Comenius University Bratislava
  • Bratislava, Slovakia
Recent publications
Although the general concept of nanotechnology relies on exploitation of size-dependent properties of nanoscaled materials, the relation between the size/morphology of nanoparticles with their biological activity remains not well understood. Therefore, we aimed at investigating the biological activity of Se nanoparticles, one of the most promising candidates of nanomaterials for biomedicine, possessing the same crystal structure, but differing in morphology (nanorods vs. spherical particles) and aspect ratios (AR, 11.5 vs. 22.3 vs. 1.0) in human cells and BALB/c mice. Herein, we report that in case of nanorod-shaped Se nanomaterials, AR is a critical factor describing their cytotoxicity and biocompatibility. However, spherical nanoparticles (AR 1.0) do not fit this statement and exhibit markedly higher cytotoxicity than lower-AR Se nanorods. Beside of cytotoxicity, we also show that morphology and size substantially affect the uptake and intracellular fate of Se nanomaterials. In line with in vitro data, in vivo i.v. administration of Se nanomaterials revealed the highest toxicity for higher-AR nanorods followed by spherical nanoparticles and lower-AR nanorods. Moreover, we revealed that Se nanomaterials are able to alter intracellular redox homeostasis, and affect the acidic intracellular vesicles and cytoskeletal architecture in a size- and morphology-dependent manner. Although the tested nanoparticles were produced from the similar sources, their behavior differs markedly, since each type is promising for several various application scenarios, and the presented testing protocol could serve as a concept standardizing the biological relevance of the size and morphology of the various types of nanomaterials and nanoparticles.
In this paper, we investigate steady equatorial flows beneath solitary water waves subject to the Coriolis effect, which propagate over a flat bed. In particular, we focus on irrotational flows and present some properties of velocity field, behavior of the pressure and the extrema of the dynamic pressure. In addition, we provide some estimates for the elevation of wave from pressure measurements at an arbitrary intermediate depth. The analysis is based on the maximum principles.
A series of five decavanadates (V10) using a simple, one-pot synthesis, adhering to the model template: transition metal ion – decavanadate – ligands:(Hnicotinamide)2{[Co(H2O)3(nicotinamide)2]2[μ-V10O28]}.6H2O (1), {[Co(H2O)4(isonicotinamide)2]3}V10O28·4H2O (2), {[Co(H2O)4]2[Co(H2O)2(μ-pyrazinamide)2][μ-V10O28]}·4H2O (3) {[Co(H2O)4(μ-pyrazinamide)]3.V10O28}·4H2O (4), and (NH4)2{[Ni(H2O)4(2-hydroxyethylpyridine)]2}V10O28·2H2O (5) was synthesized. X-ray analysis reveals that 1 and 3 are decavanadato complexes, while 2, 4 and 5 are decavanadate complex salts. Moreover, 3 is the first example of a polymeric decavanadato complex, employing direct coordination with the metal center and the organic ligand, in toto. From the solution studies using ⁵¹V NMR spectroscopy, it was decoded that 1 and 3 stay stable in the model buffer solution and aqueous media. Binding to model proteins, cytotoxicity and water oxidation catalysis (WOC) was studied primarily for 1 and 3 and concluded that neither 1 nor 3 have an interaction with the model proteins thaumatin, lysozyme and proteinase K, because of the presence of the organic ligands in the Co(II) center, any further interplay with the proteins was blocked. Cytotoxicity studies reveal that 1 is 40% less toxic (0.05 mM) and 26% less toxic (0.1 mM) than the uncoordinated V10 with human cell lines A549 and HeLa respectively. In WOC, 1 performed superior activity, by evolving 143.37 nmol of O2 which is 700% (9-fold) increase than the uncoordinated V10.
The chronology of past landslide movements is a key source of information for effective landslide hazard determination. Dendrogeomorphological methods are currently an effective tool for obtaining chronological data but still encounter limitations in extracting landslide signals from yearly series. These limitations can be reduced by introducing anatomical analyses of the yearly series. Black locust (Robinia pseudoacacia L.), a widespread tree species occupying landslides on river banks, has been surprisingly rare in dendrogeomorphology. Thus, this study focused on the effectiveness of using both standard macroscopic signals (tree-ring eccentricity) and anatomical growth responses of this species in a dendrogeomorphic analysis of landslide movements at one of the landslide hot spots in Central Europe (the Váh River bank). Analysis of the eccentricity of tree rings from 67 individuals of R. pseudoacacia allowed us to reconstruct 13 landslide events over the last 49 years. From an anatomical point of view, a strong association was found between a significant reduction in vessel lumen area and the eccentricity of the tree rings and the tilting of the tree stems. A possible cause of the anatomical response is a combination of root damage from subsurface landslide movements and occasional tension wood formation following tree tilting. The constructed chronology confirmed the known years of landslide activity and generally complemented the known chronology. One of the results of the study is the implication for effective evaluation of the spatial extent of landslide activity, considering tree-ring-based magnitude-frequency relationships. The results of this study will thus allow further extension of the use of dendrogeomorphological methods both methodologically and biogeographically.
