This thesis combines field and laboratory studies to address some of the most pressing questions in the field of microplastic research. Specifically, the thesis addresses the topic of microplastics... Show moreThis thesis combines field and laboratory studies to address some of the most pressing questions in the field of microplastic research. Specifically, the thesis addresses the topic of microplastics in the freshwater environment. The research presented covers both the environmental presence and abundance of microplastics, in addition to ecological effects, investigated using observational and experimental studies. These studies give a greater understanding of the abundance, types and sources of microplastics in freshwater systems in the UK, how organisms and chemicals interact with microplastics and the potential ecological effects on a range of freshwater organisms from different functional feeding groups and trophic levels. Show less
The unit residue group, to which the present thesis is devoted, is defined using the norm-residue symbol, which Hilbert introduced into algebraic number theory in 1897. By its definition, the unit... Show moreThe unit residue group, to which the present thesis is devoted, is defined using the norm-residue symbol, which Hilbert introduced into algebraic number theory in 1897. By its definition, the unit residue group of a global field is a direct sum of local contributions. It has a subgroup of a global nature, called the virtual group.We give a precise description of the unit residue groups and their virtual subgroups for some classes of number fields, including all quadratic fields. In addition we point out connections to two classical theorems on ideal class groups, namely the theorem of Armitage and Froehlich on 2-ranks and Scholz’s theorem on 3-ranks.We also study certain subgroups of the multiplicative group of a local field that play an important role in an algorithm for computing norm-residue symbols, and group isomorphisms between the groups of quadratic characters of two number fields that preserve L-series. Show less
Miniaturized satellites enable a variety space missions which were in the past infeasible, impractical or uneconomical with traditionally-designed heavier spacecraft. Especially CubeSats can be... Show moreMiniaturized satellites enable a variety space missions which were in the past infeasible, impractical or uneconomical with traditionally-designed heavier spacecraft. Especially CubeSats can be launched and manufactured rapidly at low cost from commercial components, even in academic environments. However, due to their low reliability and brief lifetime, they are usually not considered suitable for life- and safety-critical services, complex multi-phased solar-system-exploration missions, and missions with a longer duration. Commercial electronics are key to satellite miniaturization, but also responsible for their low reliability: Until 2019, there existed no reliable or fault-tolerant computer architectures suitable for very small satellites. To overcome this deficit, a novel on-board-computer architecture is described in this thesis.Robustness is assured without resorting to radiation hardening, but through software measures implemented within a robust-by-design multiprocessor-system-on-chip. This fault-tolerant architecture is component-wise simple and can dynamically adapt to changing performance requirements throughout a mission. It can support graceful aging by exploiting FPGA-reconfiguration and mixed-criticality. Experimentally, we achieve 1.94W power consumption at 300Mhz with a Xilinx Kintex Ultrascale+ proof-of-concept, which is well within the powerbudget range of current 2U CubeSats. To our knowledge, this is the first COTS-based, reproducible on-board-computer architecture that can offer strong fault coverage even for small CubeSats. Show less
A novel mathematical model describes spatial-temporal drug distribution within one or more brain units, which are cubic representations of a piece of brain tissue with brain capillaries at the... Show moreA novel mathematical model describes spatial-temporal drug distribution within one or more brain units, which are cubic representations of a piece of brain tissue with brain capillaries at the edges. The brain unit can be considered a highly representative building block of the brain in terms of drug distribution. While the focus of the model is on drug distribution within the brain ECF, the model includes descriptions of drug concentrations within the blood plasma, drug distribution via brain capillary blood flow, drug transport across the blood-brain barrier (BBB) by passive paracellular and transcellular transport as well as active transport, brain ECF diffusion, brain ECF bulk flow, non-specific binding of the drug to brain tissue, and drug target binding kinetics. We study the model with analytical methods and numerical simulations. This allows us to examine the integrated effect of the individual processes important to drug distribution and effect on the local concentration-time profiles of free and (non-)specifically bound drug. Moreover, the model allows us to generate a local distribution profile of a drug within the brain. In addition, the impact of disease-induced changes in brain-specific properties on the concentrations of drug within the brain ECF is assessed. Show less
