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  • Author: Łukasz Kaczmarek x
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Abstract

Localised landslide activity has been observed in the area of the plateau slope analysed, in the vicinity of the planned Warsaw Southern Ring Road. Using calculation models quantitative and qualitative evaluations of the impact of natural and anthropogenic load factors on slope stability (and hence, safety) are made. The present paper defines six stages of slope stability analysis, leading to an indication of optimum slope design in relation to the development planned. The proposed procedure produces a ranking of factors that affect slope stability. In the engineering geological conditions under consideration, the greatest factors impacting degradation and failure of slope stability are changes in soil strength due to local, periodic yielding and the presence of dynamic loads generated by intensification of road traffic. Calculation models were used to assess the impact of destabilisation factors and to obtain mutual equivalence with 3D-visualisation relations. Based on this methodology, various scenarios dedicated to specific engineering geological conditions can be developed and rapid stability evaluations of changing slope loads can be performed.

First records of Isohypsibius pushkini Tumanov, 2003 (Tardigrada, Eutardigrada, Hypsibiidae) from Poland

First records of Isohypsibius pushkini from small ponds in western Poland are described. So far, these are the only records of this species apart from its type locality in Russia. We present some remarks on the ecology of the species, as well. Moreover, we present the first ever microphotographs of I. pushkini.

Abstract

The study employs numerical calculations in the characterization of reservoir sandstone samples based on high-resolution X-ray computed microtomography. The major goals were to determine porosity through pore size distribution, permeability characterization through pressure field, and structure impact on rock strength by simulation of a uniaxial compression test. Two Miocene samples were taken from well S-3, located in the eastern part of the Carpathian Foredeep. Due to the relation between sample size and image resolution, two X-ray irradiation series with two different sample sizes were performed. In the first approach, the voxel side was 27 μm and in the second it was up to 2 μm. Two samples from different depths have been studied here. Sample 1 has petrophysical features of conventional reservoir deposits, in contrast to sample 2. The approximate grain size of sample 1 is in the range 0.1-1.0 mm, whereas for sample 2 it is 0.01-0.1 mm with clear sedimentation lamination and heterogenic structure. The porosity, as determined by μCT, of sample 1 is twice (10.3%) that of sample 2 (5.3%). The equivalent diameter of a majority of pores is less than 0.027 mm and their pore size distribution is unimodal right-hand asymmetrical in the case of both samples. In relation to numerical permeability tests, the flow paths are in the few privileged directions where the pressure is uniformly decreasing. Nevertheless, there are visible connections in sample 1, as is confirmed by the homogenous distribution of particles in the pore space of the sample and demonstrated in the particle flow simulations. The estimated permeability of the first sample is approximately four times higher than that of the second one. The uniaxial compression test demonstrated the huge impact of even minimal heterogeneity of samples in terms of micropores: 4-5 times loss of strength compared to the undisturbed sample. The procedure presented shows the promising combination of microstructural analysis and numerical simulations. More specific calculations of lab tests with analysis of variable boundary conditions should be performed in the future.

Abstract

The study concerns soil creep deformation in multistage triaxial stress tests under drained conditions. High resolution X-ray computed microtomography (XμCT) was involved in structure recognition before and after triaxial tests. Undisturbed Neogene clay samples, which are widespread in central Poland, were used in this study. XμCT was used to identify representative sample series and informed the detection and rejection of unreliable ones. Maximum deviatoric stress for in situ stress confining condition was equal 95.1 kPa. This result helped in the design of further multistage investigations. The study identified the rheological strain course, which can be broken down into three characterizations: decreasing creep strain rate, transitional constant creep velocity, and accelerating creep deformation. The study found that due to multistage creep loading, the samples were strengthened. Furthermore, there is a visibly “brittle” character of failure, which may be the consequence of the microstructure transformation as a function of time as well as collapse of voids. Due to the glacial tectonic history of the analyzed samples, the reactivation of microcracks might also serve as an explanation. The number of the various sizes of shear planes after failure is confirmed by XμCT overexposure.

Abstract

The aim of this study was the evaluation of the relationship between the presence of tardigrades and various levels of sewage pollution in different tanks of a wastewater treatment plant. The study was carried out in the wastewater treatment plant located near Poznań (Poland) during one research season. The study was conducted in a system consisting of three bioreactor tanks and a secondary clarifier tank, sampled at regular time periods. The presence of one tardigrade species, Thulinius ruffoi, was recorded in the samples. The tardigrades occurred in highest abundance in the tanks containing wastewater with a higher nutrient load. Thulinius ruffoi was mainly present in well-oxygenated activated sludge and its abundance was subject to seasonal fluctuations; however, its preference for more polluted tanks seems to be consistent across the year. Although more detailed experimental study is needed to support the observations, our data indicate that T. ruffoi has a high potential to be used as a bioindicator of nutrient load changes.

Abstract

The dynamic development of the world economy entails an increasing exchange of goods and population. This means that we are globally struggling with increasing levels of nosocomial infections. The increasing use of antimicrobial agents triggers the microorganisms’ immune system, which in turn contributes to the increasing amount of antibiotic-resistant microorganisms, making it necessary to control the development of unwanted microorganisms, including bacteria, especially those carried on the body and clothing.

Currently, there is no unique method to combat the multiplication of microorganisms and eliminate threats to human health and life. For this reason, this article describes the possibilities of using graphene materials as a potential additive materials in fiber finishes as an antibacterial aspect in various areas of life. However, the literature does not explain the mechanisms behind the antibacterial properties of graphene, strongly limiting its textile application. The research is conducted using molecular dynamic simulations of interaction between graphene materials and murein. The obtained results suggest the electrostatic mechanism of blocking the growth and division of bacteria. Due to the physical interaction, bacterial cell becomes “trapped” without changing its growth parameters. This may lead to an increase of internal cell pressure, rupture of its wall and consequently its death.

Abstract

The lung cancer is often associated with the development of pleural effusion. Neutrophils are the most numerous population of immune system cells which are an essential component of tumor leukocyte infiltration. These cells are engaged in the development and maintenance of the inflammation. It is indicated that neutrophils support the development of cancer. The aim of the study was the evaluation of neutrophils, regarding their presence and activity in pleural effusions. This was achieved by assessing of molecular structures, which are used by neutrophils in chemotaxis and phagocytosis. 60 pleural effusions and 34 peripheral blood samples received from patients and 15 peripheral blood samples from the control group were analyzed. Expression of CD11a, CD11b, CD11c, CD18 and CD62L molecules with use flow cytometry was evaluated. The concentration of the neutrophil elastase in pleural effusions were measured with use ELISA test. The number of neutrophils in the peripheral blood of patients with pleural effusion was lower than that observed in the control group. Neutrophils present in pleural effusions were characterized by an increased ability to chemotaxis and secrete significant amounts of neutrophil elastase. Neutrophils recruited into the pleura during the formation of the effusion are an essential element of the developing inflammatory reaction in this environment. The presence of neutrophils in pleural effusion may promote its further formation and support the development of cancer.