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  • Karonen, Tiina (Helsingin yliopisto, 2012)
    Leukotriene receptor antagonists montelukast and zafirlukast are used for asthma and allergic rhinitis. Their marketing authorisations were granted over 15 years ago, before regulatory guidance for drug interaction studies existed. At that time the knowledge of their metabolic pathways was largely based on in vitro studies, in which the main enzymes catalysing the biotransformation of montelukast and zafirlukast were cytochrome P450 (CYP) 2C9 and CYP3A4. Since then the understanding of the importance of CYP enzymes in drug metabolism has increased markedly and also the role of CYP2C8 has been recognised. Montelukast and zafirlukast are both potent inhibitors of CYP2C8 in vitro, but neither of them has shown inhibitory effect on CYP2C8 in vivo. Montelukast has also been shown to fit well in the active site cavity of CYP2C8 in a crystallography study. These observations led to examine the role of CYP2C8 and CYP3A4 in the metabolism of montelukast in humans, as well as the role of CYP2C8, CYP2C9 and CYP3A4 in the metabolism of zafirlukast in humans. This work was carried out as four randomised, placebo-controlled cross-over drug interaction studies in healthy volunteers. The CYP2C8 inhibitor gemfibrozil resulted in over fourfold increase of the area under the plasma drug concentration-time curve (AUC) of montelukast, almost blocking the formation of its major metabolite M4. The CYP3A4 inhibitor itraconazole had no effect on the total elimination of montelukast, and decreased only the formation of a minor metabolite M5. The pharmacokinetics of zafirlukast was only affected by CYP2C9 inhibition by fluconazole, which resulted in a 1.6-fold increase of the AUC of zafirlukast. Inhibition of CYP2C8 and CYP3A4 had no effect on the pharmacokinetics of zafirlukast. The results of this work elucidated the biotransformation pathways of montelukast and zafirlukast in humans. CYP2C8 accounts for about 80% of the metabolism of montelukast, while CYP3A4 has no significant role in it. The main enzyme in the metabolism of zafirlukast in humans is CYP2C9. Concomitant use of CYP2C8 inhibitors with montelukast, or CYP2C9 inhibitors with zafirlukast may increase the risk of concentration dependent adverse drug reactions. With regard to drug interaction studies, a probe drug should be sensitive and relatively safe: according to the present findings montelukast is a promising candidate for a CYP2C8 probe substrate. These results also highlight the relevance of drug interaction studies and the regulatory guidelines related to them. Especially drugs that have been developed before the existence of these guidelines may be deficiently characterised with regard to their metabolism, leaving the possibility of unrecognized CYP-mediated interactions.
  • Mustonen, Katja (Helsingin yliopisto, 2012)
    Ketoprofen is a non-steroidal anti-inflammatory drug belonging to the 2-arylpropionic acid group. It has been widely used in domestic animals because of its anti-inflammatory, antipyretic and analgesic actions. Ketoprofen is a chiral compound existing in two enantiomeric forms, S (+) and R (-) ketoprofen. Each enantiomer has different pharmacodynamic and pharmacokinetic properties. The commercial products in veterinary medicine are 50:50 racemic mixtures of both enantiomers. Ketoprofen undergoes unidirectional chiral inversion from the R- to the S-enantiomer, the extent of inversion being about 70% in pigs. The aims of this thesis research were to investigate the oral bioavailability, enantiospecific plasma concentrations and efficacy of racemic ketoprofen after oral administration in pigs. Total plasma concentrations of ketoprofen were investigated in a randomized crossover design. Racemic ketoprofen was administered at 3 mg/kg and 6 mg/kg po, and 3 mg/kg im and iv. The bioavailability of oral ketoprofen was almost complete. Bioequivalence could not be detected between oral and intramuscular administration routes. Plasma concentrations of S- and R-ketoprofen after oral (4 mg/kg) and intramuscular (3 mg/kg) routes of administration of racemic ketoprofen in pigs were determined in crossover design. S-ketoprofen was the predominant enantiomer in pig plasma after administration of the racemic mixture via both routes. The maximum plasma concentration of S-ketoprofen was more than twice as high as that of R-ketoprofen, and the terminal half-life was approximately three