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    Wyświetlanie 1-12 z 12
    Tytuł:
    Resonance production in heavy ion collisions
    Autorzy:
    Markert, Ch.
    Powiązania:
    https://bibliotekanauki.pl/articles/146392.pdf
    Data publikacji:
    2004
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    resonance
    strangeness
    baryon
    freeze-out
    lifetime
    fireball
    Opis:
    Resonances and their decay products may interact strongly with the hadrons in the fireball medium from the time of chemical freeze-out until the system breaks up at kinetic freeze-out. In order to try to further our understanding of the evolution and expansion of this hot and dense medium we compare resonance particle yields and spectra from elementary p+p and heavy ion collisions.
    Źródło:
    Nukleonika; 2004, 49,suppl.2; 119-123
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Low energy electrons in non-polar liquids
    Autorzy:
    Schmidt, W.
    Illenberger, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/148513.pdf
    Data publikacji:
    2003
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    electrons
    energetics
    kinetics
    non-polar liquids
    lifetime
    Opis:
    The properties of excess electrons in non-polar liquids have been studied for more than 30 years. Here, pertinent results are reviewed and discussed with respect to the possibility of studying electron-molecule interactions with low energy electrons in the liquid phase. Some new results on the estimate of the electron lifetime in the delocalized state in liquid hydrogen are presented.
    Źródło:
    Nukleonika; 2003, 48, 2; 75-82
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The influence of hydrogen concentration on positron lifetime and electrical resistivity in vanadium-hydrogen systems
    Autorzy:
    Pietrzak, R.
    Szatanik, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/146289.pdf
    Data publikacji:
    2010
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    positron lifetime
    resistivity
    V-H system
    annihilation parameters
    Opis:
    Positron lifetime spectra and electrical resistivity of the vanadium-hydrogen systems with hydrogen concentration ranging from 0 to 0.29 at.H/at.V have been investigated. The range of hydrogen concentrations under investigation included the single alfa phase and a mixture of the alfa and beta phases of V-H system. The registered positron lifetime spectra were analysed by decomposition into two components. A distinct change in the annihilation parameters has been found after exceeding the boundary concentration of hydrogen in vanadium corresponding to the phase transition alfa (alfa+ beta). Correlation of changes in the parameters of the positron lifetime spectrum and in the electrical resistivity resulting from the changes in hydrogen concentration, has been revealed.
    Źródło:
    Nukleonika; 2010, 55, 1; 35-39
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Positron annihilation lifetime spectroscopy study of thermal processing and rehydration of dry leek (Allium porrum L.)
    Autorzy:
    Zaleski, R.
    Wawryszczuk, J.
    Sobczak, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/146309.pdf
    Data publikacji:
    2010
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    positron annihilation
    lifetime spectroscopy
    food processing
    rehydration
    leek (Allium porrum L.)
    Opis:
    New application of positron annihilation lifetime spectroscopy (PALS) to development of food processing techniques is tested. Dehydrated leeks were an object of the study. Three experiments were performed consisting of evacuating air and volatile compounds from the sample, applying thermal treatment and rehydrating the sample. Distinct changes in positron lifetime spectra allowed the monitoring of alterations in the sample structure. The most likely origin of the particular components present in the spectra was able to be proposed from these data. Changes of the components were ascribed to the various processes occurring in the samples.
    Źródło:
    Nukleonika; 2010, 55, 1; 73-78
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    PALS investigation of resorcinol under high pressure
    Autorzy:
    Tydda, M.
    Jasińska, B.
    Pieniążek, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/147999.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    free volume
    ortho-positronium (o-Ps)
    pressure
    positron annihilation lifetime spectroscopy (PALS)
    Opis:
    Two kinds of measurements were conducted with resorcinol at high pressure : the first one with the use of a mechanical press and the second one with the use of a gaseous compressor. In the second case, due to some gas penetrating the material structure, the lifetime spectra obtained were difficult to analyze. The free volumes in resorcinol were influenced both by high pressure and the gas coming into the crystallographic structure.
