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“Molecular spectroscopy study of human tooth tissues affected by high dose of external ionizing radiation (caused by the nuclear catastrophe of the Chernobyl plant)”. Darchuk LA, Zaverbna LV, Worobiec A, Van Grieken R page 349 (2012).
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
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“High-resolution X-ray fluorescence micro-tomography on single sediment particles”. Vincze L, Vekemans B, Szalóki I, Janssens K, Van Grieken R, Feng H, Jones KW, Adams F page 240 (2002).
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Times cited: 11
DOI: 10.1117/12.452865
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“Monte Carlo simulation of X-ray fluorescence and scattering tomography experiments”. Vincze L, Janssens K, Vekemans B, Adams F page 328 (1999).
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1117/12.363736
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“Recent advances in electrochemical biosensors based on fullerene-C60 nano-structured platforms”. Pilehvar S, De Wael K page 173 (2017).
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Risks of atmospheric aerosol for cultural heritage assets in Granada (Spain)”. Cardell C, Urosevic M, Sebastián-Pardo E, Horemans B, Kontozova-Deutsch V, Potgieter-Vermaak S, Bencs L, Anaf KW, De Wael K, Van Grieken R page 45 (2013).
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Atmospheric aerosols in the Asian part of the former Soviet Union”. Van Grieken R, Jaenicke R, Koutsenogii KP, Khodzher TV, Kulipanov GN page 197 (1999).
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Identification and distribution of metal soaps and oxalates in oil and tempera paint layers in fifteenth-century altarpieces using synchrotron radiation Techniques”. Salvadó N, Butí S, Pradell T, Beltran V, Cinque G, Juanhuix J page 195 (2019).
Abstract: The formation and distribution of metal soaps produced as a result of the reactivity and aging of the materials in a fifteenth-century egg tempera and oil paintings on wood are presented. The painting technique involves the application of several paint layers over a ground using, sometimes in the same paint layer sequence, drying oil and egg yolk binders. We show, with a selection of examples, how the use of thin sections and a combination of various micro-sensitive analytical techniques is adequate to obtain the high-quality data necessary for the unambiguous identification of metal soaps and metal oxalates as well as their distribution in the paint layers. The techniques include micro infrared spectroscopy (μSR-FTIR) and micro X-ray diffraction (μSR-XRD) with synchrotron radiation, optical microscopy (OM), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The data obtained sheds light about the underlying reaction and aging mechanisms happening in each paint layer and among them. This helps to define the state of conservation of the artworks.
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1007/978-3-319-90617-1_11
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“X-ray fluorescence analysis, sample preparation for”. Margu'i' E, Queralt I, Van Grieken R page 1 (2009).
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Characterization and removal of a disfiguring oxalate crust on a large altarpiece by Hans Memling”. Klaassen L, van der Snickt G, Legrand S, Higgitt C, Spring M, Vanmeert F, Rosi F, Brunetti BG, Postec M, Janssens K page 263 (2019).
Abstract: During the conservation treatment of Memling’s Christ with Singing and Music-making Angels, three panel paintings that are among the most monumental works in early Netherlandish art, the conservators came across insoluble surface layers containing calcium oxalates. A very thin and irregular layer of this type, hardly visible to the naked eye, was spread across the surface of all three panels. A much thicker layer forming an opaque and highly disfiguring crust that obscured the composition (Figs. 15.1 and 15.7) was locally present on areas of dark copper-containing paint, where multiple layers of old discolored coatings and accretions remained in place before the most recent cleaning. This article describes the application of a wide range of analytical techniques in order to fully understand the stratigraphy and composition of the crusts on the Memling paintings. FTIR spectroscopy in transmission and reflection mode, micro-ATR-FTIR imaging and macro-rFTIR scanning, SEM-EDX, mobile XRD, and SR-μXRD showed that the crusts contained two related Ca-based oxalate salts, whewellite and weddellite, and were separated from the original paint surface by varnish, indicating that they did not originate from degradation of the original paint but from a combination of microbial action and a thick accumulation of dirt. Supported by the results from these different analytical techniques, which when used together proved to be very effective in providing complementary information that addressed this specific conservation problem, and aided by the presence of the intermediate varnish layer(s), the conservators were able to remove most of the crusts with spectacular results.
