Ecological half-life of radiocesium in white-tailed deer on the Department of Energy's Savannah River Site: What can a half century of field monitoring tell us?
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Environmental Sciences & Ecology↗
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Results for “half life”
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Half-life of 67 Cu
The half-life of 67 Cu was determined through serial gamma-ray spectrometry measurements of the dominant gamma emission (E γ : 184.6 keV; branching ratio: 48.7%) produced following β- decay. Data were collected consecutively for 1000 s per measurement, with a total of 3063 measurements over the duration of 36 days. The incidence rate for the 184.6 keV gamma-ray was determined from the spectral peak area and duration of each measurement. This rate was then corrected to account for detector dead-time, radioactive decay during each acquisition and drift in the computer clock in comparison to NIST nuclear clock. Least-squares regression analysis was performed to determine the half-life of 67 Cu. The result was 61.761 ± 0.004 h, which is the highest precision measurement to date, and marks a 24-fold precision improvement over the current Nuclear Data Sheets value.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
A New Approach for Calculating the Alpha-Decay Half-Life for the Heavy and Super-heavy Elements and an Exact A Priori Result for Beyllium-8
A new general method for calculating the alpha decay half-life is presented. The method predicts an a priori exact value for the beryllium-8 half-life. Beryllium-8 is an exception to the current alpha decay theory captured in the Geiger-Nuttal law. The new method predicts the beryllium-8 alpha half-life using only constants and measured isotopic mass. The method also reliably predicts all the heavier isotope alpha decay half-lives consistent with the Geiger-Nuttal law. With respect to current theory, the inability of the Geiger-Nuttal Law to predict the alpha-decay half-life in the case of beryllium-8 has led to consideration of other decay mechanisms for this isotope, such as fission for example. One result is that given the consistency of the new method presented here for all isotopes including an exact a priori result for beryllium-8, the evidence strongly suggests that the beryllium-8 decay is in fact an alpha decay. A second result is that the method definitively demonstrates that the entire rest mass of the two helium-4 electrons is converted to energy in the decay process and this energy becomes part of the emitted alpha particle kinetic energy.
07 ISOTOPE AND RADIATION SOURCES↗
Precision half-life determination for the β + emitter N 13
A new precision half-life measurement of 13 N has been conducted using the TwinSol β-counting station at the University of Notre Dame. Here, the measured value of $t^{new}_{1/2}$ = 597.05(19) s differs from the previous world value by about 2.8σ. An evaluation of the 13N half-life results in a $t^{world}_{1/2}$ = 597.19(22) s. Updated Standard Model predictions for the Fermi to Gamow-Teller mixing ratio ρ and its associated correlation parameters have been calculated using the new 13 N world half life in preparation for a future measurement of the mixing ratio. Finally, an ab initio no-core configuration interaction (NCCI) calculation for the B(GT) of this decay, carried out using the Daejeon16 interaction, has been carried out, revealing the need for higher-order chiral corrections.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurement of the 175 Hf half-life
Hafnium-175 is a useful radioisotope for numerous applications; however, its evaluated half-life (70 ± 2 days) has a large uncertainty. To enable a new measurement of the half-life, 175 Hf was produced via proton irradiation of natural lutetium and chemically purified. The 175 Hf sample was counted approximately once a month with three high-purity germanium detectors for 13 months (~5.5 half-lives). A 133 Ba standard was counted in an identical manner to quantify systematic uncertainties over the measurement period. In conclusion, the measured 175 Hf half-life is 69.90 ± 0.07 days, in agreement with the evaluated value, but with significantly reduced uncertainty.
