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    Wyświetlanie 1-23 z 23
    Tytuł:
    High-Field EPR Spectroscopy on Transfer Proteins in Biological Action
    Autorzy:
    Möbius, K.
    Schnegg, A.
    Plato, M.
    Fuchs, M. R.
    Savitsky, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043547.pdf
    Data publikacji:
    2005-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.Rn
    Opis:
    In the last decade joint efforts of biologists, chemists, and physicists were made to understand the dominant factors determining specificity and directionality of transmembrane transfer processes in proteins. Characteristic examples of such factors are time varying specific H-bonding patterns and/or polarity effects of the microenvironment. In this overview, a few large paradigm biosystems are surveyed which have been explored lately in our laboratory. Taking advantage of the improved spectral and temporal resolution of high-frequency/high-field EPR at 95 GHz/3.4 T and 360 GHz/12.9 T, as compared to conventional X-band EPR (9.5 GHz/0.34 T), three transfer proteins in action are characterized with respect to structure and dynamics: (1) light-induced electron-transfer intermediates in wild-type and mutant reaction-centre proteins from photosynthetic bacteria Rhodobacter sphaeroides, (2) light-driven proton-transfer intermediates of site-specifically nitroxide spin-labelled mutants of bacteriorhodopsin proteins from Halobacterium salinarium, (3) refolding intermediates of site-specifically nitroxide spin-labelled mutants of the channel-forming protein domain of Colicin A bacterial toxin produced in Escherichia coli. The information obtained is complementary to that of protein crystallography, solid-state NMR, infrared and optical spectroscopy techniques. A unique strength of high-field EPR is particularly noteworthy: it can provide detailed information on transient intermediates of proteins in biological action. They can be observed and characterized while staying in their working states on biologically relevant time scales.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 2; 215-234
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Temperature Dependence ofĝ Tensor Anisotropy in (tm-p-PD):Chloranil, Charge Transfer Complex Powders
    Autorzy:
    Grampp, G.
    Sczaniecki, P. B.
    Żurek, S.
    Bednarski, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043604.pdf
    Data publikacji:
    2005-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.Rn
    Opis:
    The powders of 2,3,5,6-tetramethyl-p-phenylenediamine:chloranil charge transfer complex were studied by EPR. Numerical pack EPR-NMR was used to simulate and fit the X-band experimental data in the temperature range of 119-298 K. Very good agreement between the experiment and simulations permits to obtain the main values ofĝ matrix and plot their temperature dependence. At 150 K the main g values are g$\text{}_{xx}$=g$\text{}_{yy}$=2.0041 and g$\text{}_{zz}$=2.0015. g splitting factor varies significantly with temperature and shows an anomaly near 200 K. The signal narrows with the temperature increase, which agrees with the earlier observation. Individual component linewidth, used in the simulation is anisotropic and amounts to 0.1-0.8 mT; which is reasonable when compared with those measured earlier for the single crystals of p-phenylenediamine:chloranil, where the narrowest lines are quoted to be 18μT.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 2; 317-321
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Paramagnetic Resonance Study of Organic Radicals in Some Herbal Plants
    Autorzy:
    Krupska, A.
    Wojtowicz, E.
    Augustyniak-Jabłokow, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398973.pdf
    Data publikacji:
    2016-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.-v
    76.30.Rn
    Opis:
    In this work we show the impact of the roasting process on the properties of organic radicals in some herbal products added to cereal coffee. The EPR study shows the presence of radicals in dried herbal products, both natural and roasted. Changes in the relative intensity of the EPR signal and in the g-factor for unroasted and roasted plant material can be observed. This indicates to the recombination processes of radicals. Roasting process increases the number of radicals. The analysis of EPR spectra show that they consist of two Gaussian lines which indicate that there are at least two different kinds of radicals. The values of g-factor about 2 may be derived from a number of very different radicals. For this reason the identification of such radicals is not strictly possible.
    Źródło:
    Acta Physica Polonica A; 2016, 129, 6; 1201-1204
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Free Radicals in K and Rb Admixtured Fullerene C$\text{}_{60}$
    Autorzy:
    Stankowski, J.
    Kempiński, W.
    Byszewski, P.
