Non-Gaussianities and Preheating from N-flation and Magnetogenesis via rotating cosmic string loops

In this thesis we examine multi-field inflationary models of the early Universe. Since non-Gaussianities may allow for the possibility to discriminate between models of inflation, we compute deviations from a Gaussian spectrum of primordial perturbations by extending the delta-N formalism. We use N-flation as a concrete model; our findings show that these models are generically indistinguishable as long as the slow roll approximation is still valid. Besides computing non-Guassinities, we also investigate Preheating after multi-field inflation. Within the framework of N-flation, we find that preheating via parametric resonance is suppressed, an indication that it is the old theory of preheating that is applicable. In addition to studying non-Gaussianities and preheatng in multi-field inflationary models, we study magnetogenesis in the early universe. To this aim, we propose a mechanism to generate primordial magnetic fields via rotating cosmic string loops. Magnetic fields in the micro-Gauss range have been observed in galaxies and clusters, but their origin has remained elusive. We consider a network of strings and find that rotating cosmic string loops, which are continuously produced in such networks, are viable candidates for magnetogenesis with relevant strength and length scales, provided we use a high string tension and an efficient dynamo.

Hydrogen soil deposition and atmospheric variations in the boreal zone

This research has been prompted by an interest in the atmospheric processes of hydrogen. The sources and sinks of hydrogen are important to know, particularly if hydrogen becomes more common as a replacement for fossil fuel in combustion. Hydrogen deposition velocities (vd) were estimated by applying chamber measurements, a radon tracer method and a two-dimensional model. These three approaches were compared with each other to discover the factors affecting the soil uptake rate. A static-closed chamber technique was introduced to determine the hydrogen deposition velocity values in an urban park in Helsinki, and at a rural site at Loppi. A three-day chamber campaign to carry out soil uptake estimation was held at a remote site at Pallas in 2007 and 2008. The atmospheric mixing ratio of molecular hydrogen has also been measured by a continuous method in Helsinki in 2007 - 2008 and at Pallas from 2006 onwards. The mean vd values measured in the chamber experiments in Helsinki and Loppi were between 0.0 and 0.7 mm s-1. The ranges of the results with the radon tracer method and the two-dimensional model were 0.13 - 0.93 mm s-1 and 0.12 - 0.61 mm s-1, respectively, in Helsinki. The vd values in the three-day campaign at Pallas were 0.06 - 0.52 mm s-1 (chamber) and 0.18 - 0.52 mm s-1 (radon tracer method and two-dimensional model). At Kumpula, the radon tracer method and the chamber measurements produced higher vd values than the two-dimensional model. The results of all three methods were close to each other between November and April, except for the chamber results from January to March, while the soil was frozen. The hydrogen deposition velocity values of all three methods were compared with one-week cumulative rain sums. Precipitation increases the soil moisture, which decreases the soil uptake rate. The measurements made in snow seasons showed that a thick snow layer also hindered gas diffusion, lowering the vd values. The H2 vd values were compared to the snow depth. A decaying exponential fit was obtained as a result. During a prolonged drought in summer 2006, soil moisture values were lower than in other summer months between 2005 and 2008. Such conditions were prevailing in summer 2006 when high chamber vd values were measured. The mixing ratio of molecular hydrogen has a seasonal variation. The lowest atmospheric mixing ratios were found in the late autumn when high deposition velocity values were still being measured. The carbon monoxide (CO) mixing ratio was also measured. Hydrogen and carbon monoxide are highly correlated in an urban environment, due to the emissions originating from traffic. After correction for the soil deposition of H2, the slope was 0.49±0.07 ppb (H2) / ppb (CO). Using the corrected hydrogen-to-carbon-monoxide ratio, the total hydrogen load emitted by Helsinki traffic in 2007 was 261 t (H2) a-1. Hydrogen, methane and carbon monoxide are connected with each other through the atmospheric methane oxidation process, in which formaldehyde is produced as an important intermediate. The photochemical degradation of formaldehyde produces hydrogen and carbon monoxide as end products. Examination of back-trajectories revealed long-range transportation of carbon monoxide and methane. The trajectories can be grouped by applying cluster and source analysis methods. Thus natural and anthropogenic emission sources can be separated by analyzing trajectory clusters.