times greater for S-ketoprofen than R-ketoprofen with both administration routes. The mean (± SD) relative bioavailability (po compared to im) was 83 ± 20% and 63 ± 23% for S-ketoprofen and R-ketoprofen, respectively. Although some differences were detected in the plasma concentrations of ketoprofen enantiomers after different routes of administration, they are probably not relevant in clinical use. Thus, the pharmacological effects of racemic ketoprofen are considered to be comparable after intramuscular and oral routes of administration in growing pigs. The efficacy of orally administered racemic ketoprofen in endotoxemia in pigs was assessed in an E. coli endotoxin challenge trial. The growing pigs were challenged intravenously with E. coli endotoxin and one hour after the challenge were treated with ketoprofen at dose rates of 0.5 mg/kg, 1 mg/kg, 2 mg/kg and 4 mg/kg or with tap water. The body temperature was measured and a total clinical score was calculated after assessing the general behaviour, respiratory rate and locomotion of the pigs. Thromboxane B2 and ketoprofen concentrations were analysed from blood samples. Ketoprofen treatment significantly reduced the rectal temperature and total clinical scores, and lowered the blood thromboxane B2 concentrations when compared to the control group. Ketoprofen plasma concentrations were lower than previously reported in healthy pigs after similar doses. Two mg/kg can be considered a sufficient oral dose of ketoprofen for treating endotoxemia in pigs, as increasing the dose above this did not further increase the effect. Lameness is a common problem among sows and gilts. It often leads to poor animal welfare and economic losses because of unplanned culling. Locomotor disorders cause severe pain, and lame animals need to be treated accordingly. A field trial was conducted to examine the efficacy and compare two doses of oral administration of racemic ketoprofen in the treatment of clinical lameness caused by non-infectious musculoskeletal disorders in sows and gilts. Dose rates of 2 mg/kg and 4 mg/kg of oral ketoprofen were compared to placebo treatment over five consecutive days in a double-blinded study. Lameness was assessed with a five-grade scoring system prior to and on the last day of the treatment. This study demonstrated that oral ketoprofen was efficient in alleviating the signs of non-infectious lameness in sows and gilts. The rate of treatment success was 54.3% for the ketoprofen 4 mg/kg group, 53.2% for the ketoprofen 2 mg/kg group and 20.8% for the pigs in the placebo group. There was no difference in efficacy between the two ketoprofen doses. Oral ketoprofen appeared to be a practical way to alleviate pain and improve the welfare of lame sows. The findings support the use of ketoprofen at a dose rate of 2 mg/kg in treating locomotor disorders in pigs.
  • Webb, Christian (Helsingin yliopisto, 2013)
    The thesis is about random measures whose density with respect to the Lebesgue measure is the exponential of a Gaussian field with a short range logarithmic singularity in its covariance. Such measures are a special case of Gaussian multiplicative chaos. This type of measures arise in a variety of physical and mathematical models. In physics, they arise as the are measure of two-dimensional Liouville quantum gravity and Gibbs measures in certain simple disordered systems. From a mathematical point of view, they are related to extreme value statistics of random variables with logarithmic correlations and are interesting as such from the point of view of random geometry. Questions addressed in the thesis are how to properly define such measures and some geometric properties of these measures. Defining these measures is non-trivial since due to the singularity in the covariance, the field can only be interpreted as a random distribution and not as a random function. It turns out that after a suitable regularization of the field and normalization of the measure, a limiting procedure yields a non-trivial limit object. This normalization is a delicate procedure and at a certain value of the variance of the field, the behavior of this normalization changes drastically - a phase transition occurs. Once the measure is constructed, some simple geometric and probabilistic properties of these measures are considered. Relevant questions are for example: does the measure possess atoms, if not what is its modulus of continuity, what is the probability distribution of the measure of a set.
