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  • Mäkinen, Hannu (Helsingin yliopisto, 2007)
    Genetic studies on phylogeography and adaptive divergence in Northern Hemisphere fish species such as three-spined stickleback (Gasterosteus aculeatus) provide an excellent opportunity to investigate genetic mechanisms underlying population differentiation. According to the theory, the process of population differentiation results from a complex interplay between random and deterministic processes as well historical factors. The main scope in this thesis was to study how historical factors like the Pleistocene ice ages have shaped the patterns molecular diversity in three-spined stickleback populations in Europe and how this information could be utilized in the conservation genetic context. Furthermore, identifying footprints of natural selection at the DNA level might be used in identifying genes involved in evolutionary change. Overall, the results from phylogeographic studies indicate that the three-spined stickleback has colonized the Atlantic basin relatively recently but constitutes three major evolutionary lineages in Europe. In addition, the colonization of freshwater appears to result from multiple and independent invasions by the marine conspecifics. Molecular data together with morphology suggest that the most divergent freshwater populations are located in the Balkan Peninsula and these populations deserve a special conservation genetic status without warranting further taxonomical classification. In order to investigate the adaptive divergence in Fennoscandian three-spined stickleback populations several approaches were used. First, sequence variability in the Eda-gene, coding for the number of lateral plates, was concordant with the previously observed global pattern. Full plated allele is in high frequencies among marine populations whereas low plated allele dominates in the freshwater populations. Second, a microsatellite based genome scan identified both indications of balancing and directional selection in the three-spined stickleback genome, i.e. loci with unusually similar or unusually different allele frequencies over populations. The directionally selected loci were mainly associated with the adaptation to freshwater. A follow up study conducting a more detailed analysis in a chromosome region containing a putatively selected gene locus identified a fairly large genomic region affected by natural selection. However, this region contained several gene predictions, all of which might be the actual target of natural selection. All in all, the phylogeographic and adaptive divergence studies indicate that most of the genetic divergence has occurred in the freshwater populations whereas the marine populations have remained relatively uniform.
  • Kontula, Tytti (Helsingin yliopisto, 2003)
  • Nikula, Raisa (Helsingin yliopisto, 2008)
    This study addressed the large-scale molecular zoogeography in two brackish water bivalve molluscs, Macoma balthica and Cerastoderma glaucum, and genetic signatures of the postglacial colonization of Northern Europe by them. The traditional view poses that M. balthica in the Baltic, White and Barents seas (i.e. marginal seas) represent direct postglacial descendants of the adjacent Northeast Atlantic populations, but this has recently been challenged by observations of close genetic affinities between these marginal populations and those of the Northeast Pacific. The primary aim of the thesis was to verify, quantify and characterize the Pacific genetic contribution across North European populations of M. balthica and to resolve the phylogeographic histories of the two bivalve taxa in range-wide studies using information from mitochondrial DNA (mtDNA) and nuclear allozyme polymorphisms. The presence of recent Pacific genetic influence in M. balthica of the Baltic, White and Barents seas, along with an Atlantic element, was confirmed by mtDNA sequence data. On a broader temporal and geographical scale, altogether four independent trans-Arctic invasions of Macoma from the Pacific since the Miocene seem to have been involved in generating the current North Atlantic lineage diversity. The latest trans-Arctic invasion that affected the current Baltic, White and Barents Sea populations probably took place in the early post-glacial. The nuclear genetic compositions of these marginal sea populations are intermediate between those of pure Pacific and Atlantic subspecies. In the marginal sea populations of mixed ancestry (Barents, White and Northern Baltic seas), the Pacific and Atlantic components are now randomly associated in the genomes of individual clams, which indicates both pervasive historical interbreeding between the previously long-isolated lineages (subspecies), and current isolation of these populations from the adjacent pure Atlantic populations. These mixed populations can be characterized as self-supporting hybrid swarms, and they arguably represent the most extensive marine animal hybrid swarms so far documented. Each of the three swarms still has a distinct genetic composition, and the relative Pacific contributions vary from 30 to 90 % in local populations. This diversity highlights the potential of introgressive hybridization to rapidly give rise to new evolutionarily and ecologically significant units in the marine realm. In the south of the Danish straits and in the Southern Baltic Sea, a broad genetic transition zone links the pure North Sea subspecies M. balthica rubra to the inner Baltic hybrid swarm, which has about 60 % of Pacific contribution in its genome. This transition zone has no regular smooth clinal structure, but its populations show strong genotypic disequilibria typical of a hybrid zone maintained by the interplay of selection and gene flow by dispersing pelagic larvae. The structure of the genetic transition is partly in line with features of Baltic water circulation and salinity stratification, with greater penetration of Atlantic genes on the Baltic south coast and in deeper water populations. In all, the scenarios of historical isolation and secondary contact that arise from the phylogeographic studies of both Macoma and Cerastoderma shed light to the more general but enigmatic patterns seen in marine phylogeography, where deep genetic breaks are often seen in species with high dispersal potential.
  • Leppänen, Jenni (Helsingin yliopisto, 2012)
    One of the main questions in evolutionary biology is what causes genetic differentiation among populations and the origin of new species. In this thesis I studied genetic differentiation of populations by testing how changes in the environment and behaviour have affected populations of Myrmica ants (Formicidae, Hymenoptera). First, I used a phylogeographic approach to find out how climatic changes during and after the last glaciation have affected populations of two Palearctic ant species Myrmica rubra and M. ruginodis. The aim was to locate their glacial refugia and postglacial recolonization routes, and to test whether differences in their cold tolerance and life-history traits have affected their phylogeographic structures and locations of their glacial refugia. Second, I studied the effect of behavioural differences on populations of M. rubra. I examined genetic differentiation and reproductive isolation of an intraspecific microgynous social parasite and its macrogynous host using both genetic and behavioural approaches. The aim was to clarify whether social parasitism as an alternative reproductive tactic may lead to speciation in sympatry. The results of this thesis show that differences in life-history traits have had no effect on the phylogeographic structures of M. rubra and M. ruginodis. Both species have survived the last glaciation in several refugia in Southern Europe but probably also in regions further east and north. Circumstantial evidence suggests that the more cold-tolerant M. ruginodis has survived in refugia more north than M. rubra. Both species have recolonized the northern areas from the south-west and south-east, and probably also from the east. Both genetic and behavioural evidence suggested that in M. rubra the parasite and host are reproductively isolated. They differed substantially in their nuclear DNA, indicating that the parasite is in the process of speciation. However, the mitochondrial lineages of the host and the parasite have not yet diverged. This thesis brings new information on the history of Palearctic insects and the effects of the past environmental changes on their populations. This thesis also clarifies the evolution of social parasitism and provides new evidence for a probable example of sympatric speciation through an alternative reproductive tactic, social parasitism.
  • Knopp, Theresa (Helsingin yliopisto, 2008)
    The ongoing climate change along with increasing levels of pollutants, diseases, habitat loss and fragmentation constitute global threats to the persistence of many populations, species and ecosystems. However, for the long-term persistence of local populations, one of the biggest threats is the intrinsic loss of genetic variation. In order to adapt to changes in the environment, organisms must have a sufficient supply of heritable variation in traits important for their fitness. With a loss of genetic variation, the risk of extinction will increase. For conservational practices, one should therefore understand the processes that shape the genetic population structure and also the broader (historical) phylogenetic patterning of the species in focus. In this thesis, microsatellite markers were applied to study genetic diversity and population differentiation of the protected moor frog (Rana arvalis) in Fennoscandia from both historical (evolutionary) and applied (conservation) perspectives. The results demonstrate that R. arvalis populations are highly structured over rather short geographic distances. Moreover, the results suggest that R. arvalis recolonized Fennoscandia from two directions after the last ice age. This has had implications for the genetic structuring and population differentiation, especially in the northernmost parts where the two lineages have met. Compared to more southern populations, the genetic variation decreases and the interpopulation differentiation increases dramatically towards north. This could be an outcome of serial population bottlenecking along the recolonization route. Also, current isolation and small population sizes increase the effect of drift, thus reinforcing the observed pattern. The same pattern can also be seen in island populations. However, though R. arvalis on the island of Gotland has lost most of its neutral genetic variability, our results indicate that the levels of additive genetic variation have remained high. This conforms to the conjecture that though neutral markers are widely used in conservation purposes, they may be quite uninformative about the levels of genetic variation in ecologically important traits. Finally, the evolutionary impact of the typical amphibian mating behaviour on genetic diversity was investigated. Given the short time available for larval development, it is important that mating takes place as early as possible. The genetic data and earlier capture-recapture data suggest that R. arvalis gather at mating grounds they are familiar with. However, by forming leks in random to relatedness, and having multiple paternities in single clutches, the risk of inbreeding may be minimized in this otherwise highly philopatric species.
  • Lehtonen, Mikko (Helsingin yliopisto, 2013)
    Mosses (Bryophyta) are among the basal embryophytes, which constitute a large part of the photosynthesizing biomass and carbon storage on Earth. Albeit inhabited by a number of fungal species, little is known about how this important portion of flora maintains its health status. Vascular plants (tracheophytes) respond to micro-organisms by the production of reactive oxygen species (ROS), the activation of signaling cascades leading to altered gene expression, protein synthesis and the secretion of extracellular proteins and metabolites. But how do mosses respond to pathogens and pathogen elicitors? The aim of this study was to understand interactions between mosses and fungal pathogens by finding out how the moss Physcomitrella patens responds to a fungal cell wall -derived compound chitosan, which induces defense in vascular plants, by identifying the genes involved in the response and determining their significance against fungal pathogens by creating knockout plants. Chitosan treatment was used to study the production of ROS, extracellular enzyme activity, the expression of defense gene homologs of vascular plants and the changes in the extracellular proteome of P. patens. The resulting information was utilized to generate knock-out moss plants, and since natural pathogens of P. patens are not known, the responses of the knock-out moss plants were tested using fungi isolated from commercially grown Sunagoke moss Racomitrium japonicum. The pathogenicity of these fungi was tested also on selected vascular plants. Chitosan caused the generation of superoxide and a rapid increase in peroxidase activity resulting from a single peroxidase (Prx34) of P. patens. The induction of genes related to oxidative stress and defense signaling was observed. Proteomics studies of extracellular proteins revealed secretion of a large number of proteins in response to chitosan treatment. Fungal infection in P. patens induced the formation of papillae, cell wall reinforcement, chloroplast repositioning, spreading necrosis and a reaction reminiscent of a hypersensitive response. The ΔPrx34 mutants of P. patens were susceptible not only to pathogenic but also to saprophytic fungi. The previously described salt sensitive ΔPpTSPO1 mutants of P. patens, lacking the PpTSPO1 gene involved in mitochondrial tetrapyrrole transport and abiotic (salt) stress tolerance, also showed enhanced susceptibility to fungal infection. Certain fungi including Cladosporium oxysporum and Fusarium avenaceum isolated from disease lesions in Sunagoke moss could also infect P. patens and vascular crop plants. The studies pointed out Prx34 as the first specific host factor that is pivotal for pathogen defense in a bryophyte. PpTSPO1 appears as a new link between abiotic and biotic stress signaling and illustrates the importance of redox homeostasis required for efficient pathogen defense. Analysis of extracellular proteins of P. patens indicates an active basal defense towards fungi and expands the current knowledge of bryophyte secretory proteins. Furthermore, results suggest that mosses and vascular plants may be linked by a common microbial interface consisting of pathogenic fungi. These findings have implications that have gained little previous attention.
