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    Wyświetlanie 1-9 z 9
    Tytuł:
    Some remarks on positron/positronium diffusion models
    Autorzy:
    Świątkowski, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/148428.pdf
    Data publikacji:
    2003
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    diffusion
    diffusion length
    positron
    positronium
    Opis:
    Positrons thermalized near the sample boundary (as well as Ps atoms formed in the sample) can reach the boundary as a result of diffusive movement. Observations of such effects as positron reemission or positron surface trapping as well as positronium emission allow one to calculate respective diffusion lengths. From the presented analysis it follows that some models used in such calculations give quite wrong results.
    Źródło:
    Nukleonika; 2003, 48, 3; 141-144
    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:
    New Porosimetric Method Based on the 3γ Annihilation Rate. Applications to Materials Science and Medical Imaging
    Autorzy:
    Jasińska, B.
    Zgardzińska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1033228.pdf
    Data publikacji:
    2017-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    positron annihilation
    positronium
    3γ annihilation
    porosity
    positron emission tomography
    medical imaging
    Opis:
    A new parameter δ based on 3γ annihilation is proposed. It describes the porosity of the materials containing small intermolecular voids below 1 nm. It can be applied to material investigation to compare changes in the material porosity depending on temperature or pressure as well as to study of ageing or manufacturing processes. Particularly it is dedicated to prepare the new imaging method and can be used during positron emission tomography diagnosis allowing determination the kind or stage of pathogenic alteration.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 5; 1616-1619
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Biodegradable polyester blend and copolyesters studied by positron annihilation and other methods
    Autorzy:
    Dębowska, M.
    Rudzińska-Girulska, J.
    Serwadczak, M.
    Kiersnowski, A.
    Pigłowski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/146301.pdf
    Data publikacji:
    2010
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    mixing of polymers
    polyesters
    transesterification
    positron annihilation
    positronium
    free volume
    Opis:
    Two polyesters, i.e. an aromatic one: poly(butylene terephthalate) – PBT and an aliphatic one: poly(ĺ- -caprolactone) – PCL were mixed in melt to obtain a biodegradable product. DSC, 1H NMR, SEM, WAXS, SAXS, BOD and PALS measurements were performed to study the homopolymers as well as their physical blend and copolyesters. The latter were obtained due to the transesterification reaction. Ortho-positronium (o-Ps) annihilation lifetimes were used to create the distributions of free volume. The progressive changes in probability density function of free volume, i.e. increase in large free volume holes contribution to the total free volume, appearing when going from the homopolymers to the blend and then to the copolyesters reflect the influence of: the addition of aliphatic polyester, the weight fraction of it in the composition and transesterification. The higher contribution of larger free volume holes corresponds well with the reduced crystallinity of compositions revealed in X-ray diffraction and the worsening of the regularity of structure of the macromolecules involved in formation of crystals, deduced from the 1H NMR.
    Źródło:
    Nukleonika; 2010, 55, 1; 57-64
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparison of the free volume sizes and shapes determined from crystallographic and PALS data
    Autorzy:
    Tydda, M.
    Jasińska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/146378.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    benzenediols
    free volume
    molecular crystals olanzapine
    positron annihilation
    positronium
    positronium diffusion coefficient
    Opis:
    Two different classes of molecular crystals were investigated. The first group was benzenediols, which are characterized by the same chemical composition but a different organization of their crystallographic structures; all of the compounds from this group have only one kind of free volumes. The second class was represented by olanzapine, which has more complex chemical composition and two kinds of free volumes in the structure. The o-Ps lifetime values determined from positron annihilation lifetime spectroscopy (PALS) measurements agree quite well with those calculated for sizes found from crystallographic data for benzenediols (agreement within 10% of the lifetime values). For olanzapine, a good agreement is observed in the case of cuboidal free volumes, while for the other kind of void, the agreement is less satisfactory. Positronium diffusion coefficient determined from o-Ps redistribution in olanzapine agrees with these found for polymers.
    Źródło:
    Nukleonika; 2015, 60, No. 4, part 1; 771-775
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Track Effects in Positronium Formation
    Autorzy:
    Stepanov, S.
    Byakov, V.
    Duplâtre, G.
    Stepanov, P.
    Bokov, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030026.pdf
    Data publikacji:
    2017-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    positron
    positronium
    annihilation
    ion-electron recombination
    solvation
    mobility
    external electric field
    track effects
    polar and nonpolar liquids
    Opis:
    We discuss some aspects important for interpretation of the Ps formation process in liquids and molecular media: (1) inhomogeneity of intratrack reactions and parameters of the e⁺ track, (2) final states of e⁺, its solvation in polar and nonpolar liquids, relation to e⁺ mobility, (3) quasi-neutrality of the e⁺ blob and its ambipolar outdiffusion, (4) appearance of the "in-blob" and "out-of-the-blob" positron fractions, and (5) electric field effect on Ps formation.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 5; 1461-1465
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Studies of unicellular microorganisms Saccharomyces cerevisiae by means of positron annihilation lifetime spectroscopy
    Autorzy:
    Kubicz, E.
    Jasińska, B.