    Źródło:
    Nukleonika; 2013, 58, 1; 195-198
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Principles of positron porosimetry
    Autorzy:
    Zaleski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/146520.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    porous materials
    positron annihilation lifetime spectroscopy (PALS)
    positronium
    extended Tao-Eldrup model
    Opis:
    The paper deals with positron porosimetry (PP), which is based on positron annihilation lifetime spectroscopy (PALS). The numerical analysis of positron lifetime spectra for PP is more demanding than in most of other applications of PALS. The resulting intensity distributions of ortho-positronium (o-Ps) lifetimes are interpreted in terms of the extended Tao-Eldrup (ETE) model, which provides the dependence between the o-Ps lifetime and pore size. Additionally, the relation between the intensity of an o-Ps component and the pore volume allows obtaining pore size distribution (PSD). The value of the empirical parameter Δ, which is dependent on material, can be estimated from the temperature dependence of an o-Ps lifetime. The most unique feature of PP among other techniques that allow determination of PSDs is its ability to perform measurements in almost any conditions. This makes this method suitable for various in situ studies. In this review article, both the capabilities and the limitations of PP are discussed. The methods to overcome some of the limitations are presented.
    Źródło:
    Nukleonika; 2015, 60, No. 4, part 1; 795-800
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ortho-positronium migration in mesopores of MCM-41, MSF and SBA-3
    Autorzy:
    Zaleski, R.
    Błażewicz, A.
    Kierys, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/147955.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    nitrogen adsorption/desorption
    porous materials
    positron annihilation lifetime spectroscopy (PALS)
    positronium migration
    Opis:
    Three materials: MCM-41, MSF and SBA-3 with a very similar pore diameter but different lengths of cylindrical pores were investigated using the nitrogen sorption method and positron annihilation lifetime spectroscopy. The size of primary pores and interparticle spaces obtained by both methods is similar. However, volume ratios between the discussed kinds of pores found by the above-mentioned methods differ significantly. Such discrepancy is the result of both ortho-positronium migration and the inaccessibility of the pores for nitrogen. Comparing the results of nitrogen sorption and positron annihilation lifetime spectroscopy allows us to estimate that connectivity between the primary pores and the interparticle spaces is the highest in MCM-41 and lowest in SBA-3.
    Źródło:
    Nukleonika; 2013, 58, 1; 235-240
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Photoluminescence and positron annihilation lifetime studies on pellets of ZnO nanocrystals
    Autorzy:
    Karbowski, A.
    Fedus, K.
    Patyk, J.
    Bujak, Ł.
    Służewski, K.
    Karwasz, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/148001.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    photoluminescence (PL)
    positron annihilation lifetime spectroscopy (PALS)
    X-ray diffraction (XRD)
    ZnO nanocrystals
    Opis:
    We explore the interrelationships between the X-ray diffraction patterns, the photoluminescence spectra and the positron lifetimes obtained from circular pellets composed of commercial ZnO nanoparticles. The experimental results are studied as a function of thermal treatment at different temperatures. X-ray diffractograms reveal the temperature- independent wurtzite phase structure of nanocrystals and show huge enlargement of ZnO grains after annealing at temperatures higher than 700 centigrade. Photoluminescence measurements exhibit two emission bands : a near band edge emission in UV (small tilde 378 nm) and a defect-related broad visible peak with a maximum in the green region ( small tilde 502 nm). The significant enhancement of the green emission at the expense of UV luminescence is observed after sample sintering at 800 and 1000 centigrade. The positron annihilation lifetime spectroscopy (PALS) is applied in order to study the thermally induced evolution of defects. The lifetime components show a step-like dependence on the thermal treatment, but do not follow exactly the variation in crystallographic phases and only vaguely follow differences in photoluminescence. The positron data indicate therefore some additional structural and/or defect changes. The possible origin of green luminescence from ZnO pellets is discussed.
    Źródło:
    Nukleonika; 2013, 58, 1; 189-194
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Positron annihilation studies of mesoporous iron modified MCM-41 silica
    Autorzy:
    Wiertel, M.
    Surowiec, Z.
    Budzyński, M.