  • Wadén, Johan (Helsingin yliopisto, 2010)
    Type 1 diabetes is associated with the risk for late diabetic complications which are divided into microvascular (retinopathy, nephropathy, and neuropathy) and macrovascular (cardiovascular disease, CVD) diseases. The risk for diabetic complication can be reduced by effective treatment, most importantly the glycaemic control. Glycaemia in type 1 diabetes is influenced by the interplay between insulin injections and lifestyle factors such as physical activity and diet. The effect of physical activity in patients with type 1 diabetes is not well known, however. The aim of this thesis was to investigate the physical activity and the physical fitness of patients with type 1 diabetes with special emphasis on glycaemic control and the diabetic complications. The patients included in the study were all part of the nationwide, multicenter Finnish Diabetic Nephropathy (FinnDiane) Study which aims to characterise genetic, clinical, and environmental factors that predispose to diabetic complications in patients with type 1 diabetes. In addition, subjects from the IDentification of EArly mechanisms in the pathogenesis of diabetic Late complications (IDEAL) Study were studied. Physical activity was assessed in the FinnDiane Study in 1945 patients by a validated questionnaire. Physical fitness was measured in the IDEAL Study by spiroergometry (cycle test with measurement of respiratory gases) in 86 young adults with type 1 diabetes and in 27 healthy controls. All patients underwent thorough clinical characterisation of their diabetic complication status. Four substudies were cross-sectional using baseline data and one study additionally used follow-up data. Physical activity, especially the intensity of activities, was reduced in patients affected by diabetic nephropathy, retinopathy, and CVD. Low physical activity was associated with poor glycaemic control, a finding most clear in women and evident also in patients with no signs of diabetic complications. Furthermore, low physical activity was associated with a higher HbA1c variability, which in turn was associated with the progression of renal disease and CVD during follow-up. A higher level of physical activity was also associated with better insulin sensitivity. The prevalence of the metabolic syndrome in type 1 diabetes was also lower the higher the physical activity. The aerobic physical fitness level of young adults with type 1 diabetes was reduced compared with healthy peers and in men an association between higher fitness level and lower HbA1c was observed. In patients with type 1 diabetes, a higher physical activity was associated with better glycaemic control and may thus be beneficial with respect to the prevention of diabetic complications.
  • Borodulin, Katja (Helsingin yliopisto, 2006)
    Physical inactivity, low cardiorespiratory fitness, and abdominal obesity are direct and mediating risk factors for cardiovascular disease (CVD). The results of recent studies suggest that individuals with higher levels of physical activity or cardiorespiratory fitness have lower CVD and all-cause mortality than those with lower activity or fitness levels regardless of their level of obesity. The interrelationships of physical activity, fitness, and abdominal obesity with cardiovascular risk factors have not been studied in detail. The aim of this study was to investigate the associations of different types of leisure time physical activity and aerobic fitness with cardiovascular risk factors in a large population of Finnish adults. In addition, a novel aerobic fitness test was implemented and the distribution of aerobic fitness was explored in men and women across age groups. The interrelationships of physical activity, aerobic fitness and abdominal obesity were examined in relation to cardiovascular risk factors. This study was part of the National FINRISK Study 2002, which monitors cardiovascular risk factors in a Finnish adult population. The sample comprised 13 437 men and women aged 25 to 74 years and was drawn from the Population Register as a stratified random sample according to 10-year age groups, gender and area. A separate physical activity study included 9179 subjects, of whom 5 980 participated (65%) in the study. At the study site, weight, height, waist and hip circumferences, and blood pressure were measured, a blood sample was drawn, and an aerobic fitness test was performed. The fitness test estimated maximal oxygen uptake (VO2max) and was based on a non-exercise method by using a heart rate monitor at rest. Waist-to-hip ratio (WHR) was calculated by dividing waist circumference with hip circumference and was used as a measure of abdominal obesity. Participants filled in a questionnaire on health behavior, a history of diseases, and current health status, and a detailed 12-month leisure time physical activity recall. Based on the recall data, relative energy expenditure was calculated using metabolic equivalents, and physical activity was divided into conditioning, non-conditioning, and commuting physical