Abstract: Wall paintings make up an important section of cultural heritage. They resemble time portals that can be used to travel back into the past and witness the life of our ancestors. In these paintings, the ancient artists depicted the different aspects of their life, such as cooking, baking, farming, manufacturing, as well as thoughts and beliefs. Unfortunately, wall paintings are susceptible to degradation over time in the form of the accumulations of dirt and deposits on the painted surfaces and loss of adhesion of the paint layers at the surface. Therefore, the removal of these deposits is one of the primary duties of conservator-restorers. Such operations are intended to restore the painted surface to a condition close enough to its original state. Since cleaning artworks may cause undesirable physicochemical alterations and is nonreversible, the proper cleaning procedure should be adopted. In this regard, numerous gels have been developed and exploited for the cleaning of various artwork surfaces. Lately, polyvinyl alcohol-borax (PVA-B) and agarose (AG) hydrogels have been widely employed as cleaning materials by conservator-restorers. However, both hydrogels have shown limitations in specific cleaning practices. In this work, we investigated a new double network hydrogel based on blending PVA-B and agarose to avoid the limitations posed by the constituting hydrogels. For this reason, a detailed characterization of the PVA–B/AG double network hydrogel was performed, including chemical structure, liquid phase retention, mechanical strength, rheological behavior, and self-healing behavior of various PVA-B/AG hydrogels. These new hydrogels revealed better properties than PVA-B and agarose hydrogels and obviated their limitations. A laboratory experiment on the removal of deteriorated Paraloid® B72 proved that the PVA-B/AG hydrogel loaded 10%/10% MEK/1-PeOH was able to remove these layers efficiently. Therefore, the hydrogel was tested on a wall painting from the Temple of Seti I in Abydos – Egypt. It removed the glossy/darkened consolidant from the wall painting and restored the original matt appearance of the painted surface. In another application on the painted ceiling of the same temple, the hydrogel was tested for removing thick soot layers. The hydrogel formulation (loaded with 5% ammonia, 0.3% ammonium carbonate, and 0.3% EDTA) removed these layers with no noticeable damage to the paint layers. In a wide-scale application of the hydrogel (loaded with 10% propylene carbonate), it removed a highly deteriorated varnish layer from a 19-c wall painting. All the traditional cleaning methods employed caused damage to the paint layers, proving that gel cleaning can be a safer cleaning alternative in some cases.

Abstract: In a world increasingly reliant on alternative energy sources, the quest for efficient and secure storage solutions is paramount. This doctoral thesis explores the exciting potential of a familiar material – water – to act as a vault for next-generation energy sources like hydrogen (H2) and methane (CH4). Nature offers a solution in the form of clathrate hydrates, fascinating cage-like structures formed from water molecules that can trap these gas molecules within their framework. This research investigates on improving the formation kinetics and gas storage capabilities of clathrate hydrates utilizing porous materials and the interstitial space between non-porous materials to augment the contact between gas and water thereby catalysing the growth of hydrates and unlocking their full potential as efficient and secure energy storage reservoirs. A key outcome of this research is the formulation of an empirical correlation, offering predictive insights into CH4 hydrate phase equilibrium conditions. Innovative approaches utilizing thermally conductive beads have yielded substantial enhancements in CH4 uptake. Furthermore, the identification of optimal water content within porous materials showcases a pathway to maximize CH4 storage capacity and hydrate growth kinetics. In the domain of hydrogen storage, attention is also directed towards unstirred systems, where the integration of functionalized porous materials has demonstrated a significant improvement in the rate of hydrate formation and the overall H2 storage capacity. A noteworthy achievement of this research lies in the successful storage of H2 within confined CH4 hydrates through a gas exchange process and the preliminary results show the potential for safer and more sustainable method for H2 storage at mild thermodynamic conditions, offering promising prospects for future energy systems.