In this thesis, we aimed to better understand the underlying mechanisms involved in TNBC progression and metastasis formation and discover new targets to reduce breast cancer related deaths. We... Show moreIn this thesis, we aimed to better understand the underlying mechanisms involved in TNBC progression and metastasis formation and discover new targets to reduce breast cancer related deaths. We performed an imaging-based RNAi phenotypic cell migration screen in two highly motile TNBC cancer cell lines to provide a repository of signaling determinants that functionally drive TNBC cell motility. Interestingly, two modulators essential for cancer cell migration were known to be involved in RNA splicing, making us decide to focus on the role of RNA splicing in breast cancer progression. We next summarized the current knowledge about splicing factors in breast cancer development and progression and identified co-regulated splicing factors that were associated with aggressive breast cancer phenotypes and metastasis formation that was not only restricted to breast cancer, increasing the global understanding of the role of the spliceosome in cancer development and progression. Moreover, the role of splicing factors in two major processes in cancer progression, cell migration and proliferation, was examined. Finally, using RNA sequencing, we systematically compared the transcriptomes of 14 breast cancer cell lines cultured both in 2D and 3D conditions to unravel the reprogramming that is associated with the invasive phenotype of basal B TNBC. Show less
This thesis describes the genetic and prokaryotic diversity of giant barrel sponges. Although it was originally believed that the giant barrel sponges in the AtlanticOcean and the Indo-Pacific... Show moreThis thesis describes the genetic and prokaryotic diversity of giant barrel sponges. Although it was originally believed that the giant barrel sponges in the AtlanticOcean and the Indo-Pacific Ocean were two different species, our analyses showed thatthere are several species in both ocean basins. Even more remarkable, is that each species is most closely related to a species in the other ocean basin. According to our analysis, there are threegiant barrel sponge species in the Atlantic Ocean, and, at least, six in the Indo-Pacific Ocean. Sponges house a large and diverse community of microorganisms. It is generally believed thatthese microorganisms play a central role in the physiological processes in the host. It appears that the region in which a giant barrel sponge occursmainly determines the composition of their microbial community. However, if you lookat a smaller scale within a region, for example within one reef or around an island suchas Curaçao, it appears that not only is the geographical location important, but the hostspecies to which an individual belongs also plays an important role. Show less
It is an established fact that the Standard Model has to be extended to explain the so-called Beyond the Standard Model (BSM) phenomena: dark matter, matter-antimatter asymmetry of the Universe and... Show moreIt is an established fact that the Standard Model has to be extended to explain the so-called Beyond the Standard Model (BSM) phenomena: dark matter, matter-antimatter asymmetry of the Universe and neutrino flavour oscillations. The difficulty of direct detection of new particles lies in the huge parameter space of the possible candidates. Hence, data coming from the cosmological and astrophysical observations provide invaluable directions for laboratory experiments.In this thesis we explore two methods of constraining new-physics candidates: through their influence on the primordial nucleosynthesis and through observable differences in the matter distribution caused by free-streaming of the dark-matter particles. We concentrate on the well-motivated extension of the SM that aims at explaining all 3 BSM problems at the same time: the Neutrino Minimal Standard Model. In this extension, there are 3 additional heavy neutral leptons, one of which plays the role of dark matter, while the other two are necessary for induction of matter-antimatter asymmetry and neutrino oscillations. The dark-matter candidate is an example of a Warm Dark Matter particle, the free-streaming of which might be detected in the Lyman-α forest spectra of distant quasars. The other two particles have lifetimes that make them relevant to the primordial nucleosynthesis. Show less
