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- Pérez-Loya, J. J.
(författare)
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Analysis and control of magnetic forces in synchronous machines
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In a synchronous machine, radial, tangential, and axial forces are generated. In this thesis, three different technologies to control them are proposed. The first one, involves the utilization of the radial forces that arise between the rotor and the stator. This is achieved by segmenting the rotor field winding into groups of poles and controlling their corresponding magnetization individually. This technology is particularly useful to achieve magnetic balance and to create controllable radial forces. The second technology, involves the control of the rotor field in order to influence the tangential forces that produce torque. This is achieved by inverting the rotor field winding polarity with respect to the stator field. With this technique, breaking and accelerating torques can be created. It is particularly useful to start a synchronous machine. Finally, the application of axial forces with a magnetic thrust bearing is discussed. The main benefits of this technology are higher efficiency and increased reliability.The work presented in this thesis was carried out within the Division of Electricity in the Department of Engineering Sciences at Uppsala University. It is based on original research supported by analytical calculations, computational simulations and extensive experimental work.
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| 2. |
- Gennebäck, Nina, 1982-
(författare)
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Cardiac hypertrophy : transcription patterns, hypertrophic progression and extracellular signalling
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The aim of this thesis was to study transcription patterns and extracellular signalling of the hypertrophic heart to better understand the mechanisms initiating, controlling and maintaining cardiac hypertrophy.Cardiac hypertrophy is a risk factor for cardiovascular morbidity and mortality. Hypertrophy of the myocardium is a state, independent of underlying disease, where the myocardium strives to compensate for an increased workload. This remodelling of the heart includes physiological changes induced by a changed gene expression, alteration of the extracellular matrix and diverse cell-to-cell signalling.Shedding microvesicles and exosomes are membrane released vesicles derived from the plasma membrane, which can mediate messages between cells and induce various cell-related processes in target cells.Methods and materials: Two different microarray studies on different materials were performed. In the first study, cardiac myectomies from 8 patients with hypertrophic obstructive cardiomyopathy (HOCM) and 5 controls without cardiac disease were used. In the second study, myocardial tissue from 6 aorta ligated and 6 sham operated (controls) rats at three different time points (1, 6 and 42 days post-surgically) were analysed. To reveal differences in gene expression the materials were analyzed with Illumina whole genome microarray and multivariate data analysis (PCA and OPLS-DA).Cultured cardiomyocytes (HL-1) were incubated with and without growth factors (TGF-β2 or PDGF BB). Microvesicles and exosomes were collected and isolated after differential centrifugations and ultracentrifugations of the cell culture medium. The microvesicles and exosomes were characterized with dynamic light scattering (DLS), flow cytometry, western blot, electron microscopy and Illumina whole genome microarray.Results: The two different microarray studies revealed differentially expressed gene transcripts and groups of transcripts. When comparing HOCM patients to controls significant down-regulation of the MYH6 gene transcript and two immediate early genes (IEGs, EGR1 and FOS), as well as significant up-regulation of the ACE2, JAK2 and HDAC5 gene transcripts were found. In the rat model, 5 gene groups showed interesting clustering after multivariate data analysis (OPLS-DA) associated with the hypertrophic development: “Atherosclerosis”, “ECM and adhesion molecules”, “Fatty acid metabolism”, “Glucose metabolism” and “Mitochondria”.The shedding microvesicles were rounded vesicles, 40-300 nm in size and surrounded by a bilayered membrane. Chromosomal DNA sequences were identified in the microvesicles. The microvesicles could be taken up by fibroblasts resulting in an altered gene expression in the fibroblasts. The exosomes from cultured cardiomyocytes (incubated with TGF-β2 or PDGF BB) had an average diameter of 50-80 nm, similar to the unstimulated control exosomes. A large, for all cardiomyocyte derived exosomes, common pool of mRNA seems stable and a smaller pool varied in mRNA content according to treatment of the cardiomyocyte. Of the common mRNA about 14% were ribosomal, 14% were of unknown locus and 5% connected to the function of the mitochondria.Conclusions: The microarray studies showed that transcriptional regulation at a stable stage of the hypertrophic development is a balance of pro and anti hypertrophic mechanisms and that diverse gene groups are differently regulated at different time points in the hypertrophic progression.OPLS-DA is a very useful and powerful tool when analyzing gene expression data, especially in finding clusters of gene groups not seen with traditional statistics.The extracellular vesicle studies suggests that microvesicles and exosomes released from cardiomyocytes contain DNA and can be involved in events in target cells by facilitating an array of processes including gene expression changes. Different treatment of the cardiomyocyte influence the content of the exosome produced, indicating that the signal function of the exosome might vary according to the state of the cardiomyocyte.
