Browsing by Title

The magnetic field of the Earth is 99 % of the internal origin and generated in the outer liquid core by the dynamo principle. In the 19th century, Carl Friedrich Gauss proved that the field can be described by a sum of spherical harmonic terms. Presently, this theory is the basis of e.g. IGRF models (International Geomagnetic Reference Field), which are the most accurate description available for the geomagnetic field. In average, dipole forms 3/4 and non-dipolar terms 1/4 of the instantaneous field, but the temporal mean of the field is assumed to be a pure geocentric axial dipolar field. The validity of this GAD (Geocentric Axial Dipole) hypothesis has been estimated by using several methods. In this work, the testing rests on the frequency dependence of inclination with respect to latitude. Each combination of dipole (GAD), quadrupole (G2) and octupole (G3) produces a distinct inclination distribution. These theoretical distributions have been compared with those calculated from empirical observations from different continents, and last, from the entire globe. Only data from Precambrian rocks (over 542 million years old) has been used in this work. The basic assumption is that during the long-term course of drifting continents, the globe is sampled adequately. There were 2823 observations altogether in the paleomagnetic database of the University of Helsinki. The effect of the quality of observations, as well as the age and rocktype, has been tested. For comparison between theoretical and empirical distributions, chi-square testing has been applied. In addition, spatiotemporal binning has effectively been used to remove the errors caused by multiple observations. The modelling from igneous rock data tells that the average magnetic field of the Earth is best described by a combination of a geocentric dipole and a very weak octupole (less than 10 % of GAD). Filtering and binning gave distributions a more GAD-like appearance, but deviation from GAD increased as a function of the age of rocks. The distribution calculated from so called keypoles, the most reliable determinations, behaves almost like GAD, having a zero quadrupole and an octupole 1 % of GAD. In no earlier study, past-400-Ma rocks have given a result so close to GAD, but low inclinations have been prominent especially in the sedimentary data. Despite these results, a greater deal of high-quality data and a proof of the long-term randomness of the Earth's continental motions are needed to make sure the dipole model holds true.

Soil carbon stocks of arctic regions are globally a remarkable carbon storage and a fundamental component in the global carbon cycle, as they store more than twice the amount of carbon compared to the atmosphere. Environmental controllers and mechanisms behind soil carbon stocks should be comprehensively studied, as there is no clear agreement of the climate change impacts on the sensitive tundra ecosystems and the soil carbon storages. Therefore, there is an urgent need for reliable and extensive soil carbon data to evaluate both local and global impacts of ecosystem changes in tundra regions. Typically, the upscaling of soil organic carbon predictions made in arctic regions has been based totally or partly on vegetation and land cover classifications. This might be one reason why we are lacking a wide view of the potential of using topographical variables in the upscaling of carbon stocks. Even though, the theory has proven a strong indirect relationship between topography and soil properties. Consequently, only variables extracted from a terrain model were used in this study. The aim of the study was to produce as realistic regional soil organic carbon prediction as possible and to investigate the potential of modeling soil organic carbon with topographical variables. Additionally, the variation of soil carbon stocks in relation to the topographical position were examined closely. The landscape scaled subarctic research area located in northern Norway in a mountainous region with relative elevation reaching almost one thousand meters. Hence, the area has a wide range of environmental gradients, which makes it a great area for studying ecological impacts. The research material consisted of field measurements and soil samples of which carbon contents were analyzed in laboratory. Carbon storages were examined against topographical variables extracted from the terrain model using two different multivariate models: generalized additive model (GAM) and generalized boosted regression modeling (GBM). Models were assessed through correlations between observed and predicted values and through model residuals and their root mean square errors (RMSE). Based on the predictive models, soil carbon stocks varied on the research area between 0–34,5 kg C m-2 and the regional mean estimate was 4,2 kg C m-2. These estimates and the regional variation in stocks are in line with earlier inventories made in similar environments. The largest soil carbon stocks were found above the treeline in valleys, at gently sloping hillsides and in local water-logged peatlands. Soil carbon stocks were generally smaller in the mountain birch forest compared to the shrub and heath tundra areas. Local scale variability in carbon stocks were significant and a great portion of total storages was found on a limited area. Above a height of 700 meters, steep topography and harsh climate conditions limits soil formation leaving only barren ground, which explains the low observed carbon storages. Relationships between local topography and soil carbon stocks presented in theory were also recognized in the results of the multivariate models. Absolute height above sea level regulated soil carbon stock especially through the impact on vegetation and temperature conditions. Hence, these mechanisms made up the robust landscape scaled distribution in predicted carbon storages. Instead, soil moisture determined the fine scaled variation. As well, the results indicated soil moistures essential role in soil carbon accumulation. Earlier observations of topographical variables potential in soil carbon prediction modeling are supported by the fairly good models of this research. Nevertheless, large uncertainties are still associated with regional upscaling of soil carbon stocks, which should be paid attention to in future researches to improve the reliability of predictions. A holistic perspective will be necessary to understand the spatial distribution and environmental factors influence on soil carbon storages. Reliable estimations of soil carbon stocks are a key component when determining future climate change impacts and feedbacks as these mechanisms have globally reaching consequences.