Abstract: MicroRNAs (miRNAs) are small oligonucleotides (18-25 bases) that play a key role in epigenetic regulation. Since the discovery of miRNAs in 1993, their role in biological processes has been extensively investigated. By now, it has been evidenced that monitoring and detection of miRNAs can improve (early) disease diagnosis. The existing diagnostic approaches have limitations such as the need for complex multistep protocols for sample preparation, analysis, data interpretation, high cost of equipment, the need for highly qualified personnel, and high laboratory standards. As opposed to this, point-of-care biosensors and chips aim to facilitate the procedure and avoid sending samples into centralized laboratories, which saves time, reduces the chance of sample degradation, and enables analysis of patient samples in remote areas, directly at home or primary and secondary care facilities (i.e. general practitioners and specialists). The latter is essential for therapy assessment and follow-up monitoring of patients with chronic diseases and cancer. Nevertheless, the development of such sensors is lagging compared to the projections of 10 – 20 years ago, mainly due to insufficient sensitivity, poor reproducibility, and the complexity of the sensors’ design reported in the research literature. This motivates the development of new detection strategies and technologies such as photoelectrochemical sensors that combine the best features of different sensing approaches. The primary concern when developing detection technologies for miRNA is the need for a highly sensitive and selective platform. This thesis explores a novel photoelectrochemical (PEC) method that is distinctive owing to its sensitive nature and simple and robust design. Firstly, we focused on the usage of recently emerging commercial gold-sputtered electrode systems for the detection of short nucleic acid with enzymatic amplification. Importantly, cleaning such electrodes is a challenge since the standard procedures known for regular disk electrodes such as polishing cannot be employed here, since it will damage the protective layer on the electrode. However, the electrodes can be washed and pretreated chemically and/or electrochemically. Thus, a procedure to effectively clean and modify the gold-sputtered electrode has been developed, resulting in high-performance gold-sputtered nucleic acid sensors. Next, the usage of molecular photosensitizers as an alternative to enzymatic amplification has been evaluated. We took advantage of the singlet oxygen production by photosensitizers upon photoexcitation, leading to a photocurrent response due to the singlet oxygen-induced (electro)chemical conversions. Following the demonstration of the detection strategy, the analytical performance of the sensing system was evaluated using magnetic beads-based nucleic acid assay on disposable electrode platforms, with a focus to enhance the sensitivity and robustness of the technique in detecting complementary nucleic acid targets. Following the fundamental evaluation of the singlet oxygen-based PEC detection of nucleic acids, we further optimized the assay and measurement parameters and employed the sensing strategy for a polymerase chain reaction-free (PCR-free) quantification of miRNAs related to prostate cancer. By successfully detecting and quantifying low-picomolar range concentrations (< 10 pM) in plasma samples from prostate cancer patients, we successfully showed the applicability of the novel sensing strategy. We have also compared and positioned the performance of our developed PEC strategy with an existing state-of-art technique, i.e. electrochemiluminescence (ECL). Our PEC strategy performed on par with ECL, both yielding low-picomolar detection limits in serum matrices, however quicker and cheaper than ECL. Owing to the versatility of this PEC technique, the final study explored its multiplexing capability. As a starting point in this branch of the research, we have investigated two possible ways for multiplexing. To perform multiple measurements at the same time, constructing calibration plots and quantifying unknown miRNA concentrations in patient samples at the same time, we have developed a high-throughput detection with 96X multi-channel electrode systems and in-house designed and constructed 96XLED illumination sources. Secondly, to detect more than one target miRNA in a single measurement, intra-vial multiplexing where the samples were analyzed for different targets in one vial was also explored. Altogether, this thesis presents the fundamentals, development and application of a novel PEC strategy for detecting short (< 25 bases) nucleic acid sequences, in particular, miRNA. With an aim to serve as a distinctive technique to function as a clinical testing platform without any need for PCR, this work adds value to the development of nucleic acid-based sensors for miRNAs and other short-stranded nucleic acid biomarkers, and benefits in the early detection of diseases like cancer.

