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The performance of 41Ca measurements at the 6 MV AMS system at HZDR, DREAMS (DREsden AMS) was improved in terms of overall efficiency and suppression of interfering isobar 41K. Mixing CaF 2 samples not only with Ag, but also with PbF 2 increases the negative ionization efficiency by a factor 3, from 0.15% to 0.45%. This option is dedicated to low level samples because ion source parameters have to be lowered, which increases the measurement time. In general, 41K–suppression factor of the detector is improved from 2 × 104 to 4 × 104 by advances in the analysis of the spectra. With such improvements, a 95% confidence level (C.L.) sensitivity for the 41Ca/40Ca ratio of 2 × 10–15 can be achieved at DREAMS. [ABSTRACT FROM AUTHOR]

41Ca (t 1/2 = 9.94 × 104 yrs) is an important stellar radionuclide and its production in the Early Solar System from various irradiation scenarios can help determine the viability of models of early stellar processes. A novel reaction technique has been under development and recently tested at the Nuclear Science Laboratory at the University of Notre Dame. This technique utilizes an "in-cathode" reaction method, where natural CaF 2 material is packed into an ion source sample holder (cathode) and then irradiated and subsequently measured using Accelerator Mass Spectrometry (AMS) without the need for chemical processing afterward. The setup for the irradiation was performed using a 3He beam to measure the reaction natCa(3He,x)41Ca. Initial AMS results suggest additional complexity due to ion source sputtering rates and geometry, which will need to be explored further. [ABSTRACT FROM AUTHOR]

The total and individual multipole moments of magnetic electron scattering form factors in 41 Ca have been investigated using a widely successful model which is the nuclear shell model configurations keeping in mind of 1f7⁄2 subshell as an L-S shell and Millinar, Baymann, Zamick as L-S shell (F7MBZ) to give the model space wave vector. Also, harmonic oscillator wave functions have been used as wave function of a single particle in 1f7⁄2 shell. Nucleus 40Ca as core closed and Core polarization effects have been used as a corrective with first order correction concept to basic computation of L-S shell and the excitement energy has been implemented with 2ћω. The core polarizability effect has been utilized to incorporate the rejected space (core + higher arrangement) via L-S shell with a realism interaction of effective M3Y P2 interaction to connect the model space particles in motion with the spouse (p-h). The two body M3Y interactions have been utilized as an interaction residue to calculate the core polarizability matrix elements. Finally, the theoretical result of the form factor has been compared with the experimental results. [ABSTRACT FROM AUTHOR]

The analysis of 41Ca in concrete generated from the nuclear facilities decommissioning is critical for ensuring the safe management of radioactive waste. An analytical method for the determination of 41Ca in concrete is described. 41Ca is a neutron-activated long radionuclide, and hence, for accurate analysis, it is necessary to completely extract Ca from the concrete sample where it exists as the predominant element. The decomposition methods employed were the acid leaching, microwave digestion, and alkali fusion. A comparison of the results indicated that the alkali fusion is the most suitable way for the separation of Ca from the concrete sample. Several processes of hydroxide and carbonate precipitation were employed to separate 41Ca from interferences. The method relies on the differences in the solubility of the generated products. The behavior of Ca and the interfering elements such as Fe, Ni, Co, Eu, Ba, and Sr is examined at each separation step. The purified 41Ca was measured by a liquid scintillation counter, and the quench curve and counting efficiency were determined by using a certified reference material of known 41Ca activity. The recoveries in this study ranged from 56 to 68%, and the minimum detectable activity was 50 mBq g−1 with 0.5 g of concrete sample.

Abstract The analysis of 41Ca can be quantified by measuring the ratio 41Ca/40Ca. At present, ratios of 41Ca/40Ca ≤ 10−11 can only be measured by accelerator mass spectrometry (AMS). The sensitivity is mainly limited by the interference of the isobar 41K. With compact AMS (≤1 MV), abundance sensitivities of 10−11 to 10−12 have been demonstrated, but this may necessitate the measurement of 39K to correct for the 41K background. With a 3 MV AMS, the dE/dx method can still be used to partially separate 41Ca from 41K. In this work, a new capability for 41Ca analysis has been tested at the Xi'an-AMS. Ca4+ was chosen to achieve a balanced performance between 41Ca/41K separation and transmission efficiency. A 41Ca/40Ca background level of near 10−13 was achieved without the need for 39K correction. This new analytical capability at our facility was then applied to 41Ca tracer samples from our studies on the "White Jade" land snail shells, in which 41Ca was used as a tracer for studying the absorption rate of calcium. [ABSTRACT FROM AUTHOR]

