The use of ESR spectroscopy for the investigation of dosimetric properties of egg shells

Electron spin resonance (ESR) spectroscopy was used to investigate the dosimetric properties of chicken egg shells. The ESR spectra of the irradiated egg shell were found to have an asymmetric absorption characterized by a major resonance at g=2.0019 and a minor resonance at g_||=1.9980. The study was carried out on g=2.0019 signal because of the accuracy of measurements and the possibility of using it as ESR dosimeter. The activation energy (E), frequency factor (k₀) and mean-life (τ) were calculated to be 1.50±0.10 eV, 2×10¹³ s⁻¹ and (4.4±0.4)×10⁴ year respectively. Dose–response was investigated between dose ranges of 1 Gy and 10 kGy for ⁶⁰Co γ-rays. Dose–response was found to be appropriate for dosimetry in the range 3 Gy to 10 kGy. The lower limit of observable doses for egg shell sample was about 3 Gy. The other ESR dosimetric parameters of egg shell samples, fading characteristic, light effect, dose-rate dependence and energy dependence, have also been studied in detail. Apart from its non-tissue equivalence, egg shell has very good dosimetric properties with insignificant fading, light independence, linearity in dose–response (3 Gy–10 kGy), dose-rate independence and independence from energy above 500 keV. It suggests that egg shell may be used as a retrospective γ radiation dosimetry after nuclear accidents or other short accidental radiation events.     

The use of NMR for determination of new structures in irradiated TFE/PMVE fluoropolymers

The radiation chemistry of two TFE/PMVE copolymers with TFE mole fractions of 0.66 and 0.81 has been studied under vacuum using ⁶⁰Co γ-radiation over absorbed dose ranges up to 4.2 MGy. The radiolysis temperature was 313 K for both TFE/PMVE copolymers. New structure formation in the copolymers was identified by solid-state ¹⁹F NMR and the G-values for new chain ends of 2.1 and 0.5 and for branching sites of 0.9 and 0.2 have been obtained for the TFE/PMVE with TFE mole fractions of 0.66 and 0.81, respectively. The relative yields of –O–CF₃ and –CF₂–CF₃ chain ends were found to be proportional to the copolymer composition, but the yields of the –CF₂–CF₃ chain ends and –CF– branch points were not linearly related to the composition, rather they were correlated with the radical yields measured at 77 K.     

Radiation centre of institute of physical chemistry in Moscow

Radiation centre of the Institute of Physical Chemistry of Russian Academy of Sciences (Moscow) is described. It has four ⁶⁰Co γ-ray sources and four electron accelerators, three of them being linear ones. The brief consideration of researches and developments in radiation chemistry and radiation processing is conducted.     

Effect of γ irradiation on optical properties of Ce-doped phosphate and silicate scintillating glasses

A set of Ce³⁺ activated silicate- and phosphate-based scintillating glasses were submitted to γ irradiation in the ⁶⁰Co radioisotope source “Calliope” (ENEA-Casaccia in Rome, Italy) in the dose range between 1 and 250 Gy (3.7 Gy/h). The effect of ionising radiation was probed by transmission measurements performed before and after each irradiation on all analysed samples. From these data, the radiation-induced absorption coefficient was calculated, proportional to the density of colour centres induced by irradiation in the solid matrix. Results are discussed by taking into account the possible dependence of radiation hardness on the composition of glass matrix.     

Three-dimensional polymer gel dosimetry: basic physical properties of the dosimeter

This study concentrated on assessment of the basic physical properties of a polymer gel dosimeter evaluated by NMR. For this, BANG-2 type polymer gel was prepared. The dosimeters were irradiated by ⁶⁰Co gamma photons and by 4, 6 and 18 MV X-ray photons for doses in the range 0–50 Gy. The multi-echo CPMG sequence was used for the evaluation of T₂-relaxation times in the irradiated gel dosimeters. Dependence of 1/T₂ in terms of the following factors was studied: absorbed dose, energy of applied radiation, temperature during NMR evaluation, time between irradiation and NMR evaluation and strength of the magnetic field. An exponential dependence of the 1/T₂ response on absorbed dose in the range 0–50 Gy was observed, while in the range 0–10 Gy the data could be fitted by a linear function. This paper also describes the dependence of 1/T₂ response on: radiation energy, strength of magnetic field and time from irradiation of the dosimeters to NMR evaluation. Increase of gel dosimeter 1/T₂ response with the decrease of the temperature during NMR evaluation has been qantitatively described. The polymer gel dosimetry system used in this study proved that it is a reliable system for three-dimensional dose distribution measurement.     