Studies on Binary Time Series Models with Applications to Empirical Macroeconomics and Finance

This thesis studies binary time series models and their applications in empirical macroeconomics and finance. In addition to previously suggested models, new dynamic extensions are proposed to the static probit model commonly used in the previous literature. In particular, we are interested in probit models with an autoregressive model structure. In Chapter 2, the main objective is to compare the predictive performance of the static and dynamic probit models in forecasting the U.S. and German business cycle recession periods. Financial variables, such as interest rates and stock market returns, are used as predictive variables. The empirical results suggest that the recession periods are predictable and dynamic probit models, especially models with the autoregressive structure, outperform the static model. Chapter 3 proposes a Lagrange Multiplier (LM) test for the usefulness of the autoregressive structure of the probit model. The finite sample properties of the LM test are considered with simulation experiments. Results indicate that the two alternative LM test statistics have reasonable size and power in large samples. In small samples, a parametric bootstrap method is suggested to obtain approximately correct size. In Chapter 4, the predictive power of dynamic probit models in predicting the direction of stock market returns are examined. The novel idea is to use recession forecast (see Chapter 2) as a predictor of the stock return sign. The evidence suggests that the signs of the U.S. excess stock returns over the risk-free return are predictable both in and out of sample. The new "error correction" probit model yields the best forecasts and it also outperforms other predictive models, such as ARMAX models, in terms of statistical and economic goodness-of-fit measures. Chapter 5 generalizes the analysis of univariate models considered in Chapters 2 4 to the case of a bivariate model. A new bivariate autoregressive probit model is applied to predict the current state of the U.S. business cycle and growth rate cycle periods. Evidence of predictability of both cycle indicators is obtained and the bivariate model is found to outperform the univariate models in terms of predictive power.

Atmospheric particle formation in spatially and temporally varying conditions

Atmospheric particles affect the radiation balance of the Earth and thus the climate. New particle formation from nucleation has been observed in diverse atmospheric conditions but the actual formation path is still unknown. The prevailing conditions can be exploited to evaluate proposed formation mechanisms. This study aims to improve our understanding of new particle formation from the view of atmospheric conditions. The role of atmospheric conditions on particle formation was studied by atmospheric measurements, theoretical model simulations and simulations based on observations. Two separate column models were further developed for aerosol and chemical simulations. Model simulations allowed us to expand the study from local conditions to varying conditions in the atmospheric boundary layer, while the long-term measurements described especially characteristic mean conditions associated with new particle formation. The observations show statistically significant difference in meteorological and back-ground aerosol conditions between observed event and non-event days. New particle formation above boreal forest is associated with strong convective activity, low humidity and low condensation sink. The probability of a particle formation event is predicted by an equation formulated for upper boundary layer conditions. The model simulations call into question if kinetic sulphuric acid induced nucleation is the primary particle formation mechanism in the presence of organic vapours. Simultaneously the simulations show that ignoring spatial and temporal variation in new particle formation studies may lead to faulty conclusions. On the other hand, the theoretical simulations indicate that short-scale variations in temperature and humidity unlikely have a significant effect on mean binary water sulphuric acid nucleation rate. The study emphasizes the significance of mixing and fluxes in particle formation studies, especially in the atmospheric boundary layer. The further developed models allow extensive aerosol physical and chemical studies in the future.

