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Coming dissertations at Uppsala university

  • Evolution of a silicic magma reservoir in the upper crust : Reyðarártindur pluton, Southeast Iceland Author: Emma Rhodes Link: Publication date: 2022-05-19 10:02

    Field observations of extinct and exposed magma reservoirs shed light on processes operating in the roots of presently active volcanoes. The Reyðarártindur pluton, Southeast Iceland is an example of a fossil shallow magma reservoir that fed eruptions. The different chapters in this thesis examine the accumulation of magma, and processes occurring during the development and evolution of the magma reservoir from different methodological perspectives. A final model for the evolution of the Reyðarártindur pluton is then presented.

    The majority of the pluton consists of one voluminous rock unit, the Main Granite, that formed by rapid magma emplacement. However, a local zone of geochemically distinct, but related further Granite Enclaves and Quartz Monzonite Enclaves attest to variations in the composition of the underlying source reservoir. Space for the ca. 2.5 km3 of magma in the pluton was made by piecemeal floor subsidence, which began with multiple dykes that then propagated laterally to form flat-roofed intrusions at different depths. During the first stages of magma emplacement, shattering, sintering and sanidinite-facies contact metamorphism affected a ca. 10 m thick zone of the basalt host rock at the magma reservoir roof. The resulting hornfels was stronger than the original altered basalt, and contained zero porosity and permeability. It thus formed a ‘cap-rock’ to the magma reservoir, limiting heat, volatile and fluid transfer until fractured and faulted at a later stage. 

    The magma reservoir erupted at least once, causing local subsidence of the roof, which would have been observable at the Earth’s surface. Recharge of the magma reservoir by the same Quartz Monzonite and further Granite as exposed in the Reyðará River led to overpressure and eruption. We envisage that cooling and sealing of the piecemeal subsidence network preceded eruption, causing overpressure with magma recharge. The eruptive lifetime of the magma reservoir was limited to ca. 1000 years. This timeframe is much less than the duration of silicic magmatism in a typical Icelandic central volcano, or at other rhyolite-erupting volcanoes worldwide, which is in the order of hundreds of thousands to millions of years. Hence, the Reyðarártindur pluton likely represents a small, ephemeral part of a wider magmatic plumbing system that feeds a central volcano.

    The results from these studies can provide volcano-monitoring personnel with scenarios for magma emplacement, and processes leading to eruption, which they can then use as a framework for interpreting detectable signals of magma movement and volcanic unrest.

  • Markåtkomstersättning Author: Marc Landeman Link: Publication date: 2022-05-19 09:50

    How to compensate landowners when they suffer a compulsory acquisition of their property is a long-standing problem. In general, the subject is usually stated as a two-sided problem. First, it is a fairness problem regarding what measuring instrument should be used to decide a fair amount of compensation to the landowner. Second, it concerns how the chosen measuring instrument should be applied in practice from a legal point of view. 

    The main purpose of the thesis is to reconstruct the compensation system. Broad questions addressed include how the market value should be determined, what efficiency and fairness requirements the compensation has in this context, and how the conditions of different situations affect the view of what is an efficient and fair compensation. The thesis uses a mixed-method that contains a legal dogmatic method, as well as a law and economics, and a fairness approach. 

    The thesis finds that the market value can, in an economic context, only be determined as a range of probable prices and the result is largely influenced by the appraiser. To determine the market value of real property one needs to use qualitative approaches, even though the result is a quantitative measure. From a legal point of view, the court has to decide the specific price within the range that corresponds to the legal market value. To approach this problem, the court needs to use the underlying purposes of the compensation, such as full compensation and the general sense of justice. From a fairness perspective, both the legislator and the courts have modified the compensation rules in order to fulfil other goals that go beyond the economic market value. One key finding is that the market value in a legal context has a much higher degree of flexibility than in an economic context. Another key finding is that the design of the rules matters for the overall utility of society since an unfair system will generate demoralization costs. Therefore, the thesis argues that an adequate design of the compensation system has to take in to account the differences between different situations, since these differences decide what can be considered an adequate compensation. Overall, the thesis concludes that the current system should differentiate how the compensation has to be determined between different situations to a much larger extent. Thus, the extent to which a specific level of compensation achieves legal and societal goals depends on the situation. 

  • CD93 in regulation of vascular function and tumour progression Author: Kalyani Vemuri Link: Publication date: 2022-05-19 08:50

    To achieve successful vascular targeting in cancer, a better understanding of the molecular mechanisms that lead to tumour vascular abnormalities is required.  The transmembrane protein CD93 is highly expressed in the vasculature of several tumours including glioblastoma and has emerged as a potential anti-angiogenic target. This thesis work explores the mechanisms through which CD93 contributes to vascular function and facilitates tumour progression. In paper I, we identify that CD93 interacts with the extracellular matrix (ECM) glycoprotein multimerin-2, which stabilizes CD93 at the cell surface and anchors it to the ECM protein fibronectin. CD93 binds to integrinα5β1 and regulates the activity of integrinβ1 and fibronectin fibrillogenesis in vitro. Consistent with this, the tumor vessels of CD93-/- mice bearing gliomas displayed an impaired integrinβ1 activity and fibronectin fibrillogenesis, suggesting that CD93-multimerin-2-fibronectin axis has an important role in tumour angiogenesis. In paper II, we explored the co-regulation of CD93 with other genes associated with glioblastoma vascular abnormalities. Using the publicly available Gliovis database for distinguished gene correlation analysis, we identified multimerin-2, fibronectin and angiopoietin-2 as candidate genes which are likely to be expressed with CD93 in glioblastoma vasculature. The expression of CD93, fibronectin and angiopoietin-2 was associated with high microvascular proliferation. Moreover, the presence of CD93 in a high proportion of the tumor vessels correlated with poor survival, suggesting that targeting CD93 can be beneficial for glioblastoma patients. In paper III, we explored the role of CD93 in the blood brain barrier (BBB) integrity. We demonstrate that CD93 regulates the activity of Rho-GTPases, thus stabilizing the endothelial junction molecules VE-cadherin and claudin-5 and preventing the internalization of VE-cadherin. Consistent with this, CD93-/- mice displayed a compromised BBB and exhibited an increased vascular permeability. In paper IV, we further explored the consequences of endothelial barrier disruption upon CD93-deficiency in cancer. We demonstrate that CD93 binds to VEGFR2 and that the absence of CD93 enhances VEGF-induced VEGFR2 phosphorylation in vitro. Consistent with this, melanoma-bearing CD93-/- mice displayed impaired vascular integrity and an enhanced MMP9 expression, leading to increased intravasation of tumour cells and increased metastatic spread. This phenotype was reversed to the wild-type level by inhibiting the VEGF-VEGFR2 signalling in CD93-/- mice. Taken together, this thesis work reveals a key role of CD93 in regulating vascular maturation and stabilization in health and cancer, and unveils its contribution to tumour progression and metastasis.