Väitöskirjat

Recent Submissions

  • Tarvasmäki, Tuukka (Helsingin yliopisto, 2017)
    Acute heart failure (AHF), one of the most common reasons for hospitalizations, is associated with high mortality. Its management is challenging and should be tailored according to different clinical manifestations that range from less severe hypertensive AHF to the most severe form, cardiogenic shock (CS), with its extremely poor prognosis. Acute coronary syndrome (ACS) precipitates over one-third of AHF (ACS-AHF) cases. The aim of this thesis is to analyze current real-life AHF management, with emphasis on vasoactive therapies, in relation to different AHF clinical presentations and specifically CS. In addition, the study targets for characterization two poorly described clinical pictures: 1) ACS-AHF and 2) CS complicated by acute kidney injury (AKI), a common organ injury in the critically ill. Data from two independent prospectively collected patient cohorts in this thesis comprise the FINN-AKVA (Finnish Acute Heart Failure) study, which is a national multicenter study including 620 patients hospitalized for AHF, and the European multicenter CardShock study including 219 patients with CS. Furosemide was the most common therapy for AHF regardless of clinical presentation, often administered even during the initial CS phase. Other intravenous medications and non-invasive ventilation varied according to the AHF clinical picture of AHF. Systolic blood pressure (SBP) was one of the main predictors of AHF-therapy utilization. Considering previous and current European guideline recommendations, use of nitrates was rather low, especially in hypertensive AHF. Compared with AHF patients without concomitant ACS (nACS-AHF), ACS-AHF manifested as a more severe clinical presentation and more frequently as de novo AHF. Guideline-recommended AHF therapies and invasive coronary procedures were more frequent in ACS-AHF. However, angiography (35%) and revascularization (percutaneous coronary intervention 16% and coronary artery bypass graft surgery 10%) rates were low. ACS-AHF was associated with higher 30-day mortality than was AHF without concomitant ACS (13% vs 8%). Use of vasopressors and inotropes was rather frequent in patients without shock, especially in pulmonary edema, and in ACS-AHF as well. They were used almost invariably in CS, noradrenaline being the most common vasopressor and dobutamine the inotrope of choice. Adrenaline was associated not only with excessive cardiac but also with 90-day mortality. In turn, noradrenaline combined with either dobutamine or levosimendan was associated with a more positive prognosis; these two combinations appeared to be alternatives with equivalent outcomes. Patients with CS frequently developed AKI during their first 48 hours of shock, but incidence varied by definition. The AKI definition based on urine output (UO) seemed rather liberal compared with one based on creatinine or on cystatin C (CysC). In addition, creatinine- and CysC-defined AKIs were independently related to higher 90-day mortality, whereas the UO-based AKI definition was not. A stricter cutoff of <0.3 mL/kg/h for average UO during a 6-hour period was more accurate in mortality prediction. AKI was correlated with findings of arterial hypotension, low cardiac output, and venous congestion. This study raises questions as to how well the AHF guidelines and recommended therapies are implemented in clinical practice. In addition, the study describes the clinical importance of ACS in AHF and of AKI in CS.
  • Jukarainen, Sakari (Helsingin yliopisto, 2017)
    Subcutaneous adipose tissue (SAT) dysfunction has been theorized to drive some of the effects of obesity on metabolic health. Sirtuin (SIRT) proteins and their activity have recently been proposed as possible mediators of subcutaneous adipose tissue dysfunction in obesity. SIRTs are NAD+-dependent deacylases that regulate various cellular functions (e.g. transcription factors) according to cellular energy levels, as reflected in the availability of intracellular NAD+. There are numerous animal studies manipulating SIRT and NAD+ biology, which together seem to show that increasing SIRT activity promotes metabolic health (e.g. insulin sensitivity), whereas reducing SIRT activity has the opposite effect. Thus, the focus of Study I, comprising a sample of healthy Finnish genetically identical monozygotic twins (MZ), was to determine whether obesity is associated with SAT SIRT and NAD+ synthesis gene expression and how SAT SIRT expression is associated with measures of SAT inflammation and systemic insulin resistance. The genetically informative sample of MZ twins was used to exclude possible confounding by genetic and early environmental factors in these associations. The purpose of Study II, a Finnish longitudinal weight loss intervention study on unrelated individuals, was to further examine how SAT SIRT and NAD+ synthesis gene expression respond to weight loss. Our results from these studies suggest that SAT expression of SIRT and NAD+ synthesis genes is reduced by long-term acquired obesity and increased during weight loss, effects that are not confounded by genetic or early environmental factors. Obesity itself might not be the factor driving metabolic disease, although several studies show associations between obesity and metabolic dysregulation. Poor cardiorespiratory fitness (CRF) has been suggested as an alternative explanation to the metabolic dysregulation observed in obese individuals. Moreover, differences in CRF between obese individuals has been hypothesized to explain why not all obese individuals exhibit metabolic dysregulation. Some authors have even made the assertion that if CRF is taken into account the association between obesity and increased mortality disappears. The focus of Study III, an analysis of one Finnish and one Danish twin sample, was to determine whether obesity or CRF best explains poor metabolic health. After controlling for confounding by genetic and early shared environmental factors, the results suggest that obesity is strongly associated with the studied metabolic health variables (e.g. insulin sensitivity, metabolic syndrome traits), whereas CRF, defined through maximal oxygen uptake, is only very weakly or not at all associated with metabolic health.
