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  • Inkinen, Ville (Helsingfors universitet, )
    In June 2012, the Commission introduced the Monitoring and Reporting Regulation (601/2012) by virtue of Article 14(1) of the ETS Directive (2003/87/EC). In recital 2 of the MRR the Commission puts forward an interpretation of the Renewable Energy Directive which marks a major policy change. According to the interpretation, the sustainability criteria for biofuels and bioliquids in Article 17 of the Renewable Energy Directive must be fulfilled as a precondition to the rule in Annex IV of the ETS Directive according to which emissions from the use biomass shall be considered zero. Applying the sustainability criteria in the Renewable Energy Directive results from the interpretation that biomass zero-treatment constitutes ‘financial support’ within the meaning of Article 17(1)(c) of the Renewable Energy Directive. Presently, due to the limited use of biofuels and bioliquids in the Emissions Trading sector, the policy change is of minor significance. However, the Commission is preparing a proposal to introduce sustainability criteria also for solid and gaseous biomass in heating and cooling and electricity. The proposal is expected to be formally tabled in fall 2013. In many Member States, emissions from the use of solid biomass are significant as compared to the current emissions in the whole Emissions Trading sector, and thus the economic consequences can be major. The treatment of emissions from solid biomass is also likely to have major implications for the Member States in fulfilling their binding national targets under the Renewable Energy Directive. Firstly, this study analyses the described interaction between the ETS Directive and the RED. The main finding in this regard is that the interpretation whereby biomass zero-treatment would constitute ‘financial support’ within the meaning of Article 17(1)(c) of the Renewable Energy Directive is highly problematic. Secondly, the competence of the Commission in amending the Annex IV of the ETS Directive is examined. This study posits that the Commission does not have the competence to modify biomass zero-treatment to the extent of imposing a precondition to fulfil the sustainability criteria. Lastly, the upcoming sustainability criteria for solid and gaseous biomass will be briefly discussed. The upcoming criteria will resemble those for biofuels and bioliquids with some alterations. Pivotal with respect to biomass zero-treatment will be the wording of the upcoming provisions. If the norm requiring fulfilling the criteria to be eligible for financial support will be formulated in the same manner as in the Renewable Energy Directive, the interpretation in recital 2 of the Monitoring and Reporting Regulation could have the result that the upcoming extension will apply in the Emissions Trading Scheme automatically.
  • Välimäki, Niko (Helsingin yliopisto, 2012)
    Recent advancements in the field of compressed data structures create interesting opportunities for interdisciplinary research and applications. Compressed data structures provide essentially a time--space tradeoff for solving a problem; while traditional data structures use extra space in addition to the input, compressed data structures replace the input and require space proportional to the compressed size of the input. The amount of available memory is often fixed, thus, the user might be willing to spend more time if it allows the use of larger inputs. However, despite the potential behind compressed data structures, they have not quite reached the audience of other disciplines. We study how to take advantage of compressed data structures in the fields of bioinformatics, data analysis and information retrieval. We present several novel applications for compressed data structures and include an experimental evaluation of the time--space tradeoffs achieved. More precisely, we propose (i) a space-efficient string mining algorithm to recognise substrings that admit the given frequency constraints, (ii) both theoretical and practical methods for computing approximate overlaps between all string pairs, (iii) a practical path-based graph kernel for predicting the function of unknown enzymatic reactions, and (iv) a compressed XML index that supports efficient XPath queries on both the tree-structure and textual content of XML documents. Problem (i) is motivated by knowledge discovery in databases, where the goal is to extract emerging substrings that discriminate two (or more) databases. Problem (ii) is one of the first phases in a sequence assembly pipeline and requires efficient algorithms due to the new high-throughput sequencing systems. Problem (iii) is motivated by machine learning, where kernels are used to measure the similarity of complex objects. Problem (iv) has its background in information retrieval. The proposed methods achieve theoretical and practical improvements over the earlier state of the art. To raise the overall awareness of compressed data structures, our results have been published in interdisciplinary forums, including conferences and journals from the fields of bioinformatics, data engineering and data mining.