  • Kalliomäki, Anna (Helsingin yliopisto, 2003)
  • Keceli, Asli (Helsingin yliopisto, 2015)
    The Standard Model of particle physics (SM) is a gauge field theory that provides a very successful description of the electromagnetic, weak and strong interactions among the elementary particles. It is in very good agreement with the precision measurements and the list of all the fundamental particles predicted by the model was completed with the discovery of the last missing piece, the Higgs boson, at the LHC in 2012. However, it is believed to be valid up to a certain energy scale and widely considered as a low-scale approximation of a more fundamental theory due to some theoretical and phenomenological issues appearing in the model. Among many alternatives, supersymmetry is considered as the most prominent candidate for new physics beyond the SM. Supersymmetry relates two different classes of the particles known as fermions and bosons. The simplest straightforward supersymmetrization of the SM is named as minimal supersymmetric Standard Model (MSSM) where minimal set of new supersymmetric particles is introduced as superpartners of the Standard Model particles. It is the most studied low-scale supersymmetric model since it has very appealing features such as containing a dark matter candidate and providing a solution to the naturalness problem of the SM. After the Higgs discovery, the parameter space of the model has been investigated in great detail and it has been observed that the measured Higgs mass can be achieved only for the parameter regions which generate a severe fine-tuning. Such large fine-tuning can be alleviated by extending the minimal field content of the model via a singlet and/or a triplet. In this thesis, we discuss the triplet extension of the supersymmetric Standard Model where the MSSM field content is enlarged by introducing a triplet chiral superfield with zero hypercharge. The first part of the thesis contains an overview of the SM and the second part is dedicated to the general features of supersymmetry. After discussing aspects of the MSSM in the third part, we discuss the triplet extended supersymmetric Standard Model where we investigate the implications of the triplet on the Higgs phenomenology. We show that the measured mass of the Higgs boson can be achieved in this model without requiring heavy third generation squarks and/or large squark mixing parameters which reduce the amount of the required fine-tuning. Afterwards, we study the charged Higgs sector where a triplet scalar field with non-zero vacuum expectation value leads to h±iZW∓ coupling at tree level. We discuss how this coupling alters the charged Higgs decay and production channels at the LHC.
  • Arte, Sirpa (Helsingin yliopisto, 2001)
  • Laitakari-Pyykkö, Anja-Leena (Helsingin yliopisto, 2013)
    This study addresses the theological contribution to the English Reformation of Martin Luther s friend and associate, Philip Melanchthon. The research conveys Melanchthon s mediating influence in disputes between Reformation churches, in particular between the German churches and King Henry VIII from 1534 to 1539. The political background to those events is presented in detail, so that Melanchthon s place in this history can be better understood. This is not a study of Melanchthon s overall theology. In this work, I have shown how the Saxons and the conservative and reform-minded English considered matters of conscience and adiaphora. I explore the German and English unification discussions throughout the negotiations delineated in this dissertation, and what they respectively believed about the Church s authority over these matters during a tumultuous time in European history. The main focus of this work is adiaphora, or those human traditions and rites that are not necessary to salvation, as noted in Melanchthon s Confessio Augustana of 1530, which was translated into English during the Anglo-Lutheran negotiations in 1536. Melanchthon concluded that only rituals divided the Roman Church and the Protestants. The five adiaphora issues are the disputed articles on the power of the bishops, the marriage or celibacy of priests, monastic vows, the Mass, and communion in both kinds in the Lord s Supper and to which he made a significant contribution. Melanchthon regarded these five as adiaphora (from the Greek  indifferent things ) that is, as matters that were not essential to faith or salvation. Although English theologians never used the word adiaphora, they were familiar with the concept, as will be demonstrated in the historical presentation. These issues are examined within the framework of Scripture and Tradition and the doctrine of justification by faith. The idea of the Scriptures as divine mandate changed the concept of authority in matters of doctrine and practice. From the perspective of both the German Reformers and the reform-minded clergy in England, justification by faith belonged to Scripture and was necessary for salvation. For them, the remainder of Church law (adiaphora), such as ecclesiastical policies, had become secular issues and were not of divine authority. Whereas the Wittenberg Articles were intended as an agreement between the Germans and the English, they did not produce what was hoped for on adiaphora matters, so that the parties could formulate a practice they could defend against the pope s General Council. They did agree on what was necessary for salvation. The disputed articles in which adiaphora was a question were left open for further negotiations. ---------- The method employed in this study is historical-genetic; that is, the chapters are arranged in chronological order, and Melanchthon s contribution to the English Reformation is viewed in the historical context in which the documents were produced. The chapters begin with the supremacy crisis in England (1534) and end with the Act of Six Articles (1539). Chapters Three, Five, Six, and Twelve are divided into two parts the first is a historical account, while the second delineates the documents produced during the negotiations. In other chapters, the author presents the negotiations and their historical background. The doctrine of justification by faith is essential in relation to adiaphora for evaluating Melanchthon s position in his negotiations with the German and English theologians, during the discussions between Catholics and Protestants, in the Anglo-Lutheran negotiations, and within the English Church in the documents produced: the Advice of 1534, the Wittenberg Articles of 1536, the Ten Articles of 1536, the Bishops Book of 1537, the Thirteen Articles of 1538, and the Six Articles of 1539. The major discussion involves Melanchthon s writing of the Loci Communes of 1535 as a doctrinal basis for the unification talks. The Confessio Augustana and the Apologia were translated into English. This is important because many of Melanchthon s concepts acquired somewhat different interpretations as they were translated from Latin into English. The differences in the two texts will be compared to find the degree to which Melanchthon s confessional writings were accepted in England and used by the English Reformers.
