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Removal of rhodamine 6G from aqueous solution in a continuous mode using nano-micro composite membranes
No full textThis research presents the production of nanofibers, track-etched membrane, and nanofiber/track-etched composite membranes and their dye rejection studies. Polyamide 6 nanofibers (PA6-nfs) and polyacrylonitrile nanofibers (PAN-nfs) were fabricated using an electrospinning technique. Their respective composites with the metalized track-etched polyethylene terephthalate film (PET-TM), PET-TMPA6, and PET-TMPAN were also fabricated via electrospinning. The membranes were characterized using HRSEM, TEM, BET, and TGA techniques. The rejection experiments were studied with respect to the pH and the concentration of rhodamine 6G (RD), as well as the flow rate of the system. The pH is the most significant parameter in the filtration system at higher dye concentrations. At pH 10, the rejection percentages of 10 mg/L RD were 91.27% for PET-TMPAN and 70.66% for PET-TMPA6 at a flow rate of 1 mL/min. Also, PAN-nfs, PA6-nfs, and PET-TM gave 65.97%, 36.80%, and 24.53%, respectively. The composite membranes have higher rejection capabilities in comparison to their respective nanofibers. The performance of PET-TMPAN at a lower flow rate of 0.5 mL/min showed that the RD rejection by PET-TMPAN increased by ≈5 percent (91.27 to 96.01). At a lower concentration of 2 mg/L (to simulate higher dilution in river water) and pH (5.6), PET-TMPAN had a 99.59% RD rejection. All the membranes were regenerated and reused. The composite membrane PET-TMPAN has the capability to remove RD at both higher (96.01%) and lower concentrations (99.59%) of RD at lower flow rate, thereby making the system applicable and easy to use in river water purification
Investigation of organic hydrotrioxide (roooh) formation from ro2 + oh reactions and their atmospheric impact using a chemical transport model, stochem-cri
No full textIncorporating the reactions of fifty peroxy radicals (RO2) with the hydroxyl radical (OH) into the global chemistry transport model, troposphere, affected the composition of the troposphere by changing the global burdens of NOx (−2.7 Gg, −0.5%), O3 (−2.3 Tg, −0.7%), CO (−3.2 Tg, −0.8%), HOx (+2.1 Gg, +7.7%), H2O2 (+0.5 Tg, +18.3%), RO2 (−8.0 Gg, −18.2%), RONO2 (−19.4 Gg, −4.7%), PAN (−0.1 Tg, −3.4%) HNO3 (−7.4 Gg, −1.3%) and ROOH (−96.9 Gg, −3.8%). The RO2 + OH addition reactions have a significant impact on HO2 mixing ratios in tropical regions with up to a 25% increase, resulting in increasing H2O2 mixing ratios by up to 50% over oceans. Globally, a significant amount of organic hydrotrioxides (ROOOH) (86.1 Tg per year) are produced from these reactions with CH3OOOH (67.5 Tg per year, 78%), isoprene-derived ROOOH (5.5 Tg per year, 6%) and monoterpene-derived ROOOH (4.2 Tg per year, 5%) being the most significant contributors. The tropospheric global burden of CH3OOOH is found to be 0.48 Gg. The highest mixing ratios of ROOOH, of up to 0.35 ppt, are found primarily in the oceans near the tropical land areas. The RO2 + OH reactions have a small, but noticeable, contribution to OH reactivity (∼5%) over tropical oceans. Additionally, these reactions have a significant impact on RO2 reactivity over tropical oceans where losses of the CH3O2 radical, isoprene derived peroxy radical (ISOPO2) and monoterpene derived peroxy radical (MONOTERPO2) by OH can contribute up to 25%, 15% and 50% to the total RO2 loss, respectively. The changes in RO2 reactivity influence the global abundances of organic alcohols (ROH) which are important species due to their crucial impact on air quality. The ROOOH generate secondary organic aerosol (SOA) of up to 0.05 μg m−3 which affects the Earth's radiation budget because of enhancing modelled organic aerosol by up to 5% and 2000% on land surfaces and the remote tropical oceans, respectively
Commensal transient searches with meerkat in gamma-ray burst and supernova fields
No full textThe sensitivity and field of view of the MeerKAT radio telescope provide excellent opportunities for commensal transient searches. We carry out a commensal transient search in supernova and short gamma-ray burst fields using methodologies established by S. I. Chastain et al. We search for transients in MeerKAT L-band images with integration times of 30 minutes, finding 13 variable sources. We compare these sources to the VLASS and RACS survey data, and examine possible explanations for the variability. Additionally, for one of these sources we examine archival Chandra ACIS data. We find that 12 of these sources are consistent with variability due to interstellar scintillation. The remaining source could possibly have some intrinsic variability. We also split the MeerKAT L band into upper and lower halves, and search for transients in images with an integration time of 8 s. We find a source with a duration of 8-16 s that is highly polarized at the lowest frequencies. This source is spatially coincident with a star detected by the Transiting Exoplanet Survey Satellite. We conclude that this source may be consistent with a stellar flare. Finally, we calculate accurate upper and lower limits on the transient rate using transient simulations