Calorimetric study on the effect of Co γ-rays on the growth of microorganisms

Using a calorimeter equipped with 24 sample units, the heat evolution from growing Saccharomyces cerevisiae, Escherichia coli and spores of Bacillus pumilus and Bacillus stearothermophilus was detected in the form of growth thermograms. Irradiation with ⁶⁰Co γ-rays affected the growth pattern, which was used for a quantitative analysis of the effect on microorganisms. Irradiation of B. pumilus and B. stearothermophilus spores led to dose-dependent delays in growth, indicating a bactericidal effect. In case of ⁶⁰Co γ-irradiated S. cerevisiae, a dose-dependent reduction of the growth rate constant was observed together with the retardation in growth, indicating a combination of bactericidal and bacteriostatic effects. An equation to determine the number of survivors on the basis of the retardation in growth t and the growth rate constant μ was developed, which proved the opportunity to use the calorimetric technique in predictive microbiology.     

Threshold temperature for γ-ray detection in superheated drop detector

The γ-ray detection threshold temperatures of superheated drops of refrigerant liquid R-12 is presented here for the three γ-ray energies 59.54 keV (²⁴¹Am, 500 mCi), 662 keV (¹³⁷Cs, 32.5 mCi) and 1250 keV (⁶⁰Co, 0.45 mCi). Nucleation was detected with an active device by counting the number of drops vaporized per minute as a function of the temperature of the detector over a wide range. The results show that the threshold temperature for detection increases with the energy of the incident photons.     

Radiation resistance of GaAs–AlGaAs heterostructures doped with isovalent and rare-earth elements

When GaAs–Si and GaAs–AlGaAs heterostructures are exposed to γ-quanta, radiation stimulated ordering is observed. However, the gettering efficiency in such systems falls for layer widths more than 1 μm. For this reason we seek effective methods of radiation resistance improvement of materials in which one would expect point radiation defects to be gettered not only at defect boundaries, but also in the active layer volume.

S.i.GaAs–s.i.Al_xGa_1−xAs–nGaAs : Te heterostructures are presented with epitaxial layers (doped with Yb or undoped), obtained by means of LPE (liquid-phase epitaxy). The electron concentration in nGaAs was found to be (1–3)×10¹⁸ cm⁻³ for widths 1–3 μm. The samples were exposed to ⁶⁰Co γ-quanta with doses of 10⁵–10⁷ rad.

Investigations of irradiated samples by means of low-temperature (4.2 K) photoluminescence have shown considerable decrease of exciton halfwidth in the boundary spectra of nGaAs : Te : Yb epitaxial layers in comparison with nGaAs : Te layer spectra. This is caused by background impurity gettering which happens on the s.i.Al_xGa_1−xAs–nGaAs heteroboundaries as well as in deformed regions in the epitaxial layer volume. Formation of such regions is caused by the difference between the covalent radii of Yb atoms and GaAs lattice atoms. The maximum effect of radiation stimulated gettering of dopants in nGaAs epitaxial layers is observed for Yb concentrations which are equal to 10⁻⁴–10⁻⁵ atomic fractions in a solution-melt.

It is determined that the deformed regions in epitaxial layer volumes and heteroboundaries could be efficient drains for point radiation defects which form under radiation exposure. The investigations carried out showed that the doping of an epitaxial layers by rare-earth impurities provides considerable improvement in forming radiation resistant III–V materials.     

On the kinetics of polymer degradation in solution—XII. Radiolysis of poly(2,2,2-trichloroethyl methacrylate)

The title compound (PTCMA) was irradiated in O₂-free dioxane solution by ⁶⁰Co-γ-rays or by 100 nsec-pulses of 16 MeV electrons. At concentrations below ca 0.04 base mol/l, main-chain scission occurred as was concluded from the decrease of the light scattering intensity (LSI). G(S) = 3.7 ± 0.4 was independent of the polymer concentration and equal to G(S) observed with solid PTCMA. This result indicates that in dilute solution main-chain scission is induced by the direct action of radiation on the polymer. The free radical [presumably ---C(CH₃)---(CH₂)---] giving rise to main-chain scission has a lifetime of 2.6 msec. It reacts with ethane thiol (k = 6.6 × 10⁴M⁻¹sec⁻¹). At concentrations above 0.04 base mol/l, the polymer crosslinked (gel formation, increase of the LSI according to 2nd order kinetics). It is assumed that crosslinking is due to the combination of radicals of the type ---CH₂---C(CH₃)(COOCH₂CCl₂)--- formed via dissociative electron capture processes involving mainly electrons in spurs that otherwise recombine with parent ions. This conclusion was inferred from the finding that [(τ_1/2)₁]⁻¹ ∞ (c_polymer)²[(τ_1/2)₁): 1st half-life of LSI increase after the pulse, c_polymer: polymer concentration].     