  • Mattila, Janne (Helsingin yliopisto, 2011)
    The aim of the dissertation is to explore the idea of philosophy as a path to happiness in classical Arabic philosophy. The starting point is in comparison of two distinct currents between the 10th and early 11th centuries, Peripatetic philosophy, represented by al-Fārābī and Ibn Sīnā, and Ismaili philosophy represented by al-Kirmānī and the Brethren of Purity. They initially offer two contrasting views about philosophy in that the attitude of the Peripatetics is rationalistic and secular in spirit, whereas for the Ismailis philosophy represents the esoteric truth behind revelation. Still, they converge in their view that the ultimate purpose of philosophy lies in its ability to lead man towards happiness. Moreover, they share a common concept of happiness as a contemplative ideal of human perfection, which refers primarily to an otherworldly state of the soul s ascent to the spiritual world. For both the way to happiness consists of two parts: theory and practice. The practical part manifests itself in the idea of the purification of the rational soul from its bodily attachments in order for it to direct its attention fully to the contemplative life. Hence, there appears an ideal of philosophical life with the goal of relative detachment from the worldly life. The regulations of the religious law in this context appear as the primary means for the soul s purification, but for all but al-Kirmānī they are complemented by auxiliary philosophical practices. The ascent to happiness, however, takes place primarily through the acquisition of theoretical knowledge. The saving knowledge consists primarily of the conception of the hierarchy of physical and metaphysical reality, but all of philosophy forms a curriculum through which the soul gradually ascends towards a spiritual state of being along an order that is inverse to the Neoplatonic emanationist hierarchy of creation. For Ismaili philosophy the ascent takes place from the exoteric religious sciences towards the esoteric philosophical knowledge. For Peripatetic philosophers logic performs the function of an instrument enabling the ascent, mathematics is treated either as propaedeutic to philosophy or as a mediator between physical and metaphysical knowledge, whereas physics and metaphysics provide the core of knowledge necessary for the attainment of happiness.
  • Saaristo-Helin, Katri (Helsingin yliopisto, 2011)
    The aim of this study was to examine the applicability of the Phonological Mean Length of Utterance (pMLU) method to the data of children acquiring Finnish, for both typically developing children and children with a Specific Language Impairment (SLI). Study I examined typically developing children at the end of the one-word stage (N=17, mean age 1;8), and Study II analysed children s (N=5) productions in a follow-up study with four assessment points (ages 2;0, 2;6, 3;0, 3;6). Study III was carried out in the form of a review article that examined recent research on the phonological development of children acquiring Finnish and compared the results with general trends and cross-linguistic findings in phonological development. Study IV included children with SLI (N=4, mean age 4;10) and age-matched peers. The analyses in Studies I, II and IV were made using the quantitative pMLU method. In the pMLU method, pMLU values are counted for both the words that the children targeted (so-called target words) and the words produced by the children. When the child s average pMLU value was divided with the average target word pMLU value, it is possible to examine that child s accuracy in producing the words with the Whole-Word Proximity (PWP) value. In addition, the number of entirely correctly produced words is counted to obtain the Whole-Word Correctness (PWC) value. Qualitative analyses were carried out in order to examine how the children s phoneme inventories and deficiencies in phonotactics would explain the observed pMLU, PWP and PWC values. The results showed that the pMLU values for children acquiring Finnish were relatively high already at the end of the one-word stage (Study I). The values were found to reflect the characteristics of the ambient language. Typological features that lead to cross-linguistic differences in pMLU values were also observed in the review article (Study III), which noted that in the course of phonological acquisition there are a large number of language-specific phenomena and processes. Study II indicated that overall the children s phonological development during the follow-up period was reflected in the pMLU, PWP and PWC values, although the method showed limitations in detecting qualitative differences between the children. Correct vowels were not scored in the pMLU counts, which led to some misleadingly high pMLU and PWP results: vowel errors were only reflected in the PWC values. Typically developing children in Study II reached the highest possible pMLU results already around age 3;6. At the same time, the differences between the children with SLI and age-matched peers in the pMLU values were very prominent (Study IV). The values for the children with SLI were similar to the ones reported for two-year-old children. Qualitative analyses revealed that the phonologies of the children with SLI largely resembled the ones of younger, typically developing children. However, unusual errors were also witnessed (e.g., vowel errors, omissions of word-initial stops, consonants added to the initial position in words beginning with a vowel). This dissertation provides an application of a new tool for quantitative phonological assessment and analysis in children acquiring Finnish. The preliminary results suggest that, with some modifications, the pMLU method can be used to assess children s phonological development and that it has some advantages compared to the earlier, segment-oriented approaches. Qualitative analyses complemented the pMLU s observations on the children s phonologies. More research is needed in order to verify the levels of the pMLU, PWP and PWC values in children acquiring Finnish.
