Abstract: Photocatalysis has been labeled for decades as a promising technique for air purification. The principle seems straightforward and requires a photocatalyst that is immobilized on a substrate, and one or more UV sources to activate the photocatalyst. No waste products are produced, the reactions occur in mild conditions and the supplies are relatively cheap. Yet it seems that the commercialization of photocatalytic systems does not break through on the global market. The aim of this thesis is to identify and tackle the bottlenecks that impede commercialization from an application-oriented approach. The problem of indoor air pollution is enhanced by the fact that people spend more and more time indoors and that ventilation is kept to a minimum as an energy-saving measure. This inevitably leads to an accumulation of volatile organic compounds (VOCs) that are emitted by e.g. building materials, paint and furniture. Human exposure to VOCs is directly related to the sick building syndrome leading to complaints such as headache, fatigue, dizziness and lack of concentration. In addition, exposure to VOCs is related to serious long-term health effects such as cancer or respiratory diseases. Therefore, significant research efforts are focused on advanced indoor air purification methods. Integration or retrofitting of a photocatalytic (PCO) air purifying unit into heating, ventilation and air conditioning (HVAC) equipment has been chosen as an interesting approach. As a starting point of this thesis, the operational conditions of a ventilation system were mapped. These systems are characterized by high flow rates and the necessity of minimal pressure losses. Pressure losses increase the energy demand and can lead to failure of the ventilation fan and thereby undermine the proper functioning of the ventilation system. A suitable substrate must allow the contaminated air to pass through with a minimal pressure drop, allow sufficient contact time between VOC and photocatalyst, have a large surface area available for coating with excellent adhesion, and be transparent to UV light. Therefore, the permeability and the available exposed surface were selected as main selection criteria. After a thorough quantitative analysis of potential substrates, borosilicate glass tubes were selected. Glass tubes can easily be stacked to constitute a transparent monolithic multi-tube reactor, with their length parallel to the air flow in order to minimize the pressure drop. Moreover, borosilicate glass is relatively inexpensive and has excellent UV-A light transmitting properties. Based on a literature study, a sol-gel coating procedure was selected that is extremely suitable for coating glass substrates. The next step was to optimize the amount of P25 (commercial titanium dioxide) in the photocatalytic sol-gel coating for its application. More P25 in the sol-gel coating results in a higher adsorption capacity and consequently a higher photocatalytic activity, but greatly reduces the transparency of the coating. After an in-depth study, the concentration of 10 g L-1 P25 was selected as the most feasible for multi-tube reactors. Since the operation of photocatalytic reactors is based on a complex interaction of physical and chemical processes, mathematical models were developed, supported by experimental data, that include all these phenomena as a tool for reactor design and optimization. By making use of such models, time-consuming and expensive experimental research can be minimized. However, the experimental validation of models is of utmost importance to prove its reliability and accuracy. Intrinsic kinetic parameters provide the fundamentals for these models as they describe the photocatalytic reaction rate, independent of fluid dynamics, reactor geometry and radiation field. In this work they were estimated by means of a Computational Fluid Dynamics (CFD) study, based on FTIR (Fourier-transform infrared spectroscopy) experiments with a lab scale multi-tube reactor. The kinetic parameters were validated by an alternative analytic approach, emphasizing the accuracy and reliability of the simulations. Finally, the aforementioned CFD approach, based on the simultaneously modelling of airflow, mass transfer, UV light irradiation and photocatalytic reactions, was used to obtain insights for the light source configuration in upscaled multi-tube reactors. After taking all these insights and some practical implications into account, a final upscaled multi-tube reactor design was proposed and converted into a first built prototype. Subsequently, it was evaluated according the CEN-EN-16486-1 standard for VOC removal by the external scientific research center ‘CERTECH’. The scientific results, regarding the mineralization of the VOCs and photocatalytic efficiency of the reactor, demonstrated the feasibility for indoor air purification by the upscaled multi-tube reactor and the possible implementation in ventilation systems.

Abstract: Fiber optic surface plasmon resonance (FO-SPR) has shown its potential for the detection of nucleic acids and more recently the technology has been combined with catalytic active strands such as DNAzymes. In this work, an innovative, generic solid-phase DNA sensor concept is presented, based on FO-SPR and PCR amplified DNAzyme activity. Improved levels of specificity and sensitivity were obtained down to picomolar concentrations. Moreover, the FO-SPR sensor concept enables AuNP amplified DNA target detection, independent of the target sequence length. The FO-SPR sensor was demonstrated for the screening of the mobile colistin resistance (MCR-2) gene, a gene important for the antimicrobial resistance in Gram-negative species such as E. Coli.