Keywords: H1 Book chapter; Art; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
DOI: 10.1007/978-3-319-90617-1_15
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“Chemical alteration and colour changes in the Amsterdam sunflowers”. Monico L, Hendriks E, Geldof M, Miliani C, Janssens K, Brunetti BG, Cotte M, Vanmeert F, Chieli A, Van der Snickt G, Romani A, Melo MJ page 125 (2019).
Abstract: This chapter provides a description of colour changes in the Amsterdam Sunflowers due to chemical alteration of pigments, with a focus on geranium lakes and chrome yellows. The brilliant and forceful colours of these and other late nineteenth-century synthetic materials offered artists such as Vincent van Gogh new means of artistic expression that exploited a range of contrasting hues and tints. However, geranium lakes have a strong tendency to fade and chrome yellows to darken under the influence of light. Van Gogh, like other artists of his day, was aware of this drawback, yet he continued to favour the use of both pigments up until his death in July 1890 due to the unparalleled effects they gave. In April 1888, Vincent wrote to his brother Theo: Van Gogh's use of unstable colours opens a series of questions regarding the extent to which colour change affects the way his paintings look today, as discussed here in relation to the Amsterdam Sunflowers. Furthermore, given the frequency with which geranium lakes and chrome yellows occur in Van Gogh's paintings of the period 1888–90 and the predominance of chrome yellows in Sunflowers, it becomes important to understand the factors that can drive these processes of deterioration in order to develop appropriate strategies for conserving the artist's works.
Keywords: H1 Book chapter; Art; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
DOI: 10.1017/9789048550531.006
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“Conservation of the Amsterdam sunflowers : from past to future”. Hendriks E, Geldof M, van den Berg KJ, Monico L, Miliani C, Moretti P, Iwanicka M, Targowski P, Megens L, de Groot S, van Keulen H, Janssens K, Vanmeert F, van der Snickt G page 175 (2019).
Abstract: This chapter lays out a conservation timeline, from past to future, for the Amsterdam version of Van Gogh's Sunflowers. It starts by considering the restoration history of the painting in order to assess its current physical state, and looks ahead to formulate an appropriate strategy for future conservation treatment and display. Due attention is paid to the two recorded episodes of restoration performed in 1927 and 1961 by the Dutch restorer, Jan Cornelis Traas. Based on physical and chemical investigation of Sunflowers we attempt to reconstruct what these former treatments (which are barely documented) entailed and consider the repercussions for the present condition of the painting. The former interventions by Traas also serve as a benchmark to reflect on current choices made, highlighting the extent to which ideas and methodologies have continued to evolve over the past century as conservation has moved further away from being a singularly craft-based activity to become an established historical and scientific discipline underpinned by ethical guidelines. Jan Cornelis Traas (1898–1984) As mentioned, the two main recorded interventions to the Amsterdam Sunflowers may be associated with the Dutch restorer, Jan Cornelis Traas, who treated the picture in 1927, close to the start of his career, and again in 1961, shortly before he retired. Traas was the first restorer to be appointed at the Mauritshuis in The Hague where he worked from 1931 to 1962 and treated hundreds of paintings, including iconic masterpieces such as Girl with a Pearl Earring by Johannes Vermeer. Yet despite the magnitude and importance of his restoration oeuvre, J.C. Traas (as he is usually referred to in surviving documents), has remained somewhat obscure. He is shown here in the only known surviving photograph of him at work, shortly before he retired (fig. 7.1). Unlike his illustrious contemporaries, A. Martin de Wild (1899–1969) and Helmut Ruhemann (1891–1973), for example, Traas did not publish anything, he appears to have kept no records of his work and no personal archive is known. However, the study of some newly discovered historical documents, combined with physical examination of Sunflowers and a large number of other works he treated, allows us to recover an idea of his working practices and approaches viewed within the context of his day.
Keywords: H1 Book chapter; Art; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
DOI: 10.1017/9789048550531.008
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“Methods and materials of the Amsterdam sunflowers”. Geldof M, Monico L, Johnson DH, Miliani C, Romani A, Grazia C, Buti D, Brunetti BG, Janssens K, Van der Snickt G, Vanmeert F page 85 (2019).