Abstract Dealing with the 41K interference during 41Ca measurement with low energy AMS systems is challenging. The detection of 39K to correct the measured 41Ca/40Ca ratios is a powerful tool that improves precision and accuracy. However, the study of the sources of this interference can help to reduce it to its minimum. In this work, it is shown that iron is a factor enhancing the production of the 41K interference, since the (41K57Fe)− ion has the same mass as (41K19F 3)−. To validate this observation, we measured 57Fe2+ together with 41M2+ (all ions with mass 41) and 39K2+ in a blank sample and an aluminum target at the 600 kV AMS system at ETH Zurich. We also show the temporal evolution of 41M/40Ca and 39K/40Ca ratios in two blank samples during a measurement on the 1 MV AMS system at CNA Seville. Even when unstable behavior for these ratios is observed for one of the blanks, the relationship between both, 41M/39K, is relatively stable over time. This supports the accuracy of the K–correction method, providing that it is applied sequence by sequence. Two programs, one for each of these compact AMS systems, were written in FORTRAN code to deal with the complexity of the data analysis due to the K-correction. [ABSTRACT FROM AUTHOR]

The calcium deficiency has caused many problems such as browning， poor storability for Feicheng peach，which is great economic losses for Chinese farmers. It is very significant to research the transport rule of calcium in fruit trees. In order the absorption, translocation and distribution of calcium in peach, a technique of 41Ca isotope tracer combined with AMS was developed and applied in the study. A field experiment was conducted to determine effects of injecting calcium fertilizer on tracer calcium content dynamic, calcium distribution of Feicheng peach to understand the rules of absorbing calcium and provides the theoretical basis in adding calcium nutrient and technical guidance. The experimental material is 11 years old Feicheng peach tree. Ca(N03)2 solution (including 41Ca) was injected on selected Feicheng peach fruit flees at 2015.04.30 at the florescence. Then, about every 30 days, the peach trees different organs, such as new shoots, leaves, perennial branches, were collected. All the samples were prepared to CaF) and measured at HI-13 AMS at CIAE. The main results are follows： (1) More than 60% of 41Ca were stored in the trunk and the 41Ca distribution gradually decreased from bottom to top in trunk. (2) In young fruit stage, the calcium was mainly absorbed by organs such as leaves, branches, flesh mainly concentrated, however, from the fruit swelling period to the mature stage, calcium content in the leaves and flesh was declining, and the calcium content in the perennial branches had the same tendency at the beginning but it grew in the mature stage. (3) In mature stage, from August 4 to September 2 the distribution of 41Ca of each organ showed that the organs. calcium content was higher whose transpiration was greater and the calcium contents of new organs were as follows： new shoot>pericarp>flesh. It is feasible and easy to explore the peach tree for calcium absorption and distribution by using 41Ca-AMS technology. And the rapidly calcium growing period of new shoots and leaves is at the florescence for trunk injection application of calcium. The best calcium absorption time was studied in order to provide a guidance. While there are some shortages in this experiment, such as the datum of root, new leaves for the limitation of targets in source were not got. In the future, a new and special facility to measure the built, so that more detailed study about the running rule of calcium ion in peach trees can be improved. [ABSTRACT FROM AUTHOR]

Background: Dietary soluble corn fiber (SCF) significantly improves calcium absorption in adolescents and the bone strength and architecture in rodent models. Objective: In this study, we aimed to determine the skeletal benefits of SCF in postmenopausal women. Design: We used our novel technology of determining bone calcium retention by following the urinary appearance of 41Ca, a rare long-lived radioisotope, from prelabeled bone to rapidly and sensitively evaluate the effectiveness of SCF in reducing bone loss. A randomized-order, crossover, double-blinded trial was performed in 14 healthy postmenopausal women to compare doses of 0, 10, and 20 g fiber from SCF/d for 50 d. Results: A dose-response effect was shown with 10 and 20 g fiber from SCF/d, whereby bone calcium retention was improved by 4.8% (P < 0.05) and 7% (P < 0.04), respectively. The bone turnover biomarkers N-terminal telopeptide and osteocalcin were not changed by the interventions; however, a significant increase in bone-specific alkaline phosphatase, which is a bone-formation marker, was detected between 0 and 20 g fiber from SCF/d (8%; P = 0.035). Conclusion: Daily SCF consumption significantly increased bone calcium retention in postmenopausal women, which improved the bone calcium balance by an estimated 50 mg/d. This study was registered at clinicaltrials.gov as NCT02416947. [ABSTRACT FROM AUTHOR]

