Partition distribution of selected organochlorine pesticides in water, sediment pore water and surface sediment from uMngeni River, KwaZulu-Natal, South Africa

Abstract: Organochlorine pesticides (OCPs) were analysed in surface water, pore water and surface sediment samples collected from the uMngeni River, which is one of the largest rivers in the province of KwaZulu-Natal, South Africa. Liquid-liquid extraction was used to extract the analytes from water and pore water samples and soxhlet extraction was used to extract sediment samples with subsequent florisil clean-up and gas chromatography-mass spectrometry (GC-MS) analysis. Twelve selected OCPs were analysed and their total concentrations were found to range from 8.04–21.06 ng/mL, 36.06–188.43 ng/mL and 148.17–554.73 ng/g in unfiltered surface water, unfiltered pore water and surface sediment (dry weight (dw)), respectively. The results indicated that the concentrations of these selected pesticides were far higher in sediment (72%) than in pore water (25%) and water (3%). The most polluted sites were Northern Wastewater Treatment influent (NWTI) for water (Σ12OCP = 19.41 ± 1.43 ng/mL) and Northern Wastewater Treatment effluent (NWTE) for pore water (Σ12 OCP = 166.23 ± 7.16 ng/mL) and sediment (Σ12 OCP = 495.21 ± 32.38 ng/g). The most abundant individual OCPs and their average concentrations in general in the river were p,p′-DDE in unfiltered water (1.62 ±0.22 ng/mL) and unfiltered sediment pore water (17.09 ±7.96 ng/mL), and endrin in surface sediment (55.57 ± 19.01 ng/g, dw)

New antitrypanosomal tetranotriterpenoids from Azadirachta Indica

Organic extracts of the leaves of Azadirachta indica A. Juss. yielded ten antitrypanosomal terpenoids. Three of these (1 – 3), are novel and are derivatives of nimbolide and nimbin. They were extracted from chloroformfraction of methanol extract. These compounds were found to exhibit strong antitrypanosomal activities against Trypanosoma brucei rhodesiense with MIC values ranging of 6.9, 15.6 and 7.8 μg/ml respectively and were more active than Cymerlarsan ( a standard drug), which had an MIC value of 187.5 μg/ml when tested against T. b. rhodesiense The structures were elucidated by spectroscopic methods including; NMR, MS, UV and IR.Key words: Meliaceae, limonoids, Trypanosoma brucei rhodesiense, Azadirachta indica, antitrypanosomal activity

Low temperature synthesis of multiwalled carbon nanotubes and incorporation into an organic solar cell

Abstract: Metal nanoparticle (MNP) catalysts used for the synthesis of multiwalled carbon nanotubes (MWCNTs) consisted of single metals (Fe, Ni or Co) and bimetallic mixture (CoFe, NiFe or NiCo). MWCNTs were successfully synthesised at 200 _C in 10 min using liquefied petroleum gas as carbon source with non-equilibrium plasma enhanced chemical vapour deposition (PECVD) method. The nanostructures and the morphology of the MNPs and the MWCNTs film were characterised using relevant microscopic and spectroscopic methods. The synthesised MWCNTs were used as part of the electrode material in organic solar cell (OSC) set-up. Poly (3,4- ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) was used as an electron transporter and poly-3-hexyl thiophene (P3HT) as an electron donor. The performance of OSC devices was tested using standard electrical measurements and solar simulator operating at 100 mW/cm2. The measured power conversion efficiencies was found to be dependent on the metal catalyst used during synthesis. Among all the catalysts employed in this investigation, the best device performance was found from the synthesis of MWCNTs using Fe as a catalyst followed by Co and then Ni, respectively

Identification of Niches for Integration of Brachiaria Grasses in Smallholder Mixed Crop-Livestock Farming Systems in Kenya