Abstract: This chapter explains the materials and techniques employed in the Amsterdam Sunflowers, enabling a comparison with the London version described in chapter 3. Building upon the 2016 article published in the National Gallery Technical Bulletin, it incorporates the latest findings gained by computer-assisted methods used to characterize the canvas support, as well as in-situ campaigns of non-invasive investigation together with further analysis of microscopic paint samples. The chapter sequence follows the steps in Van Gogh's working practice. Starting with the canvas, automated analysis of the weave enables the provenance of the canvas to be traced back to a particular roll of linen ordered by Van Gogh. Combining technical evidence with knowledge of historical manufacturing techniques further allows us to reconstruct the way in which Van Gogh divided his canvas roll into pieces used for Sunflowers and other paintings. We go on to consider how, with the original painting at hand, he used charcoal to transfer the motif of the London Sunflowers onto his blank canvas. Despite careful planning of the composition, an adjustment was required late in the working process, when Van Gogh added a painted wooden strip to extend the background above the flower at the top edge of the canvas. The artist's process of working up the composition in paint is described, paying special attention to his use of colour. The pigments and pigment mixtures used in the Amsterdam Sunflowers have been comprehensively mapped and are compared with the London picture, with discussion of some similarities and differences that account for the distinctive colour scheme of each painting. This understanding of colour application in the Amsterdam Sunflowers lays the foundation for subsequent chapters that will go on to consider the impact of light-induced colour changes that have taken place over time, and the related need to define appropriate lighting guidelines for the future safe preservation of this painting and others made with similar materials (chapters 5 and 7).
Keywords: H1 Book chapter; Art; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
DOI: 10.1017/9789048550531.005
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“Non-invasive and non-destructive examination of artists’ pigments, paints and paintings by means of X-ray imaging methods”. Vanmeert F, De Meyer S, Gestels A, Clerici EA, Deleu N, Legrand S, Van Espen P, Van der Snickt G, Alfeld M, Dik J, Monico L, De Nolf W, Cotte M, Gonzalez V, Saverwyns S, Depuydt-Elbaum L, Janssens K page 317 (2022).
Abstract: Recent studies in which X-ray beams of (sub)micrometre to millimetre dimensions have been used for non-destructive analysis and characterization of pigments, minute paint samples and/or entire paintings from fifteenth to twentieth century artists are discussed. The overview presented encompasses the use of laboratory and synchrotron radiation-based instrumentation and deals with the use of several variants of X-ray fluorescence (XRF) as a method of elemental analysis and imaging as well as with the combined use with X-ray diffraction (XRD). Microscopic XRF (μ-XRF) is a variant of the XRF method able to visualize the elemental distribution of key elements, mostly metals, on the scale from 1 μm to 100 μm present inside multi-layered micro samples taken from paintings. In the context of the characterization of artists’ pigments subjected to natural degradation, in many cases the use of methods limited to elemental analysis or imaging does not suffice to elucidate the chemical transformations that have taken place. However, at synchrotron facilities, combinations of μ-XRF with related methods such as μ-XAS (microscopic X-ray absorption spectroscopy) and μ-XRD have proven themselves to be very suitable for such studies. Since microscopic investigation of a relatively limited number of minute paint samples may not yield representative information about the complete artefact they were taken from, several methods for macroscopic, non-invasive imaging have recently been developed. Combined macroscopic XRF/XRD scanning is able to provide a fairly complete overview of the inorganic pigments employed to create a work of art, to answer questions about ongoing degradation phenomena and about its authenticity. As such these newly developed non-invasive and highly specific imaging methods are of interest for many cultural heritage stakeholders.
Keywords: H1 Book chapter; Art; Antwerp Cultural Heritage Sciences (ARCHES); Antwerp X-ray Imaging and Spectroscopy (AXIS)
DOI: 10.1007/978-3-030-86865-9_11
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“Foodborne outbreaks : sources and mode of transmission of foodborne pathogenic microorganisms”. Kollarahithlu SC, Sathiyamoorthy S, Thiruvottriyur Shanmugam S, De Wael K, Das J, Veluswamy P page 93 (2023).
