Half-lives Of Isotopes Research Articles

Experiences of Population Monitoring Using Whole-Body Counters in Response to the Fukushima Nuclear Accident.

Whole-body counter measurements of residents of Fukushima Prefecture have been extensively performed after the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. These measurements have demonstrated that the levels of internal contamination with radioactive cesium (Cs and Cs) in the residents are very low. This article provides an overview of and lessons learned from these whole-body counter measurements with emphasis on the technical problems encountered, and it discusses the effective use of whole-body counters for assessing the internal thyroid doses of individuals when direct measurements of I in the thyroid are difficult or impossible to implement for the total affected population in a short time after a nuclear reactor accident. The application of this dose reconstruction method requires determining the intake ratio of I to cesium isotopes at appropriate times and considers the short biological half-lives of cesium isotopes, in particular for children.

Comparative study of the alpha decay of Hg isotopes using different forms of nuclear potentials

The alpha decay half-lives of Hg isotopes within the range A = 171 – 212 have been studied using 25 different versions of nuclear potentials to select the suitable form of nuclear potential for alpha decay studies. The computed standard deviations suggested that the apt potential is BW 91 with a deviation 0.133. The next low deviation is shown by Proximity 1966, Proximity 1984, and Proximity 2003-I, II with deviations less than 0.2. Concerning other potentials, the fact we observed is that almost all the potentials possess a standard deviation less than one. The universal curve studied for alpha decay is observed to show straight line behavior irrespective of the nuclear potential used. Since the predicted alpha half-lives match well the experimental values, the half-lives of certain new Hg alpha emitters have been predicted by the present method. La période radioactive alpha des isotopes du mercure de nombre de masse A compris entre 171 et 212 a été évaluée à partir de 25 modèles différents de potentiel nucléaire adapté à la radioactivité alpha. Le calcul des écarts types suggère que le potentiel pertinent est BW 91, avec un écart de 0,133. La deuxième place revient à Proximity 1966, suivi de Proximity 1984 et de Proximity 2003-I, II, avec des écarts types inférieurs à 0,2. Les autres potentiels ont presque tous un écart type inférieur à 1. La courbe universelle caractéristique du rayonnement alpha est une droite, quel que soit le potentiel utilisé. Comme les périodes calculées sont en bon accord avec les valeurs expérimentales, on a calculé aussi, par la même méthode, les périodes de quelques émetteurs alpha nouveaux.

Unearthing radial independence for prediction of alpha-decay half-lives

Nuclear radial distance is a prerequisite for generating any alpha-decay half-life formula by taking a suitable effective potential. We study the emission process of alpha particles from an isolated quasi-bound state generated by an effective potential to a scattering state. The effective potential is expressed in terms of Frahn form of potential which is exactly solvable and an analytical expression for half-life is obtained in terms of Coulomb function, wave function and the potential. We then derive a closed-form expression for the decay half-life in terms of the parameters of the potential, Q-value of the system, mass and proton numbers of the nuclei valid for alpha-decay as well as proton-decay. From the nature of variations of half-life as a function of radial distance, we trace the radial independence region where decay time is almost constant. Finally, by overviewing our results and picking that particular radial distance, we predict the half-lives of a series of nuclei by using the closed-form expression. We also predict the half-lives of isotopes of nuclei with [Formula: see text] and 120.

Nuclear structure and decay modes of Ra isotopes within an axially deformed relativistic mean field model**Supported by Project No. SR/FTP/PS-106/2013, SERB, DST, Govt. of India

We examine the structural properties and half-life decay of Ra isotopes within the axially deformed Relativistic Mean-Field (RMF) theory with NL3 force parameters. We work out the binding energy (BE), RMS radii, two-neutron separation energies (S2n), and some other observables. The results are in good agreement with the finite-range droplet model (FRDM) and experimental results. Considering the possibility of neutron magic number, the α-decay and cluster decay half-lives of Ra isotopes are calculated systematically using the Q-values obtained from the RMF formalism. These decay half-life calculations are carried out by taking three different empirical formulae. The calculated decay half-lives are found to be highly sensitive to the choice of Q-values. Possible shell or sub-shell closures are found at daughter nuclei with N = 128 and N = 126 when alpha and 8Be, 12C, 18O respectively are emitted from Ra isotopes. Though the cluster radioactivity is affected by the shell closure of parent and daughter, a long half-life indicates the stability of the parent, and a small parent half-life indicates that the shell stability of the daughter against decay.

