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

Modelling Growth Kinetics of Klebsiella sp. FIRD 2 on TBT-Resistant Containing Lead

Tributyltin (TBT) is one of the most toxic substances ever deliberately introduced into the marine environment. The high toxicity of TBT has resulted in a wide range of adverse effects on biological systems ranging from bacteria to mammals and from the molecular to the community level. One of the most deleterious effects of TBT is imposex. The growth kinetics of TBT-Resistant Bacterium containing lead was studied. In this study various lead concentrations ranging from 1 to 100 mg/dm3 were used. Seven kinetic models (Teissier, Monod, Yano, Luong, Aiba, Webb, and Haldane,) were investigated and the accuracy of the fitted models were evaluated using statistical analysis such as coefficient of determination, adjusted coefficient of determination (R2) and root mean square (RMSE). Aiba model was fitted to the experimental growth kinetics data and gave a very good fit with an R2 of 0.98 and RMSE of 0.0042 respectively. The calculated value for the Aiba constants such as maximal growth rate, half saturation constant and half inhibition constant rate symbolized by μmax, ks, and ki, were 0.038 hr-1, 0.38s mg/dm3 and 34.38 mg/dm3respectively. This is the first report of growth kinetics of TBT-Resistant bacterium by Klebsiella sp. FIRD 2 Containing lead.Keywords: Growth Kinetic models, Klebsiella sp. FIRD 2, lead, TBT-resistant bacteria

Uloga sijalične kiseline na površini eritrocita u nastanku anemije u jaraca Savannah smeđe pasmine.

Erythrocyte surface sialic acid, free serum sialic acid concentrations and sialidase activity were determined during experimental Trypanosoma evansi infection in Savannah Brown bucks. All infected bucks developed trypanosomosis, with significant decreases in mean packed cell volume to as low as 19.50 ± 2.12% occurring at day 33 post-infection and was significantly lower than the control value of 26.75 ± 0.96. Mean haemoglobin concentrations also declined in the infected bucks with a marked drop of 6.50 ± 0.70 g/dL on day 33 post-infection and was significantly different (P<0.05) from the uninfected (control) group (8.53 ± 0.46 g/dL). The anaemia was preceded by a gradual decline in mean erythrocyte surface sialic acid concentrations occurring 5 days post-infection. There were significant differences (P<0.05) in mean erythrocyte surface sialic acid between the infected and control groups on day 5 and between days 17 to 27 post-infection. A significant (P<0.05) increase in free serum sialic acid concentrations was observed on days 15, 17 and 27 when compared to the control group. There was a significant (P<0.05) increase in the activity of sialidase on days 7, 9, 21, 23, 27, 33 and 37 post-infection.The anaemia caused during infection may be attributable to the activities of the circulating trypanosomes, which produce sialidase (neuraminidase) that resulted in the cleaving off of erythrocyte surface sialic acid, rendering such red blood cells more prone to phagocytosis in the reticuloendothelial system.U jaraca Savannah smeđe pasmine, u tijeku pokusne zaraze tripanosomom Trypanosoma evansi, određivana je koncentracija sijalične kiseline na površini eritrocita, zatim koncentracija slobodne sijalične kiseline u serumu te aktivnost sijalidaze. Svi invadirani mužjaci oboljeli su od tripanosomoze sa značajnim opadanjem srednje vrijednosti hematokrita do vrijednosti 19,50 ± 2,12%. Navedeni je pad uslijedio 33 dana nakon infekcije i bio statistički značajan u odnosu na kontrolnu vrijednost 25,75 ± 0,96. Srednja koncentracija hemoglobina također je pala u invadiranih mužjaka s najizraženijim padom od 6,50 ± 0,70 g/dL 33. dana nakon zaraze. Ta vrijednost bila je također značajno različita (P<0,05) u odnosu na kontrolnu skupinu jaraca (8,53 ± 0,46 g/dL). Petoga dana nakon infekcije, anemija je nastavljena postupnim opadanjem srednje koncentracije sijalične kiseline na površini eritrocita. Utvrđene su značajne razlike (P<0,05) u srednjoj koncentraciji sijalične kiseline na površini eritrocita između zaražene i kontrolne skupine 5. dana, te između 17. i 27. dana nakon infekcije. U usporedbi s kontrolnom skupinom, u zaraženih životinja utvrđen je signifikantan (P<0,05) porast koncentracije slobodne sijalične kiseline u serumu 15., 17. i 27. dana. Aktivnost sijalidaze bila je značajno (P<0,05) povišena 7., 9., 21., 23., 27., 33. i 37. dana nakon infekcije. Pojava anemije tijekom infekcije može se povezati s aktivnošću tripanosoma u krvnom optjecaju koji tvore sijalidazu (neuraminidazu), a time i cijepanje sijalične kiseline na površini eritrocita čineći ih podložnijima za fagocitozu u retikuloendotelijalnom sustavu

