2025-05-11
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Headwaters biogeochemistry focused on different rainfall-runoff conditions, and the role of waterlogged areas
Fraindová, K. ; Kliment, Z. ; Matoušková, M. ; Vlček, Lukáš ; Vlach, V.
River headwaters have a high environmental value. Unfortunately, the biogeochemical process in headwaters in context of different rainfall-runoff conditions and specific land cover have not been fully examined. This study focuses on changes in correlations of 16 biogeochemical parameters related to different types of rainfall-runoff events and land cover conditions for eight headwater catchments in Central Europe. Multiple methods as linear regression, Spearman rank correlation, Principal Components Analysis and C/Q hysteresis loops revealed main relationships. Presence of peatlands and waterlogged spruce forests had decisive influence on the biogeochemistry (mainly for COD(Mn), humins, Fe, P-PO4(3-) TP, and N-NO3(-)). The strongest positive correlation of organic matter (COD(Mn)) and Fe is represented in a catchment with the largest area of damaged forest (70 %), but with a smaller proportion of wetlands (8 %). High flow rates influence the release of greater amounts of organic matter and N-NO3(-).
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2025-05-03
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Optical spectra of thin intrinsic and Al doped nanocrystalline zno thin layers deposited by pulsed laser deposition on fused silica glass substrates
Remeš, Zdeněk ; Neykova, Neda ; Jain, N. ; Sharma, K.R. ; Holovský, Jakub ; Ukraintsev, E. ; Míčová, J. ; Hsu, S.S.
Zinc oxide (ZnO) is a low-cost and environmentally friendly material with unique optical properties and a variety of nano and microstructures imposing challenges for energy conversion, scintillators, photocatalytic wastewater treatment, electrochemical energy storage, or sensing applications. In this work, the nominally undoped and Al-doped nanocrystalline ZnO thin layers were pulsed laser deposited (PLD) on fused silica glass. The samples were characterized by photothermal deflection (PDS) and photoluminescence (PLS) spectroscopy. Excitons were observed at low temperature in both samples at about 3.4 eV. The intrinsic samples show the red PL in near infrared region at about 1.9 eV related to zinc vacancies. The results show that optical properties can be evaluated from optical spectra of very thin nanocrystalline ZnO layers with the thickness below 100 nm.
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2025-05-03
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Wet chemistry treatment and surface modification of recycled glass particles for sustainable construction applications
Babčenko, Oleg ; Beranová, Klára ; Remeš, Zdeněk ; Kolářová, Kateřina ; Lörinc, Jakub ; Volf, Jakub ; Prošek, Z. ; Tesárek, P.
The soda-lime glass is recognized as one of the best recyclable materials. However, surface contamination of glass waste or bulk impurities in the glass matrix can significantly alter glass properties limiting its direct reuse in the glass industry. As an alternative utilization strategy, the incorporation of waste glass as a partial replacement for sand or binder in concrete-based materials for sustainable construction applications has shown promise. Nevertheless, impurities in glass that may affect the alkalinity of concrete or calcium-silicate-hydrate formation must be carefully considered. For example, when the glass waste is in the form of shards or small fragments (particles), the potential diffusion of metal ions into the environment (e.g., through reaction with rainwater) becomes an important issue. In this work, we perform wet chemistry treatment on the recycled glass particles obtained from the commercial source. The resulting changes in glass particle properties were analyzed using microscopic and spectroscopic techniques. In particular, changes in the concentrations of Mg, Al, Ca and Na near the particle surfaces were detected, indicating potential to elements release to the environment via leaching. The observed results can be helpful in the explanation of processes at interfacial transition zones in waste glass containing concrete-based materials.