Abstract: The foodborne pathogens and microorganisms have played a prevalent role in the ebb and flow of the economy worldwide. The increasing population has strained the food processing industry to produce food in large quantity, which in turn has affected the quality of food. To curb this issue, there is immense pressure to produce and maintain quality food within a short time frame. Hence, high throughput technology is used to determine and timely assess the safety and hygiene of food. Further, the revolution of the food industry has also seen an upsurge of new pathogens and microorganisms, thereby increasing the risk of exposure towards rarest diseases to a larger population. This chapter sheds light on the different types of foodborne pathogens affecting the food industry and its social impact. It further emphasizes the safety measures to be taken on the prevention of the disease from the farm to the processing industries and in turn to the household.
Keywords: H1 Book chapter; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
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Pascucci F (2024) Superfluidity in exciton bilayer systems : Josephson effect and collective modes as definitive identification-markers. xiii, 126 p
Abstract: This thesis explores superfluidity in exciton bilayer systems, semiconductor structures with two thin conducting layers, one doped with electrons and the other with holes, separated by a few nanometers. Theoretical predictions suggest these systems can exhibit superfluid, supersolid, exciton normal solid, and Wigner crystal phases. Identifying clear markers of superfluidity is crucial due to experimental challenges in confirming excitonic superfluidity. This thesis focuses on two phenomena: the Josephson effect and density collective modes. For the Josephson effect, we propose an exciton bilayer Josephson junction in double monolayer Transition Metal Dichalcogenides. We suggest using the Shapiro method to measure the exciton Josephson current and propose fabricating the device with a tunable potential-barrier height. In low potential-barrier regions, the exciton superfluid flows over the barrier, while in high potential-barrier regions, flow is driven by quantum tunnelling. This helps delineate the boundary between Bose-Einstein Condensate (BEC) and BCS-BEC crossover regimes. For density collective modes, we examine low-temperature behaviour to identify the normal-superfluid transition as a function of density. In the normal state at high density, the system exhibits low-energy optic and acoustic modes. As density decreases, entering the superfluid phase, the response changes, with the superfluid gap blocking these modes. We expect pair-breaking collective modes to appear at the onset of exciton superfluidity due to the Coulomb interaction. Our theoretical model developed using a path-integral approach and the Hartree-Fock approximation, includes screening and intralayer correlations. We calculate gap and number equations governing superfluid phase behaviour, showing that intralayer correlations enhance screening, especially in the BCS-BEC crossover regime. This leads to a reduced superfluid gap, a shift in the BEC to BCS-BEC crossover boundary to lower densities, and the disappearance of a predicted minimum in electron-hole pair size. This study advances the understanding of superfluidity in exciton bilayer systems, providing theoretical predictions and experimental proposals. By identifying clear markers of superfluidity, this work contributes to the broader effort of realizing and characterizing excitonic condensed phases in realistic systems.
Keywords: Doctoral thesis; Theory of quantum systems and complex systems; Condensed Matter Theory (CMT)
DOI: 10.63028/10067/2078520151162165141
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Van Putte N (2023) Improving groundwater dynamics : a key factor for successful tidal marsh restoration. 166 p
Abstract: Tidal marshes take up and release certain elements from and to the river water. Hence, they act as a filter, improving the estuarine water quality. This filtering function depends on the interaction between the marsh soil and water that infiltrates into the marsh platform at high tide and seeps out of the creek banks at low tide. In the past centuries, many tidal marshes disappeared due to large scale land reclamations, together with their associated ecosystem services. Nowadays, tidal marshes are increasingly restored on formerly embanked agricultural areas to regain these ecosystem services. Here, we studied the effect of historical agricultural land use on the contribution of restored tidal marshes to water quality improvement, and we investigated several solutions to stimulate the water quality improving function in newly restored tidal marshes. In restored tidal marshes, the soil is often compacted due to the historical agricultural land use, leading to a reduced organic matter content and micro- and macroporosity. In this compacted soil, groundwater flow is hindered, leading to a more waterlogged soil and reduced groundwater dynamics in the restored marsh as compared to a natural marsh. The depth of groundwater drainage and the groundwater flow velocity have important implications for the processes that contribute to water quality improvement, e.g. removal of nitrogen, phosphorus retention and silica cycling. Where groundwater drains deeper, i.e. in the vicinity of tidal creeks and in a more porous soil, these processes are promoted. We suggest that, in newly restored tidal marshes, the soil porosity can be increased by amending the soil (e.g. with organic matter), and the distance to the nearest tidal creek can be reduced by creek excavation. Numerical modelling showed that the largest gain in groundwater dynamics and seepage was attained when both measures were applied together. The effect of organic soil amendments on groundwater dynamics and nutrient cycling was further explored in a large scale in situ mesocosm experiment. Where the soil was amended, groundwater drained deeper and nitrogen removal increased. For new tidal marsh restoration projects, we advise to conduct an explorative soil study. When the soil is heavily compacted, design measures, such as creek initiation and organic soil amendments can be applied to jumpstart the contribution to water quality improvement of newly restored tidal marshes.
