Faculty of Science

 

Recent Submissions

  • Kurppa, Mona (Helsingin yliopisto, 2020)
    Exposure to outdoor air pollution is a major environmental threat causing around 3 million premature deaths worldwide yearly. Particularly, aerosol particles are detrimental to human health. Urban areas are marked by both high population densities and degraded air quality due to high anthropogenic emissions and limited ventilation of air pollutants from the street level, making the study of urban air quality crucial. Urban air quality results from a complex interplay of meteorology, background concentrations, emissions, and chemical and physical processes of air pollutants. Yet, the lack of building-resolving neighbourhood-scale open-access numerical methods has been the bottleneck for properly solving these interactions. To narrow this gap, the main aim of my thesis is to embed the aerosol module SALSA into a large-eddy simulation (LES) model PALM to correctly simulate urban air quality. We evaluate the new PALM-SALSA model in Cambridge, UK, and Helsinki, Finland, against comprehensive aerosol particle measurements, and assess the role of different aerosol processes and boundary conditions on the pollutant concentrations in the time scale of one hour. Further, the influence of urban planning on local pollutant concentrations along boulevard-type streets is examined in real scenarios in Helsinki. The PALM-SALSA model captures well both the horizontal and vertical distribution of aerosol particle concentrations and number size distributions in an urban environment. Incorporating aerosol processes to PALM is important for correctly simulating air quality, as we show that dry deposition of particles on vegetation and other surfaces decreases number concentrations by up to 20%, whereas condensation and dissolutional growth increase aerosol mass by over 10%. Still, dispersion and emissions govern concentration fields, and thus setting the correct model boundary conditions is a determining factor. Concentration fields at street level are sensitive to the atmospheric stability and wind speed, and vertical dispersion especially to the wind direction. Furthermore, my work demonstrates how choices in urban planning can favour local air quality conditions and how particularly height variation of buildings and trees is preferential for street-level air quality and ventilation. This thesis introduces a novel, open-access model for high-resolution urban aerosol simulations, and the first LES studies on the role of urban planning on air quality and ventilation in entire neighbourhoods. Along with research purposes, the model is suited to supporting urban planning and producing data for exposure studies and monitoring network development.
  • Salonen, Markku (Helsingin yliopisto, 2020)
    The complex formation equilibria of pyridine-2-aldoxime and its methyl or amido derivatives (HL) with cobalt(II), zinc(II), and cadmium(II) ions, and the protonation and complex formation equilibria of pyridine-2,6-carboxamidoxime (H2L) with copper(II) and nickel(II) ions were studied in aqueous 0.1 M Na(Cl) solution at 25 C by potentiometric titrations with the use of glass electrode. The experimental data were analyzed with the least-squares computer program SUPERQUAD to determine the complexes formed and their stability constants. In addition, the structure of the crystallized pyridine-2,6-carboxamidoxime complex with the formula [Ni(HL)2]∙4H2O has been determined with X-ray measurements. The complexes of types Co(HL)2+ and Co(HL)22+ are mainly octahedral with a high spin d7 electron structure (t2g5eg2) and their oxidation states are stable. The deprotonated bis complexes of type Co(HL)L+ are often low spin (t2g6eg) and because of the easy loss of their only eg electron they are easily oxidized to very inert low spin cobalt(III) complexes (t2g6). Only small amounts of cobalt(III) complexes cause the very slow attainment of equilibrium often already in the pH range 2–5. Pyridine-2-carboxamidoxime and pyridine-2-aldoxime and probably also 1-(2-pyridinyl)ethanone oxime forms also tris complexes Co(HL)32+ and/or Co(HL)2L+. The complex formation of pyridine-2-aldoxime in the pH range 5–10 could be studied by using very small cobalt(II) ion concentrations. There, all the cobalt(II) form the low spin CoL2, which quantitatively displaces also the tris complex Co(HL)2L+. 6-methylpyridine-2-aldoxime forms complexes Co(HL)2+, CoL+, CoL2, Co2L2OH+, Co2L3+, and Co2L3OH, mainly in the pH range 6–10. The stabilities of the low spin CoL2, Co2L3+, and Co2L3OH and their oxidation reactions are decreased by the steric requirements of the 6-methyl groups of the ligands. Pyridine-2-acetamidoxime forms also a complex Co(H2L)3+ and pyridine-2-carboxamidoxime forms a complex Co2(HL)2H2L5+ with a positively charged ligand (H2L+). Zinc(II) and cadmium(II) ions form with 6-methylpyridine-2-aldoxime only Zn2L22+, Zn2L2OH+, and Zn2L2OH)2, and CdL+, CdL2, and Cd2L2OH+. With pyridine-2-acetamidoxime, they form only Zn(HL)2+, Zn2L2OH+, Cd(HL)2+, and CdL+. The other oximes form also Zn(HL)L+, ZnL2, Cd(HL)L+, and CdL2. Cd(HL)22+ reaches only with pyridine-2-carboxamidoxime and Zn(HL)22+ also with 1-(2-pyridinyl)- ethanone oxime measurable concentrations. Pyridine-2-carboxamidoxime forms also Zn4(L–H)2L22+ and Cd4(L–H)2L22+. The stability constants of the mono complexes M(HL)2+ increase with few exceptions in the order 6-methylpyridine-2-aldoxime < pyridine-2-acetamidoxime < pyridine-2-aldoxime < 1-(2-pyridinyl)ethanone oxime < pyridine-2-carboxamid-oxime < pyridine-2,6-dicarboxamidoxime and Cd < Zn < Co < Ni < Cu.