Structural and theoretical studies of Xe(OChF5)2 and [XeOChF5][AsF6] (Ch = Se, Te)

The XeOSeF₅⁺ cation has been synthesized for the first time and characterized in solution by ¹⁹F, ⁷⁷Se and ¹²⁹Xe NMR spectroscopy and in the solid state by X-ray crystallography and Raman spectroscopy with AsF₆⁻ as its counter anion. The X-ray crystal structures of the tellurium analogue and of the Xe(OChF₅)₂ derivatives have also been determined: [XeOChF₅][AsF₆] crystallize in tetragonal systems, P4/n, a=6.1356(1) Å, c=13.8232(2) Å, V=520.383(14) Å³, Z=2 and R₁=0.0453 at −60°C (Te) and a=6.1195(7) Å, c=13.0315(2) Å, V=488.01(8) Å³, Z=2 and R₁=0.0730 at −113°C (Se); Xe(OTeF₅)₂ crystallizes in a monoclinic system, P2₁/c, a=10.289(2) Å, b=9.605(2) Å, c=10.478(2) Å, β=106.599(4)°, V=992.3(3) Å³, Z=4 and R₁=0.0680 at −127°C; Xe(OSeF₅)₂ crystallizes in a triclinic system, , a=8.3859(6) Å, c=12.0355(13) Å, V=732.98(11) Å³, Z=3 and R₁=0.0504 at −45°C. The energy minimized geometries and vibrational frequencies of the XeOChF₅⁺ cations and Xe(OChF₅)₂ were calculated using density functional theory, allowing for definitive assignments of their experimental vibrational spectra.     

An ESR study of the ·SiCl4 radical anion

Exposure of a dilute solution of SiCl₄ in adamantane to ⁶⁰Co γ-rays at 77 K gave anisotropic ESR features which are shown to be characteristic of SiCl⁻₄ anions with a trigonal bipyramidal structure.     

Practical results of Co production at RBMK-reactors

The paper presents practical results of ⁶⁰Co production in irradiation assemblies (IAs) in RBMK-1000 reactor during 1100 effective days of irradiation. Operational support of irradiation was performed by means of certified software system SAPFIR&RC-RBMK_RT. Integrity of IA in operating reactor was monitored by design system: no leaks in IAs were detected. Activity of ⁶⁰Co contained in each capsule was measured in the hot cell by comparison, using reference dosimeter with absorbed gamma-dose rate measurement uncertainty not more than ±3% at confidence probability P=0.95. Total amount of ⁶⁰Co produced was 2 MCi, average specific activity of ⁶⁰Co—52±7 Ci/g. Achievable specific activity of ⁶⁰Co in RBMK-reactor is 90±7 Ci/g and annual production capacity—about 8 MCi.     

Solid-state static Cu and P CP/MAS NMR, and liquid-state EXAFS studies on copper(I) O,O′-dialkyldithiophosphate cluster compounds: Formation of the copper(I) O,O′-di-iso-amyldithiophosphate cluster compound on the surface of synthetic chalcocite

Polycrystalline octa-nuclear copper(I) O,O′-di-i-propyl- and O,O′-di-i-amyldithiophosphate cluster compounds, {Cu₈[S₂P(OR)₂]₆(μ₈-S)} where R = ⁱPr and ⁱAm, were synthesized and characterized by ³¹P CP/MAS NMR at 8.46 T and static ⁶⁵Cu NMR at multiple magnetic field strengths (7.05, 9.4 and 14.1 T). The symmetries of the electronic environments around the P sites were estimated from the ³¹P chemical shift anisotropy (CSA) parameters, δ_aniso and η. Analyses of the ⁶⁵Cu chemical shift and quadrupolar splitting parameters for these compounds are presented with the data being compared to those for the analogous octa-nuclear cluster compounds with R = ⁿBu and ⁱBu. The ⁶⁵Cu transverse relaxation for the copper sites in {Cu₈[S₂P(OⁱPr)₂]₆(μ₈-S)} and {Cu₈[S₂P(OⁱAm)₂]₆(μ₈-S)} was found to be very different, with a relaxation time, T₂, of 590 μs (Gaussian) and 90 μs (exponential), respectively. The structures of {Cu₄[S₂P(OⁱPr)₂]₄} and {Cu₈[S₂P(OⁱPr)₂]₆(μ₈-S)} cluster compounds in the liquid- and the solid-state were studied by Cu K-edge EXAFS. The disulfide, [S₂P(OⁱAm)₂]₂, was obtained and characterized by ³¹P{¹H} NMR. The interactions of the disulfide and of the potassium O,O′-di-i-amyldithiophosphate salt with the surfaces of synthetic chalcocite (Cu₂S) were probed using solid-state ³¹P NMR spectroscopy and only the presence of copper(I) dithiophosphate species with the {Cu₈[S₂P(OⁱAm)₂]₆(μ₈-S)} structure was observed.     