    Trybuła, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1929831.pdf
    Data publikacji:
    1993-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.Rn
    74.70.Wz
    Opis:
    Molecules of C$\text{}_{60}$ form Van der Waals type crystals. The observations reported here concern EPR investigations of such C$\text{}_{60}$ samples with only a slight amount of Rb or K. Detected defects are (C$\text{}_{60}$)$\text{}^{+}$ or (C$\text{}_{60}$)$\text{}^{y-}$ ion-radicals. A hole (h) or trapped electron (t) are localized on one fullerene ball. In the case of potassium fullerites C$\text{}_{60}$:K the line shape of EPR signal was of the Dysonian form which is characteristic of conducting electrons in metal. The EPR lines of holes (C$\text{}_{60}$)$\text{}^{+}$ are characterized by g$\text{}_{h}$ ≥ g$\text{}_{0}$ whereas for electrons g$\text{}_{t}$ is below the value g$\text{}_{0}$ = 2.0023 characteristic of a free electron (g$\text{}_{t}$ ≤ g$\text{}_{0}$). The EPR linewidth 2ΔB$\text{}_{1s}^{h}$ of the (C$\text{}_{60}$)$\text{}^{+}$ weakly increased with decreasing temperature whereas the EPR linewidth attributed to the electron 2ΔB$\text{}^{t}$$\text{}_{1s}$ significantly decreases with decreasing temperature. The C$\text{}_{60}$:K sample reached superconducting phase below T$\text{}_{c}$ = 11 K which is significantly less than T$\text{}_{c}$ = 16.5 K observed for K$\text{}_{x}$C$\text{}_{60}$ where 2 ≤ x ≤ 4.
    Źródło:
    Acta Physica Polonica A; 1993, 84, 6; 1117-1123
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    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:
    Effect of Laser Radiation on Free Radicals in Human Cancer G361 Cells
    Autorzy:
    Latocha, M.
    Pilawa, B.
    Zdybel, M.
    Wilczok, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043652.pdf
    Data publikacji:
    2005-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.77.Hq
    76.30.Rn
    Opis:
    EPR spectroscopy was used to the examination of free radicals evolution in cancer G361 cells during photodynamic therapy. The cancer cells were cultured with photosensitizer ALA and irradiated with 635 nm light by laser. The number of cells was determined microscopically. The decrease in the cell number and the increase in free radicals, obtained for G361 cells cultured with ALA and irradiated with laser, were stronger than relevant changes for the cells which were only irradiated with laser. The studied melanotic cells susceptible for photodynamic therapy differ from the other melanotic SK human cancer cells by fast spin-lattice relaxation processes. Slow spin-lattice relaxation processes exist in the studied earlier non susceptible for photodynamic therapy SK cells.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 2; 409-412
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    ESR and Electron Spin Echo Studies of Spin-Lattice Relaxation of Hydrazinium Radical in Li(N$\text{}_{2}$H$\text{}_{5}$)O$\text{}_{4}$ Single Crystal
    Autorzy:
    Morawski, P.
    Hoffmann, S. K.
    Hilczer, W.
    Goslar, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1964224.pdf
    Data publikacji:
    1997-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.80.Ed
    76.30.Rn
    Opis:
    A hydrazinium ṄH-NH$\text{}_{3}^{+}$ radical was identified by ESR in γ-irradiated Li(N$\text{}_{2}$H$\text{}_{5}$)SO$\text{}_{4}$ single crystal. Unpaired electron is strongly localized on the nitrogen atom as compared to hydrazinium radicals in other crystals. Angular variations of the multicomponent ESR spectra and computer calculations gave the isotropic hyperfine coupling parameters (in mT): a$\text{}_{N1}$ = 1.93, a$\text{}_{N2}$ = 0.80, a$\text{}_{H1}$ = 2.50, a$\text{}_{H1'}$ = 0.48 (NH$\text{}_{3}$), and a$\text{}_{H2}$ = 1.40 (adjacent molecule). The radiation defects containing unpaired electrons do not influence much the protonic conductivity along the hydrazine molecule chains in the crystal. It confirms a tunelling mechanism of the conductivity activated by NH$\text{}_{2}$-group rotation. Spin-lattice relaxation time T$\text{}_{1}$ varies strongly with temperature in the range from 100 ms (10 K) to 90 μs (170 K) and is governed by spectral diffusion (1/T$\text{}_{1}$ ∝ T$\text{}^{2}$) and a Murphy-type mechanism (1/T$\text{}_{1}$ ∝ cosech(Δ/T)) with Δ = 150 cm$\text{}^{-1}$. A distribution of the spin-relaxation times was observed with temperature independent dispersion parameter β = 0.76.
