Autor: Zecca, A. - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Positron Annihilation Studies of Czochralski-Grown Silicon Annealed Under Pressure
Autorzy:: Karwasz, G. P.
Brusa, R. S.
Misiuk, A.
Zecca, A.
Tematy:: 71.60.+z
78.70.Bj
71.55.Cn; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2008074.pdf Link otwiera się w nowym oknie
Opis:: Two positron techniques have been applied to study dynamics of oxygen precipitation in Czochralski-grown silicon, annealed under high (up to 1.4 GPa) pressure. Lifetime measurements were performed with 180 ps resolution; Doppler broadening with a variable-energy slow-positron beam. Different thermal treatings rise the mean lifetime of positrons from 222 ps in as-grown samples up to 227 ps. In samples with a high (up to 85%) amount of oxygen precipitated, an intermediate (550-800 ps) lifetime is observed.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 2.

Tytuł:: Systematic Measurements of Doppler-Coincidence Spectra for Positron Annihilation in Pure Metals and Semiconductors
Autorzy:: Deng, W.
Pliszka, D.
Brusa, R. S.
Karwasz, G. P.
Zecca, A.
Tematy:: 71.60.+z
78.70.Bj; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2030758.pdf Link otwiera się w nowym oknie
Opis:: Doppler-broadening measurements of the electron-positron annihilation line in twenty six elements are presented. The adopted coincidence technique allows to reduce the background and point out the contribution of positron annihilation with core electrons. The changes of the high momentum contribution is presented for selected examples and a semiempirical analysis of the dependence on electronic structure is performed. Measured data are in a good agreement with recent theoretical calculations and can be used to identification of impurities surrounding open volume defects.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 3.

Tytuł:: Surfaces of Electron-Emitting Glasses Studied by a Slow Positron Beam
Autorzy:: Pliszka, D.
Gazda, M.
Kusz, B.
Trzebiatowski, K.
Karwasz, G. P.
Deng, W.
Brusa, R. S.
Zecca, A.
Tematy:: 71.60.+z
78.70.Bj; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2025748.pdf Link otwiera się w nowym oknie
Opis:: Semi-conducting glasses used for electron multipliers and microchannel plate devices are obtained by surface modification of Pb or Bi-reach silicon-based glasses. The reduced layer extends down to 200-500 nm, much more than the effective depth of the electron-emitting layer. By the use of slow-positron beam we monitor the structural changes undergoing in near-to-surface layers after isothermal annealing. The measurements suggest a possible correlation between secondary-electron emission coefficient and the Doppler-broadening S-parameter. On these samples there were also performed atomic force microscopy, secondary electron emission, differential scanning calorimetry, and electric conductivity measurements.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 4.

Autorzy:: Sarna, Michał
Sarna, Tadeusz
Capucciati, Andrea
Bellei, Chiara
Zecca, Luigi
Zucca, Fabio A.
Monzani, Enrico
Casella, Luigi
Opis:: Neuromelanins are compounds accumulating in neurons of human and animal brain during aging, with neurons of substantia nigra and locus coeruleus having the highest levels of neuromelanins. These compounds have melanic, lipid, peptide, and inorganic components and are contained inside special autolysosomes. Neuromelanins can participate in neuroprotective or toxic processes occurring in Parkinson's disease according to cellular environment. Their synthesis depends on the concentration of cytosolic catechols and is a protective process since it prevents the toxic accumulation of catechols-derived reactive compounds. Neuromelanins can be neuroprotective also by binding reactive/toxic metals to produce stable and non-toxic complexes. Extraneuronal neuromelanin released by dying dopamine neurons in Parkinson's disease activates microglia which generate reactive oxygen species, reactive nitrogen species, and proinflammatory molecules, thus producing still neuroinflammation and neuronal death. Synthetic neuromelanins have been prepared with melanic, protein structure, and metal content closely mimicking the natural brain pigment, and these models are also able to activate microglia. Neuromelanins have different structure, synthesis, cellular/subcellular distribution, and role than melanins of hair, skin, and other tissues. The main common aspect between brain neuromelanin and peripheral melanin is the presence of eumelanin and/or pheomelanin moieties in their structure.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego