Opin vísindi

 

Nýlega bætt við

Verk
Spacetime from Operator Algebras
(2026-06-09) Mohan, Vyshnav; Thorlacius, Larus; Raunvísindadeild
Under suitable assumptions, geometric objects such as the spacetime metric and curvature tensor can be reconstructed from the algebra of operators of quantized matter fields in the limit of vanishing Newton's constant. In this framework, the full non-linear Einstein equations can be expressed in the language of operator algebras, extending Jacobson's derivation without invoking the area law for Bekenstein-Hawking entropy. These assumptions can then be used as a criterion for determining whether the semiclassical limit of a given quantum theory admits an emergent gravitational description. Going in the other direction, the discrete spectrum of a holographic theory at finite N can be modelled by adding non-perturbative corrections to semiclassical operator algebras. The type III von Neumann algebra that arises in the vanishing Newton's constant limit can be enlarged by adjoining its modular Hamiltonian. A random matrix theory completion of this enlarged algebra, followed by ensemble averaging, results in a type I von Neumann algebra whose minimal projectors approximate those of the underlying microstates. In the case of an eternal black hole, the dimension of the type I algebra equals the Bekenstein-Hawking entropy with universal logarithmic corrections. The complexity of probe operators in the boundary theory provides a diagnostic of the validity of the corresponding bulk semiclassical effective field theory.
Verk
A Novel Role of the MITF-A Isoform in Maintaining Genomic Stability
(University of Iceland, School of Health Sciences, Faculty of Medicine, 2026-03-04) Venkatesh, Thejus; Stefán Sigurðsson; Faculty of Medicine (UI); Læknadeild (HÍ); School of Health Sciences (UI); Heilbrigðisvísindasvið (HÍ)
The genome of all living cells is susceptible to various intra- and extracellular events that can compromise its stability. This genomic stability is crucial for the normal function of all cells, and failure to preserve genome integrity can lead to cancer and other diseases. In the event of DNA damage, cells activate the so-called DNA Damage Response to initiate DNA repair. Replication stress can also cause genomic instability. Replication stress interrupts the DNA replication process by stalling the active replication fork. If there is prolonged replication stress, it leads to genomic instability, which can result in DNA damage, chromosomal abnormalities, and mutations. MITF is a transcription factor best known for its roles in melanocyte biology and melanoma, but its function in genome maintenance remains incompletely understood. While most studies have focused on the MITF-M isoform, the roles of other isoforms remain largely unexplored. Interestingly, many non-melanocytic cells predominantly express the MITF-A isoform. Data presented in this project show that MITFA is expressed in most tissues, including cancer tissues, and may function as a genome maintenance protein. In this study, we use the osteosarcoma cell line U2OS to uncover the non-melanocyte-specific role of MITF. We found that MITF depletion leads to TP53 accumulation, P21 expression, increased 53BP1 nuclear bodies, and high fork speed, suggesting a protective role in S phase, thus maintaining genomic stability. Differentially expressed genes upon MITF-A isoform knockdown show downregulation of genes associated with DNA replication and DNA repair. Mass spectrometry reveals that MITF-A shows increased interaction with proteins involved in DNA replication and repair, including RPA and PARP1, compared to MITF-M. Notably, data from single-molecule C-trap optical tweezer experiments show that MITF-A, but not MITF-M, stably binds RPA-coated singlestranded DNA. Replication dynamics revealed that MITF-A depletion led to an increase in replication fork speed, which is associated with reduced PARylation. Collectively, this study highlights MITF-A’s role in DNA replication and in maintaining genomic stability.
Verk
In Situ LIBS Analysis of Oxidation, Vaporization, and Phase Transformations in Molten Aluminum Alloys
(University of Iceland, School of Engineering and Natural Sciences, Faculty of Physical Sciences, 2026-06-24) Radsson, Mani Thor; Snorri Þorgeir Ingvarsson; Faculty of Physical Sciences (UI); Raunvísindadeild (HÍ); School of Engineering and Natural Sciences (UI); Verkfræði- og náttúruvísindasvið (HÍ)
This thesis demonstrates how in‑situ Laser‑Induced Breakdown Spectroscopy (LIBS) can be used to probe thermodynamic and kinetic phenomena in molten aluminum alloys. The results show that LIBS not only provides rapid compositional analysis but also captures vapor–liquid equilibria, oxidation behavior, and phase‑transformation dynamics in molten metal. In Al–Mg alloys, the Mg LIBS signal was found to be influenced by vapor‑phase emission, causing an exponential increase in apparent Mg concentration with temperature. Arrhenius analysis showed that this trend follows the enthalpy of Mg vaporization, confirming that LIBS directly reflects Mg vapor–liquid equilibrium. Alloying additions revealed varying degrees of thermodynamic interactions: Si, Zn, and Sn in 1-3 wt% concentrations moderately affected Mg activity, while alloying with Be, Ca, and Sr significantly reduced the temperature-dependent Mg contribution at only 0.01 wt% additions, in agreement with other studies on the influence of these group-II elements on the oxidation of Mg-containing melts. For Li‑containing alloys, the LIBS analysis showed strong signal saturation due to rapid surface oxidation and the formation of Li‑rich surface films. Time‑dependent measurements demonstrated that the Li concentration decays exponentially in the melt, with decay time increasing linearly with Mg concentration, suggesting that Mg-containing oxides have a partial blocking effect on Li removal from the melt. In primary aluminum, Li additions were shown to enhance the loss of Mg, Ca, and Sr from the melt. In Al–Ti and Al–Zr alloys, LIBS was successfully used to map liquid–solid equilibria and track real‑time formation of Al₃Ti and Al₃Zr. Measured liquidus lines agreed with thermodynamic predictions, while experiments at different cooling rates revealed different degrees of nucleation undercooling for Al₃Ti and Al₃Zr phases. Silicon additions were shown to reduce undercooling in Al–Zr alloys and affect the morphology of Al₃Zr in the solidified alloy. Overall, the work shows that molten-metal LIBS analysis is a powerful tool for studying vaporization, oxidation, and intermetallic phase formation in molten alloys, offering unique opportunities for real-time analysis in metallurgical research and industrial process monitoring.
