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Statistical comparative performance of logistic model and proc survey in the determination of risk factors related to high blood pressure in South Africa
(University of Fort Hare, 2024-11) Mbhele, Nhlonipho Errol; Mutambayi, M.; Lala, M.
Background:
The study aims to investigate the most appropriate model for data analysis and presentation within the context of the healthcare sector in South Africa, with specific reference to hypertension. This study sets out to compare logistic regression analysis and the survey logistical model with the aim of identifying and presenting the most appropriate hypertension risk factors in the South African context.
Methods:
This study provides an analysis of secondary survey data, collected through the administration of the 2016 South African Demographic and Health Survey (SADHS). The survey was implemented by Statistics South Africa (Stats SA) with the South African Medical Research Council (SAMRC). As the nature of this study is comparative, it is appropriate to apply the identified models of healthcare analytics to a single set of data. As such, data collection comprises the acquisition of the SADHS results. The data analysis in this study comprises the application of the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) to the logistics regression model results, as well as the survey logistic model results, based on the modelsā application to the SADHS data. This study undertook a full LOGISTIC regression application, using all potential predictors of hypertension. Following the identification of potential predictors, a Random Forest was then used to determine the reduced dimension of the data. Using the relevant variables that emanated from the Random Forest algorithm, the LOGISTIC and SURVEYLOGISTIC procedures were performed to assess factors associated with hypertension and compare the model fit.
Results:
Current age showed a modest but statistically significant positive association with hypertension (AOR = 1.05, 95% CI: 1.04; 1.06). Geographical location also played a crucial role, with individuals residing in the Western Cape (AOR = 3.27, 95% CI: 1.90; 5.65), Northern Cape (AOR = 2.57, 95% CI: 1.45; 4.56), Free State (AOR = 2.66, 95% CI: 1.53; 4.63), and Kwazulu Natal (AOR = 2.07, 95% CI: 1.26; 3.42) exhibiting significantly higher odds of hypertension compared to those in Limpopo.
Moreover, socioeconomic status was a significant determinant, as individuals classified as poor (AOR = 0.43, 95% CI: 0.30; 0.61) or middle class (AOR = 0.63, 95% CI: 0.46; 0.87) had lower odds of hypertension compared to those classified as rich. Lifestyle factors also emerged as significant contributors, with non-smokers exhibiting lower odds of hypertension compared to smokers (AOR = 1.33, 95% CI: 1.05; 1.70), and individuals perceiving their own health as poor having substantially higher odds of hypertension (AOR = 2.90, 95% CI: 1.76; 4.77).
Notably, intention to reduce salt consumption was associated with decreased odds of hypertension (AOR = 0.61, 95% CI: 0.47; 0.78). Additionally, a history of CVA (AOR = 0.43, 95% CI: 0.19; 0.98) or diabetes (AOR = 0.23, 95% CI: 0.15; 0.35) were associated with lower odds of hypertension.
These findings underscore the multifactorial nature of hypertension, with implications for targeted interventions addressing geographical, socioeconomic, and lifestyle-related risk factors.
The comparison between the results obtained from the LOGISTIC and SURVEYLOGISTIC procedures for factors associated with hypertension revealed several significant findings. Firstly, current age remained consistently and significantly associated with hypertension in both procedures, with each unit increase in age corresponding to a 6% increase in the odds of hypertension (LOGISTIC: AOR = 1.06, 95% CI 1.05; 1.07; SURVEYLOGISTIC: AOR 1.06, 95% CI: 1.05; 1.07).
Additionally, the absence of a diabetes diagnosis was significantly associated with lower odds of hypertension in both procedures, with similar effect sizes and confidence intervals (LOGISTIC: AOR = 0.17, 95% CI: 0.11; 0.25; SURVEYLOGISTIC: AOR = 0.16, 95% CI: 0.11; 0.24).
Moreover, individuals who had not been diagnosed with a CVA exhibited significantly lower odds of hypertension in both procedures, with comparable effect sizes and confidence intervals (LOGISTIC: AOR = 0.37, 95% CI: 0.17; 0.81; SURVEYLOGISTIC: AOR = 0.37, 95% CI: 0.15; 0.91).
