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Background: Several research groups have explored the potential of scandium radionuclides for theragnostic applications due to their longer half-lives and equal or similar coordination chemistry between their diagnostic and therapeutic counterparts, as well as lutetium-177 and terbium-161, respectively. Unlike the gallium-68/lutetium-177 pair, which may show different in-vivo uptake patterns, the use of scandium radioisotopes promises consistent behaviour between diagnostic and therapeutic radiopeptides. An advantage of scandium's longer half-life over gallium-68 is the ability to study radiopeptide uptake over extended periods and its suitability for centralized production and distribution. However, concerns arise from scandium-44's decay characteristics and scandium-43's high production costs. This study aimed to evaluate the dosimetric implications of using scandium radioisotopes with somatostatin analogues against gallium-68 for PET imaging of neuroendocrine tumours. Methods: Absorbed dose per injected activity (AD/IA) from the generated time-integrated activity curve (TIAC) were estimated using the radiopeptides [43/44/44mSc]Sc- and [68Ga]Ga-DOTATATE. The kidneys, liver, spleen, and red bone marrow (RBM) were selected for dose estimation studies. The EGSnrc and MCNP6.1 Monte Carlo (MC) codes were used with female (AF) and male (AM) ICRP phantoms. The results were compared to Olinda/EXM software, and the effective dose concentrations assessed, varying composition between the scandium radioisotopes. Results: Our findings showed good agreement between the MC codes, with − 3 ± 8% mean difference. Kidneys, liver, and spleen showed differences between the MC codes (min and max) in a range of − 4% to 8%. This was observed for both phantoms for all radiopeptides used in the study. Compared to Olinda/EXM the largest observed difference was for the RBM, of 21% for the AF and 16% for the AM for scandium- and gallium-based radiopeptides. Despite the differences, our findings showed a higher absorbed dose on [43/44Sc]Sc-DOTATATE compared to its 68Ga-based counterpart. Conclusion: This study found that [43/44Sc]Sc-DOTATATE delivers a higher absorbed dose to organs at risk compared to [68Ga]Ga-DOTATATE, assuming equal distribution. This is due to the longer half-life of scandium radioisotopes compared to gallium-68. However, calculated doses are within acceptable ranges, making scandium radioisotopes a feasible replacement for gallium-68 in PET imaging, potentially offering enhanced diagnostic potential with later timepoint imaging. [ABSTRACT FROM AUTHOR]

Today, nuclear reactors, especially small reactors, have been significantly welcomed in different countries and have various applications, including use as desalination plants, naval propulsions, etc. During the operation of the reactor, different types of radioisotopes are produced, some of which have very high activity and half-life. The type and amount of radioisotopes produced depends on the type of fuel used, the level of enrichment and the operating time of the reactor. The atomic density and activity of the most important radioisotopes for a typical reactor with two types of high and low enrichment fuel have been calculated in terms of time using MCNPX and CINDER codes. The activity of some of these radioisotopes is high and it is necessary to pay attention to possible environmental hazards. In this research, using the MCNPX Monte Carlo code, the core of a small nuclear reactor proposed as a Virginia class submarine propulsion with a power of 150 MWth was modeled. Using the BURN and KCODE cards in this code as well as the CINDER code, the fuel burnup calculations of the core of this naval reactor have been performed. For this reactor, there are two types of metal alloy fuels, including the high-enrichment UO2-Zr fuel and the low-enrichment U-10Mo fuel, and fuel burnup calculations have been performed for both fuels. After calculations, different types of radioisotopes were identified and changes in atomic density and activity quantities were calculated for the most important of these radioisotopes with high half-life during cycle and compared. [ABSTRACT FROM AUTHOR]

The long-lived fission product 151Sm (T1/2 ≈ 90 y) present in archived dissolved Trinity nuclear test debris samples was analyzed using liquid scintillation counting and the results were compared to the expected values based upon historical analysis results. The measured 151Sm activities were found to agree with the expected values within experimental error. This demonstration validates the use of this technique in situations where the sample is too old for traditional shorter half-life radioactive fission product signatures such as 99Mo (T1/2 = 2.75 d), 97Zr (T1/2 = 16.7 h), 147Nd (T1/2 = 10.98 d), and 153Sm (T1/2 = 46.3 h), or too dilute for determining fissions through stable isotope ratio measurements. [ABSTRACT FROM AUTHOR]

