A new, simple and precise method for measuring cyclotron proton beam energies using the activity vs. depth profile of zinc-65 in a thick target of stacked copper foils.

The proton beam energy of an isochronous 18MeV cyclotron was determined using a novel version of the stacked copper-foils technique. This simple method used stacked foils of natural copper forming 'thick' targets to produce Zn radioisotopes by the well-documented (p,x) monitor-reactions. Primary beam energy was calculated using the (65)Zn activity vs. depth profile in the target, with the results obtained using (62)Zn and (63)Zn (as comparators) in close agreement. Results from separate measurements using foil thicknesses of 100, 75, 50 or 25µm to form the stacks also concurred closely. Energy was determined by iterative least-squares comparison of the normalized measured activity profile in a target-stack with the equivalent calculated normalized profile, using 'energy' as the regression variable. The technique exploits the uniqueness of the shape of the activity vs. depth profile of the monitor isotope in the target stack for a specified incident energy. The energy using (65)Zn activity profiles and 50-µm foils alone was 18.03±0.02 [SD] MeV (95%CI=17.98-18.08), and 18.06±0.12MeV (95%CI=18.02-18.10; NS) when combining results from all isotopes and foil thicknesses. When the beam energy was re-measured using (65)Zn and 50-µm foils only, following a major upgrade of the ion sources and nonmagnetic beam controls the results were 18.11±0.05MeV (95%CI=18.00-18.23; NS compared with 'before'). Since measurement of only one Zn monitor isotope is required to determine the normalized activity profile this indirect yet precise technique does not require a direct beam-current measurement or a gamma-spectroscopy efficiency calibrated with standard sources, though a characteristic photopeak must be identified. It has some advantages over published methods using the ratio of cross sections of monitor reactions, including the ability to determine energies across a broader range and without need for customized beam degraders.

Time-dependent transfer of 137Cs, 85Sr and 65Zn to earthworms in highly contaminated soils.

The transfer characteristics of (137)Cs, (85)Sr and (65)Zn to earthworms (Eisenia andrei) in soils with different amounts of the radionuclides have been investigated. The time-dependent whole-body concentration ratios (CR) were derived for worms in artificially contaminated soils with three different activity concentrations. Two parameters of a first order kinetic model, the equilibrium concentration ratio (CR(eq)) and the effective loss rate constant (k), were estimated by a comparison of experimental CR results with model predictions. The estimated CR(eq) (Bq/kg fresh worm per Bq/kg dry soil) ranged from 3.9 × 10(-4) to 4.1 × 10(-3) for (137)Cs, 1.39 × 10(-3) to 2.94 × 10(-2) for (85)Sr, and 1.39 × 10(-3) to 5.0 × 10(-2) for (65)Zn, and consistently decreased with increasing soil activity concentration but the trend was not statistically significant. The CR(eq) for (137)Cs was one to two orders of magnitude lower than previously reported CR(wo-soil) values (based on field data with much less contaminated soil), that for (85)Sr was comparable with other reported values and for (65)Zn was less two to three orders of magnitude lower than CR(wo-soil) values for stable zinc. The estimated k (d(-1)) values ranged from 9 × 10(-2) to 1.4 × 10(-1) for (137)Cs, 7 × 10(-2) to 2 × 10(-1) for (85)Sr, and 6 × 10(-2) to 1.8 × 10(-1) for (65)Zn, and did not show a relationship with soil activity concentration. The effect of CR(eq) on the total dose rate was insignificant for (137)Cs or (65)Zn because external dose rates to the soil dwelling earthworms due to these radionuclides were much greater than the internal dose rate. In contrast, the total dose from (90)Sr was determined by the internal dose rate and therefore proportional to the CR(eq).

Standardization of 65Zn by sum-peak method.