  • Khoramshahi, Ehsan (Helsingin yliopisto, 2020)
    Optical systems are vital parts of most modern systems such as mobile mapping systems, autonomous cars, unmanned aerial vehicles (UAV), and game consoles. Multi-camera systems (MCS) are commonly employed for precise mapping including aerial and close-range applications. In the first part of this thesis a simple and practical calibration model and a calibration scheme for multi-projective cameras (MPC) is presented. The calibration scheme is enabled by implementing a camera test field equipped with a customized coded target as FGI’s camera calibration room. The first hypothesis was that a test field is necessary to calibrate an MPC. Two commercially available MPCs with 6 and 36 cameras were successfully calibrated in FGI’s calibration room. The calibration results suggest that the proposed model is able to estimate parameters of the MPCs with high geometric accuracy, and reveals the internal structure of the MPCs. In the second part, the applicability of an MPC calibrated by the proposed approach was investigated in a mobile mapping system (MMS). The second hypothesis was that a system calibration is necessary to achieve high geometric accuracies in a multi-camera MMS. The MPC model was updated to consider mounting parameters with respect to GNSS and IMU. A system calibration scheme for an MMS was proposed. The results showed that the proposed system calibration approach was able to produce accurate results by direct georeferencing of multi-images in an MMS. Results of geometric assessments suggested that a centimeter-level accuracy is achievable by employing the proposed approach. A novel correspondence map is demonstrated for MPCs that helps to create metric panoramas. In the third part, the problem of real-time trajectory estimation of a UAV equipped with a projective camera was studied. The main objective of this part was to address the problem of real-time monocular simultaneous localization and mapping (SLAM) of a UAV. An angular framework was discussed to address the gimbal lock singular situation. The results suggest that the proposed solution is an effective and rigorous monocular SLAM for aerial cases where the object is near-planar. In the last part, the problem of tree-species classification by a UAV equipped with two hyper-spectral an RGB cameras was studied. The objective of this study was to investigate different aspects of a precise tree-species classification problem by employing state-of-art methods. A 3D convolutional neural-network (3D-CNN) and a multi-layered perceptron (MLP) were proposed and compared. Both classifiers were highly successful in their tasks, while the 3D-CNN was superior in performance. The classification result was the most accurate results published in comparison to other works.
  • Heikkinen, Liine (Helsingin yliopisto, 2020)
    Aerosol particles, which are solid or liquid particles suspended in the air reduce air quality as well as influence Earth’s radiative balance through their direct and indirect interactions with solar radiation. The sensitivity of Earth’s climate to aerosol particles has remained elusive despite a wealth of studies conducted. Some of this uncertainty arises from the highly dynamic manner the physicochemical properties of aerosol particles evolve in the atmosphere. Recent advances in mass spectrometric measurement techniques have helped to assess the aerosol chemical (trans)formation altering many climate-relevant aerosol properties such as aerosol particle size, volatility and water affinity. The scope of my thesis is the formation and evolution of organic aerosol (OA) in the boreal environment. Boreal forests emit a wide variety of volatile organic compounds (VOCs), which can form secondary organic aerosol (SOA) after oxidation. Notably, the mechanisms behind the VOC to SOA conversion is not straightforward and depends highly on the type of VOC, oxidants and evnironmental conditions. This process can therefore be sensitive to the changes projected to take place within the boreal biome along with the changing climate. Changes regarding tree species can alter the composition and relative abundances of the emitted VOCs, which can further influence boreal SOA formation. Anthropogenic emissions can also affect natural VOC to SOA conversion and further SOA processing (aging) even in the pristine regions of the boreal biome. Due to attempts in air quality improvements in several locations worldwide, many anthropogenic species have shown declining trends with potential consequences in SOA formation and aging. The studies conducted within this thesis can be divided into two categories: 1) examining the accumulated OA composition and its seasonal dynamics in the boreal forest to understand the present state of boreal OA (field studies), and 2) zooming in on the early stages of SOA formation and evolution and the potential impacts of anthropogenic emissions on them (laboratory studies). The measurements were conducted via online mass spectrometry. The results highlight the importance of aged low-volatility oxygenated OA (LV-OOA) within the boreal environment throughout the year, with highly season-dependent sources. The LV-OOA production was found to be extremely sensitive to heat waves. In the laboratory, we examined the volatilities and fates of highly oxygenated organic molecules (HOMs), which form in boreal VOC oxidation. HOMs were shown to be primarily of low volatility and therefore good candidates as SOA precursors. In the presence of nitrogen oxides, which imply anthropogenic influence, HOMs of relatively higher volatilities were formed, potentially reducing HOM condensate formation. HOM condensate has been previously shown to be labile, and fragment quickly after formation. In our studies, this reaction was boosted in the presence of acidic aerosol particles. SOA formation was influenced by aerosol acidity also by significantly enhancing the SOA yield from semi- or intermediate volatility precursors and simultaneous oligomerisation reactions. The formation of high molecular weight oligomers significantly reduced SOA volatility. However, the difference observed between the ambient LV-OOA and fresh laboratory SOA composition underlines the importance of photochemical aging needed for the formation of the highly oxidised ambient OA.
