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  • Franti, Lasse (Helsingin yliopisto, 2015)
    The gauge/gravity duality connects the dynamics of gravity theories in the bulk with the dynamics of field theories on the boundary. In this thesis we introduce two thermalization scenarios and investigate them using a suitable holographic description. We will first study the thermalization of equal-time correlators and entanglement entropy in a hyperscaling violating AdS-Lifshitz-Vaidya metric. This work verifies the agreement between numerical procedures and preceding analytical predictions and generalises the previous studies of thermalization in this kind of situations. In the latter part we will use the duality to describe the quark-qluon plasma created in heavy ion collisions. The anisotropic plasma is modelled by introducing anisotropies into the source on the gravity side and letting them evolve according to the equations of motion. The boundary dynamics is extracted by finding the boundary stress-energy tensor. The results agree with the conventional models. The situations considered here are rather simple but this work demonstrates the applicability of holography in the anisotropic case.
  • Kangas, Kaisa (Helsingin yliopisto, 2015)
    The starting point for this dissertation is whether the concept of Zariski geometry, introduced by Hrushovski and Zilber, could be generalized to the context of non-elementary classes. This leads to the axiomatization of Zariski-like structures. As our main result, we prove that if the canonical pregeometry of a Zariski-like structure is non locally modular, then the structure interprets either an algebraically closed field or a non-classical group. This is a counterpart to the result by Hrushovski and Zilber which states that an algebraically closed field can be found in a non locally modular Zariski geometry. It demonstrates that the concept of a Zariski-like structure captures one of the most essential features of a Zariski geometry. Finally, we give a non-trivial example by showing that the cover of the multiplicative group of an algebraically closed field of characteristic zero is Zariski-like. We define a Zariski-like structure as a quasiminimal pregeometry structure that has certain properties. Instead of assuming underlying topologies, we formulate the axioms for a countable collection C of Galois definable sets that have some of the properties of irreducible closed sets from the Zariski geometry context. Quasiminimal classes are abstract elementary classes (AECs) that arise from a quasiminimal pregeometry structure. They are uncountably categorical, and have both the amalgamation property (AP) and the joint embedding property (JEP), and thus also a model homogeneous universal monster model, which we denote by M. To adapt Hrushovski's and Zilber's proof to our setting, we first generalize Hrushovski's Group Configuration Theorem to the context of quasiminimal classes. For this, we develop an independence calculus that has all the usual properties of non-forking and works in our context. We then prove the group configuration theorem and apply it to find a 1-dimensional group, assuming that the canonical pregeometry obtained from the bounded closure operator is non-trivial. A field can be found under the further assumptions that M does not interpret a non-classical group and the canonical pregeometry is non locally modular. Finally, we show that the cover of the multiplicative group of an algebraically closed field, studied by e.g. Boris Zilber and Lucy Burton, provides a non-trivial example of a Zariski-like structure. Burton obtained a topology on the cover by taking sets definable by positive, quantifier-free first order formulae as the basic closed sets. This is called the PQF-topology, and the sets that are closed with respect to it are called the PQF-closed sets. We show that the cover becomes Zariski-like after adding names for a countable number of elements to the language. The axioms for a Zariski-like structure are then satisfied if the collection C is taken to consist of the PQF-closed sets that are definable over the empty set.
  • Leino, Aleksi (Helsingin yliopisto, 2015)
    Ions in the keV energy range are regularly used in the semiconductor industry for device fabrication. Irradiation with ions of higher energies can also induce favorable structural changes in the irradiated samples. Among these, irradiation effects of the so-called swift heavy ions (SHIs, heavy ions with specific energies in the 1 MeV / amu range) in electrically insulating materials are particularly interesting. Despite the wide range of existing applications (filters, printed circuit boards and geological dating) and application potential (fuel cells, cell mimicking membranes) of SHI irradiation, the mechanisms by which SHIs interact with insulators are still under debate. Modelling of SHIs is a very challenging task as, contrary to ions with lower energies, they mostly interact with electrons, inducing lots of electronic excitations. Incorporating the latter with atomistic dynamics is especially difficult in insulators, and the methods have not yet been fully established. SHIs can induce a cylindrical region of structural transformation known as an ion track. In crystalline silicon dioxide, a track consists of an amorphized region that is typically several microns long and has a radius of less than ten nanometers. Furthermore, it was recently found out that SHI irradiation can be used to induce a shape transformation in metal nanoclusters (NCs) that are embedded in amorphous silicon dioxide. Spherical NCs (radius 1-50 nm) elongate along the ion beam direction and are shaped into nanorods or prolate spheroids. The phenomenon can be exploited to produce large arrays of equally aligned nanoclusters within a solid substrate, which is difficult to achieve otherwise. In this thesis, ion track formation and the elongation of gold nanoclusters in silicon dioxide are studied using so called two-temperature molecular dynamics simulations. The structure of the tracks is studied and a mechanism is proposed for the nanoparticle elongation effect. The work presented here is a step towards the understanding of SHI related effects in a broader range of insulating materials for the SHI based applications.
