Search

The aim of the research was to determine the effect of sonochemical treatments on homogenization of powders as well as phase composition and thermal stability of sinters. The compounds were prepared from Eu2O3 and ZrO2 powders, weighed in the mass ratio 1:1. Initially ultrasound treatment was applied. 750-Watt ultrasonic processor VCX-750 equipped with sealed converter VC-334 and horn 630-0219 with the diameter of 13 mm (Sonics & Materials, Inc.) was used as a source of ultrasound. Applied ultrasound frequency was 20 kHz, power density was controlled in the range from 75 W/cm2 to 340 W/cm2. Investigated compounds were synthesized via solid-state reaction (SSR). The Differential Scanning Calorimetry (DSC) was used in order to investigate the effect of sonochemical treatment on the synthesis of prepared mixtures the powders particle size distribution was analyzed. Ultrasound treatment what wasn’t never been reported before.

The aim of the paper is to carry out a comparative engineering-geological study of four different waste landfills using the evaluation criteria for the geological subsoil as a natural sealing barrier. The study evaluates 4 localities (Velké Pavlovice, Kvítkovice, Prakšice and Horní Suchá) using three variants (based on two standards) which approach the geological barrier requirements as a combination of impermeability requirements based on a filtration coefficient limit value. and the required geometry represented by investigation depths. The research was carried out in landfills in Moravia, in the east of the Czech Republic. The study's motivation is to point at the differences in engineering-geological investigations of waste landfills (as for the requirements for impermeable geological subsoil as a natural sealing barrier) when compared with other engineering structures (where the main goal is to evaluate load-bearing capacity and settlement). The purpose of the geological barrier is to prevent the spread of contamination, and the paper shows this can be approached differently, as shown in two different methodologies investigated herein. The first model (Model 1) assumes there is a 3-m-thick subsoil below the landfill's footing bottom, which manifests impermeability characterized by the filtration coefficient K f  ≤ 1.0 * 10 -9  m/s, or a 30-m-thick subsoil of K f  ≤ 1.0 * 10 -8  m/s. The second model (Model 2) assumes a 1-m thick, impermeable subsoil massif of K f  ≤ 1.0 * 10 -9  m/s. We found that none of the landfills in the four selected localities had an impermeable layer in the required depth (a filtration coefficient K f from 1.8 * 10 -9 to 3.9 * 10 -9  m/s), and thus did not comply with the limiting conditions. As a result, an anthropogenic technical barrier had to be installed. An important goal of the study from an environmental point of view was to assess the existence of a suitable geological barrier under the proposed landfills. The most important criterion from this point of view is permeability. An additional technical objective of the project was also the assessment of the possible creation of a technical anthropogenic isolation barrier. In the event that the natural sealing barrier would not be sufficient. This was shown in all solved case studies of engineering geological investigations of waste landfills., (© 2023. The Author(s).)

The alarming increase in the resistance of bacteria to the currently available antibiotics necessitates the development of new effective antimicrobial agents that are active against bacterial pathogens causing major public health problems. For this purpose, our in-house libraries were screened against a wide panel of clinically relevant Gram-positive and Gram-negative bacteria, based on which compound I was selected for further optimization. Synthetic efforts in a group of arylurea derivatives of aryloxy(1-phenylpropyl) alicyclic diamines, followed with an in vitro evaluation of the activity against multidrug-resistant strains identified compound 44 (1-(3-chlorophenyl)-3-(1-{3-phenyl-3-[3-(trifluoromethyl)phenoxy] propyl}piperidin-4-yl)urea). Compound 44 showed antibacterial activity against Gram-positive bacteria including fatal drug-resistant strains i.e., Staphylococcus aureus (methicillin-resistant, MRSA; vancomycin-intermediate, VISA) and Enterococcus faecium (vancomycin-resistant, VREfm) at low concentrations (0.78-3.125 μg/mL) comparable to last resort antibiotics (i.e., vancomycin and linezolid). It is also potent against biofilm-forming S. aureus and Staphylococcus epidermidis (including linezolid-resistant, LRSE) strains, but with no activity against Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa). Compound 44 showed strong bactericidal properties against susceptible and drug-resistant Gram-positive bacteria. Depolarization of the bacterial cytoplasmic membrane induced by compound 44 suggests a dissipation of the bacterial membrane potential as its mechanism of antibacterial action. The high antimicrobial activity of compound 44, along with its selectivity over mammalian cells (lung MCR-5 and skin BJ fibroblast cell lines) and no hemolytic properties toward horse erythrocytes, proposes arylurea derivatives of aryloxy(1-phenylpropyl) alicyclic diamines for development of novel antibacterial agents., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Masson SAS.)

The engineering-geological study deals with the study of significance and relationship of soil and rock workability (factor representing the engineering-geological structure of rock massif) and the remaining earthwork parameters influencing the cost of construction work, such as excavation type and its technology, and excavated cubic volume. The comparative tool was the cost of earthwork as it reflects the real value of the given parameters during the implementation of earthwork. Soil and rock workability is the most important parameter of rock massif engineering-geological structure during any earthwork. The investor pays the contractor for earthwork based on workability classes which have their accounting value expressed as a volume unit of earthwork per particular project. The research results arise from a comparison of 6 sewer system construction project case studies in the north-east of the Czech Republic. The research shows that the most important factor during the implementation of earthwork is the specific engineering-geological structure (52%), which reflects in the parameter of soil and rock workability classes, using which all earthwork is priced. The second most important factor (33%) is the type of excavation and its technology. The least important is the excavated cubic volume (15%), which means the overall cubic volume of earthwork. The results were obtained within three evaluation approaches, where the comparison unit was one cubic meter of excavated volume during earthwork., (© 2023. The Author(s).)

