort trickling filters.Keywords: Daspoort, trickling filter, anammox, nitrification, denitrification, stoichiometric analyses, polymerase chain reactio