Drought stress impairs plant growth leading to depression in yield. This experiment aimed to elucidate the substantial impact of silicon (Si) [in forms of SiO2 and SiO2-nanoparticles (SiO2-NPs)] on modulating adverse effects of drought stress on strawberry plants. The plants grown in the greenhouse were exposed to drought stress simulating 25% field capacity (FC) (severe stress), 50% FC (moderate stress), and 100% FC (control). The strawberry plants were then sprayed with suspensions containing SiO2 or SiO2-NPs (50 mg L⁻¹). The SiO2 treatment improved morphological parameters (number of plant leaves and length of petiole). Under drought stress, application of foliar SiO2 and SiO2-NPs increased osmolytes such as proline and total soluble sugar and improved chlorophylls (Chl a, Chl b, and total Chl) and carotenoids (CARs) as well as Chl fluorescence in strawberry plants as compared to non-treated ones. Moreover, treatment by SiO2 raised tolerance to drought by promoting the activity of antioxidant enzymes such as peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) as well as reduced hydrogen peroxide (H2O2) and malondialdehyde (MDA) activity in strawberry plants. Drought stressed strawberry plants treated by Si exhibited the recovery in antioxidant activity and phenolic compounds as non-enzymatic antioxidants. The modifications of abscisic acid and phenolic compounds occurred following up-regulation of some responsive genes as a beneficiary response to drought stress when SiO2 and SiO2-NPs were applied. This application of SiO2 and SiO2-NPs can contribute to protect strawberry plants against damaging effects of drought stress.
Voronoi diagrams belong to frequently used structures in computational geometry with application in many fields of science. The properties of Voronoi diagram are already studied in various metric spaces – Euclidean, Manhattan, Minkowski, Hausdorff, or Karlsruhe and also in the hyperbolic metric. In this paper, we focus on the Voronoi diagram and its dual in the Poincaré ball model of the three-dimensional hyperbolic space. We first present some basic tools from the Poincaré ball model needed to construct a Voronoi diagram and for a closer observation of its properties. We have determined certain conditions for the position of the generators controlling the behavior of the hyperbolic Voronoi diagram. In the last section, we demonstrate this effect on the dual graph of a hyperbolic Voronoi diagram, i. e., on hyperbolic Delaunay tessellations.
Let O=(0,0) be the intersection point of two plane algebraic curves F and G. According to existing results, we know that their intersection multiplicity IO at O satisfies the inequality IO(F,G)≥mn+t, where m and n are the multiplicities of O on F and G respectively, and t is the number of their common tangents at O (counted with multiplicity). The aim of this paper is to investigate under which conditions the equality occurs. These conditions are given in terms of individual common tangents of F and G at O and their relations to the polynomials defining these curves.
Despite being the busiest transient sea in the world due to the Suez Canal, radionuclide distribution studies in seawater and sediment of the Red Sea remain rare. A sampling expedition in the Red Sea was conducted from June 9 to July 6, 2021, visiting a transect of several deep sampling stations located along the central axis of the basin from the Gulf of Aqaba to the southern Red Sea (near Farasan Island, Saudi Arabia). The collected seawater profile samples were analyzed for tritium, radiocarbon and oxygen-18. The observed tritium levels in surface waters of the Red Sea peaked at 0.3–0.4 TU, similar to the values observed in the western Arabian Sea (decay corrected). The values observed at waters below 150 m were around 0.2 TU, however, at depths of 450 and 750 m, tritium minima (<0.2 TU) were observed, which could be associated with a partial return flow of bottom waters from the southern to the northern Red Sea. At two stations at the depth of about 550 m, deep Δ¹⁴C minima were observed as well (−4‰ and −10‰), documenting ongoing transport of carbon in the water column, important for sink of anthropogenic carbon.