Conjugated microporous polymers (CMPs) have attracted great interest due to their high surface area, porosity and conjugacy, which could be potentially applied in pollutant adsorption, heterogeneous photocatalysis and super capacitor. Iodine 129 (129I) and iodine 131 (131I), as the common volatile radioactive products in nuke waste, have a long radioactive half-life, which is an important issue all the time. Here, two novel conjugated microporous polymers (TPAsTr-CMP and TPAPyD-CMP), which are rich in N element, were synthesized via Suzuki reaction and characterized through FTIR, 13C NMR, SEM, TGA and etc. The surface areas calculated by BET are 449.1 m2/g for TPAsTr-CMP and 15.6 m2/g for TPAPyD-CMP, respectively. The iodine adsorption experiments at 350 K exhibited that the iodine uptake of TPAsTr-CMP was up to 3.52 g/g; while TPAPyD-CMP had the iodine uptake of 2.84 g/g. For dissolved iodine in cyclohexane, the TPAPyD-CMP performed a better adsorption capacity than TPAsTr-CMP. The adsorption capacity of TPAPyD-CMP was 333.8 mg/g, when initial iodine concentration was 500 mg/L, while that of TPAsTr-CMP was only 104.3 mg/g. The adsorption capacity to iodine should be attributed to their high surface area, effective adsorptive sites and expanded π-conjugated network. [ABSTRACT FROM AUTHOR]

Precise determination of half-lives of 167Tm and 168Tm are important for their application in nuclear medicine diagnostics, nuclear forensics, and other nuclear data measurements. We produced 167Tm and 168Tm sources using an α-particle beam bombarded 165Ho target and a series purification steps. A series of 173 measurements was performed over a period of 44 days using a high-purity germanium (HPGe) detector to track the count rate change as a function of time by following the 207.8 keV and 531.5 keV γ-lines to determine the radioactive decay half-life of 167Tm. The measurement of half-life of 168Tm ground state has been performed using the same HPGe γ-ray spectrometer to observe γ-lines at 198.3 keV, 816.0 keV, 184.3 keV, 741.4 keV and 914.9 keV. Weighted least-squares fits of exponential decay curves were performed for the dataset of each γ-ray emission, with final determined half-lives of 9.250(15) d and 93.41(12) d for 167Tm and 168Tm, respectively. The uncertainty budgets are presented and discussed in detail. Our result of 167Tm half-life is consistent with the Evaluated Nuclear Structure Data File (ENSDF) recommended half-life of 9.25(2) d. The outcome of 168Tm half-life determination is longer than the ENSDF recommended half-life of 93.1(2) d. Further independent measurements would be ideal to resolve the discrepancy. • The half-lives obtained for 167Tm and 168Tm are 9.250(15) days and 93.41(12) days, respectively. • The 168Tm half-life value of 93.41(12) d determined in this work deviates by 0.33% from the recommended value of 93.1(2) d. • The half-life of 168Tm determined by the PMM method was 93.21(12) d. [ABSTRACT FROM AUTHOR]

The 120gI, as a positron emitter radioisotope with a suitable half-life of 1.35 h, can be used for Positron Emission Tomography (PET) in nuclear medicine. In this study, the range of proton particles in the enriched 122Te target was computed by SRIM and GEANT4 codes and compared. Moreover, the production yield of thick and thin targets and the cross-section of the 122Te(p,3n)120gI reaction were calculated using GEANT4, EMPIRE, and TALYS codes. The Composite Gilbert Cameron Model (CGCM), Back Shifted Fermi Gas Model (BSFGM), General Super Fluid model (GSM), and Optical Model Potential Spherical (OMPs) models of the TALYS code were selected to calculate the cross-section of the 122Te(p,3n)120gI reaction. Comparing the obtained simulation data with the experimental data revealed their good agreement. [ABSTRACT FROM AUTHOR]

Methods for the evaluation of the accidental coincidences counting rates in triple-to-double coincidences ratio (TDCR) liquid scintillation (LS) measurements have been proposed recently. This study shows how these corrections can be extended to two detector systems, such as commercial LS counters, or four-detector systems used for the compton source efficiency tracing (CSET) method. The significance of performing corrections for accidental coincidences in low-activity LS counting or TDCR measurements is demonstrated. The impact of accidental coincidences on the determination of half-life of radioisotopes is also shown. [ABSTRACT FROM AUTHOR]