150 ≤ A ≤ 189↗
Foam Fracturing Fluid Half-life Experimental Data
Foam thermal stability was studies at Temple University in collaboration with Oak Ridge National Lab (ORNL). The goal of this project is to explore thermally stable foams as hydrofracking fluid media for potential applications in enhanced geothermal system (EGS). Data generated from this project will allow researchers to explore foam as potential fracturing fluid. More than 800 data points on the half-life of foams are recorded in Excel files in the included archive resource (Half-life of Foams with Different Surfactants and Stabilizing Agents). The Excel file within each surfactant folder contains half-life data of the respective surfactant with different stabilizing agents, pressure, and temperature. The respective folders also contains Word files describing the details of the data included in the respective Excel sheet.
15 GEOTHERMAL ENERGY↗
Determination of the 161 Tb half-life
There is significant interest in the use of terbium radioisotopes for applications in cancer therapy and diagnosis. Of these, 161 Tb, a medium energy beta- and prolific auger emitter, is being investigated as a potential alternative to 177 Lu. The higher proportion of conversion electron and Auger electron emissions, and variety of low-energy gammas make 161 Tb an attractive targeted theranostic. As a product of nuclear fission, 161 Tb is also of importance to nuclear forensics. The current evaluated half-life of 6.89(2) d has a standard uncertainty that contributes significantly to the standard uncertainty of decay calculated activity determination. Furthermore, the accuracy of this evaluated half-life has been called into question by measurements reported recently at the Institute of Radiation Physics (IRP), Switzerland. In this work, the half-life of 161 Tb was measured at three independent laboratories located in the United Kingdom and United States of America for a total of five determinations using three independent measurement techniques. In conclusion, the half-life determined for 161 Tb of 6.9637(29) d confirms the observed 1 % relative increase observed by IRP, though the reported half-lives in this work and at IRP are significantly different (ζ-score = 3.1).
half-life↗
Half-life of Ge 71 and the gallium anomaly
Recent discussions about the origin of the so-called gallium anomaly have motivated a remeasurement of the half-life of 71 Ge. Here, we have conducted three separate measurements using dedicated planar Ge detectors—one with 55 Fe as a standard, one with 57 Co as a standard, and one standalone 71 Ge measurement. Our results yield a half-life of 11.468±0.008 days, which is consistent with, but significantly more precise than, the currently accepted value. With this experiment, the potential explanation of the gallium anomaly being due to an unexpectedly long 71 Ge half-life has been ruled out, leaving the anomaly's origin as an open question.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurement of the 136 Xe two-neutrino double-β-decay half-life via direct background subtraction in NEXT
Here, we report a measurement of the half-life of the 136 Xe two-neutrino double-β decay performed with a novel direct-background-subtraction technique. The analysis relies on the data collected with the NEXT-White detector operated with 136 Xe-enriched and 136 Xe-depleted xenon, as well as on the topology of double-electron tracks. With a fiducial mass of only 3.5 kg of Xe, a half-life of 2.34$_{-0.46}^{+0.80}$(stat)$_{-0.17}^{+0.30}$(sys)×10 21 yr is derived from the background-subtracted energy spectrum. The presented technique demonstrates the feasibility of unique background-model-independent neutrinoless double-β-decay searches.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Engineered IL-18 variants with half-life extension and improved stability for cancer immunotherapy
Background The pro-inflammatory cytokine, interleukin-18 (IL-18), plays an instrumental role in bolstering anti-tumor immunity. However, the therapeutic application of IL-18 has been limited due to its susceptibility to neutralization by IL-18 binding protein (IL-18BP), short in vivo half-life, and unfavorable physicochemical properties. Methods In order to overcome the poor drug-like properties of IL-18, we installed an artificial disulfide bond, removed the native, unpaired cysteines, and fused the stabilized cytokine to an IgG Fc domain. The stability, potency, pharmacokinetic and pharmacodynamic properties as well as efficacy of disulfide-stabilized IL-18 Fc-fusion (dsIL-18-Fc) were assessed via in vitro and in vivo studies. Results The stability and mammalian host cell production yields of dsIL-18-Fc were improved, compared to the wild-type (WT) cytokine, while maintaining its biological potency and interactions with IL-18 receptor α (IL-18Rα) and IL-18BP. Recombinant fusion of the cytokine to an IgG Fc domain provided extended half-life. Notably, despite maintaining sensitivity to IL-18BP, dsIL-18-Fc was effective at activating both T and natural killer (NK) cells, and elicited a strong anti-tumor response, either as a single agent, or in conjunction with anti-programmed cell death-ligand 1 (anti-PD-L1) therapy. Conclusions We engineered IL-18 for reinforced stability, extended half-life, and improved manufacturability. The therapeutic benefit of dsIL-18-Fc, coupled with a more favorable manufacturability profile and enhanced drug-like properties, underscores the potential utility of this engineered cytokine in cancer immunotherapy.
