Networks of neurons, which form central pattern generators (CPGs), are important for controlling animal behaviors. Of special interest are configurations or CPG motifs composed of reciprocally inhibited neurons, such as half-center oscillators (HCOs). Bursting rhythms of HCOs are shown to include stable synchrony or in-phase bursting. This in-phase bursting can co-exist with anti-phase bursting, commonly expected as the single stable state in HCOs that are connected with fast non-delayed synapses. The finding contrasts with the classical view that reciprocal inhibition has to be slow or time-delayed to synchronize such bursting neurons. Phase-locked rhythms are analyzed via Lyapunov exponents estimated with variational equations, and through the convergence rates estimated with Poincar\'e return maps. A new mechanism underlying multistability is proposed that is based on the spike interactions, which confer a dual property on the fast non-delayed reciprocal inhibition; this reveals the role of spikes in generating multiple co-existing phase-locked rhythms. In particular, it demonstrates that the number and temporal characteristics of spikes determine the number and stability of the multiple phase-locked states in weakly coupled HCOs. The generality of the multistability phenomenon is demonstrated by analyzing diverse models of bursting networks with various inhibitory synapses; the individual cell models include the reduced leech heart interneuron, the Sherman model for pancreatic beta cells, the Purkinje neuron model and Fitzhugh-Rinzel phenomenological model. Finally, hypothetical and experiment-based CPGs composed of HCOs are investigated. This study is relevant for various applications that use CPGs such as robotics, prosthetics, and artificial intelligence.

This dissertation creates practical methods for Poincaré return mappings of individual and networked neuron models. Elliptic bursting models are found in numerous biological systems, including the external Globus Pallidus (GPe) section of the brain; the focus for studies of epileptic seizures and Parkinson's disease. However, the bifurcation structure for changes in dynamics remains incomplete. This dissertation develops computer-assisted Poincaré ́maps for mathematical and biologically relevant elliptic bursting neuron models and central pattern generators (CPGs). The first method, used for individual neurons, offers the advantage of an entire family of computationally smooth and complete mappings, which can explain all of the systems dynamical transitions. A complete bifurcation analysis was performed detailing the mechanisms for the transitions from tonic spiking to quiescence in elliptic bursters. A previously unknown, unstable torus bifurcation was found to give rise to small amplitude oscillations. The focus of the dissertation shifts from individual neuron models to small networks of neuron models, particularly 3-cell CPGs. A CPG is a small network which is able to produce specific phasic relationships between the cells. The output rhythms represent a number of biologically observable actions, i.e. walking or running gates. A 2-dimensional map is derived from the CPGs phase-lags. The cells are endogenously bursting neuron models mutually coupled with reciprocal inhibitory connections using the fast threshold synaptic paradigm. The mappings generate clear explanations for rhythmic outcomes, as well as basins of attraction for specific rhythms and possible mechanisms for switching between rhythms.

Bakgrund: Bonussystem är något som började växa fram på 1980-talet och har sedan dess varit ett omdiskuterat ämne, både här hemma i Sverige och internationellt. Många forskare, politiker och invånare har uppmärksammat de höga ersättningarna som delas ut inom företagen i både bra och dåliga dagar. Det som drog mest uppmärksamhet var att företag trots en finanskris fortsatta med sina utdelningar och t.o.m. ökade sina rörliga ersättningar. Detta fick människor att undra vad företagen egentligen baserar sina ersättningar på. Å andra sidan försvarar företag sig med att dessa ersättningar ger motivation och ökad effektivitet hos de anställda som i sin tur presterar bättre, vilket utvecklar och driver företagen framåt.   Problemformulering: Väljer företagen att basera sina ersättningar på prestationsbaserade eller/och storleksbaserade variabler? Syfte: Syftet med denna studie är att kartlägga vilken av de teoretiska traditionerna som bonussystem baseras på genom att undersöka hur sambandet ser ut mellan utvalda bonusmått och verkställande direktörers och ledande befattningshavarnas totala ersättning under en femårsperiod. Metod: Uppsatsen bygger på en kvantitativ metod där datainsamlingen har skett genom sekundärdata i form av företagens årsredovisningar. Vi har även valt att anta den deduktiva ansatsen som innebär att våra valda teorier ska appliceras på det reslutat som undersökningen visar. Reslutat: Utifrån de tester som gjordes i SPSS programmet visade resultatet att det framgick ett signifikant samband mellan total ersättning och företagets prestation samt företagets storlek. Slutsats: Studien visar att både prestationsbaserade och storleksbaserade variabler visar samband med den totala ersättningen, en övergripande variabel som utformar bolagens ersättningssystem kunde inte konstateras i vår undersökning. Utformningen av ersättningssystem påverkas av inre och yttre faktorer, bl.a. som landets välfärdssystem, företagskultur, konjunkturförändringar.

