Tomasz Płociński

Unique surface and internal structure of struvite crystals formed by Proteus mirabilis

Crystallization of struvite from artificial urine in the presence of Proteus mirabilis microorganisms depends strongly on pH value. At small value of pH, struvite yields crystals of coffin-like habit with very specific structure. The analysis using scanning electron microscopy shows that the crystals possess well-defined faces, but higher magnifications show very specific structuration as if the crystals were built from small three-dimensional subunits. The possible role of microorganisms in the formation of such a structuration is analyzed. At higher pH value, the crystals exhibit dendritic growth with main trunk and branches. Although the formation mechanism of the specific structuration as well as dendritic structures is unknown, the nature of forces for such an alignment is analyzed. The revealed porous internal structure of struvite is also analyzed. The investigations provide evidence for the importance of biological regulation in crystallization process.

Hybrid a-CNH+TiO2+TiN-type surface layers produced on NiTi shape memory alloy for cardiovascular applications

AIM The goal was to improve the properties of NiTi shape memory alloy to make it suitable for cardiac applications. For this purpose, a hybrid a-CNH+TiO2+TiN-type surface layer was produced on NiTi alloy and characterized. MATERIALS & METHODS The NiTi alloy subjected to hybrid process combining low-temperature oxynitriding under glow discharge conditions and radio frequency chemical vapor deposition process was examined for microstructure, surface topography, corrosion resistance, wettability and surface-free energy, Ni ion release and platelets adhesion, aggregation and activation. RESULTS The hybrid surface layers showed slightly increased surface roughness, better corrosion resistance, a more hydrophobic nature, decreased surface free energy, smaller release of nickel ions and reduced platelets activation. CONCLUSION The produced layers could expand the range of NiTi medical applications.

Multigene Assessment of Biodiversity of Diatom(Bacillariophyceae) Assemblages from the Littoral Zone of the Bohai and Yellow Seas in Yantai Region of Northeast China with some Remarks on Ubiquitous Taxa

ABSTRACT Witkowski, A.; Li, C. L.; Zg[lstrok]obicka, I.; Yu, S. X.; Ashworth, M.; Dąbek, P.; Qin, S.; Tang, C.; Krzywda, M.; Ruppel, M.; Theriot, E. C.; Jansen, R. K.; Car, A.; Płociński, T.; Wang, Y. C.; Sabir, J. S. M.; Daniszewska-Kowalczyk, G.; Kierzek, A., and Hajrah, N. H., 2016. Multigene assessment of biodiversity of diatom (Bacillariophyceae) assemblages from the littoral zone of the Bohai and Yellow Seas in Yantai region of Northeast China with some remarks on ubiquitous taxa. Diatoms are important contributors to the benthic microeukaryote flora. This manuscript lays the foundation for future metagenomic and environmental sequencing projects off coastal China by curating diatom DNA sequences from the Yantai region of the Bohai and Yellow Seas (Northeast China). These studies are based on cultures established from samples collected in different seasons from marine littoral and supralittoral zones in 2013 and 2014. Thirty-six diatom strains were cultured successfully and identification of these clones was determined by light and scanning electron microscopy(LM and SEM) and DNA sequencing of the nuclear-encoded small subunit ribosomal RNA (SSU)and chloroplast-encoded rbcL and psbC genes. The strains primarily represent raphid pennate genera, such as Amphora, Amphora (Oxyamphora), Caloneis, Diploneis, Halamphora, Navicula, Nitzschia, Parlibellus, Pleurosigma, Surirella and Tryblionella. When the DNA markers from these strains were analysed in a multi-gene phylogeny, we found that some clones-particularly within the genera Amphora, Navicula and Nitzschia—show greater than expected genetic diversity despite their very similar morphology and morphometrics. We also compared the molecular and morphological identities of several seemingly ubiquitous marine littoral taxa in the genera Amphora and Nitzschia from the Indian Ocean and Atlantic Ocean, the Red Sea and Adriatic Sea to their Yellow Sea counterparts.

Structure and corrosion resistance of titanium oxide layers produced on NiTi alloy in low-temperature plasma

Abstract The paper presents comparative results of NiTi corrosion resistance tests of the alloy in initial state and after oxidizing and oxynitriding in low temperature plasma. These processes allow obtaining TiO2 or composite TiO2 + TiN layers with a titanium nitride (TiN) interlayer. Corrosion resistance tests of diffusion layers produced on NiTi were carried out via electrochemical impedance spectroscopy and the potentiodynamic method in Ringers solution at 37 °C. The results were complemented with analysis of the alloys structure, surface topography, and elemental distribution in the layers. The results showed an increase in corrosion resistance of NiTi alloy both after glow-discharge oxidation and oxynitriding. Significant shortening of the passive range of oxynitrided layers may result both from differences in surface topography and the thickness of the oxide layers.

