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    Wyświetlanie 1-9 z 9
    Tytuł:
    Effect of pH on Paramagnetic Centers in Cladosporium cladosporioides Melanin
    Autorzy:
    Pilawa, B.
    Buszman, E.
    Gondzik, A.
    Wilczyński, S.
    Zdybel, M.
    Witoszyńska, T.
    Wilczok, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043413.pdf
    Data publikacji:
    2005-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Hq
    76.30.Rn
    Opis:
    Paramagnetic centers in melanin existing in pigmented soil fungi Cladosporium cladosporioides cultured at acidic (4, 5, 6), neutral (7), and alkaline (8) pH were studied by EPR method. o-semiquinone free radicals (g: 2.0032-2.0040) concentration in melanin biopolymer increased for pH from 4 to 6, decreased at pH 7, and reached the maximum value at pH 8. It may be expected that melanin free radicals reactions with small molecules (metal ions, drugs) are the most effective at pH between 6 and 8. Slow spin-lattice relaxation processes exist in the all studied melanin samples.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 1; 147-150
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Paramagnetic Centers in DOPA-Melanin-Dihydrostreptomycin Complexes
    Autorzy:
    Buszman, E.
    Pilawa, B.
    Zdybel, M.
    Wrześniok, D.
    Grzegorczyk, A.
    Wilczok, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043624.pdf
    Data publikacji:
    2005-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Hq
    76.30.Rn
    Opis:
    DOPA-melanin-dihydrostreptomycin complexes with drug concentrations 1×10$\text{}^{-4}$-1×10$\text{}^{-2}$ M were examined by the use of electron paramagnetic resonance spectroscopy at X-band (9.3 GHz). Dihydrostreptomycin was chosen for studies, because this aminoglycoside antibiotic causes strong toxic effects in organism. It was stated that dihydrostreptomycin generates o-semiquinone free radicals with g=2.0038 in melanin. Free radicals formation increases with increase in the antibiotic concentration. Changes of EPR lines with microwave powers pointed out that slow spin-lattice relaxation processes exist in DOPA-melanin and in its complexes with dihydrostreptomycin. The measured EPR lines were homogeneously broadened.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 2; 353-356
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Multi-Component EPR Spectra of Coals with Different Carbon Content
    Autorzy:
    Pilawa, B.
    Więckowski, A. B.
    Pietrzak, R.
    Wachowska, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043651.pdf
    Data publikacji:
    2005-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Hq
    76.30.Rn
    Opis:
    EPR spectra of lignite"Mequinenza" (Spain) (62.3 wt% C) and Polish orthocoking coal (87.8 wt% C) were compared. The spectra were superpositions of broad Gaussian, broad Lorentzian 1, and narrow Lorentzian 3 lines. Concentration of paramagnetic centers - mainly delocalizedπ electrons - responsible for narrow Lorentzian 3 lines increases with increase in carbon content in coal. Coal units with slow and fast spin-lattice relaxation processes exist in the two studied samples. Slow spin-lattice interactions occur in simple aromatic coal units with broad Gaussian and Lorentzian 1 lines. Fast spin-lattice relaxation processes are characteristic of large aromatic units with narrow Lorentzian 3 lines.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 2; 403-407
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR Studies of Carbonized Cellulose - Oxygen Interactions
    Autorzy:
    Pilawa, B.
    Pietrzak, R.
    Wachowska, H.
    Babeł, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043418.pdf
    Data publikacji:
    2005-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Hq
    76.30.Rn
    Opis:
    EPR examination of cellulose carbonized at 400ºC and 600ºC has been performed. The aim of this work was to search a sample useful as the oximetric probe in biology and medicine. The higher paramagnetic centers concentration characterizes cellulose carbonized at 600ºC, which was found as the sensitive oximetric probe. Quasi-chemical bonds between cellulose molecules and paramagnetic O$\text{}_{2}$ molecules decrease paramagnetic centers concentration. A linear increase in paramagnetic centers concentration and a linear decrease in EPR linewidth with increasing time of sample evacuation were observed for cellulose carbonized at 600ºC. Oxygen affects spin-lattice interactions in carbonized cellulose.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 1; 151-154
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR Evidence for Thermally Excited Triplet States in Exinite, Vitrinite and Inertinite Separated from Bituminous Coal
    Autorzy:
    Słowik, G. P.
    Wojtowicz, W.
