Coming dissertations at Uppsala university
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Spinal Stenosis : Clinical and Radiological Studies
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-534193
Background: Lumbar spinal stenosis (LSS) causes back pain, leg pain and restricted walking ability. There is sometimes a coexisting degenerative spondylolisthesis (DS), where one vertebra has slipped anteriorly to the one below. LSS is the most common cause for spinal surgery, and the annual rate of surgery is increasing in Europe and the US. The original surgical method is decompression-alone, in which the surgeon resects just enough tissue to create space for the neural structures, while maintaining motion and stability between the vertebrae. Decompression with fusion is a more complex method in which a stabilising bone bridge is created at the decompressed level, usually supported by screws and rods.
Aims: The primary aim of the thesis was to determine whether decompression-alone is sufficient, or if decompression with fusion generates better outcomes. A secondary aim, explored in paper IV, was to explore if patients with new radiological stenosis also had worse clinical outcome at two-year follow-up.
Methods: All papers are based on the Swedish Spinal Stenosis Study, an RCT randomising 233 LSS patients with or without DS to decompression-alone or decompression with fusion. Clinical, radiological and health economical parameters were collected from baseline up to five years after surgery. In papers I-III, data were analysed according to randomisation. In paper IV, SSSS patients are analysed as a cohort, disregarding the original randomisation.
Results: In papers I-III the fusion group had longer operating time, more perioperative bleeding and higher direct cost per procedure than decompression-alone. Two-year clinical outcomes did not differ between the groups, whereas at five years three secondary clinical outcomes were better for decompression-alone. The rate of new radiological stenosis at two-year MRI was higher in the fusion group. Reoperation rates did not differ between the groups. In paper IV no correlation was found between clinical outcomes and new radiological stenosis at two year follow-up. The presence of preoperative DS did not affect any of the results.
Conclusion: In LSS surgery, decompression-alone should generally be the method of choice, with or without preoperative DS present. Findings of new radiological stenosis two years after spinal stenosis surgery may well be present also among asymptomatic individuals.
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Processing and interpretation of marine seismic reflection data from the Baltic Sea area and the Lesser Antilles
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-536812
This dissertation is a comprehensive summary of two case studies using Multichannel seismic (MCS) reflection data in characterizing the fossilized inversion tectonics at the Sorgenfrei–Tornquist Zone (STZ) and ongoing subduction at the Lesser Antilles.
In the first paper, new seismic profiles acquired within the Bornholm Gat in the SW Baltic Sea area are processed, which image Late Cretaceous- Paleogene inversion and exhumation of a previously poorly characterized narrow crustal zone in the southern end of the STZ. Upper Cretaceous deposition shows predominant contourites and gravity-driven sedimentation were largely controlled by inversion tectonics and influenced by the intensification of bottom currents. The results suggest more than one tectonic pulse during the Late Cretaceous-Cenozoic inversion, resulting from a far-field NE-SW compression transmitted from the Africa- Iberia-Europe convergence and the intraplate stress associated with the enhanced collisional coupling between the Alpine-Carpathian orogen and its foreland.
In the second paper, we present a structural and depositional interpretation of the STZ based on detailed stratigraphic mapping of marginal trough basins. The Hanö Bay and Bornholm Basin contain a sand-rich mounded drift proximal to the northeast of the STZ, and this unit is resolved with high seismic vertical resolution and represents a clear example of a siliciclastic-carbonate mixed depositional system. The comparison of sequence-stratigraphic indicators and the global sea-level curve allows for a refined reconstruction of the inversion history. A major inversion phase is interpreted to start around the Santonian-Campanian. Furthermore, we attribute a penecontemporaneous change in the depositional pattern, i.e., the erosional Campanian-Maastrichtian contourite moat system, to intensified bottom current activity related to significant global cooling, in conjunction with the paleoceanographic modification induced by the inversion tectonics.
The third paper deals with the structure and fluid migration in the Lesser Antilles subduction zone, where a subducting seamount ridge interacts with the upper plate. In this work, we present a reprocessed multichannel seismic (MCS) profile together with bathymetry, earthquake data and tomographic velocity structures in the central Lesser Antilles. Our results suggest that fluids are expelled upward from the band of subducted sediments at the southern flank of the Tiburon ridge, leading to an NW-SE elongated zone of hydrofractured and weakened crust above a serpentinized mantle corner, consistent with a prominent aseismic corridor. We suspect that the high interplate seismic activity offshore Martinique at ~30-65 km depths may correspond to deeply subducted indurated sediments that act as a strong asperity on the plate interface.
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Mining Nature’s Platinum : Discovery, Characterization, and Optimization of Hydrogenases for Green H2 Applications
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-536472
Establishing a sustainable hydrogen (H2) economy requires developing catalysts that are not reliant on rare and expensive metals like platinum. As summarized in Chapter 1, microorganisms utilize hydrogenases to harness molecular H2 for their metabolic processes. Remarkably, these ancient gas-processing enzymes rely on earth-abundant metals to reach activities on par with platinum. Investigating the biodiversity and understanding the mechanism of these enzymes offer a promising route to develop sustainable catalysts for H2-processing.
This thesis employed a multidisciplinary approach, including bioinformatics, biochemistry, synthetic chemistry, and biophysics, to investigate two hydrogenase superfamilies, namely [FeFe] and [NiFe] hydrogenases. Key methods are outlined in Chapter 2. The main aim was to provide insights into their evolution, diversity, structure, function, and potential for green H2 applications.
Chapter 3 challenges the prevailing view of [FeFe] hydrogenase domain distribution by revealing their presence and activity in diverse archaeal lineages, including DPANN, Asgard, and Thermoplasmata, which notably host [NiFe]-[FeFe] hybrids. The study provides a new minimal size requirement for functional hydrogenase and contests the notion of evolutionary independence between the two hydrogenase superfamilies.
Chapter 4 identifies a distinct proton transfer pathway in the putatively sensory Group D [FeFe] hydrogenases, diverging from the well-characterized pathway in the catalytic Group A enzymes. The study supports the critical role of proton transfer in controlling overall enzymatic function and provides insights for engineering catalysts that integrate both proton transfer and redox chemistry.
Chapter 5 demonstrates how rational engineering approaches informed by evolutionary insights can enhance both H2 production and O2 tolerance in a Group D [FeFe] hydrogenase, TamHydS. This work reveals the synergistic impact of protein scaffold modifications on catalytic performance and highlights the potential of integrating phylogenetic information and protein engineering for developing robust and efficient biocatalysts.
Chapter 6 elucidates the mechanism by which Huc, an isolated O2-tolerant [NiFe] hydrogenase, is able to efficiently oxidize trace atmospheric H2. This exceptional capability arises from the intrinsic properties of the enzyme, particularly its high affinity for H2 and elevated overpotential, rather than being dependent on the cellular context. The insights gained from this study provide valuable guidance for the design and engineering of (a)biotic catalysts capable of operating under ambient conditions.