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Recent Submissions
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(2024)The need caused by climate change and the pursuit to use natural resources more efficiently has accelerated the search for new alternatives to fossil fuels. This has increased the popularity of geothermal energy, of which the most common and versatile energy system is the Enhanced Geothermal System (EGS). An unavoidable byproduct of EGS power plants is seismicity, which occurs particularly during hydraulic stimulation to enhance the flow of heat transfer fluid in the bedrock. Stimulation significantly increases the seismic risk in the area to a level well above the natural state, thus increasing the probability of significant earthquakes. To minimize the risks and damages caused by significant seismic events, it is important to determine the maximum credible earthquake magnitude (Mmax) for EGS projects. Mmax serves as a crucial parameter in seismic risk assessment, defining the largest possible magnitude event that can be reached during the injections. This work investigates the ST1 Deep Heat project that operated in Otaniemi, Espoo, during which two stimulations were conducted in 2018 and 2020. The combined seismic risk from these stimulations has not yet been evaluated in terms of the Mmax and the probability distribution of magnitudes. In this study, we aim to determine the Mmax value for Otaniemi based on a probabilistic approach, using the method presented by Shapiro et al. (2010), where the Gutenberg-Richter relation is modified by incorporating the seismogenic index and the volume of injected fluid. This work suggests that the value of Mmax produced by the Otaniemi stimulations is M2.33. Therefore, the probabilities for significant earthquakes are low, indicating a low seismic risk. When previous studies are complemented with the effects of the 2020 stimulation, this study shows that the 2018 stimulation is the main contributor to the seismic risk in Otaniemi and that the increase in seismic risk from the 2018 stimulation to the end of the 2020 stimulation is small. The results of this work show that the seismogenic index can be used to estimate Mmax and probabilities of significant magnitudes from statistical injection-based data and provide structural geological justifications for these results. The results support the idea that injection-based Mmax is the result of the interaction between injection strategy and natural seismotectonic conditions. The lower seismicity of the 2020 stimulation can be explained by these factors. In EGS operations, the injection strategy is crucial for managing the seismic risk. The seismogenic index determined in this study describes the seismotectonic state of the Otaniemi reservoir. Once determined, it can be used in future studies or projects focusing on the Otaniemi reservoir and boreholes. It is also possible that another geologically similar reservoir would have a similar seismogenic index, which would allow the findings of this study to be applied to the assessment and management of similar risks elsewhere. Continued and high-quality research is a requirement for the development of policies and methods to make geothermal energy production safer in the future. This research provides information on the relationship between EGS operations and induced seismicity and will increase the understanding of induced seismicity and its hazards in general.
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(2024)Zero Trust -turvallisuusmalli uudistaa tietoverkkojen tietoturva-ajattelua lähtemällä oletukses- ta, ettei mikään tietoverkon vyöhyke ole itsessään turvallinen. Tällöin myös luotettujen verk- kojen sisäisiä tietoliikenneyhteyksiä on tarkasteltava kriittisesti, ja ne on sisällytettävä harkin- nanvaraisen ja minimioikeuksiin perustuvan pääsynhallinnan piiriin. Käsite mikrosegmentointi on ymmärrettävä suhteessa verkon segmentointiin eli sen jakamiseen vyöhykkeisiin. Mikrosegmentti on niin mikroskooppinen vyöhyke, että se on enää yhden isän- täkoneen kokoinen. Mikrosegmentoinnissa jokainen tietoliikenneyhteys, myös kahden saman lähiverkon isäntäkoneen välinen, ylittää vyöhykerajan ja on pääsynvalvonnan alainen. Tässä työssä tutkitaan, että jos virtuaalisesta tietokoneluokasta Zero Trust -mallin mukaisesti sallitaan vain tunnetut yhteydet käyttämällä tähän mikrosegmentoivaa palomuuria, niin kuinka paljon tämä vähentää lähiverkon liikennettä ja estetäänkö samalla jotain olennaista? Teoriaosuudessa esitellään tietoliikenteen perusteet, Defense in Depth ja Zero Trust -käsitteet, palomuurien toimintaperiaatteet, tietokoneiden virtualisointi sekä datakeskusverkkojen toteu- tustapoja. Empiirisessä osuudessa analysoidaan lähiverkon sisäistä liikennettä Helsingin yliopiston etä- työpöytäympäristöstä, jota voi ajatella virtuaalisena etäkäytettävänä tietokoneluokkana. Etä- työpöytäympäristöstä syntyviä lateraalisia yhteyksiä analysoidaan kvantitatiivisesti vertaillen liikennemääriä täsmä-, ryhmä- ja yleislähetysluokissa sekä kvalitatiivisesti tarkastelemalla oh- jelmistoja näiden yhteyksien taustalla. Samalla etsitään vastausta kysymyksiin: mikä tarkoitus näillä yhteyksillä on ja ovatko ne tarpeellisia virtuaalisessa tietokoneluokassa. Tarpeettomien yhteyksien suodattamista pohditaan myös energiansäästön näkökulmasta.