  • Lassila, Ilkka (Helsingin yliopisto, 2020)
    Deep continental drilling is a fundamental tool for obtaining detailed information about the composition, structure and physical conditions of the Earth’s crust. A drill hole allows direct access to rock under in situ conditions and retrieval of core samples that can be investigated in laboratory. In order to get reliable estimates for geophysical properties of rock samples, the seismic velocity measurements should be performed under pressure. An apparatus was built that could be used to determine ultrasonic (1 MHz) longitudinal and shear wave velocities (Vp and Vs) in rock samples under uniaxial compression that resembles conditions in the crust down to 11 km depth. Rock samples from Outokumpu deep drill hole (2516 m) were analyzed to characterize the geophysical nature of the Precambrian crustal section in Eastern Finland. Velocities varied according to the mineral composition, lithology, porosity and microcracks. The core velocities increased with increasing pressure due to microcrack closure. The results agreed with the down-core direction velocities of samples from the same core section measured under triaxial compression using a multi-anvil apparatus to some extent. The obtained geophysical parameters can be used to refine the interpretation of the seismic reflection survey data, such as the data from Finnish Reflection Experiment (FIRE) project. One of the FIRE survey lines crossed the Outokumpu area. The stress field in Fennoscandian crust consists of the weight of the overburden (26 MPa/km) and from a horizontal stress state arising from the Mid-Atlantic ridge push. The vertical stress exceeds the horizontal stresses at ~1 km depth. The crust exhibits velocity anisotropy that is strongly related to foliation and, in the case of retrieved core samples, to oriented microcracks. Because of seismic velocity anisotropy and the crustal stress-field, velocities should be measured in three dimensions under controlled tri-axial pressure, which is difficult with uniaxial apparatus. A multi-anvil apparatus was built to measure Vp and Vs (0° and 90° polarization) in three orthogonal directions of cube shaped samples under triaxial compression. Samples from the FIRE survey line were measured with the apparatus. Ultrasonic velocity measurements were also used to determine the porosity of custom-made ceramic samples. At 4-33% porosity the velocity decreased linearly with increasing porosity for both Vp and Vs. Material crystallinity is often a required property of the intermediate or end product in pharmaceutical manufacturing. Material can exhibit more than one crystal structure i.e. polymorph. While chemically identical the different lattice structure of an active pharmaceutical ingredient (API) results in different physicochemical properties. Polymorphism can significantly affect properties such as bioavailability, solubility and dissolution rate. These properties are also affected by the particle size, which is highlighted in case of nanoparticles. Besides using ultrasound to measure material properties, ultrasound was used in semi-batch crystallizer to initiate nucleation and control polymorphism and size of L-glutamic acid. Ultrasound-initiated nucleation produced pure (> 99.5 wt%) α-polymorph in controlled supersaturation conditions and reduced the particle size.
  • Heikinheimo, Vuokko (Helsingin yliopisto, 2020)
    In this thesis I have investigated how user-generated data can be applied to studying human-nature interactions on different spatial and temporal scales. User-generated geographic information refers to spatial data sets generated by and about people, such as social media data, sports tracking data, mobile phone data and participatory geographic information. Users of various digital platforms and mobile devices generate considerable amounts of data about their observations, activities and preferences in different environments. These data can potentially be used to fill information gaps about spatial and temporal patterns of human activities in nature. The aim with this thesis is to gain improved understanding of human-nature interactions based on user-generated geographic information with a focus on social media data from national parks and green spaces. The main objectives are to gain 1) a novel understanding about user-generated data, and 2) insights about human activities in nature on different scales through these questions: Where and when are people visiting nature? What are people doing and valuing in nature? Which users have shared their data from national parks and green spaces? This thesis consists of four articles and an introductory section. Article I provides an overview of social media data sources and analysis methods relevant for nature conservation, and highlights that most of the analytical opportunities are still unexplored in the growing body of literature using social media data in conservation science. Article II compares social media data with national park visitor survey and finds similar trends in both data sources regarding popular activities and visited places. Article III compares methods for detecting national park visitors’ place of residence from geotagged social media and assesses biases that affect the analysis. Article IV compares the use of social media data, sports application data, mobile phone data and participatory geographic information for understanding the use of urban green spaces and suggests that combining information from several sources provides a more comprehensive understanding of green space use and preferences. Overall, user-generated geographic information offers valuable insights about where, when and how people use and value nature, especially from areas that are otherwise difficult to monitor. There are several issues related to data access, bias and privacy in these data. Despite evident limitations, these data contribute to a better understanding of human activities in nature and complement traditional data sources with new and dynamic perspectives. In some areas, user-generated data might be the best available information about human activities. Data comparisons from national parks and green areas presented in this thesis also feed into other fields of research using social media and other user-generated data for studying human spatial behaviour.
  • Remes, Jere (Helsingin yliopisto, 2020)
    Quantum Chromodynamics (QCD) is the quantum field theory describing strong nuclear interactions. Due to the titular strong nature of these interactions, obtaining reliable predictions from the theory has proven challenging in many physically interesting regions of the phase diagram. The most well-established current framework for handling strongly coupled, nonperturbative systems is that of lattice simulations. Even this framework has its weaknesses when applied to QCD, however, such as simulating systems where real-time dynamics are relevant or that have non-zero chemical potential. Such cases are found in e.g. the early-time dynamics of heavy-ion collisions and inside neutron stars, respectively. These nonperturbative systems provide us with an ideal testing ground for new methods such as holography. Holography is an umbrella term for various dualities which connect a quantum field theory with a higher-dimensional theory of quantum gravity. One general property of these dualities is that they map operators in strongly coupled field theories into fields in weakly coupled classical gravity. It therefore seems natural to apply the methods provided by these dualities to the study of strong coupled real-world theories such as QCD. However, there is no known holographic dual for QCD yet, and we must resort to some modeling if we wish to compute predictions via holographic methods. In this thesis, we apply holographic models of QCD -- namely Improved Holographic QCD and its extension called V-QCD -- in the study of both the thermalization of hot quark-gluon plasma produced in heavy-ion collisions and the structure and astrophysical properties of cold, dense matter in neutron stars. We also provide an introduction to the different facets concerning these applications from the motivation in QCD and the challenges the QCD phase diagram provides to current computational methods, to holography, heavy-ion collision phenomenology and neutron star observations.