A Model for Creating Strategic Alliances. A Study of Inter-firm Cooperation in the North European ICT Sector

In this study, it is argued that the view on alliance creation presented in the current academic literature is limited, and that using a learning approach helps to explain the dynamic nature of alliance creation. The cases in this study suggest that a wealth of inefficiency elements can be found in alliance creation. These elements can further be divided into categories, which help explain the dynamics of alliance creation. The categories –combined with two models brought forward by the study– suggest that inefficiency can be avoided through learning during the creation process. Some elements are especially central to this argumentation. First, the elements related to the clarity and acceptance of the strategy of the company, the potential lack of an alliance strategy and the elements related to changes in the strategic context. Second, the elements related to the length of the alliance creation processes and the problems a long process entails. It is further suggested that the different inefficiency elements may create a situation, where the alliance creation process is –sequentially and successfully– followed to the end, but where the different inefficiencies create a situation where the results are not aligned with the strategic intent. The proposed solution is to monitor and assess the risk for inefficiency elements during the alliance creation process. The learning, which occurs during the alliance creation process as a result of the monitoring, can then lead to realignments in the process. This study proposes a model to mitigate the risk related to the inefficiencies. The model emphasizes creating an understanding of the other alliance partner’s business, creating a shared vision, using pilot cooperation and building trust within the process. An analytical approach to assessing the benefits of trust is also central in this view. The alliance creation approach suggested by this study, which emphasizes trust and pilot cooperation, is further critically reviewed against contracting as a way to create alliances.

The link between foreign aid, public investment and economic growth

Länsimaat ovat rahoittaneet kehitysyhteistyöhankkeita jo lähes kuuden vuosikymmenen ajan, mutta kehitysavun tehokkuudesta ei olla edelleenkään päästy yksimielisyyteen. Yksi avunantajamaiden tapa vaikuttaa kehitysavun tehokkuuteen, eli avun vaikutukseen vastaanottajamaan taloudellisen kasvun kiihdyttäjänä, on sitoa ne julkisen sektorin infrastruktuurihankkeisiin. Joissain tapauksissa tämä vaikuttaa avun vastaanottajan käytökseen ja asenteisiin kehitysapua kohtaan. Tutkielmassa käsitellään kehitysavun tehokkuutta tilanteessa, jossa se on sidottu julkisen sektorin investointeihin kehitysmaassa. Tutkimus pohjaa Kalaitzidakisin ja Kalyvitisin (2008) malliin, jossa osa kehitysmaan julkisen talouden investoinneista rahoitetaan kehitysavulla. Seuraavaksi tarkastellaan ylijäämää tavoittelevan käyttäytymisen (rent- seeking) vaikutusta kehitysavun tehokkuuteen pohjaten Economidesin, Kalyvitisin ja Philippopoulosin (2008) malliin. Tutkielmassa referoidaan lisäksi tutkimuskysymystä sivuavia empiirisiä tutkimuksia, esitellään aluksi tavallisimmat kehitysyhteistyön muodot, sekä esitellään talousteoreettisia näkökulmia kehitysyhteistyön tehokkuuden määrittelylle. Tutkielma perustuu puhtaasti teoreettisiin malleihin ja niissä sovelletut menetelmät ovat matemaattisia. Tutkielmassa käsitellään ensin tapaus, jossa kehitysyhteistyöllä rahoitetaan julkisen sektorin investointihankkeita. Jossain tapauksissa kehitysavun kasvu lasku siirtää vastaanottajamaan kulutusta julkisista investoinneista kulutukseen, jolloin kehitysyhteistyövaroin osittain rahoitettujen hankkeiden koko pienenee, ja suhteellinen tehokkuus laskee. Seuraavaksi tarkastellaan tilannetta, jossa kehitysyhteistyövaroista vain osa päätyy hankkeen rahoittamiseen, ja todetaan, että kehitysavun tehokkuus ja vaikutus maan kansantulon kasvuun vähenee talouden toimijoiden ylijäämää tavoittelevan käyttäytymisen (mukaan lukien korruptio) myötä entisestään. Tämän tutkimuksen perusteella voidaan todeta, että kehitysapu vaikuttaa kehittyvän maan talouden kasvuun tapauksessa, jossa julkisia infrastruktuurihankkeita rahoitetaan osittain maan omin verovaroin ja osittain kehitysyhteistyövaroin. Ylijäämää tavoitteleva käyttäytyminen vaikuttaa kehitysavun tehokkuuteen negatiivistesti vähentäen kehitysavun positiivisia kasvuvaikutuksia.

