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  • 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.
  • Hirvonen, Juho (2012)
    In this work we study a graph problem called edge packing in a distributed setting. An edge packing p is a function that associates a packing weight p(e) with each edge e of a graph such that the sum of the weights of the edges incident to each node is at most one. The task is to maximise the total weight of p over all edges. We are interested in approximating a maximum edge packing and in finding maximal edge packings, that is, edge packings such that the weight of no edge can be increased. We use the model of distributed computing known as the LOCAL model. A communication network is modelled as a graph, where nodes correspond to computers and edges correspond to direct communication links. All nodes start at the same time and they run the same algorithm. Computation proceeds in synchronous communication rounds, during each of which each node can send a message through each of its communication links, receive a message from each of its communication links, and then do unbounded local computation. When a node terminates the algorithm, it must produce a local output – in this case a packing weight for each incident edge. The local outputs of the nodes must together form a feasible global solution. The running time of an algorithm is the number of steps it takes until all nodes have terminated and announced their outputs. In a typical distributed algorithm, the running time of an algorithm is a function of n, the size of the communication graph, and Δ, the maximum degree of the communication graph. In this work we are interested in deterministic algorithms that have a running time that is a function of Δ, but not of n. In this work we will review an O(log Δ)-time constant-approximation algorithm for maximum edge packing, and an O(Δ)-time algorithm for maximal edge packing. Maximal edge packing is an example of a problem where the best known algorithm has a running time that is linear-in-Δ. Other such problems include maximal matching and (Δ+1)-colouring. However, few matching lower bounds exist for these problems: by prior work it is known that finding a maximal edge packing requires time Ω(log Δ), leaving an exponential gap between the best known lower and upper bounds. Recently Hirvonen and Suomela (PODC 2012) showed a linear-in-Δ lower bound for maximal matching. This lower bound, however, applies only in weaker, anonymous models of computation. In this work we show a linear-in-Δ lower bound for maximal edge packing. It applies also in the stronger port numbering model with orientation. Recently Göös et al. (PODC 2012) showed that for a large class of optimisation problems, the port numbering with orientation model is as powerful as a stronger, so called unique identifier model. An open question is if this result can applied to extend our lower bound to the unique identifier model.
  • Mäki, Jussi Olavi Aleksis (2013)
    With the increasing growth of data traffic in mobile networks there is an ever growing demand from the operators for a more scalable and cost efficient network core. Recent successes in deploying Software-Defined Networking (SDN) in data centers and large network backbones has given it credibility as a viable solution for meeting the requirements of even the large core networks. Software-Defined Networking is a novel new paradigm where the control logic of the network is separated from the network elements into logically centralized controllers. This separation of concerns offers more flexibility in network control and makes writing of new management applications, such as routing protocols, easier, faster and more manageable. This thesis is an empirical experiment in designing and implementing a scalable and fault- tolerant distributed SDN controller and management application for managing the GPRS Tunneling Protocol flows that carry the user data traffic within the Evolved Packet Core. The experimental implementation is built using modern open-source distributed system tools such as the Apache Zookeeper distributed coordination service and Basho’s Riak distributed key-value database. In addition to the design, a prototype implementation is presented and its performance is evaluated.