We studied whether elderly women at risk for fractures receive primary care treatment to prevent fracture. We found that across Europe, women at risk are often not identified, and less than half of such women receive appropriate treatment. Finally, women diagnosed with osteoporosis are much more likely to receive treatment. Purpose: To examine the relationship between risk factors for fragility fracture (FF) and osteoporosis (OP) treatment gap in elderly women across Europe, and compare the prevalence of risk factors between countries. Methods: Demographic and clinical information was collected from women ≥ 70 years visiting primary care physicians in Belgium, France, Germany, Ireland, Poland, Slovakia, Switzerland, and the UK. Increased risk of FF was defined by the presence of 1 or more criteria (history of fracture, 10-year fracture probability, or T-score ≤ - 2.5). Results: There were 3798 women in total. Treatment gap (proportion at increased risk of FF not receiving treatment for OP) varied from 53.1 to 90.8% across countries, and the proportion of patients at increased risk of FF varied from 41.2 to 76.1%. Across countries, less than 50% of patients with increased risk of FF had a diagnosis of OP. Previous fracture was the most common risk factor, with similar prevalence across most countries; other risk factors varied widely. The treatment gap was reduced in patients with an OP diagnosis in all countries, but this reduction varied from 36.5 to 79.4%. The countries with the lowest rates of bone densitometry scans (Poland, France, and Germany; 8.3-12.3%) also had the highest treatment gap (82.2 to 90.8%). Conclusions: This study highlights differences across Europe in clinical risk factors for fracture, rates of densitometry scanning, and the rates of OP diagnosis. More emphasis is needed on risk assessment to improve the identification and treatment of elderly women at risk for fracture.
The accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton–proton collisions delivered by the Large Hadron Collider presents a significant challenge to the computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in Monte Carlo (MC) production. In this document, a new method to account for these additional interactions in the simulation chain is described. Instead of sampling the inelastic interactions and adding their energy deposits to a hard-scatter interaction one-by-one, the inelastic interactions are presampled, independent of the hard scatter, and stored as combined events. Consequently, for each hard-scatter interaction, only one such presampled event needs to be added as part of the simulation chain. For the Run 2 simulation chain, with an average of 35 interactions per bunch crossing, this new method provides a substantial reduction in MC production CPU needs of around 20%, while reproducing the properties of the reconstructed quantities relevant for physics analyses with good accuracy.
Background Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by defects in genes coding for different lysosomal enzymes which degrade glycosaminoglycans. Impaired lysosomal degradation causes cell dysfunction leading to progressive multiorgan involvement, disabling consequences and poor life expectancy. Enzyme replacement therapy (ERT) is now available for most MPS types, offering beneficial effects on disease progression and improving quality of life of patients. The landscape of MPS in Europe is not completely described and studies on availability of treatment show that ERT is not adequately implemented, particularly in Southern and Eastern Europe. In this study we performed a survey analysis in main specialist centers in Southern and Eastern European countries, to outline the picture of disease management in the region and understand ERT implementation. Since the considerable number of MPS IVA patients in the region, particularly adults, the study mainly focused on MPS IVA management and treatment. Results 19 experts from 14 Southern and Eastern European countries in total responded to the survey. Results outlined a picture of MPS management in the region, with a high number of MPS patients managed in the centers and a high level of care. MPS II was the most prevalent followed by MPS IVA, with a particular high number of adult patients. The study particularly focused on management and treatment of MPS IVA patients. Adherence to current European Guidelines for follow-up of MPS IVA patients is generally adequate, although some important assessments are reported as difficult due to the lack of MPS skilled specialists. Availability of ERT in Southern and Eastern European countries is generally in line with other European regions, even though regulatory, organizational and reimbursement constrains are demanding. Conclusions The landscape of MPS in Southern and Eastern European countries is generally comparable to that of other European regions, regarding epidemiology, treatment accessibility and follow up difficulties. However, issues limiting ERT availability and reimbursement should be simplified, to start treatment as early as possible and make it available for more patients. Besides, educational programs dedicated to specialists should be implemented, particularly for pediatricians, clinical geneticists, surgeons, anesthesiologists and neurologists.
