Molecular modeling of ZnS nanoparticles on kaolinite surface

Diplomová práce je zaměřena na charakterizaci struktury nanokompozitu na bázi kaolinitu s nanočásticemi sulfidu zinečnatého. Skutečnost, že v rámci simulací v podobě modelů existuje veliké množství, v jaké poloze, vzdálenosti nebo natočení lze nanočástice vůči kaolinitu usadit, je nutné kombinovat více přístupů k řešení dané problematiky. Molekulární modelování nanokompozitu probíhalo v prostředí modelovacího programu Materials Studio. Studovány byly především interakční energie mezi nanočásticemi a povrchem kaolinitu, v závislosti na typu daného povrchu, velikosti a umístění nanočástic. Dále bylo provedeno hodnocení strukturní kompatibility pomocí softwarových nástrojů ve výpočetním prostředí MatLab a následné porovnání výsledků těchto dvou přístupů. Oba přístupy k řešení byly navíc srovnány s analýzou reálného vzorku nanokompozitu pomocí analýzy HRTEM. Výsledky této práce mohou být nápomocny pro hlubší charakterizaci nanokompozitů typu nanočástice/fylosilikát.The thesis is focused on characterization of nanocomposite structure based on kaolinite with zinc sulphide nanoparticles. Since large number of options in which location, distance or rotation the nanoparticle can be positioned on the kaolinite, combination of various approaches is needed to solve the problem. The molecular modeling was performed in the Materials Studio modeling environment. In particular, the interaction energies between the nanoparticles and the kaolinite surface in dependence on the type of surface, size, and location of the nanoparticles were studied. Furthermore, structure compatibility was determined using software tools in MatLab environment, and both approaches were compared. Moreover, results of these approaches were compared with HRTEM analysis of real sample of the nanocomposite. Results of the thesis can be helpful for deeper characterization of nanoparticle/phyllosilicate nanocomposites.9360 - Centrum nanotechnologiívýborn

Stress reactions of plants following metal oxide nanoparticle exposure

Ke stanovení míry fyziologického stresu v buňkách známého biomonitoru Pleurozium schreberi, byla vybrána titrační metoda stanovení kyseliny askorbové. Obsah kyseliny askorbové bylo stanoveno ve vzorcích mechu, které byly po dobu pěti týdnů vystaveny suspenzi nanočástic ZnO, za pomocí 2 % kyseliny metafosforečné a titračního činidla 2,6-dichlorfenolindofenolu. Dále bylo rovněž sledováno ovlivnění míry vyvolaného stresu v závislosti na různých podmínkách, kterým byl mech během experimentu vystaven. Míra vyvolaného stresu byla u všech vzorků závislá jak na podmínkách experimentu, tak zdali vzorky byly exponovány nebo nikoli. Metoda je vhodnou částí biomonitoringu znečištění nanočásticemi.To determine the degree of physiological stress in the cells of the known biomonitor Pleurozium schreberi, the titration method for the determination of ascorbic acid was chosen. The ascorbic acid content was determined in moss samples that were exposed to a suspension of ZnO nanoparticles for 5 weeks with 2% metaphosphoric acid and 2,6-dichlorophenolindophenol titration reagent. In addition, the effect of the stress-induced rate was monitored, depending on the different conditions the moss experienced during the experiment. The rate of stress induced in all samples was dependent both on the conditions of the experiment and whether or not the samples were exposed. The method is a suitable part of biomonitoring of nanoparticle pollution.9360 - Centrum nanotechnologiívýborn

Disparities in methods used to determine microplastics in the aquatic environment: A review of legislation, sampling process and instrumental analysis

Plastic particles smaller than 5 mm, i.e., microplastics, have been detected in a number of environments. The number of studies on microplastics in marine environments, fresh water, wastewater, the atmosphere, and the human body are increasing along with a rise in the amounts of plastic materials introduced into the environment every year, all contributing to a range of health and environmental issues. Although the use of primary microplastics has been gradually reduced by recent legislation in many countries, new knowledge and data on these problems are needed to understand the overall lifecycle of secondary microplastics in particular. The aim of this review is to provide unified information on the pathways of microplastics into the environment, their degradation, and related legislation, with a special focus on the methods of their sampling, determination, and instrumental analysis. To deal with the health and environmental issues associated with the abundance of microplastics in the environment, researchers should focus on agreeing on a uniform methodology to determine the gravity of the problem through obtaining comparable data, thus leading to new and stricter legislation enforcing more sustainable plastic production and recycling, and hopefully contributing to reversing the trend of high amounts of microplastics worldwide.Web of Science1814art. no. 760

Analytical, stochastic and experimental solution of the osteosynthesis of the fifth metatarsal by headless screw

This paper evaluates the various approaches to strength and stiffness analysis of fracture osteosynthesis using a headless Herbert screw. The problem has been extensively addressed using several scientific approaches, namely the analytical approach, stochastic approach, experimental approach, and (marginally) using the finite elements method. The problem is illustrated on the use of a prototype headless screw Ti: 4.0/1.4 x 30/7 (manufacturer: Medin, Czech Republic) and the surgical treatment of the fifth metatarsal fracture. Mathematical equations for the analytical calculation of the maximum stresses in the screw were established for tensile/compression loading. This problem is also interesting because of its static indetermination in tension and compression; for this reason, it was necessary to use the deformation condition, i.e., the relationship between screw extension and bone contraction. The stochastic (probabilistic) approach, i.e., application of the Monte Carlo method, takes advantage of the mathematical equations derived during the analytical solution by respecting of the natural variabilities and uncertainties. The analytical and stochastic approaches were validated by measurements on porcine bones and by the finite element method. The data measured experimentally were also processed and used for deriving an equation, appropriately approximating the data. The main part of the measurement was to determine the axial force generated during osteosynthesis with a headless screw. The obtained compressional force was used to determine the maximal stress in the screw and bone. Finally, the methods were compared. In this paper, comprehensive and original approaches based on the authors' experience with multiple methods are presented. Obtained results are necessary for headless screw designers during optimalization of the implants and are also useful for surgeons developing new surgical techniques. This biomechanical problem was solved in cooperation with the engineering industry and physicians to improve the quality of care for patients with trauma in orthopedics and surgery.Web of Science1219art. no. 961