Toward an accurate determination of half-life of 147Sm isotope

The task of an accurate determination of alpha-decay rate of 147Sm isotope, a topic of importance in both basic and applied science, has been performed in the present research following two different routes. First, a critical review and data analysis of the whole set of half-life values obtained till date yielded an average of 106.3 ± 0.5 Ga. Second, a one-parameter, semi-empirical model for alpha emission from nuclei, developed in the framework of quantum mechanical tunneling mechanism through a Coulomb-plus-centrifugal-plus-overlapping potential barrier, that yielded a value of 108.2 ± 3.0 Ga. The good agreement found between the half-life values obtained from these procedures represents a net progress toward the assessment of a reliable 147Sm alpha-decay rate to be used in geo- and cosmo-chronological investigations.

Theoretical predictions for α -decay chains of Og118290−298 isotopes using a finite-range nucleon-nucleon interaction

The $\ensuremath{\alpha}$-decay half-lives of the recently synthesized superheavy nuclei (SHN) are investigated by employing the density dependent cluster model. A realistic nucleon-nucleon ($\mathit{NN}$) interaction with a finite-range exchange part is used to calculate the microscopic $\ensuremath{\alpha}$-nucleus potential in the well-established double-folding model. The calculated potential is then implemented to find both the assault frequency and the penetration probability of the $\ensuremath{\alpha}$ particle by means of the Wentzel-Kramers-Brillouin (WKB) approximation in combination with the Bohr-Sommerfeld quantization condition. The calculated values of $\ensuremath{\alpha}$-decay half-lives of the recently synthesized Og isotopes and its decay products are in good agreement with the experimental data. Moreover, the calculated values of $\ensuremath{\alpha}$-decay half-lives have been compared with those values evaluated using other theoretical models, and it was found that our theoretical values match well with their counterparts. The competition between $\ensuremath{\alpha}$ decay and spontaneous fission is investigated and predictions for possible decay modes for the unknown nuclei $_{\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\phantom{\rule{1em}{0ex}}118}^{290\ensuremath{-}298}\mathrm{Og}$ are presented. We studied the behavior of the $\ensuremath{\alpha}$-decay half-lives of Og isotopes and their decay products as a function of the mass number of the parent nuclei. We found that the behavior of the curves is governed by proton and neutron magic numbers found from previous studies. The proton numbers $Z=114$, 116, 108, 106 and the neutron numbers $N=172$, 164, 162, 158 show some magic character. We hope that the theoretical prediction of $\ensuremath{\alpha}$-decay chains provides a new perspective to experimentalists.

TREATMENT OF HALF-LIFE VALUES OF SOME LEAD ISOTOPES FOR THE EMISSION OF ALPHA-PARTICLES IN 178≤A≤194

To develop equations to calculate the half-life of lead isotopes theoretically and compare them with practical results by assuming a simple mathematical model based on the probability of forming alpha particles inside the parent nucleus before tunneling decay them. It is assumed that the presence of an alpha particle inside the nucleus has a Coulomb effect dependent on the reduced mass of the alpha particle with the core, reducing the rest of the effects on the effective potential. The effective radius depends on the mass number of the core and the cluster. The model assumes that there is a number of collisions before tunneling decay, taking into account the existence of the potential barrier penetration coefficient, which expresses the potential permeability of the potential barrier to the alpha particles within it. The model assumes that the Gamow coefficient is dependent on the atomic numbers of both core and cluster, the reduced mass, and the effect of the energy of the alpha particles and takes into account the value of the Coulomb effect.

PET radiometals for antibody labeling.

Recent advances in molecular characterization of tumors have made possible the emergence of new types of cancer therapies where traditional cytotoxic drugs and nonspecific chemotherapy can be complemented with targeted molecular therapies. One of the main revolutionary treatments is the use of monoclonal antibodies (mAbs) that selectively target the disseminated tumor cells while sparing normal tissues. mAbs and related therapeutics can be efficiently radiolabeled with a wide range of radionuclides to facilitate preclinical and clinical studies. Non-invasive molecular imaging techniques, such as Positron Emission Tomography (PET), using radiolabeled mAbs provide useful information on the whole-body distribution of the biomolecules, which may enable patient stratification, diagnosis, selection of targeted therapies, evaluation of treatment response, and prediction of dose limiting tissue and adverse effects. In addition, when mAbs are labeled with therapeutic radionuclides, the combination of immunological and radiobiological cytotoxicity may result in enhanced treatment efficacy. The pharmacokinetic profile of antibodies demands the use of long half-life isotopes for longitudinal scrutiny of mAb biodistribution and precludes the use of well-stablished short half-life isotopes. Herein, we review the most promising PET radiometals with chemical and physical characteristics that make the appealing for mAb labeling, highlighting those with theranostic radioisotopes.