However, marital status yielded less consistent results between the two procedures. While there were some similarities in the associations between marital status categories and hypertension, the confidence intervals were wider in the SURVEYLOGISTIC procedure, indicating greater uncertainty.
The Akaike Information Criterion (AIC) values were lower for the LOGISTIC procedure (AIC = 2291) compared to the SURVEYLOGISTIC procedure (AIC = 2473), suggesting that the logistic regression model may provide a better fit to the data.
Conclusion:
This study proved that the logistic regression model is more appropriate to survey data analysis in terms of the established dataset of the 2016 South African Demographic and Health Survey, with a lower AIC, and narrower confidence intervals concerning the survey regression model.
The impact of sovereign credit rating on economic growth in selected Sub-Saharan African countries
(University of Fort Hare, 2025-08-25) Kopolo, Yanga; Makhetha-Kosi, P
This study investigates the impact of sovereign credit rating on economic growth for the period 2002-2022 in the selected sub-Saharan African countries. Panel data techniques, namely Pooled OLS, random effects, and fixed effects models, were employed. The findings of the Hausman test showed that the fixed effects model is appropriate for the study, and the results of the fixed effects model showed that sovereign credit rating has negative impact on economic growth, though the impact is not significant. However, gross fixed capital formation and government expenditure positively impact economic growth, and the relationships are statistically significant. Even though lending interest rate positively impacts economic growth, the impact is not significant. The policy recommendations are that policy makers should improve economic elements such as fiscal discipline and debt management to lessen vulnerability to rating downgrades. However, even though this study found an insignificant relationship between sovereign credit rating and economic growth, strong elements such as improvement of fiscal discipline may improve credit ratings and borrowing costs, thus indirectly increasing economic growth. In addition, governments in the sub-Saharan region should create a conducive environment which attracts investors, particularly foreign direct investment. The ability for the region to attract foreign direct investment could influence job creation which ultimately assists the region to achieve economic growth.
Design, construction and performance evaluation of a temperature-controlled underground fixed dome biodigester with an automatic stirrer
(University of Fort Hare, 2024-05) Makamure, Francis; Mukumba, P.; Makaka, G.
The negative impacts of temperature fluctuations on biogas production in anaerobic digesters are now a fact. Cold temperatures can completely paralyze bacterial activity in a digester. In uncontrolled digesters, biogas production varies throughout the day following environmental temperature variations and throughout the year following seasonal temperature variations. The challenge in household digesters is that they are generally constructed without heating mechanisms because of cost. Constant biogas supply throughout the year is thus not feasible in such digesters. Further, not all energy available in each substrate sample can be extracted without controlling operating conditions. Some of these process conditions include temperature, pH, total solids (TS), volatile solids (VS), stirring mode (SM), and chemical oxygen demand (COD). For a reliable biogas supply throughout the year, a robust heating system to heat the substrate from the centre of the biogas reactor tank and maintain a constant optimum operating temperature is key in biogas production.
The present empirical dissertation used a multidisciplinary approach to automatically maintain an operating temperature of 35 +/- 0.5 Degrees Celsius and automatically stir the substrate intermittently. An Arduino-aided electronic circuit was used to control three electrical circuits, which operated three mechanical devices: the water pump, the electric ball valve, and the stirrer. The slurry temperature was controlled by flowing hot water through the heat exchanger anchored at the centre of the temperature-controlled reactor. The other digester had no temperature control system but was stirred at the same rate and was used as a control.