We analyze the 55 134 Cs â†' 56 134 Ba and 55 135 Cs â†' 56 135 Ba β âˆ' decays, which are crucial production channels for Ba isotopes in asymptotic giant branch (AGB) stars. We calculate, starting from relativistic quantum mechanics, the effects of multichannel scattering onto weak decays, including nuclear and electronic excited states (ESs) populated above ≃10 keV, for both parent and daughter nuclei. We find increases in the half-lives for T > 108 K (by more than a factor of 3 for 134Cs) as compared to previous works based on systematics. We also discuss our method in view of these previous calculations. An important impact on half-lives comes from nuclear ES decays, while including electronic temperatures yields further increases of about 20% at energies of 10â€"30 keV, typical of AGB stars of moderate mass (M ≲ 8 M ⊙). Despite properly considering these effects, the new rates remain sensitively lower than the Takahashi & Yokoi values, implying longer half-lives at least above 8â€"9 keV. Our rate predictions are in substantial accord with recent results based on the shell model, and strongly modify branching ratios along the s -process path previously adopted. With our new rate, nucleosynthesis models well account for the isotopic admixtures of Ba in presolar SiC grains and in the Sun. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ever-increasing emission of uranium poses a threat to ecosystems and human health. • Modern electrochemical sensors provide a unique choice for on-site fast monitoring of trace uranyl. • A probe material is the key component of the sensors with high performances. • Biomaterials, polymers, and 2D materials are used as probe materials based on different sensing principles. • Fabrication of the sensors for environmental water monitoring is under-researched. Uranium, highly chemically toxic and radioactive with a long half-life, poses environmental risks due to activities like uranium mining, refining, and nuclear power plant operations. Detecting uranyl ion in real-time is crucial to assess human health risks and control uranium pollution. Electrochemical sensing offers advantages such as sensitivity, selectivity, simplicity, rapidity, and cost-effectiveness, making it ideal for on-site detection of uranyl ion. This paper summarizes recent research progress in electrochemical detection of uranyl. Various techniques including cyclic voltammetry, differential pulse voltammetry, stripping voltammetry, and electrochemical impedance spectroscopy are discussed along with their respective advantages. Detection methods utilizing electrode-modified functional materials like biomaterials, polymers, and nanomaterials are investigated. Probes like DNAzyme, ion-imprinted polymers, and 2D materials are highlighted for their detection mechanism and effectiveness. Electrochemical sensing with these probes achieves nanomolar-level detection limits (nM) with excellent stability and selectivity, suggesting practical applications. Lastly, predictions are made regarding sensing mechanisms, electrode material selection, and adaptability to field conditions for electrochemical detection of uranyl ion. [ABSTRACT FROM AUTHOR]

Disruption of the glutamatergic homeostasis is commonly observed in neurological diseases and has been frequently correlated with the altered expression and/or function of astrocytic high-affinity glutamate transporters. There is, however, a growing interest for the role of the cystine-glutamate exchanger system xc– in controlling glutamate transmission. This exchanger is predominantly expressed in glial cells, especially in microglia and astrocytes, and its dysregulation has been documented in diverse neurological conditions. While most studies have focused on measuring the expression of its specific subunit xCT by RT-qPCR or by Western blotting, the activity of this exchanger in tissue samples remains poorly examined. Indeed, the reported use of sulfur- and carbon-radiolabeled cystine in uptake assays shows several drawbacks related to its short radioactive half-life and its relatively high cost. We here report on the elaborate validation of a method using tritiated glutamate as a substrate for the reversed transport mediated by system xc–. The uptake assay was validated in primary cultured astrocytes, in transfected cells as well as in crude synaptosomes obtained from fresh nervous tissue samples. Working in buffers containing defined concentrations of Na+, allowed us to differentiate the glutamate uptake supported by system xc– or by high-affinity glutamate transporters, as confirmed by using selective pharmacological inhibitors. The specificity was further demonstrated in primary astrocyte cultures from transgenic mice lacking xCT or in cell lines where xCT expression was genetically induced or reduced. As such, this assay appears to be a robust and cost-efficient solution to investigate the activity of this exchanger in physiological and pathological conditions. It also provides a reliable tool for the screening and characterization of new system xc– inhibitors which have been frequently cited as valuable drugs for nervous disorders and cancer. [ABSTRACT FROM AUTHOR]

Rare event search experiments using germanium detectors are performed in underground laboratories to minimize the background induced by cosmic rays. However, the cosmogenic activation of cupreous detector components on the ground generates long half-life radioisotopes and contributes to the background level. We measured cosmogenic activation with 142.50 kg of copper bricks after 504 days of exposure at an altitude of 2469.4 m outside the China Jinping Underground Laboratory (CJPL). The specific activities of the cosmogenic nuclides produced in the copper bricks were measured using a low-background germanium gamma-ray spectrometer at CJPL. The production rates at sea level, in units of nuclei/kg/day, were 18.6 ± 2.0 for 54 Mn, 9.9 ± 1.3 for 56 Co, 48.3 ± 5.5 for 57 Co, 51.8 ± 2.5 for 58 Co, and 39.7 ± 5.7 for 60 Co. The measurement will help to constrain cosmogenic background estimation for rare event searches using copper as a detector structure and shielding material. Based on the measured production rates, the impact of the cosmogenic background in cupreous components of germanium detectors on the next generation CDEX-100 experiment was assessed with the expected exposure history above ground. [ABSTRACT FROM AUTHOR]

