Browsing by Title

Sort by: Order: Results:

Now showing items 3162-3181 of 25619
  • Pohjonen, Aarne (Helsingin yliopisto, 2013)
    The work presented in this thesis is related to the design of the future electron-positron collider, called the Compact Linear Collider (CLIC), which is currently under development at CERN. The designed operation of the collider requires accelerating electric field strengths of ∼ 100 MV/m range to reach the target energy range of 0.5 to 5 TeV for the collisions in a realistic and cost efficient way. An important limiting factor of the application of the very high electric fields is the electrical breakdown rate, which has drastic dependence on the accelerating electric field strength E (approximately proportional to E^30 ). In order to achieve material properties capable of tolerating higher electric fields, research on the materials related physical origin of the fundamental cause of electrical breakdown onset needs to be undertaken. The onset stage of the electrical breakdown on a broad area metal surfaces under electric field is still unknown, although many theories have been proposed earlier. In many of the theories, it has been common to postulate the existence of a geometric protrusion on the surface that is capable of causing high field enhancement and pre-breakdown electric currents in the vacuum over metal surfaces under electric field. However, such protrusions have never been seen on the metal surface prior to the breakdown. It has been recently experimentally observed that the average field that the material can tolerate without breakdown is correlated with the crystal structure of the material. This observation hints that some dislocation mechanism could be possibly related to the onset stage of the breakdown event. In this thesis, the following mechanism that can be responsible for the breakdown onset is analyzed. Application of the electric field exerts stress on a metal surface, which can cause the nucleation and mobility of the dislocations, i.e. plasticity. The localized plastic deformation can eventually lead to protrusion growth on the metal surface. Once a protrusion is formed on the surface, the electric field is enhanced on the protrusion site, further enhancing the protrusion growth. A defect such as a void can act as a stress concentrator which changes the otherwise uniform stress field and acts as an initiation site for plastic deformation caused by dislocations. In this thesis, we have examined the effect of an external stress on a near surface void in conditions which are relevant for the research and design of the accelerating structures of the CLIC collider. A void present at a near surface region of the accelerating structure causes local concentration of the stress induced by the external electric field on the conducting metal surface. The presence of such near surface void was experimentally observed in a metal sample prepared for experimental spark setup. By means of molecular dynamics simulation method we have shown that the stress can cause nucleation and/or movement of dislocations near the void. The mobility of dislocations then leads to formation of a protrusion on the material surface. We analyzed the nucleation of the dislocations in detail and constructed a simplified analytical model that describes the relevant physical factors affecting the nucleation event. Since the shear stress on the slip plane causes the mobility and nucleation of the dislocations, we analyzed the stress distribution on the slip plane between the void and surface by using finite element method and by calculating the atomic level stress with molecular dynamics method. The results were compared also to an analytic solution for a void located deep in the bulk under similar stress. It was found that the nearby surface had significant effect on the stress distribution only when the void depth was less than its diameter. Below this the maximum stress is equal to that for a void located deep in the bulk under similar external stress. The comparison of the finite element results to the atomic level stress revealed that the pre-existing surface stress near the void surface had significant effect on the stress distribution. In addition to the tensile stress caused by the electric field on the charged metal surface, pulsed surface heating also induces stress in the material surface region under alternating electric field. This cyclic thermal stress is known to cause fatigue and severe deformation of the metal surface. We investigated the condition relevant for yield by calculating atomic level von Mises strain which has been earlier related to dislocation nucleation. The strain concentration caused by the void was 1.9 times the bulk value. In order to see activated slip planes, we exaggerated the compressive stress to the extent that dislocation nucleation could be observed within the timespan allowed by the molecular dynamics simulation method. Dislocations were observed to nucleate at the sites of maximum von Mises strain. Taken together, the results presented in thesis contribute to the understanding of the stress distributions and possible dislocation related mechanisms under different stressing conditions assuming existence of a stress concentrator, such as a near surface void.