  • Lantto, Tiina A. (Helsingin yliopisto, 2017)
    Plant phenolics and extracts are able to affect cell signalling associated with regulated cell-death mechanisms. Such mechanisms play a crucial role in the normal homeostasis of an organism, but inadequately functioning cell-death machinery is a component of the development of complex diseases, such as cancer, where cells divide in an uncontrolled manner. Apoptosis is the most studied regulated cell-death mechanism associated with cancer. One of the key triggers of and contributors to apoptotic cell death is a tumour suppressor p53. This protein is constantly produced, though it is activated only by several cellular stress responses, such as endoplasmic reticulum stress. The purpose of this study is to investigate the cytotoxic and apoptotic properties of three plant phenolics – curcumin, resveratrol and quercetin – and seven plant extracts – basil, juniper, laurel, lemon balm, parsley, and Siberian pine – in cancerous neuroblastoma and melanoma, and non-cancerous fibroblast cell models. The emphasis of the work is on plant extracts due to their claimed additive or synergistic effects on cellular mechanisms. The effects of different treatments are determined by two cell-viability tests, followed by Western blot assays of the amounts of p53, anti-apoptotic Bcl-2, and inflammatory p65. Apoptotic events are defined by the activity of caspase 3 and DNA fragmentation. Further testing to reveal a broader spectrum of effects is defined by the cDNA RDA method in order to investigate genes expressed differently in treated and in untreated cells. The results of this study support existing knowledge of the effects of single-plant phenolics, and reveal new mechanisms for the activity of plant extracts. Possible synergistic or additive effects of juniper plant extract on apoptosis through endoplasmic reticulum stress are observed. Plant phenolics and extracts may provide a unique pool of drug candidates for the prevention or treatment of cancer. The use of plant extracts as drug candidates is especially interesting due to the possible synergistic or additive effects they achieve at low concentrations.
  • Kuivanen, Suvi (Helsingin yliopisto, 2017)
    Flavivirus is a genus that consists of small RNA viruses transmitted by arthropod vectors, mosquitos and ticks. Flaviviruses cause human diseases of global concern, such as dengue fever, Yellow fever, West Nile disease and Japanese encephalitis, with hundreds of millions of infections every year. Zika virus (ZIKV), a mosquito-borne flavivirus, recently caused a major epidemic with severe and unexpected consequences. Circulating in sylvatic cycles for decades and traditionally causing only mild self-limiting disease, ZIKV quickly spread through the Americas between 2015 and 2016, leading to an unforeseen epidemic that affected hundreds of thousands of people. Following this outbreak of acute ZIKV infections, the number of microcephaly cases reported in neonates accumulated; a causal relationship was suspected and the World Health Organization declared a Public Health Emergency of International Concern in February 2016. We were able to provide a key piece of evidence in proving the causal relationship between ZIKV infection and microcephaly. We described a case of prolonged maternal viremia from an expectant mother infected with ZIKV at the 11th week of gestation, which led to brain damage in the fetus. Subsequently, we isolated the virus FB-FWUH-2016 from the brain tissue of the fetus in human neuroblastoma cells. There is no specific anti-viral treatment for ZIKV infections nor is there a fully effective vaccine. Thus, we screened several anti-cancer compounds known to possess anti-viral activities to determine their anti-Zika virus effectivity. We found that gemcitabine, saliphenylhalamide and obatoclax, the latter of which is a novel compound, inhibited ZIKV replication and virus production in retinal pigment epithelial cells. Furthermore, we found that the compounds differentially affect the metabolism of infected cells. These data provide novel information for anti-virus drug development, as these compounds affect the functions of infected cells instead of the virus itself. We further characterized the new epidemic virus isolate and conducted a study on cell tropism. In this study, we compared four ZIKV isolates, three of which were from the epidemic Asian lineage and the other was a prototypic virus of the African lineage. We found differences in cell susceptibility that favored the new strain and a closely related French Polynesian strain, particularly in cell lines originating from the placenta, umbilical veins, kidney and brain. Tick-borne encephalitis virus (TBEV), another flavivirus that affects the central nervous system, is endemic in many parts of Europe and in the Northern parts of Asia. Three subtypes of the virus, namely, the European, Siberian and Far Eastern subtypes, can cause encephalitis with different degrees of severity. The European subtype is most prominent in most of Europe, but the Siberian subtype is also found in the Baltic countries and Finland. Fatalities are rare, which made the Kotka Archipelago in Finland a new focus after the report of two fatal TBE cases in 2015 from the same island in the archipelago along with two other infected individuals. We isolated the virus from the brain of one of the deceased patients in human neuroblastoma cells and obtained sequence data on both fatal cases. Surprisingly, the viruses were the Siberian and European subtypes. During this and previous studies, we also found both viruses in ticks from the archipelago, which shows that the subtypes coexist in the same focus.
