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  • Magnetoresistance effect in Gd-doped Cu-Co alloys

    Jaworski, Jacek   Strzala, Alicja   Kwon, Oh-Jib   Fleury, Eric  

    The present paper reports results on the Gd-doped Co-Cu granular alloys and metallic glasses prepared by different processing methods. The main aim of this research was to produce a ternary alloy which radically changes its magnetoresistance (MR) properties below critical temperature. A detailed study on the evolution of the structure and phase separation is presented basing on X-ray diffractometry (XRD) analysis and scanning electron microscopy (SEM) observation. MR was measured by means of a two point probe method in magnetic field using a new experimental device which was patented thereafter. (C) 2009 Elsevier B.V. All rights reserved.
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  • Dose perturbation caused by stents: Experiments with a model Sr-90/Y-90 source

    Wilczek, Krzysztof   Petelenz, Barbara   Strzala, Alicja   Marczewska, Barbara   Traczyk, Marek   Polonski, Lech  

    Purpose Biological effects of intravascular brachytherapy are very sensitive to discrepancies between the prescription and the applied dose. If brachytherapy is aimed at in-stent restenosis, shielding and shadowing effects of metallic stents may change the dose distribution relative to that produced by the bare source. The development of new generations of stents inspired us to a new experimental study in this field. The effect was studied for 14 stents which we have recently encountered in clinical practice. Methods The model source was a continuous 20-mm column of Sr-90/Y-90 solution sealed in a 1-mm-I.D. Plexiglas capillary. The dose distribution in the Plexiglas phantom was mapped using GafChromic MD-55-2 film. The stent masses varied from 2.5 to 25 mg; the strut thicknesses, from 0.075 to 0.15 mm; and the atomic numbers of stent materials, from 24 (Cr) to 79 (Au). Results Dose perturbations depend on a variety of stent features. Local reduction of the mean dose rates near the reference distance (r(0) = 2 mm) varied from 11% to 47%. No simple correlation was found between these data and stent characteristics, but it seems that the atomic number of the stent material is less important than the strut thickness and mesh density. Conclusions The results provide a warning that clinical indications for in-stent radiation therapy must always be confronted with another aspect of the patient's history: the kind of implanted stent. Intravascular brachytherapy using pure beta sources may be recommended only for patients "wearing" light, thin-strut stents. The presence of thick-strut stents is a contraindication for this modality, due to excessive dose perturbation.
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