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| 3. |
- Persson, Urban, 1961-
(författare)
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District heating in future Europe : Modelling expansion potentials and mapping heat synergy regions
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a set of methodologies and approaches to investigate and determine the extent by which district heating can contribute to improved energy system efficiency and reduced carbon dioxide emissions in future Europe. The main motivation for suggesting large-scale implementation of district heating as a structural energy efficiency measure to obtain these objectives originates essentially in the predicament that a majority of European buildings today remain highly dependent on fossil fuels to provide energy needed for space heating and hot water preparation. In parallel, vast annual volumes of rejected excess heat from European power plants and industries are mainly neglected and lost unutilised to the ambient surroundings, why extended recovery and utilisation of such secondary energy assets realistically could replace significant shares of current inefficient supplies by fuel substitution. A prerequisite, however, for the viability of this logical prospect, is that infrastructures by which to facilitate excess heat recovery and subsequent network heat distribution are in place, which by no means is the average case in contemporary Europe.Hereby, the investigation is structured orderly by first establishing whether district heating can be a competitive alternative on current urban European heat markets, facilitated by a distribution capital cost model, where after the energy systemic benefits of expanding district heating are characterised and used to estimate a plausible expansion potential based on comparative analysis. Next, energy system modelling of continental EU27 by the year 2050, with district heating expanded in alignment with this potential, is performed to assess the total energy system cost benefits relative an alternative scenario focusing mainly on individual energy efficiency measures. Finally, spatial mapping to identify current primary target regions from which large-scale implementation of district heating could emanate is conceived and performed by use of a geographical information systems interface.The findings are generally supportive of a realisation of the objectives, mainly so by establishing a three-fold directly feasible expansion potential for district heating in city areas, but recognise also several additional, mainly non-technical, issues and challenges necessary to address in a successful transition to more energy efficient supply structures in future Europe.
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| 4. |
- Sakari, Thorbjörn B.
(författare)
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Adhesive small bowel obstruction: aspects on epidemiology, treatment, costs and prevention
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Small bowel obstruction (SBO) is a common and sometimes life-threatening clinical condition, usually caused by post-operative adhesions. The aims of this thesis were to investigate the outcome after SBO surgery (Paper I), cost of SBO surgery including follow-up (Paper II), incidence of SBO after colorectal cancer (CRC) surgery (Paper III), and to assess the safety of using the adhesion preventing substance icodextrin in CRC surgery (Paper IV).Paper I, a population-based retrospective study on all patients operated for adhesive SBO (n=402) in the Uppsala and Gävleborg counties between 2007 and 2012. The SBO mechanism was a fibrous band in 56%. Complications and reoperations were recorded in 48% and 10% of patients, respectively. Complications, ICU care and early mortality were associated with age and ASA class. Seventy two patients had a recurrence of SBO, 26 of whom were re-operated. Previous laparotomies, diffuse adhesions, and complicated surgery (bowel injury, longer operation times and bleeding) were predictors of recurrent SBO. Paper II used the same cohort as in Paper I with an extended follow-up (8 years in median). Mean total cost estimates per patients were €40,467 during the study period. Diffuse adhesions and complications were associated with increased costs for SBO in a multivariable analysis (p<0.001).Paper III is a population-based register study based on all CRC cancer patients in Sweden 2007–2017. Among 33,632 CRC patients operated for stage I–III disease, the 5-year cumulative incidence was 7.6% for SBO and 2.2% for SBO surgery. In 198,649 matched CRC-free comparators the corresponding incidences were 0.6% and 0.2%, respectively. Open surgery and radiotherapy were associated with an increased incidence of SBO and SBO surgery. Paper IV is an interim analysis regarding morbidity and mortality, of a randomized controlled multicenter study assessing whether the adhesion preventing substance icodextrin can reduce the risk of postoperative SBO in stage I–III CRC patients. Randomization, to standard treatment with or without icodextrin, was blinded to the authors. Demographic data and overall complications were similar in the groups. Mortality, ICU care, anastomotic leaks and reoperations did not differ.
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