Verk
Scribes and Scribal Practice in Fifteenth-Century Iceland: A Study on the Evolution of Script and Language.
(University of Iceland, School of Humanities, Faculty of Icelandic and Comparative Cultural Studies, 2026-06-19) Pagani, Roberto Luigi; Haraldur Bernharðsson; Faculty of Icelandic and Comparative Cultural Studies (UI); Íslensku- og menningardeild (HÍ); School of Humanities (UI); Hugvísindasvið (HÍ)
This dissertation investigates Icelandic scribal and linguistic practices during the socalled “long” fifteenth century, roughly spanning from the late fourteenth century to the early sixteenth. The period has traditionally been regarded as one of stagnation in both language and script, yet such an assessment has rarely been tested through systematic analysis. The present study re-examines this assumption by tracing selected palaeographic and orthographic developments across a corpus of fifty scribal hands drawn from manuscripts dated between c. 1375 and c. 1525. Three palaeographic and seven linguistic features were selected on the basis of their frequency, diagnostic value, and chronological sensitivity. These include, among others, the distribution of forms of the letter “a”, of the tall “s” and of the “r” rotunda on the one hand, and on the other the fricativisation of unstressed wordfinal k, the diphthongisation of e before ng and that of é, the drop of intervocalic g before i/j, the u-epenthesis, and the orthographic representation of palatal consonants. Data were gathered through systematic random sampling of images of manuscript texts and converted into quantitative tables allowing comparison between conservative and innovative forms. The results demonstrate that the fifteenth century was not a static period but rather one characterised by gradual and uneven change. Certain features reveal clear chronological trajectories, while others display persistent coexistence of competing forms. When the individual profiles of scribal hands are compared, no coherent clusters emerge that could correspond to geographical or institutional affiliations, suggesting a highly individualised scribal practice which challenges the notion of “scribal schools” or “scribal milieu”. The combination of palaeographic and linguistic data thus provides a more nuanced picture of late-medieval Icelandic manuscript culture. Far from representing a period of decline, the “long” fifteenth century appears as a dynamic phase of transition, bridging the classical and early modern stages of Icelandic writing. Not least, the findings offer a basis for refining the dating of broadly-dated manuscripts and for reassessing the evolution of Icelandic orthography and script.
Verk
Extending the Limits of Monitorability
(2026) Xuereb, Jasmine; Achilleos, Antonios; Francalanza, Adrian; Department of Computer Science
One of the most fundamental and long-standing issues in computer science is making sure that a system behaves as intended. To address this challenge, systems may be verified dynamically using a lightweight monitoring technique called runtime verification. Even though runtime verification circumvents issues associated with traditional techniques, it is limited by the fact that observations are typically constrained to the current computation path of the system. This limitation is even more acute for correctness properties describing the system’s computational graph, known as branching-time properties. This thesis investigates whether runtime verification can be extended to meaningfully verify a wider range of branching-time properties. We depart from the classical setup where monitoring is limited to a single execution and investigate the enhanced observational capabilities when monitoring a system over multiple runs. To ensure generality in our results, we focus on branching-time properties expressed in the modal mu-calculus, a well-studied foundational logic used by state-of-the-art model checkers. As part of a comprehensive theory, the first part of this thesis focuses on deterministic systems and demonstrates that the proposed multi-run monitoring setup can systematically extend previously established monitorability limits for branching-time properties. The second part extends the multi-run framework and corresponding results to systems that may exhibit non-deterministic behaviour. To show that the proposed setup is implementable, the third part outlines the steps for a full automation, as well as proves bounds that capture the correspondence between the syntactic structure of a property and the number of system runs required to adequately verify it. We also validate our results by instantiating the proposed multi-run monitoring setup to verify actor-based concurrent systems, a widely used concurrency paradigm. Given that these systems are inherently non-deterministic, the fourth part presents a general study of a highly non-deterministic calculus, where we systematically explore how the defining characteristics of the actor model enable the recovery of a certain degree of determinism.

Flokkar í Opnum vísindum

Veldu flokk til að skoða.

Niðurstöður 1 - 9 af 9

Öll gögn í Opnum vísindum eru vernduð af ákvæðum höfundalaga og með öllum réttindum áskildum, nema annað sé tekið fram.