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  • Author: W. Janusz x
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The study of the properties of the hydroxyapatite/electrolyte interface

The study of the properties of the hydroxyapatite/electrolyte interface

A physicochemical property of hydroxyapatite (HAP) [Ca10(OH)2(PO4)6] surface was studied and parameters of electrical double layer of the hydroxyapatite/NaCl solution system were described. The study sample of hydroxyapatite was synthesized. The structure of the hydroxyapatite was confirmed using X-ray diffraction (XRD), its particle size by PCS (photon correlation spectroscopy) AFM and SCM microscope and its surface properties by means of adsorption-desorption of nitrogen (ASAP), Raman spectra,. Then the point of zero charge and the isoelectirc point were measured.

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INFLUENCE OF THE CUTTING EDGE ANGLE OF THE GRANULATOR ON THE EXTRUSION PROCESS AND PELLETS PROPERTIES

Abstract

This paper is concerned with experimental tests of the process of extrusion with hot granulating of polymer, conducted to determine the influence of a change in the value of the cutting edge angle of a granulator knife on the basic parameters of the obtained pellets and on the process of extrusion with granulation. The available literature does not raise this issue. In the present study, the process of extrusion with hot granulation was studied with the use of low-density polyethylene.

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On the characteristic and stability of iron diet supplements

Abstract

The iron diet supplements: AproFER 1000 and AproTHEM were subjected to various chemical, microbial and magnetic analysis. The microbial analysis revealed no presence of pathogenic bacteria in the studied products. No significant changes in iron content or forms (bivalent/trivalent) were observed in EPR analysis of supplements stored at different conditions for a long period of time. The chemical and magnetic analysis showed that both AproFER 1000 and AproTHEM contain a high concentration of bivalent iron so they can be used as an iron diet supplements.

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Employers Expectations Vis-à-vis Graduates of Faculties of Economics. Results of a Direct Study

Abstract

This paper presents employers’ opinions concerning competencies they expect of graduates of Faculties of Economics with elements of environmental protection. In order to provide empirical input, we conducted a questionnaire-based study among 200 top managers of (mostly) businesses located in the Lodz region (voivodeship), including 194 enterprises and 6 entities do not involved in business but whose activities are, directly or indirectly, linked with environmental protection. The findings of our study demonstrate that while both soft and professional competencies acquired in the course of university studies are important to employers, the respondents valued soft competencies more. They found foreign languages to be the most important, although surprisingly they also attached high importance to a good command of Polish. When assessing university curricula, employers indicated that general courses, the foundations of a university education, remain important as a basis to improve the professional skills of university graduates and to reinforce their position in the labour market.

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Directional measures of postural sway as predictors of balance instability and accidental falls

Abstract

Despite the obvious advantages and popularity of static posturography, universal standards for posturographic tests have not been developed thus far. Most of the center-of-foot pressure (COP) indices are strongly dependent on an individual experimental design, and are susceptible to distortions, which makes results of their analysis incomparable. In this research, we present a novel approach to the analysis of the COP trajectory based on the directional features of postural sway. Our novel output measures: the sway directional indices (DI) and sway vector (SV) were applied to assess the postural stability in the group of young able-bodied subjects. Towards this aim, the COP trajectories were recorded in 100 students standing still for 60 s, with eyes open (EO) and then, with eyes closed (EC). Each record was subdivided then into 20, 30 and 60 s samples. Interclass correlation coefficients were calculated from the samples. The controlled variables (visual conditions) uniquely affected the output measures, but only in case of proper signal pretreatment (low-pass filtering). In filtering below 6 Hz, the DI and SV provided a unique set of descriptors for postural control. Both sway measures were highly independent of the trial length and the sampling frequency, and were unaffected by the sampling noise. Directional indices of COP filtered at 6 Hz showed high to very high reliability, with ICC range of 0.7-0.9. Results of a single 60 s trial are sufficient to reach acceptable reliability for both DI and SV. In conclusion, the directional sway measures may be recommended as the primary standard in static posturography.

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Temperature study of magnetic resonance spectra of co-modified (Co,N)-TiO2 nanocomposites

Abstract

The (nCo,N)-TiO2 (n = 1, 5 and 10 wt.% of Co) nanocomposites were investigated by magnetic resonance spectroscopy in 4 K to 290 K range. Analyses of ferromagnetic/electron paramagnetic resonance (FMR/EPR) spectra in terms of four Callen lineshape components revealed the existence of two types of magnetic centers, one derived from metallic cobalt nanoparticles in superparamagnetic (SPM) phase and the other from cobalt clusters in the TiO2 lattice. Additionally, at low temperature the EPR spectrum arising from Ti3+ ions was also registered. Both relaxations of the Landau-Lifshitz type and the Bloch-Bloembergen type played an important role at high temperature in determining the linewidths and the latter relaxation was prevailing at low temperature. Analysis of the integrated intensity showed that the SPM signal is due to small size FM cobalt nanoparticles while the paramagnetic signal from Co clusters originates from those nanoparticles in which the concentration of magnetic polarons is below the percolation threshold.

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Magnetic resonance study of co-modified (Co,N)-TiO2 nanocomposites

Abstract

Three nCo,N-TiO2 nanocomposites (where cobalt concentration index n = 1, 5 and 10 wt %) were prepared and investigated by magnetic resonance spectroscopy at room temperature. Ferromagnetic resonance (FMR) lines of magnetic cobalt agglomerated nanoparticle were dominant in all registered spectra. The relaxation processes and magnetic anisotropy of the investigated spin system essentially depended on the concentration of cobalt ions. It is suggested that the samples contained two magnetic types of sublattices forming a strongly correlated spin system. It is suggested that the existence of strongly correlated magnetic system has an essential influence of the photocatalytic properties of the studied nanocomposites.

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Geodetic and Geodynamic Studies at Department of Geodesy and Geodetic Astronomy Wut

Abstract

The article presents current issues and research work conducted in the Department of Geodesy and Geodetic Astronomy at the Faculty of Geodesy and Cartography at Warsaw University of Technology. It contains the most important directions of research in the fields of physical geodesy, satellite measurement techniques, GNSS meteorology, geodynamic studies, electronic measurement techniques and terrain information systems.

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