Aim: In a Nuclear Medicine department, the risk of external and internal contamination in radiation workers is much higher than in other medical radiation facilities. The risk associated with both types of contaminations should be quantified to estimate the radiation dose received by the personal. Here, we designed an in vitro model to see the impact of internal and external contamination of F-18 and Technetium-99 m (Tc-99 m) on DNA damages. Methodology: Chinese hamster lung fibroblast V79 was used for all of the experiments. Irradiation was performed internally and externally (scenarios activity is mixed with the cell line [Internal] and activity kept at 1 cm distance from cell line [external]) using two different diagnostic radioactive sources (Tc-99 m and F-18) of known quantity 37 MBq. Total cumulated activity (MBq-min) was calculated up to one half-life of sources for both internal and external setups. An alkaline single gel electrophoresis technique (comet assay) was used for DNA damage analysis. Olive tail moment (OTM) was used to characterize DNA damage. Results: We have not observed any significant difference (P > 0.05) in OTM between internal and external irradiation for cumulated activity presented before one half-life of both diagnostic isotopes. However, a significant difference in OTM was noted between internal and external irradiation for cumulated activity presented at one half-life of radioactive sources (P < 0.05). DNA damage with internal exposure was found to be 17.28% higher for F-18 and 23% higher for Tc-99 m than external exposure at one half-life of radioactive sources. Overall, we noted greater DNA damage in F-18 as compared to Tc-99 m. Conclusions: Our in vitro study practically demonstrated that internal contamination is more hazardous than external exposure. [ABSTRACT FROM AUTHOR]

Today, microelectromechanical system (MEMS) technology plays an important role in human daily life. One of the main items in MEMS design is the use of a small battery with a long life. In this work, the 90Sr radioisotope with a half-life of 28.8 years and an activity of 16.328 mCi was considered as a radioactive source. First, the 90Sr cylindrical source was designed with a gold substrate and antimony side surface coating. Then, the optimum radius and thickness of the source were investigated. Next, the optimized 90Sr cylindrical source was considered as the direct charge nuclear battery source. In the next step, the effect of collector coating on collector efficiency was investigated. Then, different positions were considered for collector placement, substrate and side surface coating and the best mode was selected. The purpose is to determine the smallest size possible for a direct charge nuclear battery with the maximum amount of short circuit current. Finally, by comparing the results of simulations performed with Monte Carlo N–Particule Transport (MCNPX) code, the present work concluded that the best parameters for direct charge nuclear battery are the use of beryllium and the 90Sr radioisotope as collector coating and source, respectively, source thickness of 0.01 µm, source radius of 37.5 µm, collector thickness 0.01 µm and collector distance from source about 3.75 µm. Under these parameters, the short circuit current is 0.092 fA. In this case, the designed direct charge nuclear battery has the highest short circuit current and the smallest dimension possible. If the dimensions of the optimized nuclear battery are 100 times, i.e., the thickness of the source increases from 0.01 to 1 µm and the radius of the source increases from 37.5 to 3750 µm, only about 2.92% of the source efficiency decreases, but the activity is 106 times more. In other words, the activity increases from 0.016328 µCi to 16.328 mCi; therefore, the short circuit current of this direct charge nuclear battery reached 0.078 nA, which is suitable for use in MEMS. Also, the collector height of this battery is 1960 µm, its radius is 3850 µm, and its thickness 1 µm. [ABSTRACT FROM AUTHOR]

137Cs is a long-lived (30-year radioactive half-life) fission product dispersed globally by mid-20th century atmospheric nuclear weapons testing. Here we show that vegetation thousands of kilometers from testing sites continues to cycle 137Cs because it mimics potassium, and consequently, bees magnify this radionuclide in honey. There were no atmospheric weapons tests in the eastern United States, but most honey here has detectable 137Cs at >0.03 Bq kg−1, and in the southeastern U.S., activities can be >500 times higher. By measuring honey, we show regional patterns in the biogeochemical cycling of 137Cs and conclude that plants and animals receive disproportionally high exposure to ionizing radiation from 137Cs in low potassium soils. In several cases, the presence of 137Cs more than doubled the ionizing radiation from gamma and x-rays in the honey, indicating that despite its radioactive half-life, the environmental legacy of regional 137Cs pollution can persist for more than six decades. Radioactive 137Cs is a fission product remaining in the environment from mid-20th century nuclear testing. Here the authors show that vegetation thousands of kilometers from testing sites continues to cycle 137Cs, and consequently, bees magnify this contaminant in honey in regions with low soil potassium. [ABSTRACT FROM AUTHOR]