  • Korkiakoski, Mika (Helsingin yliopisto, 2020)
    Drained peatlands are a challenge to the climate change mitigation, due to acting as sources of carbon and greenhouse gases to the atmosphere. However, different management practices could be used to reduce these emissions. In this thesis, the objective was to quantify the changes in water table level (WTL), evapotranspiration (ET) and greenhouse gas (GHG) fluxes for the first few years following clearcutting and partial harvesting a nutrient-rich peatland forest. The experimental forest was divided to partial harvest, clear-cut and control subsites, where WTL was monitored and direct flux measurements were made with the eddy covariance (EC), and manual and automatic soil chamber methods. Before clearcutting, the subsite was a small CO2 and CH4 sink, but N2O emissions were small. After clearcutting, WTL rose by 24 cm due to a 45% decrease in ET. The loss of photosynthesising biomass and addition of respiring logging residues turned the clear-cut subsite from CO2 sink into a large CO2 source for the next few years. Forest floor N2O fluxes increased significantly, possibly due to residues releasing reactive nitrogen, hence promoting N2O production. Also, soil compression and WTL rise might have enhanced N2O production through increased denitrification. The soil turned from CH4 sink into a small source as a result of thinning of oxic peat layer, which decreased CH4 oxidation. The partially harvested subsite was a small CO2 source before the partial harvest, meaning more carbon was lost through peat decomposition than was taken up by growing trees. Forest floor was a small CH4 sink and N2O source. After partial harvest, WTL rose by 12 cm and ET decreased by 17% compared to the control site. Also, CO2 emissions increased. However, compared to the clear-cut site, CO2 emissions were significantly smaller at the partial harvest site. No considerable changes in CH4 and N2O fluxes were observed after partial harvest. The difference in CO2 emissions between the harvest treatments can be explained with remaining tree stand, which kept ET higher, WTL lower and acted as CO2 sink. Also, the amount of decomposing logging residues was smaller after partial harvesting than after clearcutting.
  • Oljemark, Fredrik (Helsingin yliopisto, 2020)
    The understanding of the strong interaction with low-momentum transfer is of primary importance for our understanding of the behaviour of nuclear matter. Suitable processes to study such low-momentum transfers are soft diffractive high energy physics processes. In this thesis, soft Single Diffraction (SD) in proton-proton scattering was studied at 7 TeV centre-of-mass energy with the TOTEM experiment at CERN's Large Hadron Collider (LHC), in Geneva, Switzerland. SD is a significant part of the total inelastic proton-proton scattering but despite that not so well known, nor much studied. SD events are characterized by an intact proton opposite a diffractive system with a large rapidity region without primary particles, a so-called rapidity gap, in between. In these studies, the out-going intact protons are measured at 5-30 mm from the out-going beam using the TOTEM Roman Pots (RP), movable beam-insertion detectors located about 220 m from the collision point. The proton track in the RP is used to reconstruct the scattering angle and proton longitudinal momentum loss. The diffractive system and the rapidity gap are both tagged and measured using the TOTEM T1 and T2 charged particle telescopes. The data used for the studies was taken in a special run at the LHC in 2011 with β∗ = 90 m optics that optimized the proton acceptance for low scattering angles at any proton longitudinal momentum loss value below 20%. Results are presented for the total SD cross section and differential cross section versus |t| – the absolute momentum transfer squared – in four ranges of the proton longitudinal momentum loss ξ, inferred from the size of the rapidity gap measured by T1 and T2. The data are unfolded with the Pythia and EPOS event generators, and the final results are selected to be the average of these two estimates. The results are compared to expectations from various event generators as well as earlier SD measurements at the LHC. The total SD cross section obtained is 11.10 ± 1.66 mb for the range 2.7 ∗ 10−7 < ξ < 20 %. Compared to earlier studies, these studies cover a significantly larger ξ range. They also show, for the first time at the LHC, the expected dependence of the exponential slope of the |t| distribution as function of ξ, i.e. that the |t| distribution becomes less steep with increasing ξ. The results provide relevant information regarding the proton structure, as well as valuable input to the modelling of cosmic-ray air showers and inelastic collisions.
  • Lehmonen, Lauri (Helsingin yliopisto, 2020)
    Several cardiac diseases affect myocardial function, with local myocardial deformation receiving much attention over the past few years. This work aimed to examine whether globally and locally analyzed quantitative cardiovascular magnetic resonance imaging-derived strain, rotation, and torsion of the heart would bring additional value and deeper understanding to myocardial mechanics in specified cardiovascular disorders. Patients with rheumatoid arthritis, tetralogy of Fallot, hereditary gelsolin amyloidosis, and hypertrophic cardiomyopathy, together with healthy controls, were investigated. A non-rigid registration-based software solution for myocardial tagging and feature tracking analysis was used for the quantification of left ventricular and right ventricular global and regional strain in different directions. Quantitative motion analysis showed that early treatment of rheumatoid arthritis was useful in retaining the diastolic function of the left ventricle. In adolescents with tetralogy of Fallot, right ventricular circumferential strain was increased relative to healthy controls. Tetralogy of Fallot subjects with increased pulmonary regurgitation had higher right ventricular longitudinal strain than subjects with less pulmonary regurgitation; this has been considered a compensation mechanism. Hereditary gelsolin amyloidosis showed local myocardial changes focused on the basal plane of the left ventricle and differing from the more common light-chain cardiac amyloidosis. The non-rigid registration-based technique was compared with the harmonic phase-based method with Gabor filtering in the analysis of myocardial tagging-derived rotation and torsion in subjects with hypertrophic cardiomyopathy. The absolute values obtained with the two software methods were significantly different, however, neither software showed significant differences in patients with hypertrophic cardiomyopathy relative to healthy controls. Motion parameters of both ventricles were associated with other quantitative cardiac magnetic resonance imaging parameters, such as volumetric measurements and T1 relaxation times, in the studies of this thesis. Tagging and feature tracking-derived motion parameters showed significant findings in local myocardial motion in rheumatoid arthritis, tetralogy of Fallot,and hereditary gelsolin amyloidosis. Software-based reference values are required when comparing motion parameters between study subjects. Currently, no standardization for measuring different deformation parameters, such as strain, rotation, or torsion exists, and several software solutions are available for analyzing these parameters. Variability between different software solutions and individual observers should be recognized.