  • Castrén, Sari (Helsingin yliopisto, 2013)
    Disordered gambling is a multifaceted phenomenon, and consequently many factors have a role in its development and maintenance. Adverse consequences of disordered gambling can be mental, social and legal. Only a few epidemiological studies of disordered gambling have previously been conducted in Finland, and none of these studies have been published internationally. Gambling research in Finland has increased during the past years, especially the investigation of treatment options for disordered gambling. In this thesis, disordered gambling is approached from two angles: the epidemiological angle provides an overall picture of the current situation in Finland, and the treatment angle studies the phenomenon from an individual standpoint. In the epidemiological studies of this thesis, the prevalence, socio-demographic characteristics, comorbid substance use, perceived health and well-being and the type of gambling and its relations to the severity levels of gambling were measured. The data were derived from two samples, The Health Behaviour and Health among the Finnish Adult Population, Spring 2010, postal survey (N = 2826) and The Finnish Gambling 2011 (N = 3451), telephone interview. These studies used South Oaks Gambling Screen (SOGS) and Problem Gambling Severity Index as a measure of gambling severity. In the epidemiological studies the prevalence of disordered gambling was found to be about 3% (Finnish Gambling 2011). Disordered gambling was more common among males and the younger age group. Disordered gambling was generally associated with socio-economic disadvantages like being divorced, unemployed or having a low level of education. Comorbid alcohol use and nicotine dependency as well as low self-perceived mental health status were associated with disordered gambling. Lotto (Finnish lottery) was the most popular type of game gambled, but slot machine and internet gambling were found to be associated with disordered gambling. The two treatment studies of this thesis describe the socio-demographic characteristics (N = 471), the severity of disordered gambling, gambling urge, gambling-related erroneous thoughts and the level of control of gambling among the treatment-seeking gamblers. In the treatment studies, comorbid alcohol use and depression were also studied. Moreover, changes in the severity of gambling, gambling urge, gambling-related erroneous thoughts and control of gambling, as well as alcohol use and the level of depression at baseline, post-treatment and 6- and 12-month follow- up were studied. The data were derived from the Peli Poikki program which is an internet-based 8-week cognitive behavioural therapy for gamblers. This study used NORC DSM-IV Screen for Gambling Problems as a measure of gambling severity. Results revealed that 78.8% of the treatment-seeking participants were disordered gamblers. 224 participants completed the treatment and after 8 weeks of treatment a significant decline was seen in gambling-related problems and gambling urge, and an improvement in control of gambling. The mood of participants improved and alcohol use decreased during the treatment period, and participants reported improvements in their social situations after the treatment. In conclusion, the prevalence of disordered gambling has been more or less unchanged during the past years in Finland. A specific socio-demographic group of individuals seems to be at higher risk of having and developing disordered gambling, especially with the abundant gambling opportunities in Finland. The results of the Peli Poikki program encourages implementing more evidence-based treatment options for disordered gambling in Finland.
  • Pylkkänen, Tuomas (Helsingin yliopisto, 2011)
    Spectroscopy can provide valuable information on the structure of disordered matter beyond that which is available through e.g. x-ray and neutron diffraction. X-ray Raman scattering is a non-resonant element-sensitive process which allows bulk-sensitive measurements of core-excited spectra from light-element samples. In this thesis, x-ray Raman scattering is used to study the local structure of hydrogen-bonded liquids and solids, including liquid water, a series of linear and branched alcohols, and high-pressure ice phases. Connecting the spectral features to the local atomic-scale structure involves theoretical references, and in the case of hydrogen-bonded systems the interpretation of the spectra is currently actively debated. The systematic studies of the intra- and intermolecular effects in alcohols, non-hydrogen-bonded neighbors in high-pressure ices, and the effect of temperature in liquid water are used to demonstrate different aspects of the local structure that can influence the near-edge spectra. Additionally, the determination of the extended x-ray absorption fine structure is addressed in a momentum-transfer dependent study. This work demonstrates the potential of x-ray Raman scattering for unique studies of the local structure of a variety of disordered light-element systems.
  • Palin, Eino (Helsingin yliopisto, 2013)
    Mitochondrial dysfunction is a common cause of hereditary neurodegenerative diseases, such as Parkinson s disease and inherited ataxia syndromes. Frequent causes of mitochondrial dysfunction are mutations in mitochondrial DNA (mtDNA) or mutations in the genes encoding the mtDNA replication machinery. Mutations in the gene POLG1, which encodes the catalytic subunit of mitochondrial DNA polymerase, POLG, cause a heterogeneous group of disorders with varying clinical phenotypes, such as mitochondrial recessive ataxia syndrome (MIRAS), progressive external ophthalmoplegia (PEO), PEO with parkinsonism (POLG1-PD) and Alpers syndrome. The cause of variability in the clinical manifestations is unknown and is most evident in POLG1 diseases. In this thesis, we set to elucidate this variability by examining the neuropathological changes in MIRAS, POLG1-PD, IOSCA and PEO. We found that the cell number in substantia nigra correlated well with parkinsonism in POLG1 defects. Respiratory chain complex I defect, however, is a general consequence of mtDNA maintenance defects, and does not explain manifestation of parkinsonism or degree of mesencephalic cell death in patients with mtDNA maintenance disorders. We studied the biochemical background underlying MIRAS by biochemically characterizing the recombinant POLG1, with the MIRAS causing amino acid change, p.Trp748Ser. The recombinant POLG1 does not exhibit a biochemical phenotype in DNA polymerase function. Our findings challenge previously published results and their implications. We examined the distribution of Alpers syndrome causing mutations on the protein structure of POLG1. We found that the mutations can be divided into five distinct groups, each with a different biochemical profile. Our findings were supported by the published biochemical characterizations of various mutant POLG1 enzymes. Based on the structural data, we predict that the p.Trp748Ser amino acid change affects the interaction with mitochondrial single stranded-DNA binding protein and not intrinsic DNA polymerase activity or DNA binding of POLG1. We also studied the clinical picture of MIRAS. The high carrier frequency of the MIRAS disease allele in Finland, Norway and Belgium may lead to multiple introductions of the disease allele and some MIRAS cases to be mistakenly recognised as dominantly inherited, thereby leading to the exclusion of MIRAS as the diagnosis. We described a family in which both mother and son had MIRAS-like disease. We found that the father was a carrier of the MIRAS disease allele. Thus, MIRAS should not be ruled out by an apparently dominant mode of inheritance in countries with high carrier frequency of the disease allele.