Isolation and Molecular Characterisation of Polycyclic Aromatic Hydrocarbons (PAHs) Degrading Bacteria from Petrochemical Contaminated Soil

Because of their ubiquitous nature, polycyclic aromatic hydrocarbons (PAHs) are widely dispersed in the environment as a result of both natural and human processes. One of the ways to deal with the harmful effects of these chemicals is through the use of microorganisms capable of degrading the pollutants. A petrochemical contaminated site was searched for these microbes. Eleven bacterial strains were obtained in this work using the culture enrichment technique on Bushnell Hass medium supplemented with (naphthalene, anthracene, and phenanthrene) as the only source of energy. Enumeration utilizing the spread-plate technique and liquid media were used to examine the PAH breakdown capacities of bacterial strains. The isolates were identified using standard methods of morphological and biochemical identifications. Furthermore, 16sRNA was utilized in order to classify the isolates at molecular level. The presence of PAHs degrading genes was also analysed in the isolates. Four isolates (G1, G2, G5, and G6) out of a total of eleven were able to tolerate and degrade the test PAH's up to 600 mg/l in liquid media. Isolate G1 showed the highest growth during screening followed by G6 while there were no differences between the other two isolates as demonstrated by an increase in their optical densities after 120 hours of incubation. Based on 16S rRNA gene sequences and molecular phylogenetic analysis, the isolate was identified as Pseudomonas stutzeri, Stenetrophomonas sp, Pseudomonas lactis, and Achromobacterxylosoxidans with the accession numbers OM039162, OM52851, OM52852, and OM52853 respectively. Fragments of 350 bp, 350 bp, and 867 bp for ring hydroxylating dioxygenase (RHD), hydratase-aldolase, and catechol 2, 3-dioxygenase were obtained from partial PCR amplification of catabolic genes, demonstrating the presence of a PAH degradation pathway in the organisms. These isolates have great potential for application in the bioremediation of PAHs-contaminated sites

Subjective reasons for COVID-19 vaccine hesitancy and sociodemographic predictors of vaccination in Nigeria: an online survey

The purpose of this study was to examine the subjective reasons for hesitancy to receive COVID-19 vaccination and the sociodemographic factors associated with vaccination uptake. An online social media survey was conducted among the general Nigerian population using a self-developed questionnaire. Data were analyzed using binary logistic regression with crude and adjusted odds ratios (AOR) at a 95% confidence interval (CI) and a p value of less than 0.05. A total of 576 participants with a mean age of 31.86 years participated in the study. 28% (n = 158) received one or more doses of the COVID-19 vaccine. Teachers were significantly less likely than health professionals to be vaccinated (AOR = 0.33, 95% CI 0.16&ndash;0.69). In addition, unemployed people (AOR = 0.37, 95% CI 0.15&ndash;0.89) were less likely to be vaccinated than government employees, and those of intermediate socioeconomic status (AOR = 0.47 95% CI 0.26&ndash;0.88) were less likely to be vaccinated than were those of high socioeconomic status. Five main themes emerged regarding participants&rsquo; subjective reasons for hesitating to receive the COVID-19 vaccine: fear related to vaccine content (e.g., efficacy), negative effects on the body (e.g., blood clots), distrust of the system/government (e.g., politics), psychological concerns (e.g., anxiety), and misconceptions. Sociodemographic variables and vaccine misconceptions were found to play an important role in COVID-19 vaccination coverage in Nigeria

Circular economy potential and contributions of petroleum industry sludge utilization to environmental sustainability through engineered processes - a review

The petroleum industry activities unavoidably generate a large quantity of sludge named Petroleum industry sludge (PIS). The generation rate has been increasing because of the ascending energy demand. It is a potential energy resource. PIS has been shown to contain hazardous constituents that may have negative consequences on the environment and public health. Thus, the treatment and disposal of this waste is a global issue. Numerous treatment methods have been demonstrated to reduce sludge volume and toxicity and recover petroleum components. The sludge qualities affect how effective they are. These treatment strategies can reduce the toxic substances in sludge and reduce their detrimental effects on human health and the environment. However, because of the sludge's tenacious character, only a few technologies can meet strict environmental laws while using a sizable amount of water, electricity, and chemicals. PIS treatment methods that are both waste-free and cost-effective are currently unavailable. In terms of environmental engineering significance, this study adopted the systematic review to discuss the waste to resource potential applications of PIS for reusability in sustainable construction, wastewater treatment applications, and gas generation. PIS application ineffective microorganism biofertilizer production, levan production, rubber tires manufacturing, metal catalysts synthesis, carbon–clay composites for use in sensors and electronic devices were also discussed. That is not enough, this review also found that the adoption of the circular economy that represents a new direction to create value and prosperity by elongating product lifespan and moving the waste from the end of the supply chain to the outset is very important. Thus, the circular economy potential of PIS to achieve self-cycle operation through the concept of “wastes-treat-wastes” in the petroleum industry was extensively discussed