Hydrothermal syntheses and crystal structures of bimetallic cluster complexes [{Cd(phen)2}2V4O12]·5H2O and [Ni(phen)3]2[V4O12]·17.5H2O

The hydrothermal reactions of vanadium oxide starting materials with divalent transition metal cations in the presence of nitrogen donor chelating ligands yield the bimetallic cluster complexes with the formulae [{Cd(phen₂)₂V₄O₁₂]·5H₂O (1) and [Ni(phen)₃]₂[V₄O₁₂]·17.5H₂O (2). Crystal data: C₄₈H₅₂Cd₂N₈O₂₂V₄ (1), triclinic. a=10.3366(10), b=11.320(3), c=13.268(3) Å, =103.888(17)°, β=92.256(15)°, γ=107.444(14)°, Z=1; C₇₂H₁₃₁N₁₂Ni₂O_29.5V₄ (2), triclinic. a=12.305(3), b=13.172(6), c=15.133(4), =79.05(3)°, β=76.09(2)°, γ=74.66(3)°, Z=1. Data were collected on a Siemens P4 four-circle diffractometer at 293 K in the range 1.59° <θ<26.02° and 2.01°<θ<25.01° using the ω-scan technique, respectively. The structure of 1 consists of a [V₄O₁₂]⁴⁻ cluster covalently attached to two {Cd(phen)₂}²⁺ fragments, in which the [V₄O₁₂]⁴⁻ cluster adopts a chair-like configuration. In the structure of 2, the [V₄O₁₂]⁴⁻ cluster is isolated. And the complex formed a layer structure via hydrogen bonds between the [V₄O₁₂]⁴⁻ unit and crystallization water molecules.     

Kinetic investigation of electronic energy transfer processes following the pulsed dye-laser generation of excited atomic barium, Ba[6s6p(P1)], in the presence of atomic strontium

The collisional behaviour of Ba[6s5d(³D_J)], 1.151 eV above the 6s²(¹S₀) electronic ground state, in the presence of atomic strontium, has been investigated in the ‘long-time domain' (ca. 100 μs–1 ms) following the pulsed dye-laser excitation of barium vapour at elevated temperature at λ = 553.5 nm (Ba[6s6p(¹P₁)] ← Ba[6s²(¹S₀)]. Ba(³D_J) is subsequently produced from the short-lived ¹P₁ state (τ_e = 8.37 ± 0.38 ns) by a number of radiative and collisional processes. It may then be monitored in the ‘long-time domain' by atomic spectroscopic marker methods involving either collisional activation of Ba(³D_J) by Ba(¹S₀) and He buffer gas to yield Ba[6s6p(³P_J)] with subsequent emission from the ³P₁ state (τ_e = 1.2 ± 0.1 μs): Ba[6s6p(³P₁)] → Ba[6s²(¹S₀)] + hv (λ = 791.1 nm). Alternatively, emission from Ba(¹P₁) may be monitored at long times following the generation of this short-lived state by energy pooling following self-annihilation of Ba(³D_J) + Ba(³D_J) from Ba[6s6p(¹P₁)] → Ba[6s²(¹S₀)] + hv (λ = 553.5 nm). The generation of Ba(³D_J) in the presence of atomic strontium yields emission in the long-time domain from Sr[5s5p(³P₁)] (τ_e = 19.6 μs): Sr[5s5p(³P₁)] → Sr[5s²(¹S₀)]  + hv (λ = 689.3 nm). Whilst the decay profiles at short times are complex in form, at long times all these atomic profiles show first-order kinetic removal with the decay coefficients for λ = 791.1 nm, 689.3 nm and 553.5 nm emissions in the ratio 1 : 2 : 2, consistent with overall third-order activation of the form: Ba(³D_J) + Ba(³D_J) + Sr(¹S₀) → Sr(³P_J) + 2Ba(¹S₀). The mechanism is modelled in detail, including measurement of integrated emission intensities, yielding kinetic data for fundamental collisional processes. The overall rate constant for the third-order collisional activation of Sr[5s5p(³P_J])from 2Ba[6s5d(³D_J)] + Sr[5s²(¹S₀)] takes the upper limit of 5.8 × 10⁻²⁷ cm⁶ atom⁻² s⁻¹ (T = 900 K). The rate constant for the two body collisional quenching of Ba[6s5d(³D_J)] by ground state atomic strontium, Sr[5s²(¹S₀)], is found to be (2.0 ± 0.1) × 10⁻¹² cm³ atom⁻¹ s⁻¹ (T = 900 K).     