  • Vainionpää, Noora (nyk. Noora Skants) (Helsingin yliopisto, 2008)
    Basement membranes are specialized sheets of extracellular matrix found in contact with epithelia, endothelia, and certain isolated cells. They support tissue architecture and regulate cell behaviour. Laminins are among the main constituents of basement membranes. Due to differences between laminin isoforms, laminins confer structural and functional diversity to basement membranes. The first aim of this study was to gain insights into the potential functions of the then least characterized laminins, alpha4 chain laminins, by evaluating their distribution in human tissues. We thus created a monoclonal antibody specific for laminin alpha4 chain. By immunohistochemistry, alpha4 chain laminins were primarily localized to basement membranes of blood vessel endothelia, skeletal, heart, and smooth muscle cells, nerves, and adipocytes. In addition, alpha4 chain laminins were found in the region of certain epithelial basement membranes in the epidermis, salivary gland, pancreas, esophagus, stomach, intestine, and kidney. Because of the consistent presence of alpha4 chain laminins in endothelial basement membranes of blood vessels, we evaluated the potential roles of endothelial laminins in blood vessels, lymphatic vessels, and carcinomas. Human endothelial cells produced alpha4 and alpha5 chain laminins. In quantitative and morphological adhesion assays, human endothelial cells barely adhered to alpha4 chain-containing laminin-411. The weak interaction of endothelial cells with laminin-411 appeared to be mediated by alpha6beta1 integrin. The alpha5 chain-containing laminin-511 promoted endothelial cell adhesion better than laminin-411, but it did not promote the formation of cell-extracellular matrix adhesion complexes. The adhesion of endothelial cells to laminin-511 appeared to be mediated by Lutheran glycoprotein together with beta1 and alphavbeta3 integrins. The results suggest that these laminins may induce a migratory phenotype in endothelial cells. In lymphatic capillaries, endothelial basement membranes showed immunoreactivity for laminin alpha4, beta1, beta2, and gamma1 chains, type IV and XVIII collagens, and nidogen-1. Considering the assumed inability of alpha4 chain laminins to polymerize and to promote basement membrane assembly, the findings may in part explain the incomplete basement membrane formation in these vessels. Lymphatic capillaries of ovarian carcinomas showed immunoreactivity also for laminin alpha5 chain and its receptor Lutheran glycoprotein, emphasizing a difference between normal and ovarian carcinoma lymphatic capillaries. In renal cell carcinomas, immunoreactivity for laminin alpha4 chain was found in stroma and basement membranes of blood vessels. In most tumours, immunoreactivity for laminin alpha4 chain was also observed in the basement membrane region of tumour cell islets. Renal carcinoma cells produced alpha4 chain laminins. Laminin-411 did not promote adhesion of renal carcinoma cells, but inhibited their adhesion to fibronectin. Renal carcinoma cells migrated more on laminin-411 than on fibronectin. The results suggest that alpha4 chain laminins have a counteradhesive function, and may thus have a role in detachment and invasion of renal carcinoma cells.
  • Nurmi, Satu (2015)
    Many drugs are known to bind to melanin, a complex pigment polymer found in several human tissues. Melanin can act as a natural depot by prolonging the effect of the drug and reducing its toxicity. Since it is highly concentrated in the posterior part of the eye, pigment targeted long-acting drug delivery systems are proposed as an option in ocular diseases. In systemic drug delivery, pigment targeted drugs can potentially distribute to any melanin containing tissue. Therefore, the literature review of the thesis concentrates on the characteristics of melanin and melanosomes, drug binding property and melanin distribution in humans and other species. The main objective of the exploratory part was to determine if melanin binding can be studied with SPECT/CT (single photon emission computed tomography / computed tomography) imaging method. Two different melanin binding drugs, chloroquine and nadolol, were selected and labeled with iodine and radioactive iodine (123I). Equilibrium melanin binding of iodinated and non-iodinated drugs was studied in vitro in order to find out if iodination affects to the binding. Melanin binding was studied in vitro also with non-binding reference salicylic acid, I2-salicylic acid and salbutamol. Finally, melanin binding of 123I-choloroquine and 123I-nadolol was studied with SPECT/CT (NanoSPECT/CT, Bioscan Inc., USA) by comparing distribution kinetics between pigmented and albino rat. Drugs were administered intravenously to the tail vena and the distribution was followed in several time points, up to 24 h. Based on in vitro study, iodination increases melanin binding of hydrophilic drugs, nadolol and salicylic acid, significantly. In vivo study showed clear accumulation of 123I-chloroquine in the posterior eye of pigmented rats whereas it was absent from albino rat. Interestingly, 123I-nadolol accumulated in to the nasal cavity of pigmented rats. Aromatic iodination changes electronegative properties of compounds and raises their logP (octanol/water partition coefficient) value affecting to the melanin binding positively. Therefore the effect of the radiotracer to the physicochemical properties of the compound and melanin binding should be determined in vitro. This study showed that SPECT/CT imaging method can be used to study melanin binding in vivo. Because the method is semi-quantitative, also a quantitative method should be incorporated to the study in order to have more powerful data. Additional studies are required for statistical analysis.