Heterogeneous catalysis is essential to many industrial applications. These catalysts are often comprised of supported nanoparticles, which contain various different surface sites. For some... Show moreHeterogeneous catalysis is essential to many industrial applications. These catalysts are often comprised of supported nanoparticles, which contain various different surface sites. For some reactions, the presence of specific surface sights dominates the overall reactivity. Fundamental insight into the influence of different surface sites on the surface reaction dynamics may lead to better catalyst design in the future. In this thesis, we combine ultra-high vacuum techniques and (curved) single crystal surfaces to study surface structure effects relevant to heterogeneous catalysis. We study how step edges on a platinum surface affect (elementary) reactions that occur in oxygen reduction: hydrogen dissociation, hydrogen recombination, and oxygen reduction. Show less
Decentralized plug and play systems for energy production are the future picture of our society. Artificial photosynthetic systems are used for this purpose. These systems are inspired by natural... Show moreDecentralized plug and play systems for energy production are the future picture of our society. Artificial photosynthetic systems are used for this purpose. These systems are inspired by natural photosynthesis.Chapter 2 illustrates the detailed construction of a three-flash flow cell to study light induced biological reactions, specifically the water oxidation reaction of Photosystem II. This instrument is capable of producing the S2+, S3+ and S0n intermediate states of the Kok cycle. I confirmed these by EPR experiments.In chapter 3, I study the mechanism of the major LHC II involved in conformational switching from light harvesting to the photoprotective state, in which excess light is dissipated as heat. I use MAS NMR as a non-invasive method to understand the structure and environment around Arg residues in Chlamydomonas reinhardtii LHC II. In this approach the Arg amino acid is selectively labeled with 13C isotopesChapter 4 studies the structure of self-aggregated semi synthetic Zn 31 amino chlorin that forms syn-anti parallel stacks according to the solid state NMR data. The small change of removing 33 methyl group of Zn 31 aminomethyl chlorin has significant effect on self-assembly. Finally, chapter 5 provides an outlook on future research. Show less
Galaxy intrinsic alignments induce a major astrophysical contamination to weak gravitational lensing measurements and need to be modelled and mitigated when extracting cosmological information from... Show moreGalaxy intrinsic alignments induce a major astrophysical contamination to weak gravitational lensing measurements and need to be modelled and mitigated when extracting cosmological information from such measurements. This dissertation studies the signal of the intrinsic alignment of galaxies in large and small scales. Informative priors are provided for the signal, which improve the constraining power of weak lensing data. Moreover, the dependence of the signal with the observed wavelength is studied, finding significant differences in the alignment of galaxies observed in different bands. The source of this difference appear to be satellite galaxies, and the alignment of galaxies inside galaxy groups is explored, finding that the alignment signal depends on the scale of a galaxy, with outer regions being more strongly aligned that inner ones. Lastly, the alignment of galaxies with their host dark matter halo is probed by measuring the anisotropic weak lensing signal around them, which leads to the conclusion that outer regions of galaxies are also more aligned with their dark matter halo than inner ones. Show less
A large diversity of exoplanetary systems has been found, but it is still unclear what drives this diversity. Planets are formed in disks around young stars, but the sensitivity and resolution of... Show moreA large diversity of exoplanetary systems has been found, but it is still unclear what drives this diversity. Planets are formed in disks around young stars, but the sensitivity and resolution of pre-ALMA data have allowed only a handful of disks to be characterized. ALMA has opened up the possibility to survey hundreds of disks in both the gas and dust, and to also spatially resolve them. The most recent observations of protoplanetary disks in the (sub-)mm emission and in optical/near-infrared scattered light have revealed complex structures such as spirals, rings, gaps and vortices. Planets are often invoked as an explanation, but their number and location are degenerate, and the same system can be often explained by more than one scenario. In this thesis, the origin of these gas and dust structures both through dust observations and through chemical modelling of the gas emission is studied, and the link between the structures observed in the different tracers is investigated.These studies are critical to understand if substructures in disks are the signpost of ongoing planet formation and will ultimately also tell whether and how the variety of structures observed is linked to the diversity in the exoplanetary systems’ properties. Show less
