Search

Background: Staphylococcus aureus is a serious pathogen, able to cause life-threatening infections such as bacteraemia. The association between S. aureus microbial characteristics and clinical outcomes is under-investigated in African settings. This study aimed to determine the molecular epidemiology and virulence characteristics of S. aureus isolates from bacteraemic patients at Tygerberg Hospital, South Africa, and to investigate the associations between pathogen characteristics and clinical outcomes. Methods: This study included 199 S. aureus isolates collected from blood cultures between February 2015 and March 2017. Methicillin resistance was determined using disc diffusion and all resistant isolates were further characterized by staphylococcal cassette chromosome mec (SCCmec) typing. Genotyping was done using spa and agr typing, and agr functionality was assessed using the phenotypic δ-haemolysin assay. Logistic regression models were performed to describe the associations between strain characteristics and the clinical outcomes methicillin resistance, in-hospital mortality, and length of stay (LOS). Results: Of the 199 S. aureus isolates collected, 27% were MRSA, and the overall crude in-hospital mortality rate was 29%. Seventy-three different spa types were identified, including seven new types. Agr I was the most common type, in 99 (49.7%) isolates, followed by agr II, III, and IV in 57 (28.6%), 37 (18.6%), and six (3%) isolates, respectively. Agr dysfunctionality was observed in 25 (13%) isolates, mostly belonging to spa-clonal complex (CC) 012. Methicillin resistance was significantly associated with hospital-acquired infection (odds ratio (OR) 4.77, 95% confidence interval (CI) 2.09–10.87). A significant increase in mortality was observed with increasing age (OR 7.48, 95% CI 2.82–19.8) and having a hospital-acquired infection (OR 2.26, 95% CI 1.12–4.55). S. aureus strains with a functional agr system showed an association with longer duration of stay (OR 1.66, 95% CI 0.93–2.99). Conclusions: We report the lowest MRSA prevalence at Tygerberg Hospital for the past 10 years, and agr dysfunctionality was shown to be driven by a certain genotype, spa-CC012. Despite the limited available clinical data, the study provided insights into associations between S. aureus epidemiology and agr-related virulence characteristics, and clinical outcomes. Keywords: Staphylococcus aureus, Accessory gene regulator (agr), MRSA, Molecular epidemiology, Mortality, Bacteraemia

Often mechanical parts have specific requirements in regard to the underlying alloy. Especially for axial symmetric parts like rings an often requested characteristic is a different requirement on the inner surface than on the outer. Therefore, different production processes exist. One strategy is to roll a basic ring e.g., via radial-axial ring rolling (RARR), and create a functional layer afterwards via thermal spraying. The temperature of the ring and the spraying particles influence the bonding behavior and compaction of the thermal sprayed layer benefits its mechanical properties. The hypothesis presented in this paper is a better performing thermal sprayed layer regarding the adhesion of the layer, reduced porosity and improved residual compressive stress through the combination of the thermal spraying process and the radial-axial ring rolling. After an introduction to the industrial processes of radial-axial ring rolling and thermal spraying, the experimental setup and the results are presented. In the first step, the approach of combining these processes includes an experimental design, in which the rolling of the basic ring, consisting of a 1.0570-steel, gets interrupted right before the target diameter is reached. The ring is then transported to the thermal spraying process where the ring gets covered with layers of 316L-Si, sprayed with a pressure of 8 bar, arc voltage of 34.0 V and a wire feedrate of 2.1 m/min. The coated rings were rolled to two different target diameters with a planned degree of deformation of 0.025 and 0.098 only in the radial direction. This deformation leads to an elongation of the outer circumference of 2.56 % and 10.26 %. Due to the rolling process, the applied coatings revealed a compacting effect and, thus, a significant reduction in the total porosity. The main goal of this study is to investigate the material pairings and parameters regarding thermal spraying and RARR to produce an intact coating with adequate adhesion to the substrate. The long term vision is to adapt thermally sprayed coating into the radial-axial ring rolling process.

Milk processing industries consume significant volumes of sustainable water during processing and operating steps to meet hygienic requirements. Therefore, such industries are recognized as a potential source for producing large volume of contaminated water which generally contains biodegradable matters, and are subsequently suitable to be biologically treated. Based on this, many researchers have been moving towards milk processing wastewater (MPW) treatment via biological approaches. In present study, the performance of a single stage flexible fibre biofilm reactor (SS-FFBR) in mitigation of organic loading of the MPW was assessed. The performance of SS-FFBR in terms of the biological treatment was statistically modelled and analysed in terms of HRT and CODin by employing response surface methodology (RSM). From the results, it is clear increase in HRT and decrease in the CODin led to incrementing the COD removal percentage. In addition, a significant mutual interaction occurs between the variables and other responses. The optimum removal was reported at an HRT of 8 h and CODin of 3922 mg/L corresponded to high OLR of 11.67 kg COD/m3 d. The experimental results were in good agreement with model prediction.

