An Investigative Study on Impact of Frequency Dynamics in Load Modeling

Load modeling plays a significant impact in assessing power system stability margin, control, and protection. Frequency in the power system is desired to be kept constant, but in a real sense, it is not constant as loads continually change with time. In much literature, frequency dynamics are ignored in the formulation of load models for the basic assumption that it does not affect the models.  In this paper, the composite load model was formulated with Voltage-Frequency Dependency (V-FD) on real and reactive powers and applied to estimate the load model. 2- Area network 4- machines Kundur test network was used for testing the developed model.  The model was trained with measurements from a low voltage distribution network supplying the Electrical Engineering department at Ahmadu Bello University, Zaria. Both training and testing data were captured under normal system operation (dynamics). To evaluate the V-FD model performance, Voltage-Dependent (VD) model was examined on the same measured data. The work makes use of the Feed Forward Neural Network (FFNN) as a nonlinear estimator. Results obtained indicate that including frequency dynamics in modeling active power reduces the accuracy of the model. While in modeling reactive power the model performance improves. Hence, it can be said that including frequency dynamics in load modeling depends on the intended application of the model

Capital Structure Choices in Services Firms: Empirical Results from Nigeria Listed Companies

The effects of the worldwide economic slump, which was largely triggered by SARS-CoV-2, have undermined the profitability of businesses. As a result, the overarching goal of this research is to look into the impact of capital structure choices on the financial performance of services firms quoted on the Nigerian Exchange Group (NGX). With an adjusted population of 11 listed services firms in Nigeria, the analysis spans from 2011 to 2020. The secondary data was collected from the annual reports of the selected enterprises and African financials, using an ex-post facto design. The generalised least square model was employed for the analysis of the data. While both retained earnings and total debt have a positive and significant influence on earnings per share, short-term and long-term debts, and equity were insignificant, according to the findings. The study, on the other hand, suggests that company executives save earnings to be spent solely on rainy days in order to minimize negative shocks that could harm a company's going-concern objective

Factors associated with abnormal glomerular filtration rate among HIV-positive children at the University of Maiduguri Teaching Hospital, Maiduguri, Nigeria

Background: Renal disease is commonly encountered in patients with HIV infection. The estimated glomerular filtration rate (eGFR) provides a good assessment of the renal function and is widely used in screening populations that are at risk of renal dysfunction. We determined the prevalence of abnormal eGFR among HIV-positive children and factors associated with it.Methods: In a cross-sectional study, children aged 15 years and below were recruited through systematic random sampling from the Paediatrics Infectious Disease Clinic of the University of Maiduguri Teaching Hospital until the desired sample size of 250 was reached. Clinical and laboratory information was obtained from the patient records and used for clinical staging and immunological classification. Serum creatinine was measured using Jaffe’s reaction and eGFR calculated using the Schwartz formula. The data obtained were analysed using SPSS version 16.Results: A total of 157 (62.8%) children were on antiretroviral therapy (HAART) for periods ranging from 1 to 168 months (mean duration 66.1 ± 46.5 months). Ninety-three (37.2%) children had advanced disease representing WHO clinical stages 3 and 4, whereas 103 (41.2%) had advanced or severe immunosuppression. The mean eGFR of the study population was 102 ± 41 mL/min/1.73 m2. Fifty-two children (20.1%) had low eGFR (<2 SD below the mean eGFR for age and sex) and 6 (2.4%) had high eGFR (>2 SD above the mean eGFR for age and sex). A total of 23 (9.2%) children had moderate to severe renal impairment, defined as eGFR <60 mL/min/1.73 m2. Age, sex, socio-economic status, mode of transmission as well as history of HAART usage were not significantly associated with abnormal eGFR. However, relatively shorter duration of treatment with HAART, as well as advanced clinical or immunological stage were all significantly associated with abnormal eGFR.Conclusion: Renal dysfunction is common among children with HIV disease in Maiduguri with over a third of those affected having moderate to severe renal dysfunction. Abnormal renal function is more frequent among children with advanced clinical and immunological disease. We recommend the regular determination of eGFR and early initiation of HAART in all children with HIV disease

Metabolic syndrome in urban city of North-Western Nigeria: prevalence and determinants

