Association between traumatic dental injuries (TDIs) and caries experience in a selected northern Nigerian population

Objective: To determine the association between traumatic dental injuries (TDIs) and caries experience in a selected Nigerian population and the influence(s) of gender and location on this association.Method: The sample size included 799 school children proportionately selected through multistage sampling technique. Caries experience (DMFT) and TDIs to the teeth were evaluated clinically by one examiner (intra-examiner reliability was 0.852 by Cronbach’s Alpha test). The TDIs were classified according to the modified Ellis classification. Diagnosis of caries was at cavitation level. Analysis was by the use of SPSS v17.0.Result: There were 450 (56.3%) males and 43.7% females. Subjects were aged 12 to 21 years (Mean 12.25 ± 0.93). About half (51.8%) were from the urban areas. Prevalence of TDIs and caries was 14.6% and 12.4% respectively. TDIs were more prevalent among males (P = 0.015, OR = 1.7, 95% CI = 1.103, 2.519), with enamel fracture (74.5%) being the commonest (74.5%) TDI seen. Dental caries was commoner in the rural areas (DMFT [ ] = 0.249, B = 0.029, 95% CI = -0.180, -0.009). There was no significant association between caries experience and TDIs ( = 0.197, p = 0.944, 95% CI = -0.125, 0.117) and neither by gender nor location (P>0.05). The odds of having TDIs in those with dental caries was 1.04, 95% CI = 0.581, 1.885.Conclusion: There was no association between TDIs and caries experience in the studied Nigerian population. Caries experience was more in the rural areas and being male was associated with a higher probability of having a traumatized tooth. Key words: Dental caries, traumatic dental injuries, children

Patients’ self reported satisfaction of dental treatments received

No Abstrac

3D and 4D Characterisation of Lithium-Ion Battery Electrode Microstructures using X-ray Tomography

There is a direct link between electrode microstructure and their performance in lithium-ion batteries (LIBs); however, this relationship remains poorly understood. By utilising tomographic X-ray imaging techniques, it is possible to characterise LIB electrode microstructure in three dimensions. Moreover, extending these imaging techniques to explore changes in these materials gives rise to the notion of “four-dimensional” (4D) tomography to study microstructural evolution with time. This work focused on characterising, both qualitatively and quantitatively, the three-dimensional (3D) microstructure of LIB electrode materials at multiple length and time scales with the aid of laboratory and synchrotron X-ray sources. The suitability and reliability of direct 3D microstructural analysis for quantifying LIB electrodes was demonstrated by comparing it with stereological methods, which are shown to introduce bias when applied to inhomogeneous 3D microstructures. Silicon (Si) and metallic lithium (Li) are highly energy-dense electrode materials and promising candidates for use in LIBs; however, they experience significant microstructural degradation upon electrochemical cycling. Using a custom-built, X-ray transparent in-situ electrochemical cell, 4D characterisation of the microstructural evolution and degradation within the aforementioned electrode materials was performed both in-situ and in-operando. Phase transformation, fracture formation and propagation within individual Si particles was visualized and tracked in 3D during the course of a half-cell discharge. At a higher X-ray imaging resolution, microstructural evolution in Si microparticles as a result of repeated cycling was captured and quantified in 3D. Visualisation of formation and growth of pits and mossy lithium deposits along metallic Li electrode surfaces was also presented. Finally, an X-ray contrast-enhancement approach for imaging lowly attenuating electrode materials such as graphite was also demonstrated. This work has demonstrated X-ray tomography as a diagnostic tool for providing valuable insight into electrode microstructure which can aid the efficient design of these electrode materials in future generation LIB systems