Background Physical exercise has favorable effects on the structure of gut microbiota and metabolite production in sedentary subjects. However, little is known whether adjustments in an athletic program impact overall changes of gut microbiome in high-level athletes. We therefore characterized fecal microbiota and serum metabolites in response to a 7-week, high-intensity training program and consumption of probiotic Bryndza cheese. Methods Fecal and blood samples and training logs were collected from young competitive male ( n = 17) and female ( n = 7) swimmers. Fecal microbiota were categorized using specific primers targeting the V1–V3 region of 16S rDNA, and serum metabolites were characterized by NMR-spectroscopic analysis and by multivariate statistical analysis, Spearman rank correlations, and Random Forest models. Results We found higher α-diversity, represented by the Shannon index value (HITB-pre 5.9 [± 0.4]; HITB-post 6.4 [± 0.4], p = 0.007), (HIT-pre 5.5 [± 0.6]; HIT-post 5.9 [± 0.6], p = 0.015), after the end of the training program in both groups independently of Bryndza cheese consumption. However, Lactococcus spp . increased in both groups, with a higher effect in the Bryndza cheese consumers (HITB-pre 0.0021 [± 0.0055]; HITB-post 0.0268 [± 0.0542], p = 0.008), (HIT-pre 0.0014 [± 0.0036]; HIT-post 0.0068 [± 0.0095], p = 0.046). Concomitant with the increase of high-intensity exercise and the resulting increase of anaerobic metabolism proportion, pyruvate ( p [HITB] = 0.003; p [HIT] = 0.000) and lactate ( p [HITB] = 0.000; p [HIT] = 0.030) increased, whereas acetate ( p [HITB] = 0.000; p [HIT] = 0.002) and butyrate ( p [HITB] = 0.091; p [HIT] = 0.019) significantly decreased. Conclusions Together, these data demonstrate a significant effect of high-intensity training (HIT) on both gut microbiota composition and serum energy metabolites. Thus, the combination of intensive athletic training with the use of natural probiotics is beneficial because of the increase in the relative abundance of lactic acid bacteria.
In this work, with the aid of the representation of the solution, the relative controllability for delaying linear discrete systems with a second-order difference is principally investigated. Utilizing the delayed discrete matrix function, we give a sufficient criteria for relative controllability, and construct a relevant control function. Lastly, an example is presented to demonstrate the effectiveness of theoretical result.
Bushfire occurrences will likely be exacerbated by climate change, thus requiring a model to forecast and manage their impacts. However, a robust bushfire model requires new proxies that can infer fire severity responses to past climate variability. A key test to the viability of new fire proxies is whether they record fire severity in the affected soil. We address this by testing Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR) spectroscopy and boron (B) isotopes in soil clay fractions from Yengo National Park, southeastern Australia, as proxies for bushfire severity. The isotopic results were also compared to that of clays that reacted with experimentally combusted bark. ATR-FTIR spectroscopy constrains the soil temperature to between 225 and 500 °C during high severity fires, based on the lack of dehydroxylation peak characteristics and the increased aromatic to aliphatic organic peak ratios in clays, compared to that of low severity sites. The isotope composition of the non-exchangeable B fraction in clays is lighter after reacting with leaching solutions of bark combusted at higher temperatures. Combustion temperature does not affect the B isotope fractionation during B adsorption onto clays. Changes to the B isotope composition of clays could instead be justified by the varying B concentration and B isotope compositions of the leaching solutions. In Yengo soil clay fractions, sites that experienced a high severity fire show higher δ¹¹B values by about 1.5 ‰, compared to low severity sites- at odds with observations from our experiment using combusted bark. The combustion of leaves from tree crowns in high severity fires could account for the increase in δ¹¹B of clays post-fire. In summary, FTIR spectroscopy of clays could be useful for constraining soil temperature during bushfires, while the B isotope composition of clays appears as a promising proxy for fire severity.
This paper presents the preparation and study of new ceramics of Ag⁺-conductive solid electrolytes. Ceramic disks of Ag6+x(P1-xGex)S5I (х = 0; 0.25; 0.5; 0.75) solid solutions were obtained in two stages: cold pressing to a relative density of 91 ± 1% and annealing at 923 K. The prepared Ag6+x(P1-xGex)S5I ceramics were investigated by SEM, EDS, impedance spectroscopy and microhardness measurement. Ceramic materials are phase homogeneous, and the average size of crystallites in annealed ceramic materials stays in the range of ∼3.1–4.7 μm, and the porosity is 6–8%. Ag6+x(P1-xGex)S5I ceramics belong to ion-electron conductors with a significant predominance of ionic conductivity. The compositional dependence of ionic conductivity and its activation energy isn't monotonous. The highest values of ionic conductivity 4.8 × 10⁻² S/cm (298 K) are obtained for the Ag6.75(P0.25Ge0.75)S5I, and the minimum activation energy 0.093 eV for Ag6.5P0.5Ge0.5S5I composition. The influence of microstructure and recrystallization process on electrical parameters of Ag6+x(P1-xGex)S5I ceramics is discussed.