  • Saastamoinen, Marjo (Helsingin yliopisto, 2007)
    Most studies of life history evolution are based on the assumption that species exist at equilibrium and spatially distinct separated populations. In reality, this is rarely the case, as populations are often spatially structured with ephemeral local populations. Therefore, the characteristics of metapopulations should be considered while studying factors affecting life history evolution. Theoretical studies have examined spatial processes shaping the evolution of life history traits to some extent, but there is little empirical data and evidence to investigate model predictions. In my thesis I have tried to bridge the gap between theoretical and empirical studies by using the well-known Glanville fritillary (Melitaea cinxia) metapopulation as a model system. The long-term persistence of classic metapopulations requires sufficient dispersal to establish new local populations to compensate for local extinctions. Previous studies on the Glanville fritillary have shown that females establishing new populations are not a random sample from the metapopulation, but they are in fact more dispersive than females in old populations. Many other life-history traits, such as body size, fecundity and lifespan, may be related to dispersal rate. Therefore, I examined a range of correlated traits for their evolutionary and ecological consequences. I was particularly interested in how the traits vary under natural environmental conditions, hence all studies were conducted in a large (32 x 26 m) outdoor population cage built upon a natural habitat patch. Individuals for the experiments were sampled from newly-established and old populations within a large metapopulation. Results show that females originating from newly-established populations had higher within-habitat patch mobility than females from old populations. I showed that dispersal rate is heritable and that flight activity is related to variation in a gene encoding the glycolytic enzyme phosphoglucose isomerase. Both among-individual and among-population variation in dispersal are correlated with the reproductive performance of females, though I found no evidence for a trade-off between dispersal and fecundity in terms of lifetime egg production or clutch size. Instead, the results suggest that highly dispersive females from newly-established populations have a shorter lifespan than females from old populations, and that dispersive females may pay a cost in terms of reduced lifetime reproductive success due to increased time spent outside habitat patches. In summary, the results of this thesis show that genotype-dependent dispersal rate correlates with other life history traits in the Glanville fritillary, and that the rapid turnover of local populations (extinctions and re-colonisations) is likely to be the mechanism that maintains phenotypic variation in many life history traits at the metapopulation level.
  • Järvinen, Zara (2012)
    This thesis is motivated by what some would consider as the erosion, or demise, of nation-state sovereignty today. There is a growing consensus that the nature of sovereignty has changed in the recent decades, as the state as the centrepiece of power and authority is being increasingly affected by forces of globalization and the proliferation of international organizations and institutions. However, the approaches adopted by theorists to confront this perceived crisis of sovereignty seem to be largely divided between those aiming to defend some notion of nation-sate sovereignty, and those aiming to discard it, transform it, migrate or divide it. There is thus an urgent need to re-examine and re-think the concept of sovereignty, and its place and status in today’s politics and political theory. The purpose of this thesis is to contribute to this project through a philosophical analysis of the concept of sovereignty, and the various approaches and conceptualizations present in the modern sovereignty discourse. Especially, the thesis will explore a possibility of re-configuring sovereignty towards a conceptualization that enables it to be dispersed, shared or transferred away from the nation-state to other political units. One such re-configuration is suggested by Thomas Pogge, who promotes a cosmopolitan institutional reform through a vertical dispersal of sovereignty, or a process of decentralization and centralization downwards to local, and upwards to global level - his idea will be critically assessed in detail. The key modern sources adopted in this thesis include: Jacques Maritain’s “The Concept of Sovereignty” (1950); Literature and Evil by George Bataille (1973); Rogues: Two Essays on Reason by Jacques Derrida (2005); “Democracy, Demography and Sovereignty” by Seyla Benhabib (2008); World Poverty and Human Rights by Thomas Pogge (2008); Walled States, Waning Sovereignty by Wendy Brown (2010); and After Sovereignty edited by Pavlich & Barbour (2010). The historical texts considered in this thesis are Polybius’ Histories (264-146 BC); Six Books of the Commonwealth by Jean Bodin (1576); Leviathan by the Thomas Hobbes (1651); and John Locke’s Second Treatise of Government (1689). The main conclusion in this thesis is that through a thorough philosophical analysis of the concept of sovereignty, it becomes evident that sovereignty evades any fixed meanings, and is inherently ambiguous and polysemic. Being polysemic the concept then allows re-configurations and re-conceptualizations that enable conceiving sovereignty as something that can be dispersed, shared or transferred. In addition, such re-conceptualization is further enabled by deliberations and iterations of the concept manifesting in deliberative sovereignty discourse. Throughout the thesis some important considerations and reservations are identified, which will eventually suggest several avenues for further research on the concept of sovereignty.
