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Search Results: 1 - 10 of 401359 matches for " M. Kaczmarek "
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Corrosion resistance of NiTi alloy in simulated body fluids
M. Kaczmarek
Archives of Materials Science and Engineering , 2007,
Abstract: Purpose: Corrosion resistance of an implant alloy is a very important determinant of its biocompatibility. The nature of an environment and surface treatments have a significant influence on corrosion. Most of the knowledge on the corrosion behavior of NiTi is from studies of “standard” corrosion tests. In fact, the knowledge of the corrosion behavior of NiTi inside the body is very limited. The main aim of the research was evaluation of corrosion resistance of NiTi alloy in various simulated body fluids.Design/methodology/approach: The evaluation of the electrochemical behavior of NiTi alloy was realized by recording of anodic polarization curves with the use of the potentiodynamic method. The tests were carried out for differently modified surfaces in diverse simulated body fluids.Findings: Surface condition of a metallic biomaterial determines its corrosion resistance. In the course of the work the good corrosion resistance of all the tested samples (with different surface conditions) was observed.Research limitations/implications: The obtained results are the basis for the optimization of physicochemical properties of the NiTi alloy. The future research should be focused on selected specific implants specially with respect to their application features.Practical implications: On the basis of the obtained results it can be stated that the suggested surface treatment can be applicable for NiTi alloys due to the increase of the corrosion resistance.Originality/value: The paper presents the influence of various methods of the surface treatment on corrosion resistance of the NiTi alloy. The suggested surface treatment methods can be applied to implants intended for diverse medical applications, especially in cardiology and urology.
Crevice corrosion resistance of NiTi alloy after various surface treatments
M. Kaczmarek
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: The aim of the work was determination of crevice corrosion resistance of NiTi alloy after varioussurface treatments.Design/methodology/approach: The evaluation of the electrochemical behavior of NiTi alloy was realizedby recording of anodic polarization curves with the use of the potentiodynamic method in the presence of a creviceformer. Tests were carried out in Tyrode’s physiological solution.Findings: Surface condition of metallic biomaterial determines its corrosion resistance. In the course of thework it was observed that only ground samples showed no resistance to crevice corrosion. Suggested surfacemodifications ensure good crevice corrosion resistance.Practical implications: On the basis of the obtained results it can be stated that the suggested surface treatmentcan be applied for medical implants due to increase of the crevice corrosion resistance and in consequence increaseof biocompatibility.Originality/value: The paper presents the influence of various methods of surface treatment on crevice corrosionresistance of the NiTi alloy. The suggested methods can be applied in treatment of the material intended for medicalapplications especially as reduced and complex shape implants (contact of metallic material with human bodyfluids in a small and occluded space).
Influence of Lanthanide(III) Ions on the Reaction System Tryptophan—
M. Kaczmarek,S. Lis
International Journal of Photoenergy , 2007, DOI: 10.1155/2007/42582
Abstract: Chemiluminescence (CL) studies were carried out with luminescent lanthanide ions as probes to a tryptophan-oxidation reaction at pH ∼ 6. The redox system consisted of tryptophan, hydrogen peroxide, and Fe(II) ions (catalysts of H2O2 decomposition). The luminescent lanthanide(III) ions used were Eu(III), Tb(III), Gd(III), and Dy(III). In the case of the reaction system with the Tb(III) ion a significant increase in the chemiluminescence intensity and its duration was observed over the other Ln(III) ions. The CL spectrum registered for this system shows emission bands typical of Tb(III) ions with maxima at λ ∼ 490 and 550 nm, corresponding to the electronic transitions of 5D4→7F6 and 5D4→7F5, respectively. The presence of emission bands characteristic of the Ln(III) ions was also observed in the systems containing Eu(III) and Dy(III) ions. These studies revealed a strong influence of the chemiluminescence intensity associated with the tryptophan oxidation, on the concentration of Ln(III) ions. On the basis of the results obtained, a possible mechanism is proposed for reaction of the systemml: Ln(III)—tryptophan—H2O2–Fe(II), taking into consideration an energy transfer process from the tryptophan oxidation products to the Tb(III), Dy(III), or Eu(III) ions.
