2026-06-14
01:45 |
Tři desetiletí pohybu geocentra z GNSS, SLR, LEO a geofyzikálních fluidních modelů
Zajdel, Radosław ; Balidakis, Kyriakos ; Nowak, Adrian ; Kur, Tomasz ; Sośnica, Krzysztof ; Douša, Jan
Pohyb geocentra odráží rozsáhlou redistribuci hmoty v zemském systému a lze jej odvozovat z družicových geodetických technik. V této studii hodnotíme časové řady geocentra od deseti analyzačních center IGS pokrývající období 1994–2025 (IGS Repro3 a následné aktualizace) společně s kombinovaným GNSS řešením na základě odhadu komponent rozptylu od Zajdela et al. (2025). Tyto série porovnáváme s nezávislými odhady ze SLR observací k družicím LAGEOS-1/2, z precizního určování drah družic LEO a z geofyzikálních modelů zatížení (GGFC a ESM). Spektrální dekompozice ukazuje, že roční a pololetní signály představují pouze ~20–35 % rozptylu GNSS, zatímco zbývající části dominují vysokofrekvenční a drakonitické artefakty. Porovnání napříč technikami ukazuje, že roční signál zachycený GNSS má převážně geofyzikální původ, s korelacemi ≈0,8 a s rozdíly mezi použitými technickami přibližně 2–3 mm v amplitudě a 20–30° ve fázi. Vnitřní konzistence GNSS je v Repro3 oproti Repro2 výrazně zlepšena, ačkoliv rozdíly vůči SLR, LEO a modelům zatížení přetrvávají, zejména v komponentě Z.
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2026-06-13
00:01 |
Unveiling the consequences of complete substitution of Sn atoms for Ni atoms in LaNi5: A DFT perspective
Huňařová, Anna ; Berecová, Valentína ; Zobač, Ondřej ; Friák, Martin ; Watson, A. ; Holec, D. ; Pavlů, Jana
The intermetallic compound LaNi<inf>5</inf> is a promising material for hydrogen storage. The ternary phase diagram La-Ni-Sn contains phases in which Ni atoms are substituted by Sn atoms, resulting in several different Sn/Ni ratios. In order to describe the La(Ni,Sn)5 system by phenomenological CALPHAD modelling, the energy of the completely substituted LaSn<inf>5</inf> is needed. As this compound does not exist under ambient conditions, it is difficult to examine experimentally. Therefore, its properties were computed by quantum-mechanical calculations. Density functional theory (DFT) was employed to determine the structural characteristics of LaSn5, along with its electronic structure, energetics and thermodynamic stability as well as its mechanical stability. Our DFT calculations revealed a dramatic volume expansion upon this extreme case of substitution of all Ni atoms by Sn atoms, but the hexagonal structure remains stable without any significant distortions. The electronic calculations also revealed that the electronic density of states has a minimum at the Fermi level, which is in line with the lattice stability.
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2026-06-13
00:01 |
Exploring spin disorder in ferrimagnetic iron oxides using standard DFT and advanced computational methods\n
Berecová, Valentína ; Friák, Martin ; Pizúrová, Naděžda ; Pavlů, J.
Spin disorder in ferrimagnetic iron oxides critically influences their electronic and magnetic properties, \nparticularly at the nanoscale. In this work, γ-Fe₂O₃ was investigated using several density-functional \napproaches (PBE, PBE+U, PBE+D4, SCAN, SCAN-L, SCAN+rVV10, r²SCAN and HSE06) to identify methods \ncapable of accurately reproducing its structural, magnetic, and electronic characteristics. The PBE functional \nprovided the best structural agreement with experiment, while PBE+U and HSE06 most accurately described \nmagnetic moments of –4.03/–4.06 μB (Fetetra) and 4.16/4.14 μB (Feocta). HSE06 yielded a band gap of 2.31 eV, \nin good agreement with the experimental value. Spin flip energetics revealed that spin realignment at \ntetrahedral sites is roughly twice (or more) energetically demanding than at octahedral sites; for example, \nunder PBE+U, the energy cost is 667 meV for Fetetra and 364–414 meV for Feocta. Density of states showed \nthat increasing spin disorder induces Fe 3d- and O 2p-derived in-gap states and can reduce the band gap up \nto 1.38 eV. To reduce computational cost, the CHGNet machine-learned potential was tested. While it fails to \nreproduce magnetic orientations, it substantially accelerates structural optimization. Overall, the results clarify \nthe link between spin disorder and electronic structure in iron oxides and demonstrate how DFT and machine\nlearning methods can be combined to efficiently model complex magnetic behavior for future research.