In this paper, periodic solutions of quaternion-valued impulsive differential equations (QIDEs) are considered. First, the sufficient and necessary conditions to guarantee periodic solutions are given for linear homogeneous QIDEs. Second, the representations of periodic solutions are derived by constructingGreen functions in one case, and the sufficient and necessary conditions to guarantee periodic solutions are presented by means of adjoint systems in the other case for linear nonhomogeneous QIDEs. In addition, the existence and uniqueness of periodic solutions are studied by virtue of fixed point theorems for semilinear QIDEs. All results in the sense of complex-valued and quaternion-valued are equivalent to each other due to the adjoint matrix of quaternion matrix and the isomorphism between quaternion vector space and complex variables space. Finally, examples and simulations are provided to demonstrate the validity of our main results.
The paper studies how unions used two types of resources, namely, access to national legislation/policy and to collective bargaining, to improve working conditions in healthcare and in agency work in Czechia and Slovakia. It examines how these two types of institutional resources interact, whether they are potentially in competition and how this affects union revitalization. Unions’ post-2008 strategies in the two sectors converged towards political action due to their preference for legislative regulation of issues previously bargained about or unregulated. The paper argues that extensive use of institutional safeguards contributes to improving working conditions; however, prioritizing political action may weaken other types of union strategies and undermine future access to collective bargaining. In other words, extensive utilization of one institutional resource (legislation) may gradually weaken other types of resources (collective bargaining) and thereby undermine the overall revitalization capacity of trade unions.
The present review summarizes the research progress related to some green approaches in atomic absorption spectrometry in the period from 2012 to 2021. The main points of the present review include green sample introduction and microextraction techniques and their use in different atomic absorption spectrometry techniques. The review is focused on the application of the presented green approaches for the determination of metals in various samples. Some advantages or disadvantages of these approaches are also discussed.
Severe traumatic brain injury (sTBI) is a major cause of death and disability worldwide, resulting in a significant individual and socioeconomic burden. Current treatment guidelines do not include any recommendations for neuroprotective or neuoregenerative drugs. Here, we present a combined treatment with Cerebrolysin and Citicoline in two cases. Both drugs are experimentally better than clinically proven in their own effectiveness, but there is almost no clinical data on the combination of the two. Our case study hints at a promising approach that may improve neurological outcome after sTBI. The first patient was a 29 years male motorcyclist suffered polytrauma in a high‐speed accident. He had severe bilateral chest trauma and fractures in both thighs and an sTBI. In addition to surgical and standard neurocritical care according to the evidence‐based guidelines, he was given neuroprotective therapy with Cerebrolysin (50 ml/day) and Citicoline (3 g/day), by continuous intravenous infusion (IV), for 21 days. The second patient was a 30 years male ski mountaineer who had suffered a fall over 300 m in open terrain. In addition to the sTBI, he had fractures in the cervical spine, ribs, pelvis, and lower extremities, as well as lung contusions and massive soft tissue trauma. After initial treatment in a local hospital, he was transferred to our department and received the same neuroprotective drugs, like all of our patients with sTBI. Considering the severity of the injuries (Injury Severity Score [ISS]: 43/50, Revised Trauma Score [RTS: 5.0304, 2.7794]) and the unfavorable outcome probability (Hukkelhoven Score) of 93.1% and 82.6%, the outcomes of both patients are surprisingly encouraging 1 year after the accident. They achieved a Glasgow Outcome Score of 6 and 5 and grades 2 and 4 on the modified Rankin Scale, respectively. Currently, both are able to take care of themselves in activities of daily life to a large extent. Neuroprotective drugs may improve the regeneration of cell membranes, improve blood brain barrier integrity, and reduce neuroinflammation leading to secondary damage to the injured brain. Our clinical experience and data suggest that the combined administration of Citicoline and Cerebrolysin may contribute to better recovery, without relevant side effects. However, it would be important to validate these results by means of a controlled, prospective study.
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9,766 members
Matus Hyzny
  • Department of Geology and Paleontology
Radovan Sebesta
  • Department of Organic Chemistry
Martin Janik
  • Department of Forensic Medicine
Stloukal Eduard
  • Department of Zoology
Šafárikovo námestie 6, 814 99, Bratislava, Slovakia
Head of institution
Prof. Marek Števček, rector