A commercial solution of (65)Zn was standardized by the sum peak-method using a planar HPGe detector. The activity results were compared with measurements made with a well type 4πγ ionization chamber, which is traceable to BIPM.RI (II)-K2.Zn-65 key-comparison performed in 2002. The sum-peak value was 42.79 kBq/g and the ionization chamber value was 42.74 kBq/g both at the reference date. The uncertainty obtained in the sum peak standardization was 0.25% (k=1), and in the ionization chamber was 0.85% (k=1). The results showed that sum-peak method can be used in (65)Zn standardization and this method is easier, simpler and more practical than others methods.

A comparison between Monte Carlo-calculated and -measured total efficiencies and energy resolution for large plastic scintillators used in whole-body counting.

The measured total efficiency for several source positions has been determined for a large, plastic scintillation detector (NE 102A, 91.5 × 76.0 × 24.5 cm(3)) used for whole-body counting gamma spectrometry. The results have been compared with Monte Carlo-calculated total efficiencies; the code used was MCNPX 2.60. For (137)Cs, there was a good agreement between the measured and calculated total efficiencies. MXNPX was also used to calculate the electron light yield for (137)Cs; for the detector material NE 102A, Birks' constant kB was found to be 9.6 mg cm(-2) MeV(-1). The effect of light losses on spectrum resolution has been investigated for (65)Zn.

Differential uptake and oxidative stress response in zebrafish fed a single dose of the principal copper and zinc enriched sub-cellular fractions of Gammarus pulex.

The sub-cellular compartmentalisation of trace metals and its effect on trophic transfer and toxicity in the aquatic food chain has been a subject of growing interest. In the present study, the crustacean Gammarus pulex was exposed to either 11 microg Cu l(-1), added solely as the enriched stable isotope 65Cu, or 660 microg Zn l(-1), radiolabeled with 2MBq (65)Zn, for 16 days. Post-exposure the heat stable cytosol containing metallothionein-like proteins (MTLP) and a combined granular and exoskeletal (MRG+exo) fractions were isolated by differential centrifugation, incorporated into gelatin and fed to zebrafish as a single meal. Assimilation efficiency (AE) and intestinal lipid peroxidation, as malondialdehyde (MDA) were measured. There was a significant difference (p<0.05) between the retention of the MTLP-Zn (39.0+/-6.4%) and MRG+exo-Zn (17.2+/-3.7%) and of this zinc retained by the zebrafish a significantly greater proportion of the MTLP-Zn feed had been transported away from the site of uptake. For 65Cu, although the results pointed towards greater bioavailability of the MTLP fraction compared to MRG+exo during the slow elimination phase (24-72 h) these results were not significant (p=0.155). Neither zinc feed provoked a lipid peroxidation response in the intestinal tissue of zebrafish compared to control fish (gelatin fed), but both 65Cu labeled feeds did. The greater effect was exerted by the MRG+exo (2.96+/-0.29 nmol MDA mg protein(-1)) feed which three-fold greater than control (p<0.01) and almost twice the MDA concentration of the MTLP feed (1.76+/-0.21 nmol MDA mg protein(-1), p<0.05). The oxidative stress response produced by Zn and Cu is in keeping with their respective redox potentials; Zn being oxidatively inert and Cu being redox active. These results are similar, in terms of bioavailability and stress response of each feed, to those in our previous study in which 109Cd labeled G. pulex fractions were fed to zebrafish. Thus it appears that when a metal (Cu or Cd) has the potential to cause cytotoxicity via lipid peroxidation, a feed consisting of a largely unavailable fraction (MRG+exo) causes a greater intestinal stress response than the more bioavailable (MTLP) feed.

[Soil sorption and transfer from it to plant of the radioactive and stable isotopes of chemical elements: methodology and experimental approach].

The adsorption of pair nuclides 60Co/Co and 65Zn/Zn by solid phase and their availability to plants were studied in soil suspension conditions and in the sod podzolic soil under controlled moisture. The situation when the radionuclide in constant activity is entered to system (surface water, soil) with different heavy metal contamination has been modeled. Was observed that soil contamination with heavy metal Co (Zn) significantly reduce sorption of the radionuclide 60Co (65Zn) by solid phase. As a result, the activity concentration of the 60Co or 65Zn in soil solution and, therefore, their mobility and potential availability to plants increases in 2-4 times with the total metal concentration increasing. The difference between two elements is that high Co concentration increase root uptake of the 60Co, whereas soil contamination with Zn reduce activity of 65Zn in the 14-days barley plants that may reflects diverse plant necessity of two elements and more important role of the isotopic exchange effect in the case of Zn.