  • Nurmi, Satu (2014)
    Many drugs are known to bind to melanin, a complex pigment polymer found in several human tissues. Melanin can act as a natural depot by prolonging the effect of the drug and reducing its toxicity. Since it is highly concentrated in the posterior part of the eye, pigment targeted long-acting drug delivery systems are proposed as an option in ocular diseases. In systemic drug delivery, pigment targeted drugs can potentially distribute to any melanin containing tissue. Therefore, the literature review of the thesis concentrates on the characteristics of melanin and melanosomes, drug binding property and melanin distribution in humans and other species. The main objective of the exploratory part was to determine if melanin binding can be studied with SPECT/CT (single photon emission computed tomography / computed tomography) imaging method. Two different melanin binding drugs, chloroquine and nadolol, were selected and labeled with iodine and radioactive iodine (123I). Equilibrium melanin binding of iodinated and non-iodinated drugs was studied in vitro in order to find out if iodination affects to the binding. Melanin binding was studied in vitro also with non-binding reference salicylic acid, I2-salicylic acid and salbutamol. Finally, melanin binding of 123I-choloroquine and 123I-nadolol was studied with SPECT/CT (NanoSPECT/CT, Bioscan Inc., USA) by comparing distribution kinetics between pigmented and albino rat. Drugs were administered intravenously to the tail vena and the distribution was followed in several time points, up to 24 h. Based on in vitro study, iodination increases melanin binding of hydrophilic drugs, nadolol and salicylic acid, significantly. In vivo study showed clear accumulation of 123I-chloroquine in the posterior eye of pigmented rats whereas it was absent from albino rat. Interestingly, 123I-nadolol accumulated in to the nasal cavity of pigmented rats. Aromatic iodination changes electronegative properties of compounds and raises their logP (octanol/water partition coefficient) value affecting to the melanin binding positively. Therefore the effect of the radiotracer to the physicochemical properties of the compound and melanin binding should be determined in vitro. This study showed that SPECT/CT imaging method can be used to study melanin binding in vivo. Because the method is semi-quantitative, also a quantitative method should be incorporated to the study in order to have more powerful data. Additional studies are required for statistical analysis.
  • Nyman, Marjut (Helsingin yliopisto, 2007)
    Climate change contributes directly or indirectly to changes in species distributions, and there is very high confidence that recent climate warming is already affecting ecosystems. The Arctic has already experienced the greatest regional warming in recent decades, and the trend is continuing. However, studies on the northern ecosystems are scarce compared to more southerly regions. Better understanding of the past and present environmental change is needed to be able to forecast the future. Multivariate methods were used to explore the distributional patterns of chironomids in 50 shallow (≤ 10m) lakes in relation to 24 variables determined in northern Fennoscandia at the ecotonal area from the boreal forest in the south to the orohemiarctic zone in the north. Highest taxon richness was noted at middle elevations around 400 m a.s.l. Significantly lower values were observed from cold lakes situated in the tundra zone. Lake water alkalinity had the strongest positive correlation with the taxon richness. Many taxa had preference for lakes either on tundra area or forested area. The variation in the chironomid abundance data was best correlated with sediment organic content (LOI), lake water total organic carbon content, pH and air temperature, with LOI being the strongest variable. Three major lake groups were separated on the basis of their chironomid assemblages: (i) small and shallow organic-rich lakes, (ii) large and base-rich lakes, and (iii) cold and clear oligotrophic tundra lakes. Environmental variables best discriminating the lake groups were LOI, taxon richness, and Mg. When repeated, this kind of an approach could be useful and efficient in monitoring the effects of global change on species ranges. Many species of fast spreading insects, including chironomids, show a remarkable ability to track environmental changes. Based on this ability, past environmental conditions have been reconstructed using their chitinous remains in the lake sediment profiles. In order to study the Holocene environmental history of subarctic aquatic systems, and quantitatively reconstruct the past temperatures at or near the treeline, long sediment cores covering the last 10000 years (the Holocene) were collected from three lakes. Lower temperature values than expected based on the presence of pine in the catchment during the mid-Holocene were reconstructed from a lake with great water volume and depth. The lake provided thermal refuge for profundal, cold adapted taxa during the warm period. In a shallow lake, the decrease in the reconstructed temperatures during the late Holocene may reflect the indirect response of the midges to climate change through, e.g., pH change. The results from three lakes indicated that the response of chironomids to climate have been more or less indirect. However, concurrent shifts in assemblages of chironomids and vegetation in two lakes during the Holocene time period indicated that the midges together with the terrestrial vegetation had responded to the same ultimate cause, which most likely was the Holocene climate change. This was also supported by the similarity in the long-term trends in faunal succession for the chironomid assemblages in several lakes in the area. In northern Finnish Lapland the distribution of chironomids were significantly correlated with physical and limnological factors that are most likely to change as a result of future climate change. The indirect and individualistic response of aquatic systems, as reconstructed using the chironomid assemblages, to the climate change in the past suggests that in the future, the lake ecosystems in the north do not respond in one predictable way to the global climate change. Lakes in the north may respond to global climate change in various ways that are dependent on the initial characters of the catchment area and the lake.