  • Zahabi, Seyedali (Helsingin yliopisto, 2013)
    This thesis investigates different aspects of conformal field theory and string theory and their applications in statistical properties of systems. First, we study the free fermions in planar Ising model and its scaling limit at criticality. On the one hand, we examine the relation between the transfer matrix formalism and discrete holomorphicity. We show that the fermion operators of the Ising model satisfy a complexification of the defining relations of s-holomorphicity, a strong notion of discrete holomorphicity, and examples of fermion correlation functions are shown to reproduce s-holomorphic parafermionic observables. On the other hand, we study the relation between fermionic conformal field theory and Schramm Loewner evolution by focusing on the interfaces and fermionic correlation functions of the Ising model. We demonstrate an explicit, rigorous realization of the CFT/SLE correspondence in the case of Ising model. Second, we develop a statistical framework for bosonic string theory in order to study transport properties of black holes in the context of membrane paradigm. We find that the shear viscosity of a highly excited bosonic string is equal to that of black hole horizon up to a numerical factor.
  • Ylinen, Pekka (Helsingin yliopisto, 2006)
    The aim of the present experimental study was to find out if the applications of coralline hydroxyapatite (HA) can be improved by using bioabsorbable containment or binding substance with particulate HA in mandibular contour augmentation and by using bioabsorbable fibre-reinforced HA blocks in filling bone defects and in anterior lumbar interbody fusion. The use of a separate curved polyglycolide (PGA) containment alone or together with a fast resorbing polyglycolide/polylactide (PGA/PLA) binding substance were compared to the conventional non-contained method in ridge augmentation in sheep. The contained methods decreased HA migration, but the augmentations did not differ significantly. The use of the containment caused a risk for wound dehiscence and infection. Histologically there was a rapid connective tissue ingrowth into the HA graft and it was more abundant with the PGA containment compared to the non-contained augmentation and even additionally rich when the HA particles were bound with PGA/PLA copolymer. However, the bone ingrowth was best in the non-contained augmentation exceeding 10-12 % of the total graft area at 24 weeks. Negligible or no bone ingrowth was seen in the cases where the polymer composite was added to the HA particles and, related to that, foreign-body type cells were seen at the interface between the HA and host bone. The PGA and poly-dl/l-lactide (PDLLA) fibre-reinforced coralline HA blocks were studied in the metaphyseal and in the diaphyseal defects in rabbits. A rapid bone ingrowth was seen inside the both types of implants. Both PGA and PDLLA fibres induced an inflammatory fibrous reaction around themselves but it did not hinder the bone ingrowth. The bone ingrowth pattern was directed according to the loading conditions so that the load-carrying cortical ends of the implants as well as the implants sited in the diaphyseal defects were the most ossified. The fibre-reinforced coralline HA implants were further studied as stand-alone grafts in the lumbar anterior interbody implantation in pigs. The strength of the HA implants proved not to be adequate, the implants fractured in six weeks and the disc space was gradually lost similarly to that of the discectomized spaces. Histologically, small quantities of bone ingrowth was seen in some of the PGA and PDLLA reinforced coralline implants while no bone formation was identified in any of the PDLLA reinforced synthetic porous HA implants. While fragmented, the inner structure of the implants was lost, the bone ingrowth was minimal, and the disc was replaced by the fibrous connective tissue. When evaluated radiologically the grade of ossification was assessed as better than histologically, and, when related to the histologic findings, CT was more dependable than the plain films to show ossification of the implanted disc space. Local kyphosis was a frequent finding along with anterior bone bridging and ligament ossification as a consequence of instability of the implanted segment.
  • Markkanen, Tommi (Helsingin yliopisto, 2014)
    Cosmic inflation is a phase of accelerating, nearly exponential expansion of the spacetime fabric of the Universe, which is assumed to have taken place almost immediately after the Big Bang. Inflation possesses the appealing property that it provides solutions to deep cosmological problems, such as the flatness and horizon problems, and also gives a natural origin for the formation of the large scale structures we observe today. In this thesis we set out to investigate the role quantum corrections play for some simple models where inflation is driven by a single scalar field. It is essential that here the quantum corrections are calculated via curved space field theory. In this technique one quantizes only the matter fields, the dynamics of which take place on a curved classical background. This approach is rarely used in mainstream cosmology and it has the benefit that it allows the quantum fluctuations to back-react on classical Einsteinian gravity. The curved space quantum corrections are studied first in the effective action formalism via the Schwinger-DeWitt expansion and then by constructing effective equations of motion by using the slow-roll technique. We also focus on consistent renormalization and show how to renormalize the effective equations of motion without any reference to an effective action for an interacting theory in curved spacetime. Due to a potential infrared enhancement in effective equations in quasi-de Sitter space, we also perform a resummation of Feynman diagrams in curved non-static space and observe that it regulates the infrared effects. Concerning implications for actual inflationary models, we focus on chaotic type models and observe the quantum corrections to be insignificant, but nevertheless to have theoretically a non-trivial structure.