activity. Participants aged 45 to 74 years were later invited to take part in a 2-hour oral glucose tolerance test with fasting insulin and glucose measurements. Based on the oral glucose tolerance test, undiagnosed impaired glucose tolerance and type 2 diabetes were defined. The estimated aerobic fitness was lower among women and decreased with age. A higher estimated aerobic fitness and a lower WHR were independently associated with lower systolic and diastolic blood pressure, lower total cholesterol and triglyceride levels, and with higher high-density lipoprotein (HDL) cholesterol and HDL to total cholesterol ratio. The associations of the estimated aerobic fitness with diastolic blood pressure, triglycerides, and HDL to total cholesterol ratio were stronger in men with a higher WHR. High levels of conditioning and non-conditioning physical activity were associated with lower high-sensitivity C-reactive protein (CRP) levels. High levels of conditioning and overall physical activities were associated with lower insulin and glucose levels. The associations were stronger among women than men. A better self-rated physical fitness was associated with a higher estimated aerobic fitness, lower CRP levels, and lower insulin and glucose levels in men and women. In each WHR third, the risk of impaired glucose tolerance and type 2 diabetes was higher among physically inactive individuals who did not undertake at least 30 minutes of moderate-intensity physical activity on five days per week. These cross-sectional data show that higher levels of estimated aerobic fitness and regular leisure time physical activity are associated with a favorable cardiovascular risk factor profile and that these associations are present at all levels of abdominal obesity. Most of the associations followed a dose-response manner, suggesting that already low levels of physical activity or fitness are beneficial to health and that larger improvements in risk factor levels may be gained from higher activity and fitness levels. The present findings support the recommendation to engage regularly in leisure time physical activity, to pursue a high level of aerobic fitness, and to prevent abdominal obesity.
  • Hernelahti, Miika (Helsingin yliopisto, 2004)
  • Kaseva, Nina (Helsingin yliopisto, 2014)
    Advancements in neonatal care are resulting in increasing numbers of adult survivors after preterm birth at very low birth weight (VLBW, ≤ 1500 g). VLBW is associated with risk factors of non-communicable diseases, e.g. cardiovascular disease, osteoporosis and diabetes. We investigated mechanisms underlying the effects of preterm birth on later health in VLBW adults, with a focus on 1) physical activity, 2) nutrition and 3) stress response. The participants come from a follow-up cohort study, the Helsinki Study of Very Low Birth Weight Adults. Different subgroups from the original birth cohort (born in 1978-1985) have as young adults participated in the studies of this thesis. The controls, born at term, were group-matched for birth hospital, age and sex. We evaluated physical activity by self-report and objective measurement. The participants completed a physical activity questionnaire and underwent wrist-worn accelerometer measurement. To assess dietary intake, the participants completed a 3-day food record. For evaluation of stress response, the participants underwent the Trier Social Stress Test (TSST). In conjunction with TSST, we measured heart rate, salivary cortisol, plasma ACTH, cortisol, glucose, insulin, adrenalin and noradrenalin. 1) Based on self-report, healthy VLBW adults undertake approximately 50% less conditioning leisure-time physical activity, with lower yearly frequency, total time, total volume and energy expenditure than controls. We were unable to confirm our finding of lower physical activity with wrist-worn accelerometer measurement. 2) VLBW adults had lower consumption of vegetables, fruits, berries and milk products. This was combined with lower intake of calcium and vitamin D. 3) VLBW adults showed a lower hypothalamic-pituitary-adrenal axis (HPAA) response to stress than controls. This was accompanied by a lower insulin response. No evidence of a higher sympathetic-adrenal-medullary (SAM) system stress response was found. Furthermore, we observed a lower noradrenalin response to stress in VLBW women. This study showed that VLBW adults undertake less conditioning leisure-time physical activities and have unhealthier diets, both factors that negatively affect future health in this high-risk population. They may in part underlie the increased risk for chronic non-communicable diseases in VLBW individuals. Further, a lower HPAA response to stress was found in VLBW adults than in controls. For SAM stress response, the results were similar in VLBW and control groups, with lower noradrenalin response to stress in VLBW women only. These findings reinforce the supposition that stress response is programmed early in life. In sum, this study increased understanding of possible mechanisms linking preterm birth and adult risk of disease.
