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- Ikegami Andersson, Walter, 1990-
(författare)
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Exploring the Merits and Challenges of Hyperon Physics : with PANDA at FAIR
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Binary hyperon production in antiproton-proton annihilations will be carried out with the PANDA experiment at FAIR, and probes the strong interaction in the non-perturbative regime where the relevant degrees of freedom are unclear. The self-analyzing decays of hyperons provide a straightforward way to study reaction dynamics via the measurement of spin observables. However, since weakly decaying hyperons can travel several centimeters before decaying, they are challenging to reconstruct. Conventional track reconstruction algorithms assume that charge particles originate in the experiment interaction point.In this thesis, software tools are developed for the reconstruction and fitting of charged particles in the collaboration-wide software package PandaRoot. Pattern recognition algorithms are developed for the reconstruction of charged particle tracks with displaced vertices. Three algorithms that reconstruct the longitudinal momentum in the Straw Tube Tracker (STT) of PANDA are developed. They are based on a combinatorial approach, a Hough Transform, and a recursive annealing fit. The implementation and performance of these algorithms are presented. The track fitting scheme of PandaRoot is overhauled to treat the five particle species that PANDA is expected to measure, namely electrons, muons, pions, kaons and protons. The new track fitting scheme is outlined and discussed.When the PANDA experiment is taken into operation, beam time will be allocated to many different measurements. For this reason, feasibility studies are performed in this thesis. The pp → ΛΛ reaction is simulated at 1.642 GeV/c and the pp → Ξ+Ξ− reaction is simulated at 7.0 and 4.6 GeV/c beam momenta. The simulation and analysis chain of the studies are explained. Expected reconstruction rates are presented. Furthermore, the feasibility of reconstructing spin observables in the reactions is discussed.
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| 2. |
- Norlin, Anna-Karin, 1977-
(författare)
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Exploring the Biopsychosocial Model in Irritable Bowel Syndrome : with emphasis on stress, comorbidities and fatigue
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundIrritable bowel syndrome (IBS) is a common, chronic, relapsing, and sometimes disabling, symptombased disorder of gut brain interactions. It has got a female predominance and occurs in all ages, with a slight decrease among elderly. The IBS symptoms can affect everyday work and social life in addition to an increased use of health care resources. Most IBS patients are diagnosed and helped in primary health care (PHC). For many patients, available treatment is insufficient. It is known that both extraintestinal symptoms such as fatigue, as well as comorbidities such as mood disorders, chronic pain syndromes, and insomnia contribute to the illness burden, often to a larger extent than the gastrointestinal symptoms as such.Even though the pathophysiology of IBS is not completely known, it is now conceptualized as a disorder of altered brain-gut interactions, where a biopsychosocial model helps in understanding the symptoms. Exposure to stress is thought to play an important role overall in the pathology of IBS, as well as immune activation at least in a subgroup of patients.This thesis aimed to gain deeper understanding of the biopsychosocial mechanisms of IBS and its associations with stress, comorbidities, and fatigue.Methods Study I and II are based on the Twin cities IBS study population, which included IBS patients and a control group of other patients without gastrointestinal complaints from ten PHC centres in the county of Östergötland. Alongside demographics, psychosocial questionnaires and a GI symptom diary, it included analyses of hair cortisol concentrations (HCC) evaluated in study I, and data on self-rated health as well as diagnoses of comorbidities, and number of health care contacts from a regional registry, evaluated for study II.Study III of this thesis is based on the Brain-Gut study with a population of secondary care IBS patients, and healthy controls (HC). It included self-rated measures of fatigue impact on the daily life and early adverse life events, as well as measures of circulating TNF-α, and analyses of resting-state functional magnetic resonance imaging of brain areas within a mesocorticolimbic circuitry of known relevance for fatigue.Results Study I: Perceived stress was higher in the IBS group while a considerable portion of IBS patients had low levels of HCC. No association between perceived stress and HCC was seen in either group.Study II: IBS patients had lower self-rated health and more PHC utilization than the non-IBS patients. Good self-rated health was independently associated with younger age, higher sense of coherence and less gastrointestinal pain in both groups. In IBS, PHC utilization was associated with comorbidities in general, and sleep disorders in particular.Study III: Fatigue impact on daily life, and TNF- α were higher in IBS patients than in HC. In IBS, further an association was seen between fatigue impact on the one hand, and TNF- α, emotional abuse in childhood, as well as altered mesocorticolimbic connectivity on the other.Conclusion In conclusion this thesis firstly emphasizes that IBS patients in many ways, including health outcomes, consists a vulnerable group of PHC patients. We add evidence for a possible suppression of the stress response system in a substantial portion of IBS patients.Further, comorbid sleep disorders seem to be particularly associated with excess PHC utilization in IBS and could possibly be a target for treatment interventions. Moreover, alongside treating gastrointestinal pain, efforts to improve the individuals’ sense of coherence could be one way to achieve better self-rated health in both IBS and non-IBS patients.Finally, we suggest that fatigue in IBS is associated with immune activation, central alterations and to some extend also previous childhood trauma.