  • Vepsäläinen, Mikko (Helsingin yliopisto, 2007)
    When heated to high temperatures, the behavior of matter changes dramatically. The standard model fields go through phase transitions, where the strongly interacting quarks and gluons are liberated from their confinement to hadrons, and the Higgs field condensate melts, restoring the electroweak symmetry. The theoretical framework for describing matter at these extreme conditions is thermal field theory, combining relativistic field theory and quantum statistical mechanics. For static observables the physics is simplified at very high temperatures, and an effective three-dimensional theory can be used instead of the full four-dimensional one via a method called dimensional reduction. In this thesis dimensional reduction is applied to two distinct problems, the pressure of electroweak theory and the screening masses of mesonic operators in quantum chromodynamics (QCD). The introductory part contains a brief review of finite-temperature field theory, dimensional reduction and the central results, while the details of the computations are contained in the original research papers. The electroweak pressure is shown to converge well to a value slightly below the ideal gas result, whereas the pressure of the full standard model is dominated by the QCD pressure with worse convergence properties. For the mesonic screening masses a small positive perturbative correction is found, and the interpretation of dimensional reduction on the fermionic sector is discussed.
  • Tahkokallio, Touko (Helsingin yliopisto, 2008)
    The description of quarks and gluons, using the theory of quantum chromodynamics (QCD), has been known for a long time. Nevertheless, many fundamental questions in QCD remain unanswered. This is mainly due to problems in solving the theory at low energies, where the theory is strongly interacting. AdS/CFT is a duality between a specific string theory and a conformal field theory. Duality provides new tools to solve the conformal field theory in the strong coupling regime. There is also some evidence that using the duality, one can get at least qualitative understanding of how QCD behaves at strong coupling. In this thesis, we try to address some issues related to QCD and heavy ion collisions, applying the duality in various ways.
  • Ryynänen, Heikki (Helsingin yliopisto, 2006)
    Evolutionary genetics incorporates traditional population genetics and studies of the origins of genetic variation by mutation and recombination, and the molecular evolution of genomes. Among the primary forces that have potential to affect the genetic variation within and among populations, including those that may lead to adaptation and speciation, are genetic drift, gene flow, mutations and natural selection. The main challenges in knowing the genetic basis of evolutionary changes is to distinguish the adaptive selection forces that cause existent DNA sequence variants and also to identify the nucleotide differences responsible for the observed phenotypic variation. To understand the effects of various forces, interpretation of gene sequence variation has been the principal basis of many evolutionary genetic studies. The main aim of this thesis was to assess different forms of teleost gene sequence polymorphisms in evolutionary genetic studies of Atlantic salmon (Salmo salar) and other species. Firstly, the level of Darwinian adaptive evolution affected coding regions of the growth hormone (GH) gene during the teleost evolution was investigated based on the sequence data existing in public databases. Secondly, a target gene approach was used to identify within population variation in the growth hormone 1 (GH1) gene in salmon. Then, a new strategy for single nucleotide polymorphisms (SNPs) discovery in salmonid fishes was introduced, and, finally, the usefulness of a limited number of SNP markers as molecular tools in several applications of population genetics in Atlantic salmon was assessed. This thesis showed that the gene sequences in databases can be utilized to perform comparative studies of molecular evolution, and some putative evidence of the existence of Darwinian selection during the teleost GH evolution was presented. In addition, existent sequence data was exploited to investigate GH1 gene variation within Atlantic salmon populations throughout its range. Purifying selection is suggested to be the predominant evolutionary force controlling the genetic variation of this gene in salmon, and some support for gene flow between continents was also observed. The novel approach to SNP discovery in species with duplicated genome fragments introduced here proved to be an effective method, and this may have several applications in evolutionary genetics with different species - e.g. when developing gene-targeted markers to investigate quantitative genetic variation. The thesis also demonstrated that only a few SNPs performed highly similar signals in some of the population genetic analyses when compared with the microsatellite markers. This may have useful applications when estimating genetic diversity in genes having a potential role in ecological and conservation issues, or when using hard biological samples in genetic studies as SNPs can be applied with relatively highly degraded DNA.
