Marianna Marciszko

Neuroprotective action of FK-506 (tacrolimus) after seizures induced with pilocarpine: quantitative and topographic elemental analysis of brain tissue

In the present work, X-ray fluorescence microscopy with a synchrotron source for the exciting radiation was applied for topographic and quantitative elemental analysis of rat brain tissue in pilocarpine-induced epilepsy and neuroprotection with FK-506. The mass per unit area of the elements P, S, Cl, K, Ca, Fe, Cu, Zn, Se, Br, and Rb was determined in four fields of the hippocampal formation (sectors 1 and 3 of Ammon’s horn–CA1, CA3; dentate gyrus; hilus of dentate gyrus) and the parietal cortex. The results obtained for epileptic rats treated with FK-506 (SNF) were compared with data obtained previously for epileptic rats (SNS) and a control group. Many statistically significant differences in elemental composition were observed between the SNF and SNS groups. Higher mass per unit area of P was noticed in CA1 and CA3 regions of the hippocampus of SNF rats in comparison with SNS rats. A similar relation was observed for K in all five brain areas analyzed. Also, Fe in CA3 and dentate gyrus, Cu in the parietal cortex, and Zn in CA3 and in the cortex were present at a higher level in the SNF group in comparison with the SNS group. The findings obtained in the present study suggest that the neuroprotective action of FK-506 in epileptic rat brain may involve not only the inhibition of calcineurin but also blockade of the K+ channels.

Analysis of stresses and crystal structure in the surface layer of hexagonal polycrystalline materials: a new methodology based on grazing incidence diffraction

The multireflection grazing-incidence X-ray diffraction (MGIXD) method is commonly used to determine a stress gradient in thin surface layers (about 1–20 µm for metals). In this article, the development of MGIXD to enable the determination not only of stresses but also of the c/a ratio and the a0 strain-free lattice parameter in hexagonal polycrystalline materials is presented and tested. The new procedure was applied for the results of measurements performed using a laboratory X-ray diffractometer and synchrotron radiation. The evolution of stresses and lattice parameters with depth was determined for Ti and Ti-alloy samples subjected to different mechanical surface treatments. A very good agreement of the results obtained using three different wavelengths of synchrotron radiation as well as classical X-rays (Cu Kα radiation) was found.

Problem of elastic anisotropy and stacking faults in stress analysis using multireflection grazing-incidence X-ray diffraction

Multireflection grazing-incidence X-ray diffraction (MGIXD) was used to determine the stress- and strain-free lattice parameter in the surface layer of mechanically treated (polished and ground) tungsten and austenitic steel. It was shown that reliable diffraction stress analysis is possible only when an appropriate grain interaction model is applied to an anisotropic sample. Therefore, verification of the X-ray stress factors (XSFs) was accomplished by measuring relative lattice strains during an in situ tensile test. The results obtained using the MGIXD and standard methods ( and geometries) show that the Reuss and free-surface grain interaction models agree with the experimental data. Moreover, a new interpretation of the MGIXD results was proposed and applied for the first time to measure the probability of stacking faults as a function of penetration depth for a polished and ground austenitic sample. The XSF models verified in the tensile test were used in the analysis of residual stress components.

Stress in Aluminium Alloys Measured Using Göbel Mirror as a Primary Beam Optics of X-Ray Diffractometer

Grazing incidence geometry, called MGID-sin2y, was applied to measure surface stresses in very thin layers (depth of a few mm) of Al-Mg alloy samples subjected to different thermal and mechanical treatments. The Göbel mirror was used to parallelize the incident X-ray beam. Perfect collimation of the beam significantly increases accuracy of determined peak position and consequently allows to measure low stresses in surface layers.

Stress Measurements in Polished Al-Mg Alloy and CrN Coating Using Multireflection Grazing Incidence Method

The multi-reflection grazing incidence X-ray diffrection was used to determine residual stress gradient in the mechanically polished Al-Mg alloy and CrN coating. Also, the root mean square values of the third order lattice strain was determined using Wiliamson-Hall method. The results obtained for Al-Mg alloy show that the stress field in the surface layer as well as the microstructure (density of dislocation) depend strongly on the sample preparation. A very high residual compressive stress, which does not change significantly with depth, was measured in the CrN coating. Moreover, a large value of the measured third order strains in the coating was found.

A multireflection and multiwavelength residual stress determination method using energy dispersive diffraction

Multireflection grazing-incidence X-ray diffraction was used to investigate the structure and residual stress gradients in the near-surface region of mechanically treated titanium samples. The development of this method by using a white synchrotron beam during an energy dispersive diffraction experiment is proposed.

In-Depth Distribution of Stresses Measured by Multireflection Grazing Incidence Diffraction

The geometry based on the multireflection grazing incidence X-ray diffraction (called the MGIXD method) can be applied to measure residual stresses. Using this method, it is possible to perform a non-destructive analysis of the heterogeneous stresses for different and well defined volumes below the surface of the sample (range of several mm). As the result the average values of stresses weighted by absorption of X-ray radiation are measured. In this work the stress profile as a function of depth for mechanically polished Ti and Al samples were calculated from MGIXD data using inverse Laplace transform.

Neutron Diffraction Study of Elastoplastic Behaviour of Al/SiCp Metal Matrix Composite during Tensile Loading and Unloading

The aim of the present work is to study effects occurring during elatoplastic deformation and unloading of Al/SiCp metal–matrix composite material. We have measured lattice strains for both phases independently using two separated diffraction peaks (the 111 reflections of Al and SiC) during in situ tensile testing. Lattice strains were measured in the direction parallel to the applied load. The results were compared with an elastoplastic model in order to find parameters determining the plastic deformation of Al matrix (critical resolved shear stress and hardening parameter). We have found that during initial deformation relaxation of the thermal stresses occurs in both phases. Afterwards, the distribution of strains measured during the in situ test and unloading of the sample agree very well with self-consistent model prediction.

Different Grain Interaction Models Used for Interpretation of Lattice Strain Data Collected Using Grazing Incidence X-Ray Diffraction

Multireflection grazing incidence X-ray diffraction (MGIXD) was applied to measure residual stresses in thin surface layers and the problem of X-ray elastic constants (XEC) used for the interpretation of results was studied. To show the influence of the X-ray elastic constants on the interpretation of MGIDX results, polycrystalline materials having low (Ti alloy) and high elastic anisotropy of crystallites (Ni alloy) were investigated.

Application of Göbel Mirror for Stress Measurement Using Grazing Incidence Geometry

The Göbel mirror allows parallelization of the divergent X-ray beam leading to its higher intensity. Perfectly collimated (parallel) beam radically decreases errors of determined peak position in diffraction experiments. In the present work the Göbel mirror was applied for stress measurements using grazing incidence geometry.