| 1. |
- Boisvert, Catherine Anne, 1978-
(author)
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The Origin of Tetrapod Limbs and Girdles: Fossil and Developmental Evidence
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Around 375 million years ago, the first tetrapods appeared, marking one of the most important events in vertebrate evolutionary history. The fin to limb transition saw the appearance of fingers and a weight bearing pelvic girdle. While very little research has been done on the evolution of the tetrapod pelvic girdle, a fair amount has been done on the origins of fingers but some aspects remained controversial. A combination of palaeontology, developmental biology and comparative morphology was therefore used in this thesis to better understand the fin to limb transition. The pectoral fin of Panderichthys, a sarcopterygian fish closely related to tetrapods was CT-scanned and modeled in three dimensions and its pelvic girdle and fin were examined with traditional techniques. This information from the fossil record was integrated with comparisons of the development of the Australian lungfish, Neoceratodus forsteri, our closest living fish relative and the axolotl (Ambystoma mexicanum), a salamander representing well the condition of early tetrapods. Development of bone and cartilage was studied through clearing and staining and development of skeletal muscles through immunostaining. In situ hybridizations were performed on the lungfish to study the expression of Hoxd13, associated with the formation of digits in tetrapods. This work shows that the late expression phase of Hoxd13 is present in Neoceratodus and is associated with the formation of radials. Redescription of the pectoral fin of Panderichthys reveals that distal radials are present, which, in addition to other information, lead us to conclude that digits are not novelties in tetrapods but rather have evolved from the distal radials present in the fins of all sarcopterygian fish. The earliest tetrapods lack a full set of wrist + carpals/ankle + tarsal bones. Here, we propose that this region of the limbs evolved after fingers and toes through an expansion of the region between the proximal limb bones and the digits. As for the pelvic girdle, it is very primitive in Panderichthys but comparison of its development in Neoceratodus and Ambystoma suggest that the ischium evolved through the posterior expansion of the pubis and the ilium, through an elongation of the iliac process already present in sarcopterygian fishes. The results of this thesis help to better understand the fin to limb transition and show that it is more gradual than previously believed.
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| 2. |
- Ericsson, Rolf
(author)
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A Comparative Study of Head Development in Mexican Axolotl and Australian Lungfish: Cell Migration, Cell Fate and Morphogenesis
- 2003
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Doctoral thesis (other academic/artistic)abstract
- The development of the vertebrate head is a complex process involving interactions between a multitude of cell types and tissues. This thesis describes the development of the cranial neural crest and of the visceral arch muscles in the head of two species. One, the Mexican axolotl (Ambystoma mexicanum), is a basal tetrapod, whereas the other, the Australian lungfish (Neoceratodus forsteri), belongs to the Dipnoi, the extant sister group of the Tetrapoda. The migration of neural crest cells, which form most of the bones and connective tissues in the head, and the morphogenesis of the jaw, was determined in the Mexican axolotl. It was shown that both the upper and lower jaws form from ventral condensations of neural crest cells in the mandibular arch. The dorsal condensation, earlier considered to give rise to the upper jaw, was shown to form the trabecula cranii.The normal spatio-temporal development of visceral arch muscles was investigated in both the Mexican axolotl and the Australian lungfish. In axolotl, the muscles tended to start forming almost simultaneously in all visceral arches at their future origins and extend towards their future insertions at the onset of muscle fibre formation. In lungfish, fibres formed simultaneously throughout most of each muscle anlage in the first and second visceral arch, but were delayed in the branchial arches. The anlagen were first observed at their future insertion, from which they developed towards future origins. To test the ability of neural crest cells to pattern the visceral arch muscles, migrating crest cells were extirpated from axolotl embryos, which resulted in a wide range of muscle malformations. In most cases, the muscles appeared in the right position but were small and extended in abnormal directions. This shows that neural crest cells are responsible not for the position of the muscles but for their correct anatomical pattern. Fate mapping showed that connective tissue surrounding myofibers is, at least partly, neural crest derived.In conclusion, the work presented in this thesis shows that although early development may map out the patterns of later development, the differences between axolotl and lungfish head development are not seen until during morphogenesis. Further investigation of morphogenesis is needed to explain the great variation of head morphology seen in vertebrates today.