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2025-05-03
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Metallic and semiconductor nanoparticles integrated into thin layers of hydrogenated amorphous silicon or silicon carbide
Stuchlík, Jiří ; Kupčík, Jaroslav ; Čermák, Jan ; Stuchlíková, The-Ha ; Remeš, Zdeněk
The combination of PECVD - plasma enhanced chemical vapor deposition and VE - vacuum evaporation at one vacuum chamber is in situ method how to integrate semiconductor (Ge) and metallic (Sn) nanoparticles into amorphous hydrogenated thin films and their structures on the base of a-Si:H or a-SiC:H. In this work we focus our effort to deposit a-SiC:H thin films from monomethylsilane (MMS = SiH3-CH3) diluted by hydrogen in the ratio 2/100 sccm. The Ge evaporates at vacuum higher than 2E-5 Pa. The TEM - transmission electron microscopy and AFM - atomic force microscopy are used for microscopical characterization of thin films while PDS - photothermal deflection spectroscopy and PL – photoluminescence spectroscopy are used for their spectroscopical characterization.
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2025-05-03
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Nanocomposites of ZnO-decorated HPHT Nanodiamond as a perspective green photocatalysts
Mičová, J. ; Košutová, T. ; Jerigová, M. ; Remeš, Zdeněk
Electrical and optical properties of zinc oxide, in particular the relatively wide direct band gap of ~3.3 eV predetermines ZnO as a photocatalytic material at room temperature. ZnO itself is non-toxic and the hydrothermal growth method we use to prepare its nanostructures is environmentally friendly. These facts contribute to the attractiveness of this material. Recently, we have focused on studying the influence of doping or of plasma surface treatment on the photocatalytic efficiency of ZnO. However, the main disadvantages are the high recombination rate of charge carriers and the poor use of visible light. The solution is the use of ZnO as part of nanocomposites. In the past, ZnO-detonation nanodiamons (DND) composites were studied. The disadvantage of DND is the formation of clusters of different sizes, therefore we focused our attention on the use of HPHT nanodiamonds (NDs). We modified the surface of commercial HPHT NDs by oxidation in order to increase the concentration of hydroxyl-, carbonyl- and carboxyl- functional groups. The resulting ZnO-HPHT NDs composites were synthesized using a dehydration-condensation process between oxygen-containing functional groups on the NDs surface and hydroxyl groups on the ZnO surface. The prepared nanocomposites were characterized by SEM, AFM, FTIR and PL and tested by photocatalytic dye degradation.
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2025-05-03
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VIS, UV and DUV wavelength extension of Yb:YAG diode-pumped thin-disk laser
Šatra, Šimon ; Novák, Ondřej ; Turčičová, Hana ; Mužík, Jiří ; Smrž, Martin ; Mocek, Tomáš
Application possibilities of picosecond diode-pumped Yb:YAG thin-disk laser have been expanded by installation of harmonics generation system. Fundamental, second, third, fourth, and fifth harmonic frequencies are now available for users at output powers of 70 W, 40 W, 20 W, 10 W, and 2 W, respectively. Nonlinear crystals used for the conversions are LBO (SHG, THG), BBO (FHG, FiHG), and CLBO (FHG, FiHG). The users profit from all the harmonic frequencies. Recent results on harmonics and its applications will be presented.
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2025-04-20
01:11 |
Separation of cyclic diadenosine diphosphorothioate and the diastereomers of its difluorinated derivative and estimation of binding constants of their complexes with 2-hydroxypropyl-β-cyclodextrin by affinity capillary electrophoresis
Štěpánová, Sille ; Břehová, Petra ; Kašička, Václav
Cyclic dinucleotides (CDNs) are known to activate the stimulator of interferon genes (STING), a protein that is a member of the cyclic-guanosine-adenosine synthase-STING signaling pathway and that is important for the innate immune response in eukaryotic cells. CDNs contain two ribonucleoside monophosphates linked via 3′–5′ or 2′–5′ phosphodiester bonds. Many therapeutic oligonucleotides contain phosphorothioate modification. The aim of this work was to develop a new affinity capillary electrophoresis (ACE) method for the separation of a potential anticancer drug, 2′,3′-cyclic diadenosine diphosphorothioate (Rp, Rp) (ADU-S100), and three recently synthesized diastereomers of its difluorinated derivative, 3′,3′-cyclic di(2′-fluoro,2′-deoxyadenosine phosphorothioate) [1] (see Fig. 1) using native (α-, β-, and γ-cyclodextrins (CDs)) or modified CDs (2-hydroxypropyl-β-CD (HP-β-CD) and 2-hydroxypropyl-γ-CD (HP-γ-CD)) as chiral selectors. In addition, the background electrolyte (BGE) composition and the concentration of the suitable CD should be optimized. Moreover, ACE should be applied for the estimation of the average apparent binding constants of the complexes of the analyzed CDNs with the chiral selector providing best separation.