  • Venäläinen, Satu (Helsingin yliopisto, 2017)
    Public discourse tends to position women who have committed crimes of violence as deviant ‘others’ who transgress gendered expectations about proper womanhood. This othering is commonly linked with tendencies to make sense of violence committed by women in stereotypical and reductionist terms. This dissertation analyses the construction of women as perpetrators of violence in both crime news in the tabloid press and the narratives of women imprisoned for violent crimes. By approaching the topic through different sets of research materials, and by integrating a variety of perspectives and analytical approaches, the dissertation opens up new ways of conceiving gendered dynamics of violence and, in particular, the relations between women and violence. Theoretically and methodologically the dissertation draws primarily upon feminist poststructural theorizations and critical discursive psychology, and is focused on ways in which meanings attached to gender and violence entwine with processes of being identified and identifying oneself within socio-cultural intelligibility. The dissertation comprises four sub-studies, two of which focus on analyses of tabloid news reports and the other two on the narratives of women serving a prison sentence. Sub-study I investigates how relations between gender categories and violence are constructed, and how notions about gender are drawn upon in making sense of lethal intimate partner violence in tabloid news reports. Sub-study II explores the ways in which women’s violent action is made sense of in terms of agency and the constitution of identities in the reports. Sub-study III focuses on the ways in which imprisoned women negotiate their positionings and identities in relation to culturally circulating conceptions about womanhood and violence. Finally, sub-study IV focuses on meanings attached to violence in the imprisoned women’s narratives, and on the discursive and affective processes through which those meanings entwine with the enactments of selves. Overall, the analyses illustrate different, context-specific ways in which femininity is referred to and drawn upon in positioning women in relation to violence in both tabloid news and in imprisoned women’s narratives, and shed light on the gendered ambivalences and paradoxical socio-cultural valuations and expectations that femininity entwines with. The analyses also show multiplicity in the meanings attached to violence perpetrated by women, while pointing to the specific prevalence of individualistic modes of meaning-making that emphasize individual agency. While such an emphasis tends to tie violence to the character of women suspected of violence and deepen their deviance in the tabloid news, in the imprisoned women’s narratives it frequently appears as a means for defending against otherness and gendered vulnerability. The dissertation contributes to the development of approaches to exploring relations between gender, womanhood and violence that accommodate complexity and thus work against dichotomies and reductionism. Furthermore, it charts theoretical and methodological experimentation that combines an interest in discourse and affects, and facilitates the viewing of social-psychological practices of gendered identification as both adaptive and patterned.