  • Johansson, Maria (2013)
    Dispersive liquid-liquid microextraction was developed in 2006 for the extraction of organic compounds from water samples. Since then, more complex matrices have been processed and the technique includes nowadays a variety of subsets. To the advantages of the technique are, for example, its rapidity, low cost and high enrichment factors. A pretreatment and analysis method was developed for the five harmful flame retardants, dechlorane plus (syn and anti) and dechloranes 602, -603 and -604 (component A) from solid environmental samples. The pretreatment method included extraction with pressurised liquid extraction and clean-up with multilayer silica and basic alumina columns. The analytes were separated and analysed with gas chromatography coupled to mass spectrometry. Electron capture negative ionisation was applied as the ionisation technique. The developed method was sensitive, resulting in acceptable recoveries and low detection limits. The chosen ionisation technique was proven to be superior over the more used electron ionisation.
  • Wayessa, Gutu Olana (Helsingin yliopisto, 2013)
    The study focuses on population displacement and the livelihood implications of state-planned resettlement schemes that have been implemented in Western Oromia, Ethiopia. It addresses the livelihoods of both the resettlers and the hosts. Although such resettlements have been implemented in the country since the 1960s, this study addresses those carried out since 2003. The broad objective of the study was to explore the dynamics of displacement and resettlement, and their impacts on the livelihoods of resettler and host populations. The specific objectives were: (1) to assess the policies and practices of the resettlement program carried out during the tenure of the current government; (2) to analyze the livelihood outcomes of the resettlements for resettlers and hosts in terms of changes in access to livelihood resources and social services; and (3) to examine resettlers and hosts perceptions of and attitudes towards the resettlement program. The theory of impoverishment risks and livelihood reconstruction (IRLR), the sustainable livelihood framework (SLF), and political ecology constitute the pillars of the theoretical framework. Primary data were collected in 2009 through a survey of 630 households in eight resettlement sites, and 68 thematic (group and individual) interviews in 13 resettlement sites. Several interviews were also held with government officials. Households were selected for the survey through stratified random sampling, whereas informants were selected for the interviews purposively. The primary data were complemented with relevant secondary data. The study is interdisciplinary, and combines both qualitative and quantitative methods through a concurrent mixed-methods design. Qualitative methods were used to address how and why questions through thematic analysis of the interviews and policy documents, thereby illuminating the substantive significance of the issues at stake. Quantitative methods were employed to quantify changes and establish the statistical significance of variables of interest. The quantitative methods used include descriptive statistics, such as percentages, means and cross-tabulations, and inferential statistics, such as logistic regression, mean comparisons using non-parametric tests, factor analysis, Chi-square tests, and loglinear analysis. The complementary relation between the two methods has proved useful in understanding and explaining the processes and the outcomes of the resettlement scheme. The research illuminates the causes, the processes, and the outcomes of the current resettlement program in particular, and critically analyzes the assumptions underlying the resettlement policies of the current and the previous regimes in general. Multiple causes and assumptions underlay the resettlement scheme, most notably land and rainfall shortages in resettlers areas of origin, and the government s claim of land abundance. This last assumption has been persistently made by regime after regime, despite empirical counter-evidence, as also shown in this study. By revealing that the scheme resulted in the displacement of the host population to make way for resettlement, that the resettlers were given less land than promised, and that the relocation led to serious conflicts and disputes over land between resettlers and hosts, the study challenges the state s supposition and rhetoric of ample land. The evidence also illuminates the relocation s glaring lack of inclusiveness of both resettlers and hosts, despite the benign principles of voluntarism and consultation. The outcomes were multiple, leaving some better-off, others worse-off, and still others with no noticeable livelihood deterioration or improvement. In cases where old problems were alleviated, new ones emerged in a context of little plan and capacity to meet contingencies. This calls into question government propagation of generalized success in the resettlement scheme. Although little is known about the sustainability of the improved outcomes for some resettlers in some resettlement sites, the evidence from this study also counteracts the depiction of the scheme as a general failure. The findings suggest that the relative importance of the risks experienced by the resettlers and the hosts varied between the two population groups, and among different resettlement sites. The resettlement sites were widely differentiated in terms of biophysical