Background: Ensuring adequate vitamin D status in older adults may reduce the risk of osteoporosis. The serum 25-hydroxyvitamin D [25(OH)D] concentration is the recommended biomarker of vitamin D status, but the optimal serum 25(OH)D concentration for bone health in postmenopausal women remains unclear. Objective: The aim of this study was to apply the highly sensitive (41)Ca skeletal labeling technique and the measurement of urinary (41)Ca:(40)Ca ratios to determine the serum 25(OH)D concentration that has greatest benefit on bone calcium flux in postmenopausal women. Methods: We administered a mean intravenous (41)Ca dose of 870 pmol to healthy postmenopausal women [n = 24, age (mean ± SD): 64 ± 6.0 y] without osteoporosis. After 6 mo, at the nadir of their wintertime serum 25(OH)D status, each of the women sequentially consumed daily oral cholecalciferol supplements of 10, 25, and 50 μg/d (in this order), each for 3 mo. We assessed serum 25(OH)D concentrations monthly and urinary (41)Ca:(40)Ca ratios biweekly. (41)Ca:(40)Ca ratios were measured with low-energy accelerator mass spectrometry. With the use of pharmacokinetic analysis, we determined the effect of varying serum 25(OH)D concentrations on (41)Ca transfer rates. Results: At baseline, the mean (95% CI) serum 25(OH)D concentration was 16.2 (13.5, 18.8) μg/L. After the first, second, and third intervention periods, mean (95% CI) serum 25(OH)D increased to 29.8 (27.2, 32.4), 36.9 (34.2, 39.7), and 46.6 (41.2, 52.0) μg/L, respectively. Supplementation was associated with a downward shift in the urinary (41)Ca:(40)Ca ratio compared with the predicted (41)Ca:(40)Ca ratio without vitamin D supplementation. In the model, the most likely site of action of the increase in serum 25(OH)D was transfer from the central compartment to a fast exchanging compartment. At this transfer rate, predicted values were a concentration with half-maximal effect of 2.33 μg/L and an estimate of the maximal effect of 31.7%. After the first, second, and third intervention periods, the mean changes in this transfer rate were +18.0%, +25.7%, and +28.5%, respectively. Conclusion: In healthy postmenopausal women, increasing serum 25(OH)D primarily affects calcium transfer from the central compartment to a fast exchanging compartment; it is possible that this represents transfer from the extracellular space to the surface of bone. A serum 25(OH)D concentration of ~40 μg/L achieves ~90% of the expected maximal effect on this transfer rate. This trial was registered at clinicaltrials.gov as NCT01053481. [ABSTRACT FROM AUTHOR]

Background: Postmenopausal estrogen depletion is a major contributing factor to bone loss. Soy isoflavones have variable effects on the prevention of postmenopausal bone loss, which is possibly related to the specific isoflavone content or the variable equol-producing capacity of individuals. Objective: We aimed to determine the effects of the content of isoflavones in a soy supplement and the equol-producing ability of the individual on postmenopausal bone calcium retention. Design: The study was a blinded, randomized, crossover intervention trial in 24 postmenopausal women who were prescreened for their ability to convert daidzein to equol. Women were equilibrated with 41Ca before the intervention. Interventions were 5 soy isoflavone oral supplements (2 doses of a genistein-rich soy supplement and 3 doses of mixed isoflavones in various proportions) and a bisphosphonate (risedronate). Each intervention was given sequentially for 50 d followed by a 50-d washout period. The percentage of bone calcium retention was determined from the change in urinary 41Ca:calcium. Results: Interventions that ranged from 52 to 220 mg total isoflavones/d increased bone calcium retention between 3.4% and 7.6% (P < 0.05), which was a moderate effect compared with that of risedronate at 15.3% (95% CI: 7.1%, 22.7%; P = 0.0014). The most-effective soy intervention delivered 105.23 mg total isoflavones/d as genistein, daidzein, and glycitein in their natural ratios and increased bone calcium retention by 7.6% (95% CI: 4.9%, 10.2%; P < 0.0001). Genistein, at 52.85 mg/d, increased bone calcium retention by 3.4% (95% CI: 0.5%, 6.2%; P = 0.029); but there was no benefit at higher amounts (113.52 mg/d). There was no difference (P = 0.5) in bone calcium retention between equol producers and nonproducers. Conclusion: Soy isoflavones, although not as potent as risedronate, are effective bone-preserving agents in postmenopausal women regardless of their equol-producing status, and mixed isoflavones in their natural ratios are more effective than enriched genistein. This trial was registered at clinicaltrials.gov as NCT00244907. [ABSTRACT FROM AUTHOR]