  • Rosenqvist, Johanna (Helsingin yliopisto, 2017)
    Neurocognitive functions, such as attention/executive functions, language, memory/learning, sensorimotor functions, social perception, and visuospatial processing, gradually develop as a child grows. This happens following brain maturation, but also in close relationships with the environment and background of the child. The aim of the present thesis was to explore the relationship among background and environmental variables and neurocognitive performance in typically developing children. The present thesis consists of three empirical studies exploring the relationships among background, environmental, and neurocognitive variables. Study I compared the cross-sectional development of neurocognitive functions among 2,745 children from Finland, Italy, and the United States, aged 3–15, thus investigating the relationship between cultures and neurocognition. Study II investigated the relationship between media use—that is, time spent watching television (TV), using the computer, or reading—and neurocognitive functions in 381 children, aged 5–12 years, from the United States. Study III investigated more closely one neurocognitive function—the ability to recognize emotional expressions—in 370 3–6-year-old Finnish children. The developmental sequence of the function, as well as its relationship with other neurocognitive functions, was explored. In all three studies, standardization data from the comprehensive and international child neuropsychological assessment, NEPSY-II, was used. Neurocognitive performance proved to be related to all the assessed variables in all three studies. Cultural differences emerged for most neurocognitive functions, especially in younger children, with somewhat different developmental pathways in the three countries. Media use was also significantly related to neurocognitive performance. TV watching was negatively related to neurocognition, while computer use was positively related to some neurocognitive functions. Reading was positively related to some functions in younger children and when maternal education was lower. The emotion recognition ability showed a specific developmental pattern in preschool-aged children and proved to be related to other neurocognitive functions, especially language. In all, the findings of the present thesis suggest that neurocognitive functions develop in close relation with the environment and background of the child. Cultural and media use habit differences, in addition to age and parental education level, may explain some of the variation in neurocognitive performance appearing during pediatric clinical assessments. Further, deficits in neurocognitive functions may partly explain deficits in other functions, for example, emotion recognition ability. The present findings have implications for families and assessments of children. One specific implication involves guidelines for assessing English- and Swedish-speaking children in Finland. In all, the thesis adds new information to the neuropsychology research fields of cultural, media, and social function studies.
  • Pietikäinen, Kaisa Sofia (Helsingin yliopisto, 2017)
    This dissertation investigates English as a lingua franca (ELF) in intercultural romantic relationships. The study attempts to unveil how ELF couples succeed in lingua franca communication: What do their interactions reveal about their pragmatic strategies concerning multilingualism, understanding, and silence, and how do they view their language identity? The data consists of 9h 9min of semi-structured interviews from six couples and 24h 15min of naturally occurring conversations recorded by seven couples. I use conversation analysis (CA) throughout, although the interview data has also undergone content analysis. The results concerning multilingual practices indicate that ELF couples utilise their multilingual repertoires frequently and for a range of interactional purposes, but also for no apparent reason. This implies that translanguaging within the speakers’ shared range diminishes in interactional value over time and becomes a habituated part of the “couple tongue”. The frequency of misunderstanding in ELF couple talk is generally in line with previous findings in ELF, but the closeness of the partners is a factor which both helps them understand each other, yet also causes misunderstandings because they expect to understand each other so easily. ELF couples use a vast array of understanding-enhancing practices similarly to ELF speakers in other contexts, but they also resort to extra-linguistic means such as drawing and onomatopoeia. The ELF couple identity is negotiated and shaped by their shared experiences over time. In this shaping process, the languages the couples use, including but not limited to English, become meaningful as the core around which the shared practice is built. ELF couples identify as English-speaking couples, but multilingualism is also present in their everyday life in their language practices at home and with the surrounding community. In their conflict interactions, ELF couples orient to noticeable silences as indicating troubles extending beyond disagreements. In addition to indicating a strong disagreement, withholding a response at a transition-relevance place is treated as marking avoidance of self-incrimination, resisting an inappropriate change-of-footing, taking offence, or unsuccessful persuasion. Applying CA to investigating turns that follow noticeable silences is found to be an effective methodology for examining the local inferences of noticeable silences. In sum, the findings imply that contextual factors such as the intimacy of ELF speakers and their shared history affects their pragmatic strategies; e.g., speakers in family contexts translanguage more freely and use more varied pre-emptive practices to avoid problems of understanding than ELF speakers in more transient contexts. Also, ELF partners identify as English speakers in their own right, and their naturally occurring talk is found to be valid for conversation analytic inquiry of interaction proper. The dissertation attempts to stimulate mutual understanding between ELF research, multilingualism, and CA.
  • Hellas, Arto (Helsingin yliopisto, 2017)
    The introductory programming course is one of the very first courses that computer science students encounter. The course is challenging not only because of the content, but also due to the challenges related to finding a place in a new community. Many have little knowledge of what to expect from university studies, some struggle to adjust their study behavior to match the expected pace, and a few simply cannot attend instruction due to e.g. family or work constraints. As a consequence, a considerable number of students end up failing the course, or pass the course with substandard knowledge. This leads to students failing to proceed in their studies at a desirable pace, to students who struggle with the subsequent courses, and to students who completely drop out from their studies. This thesis explores the issue of retention in introductory programming courses through multiple viewpoints. We first analyze how the teaching approaches reported in literature affect introductory programming course pass rates. Then, changes on the retention at the University of Helsinki are studied using two separate approaches. The first approach is the use of a contemporary variant of Cognitive Apprenticeship called the Extreme Apprenticeship method, and the second approach is the use of a massive open online course (MOOC) in programming for recruiting students before they enter their university studies. Furthermore, data from an automatic assessment system implemented for the purposes of this thesis is studied to determine how novices write their first lines of code, and what factors contribute to the feeling of difficulty in learning programming. On average, the teaching approaches described in the literature improve the course pass rates by one third. However, the literature tends to neglect the effect of intervention on the subsequent courses. In both studies at the University of Helsinki, retention improved considerably, and the students on average also fare better in subsequent courses. Finally, the data that has been gathered with the automatic assessment system provides an excellent starting point for future research.