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2026-06-13
00:01 |
Electricity Cost and Spectral Effects of LED Lighting in Limnospira maxima Cultivation
Vásquez, Claudia
Illumination is a major operational cost in photobioreactor systems with artificial illumination for microalgae cultivation. Light-emitting diodes (LEDs) offer high photosynthetically active radiation (PAR) efficiency and various spectral output1, however, the relationship between spectral quality, biomass productivity, pigment synthesis, and electricity consumption remains insufficiently quantified for Limnospira maxima.2 This study evaluated the effects of six LED sources — polychromatic daylight white (DW), and warm white (WW), and monochromatic red (R), green (G), yellow (Y), and blue (B) — on biomass and pigment production under controlled cultivation conditions.
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2026-06-13
00:01 |
Extended Evaluation of LARCODEMS Separation Efficiency for Plastic Recycling: From Medium Density to Viscosity Effects
Šperlich, Antonín
This contribution represents a direct continuation and extended study of prior experimental work. While earlier phases focused on establishing the baseline separation efficiency as a function of medium density, the logical next step is to evaluate medium viscosity. The primary objective of this study was to assess the specific impact of viscosity on separation performance. Ultimately, the integration of both density and viscosity data serves as the foundation for developing a robust correlation to predict overall separation efficiency based on these combined transport phenomena.
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2026-06-13
00:01 |
Synthesis and Evaluation of Fluorinated Lactose-Based Glycopolymers as High-Affinity Galectin-3 Inhibitors
Krčil, Aleš
The development of carbohydrate-based galectin-3 (Gal-3) inhibitors is often limited by the lack of potent and selective molecular recognition.1 In this work, we explored selective fluorination of a lactose scaffold as a strategy to create hydrophilic glycomimetics with tunable binding properties. A series of β-lactosyl azides (1–4), selectively deoxyfluorinated at the 2′-, 3′-, 4′-, or 6′-position of the galactose unit, was synthesized via chemical glycosylation of a glucosyl azide acceptor with corresponding fluorinated thiogalactoside donors. These ligands were subsequently conjugated to a hydrophilic and biocompatible polyoxazoline copolymer scaffold—specifically poly(2-ethyl-2-oxazoline-co-2-but-3-ynyl-2-oxazoline)—using copper-catalyzed azide-alkyne cycloaddition (CuAAC). The resulting multivalent glycopolymers were characterized by 1H NMR and GPC-MALS, confirming high conversion rates and narrow molecular weight distributions.
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2026-06-13
00:01 |
Thermally Induced Transformation of Nickel-Fullerene Hybrid Assembly
Vacík, Jiří ; Ceccio, Giovanni ; Lavrentev, Vasyl ; Lavrenteva, Inna ; Takahashi, K.
Metal-fullerene composites represent a specific class of materials exhibiting interesting properties. However, the thin hybrid assemblies are thermodynamically unstable, thus the destructive processes such as thermal annealing can change their structure and properties.In this work, the thermal stability of nickel-fullerene composites was investigated over a broad temperature range. The evolution of the samples was monitored using Neutron Depth Profiling, Rutherford backscattering, micro-Raman spectroscopy and Scanning Electron Microscopy. The results showed that the hybrid films exhibit phase transformation upon heating, which leads to a dramatic change in their structure and in formation of a new self-assembled material.