  • Hannula, Miika (Helsingin yliopisto, 2015)
    Dependence logic is a novel logical formalism that has connections to database theory, statistics, linguistics, social choice theory, and physics. Its aim is to provide a systematic and mathematically rigorous tool for studying notions of dependence and independence in different areas. Recently many variants of dependence logic have been studied in the contexts of first-order, modal, and propositional logic. In this thesis we examine independence and inclusion logic that are variants of dependence logic extending first-order logic with so-called independence or inclusion atoms, respectively. The work consists of two parts in which we study either axiomatizability or expressivity hierarchies regarding these logics. In the first part we examine whether there exist some natural parameters of independence and inclusion logic that give rise to infinite expressivity or complexity hierarchies. Two main parameters are considered. These are arity of a dependency atom and number of universal quantifiers. We show that for both logics, the notion of arity gives rise to strict expressivity hierarchies. With respect to number of universal quantifiers however, strictness or collapse of the corresponding hierarchies turns out to be relative to the choice of semantics. In the second part we turn attention to axiomatizations. Due to their complexity, dependence and independence logic cannot have a complete recursively enumerable axiomatization. Hence, restricting attention to partial solutions, we first axiomatize all first-order consequences of independence logic sentences, thus extending an analogous result for dependence logic. We also consider the class of independence and inclusion atoms, and show that it can be axiomatized using implicit existential quantification. For relational databases this implies a sound and complete axiomatization of embedded multivalued and inclusion dependencies taken together. Lastly, we consider keys together with so-called pure independence atoms and prove both positive and negative results regarding their finite axiomatizability.
  • Patokoski, Johanna (Helsingin yliopisto, 2015)
    Volatile organic compounds (VOCs) are known to be key players in the atmospheric processes. They are emitted both from natural and non-biogenic sources. Although the biogenic sources are generally dominant compared with the anthropogenic sources in some circumstances the anthropogenic emissions can dominate e.g. in densely populated areas or during pollution plumes. VOCs are ambient trace gases including a vast group of compounds. Some of the VOCs are very reactive, participating in atmospheric transformation processes e.g. secondary organic aerosol formation and growth. Some VOCs are also known to be harmful air pollutants for humans. Thus VOCs can have direct effects on air quality and secondary effects on climate. In this thesis, the aim was to define sources of VOCs, determine influence of transport and transformation of trace gases and aerosols. VOCs were measured mainly by a real time proton transfer reaction mass spectrometer. In addition, gas and liquid chromatography were used. The measurements were conducted at the rural SMEAR II and the urban background SMEAR III sites. Concentrations of VOCs were observed to have inter-annual, seasonal and diurnal variations due to meteorological factors, photochemistry and different sources. The anthropogenic influence was dominant in winter at both sites, while the biogenic influence with enhanced photochemical reactions increased in spring. The mixing and dilution effect also increased in spring and it led to decreased levels of volume mixing ratios (VMRs) in daytime especially in short-lived compounds. The VMRs of aromatic compounds were lower in spring than in winter due to lesser sources and enhanced photochemistry at both sites. At the urban background site there were more local sources than rural site and thus more variation of the diurnal patterns; higher VMRs of VOCs were observed. At both sites long-range transport was found to be an important source for long-lived VOCs. The source areas of long-lived VOCs were studied with trajectory analysis. Eastern Europe including West Russia was found to be major source area for all studied VOCs. In addition, some of them had specific source areas of their own related e.g. to their use in the solvent industry. During measurements there were two different forest fire episodes in Eastern Europe and a one-day prescribed biomass burning experiment. VMRs of VOCs related to burning were observed to increase during these pollution plumes. Atmospheric oxidation of BVOCs (biogenic VOCs) revealed that monoterpenes and their oxidation products by ozone were limiting factors for nucleation particle growth. Study of total OH reactivity showed that there are a number of unmeasured biogenic compounds which may have effects on the local atmospheric chemical processes. Keywords: variations of VOC concentrations, source analysis, long-range transport, forest fires, atmospheric chemistry
  • Niemi, Esa (Helsingin yliopisto, 2015)
    Inverse problems arise, for example, from various imaging applications in medicine and physics. Their inherent property is ill-posedness; even a very small error in the measurement data can lead to a large error in the reconstruction. To overcome this difficulty, regularization is necessary for the inversion. In this work three new computational regularization methods for limited-data inverse problems are introduced and studied. The problems of special interest are stationary and dynamic X-ray tomography (CT) with sparsely sampled X-ray projection data and acoustic inverse scattering with limited-aperture data. In the first article of this thesis we develop a computational reconstruction algorithm for solving stationary sparse-data CT problems. Sparse-data cases arise e.g. from the need to minimize radiation dose in medical imaging. The new reconstruction algorithm is based on total variation regularization, it preserves sharp features of the target and is suitable for large-scale problems such as 3D CT. Its performance is illustrated by numerical results computed from both simulated and real X-ray data. In the second and third articles we introduce an inversion method for dynamic CT application making use of a few fixed X-ray sources and detectors. In this application the attainable temporal resolution is high while the CT data measured at a single time step is extremely sparse. The inversion method is motivated by level set methods and it regularizes the problem in space-time so that certain regularity is required both in spatial and temporal directions. Some of its important theoretical aspects are analyzed, and a computational implementation of the method is tested using both simulated and real X-ray data. The new methodology provides whole new possibilities e.g. for 4D angiographic imaging with high temporal resolution. In the fourth article a numerical implementation of the so-called enclosure method by Masaru Ikehata is introduced and studied using simulated test data. The enclosure method is suitable for limited-aperture obstacle scattering problems, where one uses only one incident wave and measures the far field pattern of the scattered field on some possibly limited aperture. The name of the method comes from the fact that it finds the convex hull of the obstacle, rather than its precise shape. Numerical evidence presented suggests that the method can approximately recover the shape and position of an obstacle from noisy limited-aperture far field data.