Temperature dependence of electrical conductivity and dilepton rates from hot quenched lattice QCD
Olaf Kaczmarek,Marcel Müller
Physics , 2013,
Abstract: We present new results on the continuum extrapolation of the vector current correlation function in the deconfined phase for three temperatures close to the critical temperature utilizing quenched clover improved Wilson fermions and light quark masses. A systematic analysis on multiple lattice spacing allows to perform the continuum limit of the correlation function and to extract spectral properties in the continuum limit. These results provide constraints for the electrical conductivity and the thermal dilepton rates in the quark gluon plasma for the given temperature range. In addition results on the continuum extrapolation at finite momenta related to thermal photon rates are presented.
Biomechanical characterization of the balloon-expandable slotted tube stents
M. Pochrz?st,W. Walke,M. Kaczmarek
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The aim of the presented work was determination of the biomechanical characteristics of the vascular stent made of stainless steel (Cr-Ni-Mo) and Co-Cr-W-Ni alloy. Additionally, in order to compare obtained results, an experimental analysis of the stent made of stainless steel was carried out.Design/methodology/approach: In order to determine the strength characteristics of the analyzed stent the finite element method was applied. Geometrical model of the vascular stent, which was meshed with the use of the SOLID95 element, was worked out. Selection of the finite element was conditioned by large strains that occur during angioplastic procedure. The established boundary conditions imitated the phenomena during the balloon expansion in real conditions.Findings: The result of the analysis was determination of relationship between equivalent stresses and strains in the individual regions the stent in the function of the diameter’s change (d = 1.20 - 4.00 mm) caused by expanding pressure. Analysis of the obtained results indicates diverse distribution of stresses and strains in the stent depending on the applied biomaterial.Research limitations/implications: The obtained results of the biomechanical analysis of the coronary stent are valuable information for correct design of the geometry and mechanical properties of the applied metallic biomaterials. Strain analysis of the stent indicates that in order to limit a surface reactivity of the stent in blood environment, a deformable surface layer must be applied.Originality/value: Results of the numerical analysis indicate that mechanical properties of the metallic biomaterials used to manufacture the analyzed vascular stent were selected correctly. The correctness of the selection (mechanical properties of the metallic biomaterials) should be confirmed in in vitro tests realized with the use of the coronary angioplasty set.
(2S,4R)-4-Ammonio-5-oxopyrrolidine-2-carboxylate
Krzysztof Kaczmarek,Jakub Wojciechowski,Wojciech M. Wolf
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810004277
Abstract: In the crystal structure of the title compound, C5H8N2O3, the molecules exist in the zwitterionic form. The pyrrolidine ring adopts an envelope conformation with the unsubstituted endocyclic C atom situated at the flap. The other four endocyclic atoms are coplanar with the exocyclic carbonyl O atom, with an r.m.s. deviation from the mean plane of 0.06 . The carboxylate substituent is located axially, while the ammonium group occupies an equatorial position. In the crystal structure, the molecules are linked through N—H...O hydrogen bonds, forming a three-dimensional network.
Chemical composition of passive layers formed on metallic biomaterials
M. Kaczmarek,W. Walke,W. Kajzer
Archives of Materials Science and Engineering , 2007,
Abstract: Purpose: In the paper the results of chemical composition investigations of passive layers formed on implants made of Cr-Ni-Mo steel, Co-Cr-W-Ni alloy and Ni-Ti alloy have been presented.Design/methodology/approach: Chemical composition investigations of the passive layer have been carried out with the use of X-ray Photoelectron Spectroscopy (XPS). The X-ray photoelectron spectroscopy with monochromatic radiation AlKα of 1486,6 eV was applied. The tests were carried out on the samples of polished as well as polished and passivated surfaces. The measurement of photoelectron spectrum in the wide range of binding energy from 0-1400 eV and precise measurements of the spectrum lines of elements from the surface layer were conducted.Findings: The chemical composition analysis of passive layers on the Cr-Ni-Mo steel, the Co-Cr-W-Ni alloy and the Ni-Ti alloy has revealed the presence of the following elements: (C, N, O, Na, Mg, Ca, Cr, Fe, Ni), (C, O, N, Cr, Fe, Co, Ni, W) and (C, N, O, Na, Si, S, Cl, K, Ca, Ti, Ni) respectively.Research limitations/implications: The research was carried out on samples, not on final parts. The tests were carried out in in vitro conditions. The obtained results are promising however further studies, in particular in blood environment, will determine a usefulness of the suggested technique of stents’ surface improvement.Originality/value: The obtained results show the usefulness of the applied surface treatment to refine surfaces of implants made of the Cr-Ni-Mo steel, the Co-Cr-W-Ni alloy and the Ni-Ti alloy.