Keywords: Doctoral thesis; Sustainable Energy, Air and Water Technology (DuEL); Ecosphere
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Muys M (2019) Microbial protein as sustainable feed and food ingredient : production and nutritional quality of phototrophs and aerobic heterotrophs. 262 p
Abstract: In iets meer dan 30 jaar moeten we tot 50% meer eiwit produceren, terwijl onze conventionele lineaire voedselproductieketen reeds de grenzen van duurzaamheid overschrijdt. Microbieel eiwit (MP), de eiwitrijke biomassa van micro-organismen, werd onderzocht als nieuw voeder en voedselingrediënt in een circulaire eiwitproductieketen. MP-productie kan gebaseerd zijn op primaire grondstoffen om zo de inefficiënte stappen in de huidige eiwitproductie over te slaan, of de productie kan gebaseerd zijn op secundaire grondstoffen afkomstig van de verliezen in de conventionele productieketen (bijvoorbeeld afvalwater). Zowel indirecte als directe strategiën voor nutriëntenherwinning kunnen geïdentificeerd worden. Indirecte nutriëntenherwinning werd onderzocht door struviet toe te passen als fosfor- en stikstofbron voor MP-productie. Struviet, een herwinningsproduct in de afvalwaterzuivering, bleek een hoge zuiverheidsgraad te hebben waardoor het een uitstekende selectieve barrière vormt tussen afvalstroom en MP productie. Oplossingssnelheden en MP groei-experimenten toonden aan dat struviet gemakkelijk gedoseerd kan worden in functie van de microbiële nutriëntenbehoeftes, waarnaast problemen vermeden worden gerelateerd aan de turbiditeit van nevenstromen, wat de productie van fototrofe MP mogelijk maakt. Daarnaast werd ook directe nutriëntenherwinning onderzocht. Hierbij werden de voedingswaarde en veiligheid geanalyseerd van biomassa bestaande uit aerobe heterotrofe bacteriën (AHB) afkomstig van effluentzuivering van 25 bedrijven in de voedings- en drankensector. Verder werd ook de temporele variabiliteit in kaart gebracht. Er werd een veelbelovend eiwitgehalte geobserveerd waarvan de variabiliteit aanzienlijke was. Verder werd aangetoond dat het eiwitgehalte positief gecorreleerd was met stikstofbelasting en negatief met slibverblijftijd, wat een indicatie is dat de implementatie van een geoptimaliseerd productieproces, de biomassakwaliteit gevoelig kan verhogen. Bovendien was de veiligheid als veevoeder gegarandeerd op vlak van de meeste contaminanten. In het daarop volgende hoofdstuk werd de variabiliteit in voedingswaarde en veiligheid bestudeerd van commerciële fototrofe MP (de microalgen Chlorella en Spirulina), gekweekt op primaire grondstoffen. De waargenomen variabiliteit in voedingswaarde vereist verdere optimalisatie van het productieproces. Er werd ook waargenomen dat een hoog eiwitgehalte geen hoge totale voedingswaarde impliceert, omdat de verteerbaarheid en de eiwitkwaliteit nog steeds ongunstig kunnen zijn. Op basis van gemeten contaminanten geeft een veilige consumptiedosis aan dat microalgen perfect kunnen worden geconsumeerd als volwaardige eiwitbron in plaats van als supplement, hun huidige hoofdtoepassing. In een laatste experimenteel hoofdstuk werd onderzocht hoe de variabiliteit in biomassakwaliteit van microalgen kan worden gereduceerd en hoe een stabiele, hoogwaardige biomassaproductie kan worden bekomen. De invloed van oogsttijd, operationele modus en fotoperiode werd bepaald op de productiviteit van biomassa, eiwit en essentiële aminozuren en er werden optimale productieparameters geïdentificeerd. Samengevat is MP-productie op basis van indirecte en directe nutriëntenherwinning veelbelovend. Verdere technologische ontwikkelingen en het verhogen van bewustwording en sociale acceptatie, moeten een verdere introductie van MP in de voeder- en voedingsmarkt faciliteren. Hier kan MP een belangrijke oplossing vertegenwoordigen om de exponentieel groeiende wereldbevolking op een duurzame manier te voeden.