  • Tolppanen, Sakari (Helsingin yliopisto, 2015)
    Chemistry plays a key role in dealing with several of the big environmental problems of the future, but yet, chemistry education is often seen as irrelevant by students. Therefore, it is evident that ways to make chemistry education more relevant are called for. Educational experts have argued that sustainable development is a context that would bring relevance to science education, including chemistry education, as it bridges the gap between science and society. However, research on students perspective on the relevance of sustainable development is scarce. This thesis examines sustainable development and its education from the students viewpoint. This is done by seeking to answer the research problem: What do international students find relevant in sustainable development and its education? To answer this research problem, this thesis breaks down the problem into four research questions. The first research question examines what type of questions students ask about sustainable development, particularly in the area climate change. The second research question examines the kind of actions students take to make the world a better place. The third research question examines students expectations when applying to a non-formal educational program focused on sustainable development. The last research question examines how these expectations were met through the non-formal educational program. To address the research problem, the thesis adopted a multi-method approach, consisting of descriptive research, case studies and elements of grounded theory. The data was collected before, during and after an international youth camp, the Millennium Youth Camp held in the summers of 2010-2014. The participants of the study were 16-19 -year old students from around the world who were interested in science. The thesis consists of six interconnected studies. The first study examines the type of questions students ask about sustainable development and the second study examines the type of questions students ask about climate change, specifically. The data for these two studies were collected through an online survey from the students applying to the international youth camp. The data were analyzed using content analysis. The results indicate that students ask a variety of academic, societal and moral questions related to sustainable development. These questions cover many relevant aspects of sustainable development, and climate change specifically, and build a premise for student-centered education. In the third study, students attending the international youth camp were interviewed on the type of actions they take to make the world a better place. The data was analyzed though inductive and deductive content analysis and the results show that student actions can be categorized into three distinct groups, namely, personal responsible actions, participatory actions and future oriented actions. The fourth study used quantitative methods to address what type of expectations students have in education for sustainable development. The data was collected from students applying to the non-formal education program. The results show that in addition to wanting more knowledge on specific scientific phenomena and the nature of science, students expect to learn about societal impacts of environmental issues and discuss related moral issues. Studies four, five and six examine how the aforementioned expectations of the students can be met through non-formal education. These studies examine what type of structures and programs in the camp made the educational experience relevant for the students. The thesis concludes by asserting that students questions, actions and expectations can be used to make education for sustainable development more relevant in a number of ways. The thesis discusses the possibilities of (i) moving towards more student-centered learning, in which students questions and actions are the foundation of education, (ii) increasing relevant social and societal discussion with peers and experts, and (iii) providing students with opportunities to work on projects that address student interest. The thesis takes examples from the non-formal educational program studied and discusses how these same methods could be implemented into other similar programs or formal education.
  • Keceli, Asli (Helsingin yliopisto, 2015)
    The Standard Model of particle physics (SM) is a gauge field theory that provides a very successful description of the electromagnetic, weak and strong interactions among the elementary particles. It is in very good agreement with the precision measurements and the list of all the fundamental particles predicted by the model was completed with the discovery of the last missing piece, the Higgs boson, at the LHC in 2012. However, it is believed to be valid up to a certain energy scale and widely considered as a low-scale approximation of a more fundamental theory due to some theoretical and phenomenological issues appearing in the model. Among many alternatives, supersymmetry is considered as the most prominent candidate for new physics beyond the SM. Supersymmetry relates two different classes of the particles known as fermions and bosons. The simplest straightforward supersymmetrization of the SM is named as minimal supersymmetric Standard Model (MSSM) where minimal set of new supersymmetric particles is introduced as superpartners of the Standard Model particles. It is the most studied low-scale supersymmetric model since it has very appealing features such as containing a dark matter candidate and providing a solution to the naturalness problem of the SM. After the Higgs discovery, the parameter space of the model has been investigated in great detail and it has been observed that the measured Higgs mass can be achieved only for the parameter regions which generate a severe fine-tuning. Such large fine-tuning can be alleviated by extending the minimal field content of the model via a singlet and/or a triplet. In this thesis, we discuss the triplet extension of the supersymmetric Standard Model where the MSSM field content is enlarged by introducing a triplet chiral superfield with zero hypercharge. The first part of the thesis contains an overview of the SM and the second part is dedicated to the general features of supersymmetry. After discussing aspects of the MSSM in the third part, we discuss the triplet extended supersymmetric Standard Model where we investigate the implications of the triplet on the Higgs phenomenology. We show that the measured mass of the Higgs boson can be achieved in this model without requiring heavy third generation squarks and/or large squark mixing parameters which reduce the amount of the required fine-tuning. Afterwards, we study the charged Higgs sector where a triplet scalar field with non-zero vacuum expectation value leads to h±iZW∓ coupling at tree level. We discuss how this coupling alters the charged Higgs decay and production channels at the LHC.