The role of DNA methylation in stem cell ageing

Ageing is a major factor contributing to human morbidity and disease, including cancer. To study the possible involvement of epigenetic changes in ageing, murine haematopoiesis was used as a model system. The key cells determining ageing in this system are thought to be lower side population (LSP) cells of the bone marrow, which are enriched for long-term reconstituting haematopoietic stem cells (LT-HSCs). In this thesis, rare primary LT-HSCs from young, middle-aged and old mice were isolated and phenotyped. A protocol, termed Nano-MeDIP-seq was developed for methylome analyses on such rare cells. DNA and RNA from these cells were then subjected to comprehensive methylome (MeDIP-seq) and transcriptome (RNA-seq) analysis. Age-related changes in the LT-HSC methylome and transcriptome were observed in this study, many at genes associated with migration/adhesion and not previously implicated in ageing. These changes also include directional (young to old) global loss of DNA methylation of approximately 5%, 111 significantly (FDR < 0.2) age differentially methylated regions (aDMR) and more than one thousand significantly (FDR < 0.05) differentially expressed transcripts. Ingenuity pathway analysis (IPA) identified significant (p << 0.0001) age-related decline in B-Cell development and significant (p << 0.0001) alterations in pathways and functions associated with cell movement. A number of genes were identified to be significantly age differentially methylated and differentially expressed. One aDMR, associated with the Serum deprivation protein response (Sdpr) gene, was functionally validated to demonstrate a negative correlation between promoter methylation and differential expression. The findings in this thesis support a model involving an epigenetic dysregulation of the genes that control the interaction between LT-HSCs and their regulatory niche, during physiological ageing

Removal of Pb and Zn from Soil using cowpea (Vigna unguiculata) and maize (Zea mays) Plants

This study investigated the potential of cowpea (Vigna unguiculata) and maize (Zea mays) plants to remove Pb and Zn from soil. The crops were exposed to three concentrations (100, 150 and 200 mgkg-1) of each metal salts during the study. When the plants were treated with lead nitrate at a concentration of 150 mgkg-1, the amount and percentage of Pb removed and accumulated within plants’ tissues were 65.68 m mgkg-1g/kg (44.79%) and 78.93 mgkg-1 (53.0%) for cowpea and maize with bioconcentration factors 0.80 and 0.78 respectively. However, when the plants were assisted they had greater bioconcentration factors. Farmyard manure enhanced metal uptake by cowpea and maize significantly than EDTA. Maize extracted more Pb into its roots and translocated to shoots when assisted with EDTA than cowpea. Maize was able to translocate more Pb while cowpea translocated more Zn through the vascular system, thereby acting as phytoextractors for the different metals respectively

Heavy metal bioaccumulation and biomarkers of oxidative stress in the wild African tiger frog, Hoplobatrachus occipitalis

Human activities can have dramatic effects on animal populations around urban areas with heavy metal contamination being a primary cause of harm. Amphibians, as residents of aquatic systems and with their semi-permeable skin are especially susceptible to heavy metal contamination. To better understand the effect of heavy metals on Wild African Tiger frogs (Hoplobatrachus occipitalis) and the resulting production of oxidative stress enzymes, the concentrations of the heavy metals, cadmium (Cd), copper (Cu), iron (Fe), zinc (Zn), lead (Pb) and nickel (Ni) were investigated in the tissues of H. occipitalis as well as in water and sediment samples collected from five different locations in Lagos State, Nigeria. The activities of superoxide dismutase (SOD), reduced glutathione (GSH) and level of lipid peroxidation product, malondialdehyde (MDA) were analyzed in the liver of the sampled frogs. Most measured physicochemical characteristics of the water varied significantly across the sampling locations (P&lt;0.05). The levels of metals (mg/kg dry weight) in muscle tissues also varied significantly across the locations (P&lt;0.05) and ranged as follows: Cd: 0.21-5.03, Cu: 0.74-13.40, Fe: 3.19-109.10, Zn: 3.70-120.20, Pb: 0.12-18.24 and Ni: 3.20-7.28. Zn was the most accumulated metal, followed by Fe, Cu and Ni, while Pb was the least. The mean of SOD and reduced GSH in the frogs indicate some responses to oxidative stress which varied significantly among sampling areas (P&lt;0.05). MDA values however did not consistently correlate with either oxidative stress or heavy metal concentrations in the frogs. The water-sediment-tissue analysis for heavy metals demonstrated that the sediment concentrated more heavy metals than water, while the frog tissues accumulated these metals articularly in more polluted areas.Key words: Heavy metal pollution, bioaccumulation, Hoplobatrachus occipitalis, biomarkers, oxidative stress

The use of contrast enhancement techniques in X-ray imaging of lithium-ion battery electrodes