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| 3. |
- Holmquist, Mats, 1954-
(author)
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Lärande nätverk : En social oas i utvecklingsprocessen
- 2010
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Doctoral thesis (other academic/artistic)abstract
- Intresset för nätverk mellan organisationer växer i arbetslivet. Fler och fler chefer, ledare och ansvariga går med i nätverk för att få stöd i sitt utvecklingsarbete. Varför? Vad är det för speciellt med lärande i nätverk? Vad får individen och organisationen ut? Mina egna och kollegors erfarenheter från tio års praktiskt arbete i fem nätverk i Halland, har gett mig en unik tillgång till data för att söka svar på frågorna.Med hjälp av flervetenskaplig teori och tidigare empirisk forskning har jag skapat en modell över nätverk som stöd i utvecklingsprocessen. Modellen har jag använt till att analysera mina data för att förstå lärprocessen i nätverk, vilka förutsättningar och organiseringsformer som är viktiga för att stimulera det kollektiva lärande som uppstår i samverkan mellan olika individer och organisationer. Jag har även undersökt vad deltagandet ger i utbyte och vad som stödjer respektive hindrar en transformering till organisatorisk nytta och förändring.Resultaten visar att nätverk fungerar som en social oas för chefer och ledare, som kan vara ganska ensamma och osäkra i sitt arbete. De uppskattar en plats där de kan möta andra i en liknande situation, för att under tillitsfulla former utbyta erfarenheter och reflektera över sina handlingsalternativ. Deltagarnas olikheter tillför variationer som stimulerar ett kreativt lärande och genererar innovativa idéer.I stort sett alla deltagare är mycket positiva till nätverkformen. Utbytet är huvudsakligen personliga insikter och kunskaper i form av ökat självförtroende, reducerad osäkerhet och stärkt förändringskompetens. Deltagandet ger även inspiration, idéer och organisatoriska förändringsförslag. När dessa sedan ska föras över från nätverket till organisationen möter dock deltagarna ofta svårigheter och hinder.Organisationernas förmåga att absorbera nätverksresultaten brister. De har många gånger svårt att ta tillvara nya kunskaper och idéer, att integrera nätverkslärande med organisatoriskt lärande och därmed svårt att utnyttja den utvecklingspotential som nätverk rymmer. Viktiga hinder är strategi- och förankringsbrist på ledningsnivån.Nätverkets styrka som en stödjande social oas för deltagaren i utvecklingsprocessen rymmer också en svaghet. Utbytet riskerar att begränsas till personlig bekräftelse och bidra till få organisatoriska förändringar. För att undvika detta behöver deltagarens, organisationens och nätverkets utvecklingssyfte tydliggöras från början.Analysen leder fram till en idealmodell av en utvecklingsprocess med stöd av nätverk. I modellen stimulerar gemensamma reflektionen över praktiska erfarenheter ett kreativt lärande som ger nya kunskaper och idéer i utbyte. När dessa ska överföras och tillämpas i verksamheten behövs en utvecklingsorganisation med en ledning som kan ta ett strategiskt helhetsgrepp över förändringsprocessen.Slutsatserna talar för lärande nätverk som ett stöd i utvecklingsprocessen. De talar för fortsatt forskning för att pröva idealmodellen och för att fördjupa kunskaperna om absorberingssvårigheten och strategibristen.
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| 4. |
- Karlsson, Lennart, 1947-
(author)
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Arbetarrörelsen, Folkets Hus och offentligheten i Bromölla 1905-1960
- 2009
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Doctoral thesis (other academic/artistic)abstract
- The purpose of this dissertation is to analyze the People’s House in Bromölla as an arena for a plebeian public sphere. More specific, the analysis revolves around how the labour movement created a plebeian public sphere, the construction of the very arena and the activities there, including study circles, labour library, theatre plays, film showings, dance evenings and other amusements as parts of adult education among the working class people. It also comprises examinations of the labour movement’s acting in the local political arena, the labour movement’s connections with the local bourgeoisie on matters concerning politics and the People’s House. The main theoretical perspective is based on Jürgen Habermas’ theory of bourgeois public sphere, reformulated to a plebeian public sphere. The adult education in study circles mainly focused on subjects related to the work in the local politics and in the trade union, i.e. for the activities in the public sphere. These parts of the adult education were primarily a matter for the male part of the labour movement. This mirrors the situation in politics and in the trade union, where foremost men were engaged. Beside the trade union and political studies, subjects like Swedish, English, Esperanto, mathematics and literature were common. From time to time socialism and Marxism were studied. The women mainly studied humanistic subjects with individual development and hold thus the vision of the education ideologists within the labour movement. In the 1940’s the study circles decreased, and finally, in the end of the 1950’s almost ceased. Despite this the education did not cease, but were replaced by music, singing, dancing and machine sewing courses arranged by commercial companies and aesthetic associations. The People’s House was from the beginning open even for associations outside the labour movement. In the 1940’s and, in particularly, the 1950’s the People’s House became an assembly hall for a huge range of associations. Among the tenants were Free Church parishes, athletic associations, hobby associations, temperance societies, political parties from left to right, trade unions, authorities, companies, and the municipal of Bromölla. People’s house was also a place for wedding and birthday celebrations and other private parties. Among the more frequent tenants were Free Churches and music, singing and athletic associations, beside Bromölla municipal, which were a permanent tenant, for instance for the municipal library. The amount of associations from outside the labour movement among the tenants exceeded for some years in the end of 1950’s the labour movement’s meetings. This cross class policy was a conscious strategy by the People’s House association, in order to be a cultural institution for all inhabitants in Bromölla. The municipal council of Bromölla was even a part of this policy when subsidizing the People’s House association. It was in accordance with the cross class and consensus policy which the social democratic movement by this time was an exponent of. The People’s House in Bromölla was thus an arena not only for the labour movement, but also for the entire society.