Abstract: abstract not available

Abstract: We report on the pressure-driven superconductor-insulator transition in heavily boron-doped nanodiamond films. By systematically increasing the pressure, we suppress the Josephson coupling between the superconducting nanodiamond grains. The diminished intergrain coupling gives rise to an overall insulating state in the films, which is interpreted in the framework of a parallel-series circuit model to be the result of bosonic insulators with preserved localized intragrain superconducting order parameters. Our investigation opens up perspectives for the application of high pressure in research on quantum confinement and coherence. Our data unveil the percolative nature of the electrical transport in nanodiamond films, and highlight the essential role of grain boundaries in determining the electronic properties of this material.

Abstract: A detailed microstructural examination endeavoring to understand the interfacial phenomena yielding to cohesion
in solid-state assembling processes was performed. This study focuses on the transition zone of a dissimilar
titanium alloy joint obtained by Linear Friction Welding (LFW) the β-metastable Ti17 to the near-α
Ti6242. The transition zone delimitating both alloys is characterized by a sharp microstructure change from
acicular HCP (Hexagonal Close-Packed) α′ martensitic laths in the Ti6242 to equiaxed BCC β (Body-Centered
Cubic) subgrains in the Ti17; these α′ plates were shown to precipitate within prior-β subgrains remarkably more
rotated than the ones formed in the Ti17. Both α′ and β microstructures were found to be intermingled within
transitional subgrains demarcating a limited gradient from one chemical composition to the other. These peculiar
interfacial grains revealed that the cohesive mechanisms between the rubbing surfaces occurred in the
single-phase β domain under severe strain and high-temperature conditions. During the hot deformation process,
the mutual migration of the crystalline interfaces from one material to another assisted by a continuous dynamic
recrystallization process was identified as the main adhesive mechanism at the junction zone. The latter led to
successful cohesion between the rubbing surfaces. Once the reciprocating motion stopped, fast cooling caused
both materials to experience either a βlean→α′ or βlean→βmetastable transformation in the interfacial zone depending
on their local chemical composition. The limited process time and the subsequent hindered chemical
homogenization at the transition zone led to retaining the so-called intermingled α’/βm subgrains constituting
the border between both Ti-alloys.

Abstract: Belgian pork production has faced stagnating prices for decades. It remains unclear whether excessive market power from slaughterhouses or meat retailers has played a role in this trend. While market power studies can reveal some of the market dynamics in this setting, this type of research has not yet been applied to the Belgian pork market. The present paper investigates oligopolies and oligopsonies in the pork production sector. We build a new model that focuses on market power dynamics in the market for live pigs and distinguishes horizontal and vertical market power parameters, both for pig farmers and for slaughterhouses. The results follow from an empirical application using unique slaughterhouse data for 2001–2015. The results indicate that the farmers benefit from a significant power advantage in the live pig market, when very modest price demands are taken as a reference. The final market price of live pigs approaches the price requested by the farmers. On the other hand, the measured vertical market power also suggests that a pig farmer does not receive the (modest) full-wage-based salary. The market power of the slaughterhouses is also limited. Market power as a result of collusion—that is, horizontal market power—is present, but is not strong. However, there are significant differences between the slaughterhouses in terms of mark-up on the input prices. These differences reflect differences in company strategy, and this diversity further reduces the possibility to create sector-wide collusive behaviour.

Abstract: One of the emerging challenges in the field of 3D characterization of nanoparticles by electron tomography is to avoid degradation and deformation of the samples during the acquisition of a tilt series. In order to reduce the required electron dose, various undersampling approaches have been proposed. These methods include lowering the number of 2D projection images, reducing the probe current during the acquisition, and scanning a smaller number of pixels in the 2D images. A comparison is made between these approaches based on tilt series acquired for a gold nanoparticle.

Abstract: Climate change, environmental pollution control, and resource utilization efficiency, as well as food security, sustainable agriculture, and water supply are among the main challenges facing society today. Expertise across different academic fields, technologies,anddisciplinesisneededtogeneratenewideastomeetthesechallenges. This “white paper” aims to provide a written summary by describing the main aspects and possibilities of the technology. It shows that plasma science and technology can make significant contributions to address the mentioned issues. The paper also addresses to people in the scientific community (inside and outside plasma science) to give inspiration for further work in these fields.

Abstract: Heterostructures of strongly correlated oxides demonstrate various intriguing and potentially useful interfacial phenomena. LaMnO3/SrMnO3 superlattices are presented showcasing a new high‐temperature ferromagnetic phase with Curie temperature, TC ≈360 K, caused by electron transfer from the surface of the LaMnO3 donor layer into the neighboring SrMnO3 acceptor layer. As a result, the SrMnO3 (top)/LaMnO3 (bottom) interface shows an enhancement of the magnetization as depth‐profiled by polarized neutron reflectometry. The length scale of charge transfer, λTF ≈2 unit cells, is obtained from in situ growth monitoring by optical ellipsometry, supported by optical simulations, and further confirmed by high resolution electron microscopy and spectroscopy. A model of the inhomogeneous distribution of electron density in LaMnO3/SrMnO3 layers along the growth direction is concluded to account for a complex interplay between ferromagnetic and antiferromagnetic layers in superlattices.