Nonlinear mixture autoregressive model: economic applications

The aim of this dissertation is to model economic variables by a mixture autoregressive (MAR) model. The MAR model is a generalization of linear autoregressive (AR) model. The MAR -model consists of K linear autoregressive components. At any given point of time one of these autoregressive components is randomly selected to generate a new observation for the time series. The mixture probability can be constant over time or a direct function of a some observable variable. Many economic time series contain properties which cannot be described by linear and stationary time series models. A nonlinear autoregressive model such as MAR model can a plausible alternative in the case of these time series. In this dissertation the MAR model is used to model stock market bubbles and a relationship between inflation and the interest rate. In the case of the inflation rate we arrived at the MAR model where inflation process is less mean reverting in the case of high inflation than in the case of normal inflation. The interest rate move one-for-one with expected inflation. We use the data from the Livingston survey as a proxy for inflation expectations. We have found that survey inflation expectations are not perfectly rational. According to our results information stickiness play an important role in the expectation formation. We also found that survey participants have a tendency to underestimate inflation. A MAR model has also used to model stock market bubbles and crashes. This model has two regimes: the bubble regime and the error correction regime. In the error correction regime price depends on a fundamental factor, the price-dividend ratio, and in the bubble regime, price is independent of fundamentals. In this model a stock market crash is usually caused by a regime switch from a bubble regime to an error-correction regime. According to our empirical results bubbles are related to a low inflation. Our model also imply that bubbles have influences investment return distribution in both short and long run.

Aspiration-based utility functions in a planning model for timber flow management.

The study presents a theory of utility models based on aspiration levels, as well as the application of this theory to the planning of timber flow economics. The first part of the study comprises a derivation of the utility-theoretic basis for the application of aspiration levels. Two basic models are dealt with: the additive and the multiplicative. Applied here solely for partial utility functions, aspiration and reservation levels are interpreted as defining piecewisely linear functions. The standpoint of the choices of the decision-maker is emphasized by the use of indifference curves. The second part of the study introduces a model for the management of timber flows. The model is based on the assumption that the decision-maker is willing to specify a shape of income flow which is different from that of the capital-theoretic optimum. The utility model comprises four aspiration-based compound utility functions. The theory and the flow model are tested numerically by computations covering three forest holdings. The results show that the additive model is sensitive even to slight changes in relative importances and aspiration levels. This applies particularly to nearly linear production possibility boundaries of monetary variables. The multiplicative model, on the other hand, is stable because it generates strictly convex indifference curves. Due to a higher marginal rate of substitution, the multiplicative model implies a stronger dependence on forest management than the additive function. For income trajectory optimization, a method utilizing an income trajectory index is more efficient than one based on the use of aspiration levels per management period. Smooth trajectories can be attained by squaring the deviations of the feasible trajectories from the desired one.

Bovine mastitis caused by coagulase-negative staphylococci : host response and bacterial factors