factors, notably soil fertility and the availability of grazing land. This has serious implications for the resettlers and the hosts as their livelihoods are almost entirely based on agricultural activities. Moreover, historical issues, wider socio-political structures, physical infrastructure, and resettler-host relations are crucial for the understanding of how people s access to livelihood resources and social services is shaped. However, resettler-host relations should be seen in a broader context of state-society relations, as the state is a key actor in planning and implementing the resettlement programs. An important policy lesson from this study is that when one focuses on certain livelihood aspects, one also needs to be aware that other potential livelihood components not evident today may become vital in the future. This awareness should motivate adaptive planning and management to meet contingencies in a way that reflects the multifaceted nature of livelihoods. Key words: displacement, resettlement, livelihood, resettler, host, state, IRLR, SLF, political ecology, mixed methods, resources, processes, outcomes, Oromia, Ethiopia
  • Ylikoski, Petri (Helsingin yliopisto, 1997)
  • Puurunen, Tapio (Helsingin yliopisto, 2005)
  • Kousi, Maria (Helsingin yliopisto, 2012)
    The progressive myoclonic epilepsies (PMEs) are a clinically and etiologically heterogeneous group of symptomatic epilepsies characterized by myoclonus, tonic-clonic seizures, psychomotor regression and ataxia. Different disorders have been classified as PMEs. Of these, the group of neuronal ceroid lipofuscinoses (NCLs) comprise an entity that has onset in childhood, being the most common cause of neurodegeneration in children. The primary aim of this thesis was to dissect the molecular genetic background of patients with childhood onset PME by studying candidate genes and attempting to identify novel PME-associated genes. Another specific aim was to study the primary protein properties of the most recently identified member of the NCL-causing proteins, MFSD8. To dissect the genetic background of a cohort of Turkish patients with childhood onset PME, a screen of the NCL-associated genes PPT1, TPP1, CLN3, CLN5, CLN6, MFSD8, CLN8 and CTSD was performed. Altogether 49 novel mutations were identified, which together with 56 mutations found by collaborators raised the total number of known NCL mutations to 364. Fourteen of the novel mutations affect the recently identified MFSD8 gene, which had originally been identified in a subset of mainly Turkish patients as the underlying cause of CLN7 disease. To investigate the distribution of MFSD8 defects, a total of 211 patients of different ethnic origins were evaluated for mutations in the gene. Altogether 45 patients from nine different countries were provided with a CLN7 molecular diagnosis, denoting the wide geographical occurrence of MFSD8 defects. The mutations are private with only one having been established by a founder-effect in the Roma population from the former Czechoslovakia. All mutations identified except one are associated with the typical clinical picture of variant late-infantile NCL. To address the trafficking properties of MFSD8, lysosomal targeting of the protein was confirmed in both neuronal and non-neuronal cells. The major determinant for this lysosomal sorting was identified to be an N-terminal dileucine based signal (9-EQEPLL-14), recognized by heterotetrameric AP-1 adaptor proteins, suggesting that MFSD8 takes the direct trafficking pathway en route to the lysosomes. Expression studies revealed the neurons as the primary cell-type and the hippocampus and cerebellar granular cell layer as the predominant regions in which MFSD8 is expressed. To identify novel genes associated with childhood onset PME, a single nucleotide polymorphism (SNP) genomewide scan was performed in three small families and 18 sporadic patients followed by homozygosity mapping to determine the candidate loci. One of the families and a sporadic patient were positive for mutations in PLA2G6, a gene that had previously been shown to cause infantile neuroaxonal dystrophy. Application of next-generation sequencing of candidate regions in the remaining two families led to identification of a homozygous missense mutation in USP19 for the first and TXNDC6 for the second family. Analysis of the 18 sporadic cases mapped the best candidate interval in a 1.5 Mb region on chromosome 7q21. Screening of the positional candidate KCTD7 revealed six mutations in seven unrelated families. All patients with mutations in KCTD7 were reported to have early onset PME, rapid disease progression leading to dementia and no pathologic hallmarks. The identification of KCTD7 mutations in nine patients and the clinical delineation of their phenotype establish KCTD7 as a gene for early onset PME. The findings presented in this thesis denote MFSD8 and KCTD7 as genes commonly associated with childhood onset symptomatic epilepsy. The disease-associated role of TXNDC6 awaits verification through identification of additional mutations in patients with similar phenotypes. Completion of the genetic spectrum underlying childhood onset PMEs and understanding of the gene products functions will comprise important steps towards understanding the underlying pathogenetic mechanisms, and will possibly shed light on the general processes of neurodegeneration and nervous system regulation, facilitating the diagnosis, classification and possibly treatment of the affected cases.