  • Mehtälä, Juha (Helsingin yliopisto, 2015)
    Continuous-time Markov processes with a finite state space can be used to model countless real world phenomena. Therefore, researchers often encounter the problem of estimating the transition rates that govern the dynamics of such processes. Ideally, the estimation of transition rates would be based on observed transition times between the states in the model, i.e., on continuous-time observation of the process. However, in many practical applications only the current status of the process can be observed on a pre-defined set of time points (discrete-time observations). The estimation of transition rates is considerably more challenging when based on discrete-time data as compared to continuous observation. The difficulty arises from missing data due to the unknown evolution of the process between the actual observation times. To be able to estimate the rates reliably, additional constraints on how they vary in time will usually be necessary. A real world application considered in this thesis involves the asymptomatic carriage state (colonisation) with the bacterium \textit{Streptococcus pneumoniae} (the pneumococcus). The pneumococcus has over 90 strains and for understanding the dynamics of the pneumococcus among humans it is important to understand within-host competition between these strains. Research questions regarding competition in this thesis are: does colonisation by one serotype protect from acquisition of other serotypes and is clearance affected by concurrent colonisation by other serotypes? A question regarding the implication of competition to pneumococcal dynamics after vaccination is also of interest. In addition, vaccine protection may be heterogeneous across individuals, leading to a question about how well such vaccine protection can be estimated from discrete-time data. When only discrete-time observations are available, the decision when to measure the current status of the process is particularly important. With measurements that are temporally apart from each other, information about the state of the process at one point does not give information about the state at the other points. When measurements are very close to each other, knowing the state at one point bears information about the state at other, temporally close points. This thesis addresses the estimation of transition rates based on repeated observations of the current status of an underlying continuous-time Markov process. Applications to actual data concern the process of pneumococcal colonisation. Optimal study designs are considered for improved future studies of similar type, applications including but not limited to pneumococcal colonisation studies.
  • Rautio, Anne (Helsingin yliopisto, 2015)
    Groundwater (GW) and surface water (SW) have been studied as separate resources in most previous hydrological or hydrogeological studies in Finland. This traditional research approach has both underestimated the commonness of natural exchange between GW and SW systems and oversimplified the management of water resources. This thesis research investigated the previously poorly recognized GW−SW interactions in two boreal snow-type catchments, Lake Pyhäjärvi and River Vantaa, with physical methods, isotopic and chemical tracers and thermal methods, particularly low-altitude aerial infrared (AIR) surveys. The aim of the work was to identify the GW−SW interactions sites, to define the ubiquity of these interactions, to assess the applicability of the used methods, to provide baseline data on seasonal variation in isotopic and chemical tracers in the studied catchments and to provide new insights into more integrated water resources management. The field studies performed in Lake Pyhäjärvi revealed that the direct GW discharge areas are associated with the esker deposits and focused on the 10-km NE shoreline of lake. The direct GW discharge was spatially highly variable due to the heterogeneous substrate in lake shoreline area. The results from the various methods correlated and confirmed the GW discharge into Lake Pyhäjärvi at the NE shoreline. The baseline data on isotopic patterns and hydrogeochemistry in the hydrological cycle were provided by a one-year monitoring survey in the Lake Pyhäjärvi catchment. The results revealed strong seasonality in general water chemistry, stable isotopes and dissolved silica concentrations of different water bodies on the catchment scale that should be considered in GW SW interaction studies in northern high-latitude regions with snow-type hydrology. Samples taken during the spring thaw and high-precipitation events could be problematic in terms of both sampling and interpreting the results. In the River Vantaa and its tributaries (a 203-km-long river channel altogether), around 370 GW discharge sites were located with two catchment scale AIR surveys in two consecutive years. The identified interaction locations in the proximity of 12 municipal water intake plants during the low-flow seasons should be considered as potential risk areas for water supply during flood periods and/or with high pumping rates and taken under consideration in water resources management. This work revealed that the GW−SW interactions are a far more general phenomenon in the studied catchments than has thus far been acknowledged, and these two resources should be integrated as one entity in hydrological studies. The GW−SW interaction should be taken account in water resources management, especially in changing climate conditions. This work highlighted the importance of an integrated approach that applies detailed local field measurements combined with chemical and isotopic sampling, as well as AIR surveys on the catchment scale.