The spatial and temporal variations in soil moisture can cause natural hazards, such as droughts and floods. Soil moisture and its mediating environmental factors are fairly unknown from the point of view of climate change, even though climate is a major controlling factor. A significant feedback loop between climate and soil moisture affects various ecosystem processes, especially in the Arctic. Soil moisture is fairly fast and simple to measure in the field, but even so it has not been the subject of comprehensive research. Especially the temporal changes in soil moisture in the Arctic are poorly understood. In low-energy systems, such as Arctic-alpine regions, soil moisture is an important limiting factor for vegetation. This study aims to understand which factors mediate soil moistures spatial variation and temporal change. In addition, one of the objectives of this study is to determine the importance of soil moisture for vascular plant distribution at the landscape scale. The data comprehends 945 individual square meter plots from a 130 km² research area in northern Norway, where relative elevation reaches almost 1000 meters. The variable relief covers a vast range of extreme environmental gradients over short distances, such as a moisture gradient from dry, sun-baked slopes to water-logged peatlands and a vegetation gradient from rugged mountain tops to flood-meadows rich in species. The data consists of in situ field measurements and observations as well as data based on topography, remote sensing and climate models. Factors controlling the spatial variation and temporal change of soil moisture are studied with multivariate models (GLM: Generalized linear model and GAM: Generalizes additive model) at different scales. The importance of soil moisture for vegetation is examined by using four modelling techniques (GLM, GAM, GBM: Generalized boosted regression model, and RF: Random forest) within BIOMOD, an ensemble platform for species distribution modelling. Soil moisture is mediated by various factors, but this research stresses soil properties as the most important variable for the spatial variation in soil moisture conditions. Temporal changes in moisture are mainly controlled by climate factors along with soil properties. Throughout all scales, vegetation, topography, and snow were also proven to be important factors. Vegetation distribution is controlled by soil moisture, as several previous studies have shown. Moisture models based on field measurements as opposed to wetness indices based on topography (SWI: Saga wetness index) turned out to have higher coefficient values. In addition to soil moisture, other soil properties and radiation also control vegetation distribution. The least meaningful factor was shown to be SWI, emphasizing the irreplaceability of field measurements. There are several positive and negative feedbacks between soil moisture and its controlling factors, which need to be addressed when investigating soil moisture. The results of this study are in line with previous studies concerning both moisture controlling factors and soil moisture as a limiting resource for vegetation. The novelty of this study lies in its approach: bringing various spatiotemporal scales together in order to find factors controlling moisture an Arctic landscape. After all, soil moisture is first and foremost controlled by soil properties, but it is also mediated by various factors at different scales.