Syfte: Syftet med denna studie var att kartlägga långtidssjukskrivnas hälsa före och efter avslutad intervention samt studera vilka faktorer som hindrat alternativt främjat återgång i arbete hos individer med tidsbegränsad sjukersättning. Metod: Studien baseras på data från EU-projektet ”SAMKLANG” som är en longitudinell interventionsstudie. Data har samlats in på 59 långtidssjukskrivna deltagare via enkäter både före projektstart och ett år efter och dels har data samlats in kvalitativt genom semistrukturerade intervjuer med 13 deltagare efter det att projektet avslutats. Intervjudeltagarna var indelade i två grupper (de som hade återgått i arbete/studier och de som fortfarande var sjukskrivna). Interventionen bygger på både behandling och samverkan mellan organisationer som är involverade i rehabilitering av personer som har ett år kvar av sin tid i sjukersättning. Resultatet från enkäterna analyserades fram via ANOVA upprepad mätning och data från intervjuerna analyserades via innehållsanalys. Resultat: Huvudresultaten från den kvantitativa delstudien visade att det inte fanns någon skillnad mellan de som efter ett år återgått i arbete/studier, arbetsträning alternativt de som fortfarande var sjukskrivna gällande kön, ålder eller utbildningsnivå. Den självskattade depressions- och ångestnivån minskade och självskattad hälsa och inre kontroll ökade signifikant över tid för den grupp som kommit ut i arbete efter projektet jämfört med de två andra grupperna. Den kvalitativa analysen av intervjuerna identifierade följande tema som stödjande faktorer för arbetsåtergång: att besitta egen drivkraft, ha en insikt om arbetets mervärde och att hitta en balans mellan krav- kontroll-stöd. Det tema som beskriver hur myndigheter kan hjälpa och stödja långtidssjukskrivna tillbaks i arbete är: trygghet med mer vårdkompetens och att synliggöra individuella behov. Slutsats: Att återgå i arbete för en tidigare långtidssjukskriven person kopplas till bättre självrapporterad hälsa med mindre depression och ångestbesvär, en starkare känsla av inre kontroll och en högre tilltro till egen förmåga jämfört med om personer fortfarande är sjukskrivna. Framgångsfaktorer för arbetsåtergång är balans mellan krav, kontroll och stöd för individen och en egen motivation att återgå i arbete. För att underlätta arbetsåtergång hos långtidssjukskrivna bör myndigheter och inblandade parter samverka med vård, erbjuda trygghet och synliggöra varje enskild individs behov av rehabilitering. / Aim: The aim of this study was to investigate long term sickness absentees’ health status before and after an intervention. Furthermore, to gain deeper understanding of factors related to promoting and preventing return to work for people with limited sick leave compensation. Method: The study is based on data from the EU-funded project ”SAMKLANG” which is a longitudinal intervention study. Data has been collected from 59 long term absentees though questionnaires conducted before and one year after the start of the project. Data has also been collected through semi structured interviews from 13 participants after the end of the project. They were divided into two groups (those who had returned to work/studies or had an internship and those who still were sickness absent). The intervention is based on treatment as well as cooperation between organizations involved in a rehabilitation process for people with one year of sick leave compensation remaining. The results from the surveys were analyzed with ANOVA for repeated measures and data from the interviews were analyzed using content analysis. Result: The main result from the quantitative part of this study showed no significant difference in return to work between those who had returned to work or studies, been on internships and those who still were sickness absent based on sex, age and education. The amount of self-rated depression and anxiety levels were reduced and the self-rated health and internal control were significant induced over time for the group who returned to work after the project compared to the other two groups. From the qualitative analyze of the interviews following theme was identified as supporting factors for returning to work: having own motivation, realized the positive in having a job and to have balance between demand-control-support. The theme that describes how the authority can help and support people with long term sickness absence back to work is: security with more competence in healthcare and make individual needs visible. Conclusion: Return to work for a former long term sickness absence is associated with better self-rated health with less depression and anxiety, a stronger feeling of internal control and a higher self-efficacy compared to if persons still were sickness absent. Factors for success in return to work is balance between demand-control-support for the individual and an own motivation to return to work. The authority can facilitate return to work among people with long term sickness absence by interact more with health-care services, offer security and make every individuals need for rehabilitation visible.