  • Mykkänen, Anne-Mari (Helsingin yliopisto, 2012)
    In this thesis we use lattice field theory to study different frontier problems in strongly coupled non-Abelian gauge theories, focusing on large-N models and walking technicolor theories. Implementing lattice studies of technicolor theories, we consider the SU(2) gauge theory with two fermions transforming under the adjoint representation, which constitutes one of the candidate theories for technicolor. The early lattice Monte Carlo studies of this model have used an unimproved Wilson fermion formulation. However, large lattice cutoff effects can be expected with the unimproved formulation, and so we present the calculation of the O(a) improved lattice Wilson-clover action. In addition to the adjoint representation fermions, we also determine the improvement coefficients for SU(2) gauge theory with two fundamental representation fermions. In another work, we study the deconfined phase of strongly interacting matter, investigating Casimir scaling and renormalization properties of Polyakov loops in different irreducible representations, in SU(N) gauge theories at finite temperature. We study the approach to the large-N limit by performing lattice simulations of Yang-Mills theories with gauge groups from SU(2) to SU(6), taking the twelve lowest irreducible representations for each gauge group into consideration. We find clear evidence of Casimir scaling and identify the temperature dependence of the renormalized Polyakov loops. The third study I present is related to the long-standing idea of non-Abelian gauge theories having a close relation to some kind of string theory. In the confining regime of SU(N) gauge theories, the flux lines between well separated color sources are expected to be squeezed in a thin, stringlike tube, and the interaction between the sources can be described by an effective string theory. One of the consequences of the effective string description at zero temperature is the presence of the Luescher term - a Casimir effect due to the finiteness of the interquark distance - in the long distance interquark potential. To study the validity of this effective model, we compute the static quark potential in SU(3) and SU(4) Yang-Mills theories through lattice simulations, generalizing an efficient `multilevel' algorithm proposed by Luescher and Weisz to an improved lattice action.
  • Pääkkönen, Kimmo (Helsingin yliopisto, 2003)
  • Collin, Anssi (Helsingin yliopisto, 2006)
  • Ropponen, Olli (Helsingin yliopisto, 2011)
    This thesis is composed of an introductory chapter and four applications each of them constituting an own chapter. The common element underlying each of the chapters is the econometric methodology. The applications rely mostly on the leading econometric techniques related to estimation of causal effects. The first chapter introduces the econometric techniques that are employed in the remaining chapters. Chapter 2 studies the effects of shocking news on student performance. It exploits the fact that the school shooting in Kauhajoki in 2008 coincided with the matriculation examination period of that fall. It shows that the performance of men declined due to the news of the school shooting. For women the similar pattern remains unobserved. Chapter 3 studies the effects of minimum wage on employment by employing the original Card and Krueger (1994; CK) and Neumark and Wascher (2000; NW) data together with the changes-in-changes (CIC) estimator. As the main result it shows that the employment effect of an increase in the minimum wage is positive for small fast-food restaurants and negative for big fast-food restaurants. Therefore, it shows that the controversial positive employment effect reported by CK is overturned for big fast-food restaurants and that the NW data are shown, in contrast to their original results, to provide support for the positive employment effect. Chapter 4 employs the state-specific U.S. data (collected by Cohen and Einav [2003; CE]) on traffic fatalities to re-evaluate the effects of seat belt laws on the traffic fatalities by using the CIC estimator. It confirms the CE results that on the average an implementation of a mandatory seat belt law results in an increase in the seat belt usage rate and a decrease in the total fatality rate. In contrast to CE, it also finds evidence on compensating-behavior theory, which is observed especially in the states by the border of the U.S. Chapter 5 studies the life cycle consumption in Finland, with the special interest laid on the baby boomers and the older households. It shows that the baby boomers smooth their consumption over the life cycle more than other generations. It also shows that the old households smoothed their life cycle consumption more as a result of the recession in the 1990s, compared to young households.