    Więckowski, A. B.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043436.pdf
    Data publikacji:
    2005-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Hq
    76.30.Rn
    87.64.Hd
    Opis:
    In this work we have made an electron spin resonance (EPR) study of macerals obtained from the lithotype clarain separated from Polish medium-rank coal (85.6 wt.% C). For three macerals:~exinite, vitrinite, and inertinite, the temperature dependence of intensity of EPR spectra in the temperature range of 100-373 K was investigated. The experimentally obtained EPR spectra of macerals were fitted by curves of the derivatives of the Gaussian and Lorentzian functions. The best fitting was obtained, when the experimental EPR spectra were assumed to be a superposition of three lines, for exinite and vitrinite - a broad Gaussian (G), a broad Lorentzian (L1) and a narrow Lorentzian (L3) line, but for inertinite of two lines - a narrow Lorentzian (L2) and a narrow Lorentzian (L3) line. The computer-assisted fitting has shown that each individual component line has similar values of resonance field, but different linewidths and amplitudes. The temperature dependence of line intensity I of the broad Gaussian (G) and narrow Lorentzian (L2 and L3) lines fulfils the Curie law in the form I=C/T or IT=C, whereas the broad Lorentzian (L1) line does not fulfil the Curie law. In the last case the temperature dependence of the Lorentzian (L1) component was fitted by the relation I=C/T+B/[T(3+exp(J/kT))] or IT=C+B/[3+exp(J/kT))], valid for thermally excited triplet states (S=1). For exinite and vitrinite the curves presenting the temperature dependence of the product IT versus temperature T were resolved into two curves, one for paramagnetic centres in the doublet state (S=1/2), and the other for paramagnetic centres in the thermally excited triplet state (S=1).
    Źródło:
    Acta Physica Polonica A; 2005, 108, 1; 171-176
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Triplet States in DOPA-Melanin and in Its Complexes with Kanamycin and Copper Cu(II) Ions
    Autorzy:
    Najder-Kozdrowska, L.
    Pilawa, B.
    Buszman, E.
    Więckowski, A.
    Świątkowska, L.
    Wrześniok, D.
    Wojtowicz, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/1535688.pdf
    Data publikacji:
    2010-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Hq
    76.30.Rn
    87.64.kh
    Opis:
    The mono- and biradical forms of DOPA-melanin (DOPA-eumelanin) were studied by EPR spectroscopy in 100-300 K temperature range. The existence of triplet states in DOPA-melanin was proved. The analysis of EPR spectra has shown that in DOPA-melanin and its complexes with kanamycin and $Cu^{2+}$ ions, two kinds of paramagnetic centres exist. The first of them are in doublet ground state with spin S = 1/2 and they obey the Curie law. The paramagnetic centres of the second group are in thermally excited triplet state with spin S = 1 and in this case the Curie law is not fulfilled.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 4; 613-618
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Paramagnetic Centres in Coal Macerals
    Autorzy:
    Słowik, G.
    Więckowski, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1536501.pdf
    Data publikacji:
    2010-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Hq
    76.30.Rn
    89.30.ag
    Opis:
    The electron paramagnetic resonance (EPR) study of coal macerals: exinite, vitrinite and inertinite separated from clarain of the Polish medium-rank coal with carbon content of 85.6 wt% C, were performed. Using the continuous microwave saturation technique (measurements at 223 K and 291 K), as a result of numerical analysis of recorded EPR spectra of exinite, vitrinite and inertinite, their multi-component structure was shown. The EPR spectra of exinite and vitrinite consist of three component lines: one Gaussian G and two Lorentzians: L1 and L3. The EPR spectra of inertinite consist of two narrow lines with Lorentzian line shape L2 and L3. Temperature measurements of studied coal macerals in the range 100-373 K were done. It was evidenced that, in group of paramagnetic centres responsible for Lorentzian L1 component line, paramagnetic centres with thermally excited triplet states (S = 1) exist. Existence of paramagnetic centres with thermally excited triplet states was not observed in inertinite.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 3; 507-510
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Paramagnetic Centres in Oxidised Coal
    Autorzy:
    Najder-Kozdrowska, L.
    Samoilova, R.
    Kappl, R.
    Hüttermann, J.
    Więckowski, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1536451.pdf
    Data publikacji:
    2010-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    33.35.+r
    61.66.Hq
    76.30.Rn
    89.30.ag
    Opis:
    This paper comprises the results obtained by continuous wave (cw)/pulse electron paramagnetic resonance spectroscopy for oxidised coals. The values of EPR linewidths are different for samples of coal treated by different chemical agents. The asymmetric EPR line shape indicates to complex composition of paramagnetic centres in coal. In coal oxidised by $HNO_3$ big changes of linewidth with temperature were observed. For all samples the spin-lattice relaxation time $T_1$ was determined by pulse EPR method. The correlation between used chemical agents and the value of $T_1$ was established.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 3; 475-479
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Groups of Paramagnetic Centres in Reduced and Methylated Low Rank Coal
    Autorzy:
    Pilawa, B.
    Wachowska, H.
    Kozłowski, M.
    Więckowski, A.
    Najder-Kozdrowska, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1401865.pdf
    Data publikacji:
    2015-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    33.35.+r
    61.66.Hq
    76.30.-v
    76.30.Rn
    89.30.ag
    Opis:
    Low rank Illinois No. 6 coal was studied by electron paramagnetic resonance EPR spectroscopy. The parameters of EPR spectra (spectroscopic splitting factors g, linewidths $\DeltaB_{pp}$, concentrations of paramagnetic centres N) were measured for row and chemically treated coal (demineralized, reduced and methylated samples). The multi-component structure of experimental spectra of this coal was proved. Two groups of paramagnetic centres responsible for broad Lorentzian 1 and narrow Lorentzian 2 lines exist in studied samples. Paramagnetic centres connected with component lines revealed different behaviour during chemical treatments.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 3; 264-267
    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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