Inadequate quantity and quality of feed is the major constraint to livestock productivity in Kenya. Low rainfall, lack of adapted forages and poor management of sown forages are major factors that affect feed resources production. In most of the farming systems, forages are relegated to the less fertile and degraded soils resulting into poor growth. As a result the growth is poor resulting in deficient in minerals content, low crude protein (CP) and energy. The situation in exacerbated by climate variability and frequent drought. On the other hand, feed resources derived from crop residues, particularly cereals are of poor quality and not sufficient to meet animal production (Njarui and Mureithi, 2006). A research programme was initiated in 2012 to explore superior feed resources and increase availability of high quality forages to increase livestock productivity in East Africa. The program focuses on evaluation of drought and marginal soil adapted improved Brachiaria cultivars from South America. The genus Brachiaria is predominantly an African grass with about 100 species. The Brachiaria grasses are the most widely grown forages in South America (Miles et al., 2004). These grasses produce high biomass, enhance soil fertility and reduce greenhouse gas emission (Peters et al., 2012), are highly nutritious and are known to increase milk (Njarui, pers. comm.) thus suitable for different farming systems of Kenya. However, before integration of these grasses into farming systems, it was imperative to identify suitable niches suitable for growing these grasses. The knowledge gained from the study will facilitate development of suitable approaches for promoting these grasses across diverse production systems of Kenya

Design of multi-layer graphene membrane with descending pore size for 100% water desalination by simulation using ReaxFF

DATA AVAILABILITY STATMENT : Data are available upon request from the corresponding author and based on university rules.The performance of a desalination membrane depends on a specific pore size suitable for both water permeability and salt rejection. To increase membrane permeability, the applied pressure should be increased, which creates the need to improve membrane stability. In this research article, a molecular dynamics (MD) simulation was performed using ReaxFF module from Amsterdam Modeling suite (AMS) software to simulate water desalination efficiency using a single and multi-layer graphene membrane. The graphene membrane with different pore sizes and a multi-layer graphene membrane with descending pore size in each layer were designed and studied under different pressures. The stability of the membrane was checked using Material Studio 2019 by studying the dynamics summary. The single-layer graphene membrane was evaluated under pressures ranging from 100 to 500 MPa, with the salt rejection ranging from 95% to 82% with a water permeability of 0.347 109 to 2.94 109 (mm.g.cm2s1.bar1), respectively. Almost 100% salt rejection was achieved for the multi-layer graphene membrane. This study successfully demonstrated the design and optimization of graphene membrane performance without functionalization.The Faculty of Sciences at the University of Johannesburg, South Africa,https://www.mdpi.com/journal/membranesam2023Chemistr

Guiding water into carbon nanopipes with the aid of bipolar electrochemistry

Microfluidics and Nanofluidics, 1(3): pp. 284-288. Retrieved September 19, 2006 from http://nano.materials.drexel.edu/publications.html.The targeted bipolar electrodeposition of polypyrrole was carried out onto the tips of hydrophilic carbon nanopipes. By aligning an external electric field relative to the nanopipes, the deposition of polypyrrole onto selected ends could be achieved without physically contacting the nanopipes. After deposition, carbon nanopipes with both partially open and fully blocked tips were found. Experiments conducted in an environmental scanning electron microscope showed that water enters the nanopipes through the tip with polypyrrole due to the higher hydrophilicity of the polymer compared to the tube walls. As a result, it was possible to guide the entry of water from a specific end of the tube and fill the tube from the selected side. Condensation experiments conducted on nanopipes with polypyrrole on both tips shows the difference in hydrophilicity of the nanopipes compared to the polypyrrole. The ability to selectively control the site of condensation and uptake of fluid by carbon nanotubes or nanopipes is very important for the development of nanotube-based nanofluidic devices

Effect of inclusion of MOF-polymer composite onto a carbon foam material for hydrogen storage application

