Batch and automated SVI measurements based on short-term temperature variations

Effects of short-term temperature variations on the sludge volume index (SVI) are evaluated with batch and automated mixed liquor suspended solids (MLSS) settling tests. The test-cylinder environment and meteorological conditions have a direct influence on the MLSS sample temperature (Ts). A Ts change of 4.3°C over the 30 min settling test duration results in an inverse SVI change of 63.0 mℓ/g, at an average SVI decrease of 14.8 mℓ/g per 1°C Ts increase. Ts compensation or control during routine SVI tests is not common practice, partially due to a lack of temperature-controlled equipment and an absence of Ts-based MLSS settling models. A practical solution is found to reduce Ts variations experienced before and during batch MLSS settling tests. An automated MLSS settling meter is used to demonstrate a semi-continuous on-line method to determine SVI at the operational reactor temperature (Tr) of a full-scale plant. Basic and best-fit SVI models are obtained from the SVI data generated over diurnal periods, based on MLSS concentration and Tr fluctuations. These SVI models confirm the inverse dependence of SVI on temperature for the site-specific conditions. A diurnal Tr fluctuation of 1.8°C results in an SVI change of 26.6 mℓ/g, at an average -14.8 mℓ/g SVI change per 1°C Tr variation.Keywords: activated sludge, mixed liquor suspended solids (MLSS), model, sludge volume index (SVI), settleability, temperature, wastewate

Genotoxic effect induced by hydrogen peroxide in human hepatoma cells using comet assay

Background: Hydrogen peroxide is a common reactive oxygen intermediate generated by variousforms of oxidative stress. Aims: The aim of this study was to investigate the DNA damage capacity ofH2O2 in HepG2 cells. Methods: Cells were treated with H2O2 at concentrations of 25 μM or 50 μM for5 min, 30 min, 40 min, 1 h or 24 h in parallel. The extent of DNA damage was assessed by the cometassay. Results: Compared to the control, DNA damage by 25 μM and 50 μM H2O2 increasedsignificantly with increasing incubation time up to 1 h, but it was not increased at 24 h. Conclusions:Our Findings confirm that H2O2 is a typical DNA damage inducing agent and thus is a good modelsystem to study the effects of oxidative stress. DNA damage in HepG2 cells increased significantlywith H2O2 concentration and time of incubation but later decreased likely due to DNA repairmechanisms and antioxidant enzyme

Batch and automated SVI measurements based on short-term temperature variations

Please refer to abstract in articl

Scanning electron microscopy investigation of fibrin networks after thermal injury

Injury due to burning is known to impact on coagulation and haemostasis by disturbing the coagulation cascade and is also associated with impaired fibrinolysis. Also, venous thrombosis, pulmonary embolism and hypercoagulability are common during thermal injury. Using a Wistar albino rat model, we investigated in this study whether burn injury affects the ultrastructure of the fibrin networks. A typical fibrin network will contain mostly major, thick fibres with minor, thin fibres distributed amongst them. We found that the clot architecture changes after burn injury, showing more prominent minor, thin fibres in a netted appearance. Also, the clot showed areas of matted fibrin. We suggest that the thrombotic events associated with burn injury are due to the thickened and netlike areas formed when thrombin activates the coagulation cascade. This is due to impaired fibrinolysis activities, causing the resulting fibrin clots not to be successfully disseminated. Small fragments of these netted, clumped areas may therefore break loose and lead to thrombotic events after burn injuries. The current study therefore provided morphological evidence for thrombotic events associated with burn injury