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(2024)There are two primary types of quantum computers: quantum annealers and circuit model computers. Quantum annealers are specifically designed to tackle particular problems, as opposed to circuit model computers, which can be viewed as universal quantum computers. Substantial efforts are underway to develop quantum-based algorithms for various classical computational problems. The objective of this thesis is to implement algorithms for solving graph problems using quantum annealer computers and analyse these implementations. The aim is to contribute to the ongoing development of algorithms tailored for this type of machine. Three distinct types of graph problems were selected: all pairs shortest path, graph isomorphism, and community detection. These problems were chosen to represent varying levels of computational complexity. The algorithms were tested using the D-Wave quantum annealer Advantage system 4.1, equipped with 5760 qubits. D-Wave provides a cloud platform called Leap and a Python library, Ocean tools, through which quantum algorithms can be designed and run using local simulators or real quantum computers in the cloud. Formulating graph problems to be solved on quantum annealers was relatively straightforward, as significant literature already contains implementations of these problems. However, running these algorithms on existing quantum annealer machines proved to be challenging. Even though quantum annealers currently boast thousands of qubits, algorithms performed satisfactorily only on small graphs. The bottleneck was not the number of qubits but rather the limitations imposed by topology and noise. D-Wave also provides hybrid solvers that utilise both the Quantum Processing Unit (QPU) and CPU to solve algorithms, which proved to be much more reliable than using a pure quantum solver.
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(2024)Saprotrophic wood-decaying fungi access nutritional carbon by degrading lignocellulosic biomass with ligninolytic and carbohydrate active enzymes. Research of species-species level interactions of the fungi is crucial to understand ecosystem functions and carbon cycling. Furthermore, research results of wood-decaying fungi and interspecific fungal interactions can be beneficial for development of biotechnological applications. In this study, two brown rot species Fomitopsis pinicola and Fomitopsis betulina, two white rot species Phlebia radiata and Fomes fomentarius and one soft rot species Schizophyllum commune were studied in combination cultures on birch wood substrate for 12 weeks. Interactions of the fungi were studied by analysing laccase, manganese peroxidase, xylanase, and iron reduction activities, and by analysing the expression of genes coding for lignocellulose-degrading enzymes. pH of the cultures was measured to estimate the metabolic activity of the fungal species. Suppression of xylanase and iron reduction activities demonstrated dominance of the white rot species over the other decay type species in the co-cultures. In addition to the depressed enzyme activities, increase in white rot production of laccase and manganese peroxidase activities indicated combative interactions in the co-cultures. This study evidenced species and growth-time dependent changes in signature enzyme activities and in gene expression of wood-decaying fungi during interspecific fungal interactions.
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(2024)Antimicrobial resistance (AMR) is a crucial problem in the clinical field worldwide. The need for novel antimicrobials to tackle AMR is imminent. Image-derived data can be used to understand the mechanism of action (MoA) of newly discovered compounds and classify them within known classes of antibiotics. This study aimed to develop a simple image-based measurement method for screening new antimicrobials and simultaneously defining the MoA. In the process, Escherichia coli ATCC 25292 was selected as a model strain from the Gram-negative bacterial group. This strain was treated with antibiotics belonging to different classes. Treated bacteria were imaged with Cytation 5 Cell Imaging Reader and analyzed using ImageJ2 software. The developed workflow was validated by testing the pipeline to be applied for some ESKAPE strains categorized as antibiotic-resistant bacteria. The results revealed that this pipeline enables us to observe the bacterial single-cell phenotypic changes in response to antimicrobials, such as the elongation caused by ampicillin and ciprofloxacin treatments, which are cell wall synthesis and DNA replication inhibitors, respectively. The treated bacterial cells were significantly longer than untreated cells from the sample without antibiotic. Thus, the image-based-high throughput assay can support the drug discovery by identifying the preliminary MoA of new antimicrobials against AMR bacteria. Promising data obtained on E. coli and some pathogenic bacteria allow for pursuing similar approach with other AMR Gram-negative bacterial species.