Combined Semi-absolute FNAA and EDXRF in coal analysis

A combination of Semi-absolute Fast Neutron Activation Analysis (SFNAA) and Energy Dispersive X-ray Fluorescence (EDXRF) analysis has been employed to determine 35 inorganic elements in coals from four different mines across the minefields of Nigeria. A plot of certified against measured values of elemental constituents in a National Bureau of Standard coal reference material, SRM 1632 a, with a regression coefficient of r=0.894, is used to demonstrate the efficacy of this technique. With a complimentary application of the EDXRF technique, better precision is obtained for short-lived isotopes reducing the need for a more sophisticated transfer system and cyclic activation analysis in the situation under discussion.     

Effect of Cu content on structure,hydrogen storage properties and electrode performance of LaNi4.1-x Co0.6Mn0.3Cu x alloys

The effect of Cu content on structure, hydrogen storage, and electrochemical properties of LaNi_4.1-x Co_0.6Mn_0.3Cu _x alloys has been investigated. For sample, A, B, C, and D are used to represent alloys (x?=?0, 0.15, 0.3, and 0.45), respectively. The results indicate that the four alloys are all single-phase alloy with LaNi₅ phase of CaCu₅ hexagonal structure, the hydrogen storage capacities of the alloy are about 1.49 wt% (A), 1.48 wt% (B), 1.43 wt% (C), and 1.25 wt% (D) at 303 K. With the increase of Cu content (x) from A to D, hydrogen desorption plateau pressure and pressure hysteresis decrease. Alloy electrode A shows better activation property and higher capacity (334.44 mAh/g). The addition of Cu improves the cyclic stability of the alloy electrodes when x?=?0?~?0.45. However, their self-discharge properties and high-rate dischargeability (HRD) decrease with the increase of x. Further, electrochemical kinetics and electrochemical impedance spectroscopy (EIS) analysis show that the reaction of alloy electrode is controlled by charge transfer step, and the adding of Cu benefits the electrode properties in alkaline solution.     

Kinetic study of the thermoluminescence glow curve of natural dolerite

T _m–T _stop and glow curve deconvolution methods have been used to determine the number of glow peaks and kinetic parameters (activation energy E and frequency factor s) associated with the glow peaks in a natural dolerite. The T _m–T _stop method indicated that the glow curve of the mineral is the superposition of at least seven first-order components, whereas deconvolution analysis indicated the presence of at least eight peaks. A possible reason for this discrepancy is given. The kinetic parameters of the eight peaks are presented and used to estimate the lifetimes of the glow peaks. The lifetimes of the peaks at 120.8 and 143 °C are few days. For application in dosimetry and dating, we suggest the use of a preheat temperature around 170 °C to ensure the complete removal of these peaks with small lifetimes.     

An Adaptive Rank Aggregation-Based Ensemble Multi-Filter Feature Selection Method in Software Defect Prediction

Feature selection is known to be an applicable solution to address the problem of high dimensionality in software defect prediction (SDP). However, choosing an appropriate filter feature selection (FFS) method that will generate and guarantee optimal features in SDP is an open research issue, known as the filter rank selection problem. As a solution, the combination of multiple filter methods can alleviate the filter rank selection problem. In this study, a novel adaptive rank aggregation-based ensemble multi-filter feature selection (AREMFFS) method is proposed to resolve high dimensionality and filter rank selection problems in SDP. Specifically, the proposed AREMFFS method is based on assessing and combining the strengths of individual FFS methods by aggregating multiple rank lists in the generation and subsequent selection of top-ranked features to be used in the SDP process. The efficacy of the proposed AREMFFS method is evaluated with decision tree (DT) and naïve Bayes (NB) models on defect datasets from different repositories with diverse defect granularities. Findings from the experimental results indicated the superiority of AREMFFS over other baseline FFS methods that were evaluated, existing rank aggregation based multi-filter FS methods, and variants of AREMFFS as developed in this study. That is, the proposed AREMFFS method not only had a superior effect on prediction performances of SDP models but also outperformed baseline FS methods and existing rank aggregation based multi-filter FS methods. Therefore, this study recommends the combination of multiple FFS methods to utilize the strength of respective FFS methods and take advantage of filter–filter relationships in selecting optimal features for SDP processes.     

