Scientific African最新文献

This study evaluated catabolic gene expression as an index of hydrocarbon breakdown in ultisol treated with Bacillus altitudinis-Cropped Biofertilizers derived from Biosolid and Brewer Spent Grain (BSG) using phenotypic and molecular methods. We observed significant reductions in Total Petroleum Hydrocarbons (TPH) concentrations with both amendments, albeit the biosolid based amendment was markedly more effective. Concurrently, there was a substantial increase in hydrocarbon-degrading bacteria. Notably, the bulk of Operational Taxonomic Units (OTUs) in biosolid (95.77 %) and BSG (93.00 %) amended Ultisol were Proteobacteria, Acidobacteria, Actinobacteria, and Planctomycetes, which are key players in hydrocarbon bioremediation. We observed the presence of eleven hydrocarbon-degrading genes through M5nr analysis. These genes encompass essential catalysts for aliphatic hydrocarbon degradation and hydrocarbon desulfurization. Notably, these enzymes/genes include Bacterial Flavin-bound Monooxygenase (AlmA), Alkane Monooxygenase (AlkM), Alpha Ketoglutarate Dependent Dioxygenase (alkB), Propane Monooxygenase (PrM), Cytochrome P450 (cP450), Methane Monooxygenase/Ammonia Monooxygenase (MMO/AMO) subunits A, B, and C, Alkane Sulfonate Monooxygenase (ssuD), Alkane Sulfonates Transport System Permease Protein (ssuC), Dibenzothiophene Monooxygenase (dszC), Dibenzothiophene-Sulfone Monooxygenase (dszA), and Dibenzothiophene-5,5-Dioxide Monooxygenase (dszB). These genes play pivotal roles in the degradation of aliphatic hydrocarbons and hydrocarbon desulfurization. Interestingly, unique gene expression patterns were observed for each amendment, with Actinomycetales and Bulkhoderiales orders expressing the majority of identified genes. These findings have revealed the amendment-specific microbial and genetic alterations and, the diversity and potential of the annotated genes induced by the Bacillus altitudinis-Cropped Biofertilizers (biosolid and BSG amendments) for effective remediation of hydrocarbon-contaminated soils.

Objectives

The resistance of bacteria to current antibiotics is a significant concern in treating infectious diseases, posing a strong threat to global health, food security, and development. This underscores the need for synthesizing new heterocyclic compounds as potential lead candidates in drug discovery. Quinoxalinone derivatives, known for their presence in various therapeutic agents and clinical drugs, are of particular interest. This study aimed to synthesize angular tricyclic tetrahydrocycloamino [1,2-a]quinoxalin-4-one derivatives and evaluate their antibacterial activities.

Methods/analysis

The synthesis began with preparing precursors through the condensation of substituted 1-halogeno-2-nitrobenzene and cyclic amino acids in the presence of a base in ethanol, forming 2-nitrophenyl pyrrolidine/piperidine-2-carboxylic acids (acid adducts) 3a-3j. These acid adducts were then converted to amino esters 4a-4e by reacting them with thionyl chloride/ trimethylchlorosilane and methanol. Intramolecular reductive cyclization of the acid adducts or esters produced tetrahydrocycloamino [1,2-a]quinoxalin-4-ones (5a-5j) through catalytic hydrogen transfer hydrogenation. The chemical structures of the synthesized compounds were confirmed using FTIR, 1H and 13C NMR, MS, and CHN analysis. Their in vitro antibacterial activities were evaluated against ten bacterial strains using the broth microdilution method, revealing moderate to excellent activities compared to standard antibiotics streptomycin (STM) and nalidixic acid (NLD).

Findings

Compound 5g demonstrated significant antibacterial activity (MIC = 15.6 μg/mL) against S. epidermidis, and compound 5c exhibited activity (MIC = 31.3 μg/mL) against S. aureus, both compared to STM and NLD. The results suggest that some of these compounds with promising antibacterial activity could serve as leads for discovering new antibacterial drugs.

Novelty/improvement

The tetrahydrocycloamino [1,2-a]quinoxalin-4-ones were prepared using two methods with higher yields than previously reported, with the second method being novel for synthesizing quinoxalin-4-ones. The in vitro antibacterial studies of these compounds were reported, and substituted quinoxalin-4-ones were synthesized from N’-ethyl-N-(2-nitrophenyl)pyrrolidine-2-carboxamide 7 in good yield.

This study proposes a combined approach involving climate change scenarios and varied land use and land cover (LULC) projections in a semi-arid watershed (El Grou) located in Morocco. The Soil and Water Assessment Tool (SWAT) model was coupled with land use scenarios generated using the Cellular Automata-Markov model for three dates (2030, 2040, and 2050) and future climate projections from the CMIP5 model under RCP 4.5 and 8.5 scenarios. Future precipitation and temperature projections indicate a decrease in annual precipitation by 5 % to 34 % and an increase in average temperatures, particularly during the summer months. LULC changes reveal a significant decline in agricultural lands and forests, with an expansion of bare soil by 2050. These changes, analyzed through three SWAT models representing different time periods, indicate a decrease in surface runoff by 41 % to 73 %, a reduction in total water yield by 21 % to 53 %, and a decline in groundwater recharge, posing significant challenges for water resource management and ecosystem health. The study underscores the need for integrated land and water management strategies, incorporating climate change adaptation measures, to ensure sustainable water resource utilization and build resilience in the El Grou watershed and similar semi-arid regions.