  • Kuisma, Risto (Helsingin yliopisto, 2006)
    Plastic surfaces are a group of materials used for many purposes. The present study was focused on methods for investigation of surface topography, wearing and cleanability of polyvinyl chloride (PVC) model surfaces and industrial plastic surfaces. Contact profilometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM) are powerful methods for studying the topography of plastic surfaces. Although they have their own limitations, they are together an effective tool providing useful information on surface topography, especially when studying laboratory-made PVC model surfaces with known chemical compositions and structures. All examined laboratory-made PVC plastic surfaces examined in this work could be considered as smooth according to both AFM and profilometer measurements because height differences are in the nanoscale on every surface. Industrial plastic surfaces are a complex group of materials because of their chemical and topographical heterogeneity, but they are nevertheless important reference materials when developing cleaning and wearing methods. According to the results of this study the Soiling and Wearing Drum and the Frick-Taber methods are very useful when simulating three-body wearing of plastic surfaces. Both the investigated wearing methods can be used to compare the wearing of different plastic materials using appropriate evaluation methods of wearing and industrial use. In this study, physical methods were developed and adapted from other fields of material research to cleanability studies. The thesis focuses on the methodology for investigating the cleanability of plastic surfaces under realistic conditions, where surface topography and the effect of wear cleanability were among the major topics. A colorimetric method proved to be suitable for examining the cleanability of the industrial plastic surfaces. The results were utilized to evaluate the relationship between cleanability and the surface properties of plastic surfaces. The devices and methods used in the work can be utilized both in material research and product development.
  • Rasa, Kimmo (2011)
    The physical properties of surface soil horizons, essentially pore size, shape, continuity and affinity for water, regulate water entry into the soil. These properties are prone to changes caused by natural forces and human activity. The hydraulic properties of the surface soil greatly impact the generation of surface runoff and accompanied erosion, the major concern of agricultural water protection. The general target of this thesis was to improve our understanding of the structural and hydraulic properties of boreal clay soils. Physical properties of a clayey surface soil (0 - 10 cm, clay content 51%), with a micaceous/illitic mineralogy subjected to three different management practices of perennial vegetation, were studied. The study sites were vegetated buffer zones located side by side in SW Finland: 1) natural vegetation with no management, 2) harvested once a year, and 3) grazed by cattle. The soil structure, hydraulic properties, shrinkage properties and soil water repellency were determined at all sites. Two distinct flow domains were evident. The surface soil was characterized by subangular blocky, angular blocky and platy aggregates. Hence, large, partially accommodated, irregular elongated pores dominated the macropore domain at all sites. The intra-aggregate pore system was mostly comprised of pores smaller than 30 μm, which are responsible for water storage. Macropores at the grazed site, compacted by hoof pressure, were horizontally oriented and pore connectivity was poorest, which decreased water and air flux compared with other sites. Drying of the soil greatly altered its structure. The decrease in soil volume between wet and dry soil was 7 - 10%, most of which occurred in the moisture range of field conditions. Structural changes, including irreversible collapse of interaggregate pores, began at matric potentials around -6 kPa indicating, instability of soil structure against increasing hydraulic stress. Water saturation and several freezethaw cycles between autumn and spring likely weakened the soil structure. Soil water repellency was observed at all sites at the time of sampling and when soil was dryer than about 40 vol.%. (matric potential < -6 kPa). Therefore, water repellency contributes to water flow over a wide moisture range. Water repellency was also observed in soils with low organic carbon content (< 2%), which suggests that this phenomenon is common in agricultural soils of Finland due to their relatively high organic carbon content. Aggregate-related pedofeatures of dense infillings described as clay intrusions were found at all sites. The formation of these intrusions was attributed to clay dispersion and/or translocation during spring thaw and drying of the suspension in situ. These processes generate very new aggregates whose physical properties are most probably different from those of the bulk soil aggregates. Formation of the clay infillings suggested that prolonged wetness in autumn and spring impairs soil structure due to clay dispersion, while on the other hand it contributes to the pedogenesis of the soil. The results emphasize the dynamic nature of the physical properties of clay soils, essentially driven by their moisture state. In a dry soil, fast preferential flow is favoured by abundant macropores including shrinkage cracks and is further enhanced by water repellency. Increase in soil moisture reduces water repellency, and swelling of accommodated pores lowers the saturated hydraulic conductivity. Moisture- and temperature-related processes significantly alter soil structure over a time span of 1 yr. Thus, the pore characteristics as well as the hydraulic properties of soil are time-dependent.