Phenolics Profiling of Carpobrotus edulis (L.) N.E.Br. and Insights into Molecular Dynamics of Their Significance in Type 2 Diabetes Therapy and Its Retinopathy Complication

Adverse effects associated with synthetic drugs in diabetes therapy has prompted the search for novel natural lead compounds with little or no side effects. Effects of phenolic compounds from Carpobrotus edulis on carbohydrate-metabolizing enzymes through in vitro and in silico methods were assessed. Based on the half-maximal inhibitory concentrations (IC₅₀), the phenolic extract of the plant had significant (p < 0.05) in vitro inhibitory effect on the specific activity of alpha-amylase (0.51 mg/mL), alpha-glucosidase (0.062 mg/mL) and aldose reductase (0.75 mg/mL), compared with the reference standards (0.55, 0.72 and 7.05 mg/mL, respectively). Molecular interactions established between the 11 phenolic compounds identifiable from the HPLC chromatogram of the extract and active site residues of the enzymes revealed higher binding affinity and more structural compactness with procyanidin (−69.834 ± 6.574 kcal/mol) and 1,3-dicaffeoxyl quinic acid (−42.630 ± 4.076 kcal/mol) as potential inhibitors of alpha-amylase and alpha-glucosidase, respectively, while isorhamnetin-3-O-rutinoside (−45.398 ± 4.568 kcal/mol) and luteolin-7-O-beta-d-glucoside (−45.102 ± 4.024 kcal/mol) for aldose reductase relative to respective reference standards. Put together, the findings are suggestive of the compounds as potential constituents of C. edulis phenolic extract responsible for the significant hypoglycemic effect in vitro; hence, they could be exploited in the development of novel therapeutic agents for type-2 diabetes and its retinopathy complication.     

Low dose TL characteristics of Nigerian fluorite

Nigerian fluorite has been characterized by β-irradiation for thermoluminescence in the low dose range (40 μGy–72 mGy). The glow curves exhibit 3 peaks recorded at 111 ± 11 °C, 196 ± 2 °C and 282 ± 4 °C at the heating rate of 5 °C s^?1. The two high temperature peaks exhibit a linear response over the range of study. The minimum detectable dose for each of the observed peaks has been determined and the lowest detection limit of fluorite was also determined. A complex fading pattern was observed for the phosphor and the possible source of the TL buildup has been discussed.     

Study of the Nutritional Status of Maternal Breast Milk in Preterm Infants in Nigeria

Instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE) analysis were used to determine the concentration of 13 elements in the breast milk collected within the first week of lactation and after morning feed from 16 pre-term mothers and 20 term mothers. The results of the study show that pre-term milk has a significantly higher concentration of Cl, Cu, Fe, K, Mg, Mn, Na and Zn while term mothers have a significantly higher concentration of P and Br. No significant differences were, however, found in the mean concentration of Al, Ca, I and Rb. Furthermore, the mean concentration for most of the elements found in the breast milk fall within the range of the concentrations obtained for the commercial infant milk formulae.     

Co3O4@Cu-Based Conductive Metal–Organic Framework Core–Shell Nanowire Electrocatalysts Enable Efficient Low-Overall-Potential Water Splitting

In the work reported herein, the electrocatalytic properties of Co₃O₄ in hydrogen and oxygen evolution reactions have been significantly enhanced by coating a shell layer of a copper-based metal–organic framework on Co₃O₄ porous nanowire arrays and using the products as high-performance bifunctional electrocatalysts for overall water splitting. The coating of the copper-based metal–organic framework resulted in the hybridization of the copper-embedded protective carbon shell layer with Co₃O₄ to create a strong Cu−O−Co bonding interaction for efficient hydrogen adsorption. The hybridization also led to electronically induced oxygen defects and nitrogen doping to effectively enhance the electrical conductivity of Co₃O₄. The optimal as-prepared core–shell hybrid material displayed excellent overall-water-splitting catalytic activity that required overall voltages of 1.45 and 1.57 V to reach onset and a current density of 10 mA cm⁻², respectively. This is the first report to highlight the relevance of hybridizing MOF-based co-catalysts to boost the electrocatalytic performance of nonprecious transition-metal oxides.     

Neutron spectrum parameters in irradiation channels of the Nigeria Research Reactor-1 (NIRR-1) for the <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-NAA standardization

Summary The first nuclear research reactor in Nigeria has been commissioned for neutron activation analysis and limited radioisotope production. In order to extend its utilization to include the k₀-standardization method, the following neutron spectrum parameters in inner and outer irradiation channels were determined by the “Cd-ratio for multi-monitor method”: the thermal-to-epithermal flux ratio, f, and the epithermal flux shape factor, α. Neutron spectrum parameters determined in the inner irradiation channel B2, are: α = -0.052±0.002 and f = 19.2±0.5. For the outer irradiation channel B4, the neutron spectrum parameters were found to be α = +0.029±0.003 and f = 48.3±3.3. The results are compared with the neutron spectrum parameters of other reactor facilities with similar core configuration such as the Slowpoke and Miniature Neutron Source Reactor facilities available in the literature.