Description of a new marine diatom, Cocconeis caulerpacola sp. nov. (Bacillariophyceae), epiphytic on invasive Caulerpa species

A new species of Cocconeis has been found growing on thalli of the invasive green alga Caulerpa taxifolia collected from the Croatian Adriatic Sea (Bay of Stari Grad, the Island of Hvar, Central Adriatic, Croatia), the coasts of the Mediterranean (Saint Raphaël, west of Cannes, France) and the eastern coast of Australia (Moreton Bay, southeast Queensland). Additionally, it was observed on samples of Caulerpa racemosa, another invasive alga in the Mediterranean. Preserved thalli of Caulerpa and cleaned material of the new diatom were studied by light and electron microscopy (SEM and TEM). The morphology and fine structure of the new marine epiphytic diatom, for which we propose the name Cocconeis caulerpacola Witkowski, Car & Dobosz, was determined, including the internal and external structure of the raphe and sternum valve, and the cingulum. Comparison between the new species and three closely related species, C. borbonica, C. diruptoides and C. pseudodiruptoides, was made using material from our samples, as well as material from Vis (Adriatic Sea) obtained from the Hustedt collection. Surprisingly, C. caulerpacola is able to colonize Caulerpa taxifolia in very high abundance, but its occurrence seems to be strongly patchy. Indeed, it seems that C. taxifolia is a suitable host for epiphytic diatoms, in particular this tiny Cocconeis, despite its reputation as a ‘killer seaweed’. Cocconeis caulerpacola was observed on Caulerpa species in varying abundance over a wide geographical range.

Cs-corrected scanning transmission electron microscope investigations of an ODS ferritic steel for fusion applications

Over the last few years, oxide dispersion strengthened (ODS) ferritic steels have emerged as one of the major materials for fusion reactors. Despite the progress made in their technology, currently available properties still do not meet all the expectations. As a result these steels remain the subject of extensive research, recently centred on a possible improvement due to their nanometric engineering. In particular, technologies are developed for grain size refinement down to nanometres and strengthening by nanooxides. This, in turn, calls for nanoscale investigations of the microstructures, which can be efficiently carried out only with the use of high-resolution transmission electron microscopy and spectroscopy. The present paper illustrates the results of investigations of a model alloy of ODS steel using a recent high-resolution scanning transmission electron microscope equipped with a spherical abberation Cs-correction system, energy-dispersive x-ray spectroscopy and electron energy loss spectroscopy spectrometers. It allows bright field on transmitted electron imaging and secondary electron imaging, as well as high-angle annular dark field imaging, the so-called Z-contrast imaging. The results obtained in dark field prove that modern microscopy techniques are a necessity to provide new information on the nanostructure of the ODS steels relevant to the understanding and shaping of their properties.

Structure and properties of composite surface layers produced on NiTi shape memory alloy by a hybrid method

AbstractA hybrid process that combines oxidation under glow-discharge conditions with ion beam-assisted deposition (IBAD) has been applied to mechanically polished NiTi shape memory alloy in order to produce composite surface layers consisting of a TiO2 layer and an external carbon coating with an addition of silver. The produced surface layers a-C(Ag) + TiO2 type have shown increased surface roughness, improved corrosion resistance, altered wettability, and surface free energy, as well as reduced platelet adhesion, aggregation, and activation in comparison to NiTi alloy in initial state. Such characteristics can be of great benefit for cardiac applications.

Effect of Heat Treatment on Formation of Al-Al3Ni Hypereutectic Alloys

The paper deals with the mechanism of eutectic formation in a nickel coated aluminium system after heat treatment. The initial coating was produced from a nickel powder by means of high velocity oxyfuel (HVOF) spraying onto an aluminium sheet substrate. Specimens for investigations were manufactured immediately after the spraying. The specimens were heat-treated using a differential thermal analysis (DTA) apparatus up to the temperature of 700 or 900 °C and then cooled down to room temperature in argon atmosphere with a constant heating and cooling rate of 5 °C / min, under which Al-Al3Ni + Al3Ni hypereutectic alloys were formed within the initial substrate. Two different alloy microstructures consisting of intermetallic layers and coarse eutectic or an ultrafine well-dispersed eutectic were formed. Formation processes and resulting microstructures were studied by means of DTA, metallography, scanning electron microscopy, focused ion beam, energy dispersive microanalysis and image analysis techniques.