High-quality genome assembly and annotation of Thalassiosira rotula (synonym of Thalassiosira gravida)
No full textDiatoms are unicellular eukaryotic microorganisms thriving in most aquatic environments thanks to the expression of biosynthetic pathways for secondary metabolites involved in defence and adaptation to environmental changes. The sequencing of the transcriptome of the cosmopolitan diatom Thalassiosira rotula Meunier 1910 (synonym of Thalassiosira gravida Cleve 1896) and of the metagenome of its associated microbiome revealed the presence of biosynthetic pathways synthesising molecules and compounds useful for the algae survival and with potential biotechnological applications. Here we present the genome of a Neapolitan T. rotula strain, which is 672 Mbp in size due to a high proportion of repetitive elements (63.59%) and segmental duplications (14%), while the number of predicted genes resulted to be comparable to that of smaller diatom genomes. DNA methylation was predominantly located in transposable elements
The provision of contraception and STI prevention methods within the public sector to young people in the Western Cape
No full textBackground: There is a global recognition that prioritizing the sexual and reproductive health of adolescents is essential for their well-being and future. Access to contraception information and services is essential in preventing unplanned pregnancies and sexually transmitted infections. Accordingly, with the advent of a democratic South Africa, new policies were introduced to promote the sexual and reproductive health of young people. However, there is limited research on how these policies are implemented to ensure the provision of contraception to young people. The aim of this thesis was to assess how contraception and sexually transmitted infection (STI) prevention methods are provided to youth in the Western Cape public health sector. Methods: We used an exploratory, descriptive approach within the qualitative domain of research in this thesis. This study was conducted in an urban and rural district of the Western Cape province in South Africa. Using purposive sampling, we recruited primary healthcare and school health practitioners with experience in implementing adolescent sexual and reproductive health interventions in South Africa
Exploring the experiences and perceptions of adolescents and young adults of adherence to antiretroviral therapy treatment at a referral opportunistic infection clinic in Harare, Zimbabwe
No full textBackground: The HIV pandemic continues to have a significant impact on global public health with approximately 39 million people infected with HIV. According to estimates, there are 1.65 million adolescents living with HIV worldwide, of which 85% live in sub-Saharan Africa. While HIV/AIDS-related mortality is decreasing for most age groups, it is not declining for Adolescents and young adults (AYAs) (aged 15–24 years). Poor adherence among AYAs contributes to the poor outcomes of HIV interventions. The aim of the current study was to explore the experiences and perceptions of antiretroviral therapy (ART) adherence among AYAs at a referral Opportunistic Infection Clinic in Harare, Zimbabwe. Methodology: The study employed qualitative methods, where data was collected through semi-structured in-depth interviews with 12 AYAs and 5 key informants at a referral Opportunistic Infection Clinic in Harare, Zimbabwe. All the interviews were audio-recorded, and Shona recordings were translated to English before transcription. An inductive thematic analysis was done
“VigilanS-Prison”: a brief contact intervention to prevent suicidal behavior in prisons and corrections
No full textIn France, suicide accounts for around half of all deaths in prisons. Every year, around 120 people die by suicide in French prisons, i.e. one suicide every three days. Preventing suicide in prisons is therefore a major public health issue. In this interview With Jean-Pierre Bouchard, Élodie Mao, Thomas Fovet, Christel Debien, Guillaume Vaiva, Christophe Debien and Vincent Jardon provide feedback on the implementation of the VigilanS-Prison system in Hauts-de-France. The main principles of this brief contact intervention are presented, an initial activity report is given and the development prospects for this experiment are discusse