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2026-06-13
00:01 |
Synthesis and Modification of Thin NaSICON Solid Electrolytes Using Ion Beams
Ceccio, Giovanni ; Vacík, Jiří ; Mastronardo, I. ; D'Urso, C. ; Štěpanovská, Eva ; Mikšová, Romana
Solid electrolytes (SEs) for sodium-based superionic conductors (NaSICON) were first introduced in 1976 and quickly recognized for their excellent ionic conductivity. While considerable effort has been made to develop thin electrolytes for all-solid-state batteries (ASSBs), only a few sodium-based SEs have been successfully fabricated as thin films. These thin films are particularly desirable for their reduced electrical resistance, which typically increases with the thickness of the SE. By reducing the thickness of the SEs to the nanometer scale, their ionic conductivity can be significantly enhanced.In this study, the NASICON composite was initially prepared in the form of pellets using the mixed oxide technique with a planetary ball mill and synthesized by the solid-state method at 1300 °C. The resulting pellets were used as sputtering targets in a low-energy ion facility to prepare continuous NASICON nanofilms. To explore the effect of ion implantation on the electrical properties of NASICON, the prepared films were bombarded with Ni ions at 1.1 MeV and varying fluences, using the Tandetron accelerator at the CANAM infrastructure (NPI Řež). The electrical properties of both the synthesized and implanted films were analyzed through electrochemical impedance spectroscopy (EIS). The results, describing the impact of irradiation on NASICON's properties, are presented here.
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2026-06-13
00:01 |
Physical principles of Crosslinking of Water-Soluble Polymers for Tissue Engineering
Strnadová, K. ; Lisnenko, M. ; Agazarian, A. ; Chvátil, David ; Matějů, Š. ; Mikule, J. ; Jenčová, V.
hysical crosslinking of water-soluble polymers is a promising route for creating highly pure and biocompatible hydrogel scaffolds, offering an advantage over methods that use potentially cytotoxic chemical reagents. This study investigated the effectiveness of heat treatment and β-electron irradiation for the physical crosslinking of electrospun nanofibrous scaffolds / hydrogel disks derived from synthetic polymer - polyvinyl alcohol (PVA) and natural polymer - gelatin (GEL), focusing on material stability and cytocompatibility. PVA and GEL samples were fabricated and subsequently subjected to either heat treatment or β-electron irradiation before being characterized for morphology, water-solubility, and cytotoxicity (ISO 10993). Both physical methods were found not to significantly alter the nanofiber morphology. Crucially, β-electron irradiation failed to crosslink dry samples, which immediately dissolved, revealing that the presence of water is essential for this crosslinking mechanism. Biologically, physically crosslinked GEL nanofibers demonstrated excellent cell viability, while irradiated PVA nanofibers exhibited unexpected cytotoxicity. Otherwise, cell proliferation with PVA samples was unaffected, compared to GEL samples. Cell adhesion assays were inconclusive and require further investigation. These findings highlight that while physically crosslinked water-soluble polymers are good scaffold candidates, optimizing irradiation conditions, particularly by ensuring proper hydration, is critical for developing stable and functional scaffolds for tissue engineering applications.
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2026-06-13
00:01 |
Study of LAGP Coating on Polythylene Separator for Polysulfide Suppression in Thin Li-S Batteries
Ceccio, Giovanni ; Vacík, Jiří
The use of a thin solid electrolyte layer on polyethylene (PE) separators has been explored as a potential strategy to mitigate the polysulfide shuttle effect in lithium-sulfur (Li-S) batteries, a phenomenon responsible for significantly reducing their lifespan. While some solid electrolytes, such as LAGP (Li1+xAlₓGe2-x(PO4)3), have demonstrated the ability to effectively suppress the shuttle effect, their brittle ceramic nature limits their application, particularly in flexible electronics. Coating PE separators with LAGP nanofilms offers a promising solution by combining the mechanical flexibility and thinness of polymer separators with the electrochemical advantages of LAGP, due to its NASICON-like structure and high ionic conductivity. In this study, PE separators were coated with LAGP nanofilms using the ion sputtering technique and further modified with ferroic elements such as Ni and Co. The surface morphology of the coated separators was analyzed using scanning electron microscopy (SEM), and staircase voltammetry was employed to evaluate the electrochemical performance and modifications induced by the coatings. The results demonstrate that the use of PE separators with a thin LAGP layer significantly influences polysulfide diffusion and suppresses the shuttle effect, thereby reducing unwanted processes in Li-S batteries.
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