  • Heikinheimo, Liisa (Helsingin yliopisto, 2002)
  • Jäntti, Maria (Helsingin yliopisto, 2014)
    Orexins (orexin-A and -B) are neuropeptides with multiple physiological functions, among which regulation of wakefulness and appetite are the best known. Neurons producing orexins are localized in the lateral hypothalamus, from where they send projections to many parts of the brain. Orexins exert their functions by activating two G-protein-coupled receptors, OX1 and OX2. Orexin receptor expression was first reported in the brain, but they are also expressed outside of the central nervous system (CNS). Upon activation, OX1 and OX2 receptors can couple to heterotrimeric G-proteins of different families, including Gq, Gs and Gi/o. Orexin receptor activation can evoke increases in intracellular Ca2+ concentrations via multiple mechanisms, including activation of phospholipase C and increased Ca2+ influx, and it also regulates adenylyl cyclase activity, both positively and negatively. Multiple kinases have also been reported in their signaling cascades, including protein kinases C and D, extracellular signal-regulated kinase, p38, Src, and phosphatidylinositol-3-kinase. Previous studies have suggested interactions between the orexin and endocannabinoid systems. The endocannabinoid system consists of endocannabinoids, which are neuromodulatory lipids produced on demand by neurons, their effectors (CB1 and CB2 cannabinoid receptors, as well as other receptors and channels), and finally the enzymes that degrade them. The cannabinoid and orexin systems have several overlapping functions, such as regulation of pain transmission, appetite, learning, and reward. Evidence for the existence of interactions between these systems has been gained from physiological, but also molecular studies. Even heteromerization of CB1 and OX1 receptors has been reported. In this thesis, the signaling of the OX1 receptor was further investigated, with special emphasis on lipid mediators. Recombinant cells (mainly CHO cells) were employed as model systems. We were able to directly demonstrate the activation of phospholipase D upon OX1 stimulation, and consequently add PLD to the signaling cascades mediating orexin responses. Phospholipase D activation was mediated by a novel protein kinase C isoform, most likely protein kinase Cδ. OX1 receptor activation also leads to the release of two other messengers: arachidonic acid and the endocannabinoid 2-arachidonoylglycerol. In this thesis, the release of these messengers and the pathways leading to their production, upon orexin receptor activation, were investigated in detail for the first time. Powerful arachidonic acid release by cytosolic phospholipase A2 (cPLA2) was observed in recombinant CHO cells. In contrast, 2-arachidonoylglycerol was released by a cascade involving activation of phospholipase C and diacyglycerol lipase; this was observed in CHO, neuro-2a, and HEK293 cells. By utilizing CHO cells in an artificial cell−cell communication assay, we saw that the released 2-arachidonoyl¬glycerol can act as a paracrine messenger, activating neighboring cells expressing CB1 cannabinoid receptors. 2-Arachidonoylglycerol similarly also acted as an autocrine messenger, and co-signaling of OX1 and CB1 receptors upon orexin stimulation of the receptor-co-expressing cells via the "2-arachidonoylglycerol loop" led to the potentiation of ERK activation. This implies that the significance of the previously reported OX1−CB1 interaction is more likely to originate from functional than physical interaction of the receptors. However, the idea of heteromerization between OX1 and CB1 receptors is interesting, and in the final study of the present series, we utilized the bioluminescence resonance energy transfer (BRET) method to investigate constitutive homo- and heteromerization between OX1, OX2, and CB1 receptors. According to our results, all receptor combinations readily form heteromeric complexes when expressed in CHO cells.