Scania’s discount rate - the return requirement of investments - refers to Scania’s WACC or weighted average cost of capital. The capital markets return requirement on equity and the credit market interest cost of borrowing is weighted to become the single discount rate, the WACC. The purpose of this study is to investigate which asset pricing model of APT and CAPM Scania should use in their WACC calculations. The company now uses a group WACC of 11 percent which is used in all company levels. The problem with this is that investments in low-risk markets will be discounted by the same factor as high-risk markets, which can result in a misleading NPV. The objective is to create a differentiated WACC which gives an opportunity to compare investments with different risk profiles. The study proposes the best fitting model, given by evaluating APT and CAPM in a Scania context. To achieve a differentiated WACC a new method is created, The JCJ-Method. The method uses an industry index as a benchmark of Scania. The results indicate that APT is the better model for Scania in the differentiating context. / Carl-Johan Peel

The paper examines the investment performance of the world automotive industry using a sample of 21 original equipment manufacturers (OEMs) based in three major continents, North America, Europe and Asia between the years 1999 and 2004. The empirical findings suggest that there exists persistent overinvestment not only in the global level but also in the major automotive production regions analyzed. Proving that none of the 3 regions gain returns on investment at least as large as their costs of capital, shareholder wealth is not maximized in the world automotive industry. Europe, among these regions, proves to gain the highest return on investment of its cost of capital. The empirical results also show that the return on investment financed by debt is high around the world and close to 100% of its cost of capital.

With increasing demand of electric power in the context of deregulated electricity markets, a good strategic planning for the growth of the power system is critical for our tomorrow. There is a need to build new resources in the form of generation plants and transmission lines while considering the effects of these new resources on power system operations, market economics and the long-term dynamics of the economy. In deregulation, the exercise of generation planning has undergone a paradigm shift. The first stage of generation planning is now undertaken by the individual investors. These investors see investments in generation capacity as an increasing business opportunity because of the increasing market prices. Therefore, the main objective of such a planning exercise, carried out by individual investors, is typically that of long-term profit maximization. This thesis presents some modeling frameworks for generation capacity expansion planning applicable to independent investor firms in the context of power industry deregulation. These modeling frameworks include various technical and financing issues within the process of power system planning. The proposed modeling frameworks consider the long-term decision making process of investor firms, the discrete nature of generation capacity addition and incorporates transmission network modeling. Studies have been carried out to examine the impact of the optimal investment plans on transmission network loadings in the long-run by integrating the generation capacity expansion planning framework within a modified IEEE 30-bus transmission system network. The work assesses the importance of arriving at an optimal IRR at which the firm’s profit maximization objective attains an extremum value. The mathematical model is further improved to incorporate binary variables while considering discrete unit sizes, and subsequently to include the detailed transmission network representation. The proposed models are novel in the sense that the planning horizon is split into plan sub-periods so as to minimize the overall risks associated with long-term plan models, particularly in the context of deregulation.

This thesis documents the design and fabrication of an experimental facility that was built to produce a turbulent plane wall jet. The target flow was two-dimensional with a uniform profile of the mean streamwise velocity and a low turbulence level at the slot exit. The design requirements for a flow conditioning apparatus that could produce this flow were determined. The apparatus was then designed and constructed, and measurements of the fluid flow were obtained using particle image velocimetry (PIV). The first series of measurements was along the slot width, the second series was along the slot centerline and the third was at 46 slot heights off the centerline. The Reynolds number, based on the slot height and jet exit velocity, of the wall jet varied from 7594 to 8121. Data for the streamwise and transverse components of velocity and the three associated Reynolds stress components were analyzed and used to determine the characteristics of the wall jet.<p> This experimental facility was able to produce a profile of the mean streamwise velocity near the slot exit that was uniform over 71% of the slot height with a streamwise turbulence that was equal to 1.45% of the mean velocity. This initial velocity was maintained to 6 slot heights. The fully developed region for the centerline and the off-centerline measurements was determined to extend from 50 to 100 slot heights and 40 to 100 slot heights, respectively. This was based on self-similarity of the mean streamwise velocity profiles when scaled using the maximum streamwise velocity and the jet half-width. The off-centerline Reynolds stress profiles achieved a greater degree of collapse than did the centerline profiles.<p> The rate of spread of the wall jet along the centerline was 0.080 in the self-similar region from 50 to 100 slot heights, and the off-centerline growth rate was 0.077 in the self-similar region from 40 to 100 slot heights. The decay rate of the maximum streamwise velocity was -0.624 within the centerline self-similar region, and -0.562 within the off-centerline self-similar region. These results for the spread and decay of the wall jet compared well with recent similar studies.<p> The two-dimensionality was initially assessed by measuring the mean streamwise velocity at 1 slot height along the entire slot width. The two-dimensionality of this wall jet was further analyzed by comparing the centerline and off-centerline profiles of the mean streamwise velocity at 2/3, 4, 50, 80, and 100 slot heights, and by comparing the growth rates and decay rates. Although this facility was able to produce a wall jet that was initially two-dimensional, the two-dimensionality was compromised downstream of the slot, most likely due to the presence of return flow and spanwise spreading. Without further measurements, it is not yet clear exactly how the lack of complete two-dimensionality affects the flow characteristics noted above.