  • Elbra, Tiiu (Helsingin yliopisto, 2011)
    Physical properties provide valuable information about the nature and behavior of rocks and minerals. The changes in rock physical properties generate petrophysical contrasts between various lithologies, for example, between shocked and unshocked rocks in meteorite impact structures or between various lithologies in the crust. These contrasts may cause distinct geophysical anomalies, which are often diagnostic to their primary cause (impact, tectonism, etc). This information is vital to understand the fundamental Earth processes, such as impact cratering and associated crustal deformations. However, most of the present day knowledge of changes in rock physical properties is limited due to a lack of petrophysical data of subsurface samples, especially for meteorite impact structures, since they are often buried under post-impact lithologies or eroded. In order to explore the uppermost crust, deep drillings are required. This dissertation is based on the deep drill core data from three impact structures: (i) the Bosumtwi impact structure (diameter 10.5 km, 1.07 Ma age; Ghana), (ii) the Chesapeake Bay impact structure (85 km, 35 Ma; Virginia, U.S.A.), and (iii) the Chicxulub impact structure (180 km, 65 Ma; Mexico). These drill cores have yielded all basic lithologies associated with impact craters such as post-impact lithologies, impact rocks including suevites and breccias, as well as fractured and unfractured target rocks. The fourth study case of this dissertation deals with the data of the Paleoproterozoic Outokumpu area (Finland), as a non-impact crustal case, where a deep drilling through an economically important ophiolite complex was carried out. The focus in all four cases was to combine results of basic petrophysical studies of relevant rocks of these crustal structures in order to identify and characterize various lithologies by their physical properties and, in this way, to provide new input data for geophysical modellings. Furthermore, the rock magnetic and paleomagnetic properties of three impact structures, combined with basic petrophysics, were used to acquire insight into the impact generated changes in rocks and their magnetic minerals, in order to better understand the influence of impact. The obtained petrophysical data outline the various lithologies and divide rocks into four domains. Based on target lithology the physical properties of the unshocked target rocks are controlled by mineral composition or fabric, particularly porosity in sedimentary rocks, while sediments result from diverse sedimentation and diagenesis processes. The impact rocks, such as breccias and suevites, strongly reflect the impact formation mechanism and are distinguishable from the other lithologies by their density, porosity and magnetic properties. The numerous shock features resulting from melting, brecciation and fracturing of the target rocks, can be seen in the changes of physical properties. These features include an increase in porosity and subsequent decrease in density in impact derived units, either an increase or a decrease in magnetic properties (depending on a specific case), as well as large heterogeneity in physical properties. In few cases a slight gradual downward decrease in porosity, as a shock-induced fracturing, was observed. Coupled with rock magnetic studies, the impact generated changes in magnetic fraction the shock-induced magnetic grain size reduction, hydrothermal- or melting-related magnetic mineral alteration, shock demagnetization and shock- or temperature-related remagnetization can be seen. The Outokumpu drill core shows varying velocities throughout the drill core depending on the microcracking and sample conditions. This is similar to observations by Kern et al., (2009), who also reported the velocity dependence on anisotropy. The physical properties are also used to explain the distinct crustal reflectors as observed in seismic reflection studies in the Outokumpu area. According to the seismic velocity data, the interfaces between the diopside-tremolite skarn layer and either serpentinite, mica schist or black schist are causing the strong seismic reflectivities.