Abstract: Activation measurements of materials exposed to nuclear bomb explosions are widely used to reconstruct the neutron flux for retrospective dosimetry. In this study the applicability of coral CaCO3 as a biogenic neutron fluence dosimeter is tested. The long-lived radioisotopes 41Ca, 14C and 10Be, which had been produced in nuclear bomb explosions, are measured in several coral sand samples from the Bikini atoll at the 600 kV and 200 kV AMS facilities of ETH Zurich. Elevated concentrations of all studied isotopes are found in a sample from the crater that was initially formed by the high-yield nuclear explosion Castle Bravo in 1954 and that had been used as site for several tests afterward. The observed 14C concentration is considered too large to originate from neutron irradiation of CaCO3 alone. The relatively low concentration of 10Be found in the crater sample indicates that production of 10Be during nuclear bomb testing is generally minor. A simple neutron fluence reconstruction is performed on basis of the 41Ca/40Ca ratio. [Copyright &y& Elsevier]

Abstract: The radiological characterisation of nuclear waste is essential for managing storage sites. Determining the concentration of Long‐Lived RadioNuclides (LLRN) is fundamental for their long-term management. This paper focuses on the measurement of low 41Ca concentrations in ions exchange resins used for primary fluid purification in Pressurised Water Reactors (PWR). 41Ca concentrations were successfully measured by Accelerator Mass Spectrometry (AMS) after the acid digestion of resin samples, followed by radioactive decontamination and isobaric suppression through successive hydroxide, carbonate, nitrate and final CaF2 precipitations. Measured 41Ca concentrations ranged from 0.02 to 0.03ng/g, i.e. from 0.06 to 0.09Bq/g. The 41Ca/60Co activity ratios obtained were remarkably reproducible and in good agreement with the current ratio used for resins management. [Copyright &y& Elsevier]

Abstract: A 41Ca interlaboratory comparison between Lawrence Livermore National Laboratory (LLNL) and the Purdue Rare Isotope Laboratory (PRIME Lab) has been completed. Analysis of the ratios assayed by accelerator mass spectrometry (AMS) shows that there is no statistically significant difference in the ratios. Further, Bayesian analysis shows that the uncertainties reported by both facilities are correct with the possibility of a slight under-estimation by one laboratory. Finally, the chemistry procedures used by the two facilities to produce CaF2 for the cesium sputter ion source are robust and do not yield any significant differences in the final result. [Copyright &y& Elsevier]

Abstract: Three refractory coarse grained CAIs from the Efremovka CV3 chondrite, one (E65) previously shown to have formed with live 41Ca, were studied by ion microprobe for their 26Al–26Mg and 10Be–10B systematic in order to better understand the origin of 10Be. The high precision Al–Mg data and the inferred 26Al/27Al values attest that the precursors of the three CAIs evolved in the solar nebula over a period of few hundred thousand years before last melting–crystallization events. The initial 10Be/9Be ratios and δ10B values defined by the 10Be isochrons for the three Efremovka CAIs are similar within errors. The CAI 10Be abundance in published data underscores the large range for initial 10Be/9Be ratios. This is contrary to the relatively small range of 26Al/27Al variations in CAIs around the canonical ratio. Two models that could explain the origin of this large 10Be/9Be range are assessed from the collateral variations predicted for the initial δ10B values: (i) closed system decay of 10Be from a “canonical” 10Be/9Be ratio and (ii) formation of CAIs from a mixture of solid precursors and nebula gas irradiated during up to a few hundred thousand years. The second scenario is shown to be the most consistent with the data. This shows that the major fraction of 10Be in CAIs was produced by irradiation of refractory grains, while contributions of galactic cosmic rays trapping and early solar wind irradiation are less dominant. The case for 10Be production by solar cosmic rays irradiation of solid refractory precursors poses a conundrum for 41Ca because the latter is easily produced by irradiation and should be more abundant than what is observed in CAIs. 10Be production by irradiation from solar energetic particles requires high 41Ca abundance in early solar system, however, this is not observed in CAIs. [Copyright &y& Elsevier]

Abstract: The mechanisms governing calcium fluxes during bone remodeling processes in Osteoporosis (OP) patients are poorly known. Understanding the changes of Osteoclasts (OC) during this dynamic transition is important to prevent and cure OP. The exploration of long-lived 41Ca (T 1/2 =1.04×105 years) tracer combined with AMS measurements leads to the possibility of monitoring the bone resorption behavior of OC in OP patients. In this work, the behavior of OC with the administration of Strontium Ranelate (SR), a drug for OP, was studied by using 41Ca labeled hydroxyapatite (HAP) to simulate the bone. AMS on the HI-13 tandem accelerator at CIAE was used to determine trace amounts of 41Ca. The results show that the technique of 41Ca tracing with AMS can be used to quantitatively monitor the behavior of OC in bone resorption under the effects of drugs. Experimental details and preliminary results will be presented. [Copyright &y& Elsevier]