  • Ilmonen, Lotta (2003)
    Stamceller definieras ofta enligt det organ de befinner sig i. Det antas att stamceller från ett visst organ kan ge upphov till alla celler av detta organ och bara till dessa celler. Därför har färska forskningar väckt uppmärksamhet då de påvisat att stamceller kan välja otypiska specialiceringslinjer. Experiment har utförts på bestrålade djur. Det har varit oklart vilken betydelse donatorns stamceller har på mottagarens tillväxt i fysiologiska tillstånd. I denna studie har vi använt kimeriska tvillingkalvar i vilkas nonhematopoetiska vävnader donatorns stamceller har spårats. Med tvillingar av olika kön resulterar placentala anastomoser i tidig embryonal utveckling, i en kimerisk, steril kokalv som kallas freemartin. Med hjälp av Y-kromosom riktad in situ hybridisering kan vi spåra donatorns, tjurkalvens celler i mottagarens, freemartin-kalvens vävnader i deras naturliga omgivning. Hematopoetiska celler spårades med att identifiera deras CD45 yt-antigen och kunde därmed, i kombination med in situ hybridiseringen ekskluderas. Vi har hittat nonhematopoetiska celler härstammande från donatorn i vävnader vars ursprung är långt från varandra, så som entodermet och nerv stängen. Nonhematopoetiska celler som härstammar från donatorn var fåtaliga och de var sporadiskt utspridda i vävnaderna. Detta föreslår att de har ringa betydelse i det fysiologiska uppehållet och i utvecklingen av nötkreaturens vävnader.
  • Schendzielorz, Nadia (Helsingin yliopisto, 2012)
    Catechol-O-methyltransferase (COMT) metabolises catecholamines such as dopamine, noradrenaline and adrenaline, which are well-characterised neurotransmitters that play important roles in the regulation of physiological processes. The COMT enzyme exists in membrane-bound (MB-COMT) and soluble (S-COMT) forms that are both encoded by the same gene. Presently, the necessity and physiological importance of the existence of two COMT isoenzymes remains partially unknown. The aim of this thesis was to provide new insights into the specific distribution patterns of MB-COMT and S-COMT, to verify the proposed hormonal regulation of COMT and to investigate its possible physiological role in feeding behaviour. We used two different study designs to address the distribution of COMT in the brain. First, we utilised dopaminergic and noradrenergic toxins to assess the presence of COMT in presynaptic neurons originating from selected brain areas. Successful lesioning of the neurons was confirmed by measuring dopamine and noradrenaline levels in their respective projection areas. However, despite successful lesioning, no changes in COMT protein expression or activity could be noted, indicating that COMT is not present in presynaptic dopaminergic and noradrenergic neurons. The specific distribution patterns of MB-COMT and S-COMT were studied in an S-COMT-deficient mouse line (lacking the S-COMT form of COMT). By comparing these mice to wild type mice, we found that the general distribution patterns of both COMT isoforms were similar between the genotypes. Notably, S-COMT-deficient mice did not exhibit nuclear COMT staining, indicating that MB-COMT is not present in cell nuclei. Furthermore, S-COMT-deficient mice allowed us to examine the association of MB-COMT with the plasma membrane. Contrary to previous assumptions, MB-COMT is not associated with the plasma membrane, but instead may be attached to intracellular cytosolic membranes. The proposed regulatory function of oestrogens on COMT activity was studied by subjecting male and female Wistar rats to different hormonal treatments over a two-week period. Antagonising/modulating the effects of oestrogen