https://www.um.edu.mt/library/oar/handle/123456789/112403 Wed, 22 Apr 2026 04:50:37 GMT 2026-04-22T04:50:37Z https://www.um.edu.mt/library/oar/handle/123456789/141614 Title: Molecular logic gates as fluorescent markers and DNA binding agents Abstract: N/A Description: Ph.D.(Melit.) Sun, 01 Jan 2023 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/141614 2023-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/137599 Title: An investigation of smart, inclusion-based mechanical metamaterials Abstract: Mechanical metamaterials have captured the attention of researchers worldwide owing to their exceptional mechanical properties. They are poised to emerge as a pivotal category of materials that will shape the next generation of innovative materials. Research on auxetic materials, a class of mechanical metamaterials, has been ongoing for more than four decades, with recent years witnessing a surge in interest in the design of 3D auxetic metamaterials. Another class of metamaterials that has shown great potential is active metamaterials, which are materials that can have their geometry and/or mechanical properties tuned post-fabrication in response to external stimuli. This thesis delved into the realm of mechanical metamaterials, focusing on these two distinct categories. It introduced a novel design approach for creating 3D auxetic structures and conducted an in-depth exploration of magneto-mechanical active metamaterials. The 3D auxetic systems were intentionally designed to lay the foundation for potential future research, envisioning their transformation into active magneto-mechanical metamaterials. The mechanical properties of the 3D auxetic structures produced in this thesis were investigated through numerical simulations validated by experimental tests. It was demonstrated that a system, created through equally sized voids with a constant cross-sectional area into a solid material at specific locations in various planes, could exhibit a negative Poisson's ratio of approximately -0.5 in multiple directions. This behaviour was observed over a significant range of aperture angles for the cross-sectional areas, especially when the voids were positioned close to each other. A scalable inclusion-based active magneto-mechanical metamaterial consisting of magnetic inclusions embedded within a non-magnetic matrix was also produced. The proposed structure, based on an accordion-like structure, was shown to respond to the magnitude and direction of an external magnetic field by tuning its geometry. The basic unit was then used to create a number of active systems including the auxetic re-entrant honeycomb and egg-rack structures. Finally, iron nanoparticles inclusions were used instead of permanent magnets and successfully produced a magneto elastomer. Through numerical simulations validated by experimental prototypes, the response to an external magnetic field was investigated. The numerical model showed good agreement with the experimental tests and following this the effect of nanoparticle concentration and other geometric parameters were investigated. Description: Ph.D.(Melit.) Sun, 01 Jan 2023 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/137599 2023-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/135048 Title: Rationalising marine space : a multidisciplinary analysis for ecosystem-based marine spatial planning Abstract: This work and its abstract are both under embargo until the restriction is lifted. Description: Ph.D.(Melit.) Sun, 01 Jan 2023 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/135048 2023-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/131234 Title: The night sky brightness of Malta Abstract: Light pollution is the harmful increase in lighting at night as a result of ill-directed and uncontrolled artificial light. In the Maltese Islands, the amount of artificial light at night has significantly increased in the last few years, largely due to unregulated light emissions. The motivation to continue monitoring and quantifying the geographical pattern of the light pollution problem in Malta stems from its adverse effects on numerous fields, including astronomical observation, ecology and human health. In this study, Malta was mapped onto a 1 km2 grid and its light pollution levels were investigated by measuring the night sky brightness in each square using a Unihedron Sky Quality Meter (SQM). It was found that a previously used SQM exhibited a drift due to ageing, so all its measurements were reassessed using a brand new SQM. Analysis on this drift was carried out which showed an apparent trend towards darker skies. With the help of coloured grids and interpolation maps, the general distribution of light pollution in Malta was analysed. The north and west parts of Malta remain dark while the central, east and south areas are severely polluted. Overall, Sliema, Valletta, Marsa, and Birzebbuga, were found to be the most light polluted regions in Malta. Furthermore, the collected data was directly compared to a similar study done in 2017/18 to investigate the change in light pollution levels. Approximately 42% of the areas were found to be brighter in this research, despite the 2017/18 study not adopting an anti-glare hood to block out neighbouring lights. This study brings to the fore the extent of light pollution in Malta, and the importance to regulate its light emissions. Future studies are encouraged to adopt this methodology once again to further identify any new hotspots and problematic areas in Malta and to preserve the few remaining dark skies in our islands. Description: B.Sc. (Hons)(Melit.) Sun, 01 Jan 2023 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/131234 2023-01-01T00:00:00Z