In the present work the coupling reactions of carbon dioxide with epoxides to produce five-membered cyclic carbonates (propylene, 1-hexene, cyclohexene, styrene, and epichlorohydrin carbonates) were efficiently catalyzed either by sustainable metal-based catalysts of: (1) titanium alkoxide complexes/tetrabutylammonium salts; (2) Schiff base iron(III) complexes/onium salts; (3) bifunctional imidazole-Schiff base iron(III) complex; and (4) metal-free systems consisting of a simple, preferably primary or secondary, amines and halides with organic or inorganic cations (such as tetrabutylammonium or lithium chloride, bromide or iodide). Reactivity of the four above-mentioned catalytic systems was further studied and compared in the coupling reactions.

]]>We will empirically show that these models can be used in practice at least for three tasks: generation of creative combinations of related words, document summarization, and creating poetry. First the common word association language model is used for solving tests of creativity -- the Remote Associates test. Then observations of the properties of the model are used further to generate creative combinations of words -- sets of words which are mutually not related, but do share a common related concept.

Document summarization is a task where a system has to produce a short summary of the text with a limited number of words. In this thesis, we will propose a method which will utilise the document-specific associations and basic graph algorithms to produce summaries which give competitive performance on various languages. Also, the document-specific associations are used in order to produce poetry which is related to a certain document or a set of documents. The idea is to use documents as inspiration for generating poems which could potentially be used as commentary to news stories.

Empirical results indicate that both, the common and the document-specific associations, can be used effectively for different applications. This provides us with a simple language model which could be used for different languages.

]]>The first paper in the thesis concerns the theory of quasiregular mappings, which are non-homeomorphic generalizations of quasiconformal mappings; heuristically quasiregular mappings can be defined as mappings that map infinitesimal balls to infinitesimal ellipsoids with a bound on the eccentricity of the ellipsoid. The first article is especially focused on quasiregularly elliptic manifolds, i.e. those closed Riemannian manifolds for which there exists a non-constant quasiregular mapping from the euclidean space of same dimension to the manifold. The classes of quasiregularly elliptic 2- and 3-manifolds are classified up to a quasiconformal homeomorphism. In higher dimensions it is still a widely open question which closed manifolds are quasiregularly elliptic, but even though a complete classification of quasiregularly elliptic manifolds is hard, there are results restricting the structure of quasiregulary elliptic manifolds. One of the basic results is the Varopoulos theorem that gives an upper bound to the growth rate of the fundamental group of a quasiregularly elliptic manifold. The main result of the first paper is that if the growth rate of the fundamental group of a quasiregularly elliptic manifold is as large as possible, then the manifold is in fact a finite quotient of a torus.

Mappings of bounded length distorion, BLD-mappings for short, were first defined by Martio and Väisälä in 1988 in euclidean domains as a subclass of quasiregular mappings. Even though the original defintion of BLD-mappings was analytical, Martio and Väisälä showed that there exists also a definition with a more metric flavor. Indeed, BLD-mappings can be defined as those open, continuous and discrete mappings that preserve the length of all paths up to a uniform multiplicative constant. This definition lends itself to all (path-)metric spaces, and in the latter two articles of the thesis we study which classical results of euclidean BLD- or quasiregular mappings can be proven in the setting of locally compact and complete path-metric spaces.

]]>The mechanical properties of materials are known to be determined by the movement of dislocations. If the dislocation movement is hindered, the material will become harder, but also more brittle. Previous computational studies have investigated the effect of voids, bubbles and other dislocation structures on the movement of dislocations. However, the effect of non-coherent obstacles, man-made or irradiation induced, have received much less attention. To address this lack of data, we have investigated the effect of carbides, to represent non-coherent obstacles, on the dislocation movement.