  • Tjahjadi, Mardjono (Helsingin yliopisto, 2017)
    Objective Vertebrobasilar (VB) aneurysms remain considered as a significant challenge for both microneurosurgical and endovascular neurosurgeon/interventional neuroradiologists. The nature of the aneurysm formation and growth, as well as the tortuosity and geometry of the vessels in many cases, has reduced the efficacy of final clinical and radiological outcome of endovascular therapy. On the other hand, microsurgical treatment for VB aneurysms has also been reported to have a relatively high morbidity and mortality rate. The need to effectively treat the VB aneurysms was essentially based on the clinical fact that they have a higher rupture rate and worse prognosis than the anterior circulation group. Reducing the morbidity and mortality rate while increasing the aneurysm occlusion rate and its durability is the ultimate goal of aneurysm treatment. Our aim is to evaluate simple surgical techniques and their clinical and radiological results that have been used to treat VB aneurysms in department of neurosurgery of University of Helsinki and Helsinki University Hospital. Patients and Methods We analyzed surgical techniques that have been used in department of neurosurgery of University of Helsinki and Helsinki University Hospital during ten year period. The pre-operative clinical scale and final clinical and radiological outcomes were assessed to evaluate the efficacy of the surgical approaches. We used a defined subgroup of the surgical corridors into anterolateral, lateral, and posterolateral corridors to treat five levels of VB aneurysms. The five levels of VB aneurysms were divided based on their level to the clivus bone, which are above, upper, middle, lower, and lowermost. Results Above clivus level of VB aneurysm defined as more than 6 mm above the posterior clinoid process (PCP) was effectively treated by LSO approach, a simple modification of pterional approach which has anterolateral surgical corridors. Specifically for BB aneurysm, the wide P1 (first segment of PCA) angle was also a determined factor for the selection to use LSO. Upper clivus level defined as within 6 mm above and 8 mm below the PCP was simply treated with a subtemporal approach,at a lateral corridor to reach the lesion. This approach was a workhorse to treat theupper clivus level aneurysm because of shorter distance, more “straight to the point,”and better visibility of posterior basilar perforators. Middle clivus level aneurysms,defined as more than 8 mm below the PCP to the level of internal acoustic meatus (IAM) were commonly treated with a simplified presigmoid approach. This posterolateral corridor offered a wider and better exposure of VB artery and its surrounding neural structures. VB aneurysm which is located at lower clivus level, defined as more than 10 mm above the foramen magnum to the level of IAM, was effectively treated with simple lateral suboccipital approach or tic craniotomy. If the aneurysm is located very low or defined as less than 10 mm above the foramen magnum, a modification called “enough-lateral” approach was recommended. Conclusion These five simple surgical approaches (LSO, subtemporal, presigmoid, lateral suboccpital, and “enough-lateral”) were effective approaches to treat five different levels of VB aneurysm according to the clivus bone. The pre-operative clinical gradingscale and the large – giant size of aneurysm were the most consistent and determinant factors for unfavorable outcome in this study.
  • Mäkelä, Noora (Helsingin yliopisto, 2017)
    Cereal (1→3)(1→4)-β-D-glucan, known as β-glucan, has both technological and physiological functionality related to its ability to increase viscosity in solutions. The viscosity is dependent on the molar mass, concentration and solubility of β-glucan, and thus any degradation during processing and storage may diminish its functionality. Quite recently, chemical oxidation was shown to be one factor leading to the degradation of β-glucan. The present study aimed to investigate the hydroxyl radical-mediated oxidation of cereal β-glucan, including the pathways and reaction products. Additionally, oxidised lipids were tested as a source of radicals in β-glucan oxidation. Finally, the physicochemical properties (e.g. aggregation and gelation) were studied in order to understand the influence of oxidation on functionality. Hydrogen peroxide was shown to be the strongest oxidant, leading to both oxidative degradation and the formation of oxidised groups (e.g. carbonyl groups) within the chain. Additionally, oxidation of reducing end glucose units led to the formation of arabinose and formic acid. With ascorbic acid the oxidation was milder and mostly scission of β-glucan occurred. This difference was also seen in the aggregation behaviour, with very large but densely packed aggregates being formed when oxidising β-glucan with hydrogen peroxide. With ascorbic acid, fewer aggregates were formed and they could not be separated from single oxidised molecules during field-flow fractionation. This finding suggests the formation of cross-links via the oxidised groups in the molecules. The study showed for the first time that cereal β-glucan can be degraded by radicals from lipid oxidation although the oxidative degradation was significantly milder than with hydrogen peroxide. The gelation of cereal β-glucan has been shown to be affected by the molar mass and structure (e.g. the ratio of DP3 and DP4 units) of β-glucan. However, former studies show gelation only at relatively high concentrations. In this study, gelation of barley and oat β-glucans (both native and oxidised) was shown with 1% and 1.5% solutions, respectively, when using optimised dissolution temperatures that resulted in partial solubilisation of β-glucan molecules. The partial dissolution was proposed to enable formation of nucleation cites for gelation. In this study, changes in the structure and physicochemical properties of barley and oat β-glucans due to oxidation were demonstrated. Additionally, gelation of both non-oxidised and oxidised β-glucan was shown at concentrations relevant for food products. The results of this study provide an understanding of the role of oxidation for the stability of β-glucan in processing and storage of foods. The study suggests that gelation of β-glucan could overcome the negative effects of oxidation-related viscosity loss.