Calcium-41 ( t = 10 years) can be used after a single dose to follow calcium metabolism over a subject's lifetime. The aims of this study were to expand a Ca kinetic model and estimate bone resorption in women with stable bone loss, compare the rates with those calculated with classical isotope studies, and to use the model to simulate dynamic changes in urinary Ca:Ca ratios and bone balance for the design and interpretation of Ca studies. Forty-two women >5 years post-menopause were given Ca intravenously. Bone mineral content and bone mineral density of total body were measured by dual-energy X-ray absorptiometry at the beginning of the study. Urine collections were made periodically for up to ∼5 years while subjects were free living. Urinary Ca:Ca ratios were measured using accelerator mass spectrometry. The isotope data were analyzed by compartmental modeling. Four compartments were necessary to fit the urinary tracer data and total bone calcium. The final model included pathways for absorption, distribution, urinary excretion, and endogenous excretion and was used to calculate rates of bone turnover. Estimates of bone resorption in a subset of the women ( n = 13), studied previously in a 3-week balance and full kinetic study with Ca, agreed with those using Ca methodology. Thus, rates of bone resorption can be estimated from Ca urinary data in stable post-menopausal women. The model was used to simulate dynamic changes in urinary Ca:Ca ratios and bone balance, as a result of interventions that perturb calcium metabolism to aid in study design and interpretation. [ABSTRACT FROM AUTHOR]

Summary: Urinary excretion of tritiated tetracycline (H-TC) and Ca tracers was validated as reflecting skeletal disappearance of these bone-seeking tracers as a direct measure of bone turnover following ovariectomy in rats. Introduction: Tritiated tetracycline (H-TC) and Ca tracers have been used to measure bone resorption in animal models, but urinary excretion of these labels has not been directly compared to skeletal turnover. We aimed to evaluate the use of bone-seeking labels by comparing label release into urine with label in the skeleton when bone turnover was perturbed following ovariectomy. Methods: Sixty-four 6-month-old ovariectomized (OVX) rats were randomized to one of eight groups in a 2 × 4 design that differed in time of H-TC and Ca administration following ovariectomy (1 month, when bone turnover would be accelerated following estrogen depletion or 3 months when bone loss due to OVX had slowed down) and time of euthanasia (1 week, 1 month, 3 months, and 6 months post-dose). Twenty-four-hour urine pools over two to four consecutive days and total skeleton were collected and recovered for the assessment of H-TC and Ca. Results: Urinary H-TC levels reflected skeletal H-TC levels ( r = 0.93; p < 0.0001) over a wide range of bone turnover rates in response to an intervention. Urinary Ca and H-TC excretion were highly correlated ( r = 0.95, p < 0.0001). Conclusion: This study confirms that bone-seeking label excretion into the urine directly measures bone turnover. [ABSTRACT FROM AUTHOR]

Abstract: Recent improvements in isobaric suppression for medium-mass isotopes, e.g. 41Ca, offer new possibilities for tandem accelerators with terminal voltages of 3MV or lower; i.e. when dealing with particle energies ⩽1MeV/amu. In particular, detection of 41Ca requires sufficient discrimination of the stable isobar 41K. We explored the limits of 41Ca detection at our 3-MV AMS facility by means of different types of particle detectors: The ΔTOF method, which is based on the different flight-time of isobars after passing a thick absorber foil. The second method makes use of a new type of compact ionization chamber: 41K and 41Ca are separated in energy due to their different energy loss in the detector entrance foil and the detector gas, which is measured via a segmented anode. At VERA we measured 41Ca/Ca ratios below 10−13 for commercial CaF2 material serving as blank samples. CaH2 sputter targets, with the extraction of , yielded background ratios as low as 41Ca/Ca=1×10−15. The typical measurement precision at VERA for 41Ca measurements was between 2% and 5%. These results demonstrate that AMS facilities based on 3-MV tandems have reached the sensitivity level of larger AMS facilities for a wide range of applications, with the advantage of high overall efficiency and sample throughput. [Copyright &y& Elsevier]

Abstract: A comparative study was made between the compact AMS system at the PSI/ETH Laboratory of Ion Beam Physics in Zurich with 0.5MV terminal voltage and the 5MV-AMS system at the Scottish Universities Environmental Research Centre (SUERC), Glasgow. Overall 34 urinary samples with 41Ca/40Ca ratios in the range from 4×10−11 to 3×10−10 were processed to CaF2 and aliquots of the same material were measured on both instruments. Measurements on the compact AMS system were performed in charge state 3+ achieving a transmission of 4% at 1.7MeV beam energy. Under these conditions a suppression of the interference 41K is virtually impossible. However, samples with an excess of potassium can be identified by a shift of the 41Ca/41K peak in the ΔE −E histogram of the gas ionization detector employed and a criterion for data rejection can be defined. An overall precision of ∼4% and a 41Ca/40Ca background level of 5×10−12 have been reached. For studies with higher demands on the detection limit AMS systems like the one at SUERC are attractive: in charge state 5+ and using a gas stripper beam energy of 27MeV, a transmission of 5%, a 41K suppression factor of ∼500 and a 41Ca/40Ca background level of 3×10−14 are achieved. We demonstrate that both systems are well suited for large-scale 41Ca biomedical applications. [Copyright &y& Elsevier]