  • Sivula, Mirka (Helsingin yliopisto, 2015)
    Disseminated intravascular coagulation (DIC) is common in critically ill patients. Patients with disturbed coagulation develop more organ dysfunction and have higher mortality. The pathophysiology behind the increased morbidity and mortality remains unclear. This study assessed the applicability of diagnostic tools for DIC: a modified score for overt DIC and thromboelastometry (TEM), a viscoelastic coagulation monitor. A further aim was to evaluate matrix metalloproteinase-8 (MMP-8), tissue inhibitor of metalloproteinase-1 (TIMP-1), nucleosomal histone-complexed DNA (hcDNA) and high-mobility group box 1 (HMGB1) protein levels in severe sepsis with disturbed coagulation and to assess their association with organ dysfunctions and outcome. Studies I-IV comprised 769 patients. Study I included 494 unselected critically ill patients in whom the incidence of DIC was studied by a modified score for overt DIC. Study II was a prospective pilot study with 28 patients with severe sepsis and ten healthy controls. TEM analyses were performed on admission to intensive care unit (ICU). Study III contained 22 patients with severe sepsis, in whom serum MMP-8 and TIMP-1 concentrations were measured repeatedly. Study IV was a sub-study of a large, prospective, observational, multicentre study conducted in 17 Finnish ICUs (FINNAKI Study). Admission levels of hcDNA and HMGB1 were analysed from 225 consecutive patients. In the university hospital ICU, incidence of DIC ranged from 31% (I) to over 40% (II, III). A multicentre study revealed a lower incidence (33%) of thrombocytopenia in severe sepsis patients. Components of the score discriminated patients with DIC well; only fibrinogen proved useless. Discriminative power of antithrombin was comparable to D-dimer and prothrombin time ratio. TEM trace was hypocoagulable in DIC patients as compared with other sepsis patients and healthy controls. Clot strength and clot formation parameters discriminated DIC patients well from those without DIC. In all patients fibrinolysis was inhibited. The markers speculated to contribute to coagulation disturbance and organ dysfunction, MMP-8, TIMP-1, hcDNA and HMGB1, were higher in patients with disturbed coagulation. HcDNA and HMGB1 were also elevated in patients with acute kidney injury and adverse outcome. HcDNA was an independent predictor of thrombocytopenia.
  • Müller, Susann (Helsingin yliopisto, 2015)
    Biogeochemical processes in sea ice and the ice-water interface depend on abiotic processes and biological activity. Abiotic processes in sea ice are controlled by the crystallization process of freezing water and the associated formation of saline brine. Also the heat budget of sea ice and the resulting changes in abiotic properties such as porosity and salinity need to be taken into account. The dissolved fraction of sea ice brines contain ions and dissolved organic matter (DOM). Ions are rejected from the ice by diffusion and gravity drainage whereas dissolved organic matter with highly complex and diverse chemical composition can react in many ways with other molecules and surfaces. Hence, the present work compares the behavior of different fractions of DOM to the ones of salts during initial sea ice formation. Controlled tank studies were combined with natural sea ice sampling to exclude the disadvantages of both systems such as the effects of small-scale experiments, artificial additions in tank experiments and the unknown history of natural samples. The studies were conducted with brackish sea ice from the Baltic Sea with its high nutrient and DOM concentrations, but also with oceanic sea ice from the North Sea and the Arctic Ocean. This allows a general conclusion about the behavior of solutes during the formation of sea ice. The present studies indicate that the major seawater ions are significantly fractionated due to differential diffusion and coupled diffuse-convective salt transport through the brine channel network. Ions with a lower diffusivity than Cl¯, in this study SO42¯, Ca+ and Mg2+, remained longer in the brine channel network and got therefore enriched in sea ice relative to Cl¯. K+, on the other hand, diffused faster than Cl¯ and was depleted in sea ice in this study. The behavior of DOM in sea ice was more complex compared to ions because of the complex structure of DOM and the effect of secondary processes on DOM, such as biological production and degradation in sea ice. The quantification of DOM is challenging since only certain fractions such as chromophoric DOM can be measured instead of estimating the total concentration of DOM. Nevertheless, the present studies on DOM in sea ice from Baltic and North Sea water indicated enrichment of DOM compared to sea water ions. The magnitude of this enrichment was higher than expected from diffusion and convection following the transport of salts. The enrichment varied among DOM fractions with highest enrichment of amino-acid like DOM and lowest enrichment of humic-like substances. The results therefore suggest that additional processes, such as selective drainage that depends on the chemical properties of the DOM molecules, affect the enrichment of DOM in sea ice. The optical properties of sea ice were used to develop a bio-optical model. The model estimates the primary production in Baltic Sea ice based on the absorption by particles and chromophoric DOM and the quantum yield for C fixation calculated from photosynthesis-irradiance curves. The results were compared to in situ primary production measurements. The combination of modelled primary production estimates and the measurements of optical properties and primary production in different types of Baltic Sea ice gave a good overview over bio-optical properties in Baltic Sea ice and can be used as a tool to improve different parameters of ecosystem models.