Evaluation of nuclear structure data is a world wide effort to standardize the published nuclear data. This standardization led to generation of table of isotopes, Nuclear Data sheets, Nuclear Wallet Cards etc. This paper deals with two aspects of evaluation of nuclear structure data. First, the problems arising out of some of the recent publications and how to tackle them at pre-publication stage. Second, there is large amount of experimental data available on the NNDC site1. Of these data the half-life values, spin and parity is the most important set of values to understand the nucleon-nucleon interaction within a given nucleus. However, it is observed in our work that the quantum of half-life, spin and parity values measured, in comparison to the number of excited states, in any given nuclei, is very low. Thus, indicating that very few experimental results are available in terms of half-life measurements, spin measurements and determination of parity. This survey besides being an indicator of the quantum of measurements carried out can also be a guide to future experimentalists by highlighting the areas of nuclear chart where measurements are fewer in number. [ABSTRACT FROM AUTHOR]

The half-life of radiocarbon (14C) is 5700 ± 30 yr, which makes it particularly useful for dating in archaeology. However, only an exceptional hindrance of the beta decay from 14C to 14N—a so-called Gamow-Teller ß-decay—makes this half-life so long. A normal strength would result in a half-life of only a few days, completely useless for archaeological dating. The unusual hindrance is based on the nuclear structure of the two nuclei, resulting in strongly destructive interferences of the nuclear transition matrix element. Nuclear model calculation with great computational efforts have been performed in the literature to reproduce the very low transition probability. Here, we will attempt to describe the nuclear physics behind this most unusual half-life. [ABSTRACT FROM AUTHOR]

Measurement and interpretation of the distribution patterns of indoor 220Rn concentration is important for inhalation dosimetry in occupational and residential areas. The shorter half-life of radioactive 220Rn gas greatly affects its patterns resulting in non-homogeneity in the spatial concentration profile. In addition, the distribution profile also changes with variations in the ambient atmospheric parameters (ventilation rate, humidity etc.). The Computational fluid dynamics (CFD) technique has gained a lot of attention in recent times for the prediction and visualization of the distribution pattern of indoor 222Rn/220Rn concentration. This study aims to apply the CFD technique for studying the effect of variations in the ventilation rate on the distribution pattern of the 220Rn concentration in a thoron test house. Experimentally measured 220Rn flux from the surfaces of the experimental test house is used as input for the CFD simulations. Ventilation rate is varied from 0.1 h−1 to 9.0 h−1 and the simulated results of velocity and 220Rn concentration profile for the entire test domain are interpreted. It is observed that the increase of ventilation rate leads to the flow induced turbulence enhancing the mixing of 220Rn in indoor air. Results of this study demonstrate the inter-play of radionuclide half-life and turbulent mixing induced transportation. Inferences are discussed in order to improve the dosimetric deductions for indoor conditions. • CFD simulation of 220Rn distribution in a test house. • Effect of ventilation rate on 220Rn concentration profile studied. • Ventilation rate varied from 0.1 h−1 to 9.0 h−1. • Increase in ventilation rate induced turbulence enhancing mixing. • Homogeneity of 220Rn concentration increases with ventilation rate. [ABSTRACT FROM AUTHOR]

Recently, we reported a model independent and l-dependent four parameter formula which accounts very well for the half-lives of experimentally known one-proton emitters and also compares well with other model predictions. Later, the structure of the formula has been retained and fitted with two-proton half-lives predicted by the effective liquid drop model. With the new parameter set, the same form of the formula compared well with available experimental data on half-lives of two proton emitters as well as the predictions of ELDM. The formula has been applied to predict possible proton emitters in super heavy region. In this work, the application of these formulae is studied to predict the half-lives of one and two-proton emitters in the medium and heavy mass region ranging from 84 ≤ Z ≤ 100 and 37 ≤ Z ≤ 100, respectively. [ABSTRACT FROM AUTHOR]

Purpose: Synaptic abnormalities have been implicated in a variety of neuropsychiatric disorders, including epilepsy, Alzheimer's disease, and schizophrenia. Hence, PET imaging of the synaptic vesicle glycoprotein 2A (SV2A) may be a valuable in vivo biomarker for neurologic and psychiatric diseases. We previously developed [11C]UCB-J, a PET radiotracer with high affinity and selectivity toward SV2A; however, the short radioactive half-life (20 min for 11C) places some limitations on its broader application. Herein, we report the first synthesis of the longer-lived 18F-labeled counterpart (half-life: 110 min), [18F]UCB-J, and its evaluation in nonhuman primates. Methods: [18F]UCB-J was synthesized from the iodonium precursors. PET imaging experiments with [18F]UCB-J were conducted in rhesus monkeys to assess the pharmacokinetic and in vivo binding properties. Arterial samples were taken for analysis of radioactive metabolites and generation of input functions. Regional time–activity curves were analyzed using the one-tissue compartment model to derive regional distribution volumes and binding potentials for comparison with [11C]UCB-J. Results: [18F]UCB-J was prepared in high radiochemical and enantiomeric purity, but low radiochemical yield. Evaluation in nonhuman primates indicated that the radiotracer displayed pharmacokinetic and imaging characteristics similar to those of [11C]UCB-J, with moderate metabolism rate, high brain uptake, fast and reversible binding kinetics, and high specific binding signals. Conclusion: We have accomplished the first synthesis of the novel SV2A radiotracer [18F]UCB-J. [18F]UCB-J is demonstrated to be an excellent imaging agent and may prove to be useful for imaging and quantification of SV2A expression, and synaptic density, in humans. [ABSTRACT FROM AUTHOR]