Urinary excretion of bone labels can be used to monitor bone resorption. Here we investigate the effects of dosing frequency on label incorporation of various sites when bone turnover was perturbed by ovariectomy. We compared tritiated tetracycline (3H-TC) and 45Ca in two studies. Nine-month-old rats were given single or multiple injections of 3H-TC and 45Ca and sacrificed after 7 or 14 days. Six-month-old OVX rats were given 3H-TC and 41Ca tracers 1 or 3 months following ovariectomy (OVX + 1 mo or OVX + 3 mo, when bone turnover was higher or lower, respectively) and sacrificed 1 week, 1 month, 3 months, or 6 months postdose. Twenty-four-hour urine pools over 2–4 consecutive days as well as the proximal tibia, femur midshaft, lumbar vertebrae (L1–L4), and remaining skeleton were analyzed for 3H, 45Ca, and calcium content. Bone turnover as assessed by urinary 3H-TC was greater in OVX + 1 mo compared to OVX + 3 mo rats up to 6 months postdose. 45Ca labeling efficiency (% dose/g Ca) was significantly higher than for 3H and labeling was higher in trabecular-rich than cortical-rich bone. This study affirms that a single administration of either 3H-TC or 45Ca is a useful approach to measuring bone turnover directly. The amount of label incorporation into bone was greater in bone sites that were more metabolically active and in all sites when closer vs farther from OVX. [ABSTRACT FROM AUTHOR]

The article presents information on a study related to the evaluation of 41Calcium, a radiotracer, as a new approach to assess changes in bone metabolism. It is stated that six women with low bone metabolism were labeled with 41Calcium and treated for 6 months with risedronate. It is also mentioned that the effect of treatment on bone can be recognized by using 41Calcium.

Abstract: Our group is interested in evaluating early effects of dietary interventions on bone loss. Postmenopausal women lose bone following reduction in estrogen which leads to increased risk of fracture. Traditional means of monitoring bone loss and effectiveness of treatments include changes in bone density, which takes 6 months to years to observe effects, and changes in biochemical markers of bone turnover, which are highly variable and lack specificity. Prelabeling bone with 41Ca and measuring urinary 41Ca excretion with accelerator mass spectrometry provides a sensitive, specific, and rapid approach to evaluating effectiveness of treatment. To better understand 41Ca technology as a tool for measuring effective treatments on reducing bone resorption, we perturbed bone resorption by manipulating dietary calcium in rats. We used 3H-tetracycline (3H-TC) as a proxy for 41Ca and found that a single dose is feasible to study bone resorption. Suppression of bone resorption, as measured by urinary 3H-TC, by dietary calcium was observed in rats stabilized after ovariectomy, but not in recently ovariectomized rats. [Copyright &y& Elsevier]

Abstract: The potential for measuring the radionuclides 41Ca and 55Fe was investigated with the 3MV tandem accelerator at VERA. Interestingly, up to now, no applications have been published for 55Fe using the technique of AMS. This is in strong contrast to 41Ca, which is routinely measured by medium and large tandem accelerators in various applications. Using CaF2 samples the quantification of 41Ca down to levels of a few 10−13 for the isotope ratio 41Ca/Ca has become possible with the use of the ΔTOF technique. Both nuclides, 41Ca and 55Fe were found to be of interest in nuclear astrophysics. A first application of 41Ca detection at VERA is the measurement of the 40Ca(n,γ)41Ca cross section at stellar temperatures. Similarly, of astrophysical interest is the production of 55Fe via neutron capture on 54Fe. To this end, different Ca and Fe blank and standard samples were investigated with the goal to establish an AMS method for 41Ca and 55Fe measurements. Indeed, low background levels for both radionuclides, 41Ca and 55Fe, were observed in these studies. The full separation power of VERA results in a very low detection limit, while still providing a high overall transmission. [Copyright &y& Elsevier]