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| 5. |
- Olsson, Erik, 1967-
(author)
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Heart Rate Variability in Stress-related Fatigue, Adolescent Anxiety and Depression and its Connection to Lifestyle
- 2010
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Doctoral thesis (other academic/artistic)abstract
- Heart rate varies constantly as a consequence of activity in the sympathetic and parasympathetic autonomic nervous systems (SNS and PNS). In short-term recordings, heart rate variability (HRV) is mostly related to the inhibitory activity of the vagal nerves, which are part of the PNS. HRV is lower when under stress as well as in several illnesses and psychiatric conditions. Decreased HRV is also related to cardiac disease, which is the leading cause of death worldwide. Autonomic imbalance, measured as HRV, is suggested as a mediator between psychosocial distress and cardiovascular disease. The aim of the present thesis was to investigate the connection between HRV and psychosocial distress, including psychiatric problems (studies I and II), and lifestyle factors (study III). In study I, additional physiological measures sensitive to autonomic activity and results from a continuous attention test were investigated in parallel with HRV. In studies II and III the participants were adolescents. The results show that HRV is lower in women with stress-related fatigue and adolescent girls with a psychiatric diagnosis compared to healthy control groups. However, these groups did not exhibit an increase in physiological measures of SNS origin, which supports the assumption that the observed hyperarousal is related to decreased vagal activity rather than increased SNS activity. Women with stress-related fatigue made more impulsive errors and had a “risky” response style in the continuous attention test. There was a negative correlation between test performance and HRV. Decreased vagal activity is thus associated with deficient behavioural inhibition. In study III, HRV in a group of healthy adolescent boys and girls was positively associated with physical activity but not with other lifestyle measures. Even at young age HRV is a sensitive marker of autonomic imbalance resulting from psychosocial stress. Future longitudinal research will show whether HRV can be used for early identification of people at risk of cardiovascular disease and whether such interventions will lower the risk of cardiac morbidity.
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| 6. |
- Olsson, Erik, 1986-
(author)
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Micromechanics of Powder Compaction
- 2015
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Doctoral thesis (other academic/artistic)abstract
- Compaction of powders followed by sintering is a convenient manufacturing method for products of complex shape and components of materials that are difficult to produce using conventional metallurgy. During the compaction and the handling of the unsintered compact, defects can develop which could remain in the final sintered product. Modeling is an option to predict these issues and in this thesis micromechanical modeling of the compaction and the final components is discussed. Such models provide a more physical description than a macroscopic model, and specifically, the Discrete Element Method (DEM) is utilized.An initial study of the efect of particle size distribution, performed with DEM, was presented in Paper A. The study showed that this effect is small and is thus neglected in the other DEM studies in this thesis. The study also showed that good agreement with experimental data can be obtained if friction effects is correctly accounted for.The most critical issue for accurate results in the DEM simulations is the modeling of normal contact between the powder particles. A unified treatment of this problem for particles of a strain hardening elastic-plastic material is presented in Paper B. Results concerning both the elastic-plastic loading, elastic unloading as well as the adhesive bonding between the particles is included. All results are compared with finite element simulation with good agreement with the proposed model.The modeling of industry relevant powders, namely spray dried granules is presented in Paper C. The mechanical behavior of the granules is determined using two types of micromechanical experiments, granule compression tests and nanoindentation testing. The determined material model is used in an FEM simulation of two granules in contact. The resulting force-displacement relationships are exported to a DEM analysis of the compaction of the granules which shows very good agreement with corresponding experimental data.The modeling of the tangential forces between two contacting powder particles is studied in Paper D by an extensive parametric study using the finite element method. The outcome are correlated using normalized parameters and the resulting equations provide the tangential contact force as function of the tangential displacement for different materials and friction coefficients.Finally, in Paper E, the unloading and fracture of powder compacts, made of the same granules as in Paper C, are studied both experimentally and numerically. A microscopy study showed that fracture of the powder granules might be of importance for the fracture and thus a granule fracture model is presented and implemented in the numerical model. The simulations show that incorporating the fracture of the granules is essential to obtain agreement with the experimental data.