via the administration of tamoxifen increased COMT activity and expression. Unexpectedly, increasing oestradiol levels in male rats also led to the upregulation of COMT expression in several tissues, underscoring the importance of COMT in the clearance of biologically active oestrogen metabolites. Finally, we used female rodents (rats and mice) to address the possible role of COMT in feeding behaviour. Our studies revealed that acute COMT inhibition affects the feeding pattern of rodents; COMT-inhibited animals have significantly more ''long'' meals (lasting 300 sec or more) than vehicle-treated animals. Notably, a relatively short starvation period of 16 h induced a slight, albeit not significant, decrease in prefrontal and striatal COMT activity in mice. This finding is interesting, especially as COMT activity is thought to be rather robust, and may suggest the increased importance of COMT during altered physiological status. In conclusion, although the specific roles of MB-COMT and S-COMT remain partly obscure, their absence from presynaptic dopaminergic and noradrenergic neuron terminals suggests a secondary (and perhaps more modulatory) role of COMT in neurotransmitter metabolism in the brain. Furthermore, the observed decrease in COMT activity after a relatively short starvation period suggests that COMT has an increased importance during certain physiological states. Finally, the observed regulatory function of oestrogens on COMT activity and protein expression in vivo may be of clinical importance as COMT inhibitors are used as adjuncts in the treatment of PD.
  • Hautala, Harri (Helsingin yliopisto, 2008)
    The immediate effects of two human-related vegetation disturbances, (1) green tree retention (GTR) patch felling and scarification by harrowing and (2) experimental understorey vegetation layer removal, were examined in boreal forest stands in Finland. Effects of GTR patch felling and scarification on tree uprootings, on coarse woody debris (CWD) and on epixylic plant community were followed in upland and in paludified forest types. Uprootings increased considerably during 2-3 years after the fellings and were more frequent (47%) in the paludified than in the upland forest (13%). Scarification reduced 68% of the CWD in the felling area. Cover and especially species richness of epixylics declined in the both areas during 1-2 years after the felling. The increasing size of GTR patch correlated positively with the species richness. Regeneration of understorey vegetation community and Vaccinium myrtillus and Vaccinium vitis-idaea after different removals of vegetation layers in an old-growth forest took four years. The regeneration occurred mainly by vegetative means and it was faster in the terms of species richness than in the cover. In the most severe treatment, recovery occurred merely by sexual reproduction. V. myrtillus recovered mainly by producing new shoots. V. vitis-idaea recovered faster than V. myrtillus, mainly by increasing length growth. For ecological reasons, use of larger GTR patches on paludified biotope would be recommendable. In felling areas, scarification by harrowing could be replaced with some other spot-wise method. After moderate intensity level disturbance, recovery occurs rapidly by vegetative regrowth of the dominating species. High level of intensity may prevent the recovery of vegetation community for years, while enabling also the genetic regeneration of the initial species. Local anthropogenic-related disturbances are currently increasing and they can interact during temporally short times, which should be taken in to account in the future forest management plans.