  • Aikonen, Santeri (Helsingin yliopisto, 2020)
    Reaction mechanisms play an integral part in understanding chemical phenomena. Chemists use their knowledge of reaction mechanisms both when formulating research questions and when carrying out experiments in the fume hood or in silico. Accurate understanding of the reaction mechanism provides a pre-requisite for optimisation of reaction conditions or development of new catalysts. Reaction mechanisms are studied with experimental, e.g., in situ reaction monitoring or isotopic labelling, and computational methods as the mechanistic findings complement each other. This work combined experimental, kinetic analysis and computational methods to elucidate reaction mechanisms in homogeneous gold-catalytic activations of alkynes, photoreduction reactions of heteroaryls and oxidative coupling reactions of (hetero)aryls. Computational methods are in a central role for mechanistic explorations, and a part of this thesis is dedicated for the review of the central theory of these methods. Central mechanistic aspects of the studied reactions are also presented. The experimental and computational results presented in this thesis have been published in three peer-reviewed publications; and two manuscripts are under preparation for submission. In Publication I, we discovered the reaction mechanism of gold(I)-catalysed intermolecular 1,3-O-transposition of ynones using kinetic analysis and experimental and computational methods. We then optimised the conditions with aldehyde additives and introduced a prediction model based on the aldehydes’ nucleophilicities. In Publication II, we studied the proton and electron transfer steps in the Ru(bpy)3Cl2 and ascorbic acid-mediated photoreduction of N-heterocyclic nitroaryls to N-heterocyclic amines. From computational thermodynamics and experimental kinetics, we concluded that the first reduction is a multisite proton-coupled electron transfer while the last reduction is a stepwise protonation and electron transfer. In Publications III and IV, we studied the oxidative dehydrogenative C-C coupling mechanisms, i.e., radical cation and arenium cation, in heterogeneous carbocatalysis. We concluded that both mechanisms are kinetically feasible in the reaction conditions and the operative mechanism depends on the proton and electron affinities of the substrate and the catalyst. In Publication V, we developed hydrogen bond donor tethered ligands for gold(I)-catalysis. The side-arms activated the gold-chloride bond with the help of hydrogen bond donating substrates or additives, as well as energetically stabilised reaction intermediates and transition states. The developed catalysts proved to be superior compared to commercial gold(I)-catalysts in oxazoline cycloisomerisation. In all Publications, the combination of experimental and computational mechanistic explorations offered insight into the reactions that would have otherwise been difficult to attain. The experimental and computational methods were used to optimise reaction conditions and predict reactivity based on simple chemical descriptors, such as acidity, redox potential and nucleophilicity.
  • Lönnrot, Satu (Helsingin yliopisto, 2020)
    During recent years the emerging threat caused by climate change has directed energy production towards carbon-free technologies including nuclear power with a stable energy production. However, the nuclear energy production generates radioactive fission and activation products that are posing a threat to human health and environment without proper handling of nuclear waste streams. Among the radionuclides, activated antimony isotopes: 122Sb, 124Sb and 125Sb, and a high fission yield 99Tc are of special interest due to their high activities, anionic species and redox chemistry. Zirconium dioxide (ZrO2) is a ceramic material with a high chemical and physical resistance. Therefore, ZrO2 is highly suitable for a treatment of radioactive waste solutions in which it might experience elevated temperatures, high radiation, presence of corrosive chemicals and fast changes in the conditions. Due to the different crystal structures and morphologies of ZrO2 and its suitability for doping, the material can be applied to separation of different metal ions. The materials selectivity and other separation properties can be tuned by modifying the structure and chemical composition of ZrO2. In this thesis, the ZrO2 is used in different forms to remediate Sb(V) and Tc(VII). The main purpose of this thesis was to develop electroblown ZrO2 submicron fibers for the separation. At first, the effect of morphology on the Sb(V) uptake was studied by comparing fibrous and microparticulate zirconia with each other and special focus was targeted to adsorption kinetics and pressure development during the column operation. Secondly, the influence of ZrO2 crystal structure (amorphous, tetragonal, monoclinic) on the Sb(V) adsorption was investigated. Finally, the tetragonal ZrO2 fibers were functionalized with Sb doping to efficiently and selectively remove Tc(VII) from aqueous solutions. The electroblowing and calcination synthesis produced separate, cylindrical and long fibers with a diameter of 300 – 800 nm. In the Sb(V) adsorption experiments, the ZrO2 showed good adsorption performance by retaining Sb(V) on a broad pH range and having fast adsorption kinetics. Compared to microsized zirconia granules, the fibers maintained lower pressures during column operation indicating improved utility of nano- and microsized materials that would allow fast feeding rates of purifiable solution through the column. In addition, the tetragonal ZrO2 crystal structure was found to be beneficial for Sb(V) adsorption as the tetragonal fibers had higher adsorption capacity than the amorphous or monoclinic ZrO2 fibers. The superiority of the tetragonal ZrO2 fibers was expected to originate from the largest specific surface area generating higher number of adsorption sites, and from a higher adsorption energy inducing more stable surface complexes. According to conducted experiments, an inner-sphere complexation was assumed to be the dominating separation mechanism but Sb(V) was also partially retained by an outer-sphere complexation or ligand exchange. Since the undoped ZrO2 fibers showed only poor TcO4– separation, the material was functionalized with the Sb doping. The Sb doping improved the TcO4– separation as several orders of magnitude higher Kd values were obtained with the Sb-doped ZrO2 fibers than with the undoped ZrO2 fibers. The superior separation probably originated from the reduction of Tc(VII) to Tc(IV) by the Sb(III) dopant, and then Tc(IV) was retained on the ZrO2 surface. The material showed higher selectivity towards TcO4– than many other published materials as it was not interfered with even by stereostructurally similar ClO4–. In addition, the Sb-doped ZrO2 fibers showed only limited ReO4– uptake as these anions were not reduced. Instead, they were assumed to be bound on the zirconia surface with the electrostatic interaction mechanism that was also the probable mechanism for TcO4– adsorption on the undoped ZrO2 fibers. Overall, the electroblown ZrO2 fibers demonstrated good radionuclide separation performance that can be addressed to separation of Sb(V) and Tc(VII) and potentially some other elements. Furthermore, the simple electroblowing synthesis can be applied to the synthesis of other inorganic fibers extending the separation potential of the fibers to an even higher number of target compounds.