This study aimed to design, construct, and assess the efficiency of a temperature-controlled and automatically stirred underground bio-digester. This is achieved by heating the slurry from the centre of the digester for uniform heat distribution. The novelty of this approach lies in the combination of the insulative properties of the soil and the automatic temperature control. Most temperature- controlled digesters studied in literature so far are surface plants. The idea of heating the digester slurry from the centre has been explored but for above ground digesters. Automation of the intermittent stirring system was another novel idea. The hypothesis of this research is: ā What is the relationship between quantity and quantity of biogas and constant digester temperature when the stirring is intermittent?ā
Two underground fixed dome digesters with curved bases, each with a volume of 6 cubic meters, were designed, dug, and constructed at the University of Fort Hare research site. One was fitted with a heat exchanger secured at the centre of the digester and a stirring mechanism. The heat exchanger was designed using 22 mm diameter copper pipes of length 1m, separation of 0.07 m, and joined with 22 mm copper elbows and soldered. The other digester was fitted with a stirring mechanism only. The heat exchanger was connected to the solar geyser using Pex-AlPex tubing via an electric ball valve (to control the hot water flow), and a solar circulation pump (to pump the water from the heat exchanger back to the geyser for re-heating). The slurry in the temperature-controlled digester was heated using solar-heated water from the geyser. The electric ball valve was controlled by an Arduino circuit which was programmed to open the electric ball valve when the average slurry temperature was below 35 Degrees Celsius and to stop hot water flow when the average slurry temperature went above 35 Degrees Celsius. The water circulation pump was synchronized to the flow of hot water such that it pumped water only when the hot water was flowing and stopped when the ball valve closed. Thus, the electric ball valve and the water pump were operated by the same signal from the Arduino circuit via the same relay.
The stirrers in each digester were controlled by an Arduino code which was programmed to stir the slurry for 10 minutes after every four hours. A signal from the Arduino switched the stirrers per the programme via an automotive relay (12V, 60-80 A).
Three temperature sensors were deployed inside each digester under the slurry, along the diameter to measure slurry temperature at the centre of the digesters and 0.3 m from either wall. Two more temperature sensors were deployed to the temperature-controlled digester, one at the hot water inlet to the exchanger and the other at its outlet. The ambient temperature was also measured. All these sensors were connected to an Arduino-aided data logger. The two digesters were fed with cow dung slurry the same day in a batch mode for a retention time of 30 days. A constant temperature of 35+/-0.5 Degrees Celsius was maintained in the temperature-controlled
digester by automatically flowing hot water when the digester temperature fell below 35 Degrees Celsius and stopping when the temperature exceeded 35 Degrees Celsius. The other digester was operating under natural conditions but stirred at the same rate as the temperature-controlled one. The amount of gas produced in the two digesters per day was measured, tabulated, and analysed in terms of quantity and quality. The digester temperatures and ambient temperature were recorded every 10 minutes in the SD card of the data logging shield, but the methane concentration and amount of gas were recorded daily at 1800hrs.
To assess the performance of the temperature-controlled digester, the amount of biogas produced, and the methane content were compared with those of the uncontrolled digester. The percentage removals of TS, VS, and COD for both digesters were also compared to see how effective they were at removing these compounds. Additionally, the ability of the temperature-controlled digester to maintain the required slurry temperature was assessed. It was discovered that the temperature-control system managed to maintain slurry temperature in the required range for 82.76 % of the time. The temperature sensor at the centre of the heated digester was predominantly registering higher temperatures than those located 0.3 m from the walls creating some temperature gradient between the centre and the wall. A maximum temperature gradient of 7 Ā°C per meter was observed. This points to the fact that the 30-rpm stirrer speed could not create enough vortex needed to sufficiently distribute the heat in the digester. A stirrer motor
with a rotational speed of 100 rpm is recommended. The temperature-controlled digester produced 33% more cumulative biogas than the uncontrolled digester during the 30-day retention time, with normalized values of 26.77 cubic meters and 18.05 cubic meters, respectively. The
temperature-controlled digester produced biogas at a daily rate of 1.72 m3
, which is 90% of the theoretical value of 1.92 cubic meters. The uncontrolled digester produced biogas at a daily rate of 1.21 cubic meters, which is 63% of the theoretical value. In the temperature-controlled scenario, the rate of
biogas production increased by 42% compared to the uncontrolled scenario. The percentage of methane concentration in the produced biogas increased by 14%, while the concentration of carbon dioxide decreased by 10% from the uncontrolled scenario to the temperature-controlled one. The results showed that the temperature-controlled digester produced a much larger amount of
biogas with higher methane content when compared to the uncontrolled digester. This indicates that maintaining a constant temperature in a bio-digester improves both the quantity and quality of the biogas produced. The study also found a significant improvement in the percentage removals of total solids (TS), volatile solids (VS), and chemical oxygen demand (COD) when moving from an uncontrolled to a temperature-controlled situation. The percentage removals of TS, VS, and COD increased by 19.26%, 16.44%, and 16.88%, respectively. The results of this research demonstrate that much quality biogas can be produced if the household digesters are fitted with a temperature control facility. Much biogas can be produced from the same
quantity of substrate if the temperature is maintained constant at the mesophilic optimum level.