Understanding the microstructural morphology of Li-ion battery electrodes is crucial to improving the electrochemical performance of current Li-ion battery systems and in developing next-generation power systems. The use of 3D X-ray imaging techniques, which are continuously evolving, provides a non-invasive platform to study the relationship between electrode microstructure and performance at various time and length scales. In addition to characterizing a weakly (X-ray) absorbing graphite electrode at multiple length scales, we implement an approach for obtaining improved nano-scale image contrast on a laboratory X-ray microscope by combining information obtained from both absorption-contrast and Zernike phase-contrast X-ray images

Identification of compounds with cytotoxic activity from the leaf of the Nigerian medicinal plant, Anacardium occidentale L. (Anacardiaceae)

Cancer is now the second-leading cause of mortality and morbidity, behind only heart disease, necessitating urgent development of (chemo)therapeutic interventions to stem the growing burden of cancer cases and cancer death. Plants represent a credible source of promising drug leads in this regard, with a long history of proven use in the indigenous treatment of cancer. This study therefore investigated Anacardium occidentale, one of the plants in a Nigerian Traditional Medicine formulation commonly used to manage cancerous diseases, for cytotoxic activity. Bioassay-guided fractionation, spectroscopy, Alamar blue fluorescence-based viability assay in cultured HeLa cells and microscopy were used. Four compounds, zoapatanolide A (1), agathisflavone (2), 1,2-bis(2,6-dimethoxy-4-methoxycarbonylphenyl)ethane (anacardicin, 3) and methyl gallate (4), were isolated, with the most potent being zoapatanolide A with an IC50 value of 36.2 ± 9.8 µM in the viability assay. To gain an insight into the likely molecular basis of their observed cytotoxic effects, Autodock Vina binding free energies of each of the isolated compounds with seven molecular targets implicated in cancer development (MAPK8, MAPK10, MAP3K12, MAPK3, MAPK1, MAPK7 and VEGF), were calculated. Pearson correlation coefficients were obtained with experimentally-determined IC50 in the Alamar blue viability assay. While these compounds were not as potent as a standard anticancer compound, doxorubicin, the results provide reasonable evidence that the plant species contains compounds with cytotoxic activity. This study provides some evidence of why this plant is used ethnobotanically in anticancer herbal formulations and justifies investigating Nigerian medicinal plants highlighted in recent ethnobotanical surveys

4D analysis of the microstructural evolution of Si-based electrodes during lithiation: Time-lapse X-ray imaging and digital volume correlation

Silicon is a promising candidate to substitute or complement graphite as anode material in Li-ion batteries due, mainly, to its high energy density. However, the lithiation/delithiation processes of silicon particles are inherently related to drastic volume changes which, within a battery's physically constrained case, can induce significant deformation of the fundamental components of the battery that can eventually cause it to fail. In this work, we use non-destructive time-lapse X-ray imaging techniques to study the coupled electrochemo-mechanical phenomena in Li-ion batteries. We present X-ray computed tomography data acquired at different times during the first lithiation of custom-built silicon-lithium battery cells. Microstructural volume changes have been quantified using full 3D strain field measurements from digital volume correlation analysis. Furthermore, the extent of lithiation of silicon particles has been quantified in 3D from the grey-scale of the tomography images. Correlation of the volume expansion and grey-scale changes over the silicon-based electrode volume indicates that the process of lithiation is kinetically affected by the reaction at the Si/LixSi interface

Study of the tortuosity factors at multi-scale for a novel-structured SOFC anode

© Published under licence by IOP Publishing Ltd. Gas transport properties are closely related to the tortuosity of the pore network within porous materials. For the first time, this study explores a multi-scale imaging and modelling method to measure the tortuosity of an Solid Oxide Fuel Cell (SOFC) electrode material with pore sizes spanning over hundreds of orders of magnitude. This analysis is normally challenging using image-based techniques, as pores of different sizes may not be easily resolved at the same time using X-ray computed tomography (CT). In this study, a tubular SOFC anode, fabricated by a phase inversion technique, is used to illustrate this approach. A heat flux analogy is used to simulate mass transport and the results show that the embedded large-scale finger-like pores can significantly improve mass transport by providing less tortuous pathways