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First direct determination of the ⁹³Mo half-life.

ABSTRACT: This work presents the first direct measurement of the ⁹³Mo half-life. The measurement is a combination of high-resolution mass spectrometry for the determination of the ⁹³Mo concentration and liquid scintillation counting for determining the specific activity. A ⁹³Mo sample of high purity was obtained from proton irradiated niobium by chemical separation of molybdenum with a decontamination factor larger than 1.6 × 10¹⁴ with respect to Nb. The half-life of ⁹³Mo was deduced to be 4839(63) years, which is more than 20% longer than the currently adopted value, whereas the relative uncertainty could be reduced by a factor of 15. The probability that the ⁹³Mo decays to the metastable state ^93mNb was determined to be 95.7(16)%. This value is a factor of 8 more precise than previous estimations. Due to the man-made production of ⁹³Mo in nuclear facilities, the result leads to significantly increased precision for modelling the low-level nuclear waste composition. The presented work demonstrates the importance of chemical separations in combination with state-of-the-art analysis techniques, which are inevitable for precise and accurate determinations of nuclear decay data.

SUBMITTER: Kajan I

PROVIDER: S-EPMC8492754 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundCationic polyacrylamide copolymers (PAMs) are used for sludge dewatering in municipal waste water treatment and might enter the environment by spreading of the sludge on agricultural land. Concern has been expressed since little is known about the degradation of PAMs in soils. To obtain detailed information on the polymer's fate in the soil compartment, the degradation of 14C-radiolabelled PAM in an outdoor lysimeter was studied.ResultsNo plant uptake and leaching of radioactivity was observed. There was practically no vertical movement of polymer and no transformation products found at the end of the study. For the top 10 cm soil layer, a mass balance was established throughout the study. About 10% of applied radioactivity was not extractable from soil even with a matrix destructive method, and this was concluded to be bound residue. Characterization of extractable radioactivity by means of GPC-analysis showed a significant decrease of the molecular weight of the PAM with time. The decrease in molecular weight indicates a breakdown of the polymer backbone (the C-C-chain), and is assumed to be primary degradation. The total radioactivity content in the 10 cm top soil layer was quantified every 6 months over a period of 3 years. The results show a significant decrease of the total radioactivity over time and this is defined as ultimate degradation following the definition of OECD and EPA. Based on the data, a half-life time of 2.0 × 103 days and a rate constant of 0.00035/day were calculated. With a χ2 of 12.0 the results of the calculation are thus valid and reliable. The rate constant indicates a mineralization of 22.5% within a period of 2 years based on the total recovered radioactivity. This half-life time is solely based on mineralization and does not take into account the degradation of the polymer backbone, hydrolysis of the side chains, incorporation into the soil matrix, and thus is a conservative approach.Conclusions14C-PAM degrades very slowly in soil after land-spreading as a component of sewage sludge. Even in a very conservative evaluation which only considered the loss of radioactivity, a half-life time of 5.4 years was determined.

Project description:BackgroundEvidence linking breastfeeding to reduced risk of developing childhood obesity is inconclusive, yet previous studies have not considered variation in specific components of breast milk that may affect early development.ObjectiveWe examined whether differences in the composition of human milk oligosaccharides (HMOs) correlate with infant growth and body composition at 1 and 6 mo of age.DesignTwenty-five mother-infant dyads were recruited from the University Hospital at the University of Oklahoma Health Sciences Center. Infants were breastfed for 6 mo. Breast-milk and infant measures were obtained at 1 and 6 mo of infant age. HMO composition was analyzed by high-pressure liquid chromatography, and infant growth (length and weight) and body composition (percentage fat, total fat, lean mass) were measured by dual-energy X-ray absorptiometry. Relations between HMOs and infant growth and body composition were examined by using multiple linear regression. A priori covariates included maternal prepregnancy body mass index, pregnancy weight gain, and infant age and sex.ResultsHigher HMO diversity and evenness at 1 mo were associated with lower total and percentage fat mass at 1 mo. At 1 mo, each 1-μg/mL increase in lacto-N-fucopentaose (LNFP) I was associated with a 0.40-kg lower infant weight (P = 0.03). At 6 mo, each 1-μg/mL increase in LNFPI was associated with a 1.11-kg lower weight (P = 0.03) and a 0.85-g lower lean mass (P = 0.01). At 6 mo, each 1-μg/mL increase in LNFPI was associated with a 0.79-g lower fat mass (P = 0.02), whereas disialyl-lacto-N-tetraose and LNFPII were associated with a 1.92-g (P = 0.02) and 0.42-g (P = 0.02) greater fat mass, respectively. At 6 mo, each 1-μg/mL increase in fucosyl-disialyl-lacto-N-hexaose and lacto-N-neotetraose was associated with 0.04% higher (P = 0.03) and 0.03% lower (P < 0.01) body fat, respectively.ConclusionThese findings support the hypothesis that differences in HMO composition in mother's milk are associated with infant growth and body composition. This trial was registered at clinicaltrials.gov as NCT02535637.

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First direct determination of the ⁹³Mo half-life.

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First direct determination of the ⁹³Mo half-life.