Keywords: Doctoral thesis; Sustainable Energy, Air and Water Technology (DuEL)
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Zhu W (2021) Microbial resource management for mainstream partial nitritation/anammox : strategies to enhance the nitrogen conversion efficiency. 207 p
Abstract: This thesis provides three potential ways to enhance the nitrogen removal efficiency of mainstream partial nitritation/anammox (PN/A), a key technology to enable energy-positive sewage treatment. In Chapter 1, the typical technologies to promote nitrogen removal efficiency are summarized. In Chapters 2 and 3, the concept ‘winter bioaugmentation with stored summer surplus sludge’ is proposed. Applying that, a cost-effective sludge preservation strategy is required. Preserving PN/A biomass without cooling and redox adjustment proved to be the cost-effective strategy. The reactivation of these stored sludges was also tested in low-temperature systems (15 and 10℃). Respectively 56% and 41% of granules activity compared to pre-storage activity (after Arrhenius-based temperature correction) could be recovered within a month (41% and 32% for flocs activity). In the end, the stored AnAOB bioaugmentation was successfully validated in the lab (20℃). In Chapter 4, a return-sludge nursery concept, applying the sidestream nitritation and blending the resulting effluent with mainstream effluent to achieve an intermediate temperature and nitrogen concentrations, is proposed. That led to a 33 – 36% increase in nitrogen removal efficiency. Arrhenius’ expectations (10 ℃ higher temperature, θ = 1.09) could only explain 49-51% of the activity increase in the nursery reactor, pointing to the role of other factors, e.g., the ~400% elevated electrical conductivity (15-16%), the 56-335% higher effluent nitrogen concentrations (12-14%), and the synergy and unknown factors (20-23%). Thus, the return-sludge biostimulation approach could also enhance nitrogen efficiency in the mainstream. In Chapter 5, the N2O emissions, linked to three typical nitrite-oxidizing bacteria (NOB) suppression strategies (low dissolved oxygen (DO) level, free ammonia (FA), and free nitrous acids (FNA) treatments) were tested in a biofilm system. A low emerged DO level (~0.60 mg O2 L-1) was effective to suppress NOB activity and decrease N2O emissions, but NOB adaptation gradually appeared after 200 days. Further NOB inhibition was successfully achieved by periodical (3 hours per week) FA (~30 mg NH3-N L-1) or FNA (~3 mg HNO2-N L-1) treatments. The FA treatment promoted N2O production, while the FNA treatment had no effect. Thus, PN/A systems should be operated at relatively low DO levels with periodical FNA treatment. In Chapter 6, the major findings proposed and the main conclusions drawn in this thesis are outlined. Beyond that, the possible design of a mainstream PN/A configuration that combined all described three technologies is demonstrated. Overall, the novel insights from this thesis potential to improve nitrogen removal efficiency in the mainstream.