We present a detailed discussion on neutrinoless double beta decay (0 ν β β) within left–right symmetric models based on the gauge symmetry of type S U (2) L × S U (2) R × U (1) B − L as well as S U (3) L × S U (3) R × U (1) X where fermion masses including that of neutrinos are generated through a universal seesaw mechanism. We find that one or more of the right-handed neutrinos could be as light as a few keV if left–right symmetry breaking occurs in the range of a few TeV to 100 TeV. With such light right-handed neutrinos, we perform a detailed study of new physics contributions to 0 ν β β and constrain the model parameters from the latest experimental bound on such a rare decay process. We find that the new physics contribution to 0 ν β β in such a scenario, particularly the heavy–light neutrino mixing diagrams, can individually saturate the existing experimental bounds, but their contributions to total 0 ν β β half-life cancel each other due to unitarity of the total 6 × 6 mass matrix. The effective contribution to half-life therefore, arises from the purely left and purely right neutrino and gauge boson mediated diagrams. We find that the parameter space saturating the 0 ν β β bounds remains allowed from the latest experimental bounds on charged lepton flavor violating decays like μ → e γ. We finally include the bounds from cosmology and supernova to constrain the parameter space of the model. [ABSTRACT FROM AUTHOR]

The sorption of phosphate on soils is studied by radioisotopic tracer method. Two consecutive processes with rather different rates were differentiated: namely the heterogeneous isotope exchange between the phosphate in the soil solution and the weakly sorbed phosphate (fast reaction), and the transformation of weakly sorbed phosphate to tightly sorbed phosphate (slow reaction). In this paper, it is shown how the rate constants of these two processes can be determined by a radiotracer with a relatively short half-life. [ABSTRACT FROM AUTHOR]

Abstract To understand the long-term behavior of radiocesium in the biological processes of a forest ecosystem, its concentration in Japanese epigeic earthworms (Megascolecidae), litter, and soil, and the ambient dose equivalent rates, were investigated after the Fukushima Dai-ichi Nuclear Power Plant accident. The metabolism of radiocesium in the earthworms was also investigated in the laboratory, and its biological half-life (T b) was estimated. The concentration of 137Cs in the habitat soil and litter changed from 2014 to 2016, with levels in the litter going from 44.9 Bq/g dw (in 2014) to 45.3 Bq/g dw (2015) and 10.7 Bq/g dw (2016); in soil, these values were 9.79 Bq/g dw, 7.14 Bq/g dw and 18.0 Bq/g dw, respectively. By contrast, no significant changes were observed in the concentrations in the earthworms, which were 4.87 Bq/g fw, 5.30 Bq/g fw and 4.67 Bq/g fw in 2014, 2015, and 2016, respectively. The ambient dose equivalent rates at the sampling site declined significantly over these three years, going from 2.15 μSv/h to 1.68 μSv/h and 1.35 μSv/h, mostly corresponding to physical decay of radiocesium. The majority (95%) of the 137Cs in the earthworms, observed via autoradiography, was concentrated primarily in the intestine. The clearance of 137Cs from the earthworms was described by dual exponential functions: the half-life in the rapid loss due to gut clearance was 0.10 days and a second slower loss due to physiological clearance was 27.4 days. Highlights • The concentrations and biokinetics of radiocesium in earthworms were investigated. • No significant changes in radiocesium concentration were observed from 2014 to 2016. • The distribution of radiocesium in the earthworms was visualized via autoradiography. • About 95% of the radiocesium was located in the intestines. • The biological half-life of 137Cs was estimated for initial and delayed clearance. [ABSTRACT FROM AUTHOR]