Introduction: The aim of this study was to investigate the prevalence of metabolic syndrome in Sokoto metropolis of North-Western Nigeria.Methods: A cross-sectional community based study was carried out. Four hundred and ten subjects (201 males and 209 females) were recruited for the study using a multi-stage sampling technique. Demographic and the life style data was obtained from the participants. Evaluation of anthropometric variables, fasting blood sugar, lipid profiles, insulin resistance and blood pressure was performed. The classification of metabolic syndrome was based on the NCEP ATP III guidelines.Results: The mean (SD) age of the sample population was 39.6 (14.4) years. The mean (SD) age of the male subjects was 38.4(14.9) years and that of the females was 40.8(13.9) years (p> 0.05). The overall prevalence of metabolic syndrome was 35.1% with the females having 42.83% and the males 27.36%. The frequencies of metabolic syndrome parameters in the study subjects were low HDL (56.1%),  hypertension (46.1%), dysglycemia (32.7%), central obesity (28%), and elevated triglycerides (22.4%). Most of the women had low HDL (62.2%) and central obesity elevated (49.8%). Conclusion: Metabolic syndrome is common in residents of North- Western Nigeria, commoner in the females than males. Risk factors for metabolic syndrome should be detected in normal individuals for implementing effective preventive measures.Key words: Metabolic syndrome, dyslipidemia, obesit

Oxidative stress and outcome of antioxidant supplementation in patients with polycystic ovarian syndrome (PCOS)

Background: PCOS is a condition with significant decrease in antioxidant with an increased risk of oxidative stress. Antioxidant supplementation has been shown to improve insulin sensitivity in PCOS and may improve outcome of management of PCOS. Objectives of this study were to determine the oxidative stress level of PCOS patients, to assess the effect of antioxidant supplementation on the outcome of management of PCOS and to compare with a control group.Methods: The study was a single blind randomised control trial involving 200 patients with PCOS. The study was conducted at Usmanu Danfodiyo University Teaching Hospital Sokoto. They were randomly divided into intervention and control groups and base line serum levels of oxidative stress marker, antioxidant enzymes, vitamins and minerals were determined. Antioxidant supplementation and placebo were given to the intervention and control groups respectively. All the patients had ovulation induction with clomiphene citrate and were followed up for 6 months. Outcome measures were clinical pregnancy or menstrual regularisation. Level of significance was <0.05.Results: There was statistical significance in the serum levels of oxidative stress marker, antioxidant enzymes, vitamins and minerals between the two groups (post intervention). Glutathione peroxidase (p = 0.001), superoxide dismutase (p = 0.0001), catalase (p= 0.0369), melondialdehyde (p= 0.007), Vitamin A, Vitamin C, Vitamin E (p = 0.0001), zinc and copper (p = 0.0001). The clinical pregnancy outcomes were 22 (22%) versus 2 (2%); live births 18 (18%) versus 2 (2%) and menstrual regularisation 48 (48%) versus 46 (46%) in the intervention and control groups respectively.Conclusions: Antioxidant supplementation in this study significantly affected pregnancy rate in patients with PCOS. Larger studies are suggested to revisit the conclusion of the Cochrane review that antioxidants supplementation had no significant role in female infertility

Epidemiology of COVID-19 and Predictors of Outcome in Nigeria: A Single-Center Study.

There is a paucity of information regarding the epidemiology and outcome of COVID-19 from low/middle-income countries, including from Nigeria. This single-center study described the clinical features, laboratory findings, and predictors of in-hospital mortality of COVID-19 patients. Patients admitted between April 10, 2020 and June 10, 2020 were included. Forty-five patients with a mean age of 43 (16) years, predominantly male (87%), presented with fever (38%), cough (29%), or dyspnea (24%). In-hospital mortality was 16%. The independent predictors of mortality were hypoxemia (adjusted odds ratio [aOR]: 2.5; 95% CI: 1.3-5.1) and creatinine \u3e 1.5 mg/dL (aOR: 4.3; 95% CI: 1.9-9.8)