  • Loman, Tina (Helsingin yliopisto, 2015)
    Health behaviours are important to prevention and public health. Health behaviours include usually food habits, physical activity, drinking, smoking and sleeping. Improving health behaviours help reduce risks for several major chronic diseases and mortality. Food habits and physical activity play a key role in reducing weight gain and related disease risk. Health behaviours are socially patterned and they vary between socioeconomic groups, and contribute to inequalities in health. In order to reduce socioeconomic differences in health, novel evidence is needed of changes in socioeconomic differences of health behaviours as well as reasons behind the socioeconomic differences. The main aim of this study was to examine socioeconomic differences in food habits, physical activity and weight gain, and their changes over time among middle-aged female and male public sector employees. Specific aims were to examine first changes in occupational class differences in food habits and second in physical inactivity and activity during a follow-up of 5-7 years, considering the effects of covariates. The third specific aim was to examine the association between weight gain and multiple socioeconomic indicators. This study is part of the Helsinki Health Study (HHS). The baseline data were collected by questionnaire surveys in 2000, 2001 and 2002 (n=8 960, response rate 67%). Mail surveys were sent to employees of the City of Helsinki aged 40-60 years. The follow-up survey data were collected in 2007 among the baseline respondents (n=7 332, response rate 83%). For data analysis general linear models, logistic regression analysis and the relative index of inequality were used. In many food habits, there was a hierarchical order according to occupational class, i.e. those in higher occupational classes used more often the studied food item than those in lower classes. In some food habits, there was a reverse hierarchical order and in some food habits there were no socioeconomic differences. Occupational class differences largely remained stable over the follow-up in the food habits. At baseline, there were no occupational class differences in leisure-time physical activity, but over the follow-up physical activity increased among women with the highest occupational class and decreased among men with the lowest occupational class, suggesting the emergence of occupational class differences at follow-up. The covariates (age, marital status, body mass index physical and mental health functioning, employment status) did not substantially affect the observed occupational class differences in leisure-time physical activity at follow-up. Among women and men, socioeconomic differences were observed in at least 5 kg weight gain, and current economic difficulties showed the strongest association with weight gain. Socioeconomic differences largely remained stable over the 5-7 year follow-up in food habits, whereas in leisure-time physical activity differences emerged. There were clear differences in weight gain by economic difficulties. Thus, there is a continuous need for reducing socioeconomic inequalities in the studied health behaviours. Healthy behaviours should be promoted in particular among those in lower occupational classes and those with economic difficulties.
  • Xiong, Jie (Helsingin yliopisto, 2015)
    A general inductive probabilistic framework for clustering and classification is introduced using the principles of Bayesian predictive inference, such that all quantities are jointly modelled and the uncertainty is fully acknowledged through the posterior predictive distribution. Several learning rules have been considered and the theoretical results are extended to acknowledge complex dependencies within the datasets. Multiple probabilistic models have been developed for analysing data from a wide variate of fields of application. State-of-art algorithms are introduced and developed for the model optimization.
  • Karjalainen, Erno (Helsingin yliopisto, 2015)
    This thesis combines anion responsive polymeric ionic liquids (PILs) with thermoresponsive polymers. The polymers have been synthesized with controlled radical polymerization methods. A water-insoluble PIL was used as a macro-chain transfer agent in synthesis of block copolymers with poly(N-isopropyl acrylamide) (PNIPAm). PNIPAm chains of various lengths were grown to the same PIL-block. These polymers show a lower cirical solution temperature (LCST) type behavior, typical to PNIPAm. The PIL block and the PNIPAm block interact strongly, no phase transition can be observed for the block copolymers with short PNIPAm chains. The block copolymers form complex aggregates in water. The hydrophobic PIL-homopolymer can be used to make stable particles in salt free water. Also triblock copolymers with a long central PNIPAm block and short water soluble PIL blocks were synthesized. These polymers also show interactions between the PIL and PNIPAm blocks. This can be seen for example as reduced enthalpy of phase transition for the triblock copolymers compared to the PNIPAm homopolymer. The triblock copolymers form complex aggregates at elevated temperatures. The LCST-type phase transtiton of weakly cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) can be modified with bis(trifluoromethane)sulfonamide (NTf2) ions. The presence of NTf2 induces also an upper critical solution temperature (UCST) type transition for PDMAEMA, if the polymer is charged enough. NTf2 turns PDMAEMA to a stronger base, presumably due to the effective screening of charges. NTf2 induces an UCST-type transition for strong polycations in the presence of an added electrolyte. The phase behavior of the polycation-NTf2 system can be influenced by addition of sodium chloride. Similar transition can also be induced by trifluoromethanesulfonate (OTf), though OTf is needed in much higher concetrations. This allows the use of OTf as the only salt. The NTf2-polycation interactions influence the phase behavior of copolymers of N-isopropyl acrylamide (NIPAm) and strongly cationic (3-acrylamidopropyl) trimethylammonium chloride (AMPTMA). With low AMPTMA content, the copolymers show LCST-type behavior in the presence of NTf2 and a copolymer with high AMPTMA-content shows UCST-type behavior. If NIPAm and AMPTMA are copolymerized in nearly equal amounts, both transitions may coexist.