Abstract: We measured concentrations of cosmogenic 41Ca in 37 diogenites, including 8 falls and 29 Antarctic finds, using accelerator mass spectrometry (AMS). The measured 41Ca concentrations in falls range from 2.8 to 9.3dpm/kg, those in Antarctic finds range from 1.6 to 28dpm/kg. The 41Ca concentrations in four of the falls agree within 10% with estimated saturation values based on spallation from Ti, Cr, Mn and the main target element, Fe. Four other diogenite falls and several Antarctic finds show elevated 41Ca concentrations, which are attributed to capture of thermal neutrons on 40Ca. The neutron-capture 41Ca contributions range from 0.1 to 1.5dpm/gCa. Monte Carlo based model calculations show that contributions of neutron-capture 41Ca are negligible (<0.05dpm/gCa) in diogenites with pre-atmospheric radii <20cm, but become dominant in diogenites larger than 30cm in radius and reach a maximum value of ∼5.6dpm/gCa in the center of objects with radii of 80–100cm. The contributions of neutron-capture 41Ca in diogenites were used to constrain their pre-atmospheric radii. Many Antarctic diogenites show low 41Ca concentrations, up to 60% below the saturation value determined for falls. From these low 41Ca concentrations we derive terrestrial ages up to ∼135kyr. We compare these terrestrial ages with those of other Antarctic achondrites and Antarctic chondrites and discuss the role of terrestrial weathering in limiting the lifetime of meteorites falling in different environments, i.e. Antarctic versus hot desert conditions. [Copyright &y& Elsevier]

Abstract: In a short time Be, C, Al, Cl, Ca and I accelerator mass spectrometry (AMS) have been established on the National Electrostatics Corporation (NEC) 5MV pelletron system at the Scottish Universities Environmental Research Centre (SUERC). While summarising the present performance of the system, this report will focus on the details of ion detection, which sample materials are used and the analytical procedures employed for each individual species during routine analysis. All rare isotope detection is with a single flexible detector and ion event analysis system, but switching of analysed species typically requires a detector reconfiguration. Configurations for routine 10Be, 14C, 26Al, 36Cl, 41Ca and 129I detection have been established and will be presented here. Notably, there has proven to be sufficient suppression of the isobaric interferences of 36Cl and 41Ca in the 5+ charge state using an argon gas stripper at a terminal voltage of 5.0MV to allow for routine analysis of these isotopes. [Copyright &y& Elsevier]

Abstract: The new SUERC AMS Laboratory was described at AMS-9. Since then there have been technological developments, added and improved analysis capability, the formation of additional complementary groups, the purchase of another instrument, and many samples measured. Be, C, Al, Cl, Ca and I-AMS are established with measured species changing weekly. Full-terminal potential running is now routine and 5MV is proving sufficient for all species. Ion detection and evaluation has also been improved by the use of even thinner detector windows as necessary and a more powerful on-line data analysis system. Routine radiocarbon measurement is to 4‰ reproducibility at middling current and graphite samples of as little as 100μg C can be accommodated. Even smaller samples can be measured as CO2 using He carrier in the gas capable ion source. Two new sample preparation laboratories at SUERC are the NERC Cosmogenic Isotope Analysis Facility and the SUERC/University of Glasgow Centre for Geosciences Cosmogenic Nuclide Laboratory. In particular these benefit from competitive Be-AMS and Cl-AMS performance. [Copyright &y& Elsevier]

Bone research is limited by the methods available for detecting changes in bone metabolism. While dual X-ray absorptiometry is rather insensitive, biochemical markers are subject to significant intra-individual variation. In the study presented here, we evaluated the isotopic labeling of bone using 41Ca, a long-lived radiotracer, as an alternative approach. After successful labeling of the skeleton, changes in the systematics of urinary 41Ca excretion are expected to directly reflect changes in bone Ca metabolism. A minute amount of 41Ca (100 nCi) was administered orally to 22 postmenopausal women. Kinetics of tracer excretion were assessed by monitoring changes in urinary 41Ca/40Ca isotope ratios up to 700 days post-dosing using accelerator mass spectrometry and resonance ionization mass spectrometry. Isotopic labeling of the skeleton was evaluated by two different approaches: (i) urinary 41Ca data were fitted to an established function consisting of an exponential term and a power law term for each individual; (ii) 41Ca data were analyzed by population pharmacokinetic (NONMEM) analysis to identify a compartmental model that describes urinary 41Ca tracer kinetics. A linear three-compartment model with a central compartment and two sequential peripheral compartments was found to best fit the 41Ca data. Fits based on the use of the combined exponential/power law function describing urinary tracer excretion showed substantially higher deviations between predicted and measured values than fits based on the compartmental modeling approach. By establishing the urinary 41Ca excretion pattern using data points up to day 500 and extrapolating these curves up to day 700, it was found that the calculated 41Ca/40Ca isotope ratios in urine were significantly lower than the observed 41Ca/40Ca isotope ratios for both techniques. Compartmental analysis can overcome this limitation. By identifying relative changes in transfer rates between compartments in response to an intervention, inaccuracies in the underlying model cancel out. Changes in tracer distribution between compartments were modeled based on identified kinetic parameters. While changes in bone formation and resorption can, in principle, be assessed by monitoring urinary 41Ca excretion over the first few weeks post-dosing, assessment of an intervention effect is more reliable ∼150 days post-dosing when excreted tracer originates mainly from bone. [ABSTRACT FROM AUTHOR]

