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1
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Spin Transition Diagram of (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2] Studied by EPR

100%
Krupska A., Augustyniak-Jabłokow M., Yablokov V., Zelentsov V.
Acta Physica Polonica A
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2005
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vol. 108
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issue 2
291-296
EN
The high-spin↔ low-spin transition in (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2] was studied by EPR under hydrostatic pressure in the temperature range of 80-310 K. Two modifications of the low-spin complexes: low-pressure (LS-1) and high-pressure (LS-2) ones were revealed. The low-spin complexes are associated in domains. Under atmospheric pressure LS-1 appears or disappears at 220 K. The hydrostatic pressure shifts the transition to high temperatures. Above 410 MPa the abrupt changes of the g-factor and width Δ B of the EPR line are observed. The pressure-induced transition LS-1 ↔ LS-2 is almost independent of T up to 275 K where under pressure 420 MPa a triple point is observed. When the pressure has been decreased the reverse transition from LS-2 to LS-1 or to high spin phase (at T>260 K) occurs with a large hysteresis about 95 MPa.
2
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Characterisation of Porphyrin-TiO_2 Complex Using Raman Spectroscopy and Electron Paramagnetic Resonance

80%
Kotkowiak M., Manikowski H., Wieczorowski M., Dudkowiak A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
353-356
EN
A complex of meso-tetrakis (4-sulphonatophenyl) porphyrin covalently linked to titanium dioxide has been studied. Illumination of the complex with visible light was shown to result in formation of cationic radicals of the porphyrin. Shape and kinetics of the electron spin resonance signals were analysed which permitted calculation of spectroscopic parameters characterising the photoinduced process of the radicals formation. The dye-semiconductor complex was thoroughly characterised to indicate its possible applications.
3
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Analysis of Poly(2-Hydroxyethyl~Methacrylate)-co- Poly(4-Vinyl Pyridine) Copolymers [COP2,4] Irradiated: an EPR study

80%
Ceylan Y., Yumurtaci Aydogmus H., Usta K., Usta A., Ceylan N., Yilmaz H.
Acta Physica Polonica A
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2016
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vol. 130
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issue 1
167-171
EN
Poly(2-hydroxyethyl methacrylate)-co-poly(4-vinyl pyridine) and poly(HEMA)-co-poly-(4-VP) copolymers were synthesized by free radical polymerization. K₂S₂O₈ was used as an initiator. Chain lengths of the copolymer was changed by varying the monomer/initiator ratio. These polymers have molarites of 2.6 and 2.1 respectively and are called COP2 and COP4. The samples were exposed to gamma rays at room temperature. After irradiation, the EPR spectra of COP2 and COP4 were recorded between 120 K and 450 K. From the temperature dependence of the line intensity, it was concluded that unpaired spin concentration in the irradiated samples has been changing with temperature. A theoretical study, presented in this report, was aimed to test success of the machine learning methods and to select the best learning method.
4
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An EPR Study on Radiation-Induced 2-(piperidin-1-ylmethyl)phenol Single Crystal

80%
Usta K., Ceylan Y., Usta A., Ceylan N., Aras E.
Acta Physica Polonica A
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2016
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vol. 130
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issue 1
178-180
EN
For the assessment of irradiation influence on 2-(piperidin-1-ylmethyl)phenol single crystals (C₁₂H₁₇NO), electron paramagnetic resonance measurements were carried out on the samples exposed to ⁶⁰Co radiation at dose values of 22.8, 45.6 and 68.4 kGy at room temperature. Electron paramagnetic resonance signals were not observed in non-irradiated sample and in samples irradiated at dose values of 22.8 and 45.6 kGy. The electron paramagnetic resonance measurements were performed on the single crystals. This irradiated single crystal was rotated in steps of 10°. One type of radical center was found. The average values of g and hyperfine constant of the detected radiation damage center were calculated from experimental spectra as follows: g=2.0052, A_{H} = 0.74 mT.
5
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An ESR Study on 2,4 Diaminotoluene Exposed to Gamma Rays and Application of Machine Learning