    Źródło:
    Acta Physica Polonica A; 1997, 91, 6; 1121-1129
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR Investigations of Model Neuromelanins
    Autorzy:
    Skrzypek, D.
    Dzierżęga-Lęcznar, A.
    Ziółkowska, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2014422.pdf
    Data publikacji:
    2000-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    87.15.-v
    76.30.Rn
    Opis:
    The aim of this work was to compare free radical properties of some model neuromelanins obtained from dopamine and its mixture with 5-S-cysteinyldopamine in various molar ratios. The EPR method was used in these investigations; the samples were detected at X and K bands. The parameters of EPR spectra, free radicals concentrations in air and in vacuum, the influence of microwave power and temperature on intensity of resonance signals were measured.
    Źródło:
    Acta Physica Polonica A; 2000, 98, 5; 561-566
    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:
    NMR Relaxation Measurements as a Tool for Observation of Oxidative Processes
    Autorzy:
    Wierzuchowska, D.
    Skórski, L.
    Blicharska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398821.pdf
    Data publikacji:
    2016-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.60.-k
    76.90.+d
    76.30.Rn
    Opis:
    Water proton relaxation times, T₁ and T₂, were measured to assess the kinetics of the oxidative processes in biological samples. The oxidation in aqueous solutions of albumins was promoted by an addition of 3% hydrogen peroxide (H₂O₂). Immediately following this addition a sharp exponential decrease of both relaxation times was observed. As we confirmed experimentally, the time course of relaxation depended on several essential factors like structure and the concentration of proteins and also the presence of antioxidants added to solution. In experiments with protein solutions containing a small amount of ascorbic acid, after reaching a minimum, relaxation time increased towards the initial (pre-addition H₂O₂) values. We conclude that this T₁ and T₂ recovery is a consequence of the presence of antioxidants and may be used to evaluate its action. This study demonstrates that nuclear magnetic resonance (NMR) relaxation measurements may be useful in evaluating free radicals reactions and antioxidants capacity.
    Źródło:
    Acta Physica Polonica A; 2016, 129, 2; 226-228
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Observation of Antioxidants Activity using NMR Relaxation Measurements
    Autorzy:
    Wierzuchowska, D.
    Witek, M.
    Blicharska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030645.pdf
    Data publikacji:
    2018-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.60.-k
    76.90.+d
    76.30.Rn
    Opis:
    Formation of free radicals in biological solutions leads to the changes in water protons relaxation times. Therefore, NMR relaxation measurements were used to investigate kinetics of oxidation processes induced by the addition, in low amounts, of hydrogen peroxide (H_2O_2) to aqueous protein solution and to blood serum. The measured relaxation times were not stable over time because of the progressive formation of free radicals and their damaging action to the protein structure. The addition of antioxidants (ascorbic acid, gallic acid etc.) changed the relaxation time courses due to free radical scavenging. Similar time courses, thus anti-oxidant actions, were observed in various blood serum without antioxidant additive. Moreover, the observed kinetics of spin-lattice relaxation time (T_1) depended on several factors, such as: structure and concentration of protein solutions and activity and concentration of the added antioxidants.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 2; 289-291
    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:
    Wavelet Analysis in EPR Spectroscopy
    Autorzy:
    Drzewiecki, A.
