Wyniki wyszukiwania - BazTech

1

Multifrequency EPR study on radiation induced centers in calcium carbonates labeled with 13C

Sadło J., Bugaj A., Strzelczak G., Sterniczuk M., Jaegermann Z.

Nukleonika

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2015

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Vol. 60, No. 3, part 1

429--434

EN

In calcite and aragonite, γ-irradiated at 77 K, several paramagnetic centers were generated and detected by EPR spectroscopy; in calcite, CO3 – (orthorhombic symmetry, bulk and bonded to surface), CO3 3–, NO3 2–, O3 –, and in aragonite CO2 – (isotropic and orthorhombic symmetry) depending on the type of calcium carbonate used. For calcium carbonates enriched with 13C more detailed information about the formed radicals was possible to be obtained. In both natural (white coral) and synthetic aragonite the same radicals were identifi ed with main differences in the properties of CO2 – radicals. An application of Q-band EPR allowed to avoid the signals overlap giving the characteristics of radical anisotropy.

2

EPR study of γ-irradiated feather keratin and human fingernails concerning retrospective dose assessment

Strzelczak G., Sterniczuk M., Sadło J., Kowalska M., Michalik J.

Nukleonika

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2013

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Vol. 58, No. 4

505--509

EN

In this paper we report the results of comparative EPR studies on free radicals generated in γ-irradiated powder samples of feather keratin powder and human fingernails. In degassed samples of both materials irradiated at 77 K the major component of EPR spectrum represents sulphur-centred radicals in cysteine residues. It quickly decays after air admission at room temperature while a singlet assigned to semiquinone melanin radicals remains the only one seen. The singlet recorded with fingernails decays slowly at room temperature and might be potentially useful for dose assessment by EPR. The advantages and limitations of fingernails EPR dosimetry are discussed.

3

X- and Q-band EPR study on dosimetric biomaterials

Strzelczak G., Sadło J., Michalik J.

Nukleonika

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2009

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Vol. 54, No. 4

247-250

EN

Electron paramagnetic resonance (EPR) spectroscopy (X- and Q-band) was used for identification of stable radicals in: compact bone powder, shell of arcidae mollusc and crystalline alanine. The aim of our investigation was to analyze the complex EPR spectra of these materials and to identify paramagnetic species contributing to it. The most successful results were obtained in the EPR study (X- and Q-band) on deproteinized and irradiated bone powder and arcidae shell at room temperature.

4

EPR study on biominerals as materials for retrospective dosimetry

Sadło J., Michalik J., Stachowicz W., Strzelczak G., Dziedzic-Gocławska A., Ostrowski K.

Nukleonika

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2006

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Vol. 51,suppl.1

95-100

EN

Stable paramagnetic species, induced by irradiation in biominerals, can be successfully used as an EPR dosimeter in numerous domains of scientific activity. In hydroxyapatite, the main mineral component of bones, the most stable signal is assigned to CO2 - ion radical. The signal is dose dependent and allows to determine the absorbed dose in a wide range till 20 kGy, with detection limit for tooth enamel below 1 Gy. The additive dose method was applied to EPR dating of archeological objects and EPR dosimetry after accidental overexposing during radiotherapy. It was found that the age of remains excavated from the “tomb of giants” belonging to Nuraghic culture developed in Sardinia island is about 3160 years old (1160 years BC). The dose obtained by patients during the accident at the Białystok Oncological Center was evaluated at about 75 Gy. Searching for potential dosimeters among other biominerals shows that mollusc shells have very promising properties. The lowest dose detection limit was found for an Arcidae shell. Both fresh water and sea mollusc shells are useful to be used for dosimetry in the low dose range.

5

Electron Spin Resonance study of radiation-induced radicals in polycrystalline oligopeptides containing methionine

Strzelczak G., Bobrowski K., Kozubek H., Michalik J.

Nukleonika

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2000

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Vol. 45, nr 1

93-100

EN

The radicals formed on g-radiolysis of oligopeptides containing methionine and glycine residues in the polycrystalline state at 77 K and on subsequent warming over the temperature range of 77-293 K were identified using the electron spin resonance (ESR) technique. In all oligopeptides studied, anion peptide radicals and monomeric sulfur radical cations over the temperature range of 77-95 K and decarboxylation and deamination radicals over the temperature range of 180-250 K were detected. In addition, in oligopeptides containing adjacent methionyl residues, three-electron-bonded dimeric sulfur radical cations (S\S)+ were detected at 110 K. In oligopeptides containing N-terminal methionine residue, H-abstraction radicals in the side chain of methionine residue were observed over the temperature range of 180-250 K. H-abstraction radicals at the a-carbon of the C-terminal amino acid residue were detected at 293 K in most of oligopeptides studied, in contrast to Met-Gly-Met and Met-Gly-Met-Met peptides were H-abstraction radicals at the alfa-carbon of the internal glycine residue were obserwed.

