| 1. |
- Donoso, George A.
(författare)
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Seismic imaging of volcanogenic massive sulphide deposits : From legacy to innovative surveys
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The volcanogenic massive sulphide deposits at the Neves-Corvo mine area, part of the Iberian Pyrite Belt in southern Portugal, were studied using seismic methods. Three distinct reflection seismic datasets were used in this study: a 2D legacy data from 1996, an innovative 2019 surface and in-mine acquisition, and a 2011 3D seismic survey. The seismic data were processed with the main objective of improving the seismic signature of the volcanogenic massive sulphide deposits in the area by the use of modern and innovative seismic methods.The legacy dataset, acquired in 1996, was reprocess using today’s processing software. The Lombador massive sulphide was better imaged and a number of never-before-seen shallow but steeply dipping reflections were detected. In the 2019 seismic survey, 2D seismic profiles were acquired on the surface above the Lombador deposit, and four seismic profiles were deployed inside mine exploration tunnels at 650 m depth. Arguably, the first time a seismic acquisition survey of this size has been carried-out inside an active underground mine. The processing of the surface profiles was complemented by additional methods that indicate how the out-of-plane contribution of the Lombador deposit may not be detectable when employing 2D data only, showing the imaging potential of a small-scale survey implemented with innovative acquisition technologies. The 3D seismic data processing showed sensitivity to parameter selection for imaging. Processing results using pre-stack dip move-out and post-stack migration methods show moderate to steeply dipping reflections. Which can be correlated with known lithological contacts, some are interpreted to be originated from the Semblana and Lombador deposits. Despite the mixed signal-to-noise ratio the seismic volume reveals improved 3D seismic images of both shallow and deep structures, allowing to account for the deposit’s lateral extension beyond the capabilities of 2D seismic imaging alone. It was possible to distinguish strong diffraction patterns, interpreted as originating from faults and edges of the Lombador deposit, illustrating the usefulness of diffraction patterns for better interpretation of geological features in hard-rock environments. All of the aforesaid allows to conclude that an exploration programme solely based on 2D seismic data would have showed false-positive results in depth. This encourages the employment of 3D seismic methods, instead of 2D, in mineral exploration for accurate detection and targeting of VMS deposits.
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| 2. |
- Fortese, Fabricio, 1976-
(författare)
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Early Determination of Arbitral Jurisdiction : Balancing efficacy, efficiency, and legitimacy of arbitration
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation examines the timing of judicial determination of jurisdictional disputes in the presence of an arbitration agreement. The analysis focuses on Article 8(1) of the UNCITRAL Model Law on International Commercial Arbitration (and Article II(3) of the New York Convention on the Recognition and Enforcement of Foreign Arbitral Awards). It circumscribes the discussions to a nuanced interpretative strategy.It is uncontroversial that national courts have the authority to decide, conclusively, disputes on arbitral jurisdiction. It is common ground that arbitrators, too, have the authority to rule on their own jurisdiction, subject to judicial control. This is known as the principle of competence-competence, which is widely recognised in arbitration legislation, institutional rules, and practice. The critical research question that this dissertation deals with is whether national courts should (or could) conclusively determine arbitral jurisdiction before or after the arbitrators have preliminarily determined that controversy.This dissertation does not question who has the authority to settle jurisdictional disputes (conflict of jurisdictions). The assumption is that both, judges and arbitrators, enjoy such decision-making power. Instead, this research is about when (timing) a court should exercise that authority with conclusive effects.This work examines and answers the when question from an autonomous legal-interpretation perspective, detached from a given State's law, concepts, and rules. Its theoretical framework is specific to the Model Law and national arbitration laws that have adopted it without deviating from it – at least not from the wording of Article 8.
