Juno spacecraft measurements of Jupiter's gravity imply a dilute core

Stars and planetary system

Biokinetic modelling of natural thorium in humans by ingestion.

The retention of naturally occurring thorium (228Th, 230Th, 232Th) in model compartments and its daily urinary and faecal excretion after acute and chronic injections and ingestions were calculated for male and female subjects of six age groups based on the current age-dependent biokinetic model for thorium (Th) recommended by the International Commission on Radiological Protection (ICRP). The results are tabulated in a database. The calculated contents of 228,230,232Th in organs or tissues using their reference concentrations in foodstuffs for the European population are compared with autopsy data. The model prediction of 232Th in whole body for a 50-year-old unexposed person is 22 mBq, 86% of that in skeleton, 9.7% in other soft tissues, 3.4% in liver, 0.7% in kidneys and 0.01% in blood. The modelling predicts lower contents of the natural Th isotopes in whole body, especially in blood compared with measured data for the unexposed public. Modelled 232Th daily urinary excretions are 5 to 10 times less than bio-assay data from the authors' own laboratory

A compartmental model of uranium in human hair for protracted ingestion of natural uranium in drinking water.

To predict uranium in human hair due to chronic exposure through drinking water, a compartment representing human hair was added into the uranium biokinetic model developed by the International Commission on Radiological Protection (ICRP). The hair compartmental model was used to predict uranium excretion in human hair as a bioassay indicator due to elevated uranium intakes. Two excretion pathways, one starting from the compartment of plasma and the other from the compartment of intermediate turnover soft tissue, are assumed to transfer uranium to the compartment of hair. The transfer rate was determined from reported uranium contents in urine and in hair, taking into account the hair growth rate of 0.1 g d(-1). The fractional absorption in the gastrointestinal tract of 0.6% was found to fit best to describe the measured uranium levels among the users of drilled wells in Finland. The ingestion dose coefficient for U-238, which includes its progeny of Th-234, Pa-234, and Pa-234, was calculated equal to 1.3 X 10(-8) Sv Bq(-1) according to the hair compartmental model. This estimate is smaller than the value of 4.5 X 10(-8) Sv Bq(-1) published by ICRP for the members of the public. In this new model, excretion of uranium through urine is better represented when excretion to the hair compartment is accounted for and hair analysis can provide a means for assessing the internal body burden of uranium. The model is applicable for chronic exposure as well as for an acute exposure incident. In the latter case, the hair sample can be collected and analyzed even several days after the incident, whereas urinalysis requires sample collection shortly after the exposure. The model developed in this study applies to ingestion intakes of uranium

Improvements in routine internal monitoring— an overview of the IDEA project.

The IDEA project aimed to improve the assessment of incorporated radionuclides through developments of advanced in vivo and bioassay monitoring techniques and making use of such enhancements for improvements in routine monitoring. Many of these findings are not new in the sense that they are being already employed in advanced laboratories or for specialised applications. The primary goal was to categorise those new developments regarding their potential and eligibility for the routine monitoring community. Attention has been given to in vivo monitoring techniques with respect to detector characteristics and measurement geometry to improve measurement efficiency with special attention to low energy gamma emitters. Calibration—specifically supported by or through methods of numerical simulation—have been carefully analysed to reduce overall measurement uncertainties and explore ways to accommodate the individual variability based on characteristic features of a given person. For bioassay measurements at low detection limits, inductively coupled plasma mass spectroscopy offers significant advantages both in accuracy, speed, and sample preparation. Specifically, the determination of U and Th in urine and the associated models have been investigated. Finally, the scientific achievements have been analysed regarding their potential to offer benefits for routine monitoring. These findings will be presented in greater detail in other papers at this conference, whereas this paper intends to give an overview and put both the scientific achievements as well as the derived benefits into perspective

Comparing Jupiter interior structure models to Juno gravity measurements and the role of a dilute core

International audienceThe Juno spacecraft has measured Jupiter's low-order, even gravitational moments, $J_2$--$J_8$, to an unprecedented precision, providing important constraints on the density profile and core mass of the planet. Here we report on a selection of interior models based on ab initio computer simulations of hydrogen-helium mixtures. We demonstrate that a dilute core, expanded to a significant fraction of the planet's radius, is helpful in reconciling the calculated $J_n$ with Juno's observations. Although model predictions are strongly affected by the chosen equation of state, the prediction of an enrichment of $Z$ in the deep, metallic envelope over that in the shallow, molecular envelope holds. We estimate Jupiter's core to contain an 7--25 Earth mass of heavy elements. We discuss the current difficulties in reconciling measured $J_n$ with the equations of state, and with theory for formation and evolution of the planet

Arbeitsstrukturierung und Hoeherqualifizierung in der Rollenkettenfertigung - berufspaedagogische Begleitforschung Schlussbericht. Abschlussdatum: Juni 1981

TIB: RN 7543 (84-045) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Implementation of bioassay methods to improve assessment of incorporated radionuclides.

The present work which was carried out in the framework of an EU project (IDEA: Internal Dosimetry—Enhancements in Application; Contract Number: FIKR CT2001 00164) shall provide commonly acceptable guidelines for optimum performance of ICP-MS measurements with focus on urinary measurements of uranium, thorium and actinides. From the results of this work it is recommended that, whenever feasible, 24 h urine sampling should be conducted to avoid large uncertainties in the quantitation of daily urinary excretion values. For storage, urine samples should be acidified and kept frozen before analysis. Measurement of total uranium in urine by ICP-MS at physiological levels (<10 ng·l–1) requires no sample preparation besides UV photolysis and/or dilution. For the measurement of thorium in urine by ICP-MS, it can be concluded, that salt removal from the urine samples is not recommended. For the measurement of actinides in urine it is shown that ICP-MS is well-suited and a good alternative to alpha-spectrometry for isotopes with T1/2>5x104 years. In general, ICP-MS measurements are an easy, fast and cost-saving methodology. New improved measuring techniques (HR-SF-ICP-MS) with detection limits in urine of 150 pg·l–1 (1.9 µBq·l–1) for 238U, 30 pg·l–1 (2.4 µBq·l–1) for 235U and 100 pg·l–1 (0.4 µBq·l–1) for 232Th, respectively, meet all necessary requirements. This method should therefore become the routine technique for incorporation monitoring of workers and of members of the general public, in particular for uranium contamination