Indoor air quality (IAQ) in confined spaces like bank vaults and basements is influenced by complex factors such as building layout and HVAC systems. This study examines how mechanical ventilation impacts IAQ in a bank building's occupied basement vault, addressing significant challenges posed by pollutant exposure in these air-tight environments. This study advances safe IAQ in confined spaces, crucial for occupant health and safety, using CFD (ANSYS Fluent Workbench 16.0) and CONTAM 3.2 software for multi-zone ventilation and air quality analysis. It analysed three indoor pollutants: Radon (Rn), Carbon dioxide (CO₂), and Particulate Matter (PM2.5), enhancing the reliability and applicability of the findings. The findings indicated that the simulated indoor pollutants concentrations did not exceed the indoor air quality guideline levels. The CFD simulations predicted average steady-state values of 27.2 Bq/m³ for Radon, 574.80 ppm for CO₂, and 69.36 µg/m³ for PM_2.5 in the basement. For different outdoor air floor rates, an optimal ventilation rate of 4.7 ACH and a cooling load of 17 kW were determined to maintain Radon concentrations below 15 Bq/m³. This provides a practical and actionable solution for maintaining safe IAQ in confined spaces, which is a significant step forward compared to similar studies. These results align with other experimental research, validating the use of numerical techniques in indoor air quality studies. By optimizing HVAC systems to maintain IAQ and minimize energy consumption, the study supports SDG 7 (Affordable and Clean Energy) by enhancing energy efficiency, SDG 3 (Good Health and Well-being) by reducing exposure to indoor pollutants, and SDG 11 (Sustainable Cities and Communities) by improving air quality management in confined spaces. The findings are particularly relevant for Africa, offering practical solutions, informing policy direction, and supporting the African Union's Agenda 2063 and SDGs 3, 7, and 11.

In recent years, various energy sources and methods have been used to heat water in domestic and commercial buildings. Water heating methods for large households or commercial buildings include electrical heating elements, gas heaters, and solar energy (solar concentrators, flat plate collectors, evacuated tube collectors, etc.). In recent decades, the focus of water heating has shifted to solar energy, which is abundantly available in most African countries. The weather condition of a region has a huge impact on the system's performance. South Africa is characterised by four different weather seasons (winter, spring, summer, and autumn), unlike most African countries. Therefore, this study focuses on the impact of weather seasons on the system's performance for water heating through the combined use of solar energy and solar concentrator techniques. The system performance was modelled by using Matlab Simulink®, where historical weather data for Pretoria, South Africa, was fed into the model. Based on the weather data input, the system behaviour varied per season due to the change in solar intensity. The average outlet temperatures of the absorber, in the order of magnitude, were 333, 332, 328, and 325 K during the autumn, summer, spring, and winter seasons, respectively. Similarly, the average storage tank temperatures, in the order of magnitude, were 366, 364, 363, and 360 K in spring, summer, autumn, and winter, respectively. From this study, it is concluded that the different weather seasons in South Africa, have a direct impact on the performance of the system. Irrespective of the season, the system produced the required volume of hot water required throughout the year.

Oxidative stress plays a major role in the pathogenesis of many diseases like diabetes, cancer, cardiovascular diseases, and neurodegenerative diseases. Oxidative stress has become a potential for therapeutic target in the prevention and management of such diseases. This has spiked the interest in the use of natural antioxidants for disease prevention. The present study was aimed at assessing the antioxidant and cytotoxic properties of sequentially extracted Euclea natalensis leaf extracts. The total phenolics and flavonoids were estimated, and antioxidant activity was determined using 2,2-diphenyl-1-picryl hydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS), total antioxidant capacity, and the ferric reducing/antioxidant power (FRAP) assays. The cytotoxic capacity against HeLa cells was evaluated using WST-1 (4-[3-(4-Iodophenyl)-2-(4-nitro-phenyl)-2H-5-tetrazolio]-1,3-benzene sulfonate) colorimetric assay. Qualitative phytochemical screening showed the presence of phytochemicals such as phenols, flavonoids, tannins, terpenoids and glycosides except in the hexane extract. The total phenolic and flavonoid content ranged from 0.58–118.7 mg GAE/g DW and 9.8–20.1 mg GAE/g DW respectively. All extracts displayed a concentration-dependent inhibition of DPPH and ABTS, with IC₅₀ values in the range 0.04–0.122 mg/mL and 0.079–0.205 mg/mL respectively. The aqueous extract had the highest total antioxidant capacity and ferric reducing power of 40.4 mg AAE/g DW and 0.98 mg Vitamin C equivalence/g DW. The IC₅₀ value for cytotoxicity was in the range 155.3–211.3 mg/mL with the dichloromethane-methanol extracts being the least cytotoxic. It was concluded that Euclea natalensis leaf extracts contain bioactive phytochemicals with antioxidant potential and less cytotoxic capacity.