Summaries of Causes, Effects and Prevention of Solar Electric Fire Incidents

Currently the number of fire incidents involving photovoltaic (PV) systems are increasing as a result of the strong increase of PV installations. These incidents are terrible and immeasurable on life and properties. It is thus very important to understand the causes, effects and how prevent the occurrence of incidents. This study aimed to summarize the causes, effects, and preventions of solar electric fire incidents. Literature review was adopted to summarize the study. The summarized and discussed result from literature found that arcing, hot spot, weather conditions, improper installations and maintenance, and systems mechanical and electrical failures are the main causes solar PV fire incidents. The effects of incidents are terrible on life and properties. The result also discussed the precautionary measures in detail on how to prevent PV systems and firefighters before and during fire incidents. Therefore, it is expected that the study is comprehensive for manufacturers, installers, professionals to build and improve understanding of causes, effects and prevention of solar electric fire incidents in residential, industrial and commercial applications

Toxicity of Radon-222 in Groundwater across Keana in Nasarawa, Nigeria

The most common supply of freshwater for drinking, irrigation, and other domestic uses is groundwater; however, because of increased radon concentrations brought on by mining activities, its quality is still a severe concern. Using a liquid scintillation detector, this study investigated the radon content, its related toxicity, and its risk to human health in the groundwater of the Keana in Nasarawa, Nigeria. Ten (10) borehole samples and five (5) well samples totaling fifteen (15) groundwater samples were taken. The results showed that the average radon concentration in water samples from Keana was 2.25 Bq/L. The mean annual effective dosage (ingestion) for adults and children in Keana was 0.016 mSv/y and 0.027 mSv/y, respectively. In Keana, the additional lifetime cancer risk per adult was 5.65 × 10–5, and per child, it was 8.79 × 10–5. The study’s radon concentration was lower than the benchmark of 11.1 Bq/L established in 1991 by the Nigerian Standard Organization and the US Environmental Protection Agency. The results of this study indicate that the level of radon is safe; as a result, people can continue farming and other activities. To reduce the risk of cancer, however, more research could be done in the area. Further research should be done by looking at additional sources in the study area in order to cover the entire zone. Further investigation should be carried out both during the dry and wet seasons because radon concentrations in groundwater alter over time due to dilution by recharge from rainfall

Clinical and gross-pathological changes in Muscovy ducks and Nigerian local chickens infected with Newcastle disease virus (XIVb strain)

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Oxidative stress and outcome of antioxidant supplementation in patients with polycystic ovarian syndrome (PCOS)

Background: PCOS is a condition with significant decrease in antioxidant with an increased risk of oxidative stress. Antioxidant supplementation has been shown to improve insulin sensitivity in PCOS and may improve outcome of management of PCOS. Objectives of this study were to determine the oxidative stress level of PCOS patients, to assess the effect of antioxidant supplementation on the outcome of management of PCOS and to compare with a control group.Methods: The study was a single blind randomised control trial involving 200 patients with PCOS. The study was conducted at Usmanu Danfodiyo University Teaching Hospital Sokoto. They were randomly divided into intervention and control groups and base line serum levels of oxidative stress marker, antioxidant enzymes, vitamins and minerals were determined. Antioxidant supplementation and placebo were given to the intervention and control groups respectively. All the patients had ovulation induction with clomiphene citrate and were followed up for 6 months. Outcome measures were clinical pregnancy or menstrual regularisation. Level of significance was &lt;0.05.Results: There was statistical significance in the serum levels of oxidative stress marker, antioxidant enzymes, vitamins and minerals between the two groups (post intervention). Glutathione peroxidase (p = 0.001), superoxide dismutase (p = 0.0001), catalase (p= 0.0369), melondialdehyde (p= 0.007), Vitamin A, Vitamin C, Vitamin E (p = 0.0001), zinc and copper (p = 0.0001). The clinical pregnancy outcomes were 22 (22%) versus 2 (2%); live births 18 (18%) versus 2 (2%) and menstrual regularisation 48 (48%) versus 46 (46%) in the intervention and control groups respectively.Conclusions: Antioxidant supplementation in this study significantly affected pregnancy rate in patients with PCOS. Larger studies are suggested to revisit the conclusion of the Cochrane review that antioxidants supplementation had no significant role in female infertility