  • Virta, Leena (Helsingin yliopisto, 2020)
    During the ongoing rapid environmental change, different aspects of biodiversity and its effects on ecosystem functioning need to be resolved. A lot has already been learned regarding the value of biodiversity, but due to the complexity of natural environments many aspects are still unresolved, especially about the patterns and effects of microorganismal diversity in marine and brackish environments. This is surprising, given that microorganisms play key roles in many ecosystem functions and the marine microorganisms are estimated to, e.g., provide the majority of Earth’s oxygen. To facilitate better understanding, studies conducted along large gradients and considering the functional diversity of communities can be useful. Large gradients provide insights into the variation of ecological patterns relative to the environment and can indicate the consequences of environmental change on community responses, and the functional diversity may describe the community characteristics and diversity-ecosystem functioning relationships more effectively than taxonomic diversity and allow the generalizations of results between organisms and ecosystems to be made. In this thesis, biodiversity patterns of benthic diatoms, a highly diverse and productive microorganismal group in all aquatic systems, were resolved along different environmental, spatial and temporal gradients in the coastal ecosystems of the Baltic Sea. Being one of the world’s largest brackish water ecosystems with a naturally strong gradient of salinity and climate and with a unique mixture of marine and freshwater species, the Baltic Sea provides an ideal platform for biodiversity research. Biodiversity patterns resolved here included analyzing the effects of benthic diatom diversity on ecosystem productivity, investigating spatial and temporal beta diversity patterns, i.e. the change in community composition between sites or sampling occasions, and examining the effects of environment on the distribution and diversity of diatoms. All studies were conducted as field studies to increase knowledge on real-world processes. The results revealed some significant new insights and showed that the diversity, especially functional diversity, of benthic diatoms may set the lower boundary for ecosystem productivity. Thus, productivity could be high even when the diatom diversity was low, but high diatom diversity seemed to consistently support high productivity. This positive relationship may be due to several reasons, such as more complete resource use or the facilitative effect in diverse communities, or complex ecological interactions. However, the diversity of diatoms varied substantially among different habitats, highlighting the need to consider environmental heterogeneity and large environmental gradients in biodiversity research. Spatial beta diversity studies conducted at different spatial scales indicated a general pattern: across steep environmental gradients, the taxonomic beta diversity was consistently high while the functional beta diversity remained considerably lower. This suggests that the ecosystem requirements for the functional characteristics of microphytobenthic organisms are highly similar in different environments, and that diatoms are able to meet these requirements in variable environments, which may indicate an insurance effect against environmental change. However, simulated species loss of communities significantly increased the functional beta diversity, suggesting that the deterioration of diversity may decrease resilience, and thus emphasizing the importance of biodiversity for the stable functioning of benthic ecosystems. Despite some similarities in the environmental drivers of diatom communities in different environments, environmental variables controlling the communities varied between and within gradients. Thus, the effect of environment on communities seems to be context-dependent and variable between regions, which emphasizes the need for large-gradient studies and the consideration of region-specific differences in, e.g., environmental management and conservation efforts. The seasonal and inter-annual variation in the composition and diversity of communities was investigated along a temporal gradient of two years. The taxonomic and functional composition of communities changed significantly between seasons and years, while diversity remained fairly stable. This refers to either an ample seed bank, i.e. locally occurring resting stages of species, or a large regional species pool and effective dispersal of species, which rescue the populations. However, diversity decreased during an exceptionally warm winter with a short ice-cover duration, which may suggest that climate warming affects the diversity of benthic communities. To conclude, this thesis has increased the knowledge on the diversity and importance of benthic diatoms in complex real-world environments. Some of the diversity patterns were general and non-dependent of spatial scale, whereas others were highly variable between regions and gradients. The results emphasize the need to consider the effect of benthic diatoms when modelling and designing the management of coastal areas, and indicate the usefulness of studies with environmentally and spatially large gradients for the understanding of diversity patterns in natural ecosystems.
  • Arsenovich, Tatyana (Helsingin yliopisto, 2020)
    The Large Hadron Collider (LHC) accelerator at CERN will be updated into High-Luminosity Large Hadron Collider (HL-LHC) between 2025-2027, and as a result, all of the LHC experiments have to be upgraded to meet the goals set for high-quality physics data taking. Also the Compact Muon Solenoid (CMS) Tracker will undergo several planned upgrades aimed to improve the characteristics of its detectors without negative impact on physics potential. In the HL-LHC, the level of radiation will increase significantly, thus, the radiation hardness of the detectors should be improved while at the same time also improving their capability of handling the higher amounts of data. The candidate materials and technologies for the development of the detectors need to be reviewed taking the requirements of the HL-LHC data taking into account. The quality assurance of these detectors is of utmost importance to identify possible failures as soon as possible in the design phase and later during the production of the devices. The quality assurance methods should be verified to be able to reliably provide the needed characterisation parameters. In this thesis, the processing of the samples and their characterisation are described from the reliability point of view. Descriptions of processing steps, theoretical models and measurements methods are accompanied by the discussion of possible failures and suggestions how to prevent them. Special attention is put on the impact of the so-called human factor and the importance of knowledge transfer. The purpose of this work is to study the long-term stability of silicon detectors with Al2O3 thin films grown with the Atomic Layer Deposition (ALD) method and implemented as an insulation and surface passivation layer. The test samples for these studies were processed during 2011-2015 in the cleanroom facilities of the Micronova centre for Micro and Nanotechnology by Dr. E. Tuovinen. Electrical characterisation and characteristic measurements with source were performed in 2014-2018 in the Detector laboratory and cleanroom facilities of Helsinki Institute of Physics (HIP). In addition, Highly Accelerated Temperature and Humidity Stress Tests (HAST) like those performed in the HIP Detector laboratory facilities is suggested as a new approach for studies of the long-term stability of the detectors. Electrical characterisation demonstrated good long-term stability of capacitance, depletion voltage and leakage current characteristics of the test samples with Al2O3 insulation and surface passivation layer. The result of the characterisation demonstrates that samples with surface passivation are able to withstand higher bias voltage than samples without such passivation. Characteristic measurements with a Cs-137 source confirmed that the surface passivation with Al2O3 does not affect the general detector performance. Characterisation of single pixel sensors coated with the Al2O3 after the flip-chip bonding demonstrated that the additional ALD run is not harmful for the structure of the detector and does not affect its behaviour. Thus, ALD-deposited alumina coating can be recommended as a material for additional protection of silicon detector structures.