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| 3. |
- Walter, Marie V., 1985-
(författare)
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Novel Porous Films from Functional and Biocompatible Linear-Dendritic Hybrids
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the last decades, the fabrication of ordered nano- and microporous structures has attracted increasing interest due to their specific properties and multiple possible applications in electronics, as templates or in the biological field. The development of such materials has been favored by the introduction of the simple breath-figure templating method in the 1990’s. In order to fully exploit the potential of these porous materials, the use of advanced functional molecules as precursors is essential. One suitable class of molecules is the well-defined linear-dendritic hybrids (LD hybrids) family. The structural variations, multiple end-groups and possible amphiphilicity of these molecules are significant advantages that could lead to highly sophisticated functional materials with potential usage in biology. Therefore, this project was directed towards the synthesis of advanced LD hybrids and the evaluation of their ability to form ordered functional porous films.A degradation and toxicity study was initially conducted on polyester-based 2,2-bis(methylol)propionic acid (bis-MPA) dendrimers under physiological conditions to support the potential usage of these molecules for biological purposes. The materials were found to undergo a relatively fast depolymerization process at pH 7.5. Moreover, the initial dendrimer and its decomposition products were proven to be non-toxic for immune competent cells, allowing for the utilization of these molecules for biological applications.A linear-dendritic-linear hybrid library was successfully synthesized from biocompatible poly(ethylene glycol) (PEG), poly(ε-caprolactone) (PCL) and bis-MPA building blocks using a combination of ring-opening polymerization (ROP)and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The materials, consisting of one long PEG block connected to the focal point of the dendron and several PCL arms attached at its periphery, were used to construct ordered porous films using the breath figure method. The polymeric architecture strongly affected the ordering of the films with a more regular morphology obtained from a more flexible polymer. Changing the semi-crystalline PCL to amorphous polylactide (PLA) also permitted the formation of porous arrays. Interestingly, films obtained from inverted structures possessing one long PCL block and several short PEG chains, also presented a regular morphology. Moreover they could be activated to exhibit multiple surface hydroxyl groups.To increase the number of orthogonal synthetic methodologies available for the preparation of advanced macromolecules, high molecular weight dendritic macrothiols were synthesized. These molecules were efficiently coupled to a number of core molecules via thiol-ene coupling, generating a comprehensive library of dendritic materials. This approach represents an attractive alternative to the commonly used, but potentially toxic, CuAAC.Exploiting the obtained results, a final LD hybrid was synthesized from atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) derivatives and thiol-ene coupling (TEC) with macrothiols. This macromolecule was successfully utilized to form functional ordered porous arrays and the availability of peripheral alkyne functional groups was demonstrated by efficient coupling with fluorescent Rhodamine-B. The HEMA-backbone allowed for the introduction of cross-linkable azide groups that were used to significantly improve the thermal stability of the films from 50 °C to 200 °C. These materials have the potential to be used in applications such as catalysis, in medicine and as sensors.
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| 4. |
- Wang, Hongdi, 1991-
(författare)
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Thermo-mechanical Assessment of Reactor Pressure Vessels of Light Water Reactors During Severe Accidents
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The reactor pressure vessel (RPV) is one of the crucial safety barriers designed to isolate the reactor core, safeguarding against potential radioactive releases into the environment during a severe accident. The assessment of RPV behaviour and its failure is necessary to predict the characteristics of melt release into the reactor pit and succeeding ex-vessel accident progression.This thesis aims to develop both the model and methodology in the Finite Element Analysis (FEA) of the RPV to predict its structural behaviour during postulated severe accidents. The improvement in the FE model starts from the material models for the material properties of the RPVs. Since the SA533B1 and 16MND5 carbon steels are considered the structural materials of the RPVs relevant to a Nordic Boiling Water Reactor (BWR) and a Pressurized Water Reactor (PWR), respectively, the material models for these two materials are established and subsequently validated against multiple tests. The simulations strictly adhere to the test conditions in the validation process. The observed agreement between the simulation and test results serves as a good foundation for subsequent analysis on the RPV applications.A thermo-mechanical coupling approach is developed by coupling the ANSYS Mechanical APDL for the structural analysis of RPVs and MELCOR for defining boundary conditions. This approach can efficiently predict the RPV behaviour during accident scenarios, including deformation, stress and strain. Subsequently, the obtained results are subjected to a comprehensive failure analysis of RPVs with three failure criteria, namely melt-through, stress-based, and strain-based failure criteria. In addition, an advanced model in LS-DYNA is introduced to simulate the possible rupture phenomenon of RPVs during failure. The developed model and methodology are applied in structural analysis of the Nordic BWR and the PWR during severe accidents. The analysis results contribute to:(i) A benchmark specification in the EU-IVMR project WP2.4 conducted to investigate the effect of the ablated profile on RPV failure in numerical analysis; (ii) The feasibility of In-Vessel Retention (IVR) strategy mitigation analyzed for the RPV of a Nordic BWR in two severe accidents: a Station Blackout (SBO) and an SBO combined with a Loss-of-coolant Accident (SBO+LOCA); and (iii) A comprehensive failure analysis for RPVs in a Nordic BWR carried out under the mentioned two severe accidents. The RPV lower plenum model is extended from the two-dimensional case for a standalone vessel wall to a three-dimensional case for a vessel wall with a cluster of IGT structures. This failure analysis aims to investigate the failure mechanism and timing for both vessel wall and IGTs, providing valuable insights into the possible earliest failure mode of RPV lower plenum for different reactor designs and severe accident scenarios.
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