    Gac, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/147950.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    iron
    MCM-41 silica mesoporous materials
    N2 sorption
    positron annihilation
    positron lifetime spectra
    Opis:
    MCM-41 silica materials modified by iron incorporation in the stage of its synthesis were investigated. The aim of the studies was determination of the nature of iron species and the influence of its content on the structural changes of materials and following the changes of their properties. For this purpose, the N2 sorption/desorption method and positron annihilation lifetime spectroscopy (PALS) were used. Disappearance of the longest-lived ortho-positronium (o-Ps) component (tau5) present in the PALS spectra of the initial MCM-41 material in the spectra of Fe-modified MCM-41 measured in vacuum is a result of a strong chemical o-Ps quenching and/or the Ps inhibition mechanism. Filling of pores by air or N2 at ambient pressure causes reappearance of the (tau5) component with lifetime shortened in comparison to that observed in vacuum for pure MCM-41 to the extent which can be explained by usual paramagnetic quenching in air. In contrary to the tendency observed for (tau5) lifetime which is practically independent of Fe content, the relevant intensity I5 monotonically decreases. This fact suggests that only inhibition of Ps formation occurs for the samples in air. Observed anti-quenching effect of air seems to be a result of competition of two processes : neutralization of surface active centres acting as inhibitors and considerably weaker paramagnetic quenching by O2 molecules.
    Źródło:
    Nukleonika; 2013, 58, 1; 245-250
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Porosity structure in photon active glasses
    Autorzy:
    Jasińska, B.
    Śniegocka, M.
    Reisfeld, R.
    Zigansky, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/147953.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    glass
    ortho-positronium (o-Ps)
    porosity
    positron annihilation lifetime spectroscopy (PALS)
    sol-gel technique
    Opis:
    Two kinds of photon active glasses were investigated using positron annihilation lifetime spectroscopy (PALS). Both kinds of glasses were prepared using a sol-gel technique, doped by complex of ruthenium tris bipyridyl chloride. Glasses differed from the initial matrix: the first one was prepared using silicon oxide while the second one - zircon oxide. The ortho-positronium (o-Ps) lifetime and intensities were determined from lifetime spectra. Different porosity structure concluded from PALS measurements was found in both cases. In the silica based glasses small free volumes (angstrom size) and pores (from 1 to 10 nm) existed in the material. On the contrary, in zirconia based glasses small intermolecular voids were produced in the structure only, independently of the way of material preparation.
    Źródło:
    Nukleonika; 2013, 58, 1; 241-244
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    PALS investigations of matrix Vycor glass doped with molecules of luminescent dye and silver nanoparticles. Discrepancies from the ETE model
    Autorzy:
    Gorgol, M.
    Jasińska, B.
    Reisfeld, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/147152.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    positron annihilation lifetime spectroscopy (PALS)
    porous glass
    lumogen dye ROT-305
    silver nanoparticles
    Vycor glass
    Opis:
    A thermal stability of three materials: undoped reference Vycor glass, glass filled with ROT-305 red dye, and silver nanoparticles was investigated by positron annihilation lifetime spectroscopy (PALS) in a broad temperature range (from 93 to 473 K). The attempt of pore size calculations from the ortho-positronium lifetime data was performed using the extended Tao-Eldrup (ETE) model. Below room temperature, a significant decrease in lifetime values of the longest-lived component was found for all the samples. This effect could not be explained by thermal shrinkage of the material and is probably caused by interaction of -Ps with a Vycor glass matrix. The greatest discrepancy from the ETE model predictions was observed for the reference glass. Doping the base material with dye molecules and silver nanoparticles resulted in similar small decrease in this discrepancy. After reheating the samples to the room temperature, the PALS components returned to the initial values. In the temperature range of 293–473 K, quite good agreement between PALS results and the ETE model predictions was observed for the reference glass and the glass incorporated with dye molecules. The observed small discrepancy in this range could possibly be partly explained by thermal expansion of the material. For the glass doped with silver nanoparticles, a significant change in PALS parameters was observed in the temperature range from 403 to 473 K.
    Źródło:
    Nukleonika; 2015, 60, No. 4, part 1; 717-720
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Positron annihilation lifetime spectroscopy study of roller burnished magnesium alloy
    Autorzy:
    Zaleski, R.
    Zaleski, K.
    Gorgol, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/146650.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    AZ91HP magnesium alloy
    defects
    positron lifetime annihilation spectroscopy (PALS)
    roller burnishing
    Vickers hardness test
    Opis:
    The effect of roller burnishing on Vickers’ hardness and positron lifetimes in the AZ91HP magnesium alloy was studied. The microhardness increases with an increase in the burnishing force and with a decrease in the feed. The comparison of various methods of analysis of positron annihilation lifetime (PAL) spectra allowed identification of two components, which are related to solute-vacancy complexes and vacancy clusters, respectively. It was found that the increase in microhardness was related to the increase in the concentration of vacancy clusters.
    Źródło:
    Nukleonika; 2015, 60, No. 4, part 1; 789-794
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-12 z 12

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