  • Tuominen, Esa (Helsingin yliopisto, 2011)
    The ability of the peripherally associated membrane protein cytochrome c (cyt c) to bind phospholipids in vitro was studied using fluorescence spectroscopy and large unilamellar liposomes. Previous work has shown that cyt c can bind phospholipids using two distinct mecha- nisms and sites, the A-site and the C-site. This binding is mediated by electrostatic or hydrophobic interactions, respectively. Here, we focus on the mechanism underlying these interactions. A chemically modified cyt c mutant Nle91 was used to study the ATP-binding site, which is located near the evolutionarily invariant Arg 91 on the protein surface. This site was also demonstrated to mediate phospholipid binding, possibly by functioning as a phospholipid binding site. Circular dichroism spectroscopy, time resolved fluorescence spectroscopy of zinc- porphyrin modified [Zn2+-heme] cyt c and liposome binding studies of the Nle91 mutant were used to demonstrate that ATP induces a conformational change in membrane- bound cyt c. The ATP-induced conformational changes were mediated by Arg 91 and were most pronounced in cyt c bound to phospholipids via the C-site. It has been previously reported that the hydrophobic interaction between phospho- lipids and cyt c (C-site) includes the binding of a phospholipid acyl chain inside the protein. In this mechanism, which is known as extended phospholipid anchorage, the sn-2 acyl chain of a membrane phospholipid protrudes out of the membrane surface and is able to bind in a hydrophobic cavity in cyt c. Direct evidence for this type of bind- ing mechanism was obtained by studying cyt c/lipid interaction using fluorescent [Zn2+- heme] cyt c and fluorescence quenching of brominated fatty acids and phospholipids. Under certain conditions, cyt c can form fibrillar protein-lipid aggregates with neg- atively charged phospholipids. These aggregates resemble amyloid fibrils, which are involved in the pathogenesis of many diseases. Congo red staining of these fibers con- firmed the presence of amyloid structures. A set of phospholipid-binding proteins was also found to form similar aggregates, suggesting that phospholipid-induced amyloid formation could be a general mechanism of amyloidogenesis.
  • Laurinavicius, Simonas (Helsingin yliopisto, 2008)
    In this study we used electro-spray ionization mass-spectrometry to determine phospholipid class and molecular species compositions in bacteriophages PM2, PRD1, Bam35 and phi6 as well as their hosts. To obtain compositional data of the individual leaflets, phospholipid transbilayer distribution in the viral membranes was studied. We found that 1) the membranes of all studied bacteriophage are enriched in PG as compared to the host membranes, 2) molecular species compositions in the phage and host membranes are similar, and 3) phospholipids in the viral membranes are distributed asymmetrically with phosphatidylglycerol enriched in the outer leaflet and phosphatidylethanolamine in the inner one (except Bam35). Alternative models for selective incorporation of phospholipids to phages and for the origins of the asymmetric phospholipid transbilayer distribution are discussed. Notably, the present data are also useful when constructing high resolution structural models of bacteriophages, since diffraction methods cannot provide a detailed structure of the membrane due to high motility of the lipids and lack of symmetric organization of membrane proteins.