Geskiedenis van die Universiteit van Pretoria

Die tydperk 1983-1992 was in vele opsigte hetekenisvolle jare in die geskiedenis van die Universiteit van Pretoria. Die Universiteit bet in die tydperk voor groot uitdagings te staan gekom wat alleen in geleenthede omskep kon word deur ingrypende aanpassings in die bestuurstelsel te maak en berstrukturering op 'n groot aantal terreine teweeg te bring. Dit is dus gepas dat die geheurtenisse en tendense van hierdie tydperk in die publikasie Ad Destinatum III te hoek gestel word. Gelyklopend met bierdie helangrike fase in die Universiteit se geskiedenis was die opwindende polities-staatkundige veranderinge in Suid-Afrika. Verwikkelinge op die kampus bet uit die aard van die saak nie los daarvan gestaan nie. Selfs van nog meer regstreekse belang vir die Universiteit as die staatkundige veranderinge, was die belangrike heleidsformulering en -toepassing wat in die jare tagtig ten opsigte van die Suid-Afrikaanse universiteitswese as geheel plaasgevind het. Die Universiteit van Pretoria bet deeglik hiervan kennis geneem en bet ook by wyse van individuele lede van die Rektoraat prominente insette gelewer. Een van die knelpunte wat in die tyd hlootgele is, was die toenemende finansiele druk wat Suid-Afrikaanse universiteite ervaar het. Die Universiteit kon egter, wat dit betref, met vindingryke finansiele heplanning en hestuur die nadelige uitwerking daarvan in 'n groot mate beperk. Aansluitend hierby het die Universiteit in die tyd ook 'n nuwe bestuursmodel geimplementeer met onder meer 'n gedesentraliseerde gesaghestuurstelsel en behoorlik geformuleerde doelstellings, missies en strategieë. Dit het die infrastruktuur en ruimte geskep vir dinamiese beplanning en gladde funksionering. Die Universiteit het in die tydperk 1983- 1992 skouspelagtige groei ten opsigte van studentegetalle beleef - van 16 854 tot 23 375. Dit het egter ook nuwe uitdagings meegebring. Voldoende fisiese fasiliteite moes byvoorbeeld geskep word. Daaraan is voldoen met verskeie omvangryke en kleiner bouprojekte en ander verbeteringe. Die uitbreiding van die Universiteit se onderrigaktiwiteite na Withank in hierdie tyd verdien in hierdie verband ook vermelding. Met die totstandkoming van die satellietkampus te Witbank het kontakuniversiteitsonderrig toeganklik geword vir baie Oos-Transvaalse studente wat andersins nie die geleentheid daartoe sou gehad het nie. 'n Eiesoortige na-uurse onderrigmodel is hier ontwikkel wat ook 'n groot invloed op die onderrigmodel op die Hootkampus uitgeoefen het. Hierdie tydperk in die Universiteit se geskiedenis sal beslis verder onthou word vanwee besondere akademiese prestasies deur dosente en studente. Die Universiteitse navorsingsaktiwiteite het vinnig uitgebrei en die navorsingsuitsette het vinnig toegeneem. Dit het dikwels internasionale erkenning geniet. Uitstaande hoogtepunte is ook op die terrein van sport en ten opsigte van breer kultuuraangeleenthede behaal. Veral met die persoonlike belangstelling en aanmoediging van die vorige Rektor, prof. D.M. Joubert, het kunsuitstallings en -versamelings aan die Universiteit 'n bloeitydperk beleef. Die Universiteit kyk met groot waardering terug na 'n dekade waarin moeilike uitdagings met groot sukses aangepak is en uitnemende bydraes en prestasies op verskillende terreine gelewer is. 'n Stewige grondslag is gele vir selfs nog hoer hoogtepunte in die nuwe dekade.Digitised by the Department of Library Services in support of open access to information, University of Pretoria, 202

South Africa’s winter rainfall region drought : a region in transition?

The Western Cape region of South Africa is a key producing area for South African agriculture, with a strong dependence on austral winter rainfall. The past three years have, however, seen extensive drought impacting this region, with significant impacts on agriculture. In this article, we unpack how the drought unfolded, as well as possibilities in predicting winter rainfall. We consider how drought impacted agriculture, looking in depth at two commodities key to the winter rainfall region agricultural sector – namely, wheat and apples; concluding with a brief discussion of implications for the future.https://www.elsevier.com/locate/crmam2020Geography, Geoinformatics and Meteorolog