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| 7. |
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| 8. |
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| 9. |
- Olsson, Lennart
(author)
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Signal processing applied to acoustic distance estimation and sound classification
- 1993
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Doctoral thesis (other academic/artistic)abstract
- The thesis treats some signal processing applications to retrieval of information from acoustic measurements. In the distance estimation applications (parts AI, A2, B and C) an acoustic signal propagates through a physical system and is modified according to some system parameter. In the classification problem (parts D1 and D2) the acoustic signal is modified due to the circumstances of its generation. Finally, the design of a signal processor (part E) is described. In the pulse-echo method the parameter to estimate is the propagation time of a reflected acoustic signal. Due to the narrowband bandpass characteristic of ultrasound transducers, the echoes are represented by relatively long duration responses. When multiple echoes from surfaces closely spaced in range are obtained, they are partly overlapping, which causes a resolution problem. A general solution to this problem is to design an excitation signal and a corresponding receiver filter, based on the transducer unit pulse response, to give the shortest possible response at the receiver filter output and simultaneously a minimum acceptable output signal-to-noise ratio. In parts AI and A2 a suboptimal solution has been developed using a combination of resolution enhancement filtering, split between the transmitter and the receiver, and a signal-to-noise ratio increasing pulse compression technique. In part B, a system using airborne focused ultrasound to record a topographic map of a skin surface, is studied. A problem encountered in estimating the time delay for the single echoes from an arbitrarily shaped surface is that the echo shape depends on the local properties of the surface. This introduces a systematic error in the estimate. Dense scanning of the surface and applying a two-dimensional averaging filter to the matrix of range data have reduced the errors to an acceptable level. In part C a method, based on modelling an ore pass as a one-dimensional acoustic tube, has been developed to estimate the position of the border between the empty and the filled parts. The wave propagation in the acoustic tube is modelled as a lattice structure. The parameters of this structure have a direct physical interpretation as reflection coefficients. The border between the empty and the filled parts will correspond to a large reflection coefficient in the lattice model and its location will indicate the ore level. Frequency independent attenuation is incorporated in the model and it is shown how the estimated parameters are affected. A method to separately estimate the forward propagating wave, leads to acceptable results when the model parameters are estimated by an autoregressive model algorithm. In parts D1 and D2 classification methods are applied to secondary sounds emitted by shock wave lithotripsy, used to disintegrate kidney stones inside the body. The objective of the sound classification is to get knowledge of some parameter of the sound generation. In shock wave lithotripsy the acoustic excitation is made outside the body and the waves are focused at the stone location. The positioning of the acoustic focus relative to the stone is critical to achieve the maximum fragmenting effect on the stone. It has been found that the timbre of the audible part of the emitted secondary sound is affected by this. The classification methods have been based on the spectral properties of the sounds. In a method presented in part D1 the parameters of an autoregressive signal model are used as features for classification. A second method developed in part D2 is based on the expansion of logarithmic spectra of the sounds in a set of orthogonal base functions. The coefficients of this expansion are used as features. The base functions are obtained by singular value decomposition of a set of representative spectra. Both methods successfully discriminates between the desired cases, provided that a calibration has been carried out for each new patient. In part E the design of a signal processor, used in conjunction with the work presented in part C, is described. It was designed to accelerate part of the calculations in the algorithm. This design was carried out before standard signal processors became available. Programming tools were also developed.
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| 10. |
- Olsson, Magnus, 1975-
(author)
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On optimal hydropower bidding in systems with wind power : Modeling the impact of wind power on power markets
- 2009
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Doctoral thesis (other academic/artistic)abstract
- The introduction of large amounts of wind power into power systems will increase the production uncertainties due to unforeseen wind power production variations. This will have a significant impact on the required balance management quantities. The most suitable power source to balance fast production or consumption variations is hydropower because of its flexibility and low operational costs. This thesis addresses the problem of trading of electricity on the daily marketfrom a hydropower producer perspective in a system with large amounts of wind power. The overall aim is to present models that can be used in the trading decision process. This thesis describes models within three different areas:1. Modeling of the demand for balancing power by using deterministic andstochastic models. The stochastic models are based on stochastic differentialequations.2. Modeling of prices on the day-ahead and real-time markets using deterministic and stochastic models. The stochastic models are based on time series modeling.3. Short-term hydropower scheduling of trading decisions. These problems areformulated as stochastic optimization problems where the market prices arerandom variables. The first two can be used to simulate the impact of wind power on various market prices, while the third simulates how the hydropower producer responds to market prices. Thereby, the thesis presents the necessary models for short-term scheduling of hydropower for a future system with significant amounts of wind power. This thesis concludes that the proposed price models are sufficient to reflect the relevant price properties, and that the proposed short-term hydropower scheduling models can be used to simulate the actions taken by the hydropower producer in a system with significant amounts of wind power. This is also supported by the case studies in the appended publications.
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