Coagulase-negative staphylococci (CNS) are the most common bacteria isolated in bovine subclinical mastitis in many countries, and also a frequent cause of clinical mastitis. The most common species isolated are Staphylococcus (S) chromogenes, S. simulans, S. epidermidis, and S. xylosus. One half of the intramammary infections (IMI) caused by CNS persist in the udder. The pathogenesis of IMI caused by CNS is poorly understood. This dissertation focuses on host response in experimental intramammary infection induced by S. chromogenes, S. epidermidis and S. simulans. Model for a mild experimental CNS infection was developed with S. chromogenes (study I). All cows were infected and most developed subclinical mastitis. In study II the innate immune response to S. epidermidis and S. simulans IMI was compared in eight cows using a crossover design. A larger dose of bacteria was used to induce clinical mastitis. All cows became infected and showed mild to moderate clinical signs of mastitis. S. simulans caused a slightly stronger innate immune response than S. epidermidis, with significantly higher concentrations of the interleukins IL-1beta and IL-8 in the milk. The spontaneous elimination rate of the 16 IMIs was 31%, with no difference between species. No significant differences were recorded between infections eliminated spontaneously or remaining persistent, although the response was stronger in IMIs eliminated spontaneously, except the concentration of TNF-α, which remained elevated in persistent infections. Lactoferrin (Lf) is a component of the humoral defence of the host and is present at low concentrations in the milk. The concentration of Lf in milk is high during the dry period, in colostrum, and in mastitic milk. The effect of an inherent, high concentration of Lf in the milk on experimental IMI induced with S. chromogenes was studied in transgenic cows that expressed recombinant human Lf in their milk. Human Lf did not prevent S. chromogenes IMI, but the host response was milder in transgenic cows than in normal cows, and the former eliminated infection faster. Biofilm production has been suggested to promote persistence of IMI. Phenotypic biofilm formation and slime producing ability of CNS isolates from bovine mastitis was investigated in vitro. One-third of mastitis isolates produced biofilm. Slime production was less frequent for isolates of the most common mastitis causing species S. chromogenes and S. simulans compared with S. epidermidis. No association was found between the phenotypic ability to form biofilm and the persistence of IMI or severity of mastitis. Slime production was associated with persistent infections, but only 8% of isolates produced slime.

Constructing and negotiating entrepreneurial agency : A social psychological approach to entrepreneurship discourse in the farm context

Entrepreneurship, understood as the autonomous, effective pursuit of opportunities regardless of resources, is currently subject to a multitude of interests, expectations, and facilitation efforts. On the one hand, such entrepreneurial agency has broad appeal to individuals in Western market democracies and resonates with their longing for an autonomous, personally tailored, meaningful, and materially rewarding way of life. On the other hand, entrepreneurship represents a tempting and increasingly popular means of governance and policy making, and thus a model for the re-organization of a variety of societal sectors. This study focuses on the diffusion and reception of entrepreneurship discourse in the context of farming and agriculture, where pressures to adopt entrepreneurial orientations have been increasingly pronounced while, on the other hand, the context of farming has historically enjoyed state protection and adhered to principles that seem at odds with aspects of individualistic entrepreneurship discourse . The study presents an interpretation of the psychologically and politically appealing uses of the notion of entrepreneurial agency , reviews the historical and political background of the current situation of farming and agriculture with regard to entrepreneurship, and examines their relationships in four empirical studies. The study follows and develops a social psychological, situated relational approach that guides the qualitative analyses and interpretations of the empirical studies. Interviews with agents from the farm sector aim to stimulate evaluative responses and comments on the idea of entrepreneurship on farms. Analysis of the interview talk, in turn, detects the variety of evaluative responses and argumentative contexts with which the interviewees relate themselves to the entrepreneurship discourse and adopt, use, resist, or reject it. The study shows that despite the pressures towards entrepreneurialism, the diffusion of entrepreneurship discourse and the construction of entrepreneurial agency in farm context encounter many obstacles. These obstacles can be variably related to aspects dealing with the individual agent, the action situation, the characteristics of the action itself, or to the broader social, institutional and cultural context. Many aspects of entrepreneurial agency, such as autonomy, personal initiative and achievement orientation, are nevertheless familiar to farmers and are eagerly related to one s own farming activities. The idea of entrepreneurship is thus rarely rejected outright. The findings highlight the relational and situational preconditions for the construction of entrepreneurial agency in the farm context: When agents demonstrate entrepreneurial agency, they do so by drawing on available and accessed relational resources characteristic of their action context. Likewise, when agents fail or are reluctant to demonstrate entrepreneurial agency, they nevertheless actively account for their situation and demonstrate personal agency by drawing on the relational resources available to them.