Elevated radiation fields from dumpsites in Lagos Nigeria – waste management concerns and the way forward

This paper is a rider to the reported high gamma radiation fields around certain ordinary waste sites in Lagos, Nigeria. Exposure groups in the vicinity of these sites are susceptible to radiation risks, among other possibilities of health and environmental hazards, as a result of the waste volumes. Urbanisation requires environment-conscious waste management, especially e-wastes. This study relates Nigeria’s sub-standard waste management to the wider world. There is need for an integrated solid waste management approach.     

Corrosion behaviour and mechanism of 6082 aluminium alloy in NaCl and Na2SO4 etchants

The corrosion behaviour of 6082 aluminium alloy was studied by measuring the electrochemical impedance spectra and electrode polarization curves. After the electrochemical tests, a microstructural analysis of the samples was conducted by using optical microscopy and electron scanning microscopy techniques to determine the corrosion mechanism. The results show that the Nyquist plot of the electrochemical impedance data in the NaCl solution consists of high- and low-frequency capacitive impedance loops. When ions are added to the NaCl etchant, the Nyquist plots of the electrochemical impedance data are composed of two different curves: a high-frequency capacitive impedance loop and a low-frequency inductive impedance loop. The corrosion current density increases with increasing concentration, and as a result, the corrosion resistance of the aluminium alloy decreases. The microstructures of 6082 aluminium alloy consist of Mg₂Si secondary particles in a large α-Al matrix. Pitting corrosion initially occurs at the boundary between the matrix and secondary particles because the electrode potentials of the matrix and secondary particles are different. Then, corrosion paths develop along the network-like grain boundaries, and finally, massive network-like corrosion occurs throughout the entire alloy.     

One-pot room temperature synthesis of biopolymer-capped ZnSe nanoparticles

The synthesis of monodispersed, starch-capped ZnSe nanoparticles via a facile, “green” and environmentally benign route at room temperature is being reported. The nanoparticles exhibited strong quantum confinement effect with respect to the bulk ZnSe. The transmission electron microscopy (TEM) image indicated that the particles were well dispersed and spherical in shape. The X-ray diffraction (XRD) analysis showed that the ZnSe nanoparticles were of the wurtzite structure, with average particle diameter of about 3.50 nm. The Fourier transform infrared (FT-IR) spectrum confirmed the presence of starch as passivating agent.     

Gamma dose profile and risk to scavengers and occupants near waste dumpsites in coastal Nigeria

Radioactive waste handling and disposal are a major topic in radiation protection. The comparative survey of gamma radiation exposure in the vicinity of some ordinary, general waste dumpsites in this study indicates that they could also pose radiation health hazards. The mean Absorbed Dose Rate (ADR) from all the dumpsites was 309 ± 2.12 nGy h^?1. The ADR near the landfills was higher than those of e-waste, metal scraps and municipal solid waste dumpsites. The results also show that the waste dumps contribute to the gamma ADR in their vicinity. ANOVA revealed that ADR at different distances from each of the dumpsites had a statistical variation at the 0.05 significance level. The scavengers and occupants of shanties near the dumpsites receive annual effective doses above the value accepted worldwide average of 0.07 mSv.     

Stress corrosion behavior of 6082 aluminum alloy

Stress corrosion tests of 6082 aluminum alloy were carried out by using a three-point bending fixture while holding at 50% of yield strength state through different immersion times in 1.5% NaCl electrolyte solution. The electrochemical impedance spectra and dynamic electric potential polarization curves were measured to indicate the stress corrosion behavior of the alloy. Optical microscopy, scanning electron microscopy, and X-ray energy spectrum analysis were applied for microstructural investigations. The results show that all of the Nyquist electrochemical impedance spectra consisted of high- and low-frequency double capacitive arcs. However, an increase in immersion time while holding at 50% of yield stress resulted in a corresponding increase in the corrosion current density, leading to gradual corrosion depth growth, and a decrease in the corrosion resistance of the alloy. 6082 Aluminum alloy included AlMnFeSi, Mg₂Si, and Si secondary phases. The different secondary phases presented different stress corrosion behaviors. Stress corrosion cracks were generated at the boundaries of AlMnFeSi and matrix or within the AlMnFeSi phase. Crack direction is always perpendicular to the tensile stress applied. Mg₂Si secondary phase was self-corroded as its corrosion potential is lower than that of the matrix. As the electric potential of Si is higher than that of the matrix, corrosion occurred at the matrix side of the boundary between Si and matrix.     

