Abstract
This work presents the first direct measurement of the
93
Mo half-life. The measurement is a combination of high-resolution mass spectrometry for the determination of the
93
Mo concentration ...and liquid scintillation counting for determining the specific activity. A
93
Mo sample of high purity was obtained from proton irradiated niobium by chemical separation of molybdenum with a decontamination factor larger than 1.6 × 10
14
with respect to Nb. The half-life of
93
Mo 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
93
Mo decays to the metastable state
93m
Nb 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
93
Mo 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.
Measurement of the 145Sm half-life Kajan, I.; Pommé, S.; Pelczar, K. ...
Applied radiation and isotopes,
December 2021, 2021-12-00, 20211201, Letnik:
178
Journal Article
Recenzirano
Odprti dostop
The half-life of 145Sm has been measured by means of the reference source method with a HPGe detector. The long-lived radionuclide 44Ti was mixed into the source for reference. The time-dependency of ...the 145Sm/44Ti activity ratio was followed by assessing the count-rate ratio of their characteristic gamma-ray emissions at 61.2 keV (145Sm) and 67.9/78.3 keV (44Ti) in spectra recorded over periods of typically one day. In total, 220 measurements were performed over a period of 384 days or about one half-life period. The experiment and ensuing uncertainty budget are discussed in detail. Different error propagation is applied for random uncertainties, autocorrelated structures in the fit residuals, and potential systematic errors. The result for the 145Sm half-life, 345 (16) d, is compatible with the scarce literature values, however the experimental details of the old measurements were barely documented.
•Measured half-life of 145Sm by reference source method on a HPGe detector.•Used count ratio of 61.2 keV (145Sm) with reference peaks of 67.9 and 78.3 keV (44Ti).•Result T1/2(145Sm)=345 (16) d is consistent with recommended value of 340 (3) d.•Old experiments and data analysis are insufficiently documented.
Measurement of the 171Tm half-life Kajan, I.; S. Pommé; Heinitz, S.
Journal of radioanalytical and nuclear chemistry,
2022/1, Letnik:
331, Številka:
1
Journal Article
Recenzirano
The half-life of
171
Tm was measured by gamma-ray spectrometry, using the reference source method. The measured point-like source was prepared by homogenous mixing of
44
Ti with
171
Tm in order to ...obtain an identical detection geometry for both nuclides. The half-life of
171
Tm was determined by following the count-rate ratio between the gamma-ray emissions at 66.73 keV (
171
Tm) and 67.9/78.3 keV (
44
Ti). The measurement campaign consisted of 280 measurements acquired over a period of 449 days, corresponding to about 60% of the half-life value. The result for the
171
Tm half-life, 702.4 (70) d, is consistent with the currently recommended value, however the uncertainty assessment of the latter is poorly documented.
The European Research Council has recently funded HOLMES, a new experiment to directly measure the neutrino mass. HOLMES will perform a calorimetric measurement of the energy released in the decay of ...Formula: see textHo. The calorimetric measurement eliminates systematic uncertainties arising from the use of external beta sources, as in experiments with beta spectrometers. This measurement was proposed in 1982 by A. De Rujula and M. Lusignoli, but only recently the detector technological progress allowed to design a sensitive experiment. HOLMES will deploy a large array of low temperature microcalorimeters with implanted Formula: see textHo nuclei. The resulting mass sensitivity will be as low as 0.4 eV. HOLMES will be an important step forward in the direct neutrino mass measurement with a calorimetric approach as an alternative to spectrometry. It will also establish the potential of this approach to extend the sensitivity down to 0.1 eV. We outline here the project with its technical challenges and perspectives.
.
Ampoules of amorphous 99.5% enriched
13
C were irradiated at the PF1b neutron beam line at the high-flux ILL research reactor in order to produce
14
C atoms. The precise ratio of
14
C/
13
C was ...subsequently measured at the VERA Accelerator Mass Spectrometer, allowing the
13
C(n,
γ
)
14
C thermal cross section to be accurately determined. This is the first measurement of this cross section at sub-eV energies via this technique and the result of
1
.
52
±
0
.
07
mb for the thermal cross section is in good agreement with other recent measurements which were performed via Prompt Gamma-ray Activation Analysis.