  • Liu, Xiaoli (Helsingin yliopisto, 2017)
    A community is a collection of populations of different species living in the same geographical area. Species interact with each other in the community and this interaction affects species distribution, abundance, and even evolution. Species interact in various ways, for instance through competition, predation, parasitism, mutualism, and commensalism. We have two focuses in this thesis. One focus is analyzing the dynamical behaviors of the discretization systems of the Lotka-Volterra predator-prey model. It is well known that the dynamics of the logistic map is more complex compared with logistic differential equation. Period doubling and the onset of chaos in the sense of Li-York occur for some values. Inspired by this, we analyze the dynamical behaviors of the discretization systems of the Lotka-Volterra predator-prey model (articles I and II). In article I, we show that the system undergoes fold bifurcation, flip bifurcation and Neimark-Sacker bifurcation, and has a stable invariant cycle in the interior of $R_+^2$ for some parameter values. In article II, we show that the unique positive equilibrium undergoes flip bifurcation and Neimark-Sacker bifurcation. Moreover, system displays much interesting dynamical behaviors, including period-5, 6, 9, 10, 14, 18, 20, 25 orbits, invariant cycles, cascade of period-doubling, quasi-period orbits and the chaotic sets. We emphasize that the discretization of continuous models (articles I and II are not acceptable as a derivation of discrete predator-prey models. A discrete predator-prey model is also formulated in Section 2. We analyze the dynamics (articles I and II) from the mathematical point of view instead of biological point of view. The other focus is disease-competition in an ecological system. We propose a model combining disease and competition and study how a disease affects the two competing species (article III). In our model, we assume that only one of the species is susceptible to an SI type disease with mass action incidence, and that infected individuals do not reproduce but suffer from additional disease induced death. We further assume that infection does not reduce the competitive ability of the infected. We show that infection of the superior competitor enables the inferior competitor to coexist, either as a stable steady state or limit cycle. In the case where two competing species coexist without the disease, the introduction of disease is partially determined by the basic reproduction number. If the reproduction number is less than 1, the disease free coexistence equilibrium is globally asymptotically stable. If the basic reproduction number is larger than 1, our system is uniformly persistent. The unique coexisting endemic disease equilibrium exists and is globally stable under certain conditions. However, infection of the inferior competitor does not change the outcome.