  • Eskelä, Elina (Helsingin yliopisto, 2015)
    Cities are striving to attract and retain talented workers in order to increase their competitiveness in the new economy, which is highly dependent on innovation and knowledge. Residential satisfaction has been identified as a key determinant of whether a person stays or moves to another location. However, given the tendency to focus on the housing of immigrant groups with a lower socio-economic status, the factors that affect the residential satisfaction of skilled migrants remain understudied. This article-based dissertation in the field of urban geography examines the determinants of residential satisfaction among skilled migrants living in the Helsinki metropolitan area (HMA), Finland. The research setting is intended to maximise the cultural and socio-economic as well as locational diversity within the limits of recognised skilled migrant groups. The analysis focuses on how the interplay between individuals norms and the situational conditions is manifested when immigrants assess a single housing market, the HMA. The study is qualitative in nature and draws on 70 semi-structured interviews with skilled migrants and with experts on migration and housing in the city region. Despite the cultural, socioeconomic and locational heterogeneity of the interviewees, their experiences of housing in the HMA were notably similar: the uppermost assessment was that it is expensive, cramped and uniform. On the other hand, they appreciated the overall safety and functionality of the city region, as well as the natural environment: the predominant influence, for them, is the family life cycle rather than the urban amenities that are often assumed to be highly important for the creative class . The results also show that homeownership is not a simple indicator of the intention to stay in or leave the region, which contradicts earlier findings on ethnic-minority housing. The study underlines the importance of the social environment in creating residential satisfaction among skilled migrants. Whereas earlier studies revealed the essential nature of social networks and personal trajectories in the location decisions of skilled workers, the results of this study indicate that the supply of local, neighbourhood-based social ties is particularly limited in the case of the HMA, and that this has a negative impact on the residential satisfaction of skilled migrants. Furthermore, the structural element of housing seemed to have an effect on local social ties: among international students the extent of such ties varied according to the housing form. Although many skilled migrants are in a good socio-economic position, they are not immune to problems related to finding suitable housing. Housing availability, quality and affordability are therefore significant factors in enhancing residential satisfaction among such groups. Furthermore, as local social ties serve a mediating role with regard to the residential area as well as to society, the formation of such ties would promote the integration of migrants. These aspects of housing should be acknowledged in the strategies of cities wishing to accommodate and retain global talent. Keywords: skilled migrants, housing, residential satisfaction, social ties, Helsinki metropolitan area
  • Juntunen, Marianne (Helsingin yliopisto, 2015)
    Chemistry plays an important role in making the future more sustainable and solving the related global issues. Curricula, national and international educational strategies, research literature and chemical industry are all focusing on sustainable development. We need more environmentally literate chemists, chemistry teachers and students future citizens, who are to solve the numerous environmental challenges that face the whole world. The main aim of this design research study was to find out what are the features of holistic and inquiry-based education for sustainable development in chemistry. At the same time, the aim was to foster students environmental literacy, argumentation skills and positive attitudes towards chemistry. Education for sustainable development in chemistry is related to socio-scientific issues, e.g., life-cycle thinking and green chemistry. Theoretical problem-analysis of the study was used to investigate the approaches that are of key importance to the study presented in this dissertation: sustainable development, green chemistry, the life-cycles of different products, environmental literacy, socio-scientific education, and the pedagogical methods of inquiry-based learning and argumentation. The empirical design phase sought an answer to the main research question: What are the main features of holistic and inquiry-based education for sustainable development in chemistry? The main focus of the research was in teaching life-cycle analysis, which is one of the key elements in the Finnish national curriculum. The design research project constituted of three phases, which were conducted during the years 2010 2014. The first empirical phase was conducted in four chemistry teachers in-service training courses. During these courses, a total of 20 chemistry teachers created new inquiry-based methods for teaching life-cycle analysis in chemistry. This development process was based on theoretical problem analysis. The second empirical phase focused on creating a collaboratively-developed design solution based on the teachers concepts and the effects of this solution. The participants in this second phase were 105 9th grade students, whose environmental literacy, argumentation skills and attitudes towards chemistry learning were evaluated. The third phase was theoretical. It consisted of comparing the gained empirical knowledge to theoretical literature in order to answer the main research question. The methods of data analysis included content analysis of texts, semi-structured interviews and quantitative surveys. The validity of the results of the conducted cyclic design research project is enhanced by theoretical literature analysis, methodological triangulation, researcher triangulation, the testing of the developed teaching concept in authentic environments and the systematic, visualised documentation of the design phases. The design phases resulted in three types of knowledge: 1) new chemistry teaching concepts for sustainability education that use life-cycle thinking and inquiry-based learning methods, and a collaboratively-developed design solution (Article