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- Andreeva, M. A., et al.
(författare)
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Nuclear resonant reflectivity with standing waves for the investigation of a thin 57Fe layer buried inside a superconducting Si/[Mo/Si]45/57Fe/Nb multilayer
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 266:1, s. 187-196
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Tidskriftsartikel (refereegranskat)abstract
- A special multilayer sample Si/[Mo/Si]45/57Fe/Nb has been prepared for the depth selective investigations of the hyperfine fields in thin iron layer at low temperatures above and below the superconducting transition in the top Nb layer (Tc 8 K) by means of the nuclear resonant reflectivity with standing waves. The periodic multilayer [Mo/Si]45 below the iron layer in our sample was used as “a standing wave generator”. A weak magnetic hyperfine splitting in the 57Fe layer was detected just at low temperature. A slight variation of the nuclear resonant reflectivity time spectra measured above and below Tc was observed. At first it was supposed that this change of the spectrum shape is caused by the spatial modulation of ferromagnetic domains in the 57Fe layer caused by a proximity effect. A closer analysis, however, reveals that the spectrum variations are due to just the changes of the relative weights of the magnetic and paramagnetic phases in 57Fe layer.
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| 5. |
- Andreeva, M. A., et al.
(författare)
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Polarization selection in Mössbauer reflectivity for magnetic multilayer investigation
- 2019
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Ingår i: VII Euro-Asian Symposium on Trends In Magnetism. - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- Mossbauer reflectivity experiment with polarization selection are reported. The use of the LiF polarization analyzer allows us to get the pi ->sigma' peak on the reflectivity curve at the critical angle and Mossbauer pi ->sigma' reflectivity spectra of reasonable quality at the critical angle and also at the Bragg angles of superlattice. The impressive difference of the reflectivity spectra measured near the critical angle with and without polarizations analysis is observed for [Fe-57(10)/V-10](20) multilayer characterizing by the ferromagnetic interlayer coupling. The combined fit of the whole set of spectra measured at different angles reveals the existence of antiferromagnetic Fe oxide phases in the top three bilayers. The experiment demonstrates benefits of the Mossbauer reflectivity with polarization analysis in ultrathin surface layer investigations.
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| 8. |
- Nagy, E., et al.
(författare)
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The impact of the COVID-19 pandemic on autoimmune diagnostics in Europe: A lesson to be learned
- 2021
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Ingår i: Autoimmunity Reviews. - : Elsevier BV. - 1568-9972. ; 20:12
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The first wave of COVID-19 pandemic has disrupted almost all areas of the health care services to some extent throughout the world. Although the negative impact of COVID-19 on patients with autoimmune diseases has also been recognized, available data in this regard are limited. In the current study of the European Autoimmunity Standardisation Initiative (EASI) we aimed to provide reliable data on the extent of the impact of COVID-19 pandemic on test requests for different autoantibodies in European countries. Methods: Data on test numbers and on the number of positive results were collected in 97 clinical laboratories from 15 European countries on a monthly basis for the year before (2019) and the year during (2020) the COVID19 pandemic. Results: A reduction in the number of autoantibody tests was observed in all European countries in the year 2020 compared to 2019. The reduction affected all autoantibody tests with an overall decrease of 13%, ranging from 1.4% (Switzerland) to 25.5% (Greece). In all countries, the decrease was most pronounced during the first wave of the pandemic (March-May 2020) with an overall decrease in those three months of 45.2%. The most affected autoantibodies were those commonly requested by general practitioners (anti-tTG IgA (71%), RF IgM (66%) and ACPA (61%)). In the second wave of the pandemic (October-December 2020) the decrease was less pronounced (6.8%). With respect to the rate of positive results, subtle differences were observed for distinct autoantibodies during the pandemic, but the total rate of positive results was similar in both years. Conclusions: Our study demonstrated a strong decrease in autoantibody requests during the first wave of the COVID-19 pandemic in 15 European countries. The second wave was characterized by a less pronounced impact, with some participating countries hardly affected, while some other countries experienced a second decline. The decrease was clearly associated with the level of lock-down and with the required adjustments in the health care systems in different countries, supporting the importance of an effective strategy for the coordination of autoimmune testing in challenging situations as the COVID-19 pandemic.
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| 9. |
- Andreeva, M. A., et al.
(författare)
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Magnetic ordering in a [Fe/Co](35) BCC film studied by nuclear resonant reflectometry
- 2007
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 104:4, s. 577-585
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Tidskriftsartikel (refereegranskat)abstract
- An analysis of the angular dependences of nuclear resonant reflectivity time spectra for different models of magnetic ordering in films reveals an ambiguity in the magnetization direction determined from spectra measured at one orientation of the sample. This analysis explains features in the spectra of the nuclear resonant reflectivity from a MgO/[Fe(6 ML)/Co(3 ML)]35/V (1 nm) film measured before and after sample rotation by 90° about the normal to the surface. It is shown that the spectrum measured only at one orientation of the sample determines only the effective azimuth angle of magnetization γeff. This does not exclude the occurrence of a domain structure, while the angle γeff does not correspond to the true direction of the preferred orientation of magnetization. The results of measurements at two orientations of the sample can be satisfactorily matched using a model that considers a coherent mixture of states with magnetization directed along the 〈110〉 axis (77%) and with a chaotic orientation of the magnetic hyperfine field B hf in the film plane for the other nuclei.
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