  • Wang, Ziran (2013)
    This thesis considers the problem of finding a process that, given a collection of news, can detect significant dates and breaking news related to different themes. The themes are unsupervisedly learned from some training corpora, and they mostly have intuitive meanings, like "finance", "disaster", "wars" and so on. They are constructed only based on textual information provided in the corpora without any human intervention. To conduct this learning, the thesis use various types of component models, specifically Latent Dirichlet Allocation(LDA) and Correlated Topic Model(CTM). On top of that, to enrich the experiment, the Latent Semantic Indexing(LSA) and Multinomial Principal Component Analysis(MPCA) are also adopted for comparison. The learning produces every news coverage a relevance weight for given theme, which can be viewed as a theme distribution from statistical perspective. With the help of news time-stamp information, one can sum up and normalize these distributions from all news in day unit, and then draw the moving of accumulated relevance weights on a theme through time-line. It is natural to treat these curves as describing attention strength paid from media to different themes, and one can assume that behind every peak, there are striking events and associated news can be detected. This thesis is valuable in Media Studies research, and also can be further connected to stock or currency market for creating real value.
  • Kuosmanen, Natalia (Helsingin yliopisto, 2014)
    Sustainability is a multidimensional concept that encompasses environmental, social and economic dimensions. A large number of qualitative concepts and definitions of sustainability have been suggested. However, quantifying the notion of sustainability as an operational measure has proved challenging due to a variety of meanings attached to this concept. The aim of this dissertation is to contribute to quantitative assessment of sustainability, focusing on agriculture. The thesis consists of an introductory part and five articles, which approach the assessment of sustainability from different angles. The main objective of the first three studies is to develop a general framework for sustainability assessment at different levels of aggregation. The first study demonstrates the critical importance of separating the conceptual definition of sustainability from the questions concerning its empirical assessment. The following two articles apply the generalized framework proposed in the first article to sustainability assessment at farm and sector levels. The proposed approach utilizes existing methods of frontier estimation that are applied for productivity and efficiency analysis. Apart from the conventional nonparametric Data Envelopment Analysis (DEA) and parametric Stochastic Frontier Analysis (SFA), a recently developed Stochastic Nonparametric Envelopment of Data (StoNED) approach, is applied in this thesis. The last two articles of the thesis focus on a specific measurement issue within sustainability assessment: how to measure nutrient emissions from agriculture to water, soil, and air. Analyzing stocks and flows of nutrients requires dynamic modeling. The fourth article proposes a new dynamic approach to model the nutrient stocks and flows and demonstrates the advantages of the proposed dynamic model over the conventional static approaches to material balance accounting. The empirical applicability and usefulness of the dynamic model are demonstrated through an empirical application to Finnish agricultural sector where the stocks and flows of nitrogen and phosphorus are estimated for a 48-year period. In the fifth article, the analysis is extended to cover 14 European countries in years 1961 2009. The proposed dynamic material balance approach allows one to analyze the development of nutrient stock over time and decompose the nutrient flows to water, air and soil. The stocks and flows calculated using the dynamic model can be readily utilized in sustainability assessment as indicators of environmental pressure. Apart from the theoretical contribution, last two articles of the thesis open up interesting new avenues for future research; for example, disaggregating nutrient stocks and flows to the level of individual farms or regions presents an interesting but challenging research problem.