Abstract As a part of establishing a regional database on natural radioactivity, the atmospheric concentrations of 210Pb and 7Be were measured over a three and half year period (2014–2017) in Mangalore and Kaiga in the South West Coast of India. A total of 99 air samples, collected in the different months of the year, were analysed in this study. The mean activity concentrations of 7Be and 210Pb were found to be 5.5 ± 3.1 mBq m−3 and 1.1 ± 0.73 mBq m−3, respectively. Both the radionuclides exhibited strong seasonal variations, with maximum concentration of 7Be occurring in the summer and that of 210Pb in the winter season. The concentration of both the radionuclides was minimum in the rainy season. Higher 210Pb concentration during winter was attributed to the ingression of continental air masses due to the wind regime from the North East. The sunspot number index of the solar activity also plays an important role in the increase and decrease of 7Be concentration in the air. A clear trend of increased and lowered concentration of 7Be with lower and higher solar activity (low and high sunspot number), respectively, in accordance with the 11-year solar cycle, was observed in this study. The temporal variation of PM 10 concentration was also studied and it showed maximum value in the winter and minimum in the rainy season with an average of 56.9 μg m−3. Statistically significant positive correlation was observed between the PM 10 and 210Pb activity concentration, whereas a weak correlation was observed between PM 10 and 7Be. This is due to the fact that 7Be is largely associated with sub-micrometer size particles, whereas PM 10 is contributed by larger sizes. The dependence of the activity concentrations of 7Be and 210Pb with meteorological parameters such as rainfall, temperature, and humidity was studied through linear regression analysis. A significant correlation was observed between 7Be and 210Pb concentrations with rainfall intensity (with identical correlation coefficients), which suggested that the removal mechanisms of these two radionuclides were similar. 7Be showed a strong correlation with temperature, whereas 210Pb with humidity. A comparison of the data obtained in the present study for the South West Coast of India with the global literature values of 7Be and 210Pb in aerosols showed that the values did not reflect the well-known latitudinal dependence of the 7Be tropospheric fluxes. Overall, the study provides an improved understanding of the correlation and variability of 210Pb and 7Be concentrations in the atmosphere in the South West Coast of India. Highlights • Regional database on activity of atmospheric 7Be and 210Pb in Southwest Coast of India was established. • Rainfall is the major removal pathway for the 7Be and 210Pb from the atmosphere. • Dependence of solar activity with cosmogenic 7Be was studied. • A clear dependence of 7Be activity on solar activities was observed. • Causal factors for the temporal variability of 7Be and 210Pb concentrations were identified. [ABSTRACT FROM AUTHOR]

Technetium-99 is a high yield (~6% fission yield) fission product and long-lived (2.13×105 year half-life) component of nuclear waste that will be disposed of in a geological repository. Some 99Tc has been released into the environment due to nuclear fuel and weapon production activities at sites such as Hanford, WA. Strongly complexing ligands such as ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) are known to increase Tc(IV) solubility and mobility in environmental systems and an accurate quantification of the complexation of Tc(IV) with EDTA is important for predicting its behavior in a geological repository. A liquid–liquid extraction system utilizing 0.2 M TOPO in dodecane was used to measure the stability constants of Tc(IV)-EDTA in 0.50 m NaNO3 at variable temperatures (14.0±0.1, 25.0±0.1, and 32.0±0.1°C). The acid dependence of the apparent stability constants in the pCH range of 2.00–2.70 indicated the formation of TcO(EDTA)2− (logβ101=17.9±0.3, 25.0±0.1°C) and a protonated complex TcO(H)(EDTA)− (logβ111=20.5±0.1, 25.0±0.1°C). The associated thermodynamic parameters ΔrG101=−101.7±0.4 kJ·mol−1, ΔrH101=−47±9 kJ·mol−1, ΔrS101=179±36 J·mol−1·K−1, ΔrG111=−117.2±0.3 kJ·mol−1, ΔrH111=−23±5 kJ·mol−1, and ΔrS111=315±63 J·mol−1·K−1 (0.50 m NaNO3, 25.0±0.1°C) were determined by van't Hoff analysis. The formation of each Tc(IV)–EDTA complex is exothermic and present favorable entropy terms. [ABSTRACT FROM AUTHOR]

The radionuclide 129 I is a long-lived fission product that decays to 129 Xe by beta-particle emission. It is an important tracer in geological and biological processes and is considered one of the most important radionuclides to be assessed in studies of global circulation. It is also one of the major contributors to radiation dose from nuclear waste in a deep geological repository. Its half-life has been obtained by a combination of activity and mass concentration measurements in the frame of a cooperation of 6 European metrology institutes. The value obtained for the half-life of 129 I is 16.14 (12) × 10 6 a, in good agreement with recommended data but with a significant improvement in the uncertainty. [ABSTRACT FROM AUTHOR]

The half-life of 99 m Tc was measured at the JRC using the ionisation chamber 'IC1' (type Centronic IG12). The result, T 1/2 ( 99 m Tc) = 6.00660 (18) h, is in good agreement with literature data. One experiment was performed in IC1's default set-up with the ionisation current being integrated over an air capacitor and read out as a voltage increase over time. This ensured excellent linearity and precision throughout the dynamic range, but the maximum current was limited to 2 nA. In a second test, the current was directly read out with a Keithley 6517 A electrometer. Applying correction factors for the automatic range switching of the electrometer, an acceptable linearity was demonstrated over a range of 12 half-life periods starting at 20 nA. Range switching and autocorrelation of the current readout increase the systematic and random error propagation factors. Piecewise fitting of the decay curve over periods of 6 h yields the same 99 m Tc half-life value within 0.04% (0.0025 h) standard deviation over an activity range spanning at least 10 half-life periods (3 orders of magnitude). [ABSTRACT FROM AUTHOR]