  • Lehecka, Martin (Helsingin yliopisto, 2009)
    Objective: Distal anterior cerebral artery (DACA) aneurysms represent about 6% of all intracranial aneurysms. So far, only small series on treatment of these aneurysms have been published. Our aim is to evaluate the anatomic features, microneurosurgical techniques, treatment results, and long-term outcome in patients treated for DACA aneurysms. Patients and methods: We analyzed the clinical and radiological data on 517 consecutive patients diagnosed with DACA aneurysm at two neurosurgical centers serving solely the Southern (Helsinki) and Eastern (Kuopio) Finland in 1936–2007, and used a defined subgroup of the whole study population in each part of the study. Detailed anatomic analysis was performed in 101 consecutive patients from 1998 to 2007. Treatment results were analyzed in 427 patients treated between 1980 to 2005, the era of CT imaging and microneurosurgery. Long-term treatment outcome of ruptured DACA aneurysm(s) was evaluated in 280 patients with a median follow-up of 10 years; no patients were lost to follow-up. Results: DACA aneurysms, found most often (83%) at the A3 segment of the anterior cerebral artery (ACA), were smaller (median 6 mm vs. 8 mm), more frequently associated with multiple aneurysms (35% vs. 18%), and presented more often with intracerebral hematomas (ICHs) (53% vs. 26%) than ruptured aneurysms in general. They were associated with anomalies of the ACA in 23% of the patients. Microsurgical treatment showed similar complication rates (treatment morbidity 15%, treatment mortality 0.4%) as for other ruptured aneurysms. At one year after subarachnoid hemorrhage (SAH), DACA aneurysms had equally favorable outcome (GOS≥4) as other ruptured aneurysms (74% vs. 69%) but their mortality was lower (13% vs. 24%). Factors predicting unfavorable outcome for ruptured DACA aneurysms were advanced age, Hunt&Hess≥3, rebleeding before treatment, ICH, intraventricular hemorrhage, and severe preoperative hydrocephalus. The cumulative relative survival ratio showed 16% excess mortality in patients with ruptured DACA aneurysm during the first three years after SAH compared to the matched general population. From the fourth year onwards, there was no excess mortality during the follow-up. There were four episodes of recurrent SAH, only one due to treated DACA aneurysm, with a 10-year cumulative risk of 1.4%. Conclusions: The special neurovascular features and frequent association with anterior cerebral artery anomalies must be taken into account when planning occlusive treatment of DACA aneurysms. Clipping of DACA aneurysms provides a long-lasting result, with very small rates of rebleeding. After surviving three years from rupture of DACA aneurysm, the long-term survival of these patients becomes similar to that of the matched general population.