Influence of medium and surface modification on corrosion behaviour of the cobalt alloy
W. Kajzer,M. Kaczmarek,J. Marciniak
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: The work presents the influence of artificial urine environment and surface treatment of Co-Cr-W-Ni alloy, intended for implants applied in urogenital surgery, on their corrosion resistance. The tests were carried out in three artificial urine solutions that differed in chemical composition at the temperature 37±1°C and pH = 5.6-6.4. In particular, the pitting and crevice corrosion resistance tests were carried out.Design/methodology/approach: The corrosion tests were realized by recording of anodic polarization curves with the use of the potentiodynamic method. The VoltaLab PGP 201 system for electrochemical tests was applied. The tests were carried out in electrolyte simulating urine (pH = 5.6-6.4) at the temperature of 37±1°C.Findings: The obtained results indicate diverse corrosion resistance of the Co-Cr-W-Ni alloy depending on the applied surface treatment and chemical composition of the artificial urine that can be connected with individual reactivity of patients.Research limitations/implications: The obtained results are the basis for optimization of physicochemical properties of the Co-Cr-W-Ni alloy and allow to select only one artificial urine solution for further corrosion tests.Practical implications: On the basis of the obtained results it can be stated that Co-Cr-W-Ni alloy can be applied in urology.Originality/value: The paper presents the influence of artificial urine environment and the surface treatment on corrosion resistance of Co-Cr-W-Ni alloy.
Numerical analysis of femur in living and dead phase
A. Krauze,M. Kaczmarek,J. Marciniak
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: The paper presents numerical analysis results of stresses and displacement in femur in a living and a dead phase. The aim of the work was to present the influence of different mechanical properties of bone tissue on the obtained results. The appropriate selection of the properties ensures correct results, comparable with the results obtained in real conditions.Design/methodology/approach: The analysis was carried out on the femur of adult. The influence of the selected properties on the results of numerical analyses was analyzed. In order to carry out calculations, 3 models of diverse mechanical properties (Young modulus of bone in a living phase EI=17260 MPa, Young modulus in order to carry out a comparison analysis EII.=18600 MPa and Young modulus of bone in a dead phase EIII=20202 MPa) were selected.Findings: The analyses showed the difference in displacements and reduced stresses depending on the selected mechanical properties. The analyses show that in order to select the appropriate stabilization method, mechanical characteristics of bone structures should be considered as viscoelastic. Quality of bone structures depends on individual features (genetic, hormonal, metabolic and circulatory factors).Research limitations/implications: The limitations were connected with simplification of numerical model of femur as well as with the selected boundary conditions.Practical implications: The obtained results can be useful in clinical practice. They can be applied in selection of stabilization methods or rehabilitation as well as in describing the biomechanical conditions connected with type of bone fracture obtained from medical imaging.Originality/value: Stress – displacement characteristics of femur for different degrees of demineralization, obtained from the numerical analyses were presented in the work.
High Resolution H I Distributions and Multi-Wavelength Analyses of Magellanic Spirals NGC 4618 and NGC 4625
Jane F. Kaczmarek,Eric M. Wilcots
Physics , 2012, DOI: 10.1088/0004-6256/144/2/67
Abstract: We present a detailed analysis of high resolution H I observations of the Magellanic spiral galaxies NGC 4618 and NGC 4625. While the H I disk of NGC 4625 is remarkably quiescent with a nearly uniform velocity dispersion and no evidence of H I holes, there is a dynamic interplay between star formation and the distribution of neutral hydrogen in NGC 4618. We calculate the critical density for widespread star formation in each galaxy and find that star formation proceeds even where the surface density of the atomic gas is well below the critical density necessary for global star formation. There are strong spatial correlations in NGC 4618 between UV emission, 1.4 GHz radio continuum emission, and peaks in the H I column density. Despite the apparent overlap of the outer disks of the two galaxies, we find that they are kinematically distinct, indicating that NGC 4618 and NGC 4625 are not interacting. The structure of NGC 4618 and, in particular, the nature of its outer ring, are highly suggestive of an interaction, but the timing and nature of such an interaction remain unclear.
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