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Open access

E. Kowalczyk, E. Patyra, A. Grelik and K. Kwiatek

Abstract

A high performance liquid chromatography combined with fluorescence detection (HPLC-FLD) method was developed for determination of five ergot alkaloids (EA): ergometrine, ergotamine, ergocornine, ergocrypine and ergocristine in animal feedingstuffs. The method was based on the application of QuEChERS salts for extraction and modified QuEChERS dispersive SPE for the cleanup step. Alkaloids separation was performed on a C18, 250 mm x 4.6 mm, 5 μm column with the mobile phase containing ammonium carbonate and acetonitrile. The excitation and emission wavelengths were 330 and 420 nm respectively. The method was validated according to the Commission Decision 2002/657/EC and all parameters are in agreement with the requirements of the Decision. Linearity was determined for the concentration range of 25-400 μg/kg. The coefficient of determination (R2) for all curves was from 0.985 to 0.996. The limit of detection (LOD) was in the range 3.23 to 6.53 μg/kg and the limit of quantification (LOQ) from 11.78 to 13.06 μg/kg. The decision limit (CCα) ranged from 29.56 to 43.08 μg/kg and detection capability (CCβ) from 40.65 to 51.01 μg/kg. The highest coefficient of variation (CV) for repeatability was 14.3% and for reproducibility 15.4%.

Open access

W. Bielski, P. Kowalczyk, E. Czerwosz, A. Idzik and J. Rymarczyk

Abstract

In this paper we propose a model of electric current flow through one-dimensional palladium-carbon nanostructure (nanowire) and compare the results of numerical computations with the experimental data. We focus on two aspects: 1) calculation of the current flow through the nanowire model, 2) determination of the macroscopic parameters in the nanocomposite in our model. Because of a complex micro-geometry of a nanowire, we apply the homogenization method to perform the numerical computations.

Open access

E. Dembicki, M. Kowalczyk and P. Gotteland

Abstract

The use of shredded tyre in civil engineering applications is a significant potential end use market. The reuse of tyre chips may not only address growing environmental and economic concerns, but also help to solve geotechnical problems associated with low shear strength. The purpose of this paper is to investigate the properties of tyre chips and tyre chips - sand mixture, and to find the mixture with the highest shear strength. In this study, an experimental testing program was undertaken using a large - scale triaxial apparatus with the goal of evaluating the optimum percentage of tyre chips in sand. The effects on shear strength of varying percentage of tyre chips and varying confining pressure were studied. Tyre chips content was suspected to have influence on stress - strain and volumetric strain behaviour of the mixture. Some tests were conducted to check the influence of number of used membranes, of saturation and compaction, on sample properties.

Open access

W. Wieteska-Skrzeczyńska, K. Grzelkowska-Kowalczyk and E. Rejmak

Growth factor and cytokine interactions in myogenesis. Part II. Expression of IGF binding proteins and protein kinases essential for myogenesis in mouse C2C12 myogenic cells exposed to TNF-α and IFN-γ

The aim of the study was to examine potential interactions among IGF-I and proinflammatory cytokines, TNF-α and IFN-γ, in the regulation of local IGF-I bioavailability and cellular proteins mediating myogenic signals. We investigated levels of IGFBP-4, -5, -6, protein kinase Czeta (PKCζ), p38 and extracellular signal-regulated kinase (ERK1/2) in differentiating mouse C2C12 myoblasts. IGF-I significantly stimulated expression of IGFBP-5. TNF-α and IFN-γ attenuated the expression of IGFBP-4 and -6 under basal conditions and in the presence of IGF-I, and inhibited IGF-I-induced IGFBP-5 expression during 5-day myogenesis. TNF-α and IFN-γ markedly attenuated p38 expression in the presence of IGF-I on the 5th day of myogenesis. When combined with IGF-I the cytokines exerted opposite effects on the PKCζ level, i.e. TNF-α caused an increase, whereas IFN-γ reduced the cellular content of this kinase. Exposition of C2C12 myoblasts to IGF-I or cytokines led to the stimulation of ERK1/2 phosphorylation; however, both TNF-α and IFN-γ exerted an inhibitory effect on the activation of ERK1/2 in myoblasts cultured in the presence of IGF-I. We concluded as follows: i) TNF-α and IFN-γ present in the extracellular environment of differentiating C2C12 myoblasts can alter the local bioavailability of IGF-I by inhibiting the expression of IGFBP-4, -5, and -6, ii) the decrease in p38 expression and ERK1/2 phosphorylation in C2C12 myoblasts exposed to cytokines can lead to disturbances in IGF-I-regulated myogenesis.