Abstract: As natural gas prices proved to be very volatile, sustainable alternatives are highly needed. Water-derived H2 was revealed as a promising substitute, allowing to produce a green energy carrier with a minimum of harmful emissions. Direct splitting of earth-abundant seawater provides an eco-friendly route for the production of clean H2, but is hampered by selectivity and stability issues due to the presence of salts.Photocatalytic seawater splitting is particularly promising for this purpose, as it seems less affected by adversary seawater effects and might rely on free and renewable solar power. Unfortunately, the benchmark photocatalyst, TiO2, still suffers from its low solar light activity. It is only actived upon illumination with energetic ultraviolet light (<5% of the sunlight). In order to broaden the activity window to the visible light, the concept of the 'plasmonic rainbow' was explored. Here, TiO2 is modified with various gold-silver composites that possess the unique optical phenomenon of Surface Plasmon Resonance (SPR). This phenomenon enables the absorption of light at very specific wavelengths, depending on the metal type, size, shape and dielectric environment. The light energy might then be converted into hot carriers, strong local electromagnetic fields and/or heat. By combining multiple composites with various sizes and compositions, a broadband absorption could be obtained, resulting in significantly enhanced activity in photocatalytic model reactions under simulated sunlight. The major disadvantage of these plasmonic nanoparticles is their tendency to oxidize and deactivate. To overcome this, polymer shell stabilization strategies were found to be effective to protect the metal cores. Both conductive and non-conductive polymers were studied. For the former, a mix-and-wait strategy generating polyaniline shells of 2-5 nm was used, whille the latter was based on a Layer-by-Layer approach, allowing (sub) nanometer thickness control. For the actual H2 production experiments, the plasmonic loading was optimized in a pure water:methanol scavenger (7:1) mixture and initially the stabilization strategies proofed to be effective for simulated seawater (0.5M NaCl), even after 2 years. However, in real seawater, the activity decreased drastically due to aggregation of the photocatalyst in the presence of multivalent cations. Finally, facile immobilization strategies using 3D printing showed to be able to yield stable, solar active photocatalyst for real seawater splitting.

Abstract: As decentralized electricity generation plays an important role in the reform of the energy system in the EU, electric residential microgrids merit an assessment of their position and potential. The work on this dissertation focuses on the synergy between the development of microgrids that are powered by PV panels, and the adoption of energy storage, with the aim to identify shortcomings and propose solutions. Techno-economic assessment indicates that, for a microgrid that aims to maximize its self-consumption, the electricity pricing mechanisms that are current practice across the EU are detrimental to the economic viability of using energy storage. Case studies and simulations in Belgium, Greece, Denmark, Italy, Finland, Spain and Germany show conclusively how existing tariff structures (Net-Metering, Time-of-Use, Feed-in Tariff, with or without the option of a Capacity tariff) are suitable for stimulating renewable generation, but not storage. Another underlying reason that affects the economic viability of a residential microgrid in the current context relates to the technology losses, which cannot be compensated by electricity pricing mechanisms. Having established the need for a different approach in order to improve the economic viability of microgrids with storage, this work investigated whether a form of direct support to the microgrid operator can be envisioned. A cost-benefit analysis revealed that the benefits coming from decentralized energy generation toward the main electricity grid can be compared with the cost of including and operating energy storage, and therefore a direct support from the network operator and the public can be justified in order to attain the economic viability of a microgrid with storage. This way, the electricity network can benefit from an increased number of flexible, enriched microgrids within the system, the microgrid operators are incentivized to include energy storage, and the society contributes towards a sturdier energy supply with more engaged prosumers and less polluting emissions. Entrepreneurial diversity: a career motives’ perspective – Ilse D

Abstract: Globally, incorporation of agricultural lands into the urban boundary has been a common phenomenon. Governments use various alternatives to access the required land, including land expropriation procedures, which refers to the compulsorily taking of land from the landholders without their consent by paying compensation. In Ethiopia, the urban population is growing rapidly which resulted into an increase in the demand for urban land for housing construction, public services provision, and infrastructure developments. As the Ethiopian constitution prohibits sale of landholders, governments, at various levels, have been expropriating land from the surrounding farmers to meet the demand for urban land. The general objective of this thesis is to improve the understanding of the impacts of local land deals for urbanization on socioeconomics of farmers and the environment. The findings of this thesis revealed that there are gaps in the current practices of land expropriation for urban expansion that should be improved. The results showed that the compensation paid to the affected farmers is found to be economically inappropriate, i.e., not enough to restore the affected farmers’ livelihoods, in contrast with the land laws that allows a compensation amount that would put previous land users in a better or the same wellbeing as before the land expropriation. In addition, it is indicated that the land expropriation process does not take into account the value of ecosystem services, which are benefits obtain from the land, and important for the wellbeing of the society. We conclude that while land expropriation is an important tool to obtain land from the landholders when it is needed for public purposes, the practices in the study area show it is adversely affecting the socioeconomics of farmers and the environment.