New best estimates for radionuclide solid-liquid distribution coefficients in soils. Part 3: miscellany of radionuclides (Cd, Co, Ni, Zn, I, Se, Sb, Pu, Am, and others).

New best estimates for the solid-liquid distribution coefficient (K(d)) for a set of radionuclides are proposed, based on a selective data search and subsequent calculation of geometric means. The K(d) best estimates are calculated for soils grouped according to the texture and organic matter content. For a limited number of radionuclides this is extended to consider soil cofactors affecting soil-radionuclide interaction, such as pH, organic matter content, and radionuclide chemical speciation. Correlations between main soil properties and radionuclide K(d) are examined to complete the information derived from the best estimates with a rough prediction of K(d) based on soil parameters. Although there are still gaps for many radionuclides, new data from recent studies improve the calculation of K(d) best estimates for a number of radionuclides, such as selenium, antimony, and iodine.

Zinc as a marker in viscera of suspected metal phosphide poisoning: a study by neutron activation analysis.

Zinc as a marker element in the viscera of suspected metal phosphide poisoning has been studied during the present work. Neutron activation analysis (NAA) has been employed to detect and quantify the concentration of zinc in the viscera/stomach portion. The methodology has been developed on simulated and real life viscera samples to quantify the amount of zinc using NAA. The results obtained by NAA for real-life samples have been validated using a complementary analytical technique (viz. differential pulse anodic stripping voltammetry), and the values obtained were in good agreement, within +/- 5-8%. This exercise could be useful in medico-legal field for framing a definitive opinion about zinc phosphide poisoning.

Effect of dietary ligands and food matrices on zinc uptake in Caco-2 cells: implications in assessing zinc bioavailability.

The kinetics, depletion/repletion of zinc, and effects of dietary ligands/food matrices on (65)Zn uptake was studied in Caco-2 cells. The uptake of zinc showed a saturable and nonsaturable component, depending upon the media zinc concentrations. Intracellular depletion increased zinc uptake, whereas zinc loading did not. Phytic acid and histidine inhibited zinc uptake, while tannic acid, tartaric acid, arginine, and methionine increased zinc uptake. Tannic acid at a 1:50 molar ratio promoted zinc uptake from wheat- and rice-based food matrices. Further, Caco-2 cells responded similarly with zinc and iron uptake when fed Indian bread prepared from low- and high-extraction wheat flour, representing low and high phytate content. However, inclusion of tea extract or red grape juice as a source of polyphenols enhanced the uptake of zinc while decreasing that of iron. These results suggest that the Caco-2 cells predict the correct direction of response to dietary ligands even from complex foods.

Zinc and iron bioavailability of genetically modified soybeans in rats.

The aim of this work was to evaluate zinc and iron bioavailability of UFV-116, a new variety without 2 lipoxygenases, with better taste and flavor than a commercial variety OCEPAR 19, containing all 3 isozymes. To evaluate zinc absorption using 65Zn whole body retention and femur 65Zn uptake, rats were given 3 g of a 65ZnCl2 labeled test meal (0.25 microCi). The 2 varieties were tested at the level of 9 and 30 ppm of zinc as defatted soy flour. Two other groups (control) received egg white as source of protein and ZnS04.H20 as the zinc source. To evaluate iron absorption, using 59Fe whole body retention, animals were given a 3 g 59FeCl3 labeled test meal (0.2 microCi). The 2 varieties were tested at 12 and 25 ppm iron as defatted soy flour. Whole fat soy flour of variety 1 (UFV-116) was higher (P < 0.05) in Ca, K, Mg, phytic acid, and oxalate than variety 2 (OCEPAR-19). No difference was observed among the soybean varieties (P > 0.05) for femur 65Zn retention, at different levels of zinc. However, whole body retention was lower (P < 0.05) for UFV-116 than for OCEPAR-19. Femur 65Zn uptake was correlated with the whole body retention; however, whole body retention was more sensitive. Whole body 59Fe retention from UFV-116 was lower (P < 0.05) than from OCEPAR-19. Zinc and iron bioavailability was lower for UFV-116, possibly due to its higher content of antinutrient factors, especially phytate.