  • Annala, Eemeli (Helsingin yliopisto, 2020)
    The first theoretical attempts to study neutron stars — the immensely dense remnants of massive stars — were conducted in the 1930s, but it took nearly 40 years for the first one to be detected. Ever since, these fascinating objects have been the subject of significant interest; both nuclear and particle physicists and astronomers have tried to understand their micro- and macro-scale properties. Regardless, the composition of neutron-star cores has, to large extent, remained unknown. This is somewhat surprising because the underlying microscopic theory — quantum chromodynamics — has been available for several decades. Because it is impossible to describe the structure of neutron stars using current ab initio techniques, other kinds of approaches need to be exploited. In this thesis, state-of-the-art nuclear and particle theory calculations were utilized to restrict the dense-matter equation of state at low and high densities, respectively. Between these two limits, there exists a region, where the equation of state needs to be approximated by employing various interpolation tools. Our analysis has revealed that both the mass-radius curve of neutron stars and the underlying equation of state can be efficiently constrained by making use of the latest astronomical observations — such as the tidal-deformability measurement from the gravitational-wave event GW170817. We have also shown that there exists convincing evidence that the most massive neutron stars have deconfined quark matter in their cores assuming that the equation of state is not very extreme. In addition, we have taken some first steps towards the realistic implementation of the gauge/gravity duality in neutron-star physics. This method allows one to investigate strongly coupled quantum systems using simpler gravity-based setups. This approach has already led to several promising results in many fields, from condensed matter physics to the study of quark-gluon plasma. It is, therefore, a worthy candidate to become a fruitful framework to examine neutron-star physics, complementing the current nuclear and particle theory methods. It is expected that the improvement of theoretical calculations together with new, more precise observations will likely resolve the equation of state within a decade or two. Moreover, this progress will eventually disclose, whether quark matter resides inside the heaviest neutron stars in existence. The development of holographic tools may also open up new and powerful ways to study matter at its most extreme densities.
  • Iashin, Vladimir (2020)
    C-H activation is a challenging problem in modern organic chemistry. Direct C–H borylation is one of the widely growing subclasses of C–H activation. As a rule, these reactions are performed by transition metal catalysis. However, recently a metal-free approach towards C-B boron bond formation has been growing intensively. Usually, metal-free borylations are performed with a boron compound as a Lewis acid component and a Lewis base as a proton acceptor, which may or may not be preorganized for this transformation. Usually, such reactions require the use of boranes with high Lewis acidity such as B(C6F5)3, BCl3, BBr3, etc. At the same time, the chemistry of the less acidic boron trifluoride, BF3, as a borylating species is unprecedented. This work is aimed at uncovering the reactivity of BF3 towards C-H borylation of Csp–H and Csp2–H bonds. In this respect, the following factors were studied in the work: • Formation of BF3 adducts with various amines and their reactivity in Csp2–H and Csp–H borylation reactions • Scope of borylation: influence of the substrates’ electronic structure and various functional groups’ compatibility • Controlling the formation of mono-, bis-, tris-, and tetrakisorganoborates from BF3, amine, and Rsp–H/Rsp2–H substrate. • Reactivity difference between BF3·SMe2, BF3·OEt2, and BF3-1,2,2,6,6-pentamethylpiperidine (BF3·PMP) with respect to alkyne borylation Because organoboranes are often unstable reactive species, they were converted to fluoroborates by tetramethylammonium fluoride. In this respect, competing reactions of protodeborylation and fluorination of organofluoroboranes were studied. The literature review consists of two parts: metal-free borylation of triple bonds and double bonds. For triple bonds, the review is preferably limited to terminal acetylenes because internal alkynes cannot undergo Csp–H activation. The influence of each component of a Lewis pair as well as its structure’s selectivity for C–H borylation, 1,2-addition, and carboboration is discussed. The second part uncovers the topic of C-H borylation of Csp2–H bonds. It includes both concerted borylations and borylations by reactive borenium cations. There is a special accent on the chemistry of haloboranes. In order to limit the size of the review, the use of hydroboranes for C–H activation is reviewed least in this book.
  • Kyllönen, Katriina (Helsingin yliopisto, 2020)
    Aerosols are well known to have effects on climate and human health. The chemical composition of aerosols in particular has a profound effect on the latter. Many trace elements (e.g. cadmium, lead and arsenic) found in the particulates as well as mercury (existing mostly in the gaseous form) are considered toxic for humans while deposition of these elements poses risks to the ecosystems. Due to emission abatement strategies, emissions of trace elements have significantly reduced in the recent decades. The overall objective of this thesis was to gain knowledge on the different sources as well as the temporal and spatial changes of atmospheric trace elements in Finland. The thesis was focused on the priority trace element pollutants mercury, arsenic, cadmium, nickel and lead. Also, other elements of interest were studied (aluminium, chromium, cobalt, copper, iron, manganese, vanadium, and zinc). Gaseous, particulate and deposition forms of the elements were investigated. The work was concentrated in background areas far away from possible anthropogenic sources; however, urban and industrial sites were also surveyed. The measurement techniques were partially developed or further validated in this thesis, and partially we utilised measurements conducted as a part of international measurement programmes. Sources of trace elements were studied with source apportionment method using positive matrix factorisation (PMF) and enrichment factors. Enrichment factors were used to characterize the source of a pollutant between natural and anthropogenic, and this grouped the elements from mainly crustal (Al, Fe) to highly anthropogenic origin (As, Cd, Pb, Zn) and others in between. PMF produced a more precise analysis of sources for Pallas, in which trace elements were associated with soil, sea emissions, and various long-range transported sources e.g. copper and nickel smelters in Kola Peninsula, Russia. In addition, magnitude of mercury soil and wetland emissions was investigated at one background site with the chamber technique. The air-terrestrial surface exchange measurements of elemental mercury showed that the soil emissions were found similar to depositional fluxes at the site (but opposite) and larger than the ones observed at wetland. For most trace elements, a clear south-to-north decreasing gradient in both atmospheric concentrations and deposition was observed due to minor local sources and longer distance to the large European source areas in the north than in the south. Additionally, the differences in the length of the snow-cover period have an effect on resuspension of some of the elements. For several elements both in particulate matter (PM) and deposition, statistically significant decreasing trends up to 80 % were detected since the 1990s. For gaseous mercury, no statistically significant trends were found. No statistically significant increasing trends were observed for PM, however, at two sites increases in deposition of single elements were detected.