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| 3. |
- Mozafari, Elham, 1983-
(författare)
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Theoretical Description of the Electron-Lattice Interaction in Molecular and Magnetic Crystals
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electron-lattice interactions are often considered not to play a major role in material's properties as they are assumed to be small, the second-order effects. However, this study shows the importance of taking these effects into account in the simulations. My results demonstrate the impact of the electron-lattice interaction on the physics of the material and our understanding from it. One way to study these effects is to add them as perturbations to the unperturbed Hamiltonians in numerical simulations. The main objective of this thesis is to study electron-lattice interactions in molecular and magnetic crystals. It is devoted to developing numerical techniques considering model Hamiltonians and first-principles calculations to include the effect of lattice vibrations in the simulations of the above mentioned classes of materials.In particular, I study the effect of adding the non-local electron-phonon coupling on top of the Holstein Hamiltonian to study the polaron stability and polaron dynamics in molecular crystals. The numerical calculations are based on the semi-empirical Holstein-Peierls model in which both intra (Holstein) and inter (Peierls) molecular electron-phonon interactions are taken into account. I study the effect of different parameters including intra and intermolecular electron-phonon coupling strengths and their vibrational frequencies, the transfer integral and the electric field on polaron stability. I found that in an ordered two dimensional molecular lattice the polaron is stable for only a limited range of parameter sets with the polaron formation energies lying in the range between 50 to 100 meV. Using the stable polaron solutions, I applied an electric field to the system and I observed that the polaron is dynamically stable and mobile for only a limited set of parameters. Adding disorder to the system will result in even more restricted parameter set space for which the polaron is stable and moves adiabatically with a constant velocity. In order to study the effect of temperature on polaron dynamics, I include a random force in Newtonian equations of motion in a one dimensional molecular lattice. I found that there is a critical temperature above which the polaron destabilizes and becomes delocalized.Moreover, I study the role of lattice vibrations coupled to magnetic degrees of freedom in finite temperature paramagnetic state of magnetic materials. Calculating the properties of paramagnetic materials at elevated temperatures is a cumbersome task. In this thesis, I present a new method which allows us to couple lattice vibrations and magnetic disorder above the magnetic transition temperature and treat them on the same footing. The method is based on the combination of disordered local moments model and ab initio molecular dynamics (DLM-MD). I employ the method to study different physical properties of some model systems such as CrN and NiO in which the interaction between the magnetic and lattice degrees of freedom is very strong making them very good candidates for such a study.I calculate the formation energies and study the effect of nitrogen defects on the electronic structure of paramagnetic CrN at high temperatures. Using this method I also study the temperature dependent elastic properties of paramagnetic CrN. The results highlight the importance of taking into account the magnetic excitations and lattice vibrations in the studies of magnetic materials at finite temperatures. A combination of DLM-MD with another numerical technique namely temperature dependent effective potential (TDEP) method is used to study the vibrational free energy and phase stability of CrN. We found that the combination of magnetic and vibrational contributions to the free energy shifts down the phase boundary between the cubic paramagnetic and orthorhombic antiferromagnetic phases of CrN towards the experimental value.I used the stress-strain relation to study the temperature-dependent elastic properties of paramagnetic materials within DLM-MD with CrN as my model system. The results from a combinimation of DLM-MD with another newly developed method, symmetry imposed force constants (SIFC) in conjunction with TDEP is also presented as comparison to DLM-MD results.I also apply DLM-MD method to study the electronic structure of NiO in its paramagnetic state at finite temperatures. I found that lattice vibrations have a prominent impact on the electronic structure of paramagnetic NiO at high temperatures and should be included for the proper description of the density of states.In summary, I believe that the proposed techniques give reliable results and allow us to include the effects from electron-lattice interaction in simulations of materials.
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| 4. |
- Respuela, Patricia, 1977-
(författare)
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Gene Regulation and Epigenetic Mechanisms in the Parasite Trypanosoma cruzi
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Trypanosomes are unicellular protozoan parasites responsible for several human diseases that affect millions of people and cause thousands of casualties every year. They also represent a primitive eukaryotic model system harboring unique processes and basic regulatory mechanisms such as RNA-editing, polycistronic transcription and trans-splicing, first described in these organisms. Unlike most eukaryotes where levels of gene expression are controlled at initiation of transcription, trypanosomes use post-transcriptional events as the main regulators. This thesis explores the epigenetic mechanisms involved in gene expression control in trypanosomes, providing the first evidences for a functional “histone-code” as well as the existence and location of DNA methylation in Trypanosoma cruzi. Chromatin immunoprecipitation (ChIP) was used for the profiling of acetylated and methylated histones in T. cruzi, showing that the modified histones were exclusively localized at bidirectional transcription start sites. In addition, promoters from highly transcribed genes were found depleted of nucleosomes, while DNA regions expected to be silent were not enriched in the investigated modified histones. Furthermore, we showed that the histone patterns were developmentally regulated. The first in depth characterization of the DNA methylation patterns in T. cruzi was presented in this work. We detected m5C in regions of transcriptional initiation and termination, retrotransposons, pseudogenes and the kinetoplast minicircle. We also showed that the amount of methylation changes during development, with an increase in non-replicative forms. We also characterized the DNA-interacting properties of a T. cruzi polypyrimidine-tract binding protein (TcPTB), and its potential role as a transcription factor. TcPTB was found to interact with single-stranded DNA present in promoters bound by its mammalian homologue as well as to the region of transcriptional initiation in Leishmania major. We also demonstrated that T. cruzi polypyrimidine stretches were able to confer ssDNA conformations. Overall, these results provide new insights into the biology of ancient pathogenic parasites, which might be exploited for drug development.
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