In the last few decades, membrane technology has been extensively utilised in many water treatment applications. Nevertheless, wider implementation of this technology is hindered due to membrane fouling phenomenon. To address this major drawback, membrane modification has been widely studied to increase the membrane resistance to fouling. This paper studies the effect of using chitosan solution to modify ultrafiltration PAN and PVDF membranes and evaluate their filtration of humic acid (HA) solution and their fouling resistance capabilities. Two modification methods were evaluated, namely immersion and flow through methods. The hydrophilicity of both membranes was significantly improved due attachment of hydrophilic chitosan particles on the surface of the membrane. The flow through modification method enables deposition of chitosan particles inside the membrane pores enhancing the hydrophilicity of the membrane compared with the immersion method. The deposition of chitosan on both membranes reduced their water permeability. However, both modified membranes exhibited enhanced fouling resistance property. Furthermore, their rejection of HA was improved, particularly with PVDF membranes.

The photocatalytic nanocomposite NF membranes blended with K-B-N triple TiO2 were fabricated employing conventional wet phase inversion method. The dynamic performance of the photocatalytic membranes was evaluated by filtering biologically treated palm oil mill effluent (POME) at dark and light conditions. The performance of the chosen membrane was checked using central composite design (CCD) of response surface methodology (RSM) under continuous visible light irradiation and various variables in a dynamic mode. According to experimental results, the 0.5 wt. % membrane indicated less flux reduction without scarifying COD rejection capacity as a function of time while filtering POME under continuous visible light irradiation. The largest values of FRR and COD removal efficiency were reported to be 97 % and 100 %, respectively, at the highest feed flow rate of 150 L/min, the lowest operating pressure of 5 bar, and the lowest COD concentration of 1000 mg/L. While, the highest value of flux (33.9 kg/m2h) was obtained at operating pressure of 9 bar, feed flow rate of 50 L/h and COD concentration of 1000 mg/L. By judging from results, the photocatalytic NF membrane by benefiting from both photocatalytic and self-cleaning properties has enough potential to be applied in practical applications.

In transportation, Electricity plays a key role in modern dependency techniques, which researchers are concentrating their studies on. Electric Vehicles (EVs) and industrial machinery will continue to significantly increase in the coming years with the advent of Smart Grid (SG) with EVs integration system. The changeable increase of EVs makes them a valuable device in the modern era. SG is principally defined as the use of information technology with the electric by transferring electricity in both directions. This means to import and export to the grid via EVs, i.e Vehicle to Grid (V2G) operation. Recent literature demonstrated the significance of EVs to overcome power and environmental issues using energy management strategy (EMS). This article reviews the achievement of EMSs in the EV system reducing fuel consumption and carbon dioxide emission. To close the gap between the existing bodies of knowledge, this article focuses on the up-to-date and state-of-the-art standards of EV technology, energy resources, charging topologies and infrastructure, EMS classification, power conditional units, and electric load management. Recommendations are given as future research work to address the challenges affecting the V2G technology. The novelty of this article is the update on the state-of-the-art in the area of V2G and EMS.

Stable and reliable electricity is a prerequisite to the development of any nation and improving the living standard of the society. By exploiting Renewable Energy Sources (RESs) such as solar energy (PV) and wind energy (WT) as widely acknowledged RESs to be more environmentally friendly and address power difficulties. They are acknowledged to be an interesting option to charge Electric Vehicles (EVs) via Vehicle-to-Grid (V2G) technology. On the contrary, to the best knowledge of the authors, there are few numbers published articles on RESs (PV and WT) integrated with Electric Vehicle Charging Station (EVCS) to charge EVs. This research is aimed at implementing a metaheuristic optimization algorithm named Antlion Optimizer (ALO) algorithm for sizing the system components to meet the load demand and minimize the two objective functions - Losses Power Supply Probability (LPSP) and Cost of Electricity (COE) while maximizing the Renewable Energy Fraction (REF). In addition, the Rule-Based Energy Management Strategy (RB-EMS) is proposed to control the flow of power in the system. The integration of RESs to the utility grid with V2G technology and V2G services is discussed. Furthermore, the State-of-the-art for improving the stability and reliability of the grid-connected system is presented. As a result, the attained result from the proposed method shows better performance results as 0.0936 $/kWh, 0.1044%, and 0.9940% for COE, LPSP, and REF, respectively. The research is conducted in different microgrid configurations using a MATLAB environment.

In this work, a multistage flexible fibre biofilm reactor (MS-FFBR) composed of four equal-size compartments was used successfully to treat milk processing wastewater (MPW). Response surface methodology (RSM) was also used to evaluate, model, and optimize the performance of the MS-FFBR. The effect of variation of two process variables (CODin and HRT) on the system performance was evaluated by measuring different responses (TCOD, SCOD, TBOD5, SBOD5, TSS removal efficiency, turbidity, pH, SRT and U). From findings, the maximum removal efficiency in terms of TCOD, SCOD, TBOD and SBOD was achieved at 12 h HRT and 1590 mg L−1 CODin, whereas the lowest removal efficiencies were observed at 8 h HRT and 5869 CODin. The minimum TSS removal efficiency was obtained at 8 h HRT and 3750 mg L−1. More importantly, the MS-FFBR indicated good buffering capacity throughout the experiments. The optimum region was found at HRT less than 8 h and 1500 mg L−1