80%
Ceylan Y., Usta K., Yumurtaci Aydogmus H., Usta A., Ceylan N., Aras E.
Acta Physica Polonica A
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2016
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vol. 130
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issue 1
184-187
EN
The polycrystals of 2,4 diaminotoluene were produced by slow evaporation of solvent. The polycrystalline samples were exposed to ⁶⁰Co gamma rays with dose rate of 0.950 kGy/h, at room temperature, for 12, 24, 48, and 72 hours. The electron paramagnetic resonance measurements were carried out on these samples in the temperature range between 298 K and 400 K. No electron paramagnetic resonance signal was observed in the samples irradiated for 12, 24, 48 hours. Two types of radicals were detected using ESR spectrometer in the sample irradiated for 72 h. These radiation damage centers were called RI and RII. The average values of g and the hyperfine coupling constant were calculated. This study also investigates the potential usage of machine learning methods and aims to test the success of these methods and to select the best method.
6
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Comparative Study of Influences of Gamma Rays on Calix[4]Arene and 25,27-di(4-Nitrobenzyl)-26,28-Dihydroxycalix[4]Arene: EPR Study

80%
Ceylan Y., Usta K., Ceylan N., Usta A., Koc Y.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
1211-1213
EN
In the present study, calix[4]arene and its derivate 25,27-di(4-nitrobenzyl)-26,28-dihydroxycalix[4]arene were irradiated for 72 hours by ⁶⁰Co gamma rays at dose rate of 0.720 kGy/h. These irradiated samples were analyzed by EPR method and it was found that one type of radical was produced in calix[4]arene, and two type of radicals were produced in 25,27-di(4-nitrobenzyl)-26,28-dihydroxycalix[4]arene. The measurements were performed in the temperature range of 273-400 K using x-band EPR spectrometer. It was observed that the spectra, obtained from two samples, have very weak temperature dependence. Hyperfine and g parameters were calculated for two samples.
7
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Paramagnetic Centres in Oxidised Coal

80%
Najder-Kozdrowska L., Samoilova R., Kappl R., Hüttermann J., Więckowski A.
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issue 3
475-479
EN
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.
8
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In Vitro Analysis of AHPlus and MM-Seal by ESR and Thermoanalytical Methods

80%
Ceylan Y., Usta A., Usta K., Kont Cobankara F., Yildirim C., Birey M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2B
B-479-B-482
EN
The free radicals and their concentration in resin materials may impact biocompatibility and polymerization properties of dental materials. The aim of this study was to determine whether there are free radicals and to obtain useful information about thermal stability of materials using electron spin resonance (ESR) spectroscopy, TGA (Thermogravimetry Analysis) and DTA (Differential Thermal Analysis) methods. Epoxy resin-based sealers AHPlus and MM-Seal samples, freshly mixed and set, were prepared to be analysed with ESR and thermal methods. The free radicals were found in dental materials. As radical concentration in AHPlus have changed very slowly, the concentration in MM-Seal have decreased dramatically. Also, MM-Seal was found to decompose in three steps with the increasing temperature, while decomposition of the AHPlus occurred in two steps.
9
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Evaluation of Antioxidant Activity, Phytochemicals and ESR Analysis of Lavandula Stoechas

80%
Ceylan Y., Usta K., Usta A., Maltas E., Yildiz S.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2B
B-483-B-487
EN
The antioxidant activity of phytochemicals and of the methanolic extract of Lavandula stoechas was evaluated by β-carotene-linoleate bleaching, DPPH radical scavenging, ferric reducing/antioxidant power (FRAP). The obtained results were compared with antioxidant activities of synthetic antioxidants, such as BHT and BHA. The highest antioxidant activity of the extract was observed by DPPH radical scavenging assay, which was 84.45±5.1% at 1 mg ml¯¹. Rutin, rosmarinic acid, and caffeic acid were main phenolics in the extract. The total phenolic content of the methanolic extract of Lavandula stoechas was found to be 105.5±2.7 mg gallic acid equivalent (GAE). Electron spin resonance (ESR) measurements were also performed on the samples. Free radicals were determined by ESR method. g value was found to be 2.0034 for the Lavandula stoechas; 2.0052 for quercetin.
10
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High-Pressure EPR Study of Spin Molecular Bistability in Li[Fe(Th-5Cl-Sa)_2]