Arctic and sub-Arctic areas have significant amounts of carbon dioxide and methane stored in the sediments which can affect the climate change. The role of groundwater in the carbon cycle in the northern regions is not well known. The processes related to the groundwater cycle depend on the structure and composition of the sediment, which in turn are determined by the way the sediment is formed.  In this study, the sedimentary structures and the hydrogeological properties of the Haaralamminkangas groundwater system was investigated. The aim was also to obtain more thorough knowledge on the geological processes that have formed the sedimentary structures of the area. Geophysical survey, drilling data, grain size analysis, and water sample analyzes were used as research methods. A sedimentary structure interpretation and 3D model were created from the data. In addition, a conceptual hydrogeological model was produced, which means information about the presence of groundwater in the area, the hydraulic connections of different parts of the groundwatersystem, and how groundwater interacts with surface waters. The 3D model will later serve in the study of the connection between the role of groundwater and the carbon cycle.  The sediments of the area was found to consist of Late Weichelian glacial sediments, fine-grained basin sediments, valley delta sand deposits, sandy gravels of the braded river system, and fine-grained flood sediments. The deposits have been formed in the following main events: Late-Weichelian glacial sedimentary processes, rapid accumulation of a sediment load on the bottom of the river valley and fluvial processes.  In the study, previously unknown information about the thickness of the sedimentary structures in the study area was clarified. Local gravel layers and a possible buried esker system wich was observed in the study may have an effect on groundwater flow. The ground water system was found to extend beyond its present boundaries and a buried bedrock in the middle of the area divides the aquifer into separate parts, where the surface waters from Puukkosuo end up in. Oulankajoki was found to be seeping into the aquifer. The modeling of the change in the height of the Oulankajoki water level showed that the effect of the spring floods is directed towards the areas of Haaralamminranta and Kouruniitty.

Suomen aluerakenteellinen painopiste on muuttunut kaupunkikeskeiseksi. Palvelu- ja tietoyhteiskunta toimii keskittymisetujen mukaisesti jopa enemmän kuin matalamman jalostusasteen teollisuusvaltio. Vanha tasapainoiseen aluerakenteeseen tähdännyt politiikka on väistynyt kaupunkien kehittämisen kautta tapahtuvan yhteiskuntakehityksen tieltä. Perinteinen hyvinvointivaltio on myös väistymässä paremmin globaaliin kilpailuun vastaavan tehokkaamman valtion tieltä. Tässä laajassa kehityskuvassa maaseudun rooli on vähenemässä ja niin tuotannollinen kuin väestöllinen painopiste on siirtynyt yhä suuremmiksi kasvaville kaupunkiseuduille. Yhteiskunta jakaantuu eli polarisoituu. Erityisesti hyvin laajat harvaan asutun maaseudun alueet kärsivät väestökadosta ja jopa pienet maaseutukaupungit ovat vaikeuksissa. Hyvinvointivaltio rakennettiin koko valtion alueelle levittäytyväksi tasapainoiseksi yhteiskunnaksi, jossa palvelut olivat tasapuolisesti kaikkien saatavilla. Tämä kehitys on kuitenkin kääntynyt, palveluita on yksityistetty ja niitä karsitaan niin palvelutasoltaan kuin alueellisesti. Erityisesti maaseutualueet, joilla on vähäinen asukaspohja, kärsivät niukkenevista palveluista. Tämä tutkielma tarkastelee kaupunki- ja maaseutualueiden polarisoituvaa kehitystä Suomessa. Erityistarkasteluun otetaan maaseudun palveluiden säilyttäminen osana alueellista elinvoimaisuutta. Tutkimusmenetelmänä ovat triangulaatioajatuksen mukaisesti alueelliset tilastotarkastelut sekä asiantuntijahaastattelut. Tilastoilla osoitetaan alueellisen kehityksen trendejä ja tulevaisuuden suuntaviivoja. Haastatteluilla pyritään löytämään näkökulmia maaseutualueiden palvelukonseptien kehittämiseksi. Tutkimustuloksina todetaan, että yleisen keskittymiskehityksen mukaisesti myös maaseudun palvelukeskittyminä toimivat kyläkeskukset kasvattavat alueellista rooliaan kuten myös monitoimiset palvelupisteet. Heikkoutena maaseudulla ovat pieni asiakaspohja, pitkät välimatkat sekä näihin suhteutettuna