I), 2) knowledge about how inquiry-based learning of life-cycle analysis affects students environmental literacy, argumentation skills and attitudes towards chemistry (Articles II and III) and 3) domain knowledge about holistic and inquiry-based education for sustainable development in chemistry (Article IV). Holistic and inquiry-based education for sustainable development in chemistry includes interdisciplinary and socio-scientific issues. Socio-constructivist and contextual chemistry education is bound to societal actors and co-operational, real-life activities. Learning occurs in social interaction, through argumentation and self-reflection, for example. The students themselves may choose the focus of inquiry, and it may relate to raw materials, consumer products, food substances or water, for example. As the knowledge of chemistry is combined with possibilities for societal action, the importance of chemistry becomes apparent to the students. They gain competence to act towards building a more sustainable future. The improved scientific and ecological argumentation skills reflect their environmental literacy and competence in societal thinking. The holistic and inquiry-based chemistry education presented in this dissertation supports versatile studying and citizenship skills in a new way. It motivates students to study chemistry and guides them to take sustainable development into account. Education for sustainable development is needed at all school levels. The approaches presented in this study may be applied on all levels of education. The results may be used to promote sustainable development in the planning of chemistry education and the education of chemistry teachers. Keywords: chemistry education, sustainable development, green chemistry, teaching concepts, design research
  • Kalinowski, Jaroslaw (2015)
    One of the goals of modern quantum chemistry is to simulate actual chemical experiments. In order to study species closer to real life systems and bulk environments there is a need for methodological developments. There are two ways to approach large systems with a given level of accuracy: conceptual changes to quantum chemistry methods or algorithmic developments for current methods. Many scientists believe that the conceptual changes truly increase the size of the systems one can study. With more or less advanced approximations to the method it is possible to increase the efficiency of calculations orders of magnitude. The implementation and algorithms fall down in the priority list, as advanced algorithmic developments are time consuming and usually lead to lower efficiency increases than conceptual changes. In this work it is shown that algorithmic developments cannot be neglected, and that even simple changes help in utilizing the power of modern computers and can also increase the efficiency by orders of magnitude. In this work new algorithmic developments are presented and used for solving various timely chemical problems.
  • Paramonov, Mikhail (Helsingin yliopisto, 2015)
    The research conducted and presented herein concentrates primarily on the life cycle of a cloud condensation nucleus CCN. The primary motivation of the work is the importance of CCN in the global aerosol-cloud-climate system, and focus is placed on the production of CCN, their behaviour in the atmosphere and their properties with respect to CCN activation, as well as the removal pathways. The work presented in this thesis covers measurements performed at 16 locations around the world. The results further corroborated the notion that atmospheric new particle formation NPF is an important and widespread source of CCN in the atmosphere. The number of newly formed CCN from NPF depends on many factors, including, but not limited to, biogenic and anthropogenic emissions, frequency of NPF events, nucleation and growth rates and pre-existing CCN concentrations; method of calculation also affects the estimate of NPF contribution to CCN budgets. Highest relative increase in CCN as a result of NPF was observed at a clean remote location in Northern Finland, where in the summer the number concentration of particles above 50 nm in diameter N50 can increase by as much as 800%. Highest absolute increases in NCCN as a result of NPF (up to 3500 particles cm 3 for N50) were found at a dry savannah location of Botsalano in South Africa. In Hyytiälä Type I nucleation events were found to always, at the very least, double NCCN concentrations. It was found that in many environments around the world a rather similar fraction of aerosols activated into cloud droplets at any given level of supersaturation S, and a simple linear parameterisation is provided for an easy calculation of annual mean CCN concentration NCCN based only on total number concentration NCN and the desired S. At the majority of studied locations hygroscopicity was found to increase with size, with accumulation mode hygroscopicity parameter κ values being significantly larger than Aitken mode κ at some locations. Depending on the focus and desired accuracy, the use of κ values as a function of particle dry size rather than the assumption of a size-independent κ should preferably be considered. The photochemistry, aging processes, atmospheric NPF and other atmospheric processes occurring on a diurnal scale were found to affect the CCN activation and hygroscopic properties of Aitken mode aerosol only. The hygroscopicity of the accumulation mode aerosol is more affected by processes occurring on a time scale of a few days to months, e.g. long range transport and seasonal variation in vegetation activity. Below-cloud scavenging by snow was found to be an inefficient mechanism of CCN removal from the atmosphere compared to, e.g., in-cloud scavenging. Additionally, nucleation and Aitken mode particles are scavenged by snow more efficiently that CCN-sized aerosol. No apparent difference in the scavenging efficiency of snow was observed between a rural and an urban site in Southern Finland. Ambient relative humidity was found to correlate positively with the scavenging efficiency of snow, and a new parameterisation for calculating snow scavenging coefficients based on both particle dry size and relative humidity is presented. A reconsideration of the purpose, the focus and the motivation for the cloud condensation nuclei counter CCNC measurements at the SMEAR II is needed if they are to be continued with reasonable, interesting and exciting output.
