Microbial diversity of internal environment of Johann Gregor Mendel Station, Antarctica

During January and February 2011 two sets of microbiological samples were collected inside the main building of Johann Gregor Mendel station located at the James Ross Island near the coast of Antarctica. The aim was to examine the changes of microbial profile of the antarctic station environment. The first set of samples was collected from the station environment before the staff entry, i.e. after 10 months of quiescent state when nobody was present at the station. The second set of samples was collected from the same places before the Antarctic expedition staff left the station after 45 days of the stay. The cultivation of samples was focused on mesophilic bacteria. Twenty-three strains were obtained from the Set No. 1 and 27 strains were obtained from the Set No. 2. However, 8 strains from each set were not reliably identified by mass spectrometry. Altogether 13 strains of Gram-positive bacteria were identified in the Set. No. 1, while only 7 in the Set No. 2. Contrastingly, Gram-negative bacteria were much more abundant in the Set No. 2 (12 strains) than in the Set No. 1 (2 strains). Bacillus sp. was the most common Gram-positive strain (9 isolations from the first set, 2 isolations from the second set). Pantoea agglomerans was the most common Gram-negative strain (2 isolations from the first set, 7 isolations from the second set). The first experience with the microbial profile of the research station showed that we were able to detect mainly bacteria commonly present in the outer environment that could survive under extreme conditions. We did not isolate any microbes related to human colonisation except of enterococci and Escherichia vulneris. For further investigation of the station environment, it will be necessary to choose alternative way of collection and storage of samples to ensure survival of all present bacteria

THE EFFECT OF DIFFERENT FORMS OF OXYGEN ON PROPERTIES OF BETA TITANIUM ALLOYS

The beta-titanium alloys are widely used in many applications (medicine, aerospace industry etc.) due to their superior properties, such as corrosion resistance, biocompatibility and high strength to weight ratio. One of the ways how to increase the strength of those alloys is the addition of oxygen. The oxygen can be present in various forms in the alloy – in a solid solution or in the form of oxides. In this work, the effect of two forms of oxygen (i.e., solid solution and dispersion particles) was studied. Two alloys, one arc melted with different oxygen additions and one prepared via powder metallurgy where the titanium powder was oxidized, were prepared. The microstructure and mechanical properties were studied. A significant increase in strength with increasing the oxygen content in the solid solution has been observed. However, the powder oxidation has almost no effect on a tensile strength probably due to quite large interparticle distances between titanium oxide particles

Biomechanical study of the bone tissue with dental implants interaction

The article deals with the stress-strain analysis of human mandible in the physiological state and after the dental implant application. The evaluation is focused on assessing of the cancellous bone tissue modeling-level. Three cancellous bone model-types are assessed: Non-trabecular model with homogenous isotropic material, nontrabecular model with inhomogeneous material obtained from computer tomography data using CT Data Analysis software, and trabecular model built from mandible section image. Computational modeling was chosen as the most suitable solution method and the solution on two-dimensional level was carried out. The results show that strain is more preferable value than stress in case of evaluation of mechanical response in cancellous bone. The non-trabecular model with CT-obtained material model is not acceptable for stress-strain analysis of the cancellous bone for singularities occurring on interfaces of regions with different values of modulus of elasticity