Total hip arthroplasty with metal-on-metal bearing is associated with specific complications: local delayed hypersensitivity reaction (ALVAL) to metal particles, osteolysis and the development of pseudotumors. This process results from the low resistance of the metal bearing to abrasion and corrosion, which causes the release of metal ions into the surrounding tissues. This paper presents the case of a 54-year-old man who required revision surgery due to aseptic loosening of the endoprosthesis with a ceramic (TiN)-on-metal bearing. The removed implants were subjected to material analysis. Mean chemical analysis revealed that the main component of the residue samples was titanium, which constituted 65% of the sample weight, followed by calcium (16%), phosphorus (11%) and aluminum (3.8%). The fissures on the insert were a result of trauma caused by the head, with both elements matching in terms of visible damage. More than 50% of the surface of the head had been damaged due to abrasive wear. The transitional area between the normal and completely delaminated TiN coating shows uneven abrasion, a gradual decrease in coating thickness. In conclusion, the use of endoprosthesis heads with TiN ceramic coating involves very low polyethylene wear. The low resistance of TiN ceramic coating to trauma and the fragility of this coating prevent the use of TiN-coated heads in combination with any non-polyethylene hip endoprosthesis inserts.

The aim of the article is to compare two classifications systems of engineering-geological environment sustainability in terms of its permeability evaluated on the basis of permeability coefficient. The first evaluated classification assumes a permeable environment to be a positive characteristic in the engineering-geological assessment, while the other considers an impermeable environment as favourable. The four fine-grained soil materials were selected, as they had very similar, almost identical grains-size distribution, but different microstructure characterized by grains sphericity, angularity, and roughness. At the same time, the influence of changes in the density of soil materials (density index 10%, 30%, 60%, 90%) was analysed. Permeability coefficient was determined using six methods (empirical formulae, laboratory and microscopic analysis). The laboratory method falling head test (FHT) was taken as a reference test that reflected the actual water flow through the soil. It was found that with an increase in grain angularity and roughness (and a decrease in sphericity), the permeability coefficient was decreasing and this trend culminated along with gradual compaction. Moreover, the research shows that unsuitable methods may classify soil materials into wrong engineering-geological permeability classes, which may have negative consequences during engineering-geological or geotechnical assessment and cause subsequent problems in foundation engineering.

The aim of this research was to produce a new methodology for a special river bottom hazard mapping for the stability purposes of the biggest Polish water power plant: Włocławek. During the operation period of the water power plant, an engineering-geological issue in the form of pothole formation on the Wisła River bed in the gravel-sand alluvium was observed. This was caused by increased fluvial erosion resulting from a reduced water level behind the power plant, along with frequent changes in the water flow rates and water levels caused by the varying technological and economic operation needs of the power plant. Data for the research were obtained by way of a 4-year geodetic/bathymetric monitoring of the river bed implemented using integrated GNSS (Global Navigation Satellite System), RTS (Robotized Total Station) and SBES (Single Beam Echo Sounder) methods. The result is a customized river bottom hazard map which takes into account a high, medium, and low risk levels of the potholes for the water power plant structure. This map was used to redevelop the river bed by filling. The findings show that high hazard is related to 5% of potholes (capacity of 4308 m 3 ), medium with 38% of potholes (capacity of 36,455 m 3 ), and low hazard with 57% of potholes (capacity of 54,396 m 3 ). Since the construction of the dam, changes due to erosion identified by the monitoring have concerned approximately 405,252 m 3 of the bottom, which corresponds to 130 Olympic-size pools. This implies enormous changes, while a possible solution could be the construction of additional cascades on the Wisła River.

This paper deals with the engineering-geological investigation of uncontrolled dumpsites that are abundant in post-communist countries. The sites may be redeveloped in an optimal manner by using the applied methodology of engineering-geological investigations. The research tool is a case study dealing with hazardous uncontrolled dumpsites chemically contaminated by various substances, particularly carcinogenic chromium. The dumpsite is located in the alluvial sediments of an oxbow lake of the Nitra River in the Slovak Republic. The hazard is seen in the fact that the alluvial sediments are permeable and thus the contamination may spread easily. At the same time, it is located near a river, which makes the hazard greater. Apart from the risk of contamination, another risk is related to the methane generated by the dumpsite and thus the risk of self-ignition. In order to identify the uncontrolled dumpsite body, the research was grounded in the different physical properties of the diverse geological environments. Quasi-homogenous blocks of the dumpsite body and its alluvial surroundings were well identified by using the combined three geophysical methods, namely dipole electromagnetic profiling (DEMP), electrical resistance tomography (ERT) and spontaneous polarization (SP). In order to eliminate the risk of contamination spread, redevelopment measures for the uncontrolled dumpsite in the form of sealing walls and surface sealing foil were proposed. A system of methane drainage boreholes was proposed to eliminate the risk of self-ignition. The methodology in this case study is well applicable for other uncontrolled dumpsites, which is an important outcome of the study.