Immunology↗
Determination of the half-life of Ca-41 from measurements of Antarctic meteorites
Accelerator mass spectrometry is utilized to determine the half-life of Ca-41 from the decrease of its concentration with terrestrial age in five Antarctic meteorites and a recent fall. The meteorites were selected on the basis of their Cl-36 concentrations, which showed a span of terrestrial ages of about 600 ka, and on the basis of other cosmogenic nuclide concentrations which indicated that the meteorites had small preatmospheric sizes, and sufficiently long irradiation times in space that the concentrations of Ca-41 and Cl-36 were in secular equilibrium prior to the meteorites' fall to earth. The half-life of Ca-41 is determined at 103 + or - 7 ka. Topics discussed include the effects of undersaturation (short exposure time in space), shielding (the samples are from the interior of a large meteorite), and weathering on the cosmogenic nuclide concentrations in meteorites.
Klein, Jeffrey↗
Chemical separation of 146 Sm for half-life determination
Here, although methods for the chemical separation of samarium from a rock matrix are well established, chemical separation of samarium from non-natural isotopic impurities for the purpose of 146 Sm half-life measurement requires modifications to these procedures, as well as additional checks for effective separation. This work describes the chemical purification procedures associated with the 146 Sm source and the results from gamma spectroscopy. The purification procedure allowed for the quantitative determination of the number of 146Sm atoms using a modified isotope dilution technique. Alpha-decay counting of the sample will be applied in the future to determine the half-life of 146 Sm.
146Sm↗
Endocytosis of the non-catalytic ADAM23: Recycling and long half-life properties
A Disintegrin And Metalloprotease 23 (ADAM23) is a member of the ADAMs family of transmembrane proteins, mostly expressed in nervous system, and involved in traffic and stabilization of Kv1-potassium channels, synaptic transmission, neurite outgrowth, neuronal morphology and cell adhesion. Also, ADAM23 has been linked to human pathological conditions, such as epilepsy, cancer metastasis and cardiomyopathy. ADAM23 functionality depends on the molecule presence at the cell surface and along the secretory pathway, as expected for a cell surface receptor. Because endocytosis is an important functional regulatory mechanism of plasma membrane receptors and no information is available about the traffic or turnover of non-catalytic ADAMs, we investigated ADAM23 internalization, recycling and half-life properties. Here, we show that ADAM23 undergoes constitutive internalization from the plasma membrane, a process that depends on lipid raft integrity, and is redistributed to intracellular vesicles, especially early and recycling endosomes. Furthermore, we observed that ADAM23 is recycled from intracellular compartments back to the plasma membrane and thus has longer half-life and higher cell surface stability compared with other ADAMs. Our findings suggest that regulation of ADAM23 endocytosis/stability could be exploited therapeutically in diseases in which ADAM23 is directly involved, such as epilepsy, cancer progression and cardiac hypertrophy.
60 APPLIED LIFE SCIENCES↗
Half-life of Si-32 from tandem-accelerator mass spectrometry
A newly developed mass-spectrometry technique employing a tandem Van de Graaff accelerator together with a special beam-transport system and heavy-ion detector has been used to determine the half-life of Si-32. The result obtained, 108 plus or minus 18 yr, disagrees with the accepted value of 330 plus or minus 40 yr. The implications of the new half-life of Si-32, which is used for dating studies, are discussed.