  • Rauramo, Suvi (2000)
    Tutkielmassa tarkastellaan, millaisia kerronnallisia konventioita tietokonepelit käyttävät temmatakseen pelaajan "sisään" tarinamaailmaan. Komparatiivista lähestymistapaa soveltaen tutkielma pyrkii kartoittamaan yhteneväisyyksiä ja eroavaisuuksia tietokonepelien ja aikaisempien audiovisuaalisten medioiden välillä. Tutkimuksen empiirisenä aineistona on 36 PlayStation- ja PC-peliä vuosilta 1996-2000. Elokuvan kerronnan teoriaa hyväksi käyttäen eritellään, miten tietokonepeleissä käytetään audiovisuaalisen kerronnan elementtejä. Pelin maailmarakenne nousee keskeiseksi jäsentäväksi tekijäksi. Maailman taustalla oleva looginen rakenne viime kädessä säätelee pelaamista. Maailma rajoittaa pelaajan toimintaa huomattavasti, vaikka peli pyrkiikin usein kätkemään rajoitukset diegeettisesti. Maailman yhtenäisyys ja jatkuvuus ovat elintärkeitä spatiaalisen immersion luomisen kannalta. Tutkielma vahvistaa, että navigointi maailmassa on keskeinen kerronnallinen voima. Fokalisoijahahmon liikuttaminen tai nondiegeettisen näkymän kontrollointi vaikuttaa tarinan purkautumiseen, kameran liikkeeseen, otosten siirtymiin sekä joskus myös kerronnallisen näkökulman vaihteluun. Kerronnallisten peruselementtien - maailman, sen rajauksen ja sen sisäisten siirtymien - analysoinnin perusteella tutkielmassa muodostetaan tietokonepeleille tyypilliset kerronnalliset näkökulmat. Tietokonepelit käyttävät useita kerronnallisia näkökulmia: ensimmäisen persoonan näkökulmaa, seuraajanäkökulmaa, neljännen seinän näkökulmaa, lintunäkökulmaa tai jumalnäkökulmaa. Kuitenkin yleensä vain yhtä tai kahta näkökulmaa käytetään kussakin pelissä. Hahmo on alisteisessa asemassa maailmaan nähden silloinkin, kun hahmo on fokalisoija. Tätä korostaa kuvan rajaaminen kaukaa: hahmo on (hyvin) pieni, kun taas ympäröivä maailma nousee pääosaan. Lisäksi kerronta on usein nondiegeettistä, jolloin näkymä ei ole lainkaan sidoksissa hahmoon. Maailma, eikä hahmo, on pelaajan huomion keskipiste. Pelien kerronta näyttää kehittyvän kohti lyhyempiä otospituuksia ja entistä monipuolisempaa kameran sijoittelua ja liikettä. Suuntaus vie entistä moninaisempiin kerronnallisiin näkökulmiin ja kerronnan tasoihin, mikä on perustavanlaatuinen edellytys kehittyneelle tarinankerronnalle. Keskeiset lähteet ovat Edward Braniganin Narrative comprehension and film (1992) ja Lev Manovichin The language of new media (ilmestyy 2000).
  • Hacklin, Saara (Helsingin yliopisto, 2012)
    Maurice Merleau-Ponty (1908-1961) has been known as the philosopher of painting. His interest in the theory of perception intertwined with the questions concerning the artist s perception, the experience of an artwork and the possible interpretations of the artwork. For him, aesthetics was not a sub-field of philosophy, and art was not simply a subject matter for the aesthetic experience, but a form of thinking. This study proposes an opening for a dialogue between Merleau-Pontian phenomenology and contemporary art. The thesis examines his phenomenology through certain works of contemporary art and presents readings of these artworks through his phenomenology. The thesis both shows the potentiality of a method, but also engages in the critical task of finding the possible limitations of his approach. The first part lays out the methodological and conceptual points of departure of Merleau-Ponty s phenomenological approach to perception as well as the features that determined his discussion on encountering art. Merleau-Ponty referred to the experience of perceiving art using the notion of seeing with (voir selon). He stressed a correlative reciprocity described in Eye and Mind (1961) as the switching of the roles of the visible and the painter. The choice of artworks is motivated by certain restrictions in the phenomenological readings of visual arts. The examined works include paintings by Tiina Mielonen, a photographic work by Christian Mayer, a film by Douglas Gordon and Philippe Parreno, and an installation by Monika Sosnowska. These works resonate with, and challenge, his phenomenological approach. The chapters with case studies take up different themes that are central to Merleau-Ponty s phenomenology: space, movement, time, and touch. All of the themes are interlinked with the examined artworks. There are also topics that reappear in the thesis, such as the notion of écart and the question of encountering the other. As Merleau-Ponty argued, the sphere of art has a particular capability to address our being in the world. The thesis presents an interpretation that emphasises the notion of écart, which refers to an experience of divergence or dispossession. The sudden dissociation, surprise or rupture that is needed in order for a meeting between the spectator and the artwork, or between two persons, to be possible. Further, the thesis suggests that through artworks it is possible to take into consideration the écart, the divergence, that defines our subjectivity.
