Search results

Filters

  • Journals
  • Keywords
  • Date

Search results

Number of results: 17
items per page: 25 50 75
Sort by:

Abstract

This paper describes in detail the phe notypic traits of the newly discovered Leptolyngbya sieminskae sp. n. (Cyanobacteria). The species was found at two islands of the Svalbard archipelago (Spitsbergen and Nordaustlandet) in habitats which differed in humidity, water sources and altitude. The research was conducted at two fjords: on the southern side of Spitsbergen – Hornsund (77 ° N, 015 ° E) and the north−west side of Nordaustlandet – Murchisonfjord (80 ° N, 018 ° E). Although Leptolyngbya sieminskae was found in different latitudes no significant morphological differences were found between the specimens from both sites. The only visible difference is in the thickness of filaments and sheaths.
Go to article

Abstract

As part of the presented work, tests were carried out to check the possibility of replacing of conventional reducers used in the lead pyrometallurgical processes by cheaper, but equally effective substitutes. For research of lead oxide reduction, the following fine-grained carbonaceous materials were used, ie anthracite dust and coal flotation concentrate, as well as traditional used coke breeze for comparison. The obtained test results indicate a similar ability to reduce the lead oxide of all studied carbonaceous materials.
Go to article

Abstract

Ceramic injection moulding and gas pressure infiltration were employed for the manufacturing of alumina/AlSi10Mg composites. Porous ceramic preforms were prepared by mixing alumina powder with a multi-binder system and injection moulding of the powder polymer slurry. Then, the organic part was removed through a combination of solvent and thermal debinding, and the materials were finally sintered at different temperatures. The ceramic preforms manufactured in this way were infiltrated by an AlSi10Mg alloy. The microstructure and properties of the manufactured materials were examined using scanning electron microscopy, mercury porosimetry and bending strength testing. The results of transmission electron microscopy and scanning electron microscopy observations show that the fabricated composite materials are characterised by the percolation type of the microstructure and a lack of unfilled pores with good cohesion at the metal-ceramic interfaces. This is surprising considering that over 30% of the pores are smaller than 1 μm. The results show that the bending strength of the obtained composites decreased with increasing sintering temperature of the porous preforms.
Go to article

Abstract

This article describes the morphological characteristics of the populations of green alga, Tetraspora gelatinosa , growing in the stressful Arctic conditions (77 ° 00’22” N, 015 ° 32’54.33” E). We present the first detailed morphological characteristics of this species from such a high latitude. Populations from both stagnant and flowing waters were studied. Depending on the type of habitat, their mucilaginous colonies (thalli) have different shapes, but the structure, size and the placement of the vegetative cells, akinetes and ameboid forms, as well as the pseudocilia morphology of both populations, were very similar. Literature data on the distribution of T. gelatinosa indicate that it is a cosmopolitan species. Our data are compared with some characteristic features of this species growing in different geographical and climatic zones. No significant differences were found in the morphology of the colonies compared, nor in the location and the inner structure of cells. How − ever, there were slight differences in cell size between the populations from warm and cold zones.
Go to article

Abstract

The aim of the study was to compare cyanobacterial and algal assemblages occurring in ornithocoprophilous habitats formed under the influence of two seabird colonies (mixed colony of piscivorous Uria lomvia and Rissa tridactyla and planktivorous Alle alle) nesting on the southwest side of Hornsund (Spitsbergen). Various influences of the bird colonies (e.g. surface trophy, treading) lead to the formation of ornithogenic habitats with quantitatively and qualitatively diverse cyanobacterial and algal assemblages. Only 6 species common to both habitats were identified, but due to their different proportions the similarity ended there. Cyanobacterial and algal assemblages of both ornithogenic habitats also react rather differently to the intensity of the bird colonies' influence. The assemblages located directly beneath piscivorous bird nests were characterized by a larger number of species, which decreased the farther from the colony it was. Cyanobacterial and algal assemblages located directly next to planktivorous bird nests were species poor, but species richness increased at locations farther from their direct influence. The obtained results confirmed that bird colonies characterized by different diet and behavior influenced the formation of two separate, quantitatively and qualitatively different cyanobacterial and algal assemblages. Species such as Eucapsis sp., Gleocapsopsis sp., Gloeothece sp., Woronichinia sp., Hematococcus sp. were characteristic for algae and cyanobacteria assemblages in the vicinity of piscivorous bird colonies, whereas Aphanocapsa sp., Gloeothece sp., Komvophoron minutum, Pseudanabaena sp., Gloeocystis sp. 2 occurred in the vicinity of planktivorous bird colonies.
Go to article