Transients and cooperative action of β-carotene, vitamin E and C in biological systems in vitro under irradiation

Using N^•₃ species as specific electron acceptor a defined ascorbate radical: AH^•↔A^•−+H⁺ (λ_max=360 nm, =3400 dm³ mol⁻¹ cm⁻¹) is observed. The attack of DMSO^•+ on vit.E results in a vit.E^• radical (k=1×10⁹ dm³ mol⁻¹ s⁻¹; λ_max=425 nm, =2400 dm³ mol⁻¹ cm⁻¹; 2k=4.7×10⁸ dm³ mol⁻¹ s⁻¹). Vit.E-acetate leads to the formation of a radical cation (vit.E-ac^•+). β-carotene reacts also with DMSO^•+ forming a radical cation, β-car^•+ (k=1.75×10⁸ dm³ mol⁻¹ s⁻¹; λ_max=942 nm, =14 600 dm³ mol⁻¹ cm⁻¹), which probably leads to the formation of a dimer radical cation, (β-car)^•+₂ (k=2.5×10⁷ dm³ mol⁻¹ s⁻¹).

Using E.coli bacteria (AB1157) as a model system in vitro it was found that all three vitamins are rather efficient radiation protecting agents. They can also increase the activity of cytostatica, e.g., mitomycin C (MMC), by electron transfer process. The mixture of vit.E-ac and β-car acts contradictory, but adding vit.C to it a strong cooperative enhancement of the MMC activity is observed once again. A relationship between the pulse radiolysis and the radiation biological data is found and discussed. A possible explanation of the previously reported trials concerning the role of vit.E and β-car on the increased occurence of lung and other types of cancer in smokers and drinkers is presented.     

Effects of gamma irradiation on the shoot length of Cicer seeds

The effects of radiation on the shoot and root lengths of germinated seedling of irradiated seeds of Cicer species, i.e. three kabuli types and four desi types of cultivated chickpea (Cicer arietinum Ladiz.) and 2 annual wild types (C. reticulatum Ladiz. and C. bijugum K.H. Rech.) were investigated. The seeds were irradiated with a ⁶⁰Co gamma source using 0, 200, 300 and 400 Gy doses at 1.66 kGy h⁻¹. At 200 Gy minor effects could be observed, but at 400 Gy an obvious depression of shoot length was observed. The kabuli types were more affected than the desi ones. The critical dose that prevented the shoot and root elongation varied among species and also ranged from genotypes to genotype within species.     

Effects of γ-irradiation on the lipid composition of inner sprout of garlic

The aim of this work was to evaluate the effects of a dose of 60.0 Gy of ⁶⁰Co γ-rays on the concentration and composition of lipids from the inner sprout of garlic cloves. 210 days after treatment, the levels of phospholipids, triacylglycerols and glycolipids were significantly reduced as a result of radiation. Levels of polyunsaturated fatty acids from these lipid fractions such as linoleic acids showed a similar trend of decrease. Irradiation also brought about an increase in diacylglycerols. Results are correlated with sprouting inhibition induced by γ-irradiation in garlic.     

Radiation effect studies on anticancer drugs, cyclophosphamide and doxorubicin for radiation sterilization

Two anticancer drugs, cyclophosphamide (CPH) and doxorubicin hydrochloride (DOXO), in powder form were exposed to a range of doses of ⁶⁰Co gamma and electron beam radiation to study the effects of ionizing radiation. Pharmacopoeia tests, discolouration, degradation products, effect of irradiation temperature and dose rate were investigated. CPH undergoes less than 2% degradation at 30 kGy. Chromatographic studies revealed formation of several trace level degradation products, discolouration and free radicals in the irradiated CPH. N,N-bis (2-chloroethyl) group in the molecule is particularly sensitive to radiation degradation. Irradiation to 5 kGy at low temperature (77 K) did not result in significant changes. DOXO was observed to be quite radiation resistant and did not undergo significant changes in its physico-chemical properties and degradation product profile. It can be radiation sterilized at normal sterilization dose of 25 kGy.     

Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.