The work presented in this thesis is based on ALMA surveys of protoplanetary disks in three star-forming regions: Lupus, OMC-2, and NGC 2024. The motivation for this thesis is to study the... Show moreThe work presented in this thesis is based on ALMA surveys of protoplanetary disks in three star-forming regions: Lupus, OMC-2, and NGC 2024. The motivation for this thesis is to study the evolution of protoplanetary disks from the population level.The first two chapters focus on the Lupus clouds, a low-mass star-forming region. It has been the subject of a large survey with ALMA, targeting bright gas lines and the emission from millimeter-sized grains. This allows us to answer important questions on disk evolution: how common are >200 AU-sized disks with continuum substructure, and how are these substructures formed? Do compact disks observed in the continuum also correspond to compact gas disks?The chapters focusing on Orion deal with the impact of massive stars on disks. OMC-2 provides a view of a population of disks that are formed in a massive cloud, but isolated from the radiation of massive stars. They link disks that do form near these massive stars to those in low-mass YSOs. NGC 2024 also hosts massive stars, and is the youngest region surveyed; the presence of multiple populations of young stars has been suggested. ALMA allows us to independently test the complexity of this environment. Show less
Multi-objective evolutionary computation aims to find high quality (Pareto optimal) solutions that represent the trade-off between multiple objectives. Within this field there are a number of key... Show moreMulti-objective evolutionary computation aims to find high quality (Pareto optimal) solutions that represent the trade-off between multiple objectives. Within this field there are a number of key challenges. Among others, this includes constraint handling and the exploration of mixed-integer search spaces. This thesis investigates how these challenges can be handled at the same time, and in particular how they can be applied in the multi-objective optimisation algorithms. These algorithms are developed in the context of the optimisation of building spatial designs, which describe the exterior shape of a building, and the internal division into different spaces. Spatial designs are developed early in the design process, and thus have a large impact on the final building design, and in turn also on the quality of the building. Here the structural and thermal performance of a building are optimised to reduce resource consumption. The main contributions of this thesis are as follows. Firstly, a representation for building spatial designs in is introduced. Secondly, specialised search operators are designed to ensure only feasible solutions will be explored. Thirdly, data about the discovered solutions is analysed to explain the results to domain experts. Finally, a general purpose multi-objective mixed-integer evolutionary algorithm is developed. Show less
Chip manufacturers are rapidly moving towards so-called manycore chips with thousands of independent processors on the same silicon real estate. Current programming languages can only leverage the... Show moreChip manufacturers are rapidly moving towards so-called manycore chips with thousands of independent processors on the same silicon real estate. Current programming languages can only leverage the potential power by inserting code with low level concurrency constructs, sacrificing clarity. Alternatively, a programming language can integrate a thread of execution with a stable notion of identity, e.g., in active objects.Abstract Behavioural Specification (ABS) is a language for designing executable models of parallel and distributed object-oriented systems based on active objects, and is defined in terms of a formal operational semantics which enables a variety of static and dynamic analysis techniques for the ABS models.The overall goal of this thesis is to extend the asynchronous programming model and the corresponding analysis techniques in ABS. Show less
While ecosystems have concrete benefits for human society, these benefits are typically overlooked in decision-making. This is problematic because ecosystems – and thus the benefits that... Show moreWhile ecosystems have concrete benefits for human society, these benefits are typically overlooked in decision-making. This is problematic because ecosystems – and thus the benefits that ecosystems provide – are under increasing pressure from human actions. The ecosystem services concept aims to better reflect the benefits of ecosystems for human wellbeing. As a tool to quantify ecosystem services, their value is often estimated in monetary terms. This thesis investigates whether this approach is valid in ecological terms: do monetary value estimates adequately reflect the