  • Peltovuori, Tommi (Helsingin yliopisto, 2006)
    An overwhelming majority of all the research on soil phosphorus (P) has been carried out with soil samples taken from the surface soils only, and our understanding of the forms and the reactions of P at a soil profile scale is based on few observations. In Finland, the interest in studying the P in complete soil profiles has been particularly small because of the lack of tradition in studying soil genesis, morphology, or classification. In this thesis, the P reserves and the retention of orthophosphate phosphorus (PO4-P) were examined in four cultivated mineral soil profiles in Finland (three Inceptisols and one Spodosol). The soils were classified according to the U.S. Soil Taxonomy and soil samples were taken from the genetic horizons in the profiles. The samples were analyzed for total P concentration, Chang and Jackson P fractions, P sorption properties, concentrations of water-extractable P, and for concentrations of oxalate-extractable Al and Fe. Theoretical P sorption capacities and degrees of P saturation were calculated with the data from the oxalate-extractions and the P fractionations. The studied profiles can be divided into sections with clearly differing P characteristics by their master horizons Ap, B and C. The C (or transitional BC) horizons below an approximate depth of 70 cm were dominated by, assumingly apatitic, H2SO4-soluble P. The concentration of total P in the C horizons ranged from 729 to 810 mg kg-1. In the B horizons between the depths of 30 and 70 cm, a significant part of the primary acid-soluble P has been weathered and transformed to secondary P forms. A mean weathering rate of the primary P in the soils was estimated to vary between 230 and 290 g ha-1 year-1. The degrees of P saturation in the B and C horizons were smaller than 7%, and the solubility of PO4-P was negligible. The P conditions in the Ap horizons differed drastically from those in the subsurface horizons. The high concentrations of total P (689-1870 mg kg-1) in the Ap horizons are most likely attributable to long-term cultivation with positive P balances. A significant proportion of the P in the Ap horizons occurred in the NH4F- and NaOH-extractable forms and as organic P. These three P pools, together with the concentrations of oxalate-extractable Al and Fe, seem to control the dynamics of PO4-P in the soils. The degrees of P saturation in the Ap horizons were greater (8-36%) than in the subsurface horizons. This was also reflected in the sorption experiments: Only the Ap horizons were able to maintain elevated PO4-P concentrations in the solution phase − all the subsoil horizons acted as sinks for PO4-P. Most of the available sorption capacity in the soils is located in the B horizons. The results suggest that this capacity could be utilized in reducing the losses of soluble P from excessively fertilized soils by mixing highly sorptive material from the B horizons with the P-enriched surface soil. The drastic differences in the P characteristics observed between adjoining horizons have to be taken into consideration when conducting soil sampling. Sampling of subsoils has to be made according to the genetic horizons or at small depth increments. Otherwise, contrasting materials are likely to be mixed in the same sample; and the results of such samples are not representative of any material present in the studied profile. Air-drying of soil samples was found to alter the results of the sorption experiments and the water extractions. This indicates that the studies on the most labile P forms in soil should be carried out with moist samples.
  • Väänänen, Riitta (2008)
    Phosphorus (P) retention properties of soils typical for boreal forest, i.e. podzolic soil and peat soils, vary significantly, but the range of this variation has not been sufficiently documented. To assess the usefulness of buffer zones used in forestry in removing P from the discharge by chemical sorption in soil, and to estimate the risk of P leaching after forestry operations, more data is needed on soil P retention properties. P retention properties of soils were studied at clear-cut areas, unharvested buffer zones adjoining the clear-cut and at peatland buffer zone areas. Desorption-sorption isotherms were determined for the humus layer, the mineral soil horizons E, B and C of the Podzol profile and for the surface layer peat (0-15 cm) and the subsurface layer peat (15-30 cm). The efficiency of buffer zones in retaining P was studied at six peatland buffer zone areas by adding P-containing solute in the inflow. A tracer study was conducted at one of the buffer zone areas to determine the allocation of the added P in soil and vegetation. Measured sorption or desorption rather than parameter values of fitted sorption equations described P desorption and sorption behaviour in soil. The highest P retention efficiency was in the B horizon and consequently, if contact occurred or was established between the soluble P in the water and the soil B horizon, the risk of P leaching was low. Humus layer was completely incapable of retaining P after clear-cutting. In the buffer zones, the decrease in P retention properties in the humus layer and the low amount of P sorbed by it indicated that the importance of the layer in the functioning of buffer zones is low. The peatland buffer zone areas were efficient in retaining soluble P from inflow. P sorption properties of the peat soil at the buffer zone areas varied largely but the contribution of P sorption in the peat was particularly important during high flow in spring, when the vegetation was not fully developed. Factors contributing to efficient P retention were large buffer size and low hydrological load whereas high hydrological load combined with the formation of preferential flow paths, especially during early spring or late autumn was disadvantageous. However, small buffer zone areas, too, may be efficient in reducing P load.