kallis infrastruktuuri. Kasvavina uhkina ovat palveluiden yhä suurempi keskittäminen kuntakeskuksiin erityisesti kuntaliitostilanteissa. Toisaalta pieni asiakaspohja ja maaseudun uudenlainen vetovoima tekevät maaseudusta hyvän kokeiluympäristön uudenlaisille konsepteille, joita ovat erityisesti mobiiliteknologioihin ja paikkatietopalveluihin pohjautuvat palvelut. Nämä palvelut toisaalta vaativat käyttäjiltään yhä suurempaa tietoteknistä osaamista ja oma-aloitteisuutta. Tehokas asiakasryhmien tunnistaminen ja palvelujen optimointi mahdollistavat myös suhteellisen halvan palveluiden järjestämisen. Tasapäistävään aluepolitiikkaan on muuttuvassa hyvinvointivaltiossa tuskin enää paluuta. Maaseutuasuminen tulee saamaan uusia muotoja esimerkiksi monipaikkaisen asumisen muodossa. Palvelut eivät enää tule toimimaan perinteisen kaavan mukaan, vaan ne muuttuvat yhä enemmän pyörien päällä liikkuviksi, sähköisiksi sekä tarpeen mukaisesti räätälöidyiksi. Maaseutuasumiseen on selvästi nähtävissä kasvavaa kiinnostusta. Maaseutu saakin uudenlaisia asukkaita, jotka esimerkiksi pendelöivät kaupunkiin töihin. Maaseutuasumisesta tulee yhä enemmän tietoinen valinta, usein suuren kaupungin vaikutuspiirissä. Näin syrjäisimmät ydinmaaseudun alueet menettävät asukkaita ja myös palveluiden määrä lähes väistämättä vähenee entisestään. Julkisten ja yksityisten palvelutuottajien sekä ammattimaisen ja vapaaehtoisuuteen perustuvan palvelutuotannon välinen raja-aita ovat kaikki murroksessa, mikä tuo tarvetta lisätutkimukselle.

Tässä tutkimuksessa perehdytään CMP-luotauksen teoriaan ja käytäntöön maatutkaluotausten profiililinjojen syvyyskalibroinnissa. CMP-luotaus on Suomessa harvoin käytetty nopeusanalyysimenetelmä ja tutkimuksessa haluttiin selvittää CMP-luotauksen tuomia mahdollisuuksia. Tutkimuskohteet sijaitsevat Etelä-Suomessa, Helsingissä ja Hollolassa. Tutkimuskohteet valikoitiin toisistaan poikkeavan geologian vuoksi. Patolassa metsässä maakerrokset olivat pääosin moreenia ja kalliomaata. Tattarisuon pohjavesialueella kerroksissa vaihtelivat hiekkaiset ja saviset kerrosrakenteet. Hollolan deltamuodostumalla maakerrokset vaihtelivat karkeasta sorasta hiekkaan. Sekä Tattarisuolla että Hollolassa saatiin myös aineistoa pohjavesikerroksesta. Kohteissa tehtiin sekä profiililuotaukset että CMP-luotaukset. Tutkimuksissa hyödynnettiin Malå:n ja GSSI:n maatutkalaitteistoja, joita käyttökokemuksen perusteella vertailtiin myös keskenään. CMP-luotauksella saatuja kerrosnopeuksia verrattiin kohteiden referenssiaineistoihin, keskiarvoiseen 0,1 m/ns:n nopeuteen, taulukkoarvoihin sekä Patolassa hyperbelianalyysin tuottamaan tulokseen. Tulokset olivat rohkaisevia, joskin myös poikkeavia arvoja löytyi. Patolassa haasteena oli moreenin ja rikkonaisen kallionpinnan tunnistaminen profiililuotauksista. Tämä aiheutti hajontaa CMP-luotauksella ja muilla referenssiaineistolla saatujen tulosten välillä. Osa tuloksista oli hyvinkin lähellä referenssiaineistoja, mutta moreeni-kallio-rajapinnan tulkinnan haasteellisuuden vuoksi myös huomattavia poikkeamia saatiin. Tattarisuolla tulkinnan haasteena oli monimutkainen kerrosrakenne ja paikoin profiililuotauslinjoja häiritsevät heijasteet. CMP-luotauksen kerrosnopeudet vastasivat hyvin hiekkaisten kerrosten nopeuksia. Lisäksi CMP-luotauksella voitiin varmistaa luotauslinjalla 2 oleva pohjavesikerros ja että luotauslinjalla 1 pohjavettä ei CMP-luotauksella saatujen nopeuksien perusteella ollut. Hollolassa CMP-luotausaineisto kärsi päällisin puolin huomattavasti häiriösignaaleista. Aineiston prosessoinnin jälkeen saadut kerrosnopeudet vastasivat kuitenkin erinomaisesti referenssiaineistojen kerrossyvyyksiä. Kahden maatutkalaitteiston ja useamman antennikonfiguraation hyödyntäminen profiililuotauslinjoissa mahdollistivat hyvän luotausresoluution niin matalammilla kuin paksummilla kerrospaksuuksilla. Malå:n ja GSSI:n luotauslaitteistot toimivat pääosin hyvin eikä kumpikaan laitteisto ollut selkeästi toista parempi. Tässä tutkimuksessa saadun kokemuksen perusteella CMP-luotauksella voidaan saada merkittävää hyötyä maatutkalinjojen tulkintaan. Kun CMP-luotauksen heikkoudet osataan tunnistaa ja aineiston tulkitsija omaa riittävän hyvän kokemuksen, voidaan CMP-luotauksen avulla tehdyillä syvyyskalibroinneilla saada luotettavia tuloksia tutkimusalueen kerrospaksuuksista.