Activity measurements and determination of gamma-ray emission intensities in the decay of 65Zn.

An International EUROMET exercise, Action 721, was organized with the objective of obtaining more reliable decay data on the disintegration of 65Zn. Nine laboratories participated, sending their results relating to activity measurements and 1115-keV gamma-ray emission intensity. Participants mainly used the 4pibeta-gamma coincidence method for the activity measurement, the resulting values and uncertainty budgets are described. New gamma-ray emission intensities were also measured in this exercise and, taking into account previously published values, the intensity of the 1115-keV gamma-ray emission has been determined to be 50.22(11)%.

An approach based on the SIR measurement model for determining the ionization chamber efficiency curves, and a study of 65Zn and 201Tl photon emission intensities.

The measurement model used to determine ionization chamber efficiency curves accounts from the outset for impurity corrections and beta spectrum shapes. The curves are represented by exponentials of polynomials whose coefficients are adjusted using non-linear least-squares minimization. The curves are validated by comparing with SIR key comparison reference values (KCRVs) and other published curves. The associated covariance matrix is also evaluated. Deviations from model predictions for 65Zn and 201Tl using recommended nuclear data are studied.

Absolute activity measurement of the electron-capture-based radionuclides 139Ce, 125I, 192Ir and 65Zn by liquid scintillation coincidence counting.

Four radionuclides with electron-capture-based decay schemes have been directly measured by a liquid scintillation coincidence extrapolation technique. 125I, 192Ir and 65Zn were measured as part of international key comparisons held under the auspices of the International Bureau of Weights and Measures (BIPM). The 139Ce measurements formed part of a regional comparison organized by the Asia Pacific Metrology Programme (APMP). Since 139Ce decays purely by electron-capture, the basic method is described for this radionuclide. Results and difficulties encountered are discussed and uncertainty budgets are presented.

Standardisation of 54Mn and 65Zn using a software coincidence counting system.

The activities of 54Mn and 65Zn have been determined by 4pi(PC)-gamma coincidence counting, with efficiency variation performed by the conventional method of altering the self-absorption in the sources as well as by the computer discrimination method. The standardisation of 65Zn presents some complications requiring optimisation of the gamma-ray energy window settings to achieve a linear efficiency-extrapolation curve. Determination of these optimal settings by the conventional coincidence method is a tedious task. These difficulties have been reduced by the utilisation of a software coincidence counting system that records time and amplitude information of individual pulses from coincidence measurements, where the coincidence parameters are set after the data collection process has completed, facilitating multiple data evaluations on a single data set. The optimal gamma-ray energy window settings for the 65Zn standardisation were derived from the results of the 54Mn standardisation, as well as from studies of the 65Zn data itself. The setting of the PC channel thresholds for K and both (K+L) electrons is also discussed. The results are compared with those attained using conventional coincidence counting.

Standardization and nuclear decay data of 65Zn.

Standardization by means of 4pibeta-gamma coincidence counting was applied to calibrate a 65Zn solution within the scope of EUROMET project no. 721. The activity result was combined with gamma-ray spectrometry measurements to investigate the photon emission probabilities. The half-life of 65Zn was measured with improved accuracy by means of 4pi ionization chamber measuring systems that were also used for secondary activity determination. In addition, we tested a new secondary standardization procedure by means of liquid scintillation counting.

The LSC efficiency for low-Z electron-capture nuclides.