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2025-04-20
01:11 |
Analysis and physico-chemical characterization of peptides and lipopeptides regulating food intake by capillary electrophoresis and isotachophoresis
Šolínová, Veronika ; Křížková, Adéla ; Maletínská, Lenka ; Kašička, Václav
New lipidized analogs of peptides (ghrelin, prolactin-releasing peptide (PrRP) and cocaine- and amphetamine-regulated transkript peptide (CARTP)) are studied for regulation of food intake.\nGhrelin (28 amino acids) is native peptide hormone, which is secreted in the stomach and acts both peripherally and centrally [1]. PrRP (31 amino acids) was discovered as a ligand for an\norphan G-protein coupled receptor GPR 10 and as a regulator of prolactin release [2]. The CARTP (42 amino acids) is a brain-born and brain-acting neuropeptide with anorexigenic properties regulating hormone leptin [3]. The inability of these peptides to cross blood-brain barrier to their target receptors may be overcome by their lipidization at biologically inactive sites of their molecules. The set of ten (lipo)peptides was synthesized to be tested as potential drugs. Prior their application, they have to be analyzed and characterized. For that reason, the aim of this work was to check their purity and to characterize their acid-base properties by capillary zone electrophoresis (CZE) and capillary isotachophoresis (CITP).
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2025-04-20
01:11 |
Separation of selected catecholamines and determination of binding constants of their complexes with HS-β-CD by capillary electrophoresis
Sázelová, Petra ; Jiráček, Jiří ; Kašička, Václav
Catecholamines play an important role in carbohydrate and fat metabolism, cardiovascular system regulation, unstriped musculature function, blood coagulation, and the regulation of the acute adaptive reactions of the body. Analyses of the most important neurotransmitters such as dopamine, adrenaline and noradrenaline are of great significance for diagnostics and treatment of various brain diseases. The main path of formation of catecholamines in the body is: tyrosine - dihydroxyphenylalanine (DOPA) - dopamine - noradrenaline - adrenaline. L-DOPA (levodopa) is a chiral drug used in the treatment of Parkinson's disease, which is related to the depletion of the dopamine in the brain. Only this enantiomer is converted to dopamine while D-DOPA may cause side effects. Hence, control of enantiomeric purity of L-DOPA is necessary. Capillary electrophoresis (CE) using chiral selectors, among them especially cyclodextrins, is powerful tool for separation of enantiomers [1].
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2025-04-20
01:11 |
Chiral separation of ketamine and its metabolites from rat plasma samples using partial filling CE-ESI/MS
Konášová, Renáta ; Koval, Dušan ; Tůma, P. ; Kašička, Václav
Ketamine is a chiral drug used for a nearly 60 years to induce and maintain anaesthesia. In addition, ketamine and especially its metabolites act as antidepressants. For that reason, the mechanisms of action of these species have been studied. Different effects of enantiomers of ketamine and its metabolites were observed. S-ketamine has about twice the analgesic potency\nthan the clinically used racemic mixture [1] and is supposed to be responsible for high abuse liability of ketamine [2]. The metabolism of R-ketamine to 2R,6R-hydroxynorketamine is essential for its antidepressant effect [3]. Ketamine and its main metabolites were successfully separated by capillary zone electrophoresis (CZE) [4] but a complete separation of enantiomers of ketamine (Ket) and its main metabolites, norketamine (NK), dehydronorketamine (DHNK) and hydroxynorketamine (HNK), has not yet been achieved. The recently developed LC-MS method requires one achiral and two chiral columns for separation of six enantiomers [5]. Therefore, the aim of this work was to develop a new CZE method that could separate the enantiomers of all above species in a single run.
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