The 238U decay constant (λU-238) is fundamental to radioisotope-based chronometry in the Earth and planetary sciences, yet only a single published λU-238 value (Jaffey et al. in Phys Rev C 4(5):1889-1906, 1971) is widely applied. We have determined λU-238 via the novel approach of measuring of 234Th ingrowth in high-purity 238U solutions, using isotope dilution mass spectrometry (ID-MS). The 234Th decay constant (λTh-234) was measured via decay counting with high-purity Ge (HPGe) γ detectors. Preliminary results for λU-238 agree with the value determined by α-counting [1] within the elevated uncertainty of 0.462% (k = 2). Ongoing efforts to reproduce λU-238 with reduced experimental uncertainties will inform future conclusions. [ABSTRACT FROM AUTHOR]

A new determination of the 229Th half-life was made based on measurements of the 229Th massic activity of a high-purity solution for which the 229Th molality had previously been measured. The 229Th massic activity was measured by direct comparison with SRM 4328C using 4παβ liquid scintillation counting, NaI counting, and standard addition liquid scintillation counting. The massic activity was confirmed by isotope dilution alpha spectrometry measurements. The calculated 229Th half-life is (7825 ± 87) years (k = 2), which is shorter than the three most recent half-life determinations but is consistent with these values within uncertainties. [ABSTRACT FROM AUTHOR]

The article discusses the concept of half-life and a model of knowledge decay in the health care industry, in light of technological advances. A mathematical equation--developed from a descriptive model--can provide an analogy for physical science's half-life and the concept of knowledge decay in managerial and professional expertise. The concept can be used to calculate the obsolescence of practicing physicians or other professionals and is relevant in evaluating the effectiveness of training and continuing-education programs.

Systematic study of superheavy nuclei 296Og and its possibilities to emit alpha particle and heavier clusters are studied using Modified Generalized Liquid Drop Model (MGLDM) with Q value dependent preformation factor. Half-lives and branching ratio of all possible cluster emission of 296Og is checked and only those cluster which are within the experimental half-lives limit (less than 1030s) and branching ratio limit (down to 10-19) are considered. Among this, 88Kr is found to be the most probable heavy cluster, leading to doubly magic 208Pb daughter nuclei, with half-lives comparable with alpha decay half-lives. Thus the role of doubly magic daughter nuclei in cluster decay is highlighted here. Again the decay modes of 296Og are also studied by comparing alpha decay half-lives using MGLDM with spontaneous fission half-lives proposed by Bao et al., and from this, it is found that for superheavy element 296Og, decays by 3 alpha chains followed by spontaneous fission. We hope that this study would help when this emission is experimentally detected in near future. [ABSTRACT FROM AUTHOR]

We have studied the α -decay properties of superheavy nuclei Z = 118 in the range 275 ≤ A ≤ 325 . Most of the predicted, unknown nuclei in the range 291 ≤ A ≤ 301 were found to have α -decay chains. Of these the nuclei 293−301 118 were found to have long half-lives and hence could be sufficient to detect them if synthesized in a laboratory. Fusion barries for different projectile-target combinations to synthesis superheavy nuclei Z = 118 are studied and are also represented in simple relations. We have also studied the evaporation residue cross section, compound nucleus formation probability (P CN ) and survival probability ( P Surv ) of different projectile-target combinations to synthesis superheavy element Z = 118 . The selected most probable projectile-target combinations are Ca+Cf, Ti+Cm, Sc+Bk, V+Am, Cr+Pu, Fe+U, Mn+Np, Ni+Th and Kr+Pb. We have formulated simple relations for maximum evaporation residue cross sections and its corresponding energies. This helps to identify the projectile-target combinations quickly. Hence, we have identified the most probable projectile-target combinations to synthesis these superheavy nuclei. We hope that our predictions may be a guide for the future experiments in the synthesis of more isotopes of superheavy nuclei Z = 118 . [ABSTRACT FROM AUTHOR]

The α -decay half-lives for the even–even, even–odd, odd–even and odd–odd of 356 nuclei in the range 52 ≤ Z p ≤ 118 have been studied within the analytical formula of Royer and also within the modified analytical formula of Royer. We calculated the new coefficient of the Royer by fitting 356 isotopes. Also, we considered the Denisov and Khudenko formula and obtained the new coefficient for the modified Denisov and Khudenko formula. We calculated the standard deviation and the average deviation. Analytical results are compared with the experimental data. The results are in better agreement with the experimental data when the effect of the isospin considered for the parent nuclei. [ABSTRACT FROM AUTHOR]