Application of Geographical Information Systems to Lahar Hazard Assessment on an Active Volcanic System

Lahars (highly dynamic mixtures of volcanic debris and water) have been responsible for some of the most serious volcanic disasters and have killed tens of thousands of people in recent decades. Despite considerable lahar model development in the sciences, many research tools have proved wholly unsuitable for practical application on an active volcanic system where it is difficult to obtain field measurements. In addition, geographic information systems are tools that offer a great potential to explore, model and map hazards, but are currently under-utilised for lahar hazard assessment. This research pioneered a three-tiered approach to lahar hazard assessment on Montserrat, West Indies. Initially, requirements of potential users of lahar information (scientists and decision-makers) were established through interview and evaluated against attainable modelling outputs (given flow type and data availability). Subsequently, a digital elevation model, fit for modelling lahars, was used by a path of steepest descent algorithm and a semi-empirical debris-flow model in the prediction of lahar routes and inundation areas. Limitations of these established geographical information system (GIS) based models, for predicting the behaviour of (relatively under-studied) dilute lahars, were used to inform key parameters for a novel model, also tightly coupled to a GIS, that simulated flow routes based on change in velocity. Importantly, uncertainty in model predictions was assessed through a stochastic simulation of elevation error. Finally, the practical utility of modelling outputs (visualisations) was assessed through mutual feedback with local scientists. The new model adequately replicated past flow routes and gave preliminary predictions for velocities and travel times, thus providing a short-term lahar hazard assessment. Inundation areas were also mapped using the debris-flow model to assist long-term planning. Ultimately, a GIS can support ‘on the ground’ planning decisions, but efficacy is limited by an active volcanic system which can restrict feedback to and from end-users. *[The appendices for this thesis were submitted as separate files which could not be uploaded to the repository. Please contact the author for more information.]

Expanding the palette of phenanthridinium cations

5,6-Disubstituted phenanthridinium cations have a range of redox, fluorescence and biological properties. Some properties rely on phenanthridiniums intercalating into DNA, but the use of these cations as exomarkers for the reactive oxygen species (ROS), superoxide, and as inhibitors of acetylcholine esterase (AChE) do not require intercalation. A versatile modular synthesis of 5,6-disubstituted phenanthridiniums that introduces diversity by Suzuki–Miyaura coupling, imine formation and microwave-assisted cyclisation is presented. Computational modelling at the density functional theory (DFT) level reveals that the novel displacement of the aryl halide by an acyclic N-alkylimine proceeds by an SNAr mechanism rather than electrocyclisation. It is found that the displacement of halide is concerted and there is no stable Meisenheimer intermediate, provided the calculations consistently use a polarisable solvent model and a diffuse basis set

ORIGINAL RESEARCH ARTICLE - Assessment of the health risks associated with human dietary exposure to polycyclic aromatic hydrocarbons in Nile tilapia from Agboyi creek, Southwest Nigeria

Increasing levels of persistent organic pollutants in aquatic ecosystems have been a major challenge in many regions of the world due to their potential adverse effects on ecological receptors and humans via the food chain. This study assessed the risk associated with dietary exposure to polycyclic aromatic hydrocarbons (PAHs) in muscle tissues of Nile tilapia Oreochromis niloticus from Agboyi creek in Southwest-Nigeria. The concentrations of PAHs were determined using Gas Chromatography-Mass Spectrometry (GC-MS) following United State Environmental Protection Agency (USEPA) methods. Of the 16 priority PAHs screened, the mean concentration of Acenaphthene (60.51 ± 69.85 μg/kg), the most dominant of all detected PAHs accounted for 19 % of total PAHs while Benzo (a) pyrene with the lowest mean concentration of 0.08 ± 0.17 μg/kg accounted for 0.03 % of total PAHs recorded. Estimated human daily intake (EDI), Hazard Quotient (HQ) and Hazard Index (HI) of PAHs in fish through human consumption were less than the reference dose (RfD) and threshold value. However, obtained toxic equivalent concentration (TEC) for Benzo (b) fluoranthene (35.79 μg/kg) and Dibenz (a, h) anthracene (56.25 μg/kg) as well as the estimated excess cancer risk (ECR) values for 7 most toxic PAHs in fish tissues exceeded the calculated screening value of 0.0027 μg/g and the 'acceptable' range of risk (˃ 10-6) set by the United State Environmental Protection Agency (USEPA) respectively. Dietary exposure to some PAHs recorded in the tissue of Nile tilapia from Agboyi creek may have consequent health implications on the consumers

Navigating the AI Revolution in Higher Education: Strategies for Integrating Generative AI through Academia-Industry Alliances

Our presentation examines the implementation of generative AI in an undergraduate design program at a Midwestern engineering university. This initiative, a joint effort with the Industrial Advisory Board, represents a synergistic academia-industry collaboration. We will cover the initiative’s development, obstacles faced, successful outcomes, strategies to address challenges, and insights into its practical and pedagogical impact

A tool for assessing error in digital elevation models from a user’s perspective

A Digital Elevation Model (DEM) is a representation of geographic reality. The elevations recorded within DEMs have been shown to contain errors pertaining to sampling, measurement and interpolation (Fisher, 1998). Even a small amount of elevation error can greatly affect derivative products (Holmes et al., 2000). This can potentially have a significant impact on the application of DEMs in Geographical Information Systems (GIS) where first and second order derivatives are considered

Highly fluorinated naphthalenes and bifurcated C–H⋯F–C hydrogen bonding

The synthesis and crystal structures of 1,2,4,5,6,8-hexafluoronaphthalene and 1,2,4,6,8-pentafluoronaphthalene are reported. Intermolecular interactions are dominated by offset stacking and by C–H⋯F–C hydrogen bonds. For hexafluoronaphthalene, molecules are linked in layers with (4,4) network topology via R12(6) C–H⋯(F–C)2 supramolecular synthons that are rationalised by consideration of the calculated electrostatic potential of the molecule. Such an arrangement is prevented by the additional hydrogen atom in pentafluoronaphthalene and molecules instead form tapes via an R12(8) (C–H⋯F)2 synthon. The geometric characteristics of C–H⋯(F–C)2 bifurcated hydrogen bonds have been analysed for crystal structures in the Cambridge Structural Database (6416 crystal structures; 9534 C–H⋯(F–C)2 bifurcated hydrogen bonds). A geometric analysis of these hydrogen bonds has enabled the extent of asymmetry of these hydrogen bonds to be assessed and indicates a preference for symmetrically bifurcated interactions

Palladium–mediated organofluorine chemistry

Producción CientíficaThe substitution of fluorine for hydrogen in a molecule may result in profound changes in its properties and behaviour. Fluorine does not introduce special steric constraints since the F atom has a small size. However, the changes in bond polarity and the possibility of forming hydrogen bonds with other hydrogen donor fragments in the same or other molecules, may change the solubility and physical properties of the fluorinated compound when compared to the non-fluorinated one. Fluorine forms strong bonds to other elements and this ensures a good chemical stability. Altogether, fluorinated compounds are very attractive in materials chemistry and in medicinal chemistry, where many biologically active molecules and pharmaceuticals do contain fluorine in their structure and this has been shown to be essential for their activityJunta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA302U13)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA256U13