  • Torsti, Pilvi (2003)
    Tutkimuksen tavoite oli kaksiosainen: historian käytön analysointi sodanjälkeisessä Bosnia ja Hertsegovinassa erityisesti nuorten näkökulmasta sekä Bosnian serbi-, kroaatti-, ja bosniakkinuorten historiallisen ajattelun tarkastelu. Tutkimustavoite konkretisoitui seuraavaan kolmeen pääanalyysiin: Analyyseista ensimmäinen käsitteli yleistä historian läsnäoloa sodanjälkeisessä Bosniassa. Jäsentelin analyysin historiallisten ilmiöiden, kuten historiakulttuurin, historiatietoisuuden ja historiapolitiikan ympärille. Toinen pääanalyysi keskittyi kolmeen erilliseen 8. luokan historian oppikirjaan (8. luokka on peruskoulun viimeinen luokka), joita Bosnian kolme kansallista ryhmää ovat käyttäneet sotavuosista lähtien. Koulukirjakäsittely rakentui sodan, rauhan ja kansakunnan käsitteiden ympärille. Keskuskäsitteiden katsotaan olevan keskeisiä yhteiskuntahistoriallisia käsitteitä sodanjälkeisessä Bosniassa. Kolmas pääanalyysi käsitteli kansainvälistä Nuoret ja Historia -tutkimusta, jonka keräsin kahdeksasluokkalaisilta bosnialaisilta 1999–2000. Nuorten historiallista ajattelua ja käsityksiä kuvannut tilastollinen analyysi perustui 907 oppilaan vastauksiin ja keskittyi samojen kolmen pääkäsitteen representaatioihin kuin oppikirja-analyysi. Bosnian kansallisten ryhmien vastauksia verrattiin muiden maiden tuloksiin sekä keskenään. Analyysi historian läsnäolosta kuvasti historiakulttuurin jakautumista kolmeen erilliseen ja osin jopa vastakkaiseen kulttuuriin sodanjälkeisessä Bosniassa. Historian oppikirjat havainnollistivat, kuinka kolmen kansanryhmän esitykset menneestä luovat viholliskuvia muista kansanryhmistä maan sisällä. Kirjat rakentavat kolmea erilaista historiantulkintaa neljän miljoonan asukkaan yhteiskunnan sisällä ja rinnastavat usein menneen ja nykyisen. Samaan aikaan Nuoret ja Historia –tutkimus osoitti, että valtaosassa kysymyksiä Bosnian kansalliset ryhmät erottuivat toisistaan vain marginaalisesti. Eurooppalaisessa vertailussa Bosnian nuoret muodostivat oman yksittäisen ryhmänsä: he uskoivat vahvasti rauhaan tulevaisuudessa eivätkä pitäneet sotia tärkeinä historian muutosvoimina.
  • Torsti, Pilvi (2003)
    The task of the research was binary: to determine the use of history in the post-war Bosnia and Herzegovina from the perspective of young people, and to define the historical thinking of youth among Bosnian Serbs, Croats and Bosniacs. The task coalesced into three main analyses. The first analysis discussed the general presence of history in post-war Bosnian society. The analysis was organised around history-related phenomena: history culture, historical consciousness and history politics. Three separate 8th-grade (the 8th grade is the last year of obligatory schooling) history textbooks used by the three Bosnian national communities were the subject of the second analysis, which focused on the representations of three socio-historical concepts central in post-war Bosnian society: war, peace and nation. The third analysis of the historical thinking of the youth was based on the international Youth and History survey which I conducted among 8th-grade pupils in Bosnia in 1999-2000. The descriptive statistic analysis of the answers of 907 pupils concentrated on the representations of the same three concepts as in the textbooks analysis. The answers of the Bosnian national groups were compared to each other and to other European country samples. The description of the presence of history illustrated the division of history culture into three separate – and even opposing – cultures in post-war Bosnia and Herzegovina. History textbooks further demonstrated how presentations of the past among the three communities create hostile images of the country’s other national groups. They construct three different interpretations of the past within a society of four million people often equating the past with the present. Finally, the Youth and History survey analysis showed that in most questions, the national groups differed only marginally in their thinking. In the European comparison, Bosnians formed a single group and demonstrated great belief in future peace and did not consider wars important factors of change in history.