ecological status of the ecosystem? Two sets of water-related services in two different types of regions have been investigated: water quantity-related services in global drylands (chapters 2 and 3) and water quality-related services in the Scheldt river basin (chapters 4 and 5). The results show that the selected methodological approach has a dominant impact on value estimates for water-related services, while the ecological status of the ecosystem is of minor importance. This finding casts doubts upon the validity of monetary valuation as a means to take the ecological status of ecosystems into account in public decision-making. Future research should explore how the ecosystem’s ecological status can be better integrated in the valuation of ecosystem services. Show less
In this dissertation, matching, entropy, holes and expansions come together. The first chapter is an introduction to ergodic theory and dynamical systems. The second chapter is on, what we called... Show moreIn this dissertation, matching, entropy, holes and expansions come together. The first chapter is an introduction to ergodic theory and dynamical systems. The second chapter is on, what we called Flipped $\alpha$-expansions. For this family we have an invariant measure that is $\sigma$-finite infinite. We calculate the Krengel entropy for a large part of the parameter space and find an explicit expression for the density by using the natural extension. In Chapter 3 Ito Tanaka's $\alpha$-continued fractions are studied. We prove that matching holds almost everywhere and that the non-matching set has full Hausdorff dimension. In the fourth chapter we study $N$-expansions with flips. We use a Gauss-Kuzmin-Levy method to approximate the density for a large family and use this to give an estimation for the entropy. In the last Chapter we look at greedy $\beta$-expansions. We show that for almost every $\beta\in(1,2]$ the set of points $t$ for which the forward orbit avoids the hole $[0,t)$ has infinitely many isolated and infinitely many accumulation points in any neighborhood of zero. Furthermore, we characterize the set of $\beta$ for which there are no accumulation points and show that this set has Hausdorff dimension zero. Show less
This thesis described the development of novel scanning tunneling microscopy techniques to investigate strongly correlated electronic states in quantum matter.
The PID-directed shift in PIN polarity has been broadly accepted as one of the essential mechanisms for the regulation of auxin transport polarity. We verified that both PID functionality and its... Show moreThe PID-directed shift in PIN polarity has been broadly accepted as one of the essential mechanisms for the regulation of auxin transport polarity. We verified that both PID functionality and its subcellular localization do not depend on PDK1 function. However, by detailed analysis on these phenotypes and the expression of the auxin response reporter, we found the pdk1 pdk2 double mutant to be impaired in auxin transport in vascular tissues. Together with other mutant phenotypes, we suspect that PDK1 may be the master regulator of AGC1 kinases. The pdk1 pdk2 short root phenotype caused by phloem differentiation defects phenocopied the pax mutant. Complementation results of wild type and phosphomimic PAX in the pdk1 pdk2 background suggest that PDK1-dependent PAX phosphorylation and activation are essential for its full biological function. We also explain the molecular basis of PDK1 basal localization and the unnecessity of this polarity for vascular development. In addition, we investigated downstream action after PID phosphorylation. Several conserved tyrosine residues close to serine phosphorylation sites in the PIN1 and PIN2 HLs are mutated. Two of these tyrosines redundantly affected PIN polarity. However, PID mediated phosphorylation and tyrosine-based PIN trafficking are independent processes. Show less
The LOFAR radio telescope produces petabytes of data every year. Radio Astronomers use complex multi-step pipelines to process this data and produce scientific images. In this thesis, we describe... Show moreThe LOFAR radio telescope produces petabytes of data every year. Radio Astronomers use complex multi-step pipelines to process this data and produce scientific images. In this thesis, we describe methods for astronomers to efficiently process massive amounts of data on high-throughput clusters. We gain insights into efficient acceleration of complex scientific pipelines, as well as understanding of the scalability of the underlying software. These insights ensure the scientific output of LOFAR keeps up with the pace of the data the telescope produces. Moreover, our results can be applied to arbitrary scientific studies, greatly increasing the potential of the LOFAR telescope. Finally, our discoveries can be applied to current and future telescopes. These lessons will help astronomers efficiently producing science in the big data era. Show less