Purpose
Glucagon-like peptide 1 (GLP-1) is an incretin hormone that appears to play a major role in the control of food intake. The aim of this investigation was to evaluate and quantify the ...association of circulating GLP-1 concentration with ad libitum total calorie and macronutrient intake.
Methods
One-hundred and fifteen individuals (72 men) aged 35 ± 10 years were admitted for an inpatient study investigating the determinants of energy intake. Ad libitum food intake was assessed during 3 days using a reproducible vending machine paradigm. Fasting plasma GLP-1 concentrations were measured on the morning of the first day and on the morning of the fourth day after ad libitum feeding.
Results
Plasma GLP-1 concentrations increased by 14% after 3 days of ad libitum food intake. Individuals overate on average 139 ± 45% of weight-maintaining energy needs. Fasting plasma GLP-1 on day 1 was negatively associated with carbohydrate intake (
r
= − 0.2,
p
= 0.03) and with daily energy intake from low fat–high simple sugar (
r
= − 0.22,
p
= 0.016).
Conclusion
Higher plasma GLP-1 concentrations prior to ad libitum food intake were associated with lower carbohydrate intake and lower simple sugar ingestion, indicating a possible role of the GLP-1 in the reward pathway regulating simple sugar intake.
Trial registration
ClinicalTrials.gov identifier: NCT00342732.
This paper describes the production and chemical separation of the 163Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the neutron ...cross section of the 163Ho isotope. For this purpose, several batches of enriched 162Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired 163Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed.
Large amounts of 10Be are produced at the PSI muon production facility by high-energy proton spallation in polycrystalline graphite. For the extraction of 10Be out of large amounts of carbon, ...pyrolysis followed by chemical purification has been performed. Approx. 270g of graphite from Target E92, which had received a total proton charge of 29 Ah between 2002 and 2005, have been burned at 1000°C in a stream of oxygen. The volatile radioactive oxidation product 3H2O was trapped in 3 water bubblers connected in series. The remainder, a white hygroscopic solid material mainly consisting of 7Li2O, 9/10BeO and 10/11B2O3, was dissolved in HF and subsequently purified by ion exchange chromatography. Radioactive impurities such as 22Na, 44Ti, 54Mn, 60Co, 101Rh, 133Ba and 172Hf have been separated from the final product. The purified material represents a mixture of approx. 6.5mg 9Be and 3.5mg (3.3MBq) 10Be. It is ready to be used for scientific investigations requiring large amounts of this precious isotope.
In animal models, a role in the regulation of energy expenditure (EE) has been ascribed to sphingolipids, active components of cell membranes participating in cellular signaling. In humans, it is ...unknown whether sphingolipids have a role in the modulation of EE and, consequently, influence weight gain. The present study investigated the putative association of EE and weight gain with sphingolipid levels in the human skeletal muscle, a component of fat-free mass (the strongest determinant of EE), in adipose tissue and plasma.
Twenty-four-hour EE, sleeping metabolic rate (SMR) and resting metabolic rate (RMR) were assessed in 35 healthy Native Americans of Southwestern heritage (24 male; 30.2±7.73 years). Sphingolipid (ceramide, C; sphingomyelin, SM) concentrations were measured in skeletal muscle tissue, subcutaneous adipose tissue and plasma samples. After 6.68 years (0.26-12.4 years), follow-up weights were determined in 16 participants (4 females).
Concentrations of C24:0, SM18:1/26:1 and SM18:0/24:1 in muscle were associated with 24-h EE (r=-0.47, P=0.01), SMR (r=-0.59, P=0.0008) and RMR (r=-0.44, P=0.01), respectively. Certain muscle sphingomyelins also predicted weight gain (for example, SM18:1/23:1, r=0.74, P=0.004). For specific muscle sphingomyelins that correlated with weight gain and EE (SM18:1/23:0, SM18:1/23:1 and SMR, r=-0.51, r=-0.41, respectively, all P<0.03; SM18:1/24:2 and RMR, r=-0.36, P=0.03), associations could be reproduced with SMR in adipose tissue (all r<-0.46, all P<0.04), though not in plasma.
This study provides preliminary, novel evidence, that specific muscle and adipose tissue sphingolipid compounds are associated with EE and weight gain in Native Americans of Southwestern heritage. Further studies are warranted to investigate whether sphingolipids of different body compartments act in concert to modulate energy balance in humans.
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