Four young scientists from Vilnius University (VU) became laureates of the Best Dissertations 2020 competition. On Wednesday the winners were awarded by the President of the Republic of Lithuania Gitanas Nausėda.
71 research papers were submitted to the competition organised by the Lithuanian Union of Young Scientists: 39 dissertations in the natural sciences, technology, medicine and health, and agriculture, and 32 dissertations in the humanities and social sciences.
10 best dissertation authors, including four VU PhD students, were recognised as winners of the competition.
The aim of this competition is to encourage PhD students to prepare high-level dissertations that will be recognised not only in Lithuania, but also worldwide, to foster inter-institutional and interdisciplinary cooperation and to increase the motivation of young scientists of Lithuania to carry out scientific activities of the highest quality and relevance to society.
Živilė Pabijutaitė from the Faculty of Philosophy was awarded for her dissertation "Classical and Contemporary Models of Non-Deterministic Temporal Logic: the Superiority of Semantic Compatibilism". Her dissertation supervisor is Associate Professor Jonas Dagys and her scientific advisor is Professor Marius Povilas Šaulauskas.
Ž. Pabijutaitė's dissertation is devoted to one of the varieties of contemporary logic, temporal logic, whose object is propositions expressing temporal content, and whose aim is to make it possible to write and evaluate such propositions in formal systems. Although this branch of logic is nowadays of great applied importance, and some of its most prominent researchers are representatives of computer science, in this dissertation the tools provided by the field were used to solve a philosophical problem.
The problem is the question, raised by Aristotle, of whether and how it is possible to reconcile the logical principle of equivocation, which presupposes that every proposition is true or false, and the intuition of the open future, which is the proposition that there is not just one future course of action at the moment of time that is determined by necessity. The dissertation seeks to make a new case for the superiority of the compatibilist strategy and to present new arguments in defence of the possibility of reconciling these two provisions.
Focus on treating diseases
Dr Kristina Šnipaitienė from the Life Sciences Centre (LSC) was awarded for her dissertation in the field of biology "RNA Studies of Body Fluids for the Diagnosis and Prognosis of Prostate Cancer". The scientific supervisor of her dissertation is Professor Sonata Jarmalaitė.
Although the treatment of localised prostate cancer (PC) is quite effective, and aggressive disease development is only common in a minority of patients, it is characterised by a poor prognosis and a shorter survival time, and there is a lack of reliable markers for assessing the response to treatment. RNA circulating in blood and urine is an informative target for testing and can serve as a low-invasive diagnostic and prognostic marker for PC.
This dissertation shows that a combination of urinary miRNAs is a sensitive molecular tool for the non-invasive diagnosis of PC and specifically predicts biochemical disease progression.
Castration-resistant prostate cancer (CRPC) is still incurable and, due to the heterogeneous nature of CRPC, around 30% of patients develop immediate primary resistance to drugs such as abiraterone acetate (AA). One reason for AA resistance could be androgen receptor gene transcript variants (AR-V), which do not have a ligand binding domain and are always active. The dissertation shows that higher levels of AR and AR-V transcripts detected in the blood of AA-treated CRPC patients predict shorter progression-free survival and overall survival.
Tomas Šneideris was awarded for his dissertation in biochemistry "Study of the Formation and Self-Replication Characteristics of Protein Amyloid Fibrils". Scientific supervisor – Dr Vytautas Smirnovas.
The onset and progression of more than 50 human diseases, including Alzheimer's disease, Parkinson's disease and type 2 diabetes, are associated with the inability of specific peptides and proteins to adopt or maintain a native conformation and the subsequent conversion of these monomeric peptides or proteins into insoluble fibrillar aggregates known as amyloids.
T. Šneideris' dissertation provides new mechanistic insights into the formation of different insulin fibril strains. Furthermore, it has been demonstrated that the environmental conditions under which the amyloid aggregation reaction is carried out and the effect of the molecule on it, as well as the criteria by which the effect is assessed, are among the main factors determining whether a molecule will be identified as a potential anti-amyloid drug.
This dissertation provides new mechanistic insights into the process of prion self-replication. For the first time, it has been shown that the conformational variability of prion protein fibrils during their self-replication reaction depends on the concentration of the aggregates, which initiate the reaction.
T. Šneideris' work demonstrates that atomic force microscopy with a microfluidic dispensing platform offers a unique opportunity to visualise all forms of aggregating proteins that exist during amyloid aggregation.
Halide perovskites analysed
Sergejus Balčiūnas was awarded for his dissertation in physics "Broadband Dielectric Spectrometry of Some Perovskite Structures". Scientific supervisor – Dr Maksim Ivanov.
S. Balčiūnas' dissertation presents ABX3 materials of perovskite structure, which were tested over a wide range of frequencies from 10-3 to 1011. It was researched how a thin layer of potassium niobate (KNbO3) on crystallites of inorganic barium titanate (BaTiO3) affect the dielectric properties of BaTiO3.
The spontaneous polarisation value was observed to increase in such a shell-core structure. One possible cause is tensions on the surface of the BaTiO3 crystallites due to the mismatch of the crystal lattice with the KNbO3 lattice.
The dissertation focuses on a very popular material, halide perovskites ((CH3NH3PbX3(X = I, Br, Cl)). The author shows that these materials are not ferroelectric, so they cannot contain domains, and that the high efficiency is due to the relatively high value of dielectric permittivity, which effectively shields defects.
In the work on halide perovskites, it has been observed that replacing the A position cation, CH3NH3, with (CH3)2NH3 increases the stability of these materials. Also, the influence of the (CH3)2NH3 cation on the dielectric properties of the material is examined. Experimental results show that it is low, up to 4%. The concentration of (CH3)2NH3 cations in (CH3NH3)1-x((CH3)2NH3)xPbBr3 crystals is responsible for the expansion of low-temperature (148 K) phase transformation from a tetragonal to an orthorhombic state and for the drift to lower temperatures.
Photos by Robertas Dačkus / Office of the President of the Republic of Lithuania.