  • Keronen, Petri (Helsingin yliopisto, 2017)
    FLUX AND CONCENTRATION MEASUREMENTS OF CARBON DIOXIDE AND OZONE IN A FORESTED ENVIRONMENT This thesis compiles the setup and characteristics of the measurement systems for CO2, H2O vapour and O3 eddy-covariance (EC) flux and vertical concentration profile, and their calibration arrangements at the SMEAR II station of the University of Helsinki. A commercial chemiluminescence O3 analyser operating on a liquid reagent solution was modified to improve its suitability and reliability in long term EC flux measurements. Fluxes of CO2 and O3 were also determined with the flux-profile method relating the fluxes to the observed concentration profiles. The EC and the flux-profile methods were inter-compared and their performances were evaluated. A separate measurement system utilising a commercial, low cost Non-dispersive Infrared-absorption analyser and incorporating an automatic calibration system for measuring atmospheric CO2 mole fraction was developed in the thesis. The performance of the system was evaluated and its measurement accuracy was determined in comparisons to reference standards. The measured CO2 mole fraction data was compared with the results of an independent atmospheric transport simulation (MACC-II) for period November 2006–December 2011. The modifications made to the reagent liquid flow system improved the reliability of the EC O3 analyser. The fluxes measured with the eddy-covariance and flux-profile method agreed during daytime under unstable conditions. At night-time the flux-profile method estimated higher respiration of CO2 and stronger deposition of O3, but no apparent reason for over- or underestimation by either method was identified. Night-time eddy-covariance fluxes had a specious dependence on turbulence even after accounting for storage flux. Additionally the chemical sink strength was evaluated negligible also for O3. Accounting for vertical advection flux removed the dependencies. However, while accounting for the vertical advection flux resulted in invariance of both net ecosystem exchange (NEE) of CO2 and deposition rate of O3 on turbulence intensity, the importance for estimating e.g. NEE by different ways at other flux tower sites was stressed. The atmospheric CO2 mole fraction measurement system had an accuracy of 0.3–0.4 µmol mol-1, an operating ratio of 99 % and its data coverage was 95 % during the comparison period. The trend and phase of the modelled and measured atmospheric CO2 mole fraction data, on the average 390 µmol mol-1, were observed to generally agree and the average bias of the simulation, –0.2 µmol mol-1, was within the measurement accuracy. The instrumentation fulfilled the set requirements of accuracy and continuous operation, and the result of the comparison implied that the CO2 mole fraction data from the SMEAR II station would clearly have the potential to be assimilated in the MACC-II simulations and thus improving their accuracy.
  • Kaskela, Anu (Geological Survey of Finland, 2017)
    Marine ecosystems provide a wide range of ecosystem services to human society, including supporting, regulating, cultural, and provisioning services. The concept of Blue Growth even considers marine areas as potential drivers of the economy. However, despite the long tradition of ocean exploration, the realization of Blue Growth and effective marine spatial planning often suffer from incomplete and scattered marine data over large areas. This dissertation presents a GIS-based approach to analyzing and characterizing the geologic seabed environment of the Baltic Sea. It combines scattered geospatial data to produce spatial representations of the Baltic Sea in terms of the seabed geomorphic features, marine landscapes, and geodiversity. The broad scales of the analyses reflect the scale of the available datasets and the needs of transnational ecosystem-based management. Spatial analysis techniques enabled the identification of coherent geomorphic features and quantification of geodiversity patterns over the entire Baltic Sea region, within the limits of the input data resolution. Based on the results, the overall geological landscape of the Baltic Sea is characterized by plains and basins. Other geomorphic features, such as elevations and valleys, are characteristic of certain sub-regions. The seabed geodiversity generally increases from south to north and from the open sea to areas with a high shore density. The crystalline bedrock areas provide more diverse seabed environments than the sedimentary rock areas. Archipelagos, in particular, stand out as seabed areas with high geodiversity. The results underline the significance of the ongoing processes (erosion, sediment transport, and accumulation), the basement rock type, past glaciations, and certain geological events during the last deglaciation in shaping the seabed environment of the Baltic Sea. The dissertation presents new evidence that the geodiversity of the seafloor influences the distribution of the zoobenthic assemblages of the eastern Gulf of Finland. It is suggested that the high geodiversity and archipelago gradient could directly influence benthic assemblages and biodiversity by providing a multitude of habitats and indirectly by channeling water movement. Additionally, the potential key habitats, rocky reefs, were mapped with good accuracy in seabed areas with limited data, and the features were also recognized to have ecological value. These spatial datasets provide valuable background material for more detailed studies on the rocky reefs and the archipelago areas, as well as for monitoring their status. The study provides spatial information on the seabed characteristics of the Baltic Sea for scientists, marine spatial planners, and managers. The results emphasize that geodiversity should be acknowledged in the ecosystem-based management of marine areas, because it has intrinsic value, it provides several abiotic ecosystem services, and it is associated with the biodiversity and long-term conservation of the marine environment.