Abstract: Selective ultra-trace determination of the long-lived radioisotope 41Ca has applications in environmental and biomedical research, as well as in cosmochemistry. We have conducted an intercomparison between the two currently available methods for measurement at these low (radio) activities: accelerator mass spectrometry (AMS) and resonance ionization mass spectrometry (RIMS). Three artificially produced 41Ca samples, primarily of cosmochemical importance, with isotopic abundances in the range of 10−11–10−10 were used and results of these measurements show good agreement between the two methods, within the experimental uncertainties. [Copyright &y& Elsevier]

Abstract: The long-living radioisotope 41Ca could overcome current limitations in assessing the impact of interventions on bone health in controlled human studies. Changes in bone Ca metabolism can be identified directly via the induced changes in 41Ca excretion from 41Ca-labelled bones via the n(41Ca)/n(40Ca) ratio in urine. A 41Ca dose material (IRMM-3703), for use in human studies, was produced by IRMM within the EC funded project OSTEODIET. The 41Ca base material was purified and the purified solution is certified for both isotopic composition and amount content by isotope dilution mass spectrometry. The 44Ca-enriched isotope reference material, IM-6009, was used as spike and the natural Ca reference material, IM-6008, was used for correction of procedural bias. Isotope ratio measurements were performed using thermal ionisation mass spectrometry (TIMS). The certified n(41Ca)/n(40Ca) ratio in IRMM-3703 is 0.012789 (58). A set of synthetic isotope mixtures, IRMM-3701, was prepared from IRMM-3703. It enables comparability of 41Ca measurement results in different laboratories and by different techniques. The IRMM-3701 series is derived from gravimetric mixing of IRMM-3703 and a Ca solution of natural isotopic composition. It covers n(41Ca)/n(40Ca) ratios in the range of 1.0114(68)×10−6 to 1.0524(71)×10−13. [Copyright &y& Elsevier]

In order to develop 41Ca application in biomedicine science, we are now setting up and developing the method for the measurement of 41Ca with accelerator mass spectrometry (AMS) at the China Institute of Atomic Energy (CIAE). A sensitivity of about 10-14 (41Ca/Ca) was obtained in the first 41Ca AMS measurement trial. We are also developing this methodology to investigate fluctuation in Ca2+ concentration in the human cell when exposed to carcinogenic substances (CS). Both 41Ca AMS measurement and its tracing for cell messenger methods are introduced. The results indicate that 41Ca tracing can be used for investigation of Ca2+, an important member of cell messengers, and for studying Ca2+ messenger related cancer caused by CS, and it is suggested that other cell problems related with Ca2+ can also be studied with 41Ca tracing measured by 41Ca AMS. [Copyright &y& Elsevier]

We discuss here developments carried out at the Gif-sur-Yvette Tandetron based AMS facility since AMS-8. These include installation of an automatic sample changer, measurement of 41Ca by three different procedures (PXD, CaH3− injection and CaF3− injection), limits of detection for 79Se and 126Sn obtained by the PXD technique, and some preliminary tests with U beams. We also briefly review the research programmes being pursued by the CSNSM at this facility. Finally, we discuss future prospects when the 14C activities at this facility are transferred to a new AMS facility in Saclay at the beginning of 2003. [Copyright &y& Elsevier]

An atom trap trace analysis system based on the technique of laser manipulation of neutral atoms is being developed to count individual 41Ca atoms present in natural samples with an isotopic abundance of 10−15. Trapping of all stable calcium isotopes has been demonstrated and single-atom counting has been realized. For the most abundant isotope, 40Ca (97% isotopic abundance), a magneto-optical trap loading rate of 2×1010 atoms/s has been reached at the overall capture efficiency of 1×10−4. System improvements could increase the efficiency by at least an order of magnitude. [Copyright &y& Elsevier]

Abstract: 41Ca measurement using CaF− was developed with the CIAE large tandem AMS system with 10 times larger efficiency than using . The strong 41K interference occurring with CaF− is greatly reduced by both chemistry in the sample preparation and by ion identification method. The background level obtained with blanks was 41Ca/Ca∼1.5×10−13. [Copyright &y& Elsevier]