Probing the cosmological principle with weak lensing shear
No full textThe Cosmological Principle is a cornerstone of the standard model of cosmology and shapes how we view the Universe and our place within it. It is imperative, then, to devise multiple observational tests which can identify and quantify possible violations of this foundational principle. One possible method of probing large-scale anisotropies involves the use of weak gravitational lensing. We revisit this approach in order to analyse the imprint of late-time anisotropic expansion on cosmic shear. We show that the cross-correlation of shear Eand B-modes on large scales can be used to constrain the magnitude (and possibly direction) of anisotropic expansion. We estimate the signal to noise for multipoles 10 ≲ ℓ ≲ 100 that is achievable by a Euclid-like survey. Our findings suggest that such a survey could detect the E-B signal for reasonable values of the late-time anisotropy parameter
Salinity modulates morpho-physiology, biochemical and antioxidant defence system in tetragonia decumbens mill.: a neglected wild leafy vegetable in South Africa
No full textTetragonia decumbens is an edible halophyte that grows naturally in saline environment; however, its tolerance mechanisms are poorly understood for bio-saline agriculture. So, this research was designed to look into how salinity affects vegetative growth, leaf succulence, chlorophyll content, cation accumulation, oxidative stress indicators, and antioxidative defence mechanisms involved in the salt tolerance of T. decumbens. Saline conditions were prepared by dissolving sodium chlorine (NaCl) in the nutritive solution. The control was maintained and only watered with nutrient solution while the tested treatments contained graded NaCl doses (250, 200, 150, 100, and 50 mM). Results revealed a substantial enhancement in shoot length, number of branches, relative water content, as well as total fresh weight in plants irrigated with 50 and 100 mM NaCl in comparison to the control, while higher saline concentrations (150–250 mM NaCl) reduced plant growth and chlorophyll content. Similarly, these high salt concentrations induced more severe oxidative stress indicated by high amounts of superoxide, cell death viability and malondialdehyde, with the most pronounced effect at the highest NaCl concentration (250 mM). Nevertheless, T. decumbens modulated various defence mechanisms with increasing salinity stress, these include the upregulation of superoxide dismutase, catalase, polyphenols, flavonoids, proanthocyanidins and the build-up of sodium ions in the leaves. These results show that T. decumbens can withstand salinity by modifying its morpho-physiological traits, antioxidant defence systems, and managing ion toxicity and oxidative stress efficiently, since all plants withstand salinity without showing signs of toxicity
The use of cover crops for sustainable citrus orchard performance
No full textCover crops play a pivotal role in maintaining and improving agricultural sustainability through enriching organic matter content. They are commonly planted between tree rows to enhance soil quality, suppress weeds and improve production and fruit quality in citrus orchards. However, there is limited information regarding plantation of cover crops in citrus orchards in South Africa. Current conventional agricultural production systems in citrus orchards rely heavily on a high level of agrochemicals. This study is an attempt to alleviate some of the direct input costs and high application of agrochemicals. A cover crop field study was conducted at Lamara farm at Franschhoek, South Africa to assess the effect of cover crop species on soil quality, weed suppression, soil enzymes, citrus fruit yield and soil water content under two termination methods (slashed and non-slashed). Cover crop species tested were vetch, medics, oats and control (no cover crop). The experiment was set up in a randomised block design with a factorial treatment structure (Factor 1 - cover crop species; Factor 2 – cover crop termination methods) replicated six times. In the first study, effect of cover crop species on soil organic carbon, weed control and citrus fruit weights using two termination methods (slashed and non-slashed) were assessed. Soil samples were taken before planting cover crops and one year after planting cover crops to determine soil fertility. Dry weight samples of cover crop and weed were collected during the termination stage and fruit weight measurements were taken at harvest