The efficiency of biogas production has been enhanced by 42% with the use of temperature-controlled bio-digesters. The cost of heating in this process has been significantly reduced by utilizing solar energy. In areas where the intensity of sunlight is not strong enough, a hybrid system can be employed by combining recovered heat from electricity-generating plants with solar energy.
A mathematical model was developed for biogas yield using pH and slurry temperature as input variables. The developed model was of the form:
š (šš», šš ) = š + š (šš») + š (šš )
where, a is the y-intercept, b, and c are scaling coefficients and V is the biogas yield.
š = ā10.480 + 1,139 šš» + 0,087 šš šš¢ššļæ½
It was observed that both the slurry temperature and pH positively impacted biogas yield, with slurry temperature having a higher contribution by weight (0.1594) and pH the least contribution (0.0957) to the daily volume of biogas produced. The derived model gave a very good determination coefficient and adjusted determination coefficient values of 0.9587 and 0.9551, respectively showing its predictive power.
The ethics at the intersection of artificial intelligence and transhumanism: a personhood-based approach
(Cambridge University Press, 2024-04-08) Chimakonam, Amara Esther
In this article, I will consider the moral issues that might arise from the possibility of creating more complex and sophisticated autonomous intelligent machines or simply artificial intelligence (AI) that would have the human capacity for moral reasoning, judgment, and decision-making, and (the possibility) of humans enhancing their moral capacities beyond what is considered normal for humanity. These two possibilities raise an urgency for ethical principles that could be used to analyze the moral consequences of the intersection of AI and transhumanism. In this article, I deploy personhood-based relational ethics grounded on Afro-communitarianism as an African ethical framework to evaluate some of the moral problems at the intersection of AI and transhumanism. In doing so, I will propose some Afro-ethical principles for research and policy development in AI and transhumanism.
An innovative approach to growing youth entrepreneurship in Raymond Mhlaba Municipality, a poorly resourced South Africa region
(University of Fort Hare, 2025-08) Hani, Sikanyisele; Nzewi, O I; Sibanda, M M
In this study, the researcher examined the innovative approaches that can be used in growing youth entrepreneurship in poorly resourced areas in South Africa, in particular Raymond Mhlaba Local Municipality (RMLM) in the Eastern Cape Province. Specifically, this study examined theoretical and conceptual foundations underpinning youth entrepreneurship development in poorly resourced areas in South Africa. It assessed the role of the government and other sectors in establishing innovative approaches to growing youth entrepreneurship globally. Subsequently, identified and assessed strategies and challenges of young entrepreneurs in poorly resourced areas in South Africa and finally drew up recommendations and innovative solutions; the municipality can focus on to improve youth entrepreneurship in poorly resourced areas in South Africa. The research process was guided by the formulated research objectives and questions that strive to bring innovative approaches to growing youth entrepreneurship in poorly resourced areas. This study employed a qualitative research technique to gather innovative approaches to growing youth entrepreneurship in poorly resourced areas, especially in Raymond Mhlaba Local Municipality. Thematic analysis was utilized for data analysis. The study's findings revealed challenges entrepreneurs face when growing their businesses, such as limited access to funding, market access due to poor infrastructure, load-shedding, and upgrading marketing strategies. The study also found that an innovative approach to growing youth entrepreneurship in underserved areas is required, if effectively implemented when needed, to combine all resources or place all resources under the control of a single entity to ensure effective coordination and proper resource control. More importantly, the findings indicate that no practical innovative technique has been taken to enhance youth entrepreneurship in RMLM. Finally, recommendations were made for the municipality on how to bring more innovative approaches to growing youth entrepreneurship in poorly resourced areas.