  • Nygård, Jenni (Helsingfors universitet, )
    Osakkeiden merkintähinnan maksamista niin, että merkitsijä luovuttaa merkintähinnan maksuksi kokonaan tai osittain muuta omaisuutta kuin rahaa, kutsutaan apportiksi ja apporttina luovutettavaa omaisuutta apporttiomaisuudeksi. Apporttiomaisuuden käyttö on sallittua, mutta sen on katsottu olevan erityisen sääntelyn tarpeessa, sillä vastikkeen maksaminen apporttiomaisuudella voi olla taloudellisesti riskialtista muiden merkitsijöiden, itse yhtiön ja yhtiön velkojien kannalta. Merkintähinnan maksamisesta apporttina osakeyhtiötä perustettaessa säännellään OYL 2:6:ssä. Osakeannin yhteydessä apporttimaksusta säädetään OYL 9:12:ssä. Suoran apporttimaksun lisäksi OYL:ssa on huomioitu apporttisäännösten kiertämiseksi tehdyt järjestelyt, mutta tämä jälkiapporttia koskeva sääntely ei ole keskittynyt omaan pykäläänsä OYL:ssa, vaan se sisältyy apporttia koskeviin säännöksiin omana momenttinaan. OYL 10:6:n mukaan optio- tai muusta erityisestä oikeudesta yhtiölle suoritettavan merkintähinnan tai muun vastikkeen maksuun sovelletaan vastaavasti, mitä osakeantia koskevassa 9 luvussa säädetään mm. apportista. Yhtiön osakepääomaa voidaan korottaa esimerkiksi uusmerkinnällä tai osakepääomasijoituksella ja samoin näihin voi soveltaa vastaavasti, mitä OYL 9 luvun 12:ssä säädetään apportista. Vain ne osakkeet, oikeudet ja osakepääomankorotukset, jotka ovat täysin maksettuja, voidaan ilmoittaa rekisteröitäväksi. Ensisijaisesti merkitsijällä todistustaakka siitä, että apporttina on yhtiölle siirtynyt merkintähinnan suuruinen määrä varallisuutta (OYL 2:6.2 ja OYL 9:12.2), mutta vahingonkorvausvastuuseen suhteessa yhtiöön saattavat joutua myös toimitusjohtaja, hallitusten jäsenet sekä tilintarkastaja, jos he vakuuttavat ja todistavat (OYL 2:8.3 ja OYL 9:14.3), että ilmoitettu määrä varallisuutta on siirtynyt yhtiölle, esim. johdon huolellisuusperiaatteen vastaisesti, huolimattomuuttaan (OYL 22 luku). Uudessa OYL:ssa ei ole VOYL:n mukaista säännöstä siitä, että osakkeista maksettavan määrän tulee olla yhtiön ”omistuksessa ja hallinnassa”, jotta maksu katsotaan suoritetuksi, mutta lain esitöiden mukaan tämä ei tarkoita sitä, ettei maksua arvioitaisi edelleen näiden yleisten varallisuusoikeudellisten sääntöjen mukaisesti. Yhtiötä voidaan pitää apporttiomaisuuden omistajana ja merkintähintaa voidaan pitää maksettuna, vaikka luovutusta rasittaisi sivullisen mahdollisuus saannonmoitteeseen. Jos osakeyhtiön hallitus eikä toimitusjohtaja ole tienneet eikä heidän olisi pitänyt tietää siitä, että apporttina luovutettavaa omaisuutta rasittaa kolmannen oikeus, saa yhtiö myös muiden saantosuojan edellytysten täyttyessä osakseen ekstinktion. Saannon siirtohetken edellytyksesi voidaan asettaa velkojansuojan saamishetken, sillä tällöin voidaan olla varmoja sitovuudesta merkitsijän ulosmittaus- ja konkurssivelkojia kohtaan, joka on esineoikeudellisessa kirjallisuudessa asetettu merkityksellisesti hetkeksi. Sitoumus työn tai palvelun suorittamiseen ei voi olla apporttiomaisuutta (OYL 2:6.1 ja OYL 9:12.1). Apport-tiomaisuutta voivat olla omistusoikeus kiinteään tai irtaimeen omaisuuteen, saamisoikeudet, immateriaalioikeudet ja osuusoikeudet, kunhan ne ovat siirrettävissä ja merkittävissä yhtiön taseeseen varallisuudeksi, sillä omaisuudella on oltava taloudellista arvoa yhtiölle. Pantattua ja kiinnitettyä omaisuutta voidaan luovuttaa yhtiölle apporttina panttirasituksen ylittävältä osalta. Erillisten omaisuuserien luovuttamisen lisäksi on mahdollista, että omaisuuserien muodostaessa yhtenäisen arvokkaan kokonaisuuden, voidaan tämä luovuttaa yhtiölle kokonaisuutena (esim. liike tai liiketoimintakokonaisuus). Luovutettaessa yhtiölle apporttina kiinteistöä, tulee noudattaa MK 4:3:een perustuen MK 2 luvun säännöksiä soveltuvin osin muun muassa kiinteistön luovutusta yhtiöön osaketta tai muuta osuutta vastaan.
  • Sipiläinen, Ulla (1999)