Several nuclear power plants in the European Union are approaching the ends of their originally planned lifetimes. Extensions to the lifetimes are made to secure the supply of nuclear power in the coming decades. To ensure the safe long-term operation of a nuclear power plant, the neutron-induced embrittlement of the reactor pressure vessel (RPV) must be assessed periodically. The embrittlement of RPV steel alloys is determined by measuring the ductile-to-brittle transition temperature (DBTT) and upper-shelf energy (USE) of the material. Traditionally, a destructive Charpy impact test is used to determine the DBTT and USE. This thesis contributes to the NOMAD project. The goal of the NOMAD project is to develop a tool that uses nondestructively measured parameters to estimate the DBTT and USE of RPV steel alloys. The NOMAD Database combines data measured using six nondestructive methods with destructively measured DBTT and USE data. Several non-irradiated and irradiated samples made out of four different steel alloys have been measured. As nondestructively measured parameters do not directly describe material embrittlement, their relationship with the DBTT and USE needs to be determined. A machine learning regression algorithm can be used to build a model that describes the relationship. In this thesis, six models are built using six different algorithms, and their use is studied in predicting the DBTT and USE based on the nondestructively measured parameters in the NOMAD Database. The models estimate the embrittlement with sufficient accuracy. All models predict the DBTT and USE based on unseen input data with mean absolute errors of approximately 20 °C and 10 J, respectively. Two of the models can be used to evaluate the importance of the nondestructively measured parameters. In the future, machine learning algorithms could be used to build a tool that uses nondestructively measured parameters to estimate the neutron-induced embrittlement of RPVs on site.

Earlier field work in the 1.64 Ga Ahvenisto AMCG (anorthosite-mangerite-charnokite-granite) complex has revealed mafic and felsic magma interaction between hornblende granite and monzodioritic rocks, but a detailed description of this interaction has not previously been presented. In this study field observations, detailed mapping, petrography, geochemistry, and melt viscosity modeling are utilized to provide a comprehensive description of magma interaction processes and the related rock types. Two major mafic and felsic interaction processes, both also observed in the Ahvenisto complex, are mingling and mixing. Mingling is observed in the form of monzodioritic pillows with finger-like granitic veins protruding in them. Mixing is observed as a hybrid rock with monzodioritic groundmass and K-feldspar phenocrysts. The monzodioritic rocks are presumed to represent the last liquids of the mafic magmas of the complex, and the hornblende granite and the granitic veins are presumed to represent the first felsic melts of the granitic intrusion stage. Observed mixing and mingling indicates that these two magmas were, at least partly, liquids simultaneously at the time of intrusion. Petrography and geochemistry reveals at least three different monzodioritic rock types: olivine monzodiorite, ferrodiorite, and monzodiorite. These types represent partial melts of the monzodioritic magma, olivine monzodiorite being the least evolved and monzodiorite the most evolved. The vein granites originate from a more evolved partial melt of the hornblende granite superheated by the coeval mafic magma. Calculated mixing trends and melt viscosities with liquidus temperatures were used to evaluate the magma interaction styles between different rock types. Volatile contents of the two magmas played an important role: the felsic melts most likely contained higher amount of volatiles whereas the mafic melts were relatively dry. Mixing calculations reveal that the hybrid rock was produced by mixing of monzodioritic and hornblende granitic magmas. Mingling occur between ferrodiorite and the vein granites. The least evolved monzodioritic rock, olivine monzodiorite, shows minor interaction only and is probably a close representative of the 'primary' monzodiorite magma of the Ahvenisto complex.