In this study we investigated different carbides and compared them with other defect structures, voids and fixed atoms. The effect of size and temperature were also determined. We obtained two parameters for each obstacle, the needed unpinning stress and the unpinning mechanism, that can be used in other simulation methods to be able to investigate larger systems. We found that the nanostructure of the obstacle can drastically change the needed unpinning stress. We also found that the obstacles with same unpinning mechanism showed similar unpinning stresses, but to obtain the subtle differences we need to consider the nanostructure. A comparison of spherical and rod shaped obstacles showed that the surface curvature will be an important factor in the unpinning event.

Recently, a new class of metal alloys have been found, where the concentrations of the alloying elements are in large or equal fractions. We wanted to investigate the possibility to use these equiatomic multicomponent alloys in environments where radiation is present. These alloys have been shown to have very promising properties, but there were no data on the irradiation response of these alloys. We studied two equiatomic multicomponent alloys, two-element and three-element alloys, and compared them with the single element specimen. We found a major reduction of defect build-up in the alloys compared to the single element sample, in agreement with experiments. We found one of the key mechanisms of this reduction to be the reduced dislocation mobility in the alloys.

]]>Aerosols can be divided into fine and coarse particles based on their size. This thesis concentrated on fine particles, which are either directly emitted into the atmosphere (primary particles) or formed in the atmosphere through gas-to-particle conversion (secondary particles). The main sources of atmospheric fine particles are natural and anthropogenic combustion, industry and secondary aerosol formation (biogenic and anthropogenic).

The overall objective of this thesis was to investigate the chemical composition of fine particles with different temporal and seasonal time-scales. For this purpose, a variety of different sampling techniques, off-line analytical methods and on-line instruments were used to characterise the main chemical species of fine particles in simultaneous and independent campaigns at several sites mainly in southern Finland but also in South Africa. More specific objectives were to investigate the dominant sources of particulate organic matter in the Helsinki area and chemically characterise the fine particles originating from biomass burning. Determining the effect of air mass origin on the chemical composition and concentration of fine particles was also one of the specific aims.

In this thesis, it was found that the chemical composition of fine particles had strong spatial and temporal variation, although on average the mass concentrations of fine particles were quite similar between different sites. The main components in fine particulate matter in southern Finland was particulate organic matter (POM), followed by sulphate, whereas sulphate had the highest contribution to particulate mass in South Africa. Source apportionment analysis of POM revealed clear primary sources from traffic and from biomass burning. However, the secondary organic aerosol had the largest contribution of POM, even though the campaigns were conducted in specific environments such as residential areas where biomass combustion is commonly used or traffic environments. Occasionally, the contribution of biomass burning organic aerosol increased substantially as ambient air temperature decreased. Additionally, simultaneous measurements pointed out a high contribution of common regional or long-range transported sources over large areas of southern Finland. Similarly, the air mass passing over either clean or polluted areas showed a significant effect on the mass concentrations in Finland and South Africa.

]]>In the first article, (non-)amenability of hyperbolic metric spaces is considered. In it, we prove that a uniformly coarsely proper hyperbolic cone of a connected bounded metric space containing at least two points is non-amenable. In particular, this implies that any uniformly coarsely proper visual Gromov hyperbolic space with connected boundary containing at least two points is non-amenable.

In the second article, the degree of amenability of metric measure spaces is considered in general. Here, we prove a homological characterisation of global weighted Sobolev inequalities for quasiconvex uniform metric measure spaces that support a local weak (1,1)-Poincaré inequality using methods from large scale algebraic topology. Returning to the topic of the first article, we show that a quasiconvex visual Gromov hyperbolic uniform metric measure space that supports a local weak (1,1)-Poincaré inequality with a connected boundary containing at least two points satisfies a global Sobolev inequality.

In the third article, fixed point conditions for uniformly bounded group actions on Hilbert spaces are considered. In the article, we establish a spectral condition for the vanishing of the first cohomology group of the complex of square integrable cochains twisted by a uniformly bounded representation of an automorphism group of a 2-dimensional simplicial complex. In particular, if the automorphism group acts properly discontinuously and cocompactly on the complex this implies that every affine action of the automorphism group on the Hilbert space with linear part given by the representation has a fixed point.