80%
Krupska A.
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vol. 126
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issue 3
790-795
EN
The spin transitions in Li[Fe(Th-5Cl-Sa)_2] were studied by EPR under hydrostatic pressure in the temperature range 80-332 K. The structural changes in the complex anion induced by the pressure above 350 MPa (when LS-2 phase appears) are observed, which are manifested in abrupt changes in g_{⊥} factor and linewidth ΔB_{⊥} of the low-spin phase LS. It is also manifested in the change in the shape of EPR spectrum. The high-spin ↔ low-spin transition HS ↔ LS shows hysteresis whose width is constant up to about 265 K and then rapidly increases. The spin phase diagram studied shows a large similarity to the phase diagram of (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2], which means that characteristics of the transition depend mainly on complex anion, not on cation. The hysteresis indicates on a cooperative character of the spin transition and on grouping of the complexes in domains.
11
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Content available

Field Dependent Electron and Quadrupole Spin Relaxation: A Unified Treatment

70%
Kruk D.
Acta Physica Polonica A
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2007
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vol. 111
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issue 2
215-238
EN
This article reviews recent theoretical treatments of field dependent relaxation processes in complex systems containing mutually coupled dipolar, quadrupole, and electron spins. The presented approaches are based on an analogy between the Hamiltonian formalisms for quadrupole and zero field splitting interactions. Limitations of the presented treatments, resulting from the validity conditions of the second-order perturbation theory are discussed in detail.
12
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Groups of Paramagnetic Centres in Reduced and Methylated Low Rank Coal

70%
Pilawa B., Wachowska H., Kozłowski M., Więckowski A., Najder-Kozdrowska L.
Acta Physica Polonica A
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2015
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vol. 128
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issue 3
264-267
EN
Low rank Illinois No. 6 coal was studied by electron paramagnetic resonance EPR spectroscopy. The parameters of EPR spectra (spectroscopic splitting factors g, linewidths ΔB_{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.
13
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EMR Data on Mn(III; S=2) Ions in MnTPPCl Complex Modelled by Microscopic Spin Hamiltonian Approach

61%
Tadyszak K., Rudowicz C.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
15-19
EN
The electron magnetic resonance data on high-spin (S =2) manganese(III) 3d⁴ ion in tetraphenylporphyrinato chloride complex (MnTPPCl) obtained by high-frequency techniques are reanalysed. Preliminary results of semiempirical modeling of the spin Hamiltonian parameters for Mn(III) in MnTPPCl are presented. The microscopic spin Hamiltonian approach is utilized to predict the zero-field splitting and the Zeeman electronic parameters. It is found that for Mn(III) ions in MnTPPCl matching the experimental spin Hamiltonian parameters and the theoretical ones based on the ligand-field energy levels (Δ_{i}) within the ⁵D multiplet only may not be suitable for this system. Contributions due to the levels arising from the higher-lying ³H multiplet need to be taken into account in order to determine the reasonable values of microscopic parameters describing Mn(III) ions in MnTPPCl.
14
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EPR Characteristics of Activated Carbon for Hydrogen Production by the Thermo-Catalytic Decomposition of Methane