Abstract

The paper presents the results of a study of cyanobacteria and green algae assemblages occurring in various tundra types determined on the basis of mosses and vascular plants and habitat conditions. The research was carried out during summer in the years 2009–2013 on the north sea−coast of Hornsund fjord (West Spitsbergen, Svalbard Archipelago). 58 sites were studied in various tundra types differing in composition of vascular plants, mosses and in trophy and humidity. 141 cyanobacteria and green algae were noted in the research area in total. Cyanobacteria and green algae flora is a significant element of many tundra types and sometimes even dominate there. Despite its importance, it has not been hitherto taken into account in the description and classification of tundra. The aim of the present study was to demonstrate the legitimacy of using phycoflora in supplementing the descriptions of hitherto described tundra and distinguishing new tundra types. Numeric hierarchical−accumulative classification (MVSP 3.1 software) methods were used to analyze the cyanobacterial and algal assemblages and their co−relations with particular tundra types. The analysis determined dominant and distinctive species in the communities in concordance with ecologically diverse types of tundra. The results show the importance of these organisms in the composition of the vegetation of tundra types and their role in the ecosystems of this part of the Arctic.
Go to article

Abstract

The current study were performed in order to assess the fabrication possibility of the metal-ceramic composites based on nanocrystalline substrates. The influence of the variable time of the high energy ball-milling (10, 30 and 50 h) on the structure, pores morphology and microhardness of Ti/ZrO2 and Ti/Al2O3 compositions was studied. The X-ray diffraction analysis confirmed the composite formation for all milling times and sintering in the case of Ti/ZrO2 system. Decomposition of substrates during milling process of Ti/Al2O3 system was also observed. Additionally, the changes of lattice parameter as a function of milling time were studied. The morphology of powders and the microstructure of the sintered samples were observed by scanning electron microscopy (SEM). Also, analysis of microhardness and pores structure were performed.
Go to article

Abstract

The main purpose of this study was to identify the mineral composition of soil sample taken from the upper layer of topsoil. High absorption of chemical substance is a characteristic for humus-organic layer of topsoil. The source of those substance could be a pollutant emitted to the atmosphere by human activity. The research area includes Upper Silesia region, which is the most industrial region of Poland. In the present study, the phase composition of the top soil separates were analyzed by using X-ray diffraction and Mössbauer spectroscopy. X-ray diffraction analysis revealed the presence of seven mineral phases in the material magnetic separated by lower current (quartz, illite, kaolinite, Fe3+ oxides, hematite, magnetite and pyrite). In case of higher current were identified four phases (quartz, muscovite, kaolinite and K0.94 Na0.06(AlSi3O8)). Mössbauer spectroscopy was used for an extensive analysis of iron-containing phases (pyrrhotite, magnetite, aluminosilicate oxides with Fe3+ and kaolinite/Fe2+ silicate).
Go to article

Abstract

This paper presents the study of microstructure and properties of 8 mol% yttrium stabilized zirconia coating fabricated by Plasma Spray Physical Vapor Deposition technique on commercial pure titanium. The coating was characterized by X-ray diffraction, high resolution scanning electron microscope, profilometer, nanoindentation and nanomachining tests. The X-ray phase analysis exhibit the tetragonal Zr0.935Y0.065O1.968, TiO and α-Ti phases. The Rietveld refinement technique were indicated the changes of crystal structure of the produced coatings. The characteristic structure of columns were observed in High Resolutions Scanning Electron Microscopy. Moreover, the obtained coating had various development of surfaces, thickness was equal to 3.1(1) µm and roughness 0.40(7) µm. Furthermore, the production coatings did not show microcracks, delamination and crumbing. The performed experiment encourages carried out us to tests for osseointegration.
Go to article

Abstract

According to the Polish Ministry of Science and Higher Education and Polish Central Statistical Office the number of students systematically decreases since 2015. This demographic change was a reason to examine students motivation for undertaking their studies in order to improve educational program and to encourage students to peruse higher education. By approaching the subject of “Motivations for Undertaking Special Education Studies in The Opinion of Students at Pedagogical University of Cracow”, the answers were sought to the three following questions: What were the main reasons for choosing studies at Pedagogical University of Cracow? What motivators played a key role for students while selecting field of studies? What student’s personality traits did mainly influence their choice? Research material was collected basing on a self-designed questionnaire. The group of first-year 54 students year were tested, in which 39% didn’t know which specialization they would choose after a one year. The article’s conclusions present key factors motivating students for undertaking Special Education Studies and explain how personality traits influenced their choice.
Go to article

This page uses 'cookies'. Learn more