6

Radiation effects in poly(ethylene terephthalate) - polypropylene composite materials

Sadło J., Bojarski J., Michalik J., Strzelczak G.

Polimery

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1999

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T. 44, nr 3

226-228

EN

Radiation-induced radicals in poly(ethylene terephthalate) (PET) and polypropylene (PP) and in their composites were studied by ESR. In pure PET, the radicals were not stabilized at room temperature but, in PET/PP composites (10-20% of PP), peroxy radicals were recorded at concentrations indicating the radical centers formed originally in PET units to be able to migrate to PP units where they become stabilized. Changes in polymer viscosity observed in the molten state proved degradation to be the major radiation effect.

PL

Napromieniowano kompozyty (80:20) i (90:10) PP-PET oraz czysty PP i PET wiązką elektronów 10 MeV (z akceleratora liniowego LAE 13/9) i wytworzone rodniki badano metodą EPR. W czystym PET rodniki nie ulegały stabilizacji w temperaturze pokojowej, natomiast w kompozytach stwierdzono obecność ustabilizowanych rodników nad tlenkowych. Ich stężenie wskazuje, że najpierw tworzą się one w łańcuchach PET, a następnie migrują do łańcuchów PP, gdzie ulegają stabilizacji. Zbadano lepkość polimerów w stanie stopionym; wyniki wskazują, że głównym efektem promieniowania jest degradacja polimerów.

7

Using bone powder for dosimetric system EPR response under the action of γ irradiation

Ziaie F., Stachowicz W., Strzelczak G., Al-Osaimi S.

Nukleonika

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1999

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Vol. 44, nr 4

603-608

EN

Two sets of samples of the bovine bone powder and α-l-alanine crystalline powder were irradiated in a 60Co source using the doses from 5 kGy up to 120 kGy while recorded signals were subsequently measured with the EPR spectrometer at room temperature in the air. Quantitative data related to the absorbed dose of radiation were collected. Dose versus EPR signal intensity curves for both kinds of samples were constructed and evaluated.

PL

W pracy poddano napromieniowaniu w źródle Co-60 dawkami od 5 kGy do 120 kGy dwa zestawy próbek, sproszkowaną kość wołową oraz sproszkowaną krystaliczną α-Ianinę, a następnie przeprowadzono na spektrometrze EPR pomiary ilościowe zarejestrowanych sygnałów w temperaturze pokojowej, przy dostępie powietrza. Zgromadzono ilościowe dane odnoszące się do absorbowanej dawki promieniowania. Wykreślono krzywe zależności dawka - intensywność sygnału dla obu rodzajów próbek oraz dokonano oceny uzyskanych wyników.

8

Radiation proceses in poly(ethylene terephthalate) composite materials

Sadło J., Bojarski J., Strzelczak G., Michalik J.

Nukleonika

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1999

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Vol. 44, nr 1

59-69

EN

The radiation - induced radicals in poly(ethylene terephthalate) - PET composite with polypropylene - PP and polyetherester KPEE have been studied by ESR spectroscopy. In pure PET matrix radicals are not stabilized at room temperature but in PET/PP composite (10-20% of PP) similary to pure PP matrix peroxy radicals are recorded at room temperature with the concentrations indicating that radicals formed originally in PET units are stabilized during migration along polymer chain by PP units enabling the formation of peroxy radicals. In contrast, in PET/KPEE composite materials the radical processes are the same as in PET homopolymers. The changes of polymer viscosity in melting state prove that polymer degradation is major radiation effect in the majority of composite materials.

PL

Przy użyciu spektroskopii Elektronowego Rezonansu Paramagnetycznego (EPR) badano inicjowane radiacyjnie rodniki w kompozytach polimerowych na bazie politereftalanu etylenu (PET) z domieszką polipropylenu (PP) lub kopolieteroestru (KPEE). W czystym PET wolne rodniki w temperaturze pokojowej nie stabilizują się, natomiast w kompozytach PET/PP zawierających 10 i 20% PP rejestruje się, podobnie jak w czystym PP, rodniki nadtlenkowe. Stężenie rodników w tych kompozytach jest większe niż procentowy udział polipropylenu w matrycy polimerowej. Wskazuje to, że rodniki powstające początkowo we fragmentach politereftalanowych migrują wzdłuż łańcuchów ulegając stabilizacji we fragmentach polipropylenowych w wyniku powstawania rodników nadtlenkowych. Efektu tego nie obserwuje się w kompozytach PET/KPEE, w których procesy rodnikowe przebiegają w ten sam sposób jak w homopolimerze PET. Na podstawie zmian lepkości polimerów w stanie stopionym stwierdzono, że w badanych polimerach głównym efektem radiacyjnym jest degradacja.