2024-09-22
00:06 |
Role of submembrane spaces in the control of transmembrane ion flux and cellular inotropic state in a model of human ventricular cardiomyocyte
Pásek, Michal ; Bébarová, M. ; Christé, G.
We have recently developed a model of a human ventricular cardiomyocyte incorporating the t-tubular and surface submembrane spaces and restricted ion exchange between these spaces and cytosol. After incorporating the experimental finding that the majority of Na+-Ca2+ exchanger proteins are located at the t-tubular membrane of human ventricular cardiomyocytes, we explored the consequences of ion concentration changes in the submembrane spaces on the electrophysiological activity of these cells. Consistently with published experimental and modelling studies, our model predicts an increased Ca2+ extrusion during the action potential. However, our model also predicts a significant reduction of Ca2+ extrusion throughout the diastole, which can ultimately lead to an increase in cellular inotropy.
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2024-09-14
00:04 |
Applicable Adaptive Discounted Fully Probabilistic Design of Decision Strategy
Molnárová, Soňa
The work addresses the issue of decreased utility of future rewards, referred to as discounting, while utilizing fully probabilistic design (FPD) of decision strategies. FPD obtains the optimal strategy for decision tasks using only probability distributions, which is its main asset. The standard way of solving decision tasks is provided by Markov decision processes (MDP), which FPD covers as a special case. Methods of solving discounted MDPs have already been introduced. However, the use of FPD might be advantageous when solving tasks with an unknown system model. Due to its probabilistic nature, FPD is able to obtain a more precise estimation of this model. After previously introducing discounting and system model estimation to FPD, the current work examines the effect of discounting on decision processes and its possible advantages when dealing with an unknown system model.
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2024-09-06
20:55 |
Correlative probe electron microscopy analysis of plasma-treated gallium-doped zinc oxide nanorods
Rutherford, D. ; Remeš, Zdeněk ; Mičová, J. ; Ukraintsev, E. ; Rezek, B.
Correlative Probe Electron Microscopy (CPEM) was used to investigate the topographical and electronic emission properties of gallium-doped zinc oxide nanorods (ZnO:Ga) after low pressure hydrogen or oxygen plasma treatment. Simultaneous secondary electron (SE) and back-scattered electron (BSE) emission information from the same nanorods enabled true correlation with the topographical information obtained by atomic force microscopy (AFM). All nanorods were analyzed in-situ on the same substrate using the same experimental parameters which allowed for accurate comparison. ZnO:Ga nanorods displayed the largest SE emission intensity as well as the greatest BSE emission intensity. Hydrogen plasma treatment reduced both SE and BSE emission intensity, whereas oxygen plasma treatment only reduced SE emission. These effects may help elucidate various optical as well as biological interactions of ZnO:Ga nanorods.
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2024-08-17
00:01 |
Stucco decoration of the coffered dome in Boim Chapel, Lviv (Ukraine)
Svorová Pawełkowicz, Sylwia ; Myślicka, M. ; Witkowski, M.
The Boim Chapel in Lviv, erected at the beginning of the 17th c. (1609–1611) as a family mausoleum by Jerzy (Georg) Boim, a wealthy merchant originating from Hungary, since 1967 is part of the Lviv National Art Gallery. Although today it forms a visual dominant of the Cathedral Square, until the end of 18th c. it was surrounded by other funeral chapels as part of the city’s cemetery. It represents one of the most important examples of Mannerist, profusely decorated, architectural style on the historical territory of the Polish-Lithuanian Commonwealth (covering today’s territories of Poland, Lithuania, Byelorussia and western Ukraine). Its exterior and interior decoration has mostly been executed\nin local stone except the stuccoworks in the coffered dome. The hemisphere has been divided into three rows of coffers, where at the bottom portrait busts of the Boim family, in the middle of prophets and at the top of saints have been placed. The space between the coffers, painted most probably in 1925 in blue, has been decorated with gilded stucco stars. In 2019, an archival and material research was launched to plan future restoration works in the chapel. For the time being, only a few samples have been taken to study the technique of stuccoworks in the coffered dome. The results of this preliminary research gave us an insight into the original technique and subsequent renovation works. The architectural decoration, such as frames, have been moulded on site, while the portrait busts and stars have been mounted as precast elements. The archival research was helpful in interpreting the material research results.
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2024-08-10
00:00 |
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2024-08-10
00:00 |
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2024-08-10
00:00 |
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2024-08-10
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2024-07-27
00:02 |
QUANTUM-MECHANICAL STUDY OF INTERNAL STRUCTURAL TRANSFORMATIONS IN Pb-SUPERSATURATED Pb-Sn ALLOYS
Friák, Martin ; Čípek, Petr ; Pavlů, J. ; Roupcová, Pavla ; Miháliková, Ivana ; Msallamová, Š. ; Michalcová, A.
Motivated by a decades-long controversy related to the crystal structure of Pb-supersaturated solid solutions of Pb in Sn, we have performed a quantum-mechanical study of these materials. Focusing on both body-centred-tetragonal beta-Sn and simple-hexagonal gamma-Sn structures, we have computed properties of two alloys with the chemical composition Pb5Sn11, i.e. 31.25 at. % Pb, which is close to the composition of the experimentally found alloy (30 at. % Pb). The 16-atom computational supercells were designed as multiples of the elemental beta- and gamma-Sn unit cells, where the Pb atoms were distributed according to the special quasi-random structure (SQS) concept. Full structural relaxations of both beta- and gamma-phase-based alloys resulted in very significant re-arrangements into structures which do not exhibit any apparent structural features typical for the original alloys, and are, therefore, difficult to classify. The formation energies of the beta- and gamma-phase-originating equilibrium phases are 50 meV/atom and 53 meV/atom, respectively. Therefore, they are not stable with respect to the decomposition into the elemental lead and tin. Moreover, our calculations of elastic constants of both phases revealed that they are close to mechanical instability. Our results indicate that the studied Pb-supersaturated Pb-Sn solid solutions may be prone to structural instability, transformations into different phases and decomposition. Our findings may contribute into the identification of the reason why the subsequent experimental studies did not reproduce the initial published data.
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2024-07-27
00:02 |
QUANTUM-COMPUTING STUDY OF THE ELECTRONIC STRUCTURE OF CRYSTALS: THE CASE STUDY OF SI
Ďuriška, Michal ; Miháliková, Ivana ; Friák, Martin
Quantum computing is newly emerging information-processing technology which is foreseen to be exponentially faster than classical supercomputers. Current quantum processors are nevertheless very limited in their availability and performance and many important software tools for them do not exist yet. Therefore, various systems are studied by simulating the run of quantum computers. Building upon our previous experience with quantum computing of small molecular systems (see I. Mihalikova et al., Molecules 27 (2022) 597, and I. Mihalikova et al., Nanomaterials 2022, 12, 243), we have recently focused on computing electronic structure of periodic crystalline materials. Being inspired by the work of Cerasoli et al. (Phys. Chem. Chem. Phys., 2020, 22, 21816), we have used hybrid variational quantum eigensolver (VQE) algorithm, which combined classical and quantum information processing. Employing tight-binding type of crystal description, we present our results for crystalline diamond-structure silicon. In particular, we focus on the states along the lowest occupied band within the electronic structure of Si and compare the results with values obtained by classical means. While we demonstrate an excellence agreement between classical and quantum-computed results in most of our calculations, we further critically check the sensitivity of our results with respect to computational set-up in our quantum-computing study. A few results were obtained also using quantum processors provided by the IBM.
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