  • Virtanen, Elina (Helsingin yliopisto, 2020)
    Marine ecosystems are degrading around the world at an unprecedented rate. Loss of biodiversity, population declines, invasion of non-indigenous species, and change in community composition are apparent in all marine ecosystems. Various policies at multiple management levels address these challenges with specific targets for good ecological and environmental status of marine areas. While various policies, directives and strategies are applicable at global and regional levels, threats facing marine ecosystems in coastal areas are more localized. Thus, to achieve effective results, conservation and management actions should be designed and addressed locally, and carefully targeted to maximize cost-efficiency and benefits for the marine ecosystem. In this thesis, four case studies are developed which demonstrate how spatially explicit analyses can support seascape conservation, sustainable use of marine areas, as well as effective management actions: (1) locate key areas for conservation, (2) pinpoint areas for effective nutrient abatement, (3) identify locations for marine mineral extraction, and (4) estimate potential future changes in key communities with the projected declines in marine environment. This thesis aims to show how extensive data combined with appropriate spatial analysis paths together with cross-disciplinary marine science can support seascape conservation and ecosystem-based marine management. The role of management in sustaining marine biodiversity is investigated and the applicability of methods developed in terrestrial realm to marine environments is evaluated. The case studies are located in the northern Baltic Sea, where multiple stressors threaten marine biodiversity. The work relies on extensive species inventory data from 140,000 underwater sites, collected by the Finnish Inventory Programme for the Underwater Marine Environment (VELMU). Statistical modelling was used in case studies (1) and (4) to explain the distribution of species, and further in case studies (2) and (3) in describing hypoxia probabilities and the occurrence of ferromanganese concretions, respectively. Further, key areas for conservation were identified with spatial prioritization in case study (1). Based on the results, current marine protected areas (MPAs) leave almost three-quarters of ecologically important species occurrence areas unprotected. This highlights the need to further develop current MPA network, and the role of spatial planning in guiding the allocation of marine areas to human activities. Knowledge of unprotected key areas can be further utilized to promote private seascape conservation and sustainable use of marine areas. In case study (2), areas naturally prone to hypoxia development were identified with spatial analyses, borrowing concepts and methodologies from landscape ecology. The approach developed can be used to optimally target nutrient abatement measures to where they are most likely to be efficient, as well as explain why some areas are more or less immune to nutrient abatement actions already taken. Case study (4) further emphasizes that some areas would benefit more from nutrient abatement measures than others. Case study (3) demonstrated that marine minerals, namely ferromanganese concretions, are more widespread than previously anticipated. As concretions hold high quantities of minerals targeted by the emerging seabed mining industry, there may be economic opportunities for such extraction activities to take place also in the Baltic Sea. Results of the case studies (1) and (3) can guide detrimental mining activities to ecologically less valuable areas, where abundant concretions can be found. Spatially explicit analyses described in case studies (1)–(4) can provide valuable support for seascape conservation and ecosystem-based management and can give further guidance for sustainable use of marine areas. Finally, efficient management of marine areas requires the integration of local management actions into wider policy processes. Ecosystem-based marine spatial planning needs to adopt place-based management strategies and decisions that are actionable at various spatial scales and can be implemented locally.
  • Anttila, Pia (Helsingin yliopisto, 2020)
    In this thesis, long-term, multicomponent, high-resolution (time and accuracy) air quality monitoring data from about 400 sites across Finland since 1994 are integrated into a single unified and compact view to demonstrate past air quality development and to assess the reasons behind the development at the national level. This thesis demonstrates that internationally launched and nationally implemented regulatory controls have had an important role in improving air quality in Finland. The pollutants subject to long-term ambitious international abatement strategies (like SO2 and persistent organic pollutants) have decreased the most. Also, NOx emission control has been successful, but urban roadside NO2 concentrations have not decreased as expected. The increase in diesel cars (and their potentially high primary NO2 emissions) may have been one factor in slowing down the decline of concentrations. However, the development of emission reduction technologies together with the improved type approval test procedures have resulted in a reduction in the significance of primary NO2 emissions in Europe. In Finland, our relatively old car fleet and the increased import of old diesel cars cause uncertainty for future development. Due to the use of studded tyres and manifested as elevated concentrations of PM10, springtime street dust is a local air pollution problem. This thesis suggests that local abatement measures (e.g., reducing traffic, changes in the car fleet, road maintenance activities) have been moving in the right direction, and the springtime street dust levels have been reduced. Although air quality standards are not exceeded today, street dust remains a persistent flaw in our otherwise good air quality. In Finland, the ozone peak levels have been declining since 2006. Similar development has been detected in Europe and North America, and it is related to decreasing anthropogenic precursor emissions of NOx and VOCs. For Finland, high background concentrations are more problematic, and reducing them would require international and even hemispheric cooperation. The available long-term background data of PAH concentrations suggest that no widespread decrease in concentrations has occurred. This is not necessarily surprising as the major global sources are small-scale solid fuel combustion and wildfires. Efforts to reduce these emissions have been relatively limited or non-existent so far.

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