In this paper, we apply the CIEMAT/NIST method to the three low-Z electron-capture nuclides 54Mn, 55Fe and 65Zn by using the KLM and KL1L2L3M atomic rearrangement models, respectively. The counting efficiencies are computed with the new code EMILIA, which comprises an improved model for the interaction of low-energy X-rays with the scintillation cocktail. The calculated counting efficiencies are compared with experimental results.

Precise Zn isotopic ratio measurements of human red blood cell and hair samples by multiple collector-ICP-mass spectrometry.

Precise 66Zn/64Zn and 68Zn/64Zn isotopic ratios of biochemical samples have been measured using multiple collector-ICP-mass spectrometry (MC-ICPMS). In order to eliminate the mass spectrometric interferences on Zn isotopes (e.g., 64Ni+ and 136Ba2+), we chemically purified the analyte using an ion chromatographic technique. The resulting precisions of the 66Zn/64Zn and 68Zn/64Zn ratio measurements were 0.05/1000 and 0.10/1000 (2SD), respectively, which were enough to detect the isotopic variation of Zn in nature. Red blood cell (RBC) samples were collected from five volunteers (four males and one female), including a series of 12 RBC samples from one person through monthly-based sampling over a year. These were analyzed to test possible seasonal changes and variations in 66Zn/64Zn and 68Zn/64Zn ratios among the individuals. The 66Zn/64Zn and 68Zn/64Zn ratios for a series of 12 RBC samples collected over a year were 0.43/1000 and 0.83/1000 higher than the values of highly purified Zn metal (JMC Zn), and no seasonal change could be found. The 66Zn/64Zn and 68Zn/64Zn ratios for RBC samples collected from five volunteers did not vary significantly. In order to investigate Zn isotopic heterogeneity in a human body, Zn isotopic ratios of a hair sample collected from one of the volunteers was also analyzed. The 66Zn/64Zn and 68Zn/64Zn ratios for the hair sample were 0.59/1000 and 1.14/1000 lower than the mean value of RBC samples. This result demonstrates that detectable isotopic fractionation occurs in the human body. The data obtained here suggest that the isotopic ratios of trace metals could provide new information about transportation of metal elements in vivo.

Experimental verification of the half-life of 65Zn.

The half-life of 65Zn was determined experimentally and compared with literature values. Two ampoules of a 65Zn solution were measured at regular intervals in two ionisation chambers over a period corresponding to nearly two half-lives. The result of 243.8+/-0.3 days is in agreement with the value of 244.0+/-0.2 days obtained by De Roost et al. (Z. Phys. 250 (1975) 395) at the same institute (previously called CBNM) in 1972. Moreover, this half-life is supported by most of the other measurements reported in the literature.

Standardization of 65Zn.

Two absolute methods were used for standardizing the 65Zn solution received within the framework of the 2002-2003 full-scale BIPM comparison. The first method was the 4piPC-gamma-coincidence with efficiency extrapolation. The measurement conditions were adjusted so that the slope of the extrapolation curve was absent, which ensured that the measurement result did not depend on the positron branch intensity. When using the second method, the KX-gamma-coincidence counting with two NaI(Tl) scintillation crystals of different thicknesses, extrapolation was not needed, but a correction for the positron branch was necessary. It is shown that the 4piPC-gamma-coincidence method has a significantly larger uncertainty, and it is necessary to pay attention to the uncertainty component connected with setting the gamma-channel mode, which is characteristic for 65Zn only.

Standardization of 65Zn by 4piPC-gamma coincidence counting method with efficiency extrapolation.

A 65Zn solution was standardized by the 4piPC-gamma efficiency-extrapolation coincidence counting method. Theoretical aspects of coincidence equations, efficiency equations and linearity conditions are reviewed. Experimental measurements were performed for two low level discrimination thresholds for the PC channel (counting K+L or K X-rays or Auger electrons from EC decay) and for three different settings of the gamma window. Requirements on gamma channel set-up for linear extrapolation were established by using a Pb absorber or by proper gamma window setting. The measured activity values were discussed and found in good agreement with those obtained with a calibrated ionization chamber.