Keywords: Doctoral thesis; Sustainable Energy, Air and Water Technology (DuEL)
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Conti S (2020) Multi-band superfluidity and BEC-BCS crossover in novel ultrathin materials. 123 p
Keywords: Doctoral thesis; Sociology; History; Condensed Matter Theory (CMT)
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Shaw P (2021) Dual action of reactive species as signal and stress agents in plasma medicine : combined computational and experimental research. 191 p
Abstract: Reactive oxygen and nitrogen species (RONS) generated by cold atmospheric plasma (CAP) can activate discrete signaling transduction pathways or disrupt redox cellular homeostasis, depending on their concentration. This makes that CAP possesses therapeutic potential towards wound healing, cancer, and other diseases. In order to effectively use CAP in the clinic, a clear understanding of the interaction of RONS with biomolecules (lipids, proteins and nucleic acids) from the atomic to the macro scale, and their biological significance, is needed. In this work, I have therefore studied the dual role of CAP-derived RONS, i.e., (i) in the signaling pathways involved in wound healing, and (ii) in their reaction with biomolecules to cause oxidation-mediated damage. I performed computer simulations to provide fundamental insight about the occurring processes that are difficult or even impossible to obtain experimentally. Furthermore, next to computational studies, I used both 2D and 3D tissue cultures. 3D model allows proliferation in a more physiologically relevant geometry that stimulates the production of extracellular matrix proteins. I investigated the treatment of human gingival fibroblasts with low doses of CAP-generated RONS. This treatment demonstrated that it can inhibit colony formation but does not induce cell death, induce the expression of metalloprotease proteins, induce extracellular matrix degradation, and promote cell migration, which could result in enhanced wound healing. In contrast, at high concentrations, RONS can disrupt the cell membrane integrity and induce cancer cell death through oxidative stress-mediated pathways. I discovered how oxidation of the cell membrane (lipid-peroxidation) can facilitate the access of a drug (Melittin) into cancer cells, and in this way, reduce the required therapeutic dose of Melittin in melanoma and breast cancer cells (demonstrated using in vitro, in ovo and in silico approaches). Furthermore, I studied how excessive lipid-oxidation in chemoresistant pancreatic cancer cells promotes ferroptotic cell death. This was due to the stimulation of the iron-dependent Fenton reaction by targeting a redox specific signaling network. However, upon oxidative stress, cells protect themselves via a sophisticated intracellular antioxidant system that involves the regulation of glutathione/glutathione peroxidase 4 (lipid repair enzyme). Cancer cells exhibited increased levels of intracellular RONS due to their hyper metabolism, leading to high expression of anti-oxidant systems. I therefore focus on the effect of reactive species on the intracellular anti-oxidant system and corresponding DNA damages in both temozolomide-sensitive as well as temozolomide-resistant glioblastoma spheroids, in a 3-dimensional tumor model with a more complex tumor microenvironment than cell monolayers.
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Center for Oncological Research (CORE)
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Van Loenhout J (2021) Targeting pancreatic ductal adenocarcinoma and glioblastoma with oxidative stress-mediated treatment strategies : focus on tumor cell death and modulation of the tumor microenvironment. 167 p
Abstract: Pancreatic ductal adenocarcinoma (PDAC) and glioblastoma multiforme (GBM) are two of the most malignant solid tumor types with poor survival rates, which underscore the urgency of novel and efficacious treatment strategies. Within the last decade, immunotherapy has been established as a breakthrough in cancer therapy. This mainly has been driven by the clinical data and approval associated with several immune checkpoint inhibitors (e.g. anti-CTLA-4 and anti-PD-1/L1). Despite the clinical benefit in specific tumor types, these inhibitors have not yet fulfilled their promise in low immunogenic tumors such as PDAC and GBM. Oxidative stress in cancer cells due to elevated reactive oxygen species (ROS) and an inability to balance intracellular redox state has recently been highlighted as promising target for anticancer treatment strategies with possible immunogenic effects. In this PhD dissertation, I investigated novel oxidative stress-mediated treatment approaches to target PDAC and GBM and to enhance immunogenicity by inducing immunogenic cell death (ICD). In the first part of this thesis (chapter 2), I reviewed the mechanistic responses of cancer cells towards different oxidative stress-inducing treatment strategies and their immunomodulating effects. The resulting literature demonstrated that different exogenous and endogenous ROS-inducing therapies show direct and indirect immunomodulating effects, which can be either immunostimulatory or immunosuppressive. One of the indirect immunostimulatory effects of the ROS-mediating therapies is the capacity of