    Sczaniecki, P. B.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043391.pdf
    Data publikacji:
    2005-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    07.05.Kf
    76.30.Rn
    82.50.Kx
    Opis:
    Possibility of application of wavelet analysis in EPR spectroscopy is investigated. Basic mathematics of the method is summarized, with emphasis on the relation between EPR experiment and physical interpretation of wavelet transform. The fact that first derivative of the Lorentzian function can be used as a base wavelet is employed and the specific rules of the interpretation of the final wavelet synthesis are identified. Analysis of a sample EPR spectrum of X-ray irradiated guanidinium aluminium sulphate hexahydrate crystal is given as an example. Set of parameters resulting from the wavelet analysis is subsequently used to reconstruct/synthesize the original EPR spectrum. The method involves an opportunity of eliminating unwanted components of the multicomponent spectra. Generally, the method may supplement other means of data analysis, in particular, in magnetic resonance.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 1; 73-79
    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:
    Influence of Microwave Power on EPR Signal of Melanin Radical and Copper(II) Ions in DOPA-Melanin Complexes
    Autorzy:
    Najder-Kozdrowska, L.
    Pilawa, B.
    Więckowski, A.
    Buszman, E.
    Wrześniok, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399522.pdf
    Data publikacji:
    2013-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.Rn
    87.80.Lg
    87.64.kh
    Opis:
    Electron paramagnetic resonance spectroscopy EPR was used for examination of microwave saturation in DOPA-melanin complexes with kanamycin and Cu(II) ions. The fast spin-lattice relaxation processes take place in system of paramagnetic metal ions. EPR signal of melanin radical saturated with growing of microwave power used during measurements. After adding Cu(II) ions a shortening of relaxation time is observed for EPR signal of melanin radical.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 1; 112-114
    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
    Tytuł:
    Anharmonic Effects in the Electron Spin-Lattice Relaxation of Radiation Defects in Potassium Selenate and Rochelle Salt Single Crystals
    Autorzy:
    Ivanshin, V. A.
    Kurkin, I. N.
    Brunner, W.
    Völkel, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1920523.pdf
    Data publikacji:
    1992-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.Rn
    61.80.Ed
    63.20.Mt
    77.80.-e
    Opis:
    An anharmonic character for the Raman processes of the electron spin-lattice relaxation of paramagnetic defect centres in γ-irradiated potassium selenate and Rochelle salt single crystals was observed at low temperatures.
    Źródło:
    Acta Physica Polonica A; 1992, 81, 3; 393-396
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    ESR Studies of Fast Electron Irradiated Ferroelectric Poly(Vinylidene Fluoride)
    Autorzy:
    Goslar, J.
    Hilczer, B.
    Smogór, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043394.pdf
    Data publikacji:
    2005-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.80.Fe
    61.82.Pv
    76.30.Rn
    77.84.Jd
    78.30.Jw
    Opis:
    Radiation-induced functionalization of ferroelectric poly(vinylidene fluoride) was studied by ESR spectroscopy. The samples were irradiated in the high vacuum of a Van de Graaff accelerator with 1.0 MeV and 1.5 MeV electrons at room temperature and the decay of free radicals was studied after transferring the samples into the air. The samples exhibit a multicomponent ESR spectrum that can be decomposed into: a large asymmetric signal in the centre related to peroxy radicals, a quintet with hyperfine splitting A$\text{}_{F}$ = 4.3 mT centred at g = 2.004, assigned to the in-chain radical (-CF$\text{}_{2}$-CH-CF$\text{}_{2}$-), and a triplet due to an end-chain (-CH$\text{}_{2}$) radical with A$\text{}_{H}$ = 1.6 mT and g = 2.009.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 1; 89-94
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR Study of Gamma Irradiated Cholestanone Single Crystal
    Autorzy:
    Caliskan, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1206732.pdf
    Data publikacji:
    2014-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    87.64.kh
    87.80.Lg
    61.72.Hh
    33.35.+r
    76.30.Rn
    32.10.Fn
    33.15.Pw
    71.18.+y
    76.30.-v
    61.82.Pv
    61.72.-y
    Opis:
    Cholestanone ($C_{27}H_{46}O$) single crystals were irradiated with ⁶⁰Co-γ rays at room temperature. The spectra were recorded for different orientations of the crystal in the magnetic field at 120 K using the EPR technique. Radiation damage center was attributed to $CHCH_2CH_2$ radical. The principal values of the hyperfine coupling tensor of the unpaired electron with the protons and the principal values of the g tensor were determined. The results were found to be in good agreement with the existing literature.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 1; 135-138
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-23 z 23

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