The complex relationship between corruption, economic growth, and labor dynamics has long been a challenge for policymakers. This study sheds new light on these dynamic interactions by constructing a novel economic model with saturation effects that integrate employment considerations. Unlike static or purely empirical models, our approach captures the system’s evolution over time, employing a logistic growth function to realistically reflect economic limitations and distinguishing between employed and unemployed labor segments. By incorporating a Holling type II function, the model captures the nonlinear influence of corruption on economic growth, acknowledging diminishing returns at higher corruption levels. Through advanced theoretical analysis, we establish the existence and stability conditions for three distinct long-term equilibria: stagnation, corruption-free growth with full employment, and a coexistent state where corruption persists alongside some economic activity. Our analysis goes beyond merely identifying these equilibria by revealing the specific conditions under which each state prevails, and we solidify these theoretical predictions with comprehensive numerical simulations depicting the system’s behavior under varying conditions. The findings underscore the importance of robust anti-corruption measures and a labor-intensive economic approach, highlighting that fostering growth outpacing resource depletion is crucial for escaping stagnation and achieving sustainable development. Overall, this research advances the field by integrating employment dynamics, a Holling type II function for corruption, and a focus on stability analysis, providing invaluable insights for policymakers aiming to promote sustainable economic development, combat corruption, and ensure healthy employment conditions.

Amidst persistent inflationary pressures in Africa and central banks raising rates to counter inflation, leading to a shift from stocks to alternative assets and impacting stock return volatility, this paper investigates the influence of inflation on stock return volatility in five African countries using the GARCH-MIDAS approach, using mixed data of daily and monthly frequencies. We observe that inflation is important for stock return volatility, as higher inflation increases volatility and reduces returns. Our results provide a better understanding of the dynamics of stock market volatility while accounting for the role of inflation, using the natural frequencies of the variables. Our findings encourage monetary authorities to communicate their inflation expectations to the market participants/investors to moderate negative stock return volatility.

Background

Blood transfusion is a critical hemotherapeutic intervention. However, the widespread utilization of Rapid Diagnostic Test (RDT) methods in screening potential donors for TTIs poses a serious public health challenge. We investigated the prevalence of TTIs in donor blood units that were transported from external health facilities (Trans-in blood) to Ho Teaching Hospital for critical care.

Method

We adopted a cross-sectional design to investigate 727 units of Trans-in blood at the Ho Teaching Hospital's blood bank between January 1, 2021, to December 31, 2022. An apriori-developed data capture form was used to collect the data for this study. The chi-square test and Cramer's V or Phi were used to assess the association between variables of interest. Binary logistic regression analysis was used to determine the association between TTIs and donor's blood groups whereas spatial visualization was employed to present the distribution of missed TTIs.

Results

The overall prevalence of missed TTIs was 6.19 % (95 % CI: 4.66–8.18), comprising missed HIV, HBV, and Syphilis infection rates of 1.79 % (95 % CI: 1.72–1.86), 1.24 % (95 % CI: 1.17–1.31), and 3.16 % (95 % CI: 3.09–3.23), respectively. There was a higher rate of missed HIV infections in 2022 (2.04 %, 95 % CI: 1.04–3.97) compared to 2021 (1.49 %, 95 % CI: 0.64–3.45), and a decline in the rates of missed HBV and Syphilis infection within the period. The prevalence of TTI was highest among donors with ABO blood group 'O' (68.89 %, 95 % CI: 54.34–80.47) and Rh 'D' Positive blood group (95.56 %, 95 % CI: 85.17–98.77). Compared to donors with blood group O, non-O donors had 4.53 times the odds (95 % CI: 1.12–18.27; p-value=0.034) of missed HBV infection.

Conclusion

The observed prevalence of missed TTIs highlights potential gaps in current screening practices, posing a significant public health concern. Efforts made to clamp down on the spread of these infections within the population may be impeded if the current trend of missed TTIs continues. Further studies on a larger scale with more comprehensive data are advised to better appreciate the public health implications of missed TTIs in Ghana.

A debilitating disease such as malaria has been a global health challenge for a long time. Mathematical models have provided insights on how best to control, prevent, or eradicate the disease. Most of the models used parameters to represent control strategies. The current research aims at using control strategies as disease compartments for both vector control and human-protection. By this, the long-time evolution of containment measures can be assessed. Consequently, a model of nine disease compartments is constructed using first-order ordinary differential equations. A qualitative analysis of the malaria-free equilibrium was carried out. The results indicate that the malaria-free equilibrium state is locally and globally asymptotically stable when $R_{0HV}<1$, which implies that the disease-free state will always be attained from any initial conditions. A bifurcation analysis also shows that the malaria-endemic and malaria-free equilibria cannot overlap. Numerical simulations show that vector control is more effective in the containment of malaria than human-protection, which confirms the findings of Ross 53 years ago. Numerical results also show that solutions attain a disease-free steady state with time, which agrees with the theoretical results. The implication of the findings is that more attention should be paid to vector control if malaria is to be eradicated.