inducing immunogenic cell death (ICD) in tumor cells, which can increase the immunogenicity and consequently can trigger an antitumoral immune response. In chapter 3, I investigated a novel exogenous ROS-inducing treatment method, namely cold atmospheric plasma, to determine the therapeutic and ICD-inducing effects in PDAC, in vitro. I revealed that plasma-treated PBS (pPBS) has the potential to induce ICD in pancreatic cancer cells (PCCs) and to reduce the immunosuppressive tumor microenvironment (TME) by attacking the tumor supportive pancreatic stellate cells (PSCs). Although the cell death induced in PSCs was non-immunogenic as seen by the lack of danger-associated molecular patterns (DAMPs) emission and DC activation, I showed that pPBS could disrupt the physical barrier and lower the immunosuppressive secretion profile (lower TGF-β) of PSCs. In contrast, DAMPs were released by PCCs after treatment with pPBS which resulted in activation and maturation of DCs and a more immunostimulatory secretion profile (higher TNF-α, IFN-γ). Hence, indirect plasma treatment via pPBS has the potential to enhance immunogenicity in PDAC by triggering ICD and by attacking the immunosuppressive PSCs. Tumor cells can evolve adaptation mechanisms to protect themselves against intrinsic oxidative stress by upregulation of pro-survival molecules and their antioxidant defense system to maintain the redox balance. As such, tumor cells can become resistant towards exogenous ROS-inducing therapies, like plasma. Dual targeting of the redox balance of tumor cells by increasing exogenous levels of ROS and inhibiting the antioxidant defense system can maximally exploit ROS-mediated cell death mechanisms as therapeutic anticancer strategy. In this regard, cold atmospheric plasma was combined with auranofin, a thioredoxin reductase inhibitor, in GBM (chapter 4). A synergistic effect was shown after this combination treatment in 2D and 3D, however, in 3D only high concentrations of auranofin synergized with plasma treatment. I confirmed a ROS-mediated response after combination treatment, which was able to induce distinct cell death mechanisms, specifically apoptosis and ferroptosis. Additionally, the auranofin and plasma combined treatment strategy induced cell death, which resulted in an increased release of DAMPs. Together with the observed DC maturation, these results indicates the potential increase in immunogenicity, though, the phagocytotic capacity of DCs was inhibited by auranofin. In chapter 5, I evaluated this promising oxidative stress combination therapy in GBM, in vivo. A decrease in tumor kinetics and an increased survival in GBM-bearing mice was observed when auranofin was sequentially combined with direct plasma treatment. No T cell infiltration was observed after auranofin monotherapy. However, further characterization of the TME after the combination therapy is necessary to provide more insight in the immunogenic effects in vivo. In conclusion, this PhD dissertation comprises novel and important therapeutic and immunogenic insights in cold atmospheric plasma and auranofin as promising oxidative stress-mediated treatment strategies for low immunogenic tumors, like PDAC and GBM. These preclinical results provide a solid basis for future research towards combinations with immunotherapeutic approaches.
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Center for Oncological Research (CORE)
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Yusupov M (2014) Atomic scale simulations for a better insight in plasma medicine. Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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Eckert M (2010) Combined molecular dynamics and Monte Carlo simulations for the deposition of (ultra)nanocrystalline diamond. Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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Aghaei M (2014) Computational study of inductively coupled plasma mass spectroscopy (ICP-MS). Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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Setareh M (2014) Computational study of CH4 and CF4 conversion in presence of N2 and O2 in plasma discharges applied. Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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Aerts R (2014) Experimental and computational study of dielectric barrier discharges for environmental applications. Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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Bogaerts A (1996) Mathematical modeling of a direct current glow discharge in argon. Universitaire Instelling Antwerpen, Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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Wendelen W (2014) Modeling ultrashort pulsed laser induced electron emission. Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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Autrique D (2014) Multiphase modelling of a ns-laser-irradiated copper sample. Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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Khalilov U (2013) New perspectives on thermal and hyperthermal oxidation of Si surfaces. Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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