Elmore, D.↗
Experimental Images and Videos of Foam Stability (Half-life)
The experimental data obtained in this project is the thermal stability data of various foams measured using the setup established at Temple University during this study. The setup is installed with a portable digital camera which can take images and videos of foam evolution at a given pressure and temperature condition. Consequently, the half-life data was recorded from the images/videos, which are used as a measure of the thermal stability for foams. Over the 3 years of this project, four different surfactants and five different stabilizing agents were studied. The surfactants are, Alfa Olefin Sulfonate (AOS), Sodium Dodecyl Sulphate (SDS), Tergitol (NP-40), and Cetyltrimethylammonium chloride (CTAC). The stabilizing agents are, guar gum, bentonite clay, crosslinking agents, silicon dioxide nanoparticles (60 to 70nm), and graphene oxide dispersions. Foam stability was evaluated at different temperatures between 100C and 200cC, while the foam generation pressure varied between atmospheric pressure (14.7 psi) and 1000 psi. The images are saved as .jpg file and videos are saved as .avi files.
15 GEOTHERMAL ENERGY↗
Precise half-life determination of 131 Ba and 125 Xe
Barium-131 and Xenon-125 are valuable radioisotopes with numerous scientific and medical applications. Here, we produced both isotopes via proton irradiation of a cesium iodide (CsI) target at the Brookhaven Tandem Van de Graaff accelerator (BTVG). Following irradiation, we conducted systematic γ-ray spectroscopy measurements at the National Nuclear Data Center (NNDC) decay station using a calibrated High-Purity Germanium (HPGe) detector, collecting data over a 2-month period (spanning approximately 4.5 half-lives for 131 Ba). Through careful analysis of the characteristic γ-ray emissions from both isotopes, we determined the half-life of 131 Ba to be 11.55(6) days, which agrees with the previously evaluated value. For 125 Xe, we measured a half-life of 16.56(8) hours, slightly lower than the evaluated value.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
RBC-/Cr-51/ half-life and albumin turnover in growing Beagle dogs during chronic radial acceleration
The effects of chronic centrifugation on growing Beagle dogs exposed to -2 or -2.6 Gx on albumin and RBC turnover rates, albumin concentration and space, and total blood volume were determined and compared with caged and run control of animals. Albumin-(I-125) and autologous RBC-(Cr-51) preparations were injected into all dogs at day 82 of the centrifugation periods, and the disappearance curves were determined by successive bleedings of the animals over the next 35 d, during which the centrifugation was continued. There were no differences in albumin turnover rates or space. Two populations of RBCs were found in both centrifugated groups, one with a normal half-life of 27 + or - 1 S.E.M. d, and one with a significantly (p less than 0.01) shorter half-life of 15 + or - 2 S.E.M. d. An absolute polycythemia was also observed in both centrifuged groups. The results suggest that chronic centrifugation acts through some as-yet unknown mechanism to affect RBC population kinetics.
Beckman, D. A.↗
New Direct Limit on Neutrinoless Double Beta Decay Half-Life of 128 $\mathrm{Te}$ with CUORE
The Cryogenic Underground Observatory for Rare Events (CUORE) at Laboratori Nazionali del Gran Sasso of INFN in Italy is an experiment searching for neutrinoless double beta (0νββ) decay. Its main goal is to investigate this decay in 130 Te, but its ton-scale mass and low background make CUORE sensitive to other rare processes as well. Here, in this Letter, we present our first results on the search for 0νββ decay of 128 Te, the Te isotope with the second highest natural isotopic abundance. We find no evidence for this decay, and using a Bayesian analysis we set a lower limit on the 128 Te 0νββ decay half-life of T 1/2 > 3.6 x 10 24 yr (90% CI). This represents the most stringent limit on the half-life of this isotope, improving by over a factor of 30 the previous direct search results, and exceeding those from geochemical experiments for the first time.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