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Wyszukujesz frazę "Ferreira Marques, M." wg kryterium: Autor


Wyświetlanie 1-5 z 5
Tytuł:
Study on the Structure of Defects in a-Si:H Films by Positron Annihilation and Micro-Raman Spectroscopy
Autorzy:
Gordo, P.
de Lima, A.
Ferreira Marques, M.
Kajcsos, Zs.
Powiązania:
https://bibliotekanauki.pl/articles/1812497.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.66.Jg
78.70.Bj
78.30.Ly
Opis:
Thin films of hydrogenated amorphous silicon deposited on glass and crystalline silicon substrates by rf plasma enhanced chemical vapor deposition at different rf power were studied using slow positron beam and the Raman scattering spectroscopy in order to verify the influence of that deposition parameter on the film defect structure and on the degree of disorder. By positron annihilation spectroscopy, it was found that there are mainly two types of defects in the films: large vacancy clusters or voids and small vacancy type defects. By micro-Raman spectroscopy it was observed that the degree of structural disorder is lower for the film with large vacancy clusters and this finding was related to structural relaxation process. Light soaking induced changes attributed to major atomic rearrangements were also observed.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1373-1378
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy
Autorzy:
Ferreira Marques, M.
Gordo, P.
de Lima, A.
Queiroz, D.
Norberta de Pinho, M.
Major, P.
Kajcsos, Zs.
Powiązania:
https://bibliotekanauki.pl/articles/1812490.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.41.+e
78.70.Bj
82.30.Gg
Opis:
Positron annihilation lifetime spectroscopy was used to study the free volume parameters in polypropylene oxide-based tri-isocyanate terminated prepolymer/polycaprolactone diol bi-soft urethane/urea membranes (PU/PCL) with PCL content from 5 up to 25 wt%. Positron annihilation lifetime spectroscopy measurements carried out in the temperature range 298-324 K mirrored the phase separation of the various soft and hard segments present in the membranes. The size and amount of free volume holes determined by positron annihilation lifetime spectroscopy appear to be correlated with the $CO_2$ gas permeability through the membranes.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1359-1364
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron and Positronium Trapping in Heat Treated Zeolites (Ceramics), the Effect of Swift Heavy Ion Irradiation
Autorzy:
Major, P.
Kajcsos, Zs.
Liszkay, L.
Zalán, P.
Kosanović, C.
Bosnar, S.
Subotić, B.
Lázár, K.
Skuratov, V.
Havancsák, K.
Gordo, P.
Ferreira Marques, M.
Powiązania:
https://bibliotekanauki.pl/articles/1812537.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.43.Gt
36.10.Dr
61.80.Jh
Opis:
A systematic study of zeolite precursor gels, zeolites, and products of their recrystallization to ceramics was carried out in presence of various alkali ions. The investigation of radiation damage induced by high-energy ion beam irradiation with swift heavy ions (Bi ions at 670 MeV energy with $4×10^{12}$ ion/$cm^2$ fluence) was also included. The shortening of lifetimes found after irradiation in ceramics might probably be ascribed to interactions of o-Ps with free radicals and other quenching agents created through the ion irradiation. These lifetime-shortening interactions probably partly hide the o-Ps trapping in free volume sites.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1441-1446
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Trapping in Porous Solids: Means and Limitations for Structural Studies
Autorzy:
Kajcsos, Zs.
Liszkay, L.
Duplâtre, G.
Varga, L.
Lohonyai, L.
Pászti, F.
Szilágyi, E.
Lázár, K.
Kótai, E.
Pál-Borbély, G.
Beyer, H. K.
Caullet, P.
Patarin, J.
Azenha, M. E.
Gordo, P. M.
Lopes Gil, C.
de Lima, A. P.
Ferreira Marques, M.
Powiązania:
https://bibliotekanauki.pl/articles/2042216.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
61.43.Gt
Opis:
Positron annihilation techniques are used for the structural investigation of solids but the interpretation of results in grainy and porous media is still unclear. A unique picture can be obtained assuming that the dominant process is Ps trapping in competing "extended free volume" sites. In samples with a large amount of free volumes near-saturation Ps trapping will rule the lifetime pattern, and very long lifetimes of over 100 ns might arise from o-Ps trapped in mesopores. It is shown that lifetime parameters must be corrected for the 3γ/2γ counting efficiency ratio. The results demonstrate the high sensitivity of Ps to mesopores in zeolites but also that Ps-trapping poses limitations on the applicability of lifetime to structural investigation in porous systems. The evolution of the lifetime spectra upon changes in the sample and measuring conditions should be considered in a complex way, observing not only changes in some selected components but in the whole lifetime pattern simultaneously.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 729-737
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Time-of-Flight Positron Emission Tomography with Resistive Plate Chamber Detectors: An Unlikely but Promising Approach
Autorzy:
Couceiro, M.
Crespo, P.
Blanco, A.
Ferreira, N.
Mendes, L.
Ferreira Marques, R.
Fonte, P.
Powiązania:
https://bibliotekanauki.pl/articles/1402607.pdf
Data publikacji:
2015-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.57.uk
29.40.Cs
87.57.cf
87.57.cm
Opis:
The cost-effectiveness of resistive plate chamber detectors and their very good timing characteristics, open the possibility to build affordable time-of-flight positron emission tomography systems with a large axial field-of-view. Simulations suggest that, under reasonable assumptions, the absolute 3D true sensitivity, spatial resolution, and noise equivalent count rate of such systems for human whole-body screening, may exceed that of present crystal-based PET technology. However, due to the lack of energy resolution, although having energy sensitivity, the scatter fraction is expected to be considerably higher than that presented by crystal-based PET scanners. In the present paper, the simulation work done so far to access the expected performance of a resistive plate chamber time-of-flight-PET system with 2400 mm length axial field-of-view, a time resolution of 300 ps full width at half maximum for photons pairs, and depth-of-interaction information, will be revised.
Źródło:
Acta Physica Polonica A; 2015, 127, 5; 1453-1461
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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