  • Jääskeläinen, Iiro (Helsingin yliopisto, 2017)
    Background. Skin and skin structure infections (SSSI) are among the most frequent indications for antimicrobial treatment both in the hospital and outpatient settings. SSSI is generally considered as complicated (cSSSI) if it involves deep subcutaneous tissues, needs surgery in addition to antimicrobial therapy or affects a patient with severe co-morbidity, like diabetes. CSSSIs are among the most frequently studied indications for new antibiotics and early treatment response has been suggested for assessment of drug efficacy. Study population. The patient material (n=460) of this population-based retrospective observational study consisted of all adult residents from Helsinki, Finland and the Gothenburg area, Sweden, who were hospitalized due to cSSSI in 2008–2011. Results and conclusions. In our study, as compared to previous studies on cSSSI, high levels of bacteraemia (13% of patients), treatment failure (38%) and initial antibiotic treatment modifications (39%) were detected, but a switch to narrow-spectrum antibiotic treatment (streamlining) was rare (5%). Staphylococcus aureus (21%) and streptococci (16%) were the most common aetiologies in monomicrobial infections. In multivariable analysis, late (≥4 days) treatment response was significantly associated to admission to ICU (OR 10.1), posttraumatic wound infection (OR 3.17), bacteraemia (OR 3.09), surgical intervention after diagnosis (OR 2.64), diabetes (OR 2.33) and initial broad-spectrum antibiotic therapy (OR 3.03). Early treatment response (≤3 days) was associated with previous hospitalization (OR 0.47) and empirical antimicrobial therapy covering the initial pathogens (OR 0.38). These observations suggest that time to treatment response depends not merely on treatment related factors. Furthermore, patients with early treatment response had eventually shorter hospital stay and antimicrobial treatment than those who stabilized later. After exclusion of patients with diabetic foot infection, no difference was detected in the microbiological aetiology of cSSSI between diabetics and nondiabetics. Yet, diabetes was the only baseline characteristic associated with broad-spectrum antimicrobial use and long (≥17 days) antibiotic treatment duration. Remarkable differences in the management of cSSSI were revealed between the two Nordic cities. Patients in Helsinki, as compared to those in Gothenburg, were treated more often with antimicrobials covering also Gram-negatives (96% vs. 47%), had more treatment modifications (mean 4.3 vs. 2.7) and longer median duration of antimicrobial therapy (29 vs. 12 days) and longer in-hospital stay (17 vs. 11 days). Most importantly, 57% of patients in Helsinki visited more than one department during their hospital stay, while in Gothenburg 85% of patients were treated in only one department. The findings suggest that cSSSI could be treated more often with a narrow-spectrum antibiotic and with a shorter treatment time and that unnecessary surgery and transfer of patients between wards should be avoided.
  • Oikkonen, Annu (Helsingin yliopisto, 2017)
    The state of the sea ice cover results from an interplay between thermodynamics and dynamics. Changes in the ice cover further affect the way in which the ice responds to forcing, both thermodynamic and dynamic. This thesis discusses several aspects of sea ice thermodynamics and dynamics, and their contribution to the evolution of ice pack, and particularly to changes in the Arctic sea ice cover. The main focus is on the ice dynamics in different types of ice zones and under different conditions, which also enables the examination of the impact of thermodynamic forcing on sea ice dynamics. Changes in the Arctic sea ice thickness distribution during the period 1975-2000 are studied in detail, and the contribution of thermodynamics and dynamics as driving forcing is discussed. The results show that the shape of the sea ice thickness distribution has changed: the peak of the distribution has generally narrowed and shifted towards thinner ice. A prevalent feature is the loss of thick, mostly deformed ice, which has had a significant role in the decrease in the mean and modal ice thickness. The results also show a decrease in the seasonal variability of the mean ice thickness, but with strong regional differences. Also, the regional variability of the sea ice thickness has decreased, since the thinning has been the most pronounced in regions which formerly had the thickest ice cover. The observed changes in the regional ice draft distributions cannot be explained by local warming of the atmosphere, but changes in the ice drift patterns have had an essential impact. These results emphasize the importance of the description of sea ice dynamics in the models. Sea ice dynamics, and especially deformation, strongly affect the evolution of ice volume and properties of ice cover. There has still been a need for better understanding of the highly local and intermittent deformation process, as well as its variability that rises from different types of conditions and regions. Several aspects of these questions are covered in this thesis. With coastal and ship radar images, the study of the length scale dependency of sea ice deformation rate is extended to smaller length scales (from 100 m to 10 km) and time scales (from 10 min to 24 h) than were previously possible. Sea ice deformation rate is shown to exhibit a power law with respect to both length scale and time scale at all the scales covered. Both the overall deformation rate and the length scale dependency of deformation rate are found to depend strongly on the time scale considered. Small scale deformation is studied in different type of ice regions (coastal boundary zone, compact Arctic ice pack and marginal ice zone), and under different weather conditions. One of the key findings is the connection between air temperature and deformation rate: during warm days deformation rates are generally higher than during cold days. The deformation rate is found to respond to changes in air temperature in a time scale of days, which is clearly faster than previously assumed. This response is most likely connected to the effectiveness of the healing process. However, despite of the most effective healing during the coldest winter, the previously damaged areas are found to remain the weak points in the ice cover. This confirms that the deformation history is an important factor in determining how the ice cover responds to dynamic forcing.