  • Kärkkäinen, Simo (2015)
    Tutkimus keskittyy suomalaisen 1970-luvun rocklehdistön historiaan ja asemaan kotimaisella musiikin kentällä. Musan ja Soundin kirjoituksia on tarkasteltu hyödyntäen Pierre Bourdieun distinktioteoriaa. Tutkielmassa on tarkasteltu aineistossa esiintyviä bourdieulaisia kulttuurikentän erityispiirteitä, distinktion eli erottumisen tapoja sekä kentän sisällä syntyneitä konflikteja. Tutkimusongelmaa on lähestytty seuraavan tutkimuskysymyksen avulla: Millaisia bourdieulaisia distinktioita ja kenttäkonflikteja suomalaisessa 1970-luvun rocklehdistössä ilmenee? Lisäksi on pohdittu, mitä rocklehtien distinktiot ja konfliktit kertovat ympäröivästä yhteiskunnasta ja miten musiikin kenttä mahdollisesti muuttui 1970-luvun kuluessa. Aineisto koostuu Musa- ja Soundi -lehtien vuosikerroista. Ensimmäinen Musa julkaistiin vuonna 1972 ja ensimmäinen Soundi vuonna 1975. Kyseessä ovat ainoat laajalevikkiset suomalaiset rocklehdet tutkitulta ajalta. Musan säännöllinen julkaiseminen alkoi vuoden 1972 heinäkuussa ja loppui 1978. Soundi julkaistiin ensimmäisen kerran vuonna 1975, ja lehti ilmestyy edelleen. Analyysi on rakentunut temaattisesti suuremmasta kokonaisuudesta pienempään siten, että aluksi on käsitelty Suomen rocklehdistön identifioitumista laajalla musiikin kentällä, minkä jälkeen tarkastellaan rocklehtien toimintaa suomalaisella kulttuurin kentällä. Lopuksi käydään läpi Musan ja Soundin välistä konfliktia. Rocklehtien tärkein distinktiomuoto läpi 1970-luvun oli kiistatta autenttisuus. Autenttisuuden muodot olivat Suomessa jokseenkin moninaisia, mutta ne kiteytyvät viime kädessä yleensä epäkaupallisuuteen sekä romanttiseen ihanteeseen itsenäisestä ja vilpittömästä taiteilijasta. Autenttisuuden ihannointimuodot rockin kentällä sekä niihin perustuvat distinktiot syntyivät angloamerikkalaisessa rockkulttuurissa, ja ne periytyivät suomalaiseen rockkirjoitteluun lähes sellaisinaan. Autenttisuutta ihannoimalla rocklehdet erottuivat suomalaisesta vallitsevasta musiikkikentän eliitistä, nuortenlehdistä, toisistaan sekä paikoin ylikaupalliseksi kokemastaan musiikkiteollisuudesta. Konfliktit syntyivät, kun rocklehdet pyrkivät kasvattamaan symbolista pääomaansa ja kyseenalaistamaan kentän eliittiä ja kilpailijoitaan. Konfliktienkin ytimessä oli usein autenttisuuden ihannointi sekä käsityserot autenttisuuden merkityksestä. Rocklehdet ottivat myös näkyvästi kantaa suomalaiseen musiikkipolitiikkaan. Keskeistä rocklehtien kulttuuripoliittiselle kirjoittelulle on pyrkimys muodostaa sukupolvikonflikti, jossa vakiintuneen kentän paradigmaa kyseenalaistetaan oman aseman edesauttamiseksi. Rocklehdet halusivat horjuttaa suomalaisen kulttuurieliitin vakiintunutta asemaa voidakseen itse määritellä legitiimin taiteen ja kulttuurituotteiden ehdot. Lisäksi Musa ja Soundi tekivät distinktioita toisiinsa ja yrittivät saavuttaa valta-asemaa omalla kentällään. Lehtien autenttisuuteen ja epäkaupallisuuteen pyrkiminen heijastelee näkyvästi 1970-lukulaista yhteiskuntaa, joka oli toisaalta hidastuneen talouskasvun leimaama ja jonka musiikkikenttä kuitenkin kaupallistui nopeasti suurten levy-yhtiöiden kasvaessa ja vahvistaessa markkinaosuuttaan. Yhteiskunnan ja populaarimusiikin kehitys koettiin rocklehdissä pitkälti rappiollisena, ja tilanteen pelastajana nähtiin autenttisuuden vaaliminen ja oletetun rahakeskeisyyden hylkääminen.
  • Prause, Istvan (Helsingin yliopisto, 2007)
    Quasiconformal mappings are natural generalizations of conformal mappings. They are homeomorphisms with 'bounded distortion' of which there exist several approaches. In this work we study dimension distortion properties of quasiconformal mappings both in the plane and in higher dimensional Euclidean setting. The thesis consists of a summary and three research articles. A basic property of quasiconformal mappings is the local Hölder continuity. It has long been conjectured that this regularity holds at the Sobolev level (Gehring's higher integrabilty conjecture). Optimal regularity would also provide sharp bounds for the distortion of Hausdorff dimension. The higher integrability conjecture was solved in the plane by Astala in 1994 and it is still open in higher dimensions. Thus in the plane we have a precise description how Hausdorff dimension changes under quasiconformal deformations for general sets. The first two articles contribute to two remaining issues in the planar theory. The first one concerns distortion of more special sets, for rectifiable sets we expect improved bounds to hold. The second issue consists of understanding distortion of dimension on a finer level, namely on the level of Hausdorff measures. In the third article we study flatness properties of quasiconformal images of spheres in a quantitative way. These also lead to nontrivial bounds for their Hausdorff dimension even in the n-dimensional case.