In the summary, the results of the articles are further explained and placed in a larger context: mathematically as well as historically.

]]>The dissertation consists of an introductory part and four research articles. In the first article, we present a general randomization procedure for dyadic systems in metric spaces which can be used for constructing both random and adjacent dyadic systems. As an application of the new random systems, we improve the continuity properties of metric wavelets of P. Auscher and T. Hytönen by exploiting the improved ``smallness of boundary'' property of our random cubes. In the third article, we prove some additional properties for our adjacent dyadic systems to prove a decomposition result for dyadic systems in metric spaces. With its help, we give an alternative proof for the quantitative bound of the Lp norm of shift operators acting on vector-valued functions in metric spaces.

In the second article, we explore certain properties of the Muckenhoupt weight classes, the class of Reverse Hölder weights and their weakened versions in spaces of homogeneous type. In the Euclidean setting, the Muckenhoupt weight classes have numerous different equivalent definitions but in spaces of homogeneous type some of those equivalences break down. We show that although certain definitions are no longer equivalent in this context, their weakened versions still define the same weight classes. We also show that every weak Reverse Hölder weight has a self-improving property. In the literature, these types of weak weights appear especially in the theory of partial differential equations.

In the fourth article, we prove quantitative weighted bounds for so called rough homogeneous singular integrals by combining older techniques with a quantitative version of M. Lacey's recent extension of the A2 theorem. The proof of this extension is based on a domination technique which provides a way to dominate Calderón-Zygmund operators pointwise with the help of a finite number of simple sparse operators associated with adjacent dyadic systems.

]]>One of the outcomes of this work was the refinement of the emissions modelling for global-to-mesoscale dispersion model. Firstly, a new parameterisation for bubble-mediated sea salt emissions has been developed by combining and re-assessing widely used formulations and datasets. This parameterisation takes into account the effects of wind speed and seawater salinity and temperature, and can be applicable to particles with dry diameters raging between 0.01 and 10 µm. The parameterization is valid for low-to-moderate wind speed, seawater salinity ranging between 0 and 33 and seawater temperature ranging between -2 and 25 °C. Secondly, the near-real time fire estimation system, IS4FIRES, based on Fire Radiative Power (FRP) data from MODIS, was refined to reduce the overestimation of particulate matter (PM) emissions by including more vegetation types, improving the diurnal variation, removing highly-energetic sources and recalibrating the emission factors. Applying dynamic emission modelling brought more insight to the spatial distribution of these emissions, their contribution to the atmospheric budget, and possible impact on air quality and climate. The modelling shows that sea salt aerosol (SSA) can be transported far over land and contribute up to 6 µg m-3 to PM10 (at annual level), and indicate that the Mediterranean has sharp gradients of concentrations, becoming an interesting area to analyse for climate considerations. For fire, the simulations show the importance of meteorology and vegetation type for the intensity of the emissions. The simulations also show that MODIS FRP is accounting for highly energetic sources as a wildland fire, bringing up to an 80% overestimation in AOD, close to the misattributed sources.

The second outcome is related to urban-scale modelling. The emissions for Helsinki Metropolitan Area (HMA) were revised to bring up-to-date the emissions for traffic and energy sectors in use for urban-scale modelling. The EXPAND model was revised to combine concentrations and activity data in order to compute parameters such as population exposure or intake fraction. EXPAND includes improvements of the associated urban emission and dispersion modelling system, time use of population, and infiltration coefficients from outdoor to indoor air. This refinement showed that PM2.5 in HMA is mainly originated from long-range transport, with the largest local contributors being vehicular emissions and shipping (at harbours and its vicinity). At annual level, the population living mostly indoors (home and work) is mainly exposed to PM2.5 with an acutely increased exposure while commuting.

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