  • Häme (née Häkkinen), Silja (Helsingin yliopisto, 2015)
    Aerosol particles are important atmospheric constituents. They exist in both polluted and remote areas but the sizes and concentrations of these particles vary greatly depending on location. Aerosol particles damage human health via inhalation, reduce visibility with high mass loadings, and among all, contribute to climate change. Particles directly scatter and absorb solar radiation. In addition, particles that are large enough can participate in cloud formation and affect cloud properties by acting as cloud condensation nuclei (CCN). A notable fraction of submicron atmospheric aerosol mass consists of organic compounds, and a large fraction of this material has been formed through condensation of organic vapors onto aerosol particles (secondary organic aerosol, SOA). Most of the global SOA mass is deemed to be biogenic in origin, but recent studies suggest that a significant fraction of it may be controlled by anthropogenic pollution. However, due to poor understanding of this anthropogenic enhancement in biogenic SOA formation, it is not systematically accounted for in current atmospheric models. Due to these kind of uncertainties in global SOA mass burden and lack of detailed knowledge of chemical, physical and optical properties of SOA, estimates of organic aerosol effect on the climate are highly uncertain. To decrease the uncertainty in the climate effects of the organic aerosol, an improved understanding of the formation mechanisms and properties of SOA is needed. In addition, nanoparticle growth to CCN-sizes by condensation of secondary organic matter needs to be accurately described in atmospheric models. In this thesis the formation of SOA is investigated in the presence of both biogenic and anthropogenic compounds. The chemical and physical properties volatility and hygroscopicity of SOA are examined via field and laboratory experiments combined with process modeling. The thesis introduces improvements for the treatment of SOA related to nanoparticle growth in atmospheric models and evaluates their performance. The thesis shows that interactions between atmospheric biogenic and anthropogenic aerosol components can form aerosol material of low-volatility. For instance organic salt formation via chemical reactions between organic acids and inorganic salts can lower aerosol volatility. Particulate-phase processing may also alter aerosol hygroscopic properties. Description of nanoparticle growth by low-volatility secondary organics is important in improving the estimates of particle and CCN numbers. The thesis highlights the significance of biogenic organic matter formed under anthropogenic influence in the nanoparticle growth. This warrants future studies focusing on the formation mechanisms and properties of anthropogenically driven biogenic organic aerosol.
  • Zou, Xiaochen (Helsingin yliopisto, 2015)
    Leaf angle distribution (LAD) is one of the most important parameters used to describe the structure of horizontally homogeneous vegetation canopies, such as field crops. LAD affects how incident photosynthetically active radiation is distributed on plant leaves, thus directly affecting plant productivity. However, the LAD of crops is difficult to quantify; usually it is assumed to be spherical. The purpose of this dissertation is to develop leaf angle estimation methods and study their effect on leaf area index (LAI) and chlorophyll a and b content (Cab) measured from optical observation. The study area was located in Viikki agricultural experimental field, Helsinki, Finland. Six crop species, faba bean, narrow-leafed lupin, turnip rape, oat, barley and wheat, were included in this study. A digital camera was used to take photographs outside the plot to record crop LAD. LAI and Cab were determined for each plot. Airborne imaging spectroscopy data was acquired using an AISA Eagle II imaging spectrometer covering the spectral range in visible and near-infrared (400 1000 nm). A recently developed method for the determination of leaf inclination angle was applied in field crops. This method was previously applied only to small and flat leaves of tree species. The error of LAI determination caused by the assumption of spherical LAD varied between 0 and 1.5 LAI units. The highest correlation between leaf mean tilt angle (MTA) and spectral reflectance was found at a wavelength of 748 nm. MTA was retrieved from imaging spectroscopy data using two algorithms. One method was to retrieve MTA from reflectance at 748 nm using a look-up table. The second method was to estimate MTA using the strong dependence of blue (479 nm) and red (663 nm) on MTA. The two approaches provide a new means to determine crop canopy structure from remote sensing data. LAI and MTA effects on Cab sensitive vegetation indices were examined. Three indices (REIP, TCARI/OSAVI and CTR6) showed strong correlations with Cab and similar performance in model-simulated and empirical datasets. However, only two (TCARI/OSAVI and CTR6) were independent from LAI and MTA. These two indices were considered as robust proxies of crop leaf Cab. Keywords: leaf angle; leaf area index; leaf chlorophyll; digital photograph; imaging spectroscopy; PROSAIL model; vegetation indices
  • Muuronen, Mikko (Helsingin yliopisto, 2015)
    Understanding the electronic structure of a chemical system in detail is essential for describing its chemical reactivity. In the present work, quantum chemical methods are applied in combination with experimental studies to achieve such detailed mechanistic understanding of chemical systems. Understanding the basic theory behind computational methods is of importance when applying them to chemical problems. Therefore, the first part of this work provides an introduction to quantum chemical methods. The results of this work are published in four peer-reviewed publications. In each publication, the understanding of the chemical system has been obtained using a combination of experimental and quantum chemical studies. These include the design of a new-type of Au(III)-catalysts, and understanding mechanistic aspects related to a Au(III) catalytic cycle. We have also focused on understanding how the electronic structure of an alkyne affects the regioselectivity in the Pauson-Khand reaction. A computational model, which provides a qualitative and, to some extent, a quantitative prediction of regiochemical outcomes is presented.