Climate change is predicted to increase rates of fire activity in boreal forests. A shortened fire return interval may result in different outcomes of community structure in the northern boreal forest, since the age of a forest influences seed production and potential post-fire regeneration. With two closely timed fires, dominant boreal conifers such as black spruce (Picea mariana) may be vulnerable to regeneration failures after fire because of the long time required to reach reproductive maturity. I report on the relationship between stand age and seed productivity of black spruce in northern Yukon Territory and central Alaska. I used fire history maps to select sites of various stand ages, including stand ages that would occur in a short fire return interval (less than 80 years) versus longer fire intervals (up to 200 years). At each site, I measured stand density and basal area using the point-center-quarter method. Ten black spruce trees were randomly selected for cone surveys and age analysis. I also selected a subset of five trees for detailed analyses of cone and seed production within yearly cohorts. The results of this study illustrate the strong relationships between stand age and stand basal area with cone and seed production of northern black spruce. The resulting equations can be used to predict the seed capacity and regeneration potential of black spruce stands with known stand basal area or stand age. I estimate, along with the number of seeds required to produce a two year old black spruce seedling on high quality seedbeds, stands burned at an age less than 50 years will likely have reduced black spruce post-fire density. On low quality seedbeds, black spruce forests are more vulnerable to regeneration failures and fire cycles less than 150 years are likely to result in reduced recruitment. Under a shortened fire return interval these northern black spruce forests are likely to have reduced post-fire density.

Following the development and popularity of mutual funds among Swedish investors, the question of active fund management and return has become a central issue for private investors. 99 percent of the Swedish population invests in mutual funds, comprising a total net fund value of almost 2,000 billion SEK. The idea behind active management is for a charged fee, to generate a return higher than the return of the market. But statistics indicate a low level of competition between the largest providers and only one out of ten funds performs better than its index. Financial instability due to the last decade’s two recessions has indeed caused fluctuating performance of actively managed Swedish mutual funds. It has also spurred academics to investigate the role and effect of active management and attached management fees. The main purpose of this research is to investigate if there exist differences between the performance of benchmark indices and the performance of actively managed equity funds, balanced funds and money market funds provided by seven Swedish banks; Folksam, Länsförsäkringar, Handelsbanken, Nordea, SEB, Skandia and Swedbank. We also seek to investigate if the level of fee and total risk affect the fund performance. The research was deductively conducted with a quantitative method of inquiry. The ontological and epistemological positions are objectivism and positivism. Our sample of 21 Swedish mutual funds, with daily price observations was investigated between 2004 and 2011, with a division of four subperiods. To answer our research question and sub-questions, ten fictive portfolios were created and five hypotheses were formulated based on previous research and theories within the field. The data was analyzed with paired samples T-tests and multiple linear regression analyses. The portfolios included three risk-adjusted fund performance measures and Value at Risk.     We have concluded that on average both balanced funds and money market funds have performed worse than their benchmark indices in the period 2004 to 2011. The equity funds have also performed worse than their benchmark index but the difference is not statistically significant. The balanced funds had the highest return, the money market funds second highest return and equity funds the lowest return. Supported by the multiple regression analyses, we have concluded that fund performance is negatively related to the level of total risk in the period 2004 to 2011. There is no statistical relationship between fund performance and fund provider. We finally conclude that fund return during the entire investigation period, is negatively related to management fees.