    Zgardzińska, B.
    Bednarski, T.
    Białas, P.
    Czerwiński, E.
    Gajos, A.
    Gorgol, M.
    Kamińska, D.
    Kapłon, Ł.
    Kochanowski, A.
    Korcyl, G.
    Kowalski, P.
    Kozik, T.
    Krzemień, W.
    Niedźwiecki, S.
    Pałka, M.
    Raczyński, L.
    Rajfur, Z.
    Rudy, Z.
    Rundel, O.
    Sharma, N. G.
    Silarski, M.
    Słomski, A.
    Strzelecki, A.
    Wieczorek, A.
    Wiślicki, W.
    Zieliński, M.
    Moskal, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/147902.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    environmental scanning electron microscopy (ESEM)
    free volume
    inverted microscopy
    positron annihilation
    positronium
    yeasts
    Opis:
    Results of positron annihilation lifetime spectroscopy (PALS) and microscopic studies on simple microorganisms, brewing yeasts, are presented. Lifetime of ortho-positronium (o-Ps) were found to change from 2.4 to 2.9 ns (longer-lived component) for lyophilized and aqueous yeasts, respectively. Also hygroscopicity of yeasts in time was examined, allowing to check how water – the main component of the cell – affects PALS parameters, thus lifetime of o-Ps were found to change from 1.2 to 1.4 ns (shorter-lived component) for the dried yeasts. The time sufficient to hydrate the cells was found below 10 hours. In the presence of liquid water, an indication of reorganization of yeast in the molecular scale was observed. Microscopic images of the lyophilized, dried, and wet yeasts with best possible resolution were obtained using inverted microscopy (IM) and environmental scanning electron microscopy (ESEM) methods. As a result, visible changes to the surface of the cell me mbrane were observed in ESEM images.
    Źródło:
    Nukleonika; 2015, 60, No. 4, part 1; 749-753
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    PALS investigations of free volumes thermal expansion of J-PET plastic scintillator synthesized in polystyrene matrix
    Autorzy:
    Wieczorek, A.
    Zgardzińska, B.
    Jasińska, B.
    Gorgol, M.
    Bednarski, T.
    Białas, P.
    Czerwiński, E.
    Gajos, A.
    Kamińska, D.
    Kapłon, Ł.
    Kochanowski, A.
    Korcyl, G.
    Kowalski, P.
    Kozik, T.
    Krzemień, W.
    Kubicz, E.
    Niedźwiecki, S.
    Pałka, M.
    Raczyński, L.
    Rudy, Z.
    Rundel, O.
    Sharma, N. G.
    Silarski, M.
    Silarski, A.
    Strzelecki, A.
    Wiślicki, W.
    Zieliński, M.
    Moskal, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/147132.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    free volume
    positron annihilation
    polystyrene
    positronium
    scintillator
    Opis:
    The polystyrene doped with 2,5-diphenyloxazole as a primary fluor and 2-(4-styrylphenyl)benzoxazole as a wavelength shifter prepared as a plastic scintillator was investigated using positronium probe in wide range of temperatures from 123 to 423 K. Three structural transitions at 260, 283, and 370 K were found in the material. In the o-Ps intensity dependence on temperature, the significant hysteresis is observed. Heated to 370 K, the material exhibits the o-Ps intensity variations in time.
    Źródło:
    Nukleonika; 2015, 60, No. 4, part 1; 777-781
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Human tissue investigations using PALS technique - free radicals influence
    Autorzy:
    Jasińska, B.
    Zgardzińska, B.
    Chołubek, G.
    Pietrow, M.
    Gorgol, M.
    Wiktor, K.
    Wysogląd, K.
    Białas, P.
    Curceanu, C.
    Czerwiński, E.
    Dulski, K.
    Gajos, A.
    Głowacz, B.
    Hiesmayr, B.
    Jodłowska-Jędrych, B.
    Kamińska, D.
    Korcyl, G.
    Kowalski, P.
    Kozik, T.
    Krawczyk, N.
    Krzemień, W.
    Kubicz, E.
    Mohammed, Muhsin
    Pawlik-Niedźwiecka, M.
    Niedźwiecki, S.
    Pałka, M.
    Raczyński, L.
    Rudy, Z.
    Sharma, N.
    Sharma, S.
    Shopa, R.
    Silarski, M.
    Skurzok, M.
    Wieczorek, A.
    Wiktor, H.
    Wiślicki, W.
    Zieliński, M.
    Moskal, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1057941.pdf
    Data publikacji:
    2017-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    positron annihilation
    positronium
    free radicals
    tissues
    uterine leiomyomas
    Opis:
    The positron annihilation lifetime spectroscopy was applied to the samples of the human uterine leiomyomas and the normal myometrium tissues taken from the selected place of the uterus during a surgery. The method indicated differences in values of the measured positron annihilation lifetime spectroscopy parameters (lifetimes and intensities) between healthy and diseased tissue samples. The additional measurements were performed either in darkness or in presence of visible light which influenced the free radicals present in both kind of tissues and, as a result, made changes in free annihilation and o-Ps decay lifetime and intensity values.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 5; 1556-1558
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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