Diagnosis of Prostate Cancer and Prostatitis Using near Infra-Red Fluorescent AgInSe/ZnS Quantum Dots

The link between the microbiome and cancer has led researchers to search for a potential probe for intracellular targeting of bacteria and cancer. Herein, we developed near infrared-emitting ternary AgInSe/ZnS quantum dots (QDs) for dual bacterial and cancer imaging. Briefly, water-soluble AgInSe/ZnS QDs were synthesized in a commercial kitchen pressure cooker. The as-synthesized QDs exhibited a spherical shape with a particle diameter of 4.5 ± 0.5 nm, and they were brightly fluorescent with a photoluminescence maximum at 705 nm. The QDs showed low toxicity against mouse mammary carcinoma (FM3A-Luc), mouse colon carcinoma (C26), malignant fibrous histiocytoma-like (KM-Luc/GFP) and prostate cancer cells, a greater number of accumulations in Staphylococcus aureus, and good cellular uptake in prostate cancer cells. This work is an excellent step towards using ternary QDs for diagnostic and guided therapy for prostate cancer.     

Compatibilization of epoxidized triblock copolymer on the generation of self-assembled nanostructured epoxies and their surface wettability

In this work, we have successfully synthesized epoxidized poly(styrene-block-butadiene-block-styrene) with the highest epoxidation degree (55 mol%) for the first time by using metachloroperbenzoic acid method. This highly epoxidized styrene-butadiene-styrene (eSBS) block copolymer exhibited good compatibility with the epoxy (diglycidylether of bisphenol-A)/ eSBS block copolymer- 4,4′-diamino diphenyl methane blend. Transmission electron microscope images showed that the eSBS block copolymer formed spherical nanostructure morphology within the blend due to reaction induced phase separation. The addition of eSBS block copolymer in the system significantly improved the wetting parameters such as hydrophilicity, surface free energy, work of adhesion, spreading coefficient and Girifalco-Good's interaction parameter values, which are discussed in detail. The as-prepared self-assembled nanostructured epoxy system will be useful in highly toughened coating applications such as aircraft, automobile, and flooring industries.     

Aqueous synthesis of Zn-based ternary core/shell quantum dots with excellent stability and biocompatibility against different cell lines

Journal of Materials Science - Ternary quantum dots (QDs) such as zinc indium sulphide (ZIS), copper indium sulphide (CIS) and silver indium sulphide (AIS) have received great attention. Among...     

Ergodic capacity analysis of cooperative amplify‐and‐forward relay networks over generalized fading channels

This paper presents two new methods for evaluating the ergodic channel capacities of cooperative non‐regenerative multirelay networks in a myriad of fading environments and under three distinct source‐adaptive transmission policies: (i) optimal rate adaptation with a fixed transmit power; (ii) optimal joint power‐and‐rate adaptation; and (iii) truncated channel inversion with fixed rate. In contrast to the previous related works, our proposed unified analytical frameworks that are based on the moment generating function and/or the cumulative distribution function of end‐to‐end signal‐to‐noise ratio allow us to gain insights into how power assignment during different transmission phases, relay node placement, fade distributions, and dissimilar fading statistics across the distinct communication links impact the ergodic capacity, without imposing any restrictions on the channel fading parameters. Copyright © 2013 John Wiley & Sons, Ltd.     

Autonomous Unbiased Study Group Formation Algorithm for Rapid Knowledge Propagation

Knowledge propagation is a necessity, both in academics and in the industry. The focus of this work is on how to achieve rapid knowledge propagation using collaborative study groups. The practice of knowledge sharing in study groups finds relevance in conferences, workshops, and class rooms. Unfortunately, there appears to be only few researches on empirical best practices and techniques on study groups formation, especially for achieving rapid knowledge propagation. This work bridges this gap by presenting a workflow driven computational algorithm for autonomous and unbiased formation of study groups. The system workflow consists of a chronology of stages, each made of distinct steps. Two of the most important steps, subsumed within the algorithmic stage, are the algorithms that resolve the decisional problem of number of study groups to be formed, as well as the most effective permutation of the study group participants to form collaborative pairs. This work contributes a number of new algorithmic concepts, such as autonomous and unbiased matching, exhaustive multiplication technique, twisted round-robin transversal, equilibrium summation, among others. The concept of autonomous and unbiased matching is centered on the constitution of study groups and pairs purely based on the participants’ performances in an examination, rather than through any external process. As part of practical demonstration of this work, study group formation as well as unbiased pairing were fully demonstrated for a collaborative learning size of forty (40) participants, and partially for study groups of 50, 60 and 80 participants. The quantitative proof of this work was done through the technique called equilibrium summation, as well as the calculation of inter-study group Pearson Correlation Coefficients, which resulted in values higher than 0.9 in all cases. Real life experimentation was carried out while teaching Object-Oriented Programming to forty (40) undergraduates between February and May 2021. Empirical result showed that the performance of the learners was improved appreciably. This work will therefore be of immense benefit to the industry, academics and research community involved in collaborative learning.