  • Lignell, Hanna (Helsingin yliopisto, 2014)
    In this thesis, fundamentally and atmospherically relevant species, their heterogeneous chemistry, and photolytic processing in multiple phases are explored both experimentally and computationally, providing important new insights and mechanistic understanding of these complicated systems. HArF is a covalently bonded neutral ground-state molecule of argon that is found to form at very low temperatures. This thesis explores the HArF low temperature formation mechanism and kinetics, and discusses the effect of the environment to the formation. In the next part, a computational study of an atmospherically relevant molecule N2O4 and its isomerization and ionization on model ice and silica surfaces is presented. N2O4 is known to produce HONO, which is a major source of atmospheric OH, an important atmospheric oxidant. The isomerization mechanism is found to be connected to the dangling surface hydrogen atoms at both surfaces, and we suggest that this mechanism could be expanded to other atmospherically relevant surfaces as well. Atmospheric aerosols play a critical role in controlling climate, driving chemical reactions in the atmosphere, acting as surfaces catalyzing heterogeneous reactions, and contributing to air pollution problems and indoor air quality issues. Low-volatility organic compounds that are produced in the oxidation of biogenic and anthropogenic Volatile Organic Compounds (VOC s) are known collectively as Secondary Organic Aerosol (SOA). In this thesis, a comprehensive investigation of aqueous photochemistry of cis-pinonic acid, a common product of ozonolysis of α-pinene (an SOA precursor) is presented. Various experimental techniques are used to study the kinetics, photolysis rates, quantum yields, and photolysis products, and computational methods are used to explore the photolysis mechanisms. Atmospheric implications and importance of aqueous photolysis vs. OH-mediated aging is discussed. The viscosity effects on SOA chemistry are then explored by a novel approach where an environmentally relevant probe molecule 2,4-dinitrophenol is embedded directly inside the SOA matrix, and its photochemistry is studied at different temperatures and compared to reaction efficiency in other reaction media (octanol and water). It is observed that decreasing temperature significantly slows down the photochemical process in the SOA matrix, and this behavior is ascribed to increasing viscosity of the SOA material.
  • Isoniemi, Esa (Helsingin yliopisto, 2003)
  • Kulmala, Liisa (Helsingin yliopisto, 2011)
    Research on carbon uptake in boreal forests has mainly focused on mature trees, even though ground vegetation species are effective assimilators and can substantially contribute to the CO2 uptake of forests. Here, I examine the photosynthesis of the most common species of ground vegetation in a series of differently aged Scots pine stands, and at two clear-cut sites with substantial differences in fertility. In general, the biomass of evergreen species was highest at poor sites and below canopies, whereas grasses and herbs predominated at fertile sites and open areas. Unlike mosses, the measured vascular species showed clear annual cycles in their photosynthetic activity, which increased earlier and decreased later in evergreen vascular species than in deciduous species. However, intraspecific variation and self-shading create differences in the overall level of photosynthesis. Light, temperature history, soil moisture and recent possible frosts could explain the changes in photosynthesis of low shrubs and partially also some changes in deciduous species. Light and the occurrence of rain events explained most of the variation in the photosynthesis of mosses. The photosynthetic production of ground vegetation was first upscaled, using species-specific and mass-based photosynthetic activities and average biomass of the site, and then integrated over the growing season, using changes in environmental factors. Leaf mass-based photosynthesis was highest in deciduous species, resulting in notably higher photosynthetic production at fertile sites than at poor clear-cut sites. The photosynthetic production decreased with stand age, because flora changed towards evergreen species, and light levels diminished below the canopy. In addition, the leaf mass-based photosynthetic activity of some low shrubs declined with the age of the surrounding trees. Different measuring methods led to different momentary rate of photosynthesis. Therefore, the choice of measuring method needs special attention.
  • Jansen, Gunther (Helsingin yliopisto, 2009)
    Understanding the overwhelming diversity of life calls for complex organisational schemes. The field of systematics may thus be seen as the cornerstone of evolutionary biology. In the last few decades, systematics has been rejuvenated through the introduction of molecular methods such as DNA barcoding and multi-gene phylogenetic approaches. These methods may shed new light on established taxonomic ideas and problems. For example, the classification of ants has aroused much debate due to reinterpretation of morphological characters or contradictions between molecular data and morphology. Only in the last few years a consensus was reached regarding the phylogeny of ant subfamilies. However, the situation remains deplorable for lower taxonomic ranks such as subfamilies, tribes and genera. This thesis describes the systematics and evolution of the Holarctic ant genus Myrmica and the tribe to which it belongs, Myrmicini. Using barcoding, molecular-phylogenetic data and divergence time estimations, it addresses questions regarding the taxonomy, morphology and biogeography of this group. Furthermore, the interrelationships between socially parasitic Myrmica species and their hosts (other species in the genus) were inferred. The phylogeny suggests that social parasitism evolved several times in Myrmica. Finally, this thesis investigated whether coevolution shaped the phylogeny of socially parasitic Maculinea butterflies that live inside Myrmica colonies. No evidence was found for coevolution.