61%
Więckowski A., Najder-Kozdrowska L., Rechnia P., Malaika A., Krzyżyńska B., Kozłowski M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 3
701-704
EN
The electron paramagnetic resonance (EPR) method was used to characterize samples of activated coal before and after reactions of the catalytic decomposition of methane and ethanol at temperatures of 1023 K (750°C), 1123 K (850°C) and 1223 K (950°C). The EPR parameters: spectroscopic splitting factor g, peak-to-peak linewidth ΔBₚₚ, and spin concentration c were measured. During the ethanol-assisted catalytic decomposition of methane carbon-located-spin radicals are partially transformed into oxygen-located-spin radicals.
15
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Comparative Analysis of Experimental and Theoretical Zero-Field Splitting and Zeeman Electronic Parameters for Fe²⁺ Ions in FeX₂·4H₂O (X = F, Cl, Br, I) and [Fe(H₂O)₆](NH₄)₂(SO₄)₂

61%
Zając M., Rudowicz C.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
19-23
EN
Spectroscopic and magnetic properties of Fe²⁺ (3d⁶; S=2) ions at orthorhombic sites in FeX₂·4H₂O (X = F, Cl, Br, I) crystals are compared with those in [Fe(H₂O)₆](NH₄)₂(SO₄)₂ (FASH). The microscopic spin Hamiltonian modeling utilizing the package MSH/VBA enables prediction of the zero-field splitting parameters and the Zeeman electronic ones. Wide ranges of values of the microscopic parameters, i.e. the spin-orbit (λ), spin-spin (ρ) coupling constants, and the crystal-field (ligand-field) energy levels (Δp_{i}) within the ⁵D multiplet are considered to establish the dependence of the zero-field splitting parameters b_{k}^{q} (in the Stevens notation) and the Zeeman factors g_{i} on λ, ρ, and Δp_{i}. By matching the theoretical spin Hamiltonian parameters and the experimental ones measured by EMR, the suitable values of λ, ρ, and Δp_{i} are determined. The novel aspect is prediction of the fourth-rank zero-field splitting parameters and the ρ (spin-spin)-related contributions, not considered in previous studies. The MSH predictions provide guidance for high-magnetic field and high-frequency EMR measurements.
16
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Optimization of Antioxidant Properties of Creams with Berry Extracts by Artificial Neural Networks

61%
Makarova K., Zawada K., Wagner D., Skowyra J.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
44-51
EN
Oxidative stress and the excess of free radicals accelerate the ageing process of human skin. The application of skin cream with antioxidant compounds could reduce the damage caused by free radicals. In this work we studied two types of skin creams with extracts from aronia (Aronia melanocarpa), elderberry (Sambucus nigra) and bilberry (Vaccinium myrtillus) because of their high content of anthocyanins, i.e. strong natural antioxidants. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability of the skin creams with berry extracts were studied with ESR spectroscopy. The artificial neural networks were applied to optimize the berry extract concentration and storage time for oil-in-water and water-in-oil creams. Based on experimental results chokeberry and elderberry extracts in oil-in-water cream base revealed higher DPPH radical scavenging ability than in the corresponding water-in-oil. Artificial neural networks predicts maxima of DPPH radical scavenging for 1-week stored elderberry (2.23 mg DPPH/g) and 1-week stored chokeberry (5.84 mg DPPH/g) and bilberry (5.26 mg DPPH/g) 0.76% extracts in oil-in-water creams. The maxima of DPPH radical scavenging for water-in-oil creams were predicted for 6-week stored 0.8% aronia extract, freshly prepared 0.76% bilberry extract and 1-week stored 0.56% elderberry extract. The artificial neural networks predicted values are in good agreement with the experimental values. DPPH-EPR could be combined with artificial neural networks to optimize the extract concentration, and the type of cream base as well as to predict the effect of storage based on a limited number of experiments and samples.
17
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EPR Study of Gamma Irradiated Cholestanone Single Crystal

41%
Caliskan B.
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vol. 125
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issue 1
135-138
EN
Cholestanone (C_{27}H_{46}O) single crystals were irradiated with ^{60}Co-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 ĊHCH_2 CH_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.
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