  • Kohout, Tomas (Helsingin yliopisto, 2009)
    Together with cosmic spherules, interplanetary dust particles and lunar samples returned by Apollo and Luna missions, meteorites are the only source of extraterrestrial material on Earth. The physical properties of meteorites, especially their magnetic susceptibility, bulk and grain density, porosity and paleomagnetic information, have wide applications in planetary research and can reveal information about origin and internal structure of asteroids. Thus, an expanded database of meteorite physical properties was compiled with new measurements done in meteorite collections across Europe using a mobile laboratory facility. However, the scale problem may bring discrepancies in the comparison of asteroid and meteorite properties. Due to inhomogenity, the physical properties of meteorites studied on a centimeter or millimeter scale may differ from those of asteroids determined on kilometer scales. Further difference may arise from shock effects, space and terrestrial weathering and from difference in material properties at various temperatures. Close attention was given to the reliability of the paleomagnetic and paleointensity information in meteorites and the methodology to test for magnetic overprints was prepared and verified.
  • Kiilavuori, Kai (Helsingin yliopisto, 2000)
  • Tala, Suvi (Helsingin yliopisto, 2015)
    A central part of the enculturation of new scientists in the natural sciences takes place in poorly understood apprentice master settings: potential expert researchers learn about success in science by doing science as members of research groups. What makes learning in such settings challenging is that a central part of the expertise they are attempting to achieve is tacit: the ideas guiding scientific knowledge-building are embodied in its practices and are nowadays rarely articulated. This interdisciplinary study develops a naturalistic view concerning scientific knowledge construction and justification and what is learned in those processes, in close cooperation with practitioners and by reflection on their actual practices. Such a viewpoint guides developing the expertise education of scientists. Another goal of the study is to encourage science education at every level to reflect as much as possible the epistemological aspects of doing science that practising scientists can also agree upon. The theoretical part of the dissertation focuses on those features of experimentation and modelling that the viewpoints of scientific practices suggest are essential but which are not addressed in the traditional views of science studies and, as a consequence, in science education. Theoretical ideas are tested and deepened in the empirical part, which concerns nanoscience. The developed contextualized method supports scientists in reflecting on their shared research practices and articulating those reflections in the questionnaire and interview. Contrary to traditional views, physical knowledge is understood to progress through the technoscientific design process, aiming at tightening the mutually developing conceptual and material control over the physical world. The products of the design process are both understanding about scientific phenomena and the means to study them, which means constructing and controlling a laboratory phenomenon, created in a laboratory in the same design process that produces the understanding about its functioning. These notions suggest the revision of what exactly is achieved by science and on what kind of basis, which indeed moves the epistemological views of science towards a viewpoint recognizable to its practitioners. Nowadays, technoscientific design is increasingly embodied in simulative modelling, mediating between the experimental reality and its theoretical framework. Such modelling is neither a part or continuation of theorizing as most literature considers modelling, nor it is only a bare means to analyse experimental data, but a partly independent and flexible method of generating our understanding of the world. Because the rapid development of modelling technology alters the evidential basis of science, a new kind of expertise is needed. The entry to the physical reality provided by generative modelling differs epistemologically and cognitively, from traditional methodological approaches. The expertise developed in such modelling provides scientists with new kinds of possibilities. For young scientists success and scientific and technological progress, this expertise is worth understanding.
  • Nousiainen, Maija (Helsingin yliopisto, 2012)
    In physics teacher education the use of graphical knowledge-representation tools like concept maps are often used because they are known to support the formation of organised knowledge. It is widely assumed that certain structural characteristics of concept maps can be connected to the usefulness of content. In order to study this relationship, the concept maps made by pre-service physics teachers are examined here. The design principles of the concept maps are based on quantitative experiments and modelling as the basic procedures in physics concept formation. The approach discussed here is informed by the recent cognitively oriented ideas of knowledge organisation around basic knowledge-organisation patterns and how they form the basis of more complex concept networks. The epistemic plausibility of justifications written in links is evaluated by using a four-level classification introduced here. The new method generalises and widens the existing approaches which use concept maps in representing the learners knowledge, and which also use concept maps for research purposes. Therefore, this thesis presents some novel theoretical constructs for analysis and discusses empirical results by using these new constructs at length, in order to show the advantages which the new theoretical aspects offer. Modelling of the data shows that such a concept-mapping technique supports students conceptual understanding. Also their usefulness in making plans for teaching is identified through modelling the flux of information which the relational structure of the map represents.
  • Puhakainen, Tuula (Helsingin yliopisto, 2004)