Despite the extensive studies done on the remarkable characteristics of metal–organic frameworks (MOFs) for gas storage applications, several issues still preclude their widespread commercial lightweight applications. In most cases, MOF materials are produced in powdery form and often require shaping to attain application-specific properties. Fabrication of MOF-polymer composites is considered an attractive approach for shaping MOF powders. In most cases, the final hybrid material retains the intrinsic adsorbing properties of the pristine MOF coupled with other interesting synergistic features which are sometimes superior to their pristine counterparts. In this regard, the use of porous polymers of intrinsic microporosity (such as PIM-1) has proved to be of interest. However, most of these polymers lack some other important properties such as conductivity, which is of paramount importance in a hydrogen storage system. It is on this basis that our study aimed at direct anchoring of a PIM-1/MOF viscous solution onto a carbon foam (CF) substrate. The effects of PIM-1/UiO-66(Zr) inclusion into CF to the resulting thermal properties (thermal conductivity, thermal diffusivity and volumetric heat capacity) as well as hydrogen uptake capacity was investigated. Contrary to our expectations, the incorporation of PIM-1/UiO-66(Zr) into CF only offered better handling but did not lead to the enhancement of thermal conductivity.The Department of Science and Innovation (DSI) of South Africa towards HySA Infrastructure, National Research Foundation (NRF) for SA/France collaboration funding and the Royal Society—DFID Africa Capacity Building Initiative Programme Grant.http://link.springer.com/journal/109042021-08-09hj2020Chemistr

Determinants of antibody persistence across doses and continents after single-dose rVSV-ZEBOV vaccination for Ebola virus disease: an observational cohort study.

BACKGROUND: The recombinant vesicular stomatitis virus (rVSV) vaccine expressing the Zaire Ebola virus (ZEBOV) glycoprotein is efficacious in the weeks following single-dose injection, but duration of immunity is unknown. We aimed to assess antibody persistence at 1 and 2 years in volunteers who received single-dose rVSV-ZEBOV in three previous trials. METHODS: In this observational cohort study, we prospectively followed-up participants from the African and European phase 1 rVSV-ZEBOV trials, who were vaccinated once in 2014-15 with 300 000 (low dose) or 10-50 million (high dose) plaque-forming units (pfu) of rVSV-ZEBOV vaccine to assess ZEBOV glycoprotein (IgG) antibody persistence. The primary outcome was ZEBOV glycoprotein-specific IgG geometric mean concentrations (GMCs) measured yearly by ELISA compared with 1 month (ie, 28 days) after immunisation. We report GMCs up to 2 years (Geneva, Switzerland, including neutralising antibodies up to 6 months) and 1 year (Lambaréné, Gabon; Kilifi, Kenya) after vaccination and factors associated with higher antibody persistence beyond 6 months, according to multivariable analyses. Trials and the observational study were registered at ClinicalTrials.gov (Geneva: NCT02287480 and NCT02933931; Kilifi: NCT02296983) and the Pan-African Clinical Trials Registry (Lambaréné PACTR201411000919191). FINDINGS: Of 217 vaccinees from the original studies (102 from the Geneva study, 75 from the Lambaréné study, and 40 from the Kilifi study), 197 returned and provided samples at 1 year (95 from the Geneva study, 63 from the Lambaréné, and 39 from the Kilifi study) and 90 at 2 years (all from the Geneva study). In the Geneva group, 44 (100%) of 44 participants who had been given a high dose (ie, 10-50 million pfu) of vaccine and who were seropositive at day 28 remained seropositive at 2 years, whereas 33 (89%) of 37 who had been given the low dose (ie, 300 000 pfu) remained seropositive for 2 years (p=0·042). In participants who had received a high dose, ZEBOV glycoprotein IgG GMCs decreased significantly between their peak (at 1-3 months) and month 6 after vaccination in Geneva (p0·05). Neutralising antibodies seem to be less durable, with seropositivity dropping from 64-71% at 28 days to 27-31% at 6 months in participants from the Geneva study. INTERPRETATION: Antibody responses to single-dose rVSV-ZEBOV vaccination are sustained across dose ranges and settings, a key criterion in countries where booster vaccinations would be impractical. FUNDING: The Wellcome Trust and Innovative Medicines Initiative 2 Joint Undertaking