Protection Function of Labour Law in Collective Labour Law Relations (Labour Law and Criminal Law Aspects of Strike)

The basic and typical function of the labour law is its protection function which is oriented mainly towards the weaker party of the employment relationship – the employee. However, this function should be maintained also in relation to the employer. An important area of activity of employees’ representatives – the trade union is the area of collective bargaining. In the context of collective bargaining there may also occur the realisation of a strike which we will address from the perspective of the “balanced protective function” of the labour law. The aim of the paper is to investigate the possible limits of the right to strike, especially in terms of “maintaining the existence” of the employer (especially in plants where the interruption of operation can cause ecological disasters and threats to the lives of employees)

Influence of nano-ZnO exposure to plants on L-ascorbic acid levels: Indication of nanoparticle-induced oxidative stress

With the continuously growing production of nanomaterials, their presence in the environment increases. The effects of nanoparticle exposure on plants are yet not fully understood. This study aimed to provide new insights into the stress induced by the exposure of plants to nanoparticles via the determination of the content of L-ascorbic acid, known antioxidant, in the samples of bryophyte species Pleurozium schreberi (Brid.) Mitt. Bryophyte samples, collected from a pristine environment, were exposed to 0.1 g.L-1 suspensions of nano-ZnO for five weeks. Prior to the exposure, the samples were subjected to the combination of treatments-washing or not washing as well as drying or irrigation. In order to assess the level of oxidative stress caused by the exposure to the ZnO nanoparticles under various pre-treatment conditions, the content of the L-ascorbic acid in the samples was determined by titration with dichlorophenolindophenol. Effect of both nano-ZnO exposure and pre-treatment was observed; nano-ZnO exposure significantly reduced the content of L-ascorbic acid in the bryophyte samples indicating it being consumed in the repair processes following the exposure-related physiological stress.Web of Science1953023301

Simple and fast method for determination of preferred crystallographic orientation of nanoparticles: A study on ZnS/kaolinite nanocomposite

Crystallographic orientation of nanoparticles anchored on surface of solid crystalline matrix plays an important role in the resulting activity (e.g. the catalytic activity) of such structured nanocomposites. Possibility to predict the crystallographic orientation can thus be advantageous in many areas of materials science. This study presents a simple method of such prediction by determining the structure compatibility of two crystal structures based on the average number of pairs of overlapping atoms calculated from the mutual rotation of two (hkl) planes: one plane belonging to the nanoparticle crystal structure, the second one belonging to the matrix crystal structure. In this work, the structure compatibility of photocatalytic ZnS nanoparticles and tetrahedral kaolinite surface was studied. Results were compared with molecular simulations and with the high-resolution transmission electron microscopy analysis performed on a sample of the real ZnS/kaolinite nanocomposite. All three approaches led to identical result: the same preferred crystallographic orientation of ZnS on the tetrahedral surface of kaolinite was found. The method of determining structure compatibility is the fastest of the three approaches used, and thus appears to be very suitable for the purpose of predicting the preferred crystallographic orientation.Web of Science544art. no. 14896

Immunotoxicity of stainless-steel nanoparticles obtained after 3D printing

This study aims to investigate the in vitro effects of nanoparticles (NPs) produced during the selective laser melting (SLM) of 316 L stainless steel metal powder on the immune response in a human blood model. Experimental data did not reveal effect on viability of 316 L NPs for the tested doses. Functional immune assays showed a significant immunosuppressive effect of NPs. There was moderate stimulation (117%) of monocyte phagocytic activity without significant changes in phagocytic activity and respiratory burst of granulocytes. A significant dose-dependent increase in the levels of the pro-inflammatory cytokine TNF-a was found in blood cultures treated with NPs. On the contrary, IL-8 chemokine levels were significantly suppressed. The levels of the pro-inflammatory cytokine IL-6 were reduced by only a single concentration of NPs. These new findings can minimise potential health risks and indicate the need for more research in this area

Simple method for quantification of metal-based particles in biopsy samples of patients with long bone implants – Pilot study

The presence of particles fixed in tissue samples due to implant degradation or disintegration plays an important role in post-operative complications. The ability to determine the size, shape, chemical composition and, above all, the number of these particles can be used in many areas of medicine. This study presents a novel, simple metal-based particle detection method using scanning electron microscopy with energy dispersive spectrometer (SEM-EDS). The presence of metal particles in biopsy specimens from long bone nail-fixated implants (10 patients with titanium steel nails and 10 patients with stainless steel nails) was studied. The samples were analysed using automated area analysis based on image binarization and brightness to 255 grayscale. The results were supplemented with histological data and statistically analysed. The method based on the software used was found to be accurate and easy to use and, thus, appears to be very suitable for particle detection in similar samples.Web of Science103art. no. 10428