Open access

E. Patyra, E. Kowalczyk, A. Grelik, M. Przeniosło-Siwczyńska and K. Kwiatek

Abstract

A liquid chromatography – diode array detector (HPLC-DAD) procedure has been developed for the determination of oxytetracycline (OTC), tetracycline (TC), chlorotetracycline (CTC), doxycycline (DC), enrofloxacin (ENR), ciprofloxacin (CIP), sarafloxacin (SAR) and flumequine (FLU) residues in animal drinking water. This method was applied to animal drinking water. Solid-phase extraction (SPE) clean-up on an Oasis HLB cartridge allowed an extract suitable for liquid chromatographic analysis to be obtained. Chromatographic separation was carried out on a C18 analytical column, using gradient elution with 0.1% trifluoroacetic acid – acetonitrile – methanol at 30°C. The flow-rate was 0.7 mL/min and the eluate was analysed at 330 nm. The whole procedure was evaluated according to the requirements of the Commission Decision 2002/657/EC, determining specificity, decision limit (CCα), detection capacity (CCβ), limit of detection (LOD), limit of quantification (LOQ), precision and accuracy during validation of the method. The recoveries of TCs and FQs from spiked samples at the levels of 10, 100 and 1000 μg/L were higher than 82%. The developed method based on HPLC-DAD has been applied for the determination of four tetracyclines and four fluoroquinolones in animal drinking water samples.

Open access

L. Kowalczyk, H. Goszczynska, E. Zalewska, A. Bajera and L. Krolicki

Abstract

This work was performed as part of a larger research concerning the feasibility of improving the localization of epileptic foci, as compared to the standard SPECT examination, by applying the technique of EEG mapping. The presented study extends our previous work on the development of a method for superposition of SPECT images and EEG 3D maps when these two examinations are performed simultaneously. Due to the lack of anatomical data in SPECT images it is a much more difficult task than in the case of MRI/EEG study where electrodes are visible in morphological images. Using the appropriate dose of radioisotope we mark five base electrodes to make them visible in the SPECT image and then approximate the coordinates of the remaining electrodes using properties of the 10-20 electrode placement system and the proposed nine-ellipses model. This allows computing a sequence of 3D EEG maps spanning on all electrodes. It happens, however, that not all five base electrodes can be reliably identified in SPECT data. The aim of the current study was to develop a method for determining the coordinates of base electrode(s) missing in the SPECT image. The algorithm for coordinates approximation has been developed and was tested on data collected for three subjects with all visible electrodes. To increase the accuracy of the approximation we used head surface models. Freely available model from Oostenveld research based on data from SPM package and our own model based on data from our EEG/SPECT studies were used. For data collected in four cases with one electrode not visible we compared the invisible base electrode coordinates approximation for Oostenveld and our models. The results vary depending on the missing electrode placement, but application of the realistic head model significantly increases the accuracy of the approximation.

Open access

A. Śmiglewicz, M. Jabłońska, W. Moćko, K. Kowalczyk and E. Hadasik

Abstract

The paper presents the results of investigation on X30MnAlSi26-4-3 austenitic steel subjected to dynamic compression using the split Hopkinson pressure bar. The strain rate was 3700 s−1. The compression test was also carried out without the use of breaking rings and then true strain was about 0.3. The split Hopkinson pressure bar test take only few milliseconds to complete during which time it is impossible to transfer the excess heat out of the specimen, therefore the test must be carried out in adiabatic conditions and so the increase of the temperature caused by the work of plastic deformation had to be calculated. The stepping load method was used in order to evaluate the effect of adiabatic heating on the properties of steel which allowed to maintain the isothermal deformation conditions. The paper presents the comparison of results obtained during deformation under adiabatic and isothermal conditions in correlation to structure changes occurring in course of dynamic compression.