Iskanje po katalogu digitalne knjižnice

Opis: Background: This study aimed to quantitatively evaluate the learning curve of laparoscopic liver resection (LLR) of a single surgeon. Patients and methods: A retrospective review of a prospectively maintained database of liver resections was conducted. 171 patients undergoing pure LLRs between April 2008 and April 2021 were analysed. The Halls difficulty score (HDS) for theoretical predictions of intraoperative complications (IOC) during LLR was applied. IOC was defined as blood loss over 775 mL, unintentional damage to the surrounding structures, and conversion to an open approach. Theoretical association between HDS and the predicted probability of IOC was utilised to objectify the shape of the learning curve. Results: The obtained learning curve has resulted from thirteen years of surgical effort of a single surgeon. It consists of an absolute and a relative part in the mathematical description of the additive function described by the logarithmic function (absolute complexity) and fifth-degree regression curve (relative complexity). The obtained learning curve determines the functional dependency of the learning outcome versus time and indicates several local extreme values (peaks and valleys) in the learning process until proficiency is achieved. Conclusions: This learning curve indicates an ongoing learning process for LLR. The proposed mathematical model can be applied for any surgical procedure with an existing difficulty score and a known theoretically predicted association between the difficulty score and given outcome (for example, IOC).
Ključne besede: difficulty score, learning curve, laparoscopy, hepatectomy, intraoperative complications, surgical procedures
Objavljeno v DKUM: 07.04.2025; Ogledov: 0; Prenosov: 2
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Opis: With this publication, we aim to inform doctoral students, university professors, and the interested public about current topics being researched by doctoral students in the field of the green transition and the role of the academic environment in developing sustainable solutions. The summaries of the publications provide insight into the research problems doctoral students are addressing in this area and the solutions they propose.
Ključne besede: green transition, sustainability, development, innovation, doctoral students
Objavljeno v DKUM: 22.11.2024; Ogledov: 0; Prenosov: 46
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Opis: We study the separability of the Dirac equation in the background of four dimensional charged rotating asymptotically flat black hole solution of supergravity and the low energy string theory known as STU black hole. In particular, we analyze in detail the separability conditions in the pairwise equal charge STU black hole space-time [M. Cvetič and D. Youm, Phys. Rev. D 54, 2612 (1996).]. While in the latter case the minimally coupled Dirac equation is not separable, the introduction of a specific torsion term ensures the separability. The source of the torsion is the Kalb-Ramond field, which is an integral part of string theory, but further aspects of its properties and coupling to fermionic fields remain to be studied. To derive the torsion, two different approaches are used in conformally related frames, showing that the torsion is not unique. The correspondingly modified Dirac equations in the Einstein and string frames are shown to be separable. Furthermore, the massless radial and angular wave equations are examined; they show close similarity with corresponding equations for the standard Kerr background. A generalization of the Teukolsky equation for the pairwise equal case is conjectured. We also briefly analyze a technically sophisticated radial equation in the massive case.
Ključne besede: quantum fields of spacetime, supergravity, curved spacetime, Dirac equation
Objavljeno v DKUM: 19.07.2024; Ogledov: 165; Prenosov: 10
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Opis: Motivated by recent studies of long-range forces between identical black holes, we extend these considerations by investigating the forces between two nonidentical black holes. We focus on classes of theories where charged black holes can have extremal limits that are not BPS. These theories, which live in arbitrary spacetime dimension, comprise gravity coupled to N 2-form field strengths and (N − 1) scalar fields. In the solutions we consider, each field strength carries an electric charge. The black hole solutions are governed by the SLðN þ 1; RÞ Toda equations. In four dimensions, the black hole solutions in the SLð3; RÞ example are equivalent to the “Kaluza-Klein dyons.” We find that any pair of such extremal black holes that are not identical (up to overall scaling) will repel one another. We also show that there can exist pairs of non-extremal, nonidentical black holes which obey a zero-force condition. Finally, we find indications of similar results in the higher examples, such as SLð4; RÞ.
Ključne besede: astronomy, astrophysics, black holes, spacetime dimensions
Objavljeno v DKUM: 06.06.2024; Ogledov: 115; Prenosov: 12
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Opis: Self-sovereign identity (SSI) is a user-centric, decentralised identity approach that provides a means for identification, authentication, and authorisation without the involvement of external entities, responsible for identity provisioning and management in current centralised and federated approaches. In general, the basic building blocks of an SSI system include decentralised identifiers, verifiable credentials, identity wallets, a verifiable data registry, and three main actors: issuer, identity holder, and verifier. Even though the SSI field is dominated by proposals, SSI systems can be implemented in different ways, which is reflected in the absence of a well-defined architecture. Thus, the best implementation is still a matter of research, the requirements of the individual system, and its field of application. However, well-designed and implemented systems are crucial to avoiding failures, speeding up the development process, ensuring high quality, and the broader adoption of SSI solutions. Hence, the main objective of this study was to identify design patterns and good practices of the SSI ecosystems by reviewing and analysing the literature, technical documentation, and existing SSI implementations. Therefore, the study is built on existing knowledge, and presents a comprehensive catalogue of thirty-five SSI design patterns that can serve as a starting point for a possible SSI system design.
Ključne besede: self-sovereign identity, decentralised identity, design patterns, decentralised identifiers, verifiable credentials, blockchain, verifiable data registry, identity wallets
Objavljeno v DKUM: 05.12.2023; Ogledov: 448; Prenosov: 79
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