Parkinsonin tauti on yleinen neurodegeneratiivinen sairaus, jossa muun muassa dopaminienergisten hermosolujen kato aivojen mustatumakkeessa johtaa motorisiin oireisiin, joihin kuuluu esimerkiksi liikkeiden hitaus, vapina ja lihasjäykkyys. Tautiin liittyy usein myös muita oireita, kuten kognitiivisia muutoksia, autonomisen hermoston vajaatoimintaa ja uniongelmia. Parkinsonin tautiin johtavat syyt ovat huonosti tunnettu, eikä taudille ole myöskään parannuskeinoa. Tässä tutkielmassa on selvitetty magnetiitti/maghemiittinanopartikkeleiden (MNP) mahdollista yhteyttä Parkinsonin taudin syntyyn. MNP:itä, magneettisia rautaoksideja, on aikaisemmin havaittu ihmisten aivoissa ja muissa kudoksissa. Näillä hiukkasilla voi olla merkittäviä biologisia vaikutuksia ihmisissä niiden hapetus-pelkistysreaktioiden ja magneettisuuden vuoksi, minkä takia niiden epäillään vaikuttavan neurodegeneratiivisten sairauksien syntyyn. Kymmenen Parkinsonin tautia sairastavan potilaan ja kuuden verrokin ihonäytteistä määritettiin magnetiitti/maghemiittinanopartikkeleiden määrä magneettisin menetelmin. Mittauksilla pyrittiin saamaan selville missä määrin ihonäytteet sisältävät magneettista materiaalia, magneettisen materiaalin ominaisuudet, niiden alkuperä sekä mahdolliset erot potilaiden ja verrokkien väillä. Näytteissä havaittiin magneettista materiaalia, jonka ominaisuudet vastasivat magnetiittia/maghemiittia. Tarkkaa alkuperää MNP:ille ei kyetty selvittämään, eikä ryhmien välillä havaittu määrällisiä tai laadullisia eroja MNP:iden suhteen. Jatkotutkimukset etenkin MNP:iden alkuperästä ja niiden roolista Parkinsonin taudin synnyssä voisivat parantaa ymmärrystä Parkinsonin taudista ja auttaa sen hoidon kehityksessä.

In this work, a series of biocompatible nanocomposite hydrogels was prepared by UV-initiated polymerization based on 2-hydroxyethyl methacrylate (HEMA), using ethylene glycol dimethacrylate (EGDMA) as a crosslinker and 2-hydroxymethyl-2-methylpropiophenone as a photoinitiatior, containing liquid crystals of cellulose nanocrystals (CNCs) doped with magnetic nanoparticles. The formation of liquid crystals was achieved thanks to the intrinsic property of CNCs to self-assemble above a critical aqueous concentration. By varying the preparation conditions, allowing different times for phase-separation between the nanoparticles and CNCs and exposing the polymerization mixture to small magnetic field, films with different size and orientation of CNC liquid crystal domains were synthesized. Subsequently, the hydrogel films were studied by dynamic mechanical analysis (DMA) to evaluate the effect of these parameters on the mechanical properties, specifically the Young’s modulus and the ultimate strength. Also, the microstructure of the films was studied via polarized optical microscopy (POM) and scanning electron microscopy (SEM). The water uptake capacity was also analyzed. The results indicate that the presence of cellulose nanocrystals modulates the architecture of the prepared hydrogels. Cholesteric microdomains were embedded in PHEMA matrix and their uniaxial alignment was achieved upon exposure to small static magnetic field, already after several hours. Moreover, structural gradient in the distribution of the liquid crystalline microdomains, in dependence on their size, was obtained within the material. This originated from the direct proportionality between the size and the density of liquid crystals. Finally, it was shown that cellulose nanocrystals act as reinforcing structures of the hydrogels, when the degree of their self-assembly is sufficient, and therefore the resulting hydrogel exhibits both higher resistance to elastic deformation and also higher ultimate strength. Finally, we showed that mechanical performance of these nanocomposites can be enhanced by systematic orientation of the liquid crystalline domains.