High power density nuclear battery prototype based on diamond Schottky diodes

We report here for the first time a fabrication of betavoltaic battery prototype consisting of 200 single conversion cells based on Schottky barrier diamond diodes which have been vertically stacked with ~24% 63Ni radioactive isotope. The maximum electrical output power of about 0.93 μW was obtained in total volume of 5 × 5 × 3.5 mm3. We used the ion-beam assisted lift-off technique to obtain conversion cells of minimal thickness comparable with the characteristic penetration length of beta-particles emitted by 63Ni isotope. The obtained value of 15 μm was limited by the mechanical strength of produced structures and process reliability. To check the performance of thin diamond based conversion cells we carried out IV-curves measurements at electron beam irradiation in SEM. We found that the sacrificial layer for the splitting of such thin conversion cell from HPHT diamond substrate did not cause a considerable degradation of device charge collection efficiency. As a result, the fabricated prototype provided the output power density of about 10 μW/cm3, that is the best known value for nuclear batteries based on 63Ni radioisotope. Moreover, the long half-life of 63Ni isotope gives the battery specific energy of about 3300 mWh/g that is an order of magnitude higher than the typical value of commercial chemical cells.

Interplay of quasiparticle-vibration coupling and pairing correlations on β-decay half-lives

The nuclear β-decay half-lives of Ni and Sn isotopes, around the closed shell nuclei 78Ni and 132Sn, are investigated by computing the distribution of the Gamow–Teller strength using the Quasiparticle Random Phase Approximation (QRPA) with quasiparticle-vibration coupling (QPVC), based on ground-state properties obtained by Hartree–Fock–Bogoliubov (HFB) calculations. We employ the effective interaction SkM⁎ and a zero-range effective pairing force. The half-lives are strongly reduced by including the QPVC. We study in detail the effects of isovector (IV) and isoscalar (IS) pairing. Increasing the IV strength tends to increase the lifetime for nuclei in the proximity of, but lighter than, the closed-shell ones in QRPA calculations, while the effect is significantly reduced by taking into account the QPVC. On the contrary, the IS pairing mainly plays a role for nuclei after the shell closure. Increasing its strength decreases the half-lives, and the effect at QRPA and QRPA+QPVC level is comparable. The effect of IS pairing is particularly pronounced in the case of the Sn isotopes, where it turns out to be instrumental to obtain good agreement with experimental data.

Theoretical studies on the $$\alpha $$ α decay half-lives of hyper and normal isotopes of Po

The $$\alpha $$ decay half-lives of hyper and normal isotopes of Po nuclei are studied in the present work. The inclusion of $$\Lambda $$ –N interaction changes the half-life for $$\alpha $$ decay. The theoretical predictions on the $$\alpha $$ decay half-lives of normal Po isotopes are compared with experimental results and are seen to be matching well with each other. The neutron shell closure at $$N = 126$$ is found to be the same for both normal and hypernuclei. The Geiger–Nuttal (G–N) law for $$\alpha $$ decay is unaltered in the case of hypernuclei. The hypernuclei will decay into normal nuclei by mesonic or non-mesonic decay modes. Since the half-lives of normal Po nuclei are well within the experimental limits, our theoretical results suggest experimental verification of the $$\alpha $$ emission from hyper Po nuclei in a cascade process.

Influence of proton-skin thickness on the decays of heavy nuclei

We investigate the effect of proton-skin thickness on the α decay process. We consider 188 neutron-deficient nuclei belonging to the isotopic chains from Te (Z = 52) to Pb (Z = 82). The calculations of the half-life are carried out in the framework of the preformed cluster model, with the Wentzel-Kramers-Brillouin penetration probability and assault frequency. It is shown that the proton-skin thickness ( of the daughter nucleus gives rise to a total α- daughter nucleus interaction potential of relatively wide deep internal pocket and a thinner Coulomb barrier of less height. This increases the penetration probability but decreases the assault frequency. The overall impact of the proton-skin thickness appears as a decrease in the decay half-life. The proton-skin thickness decreases the stability of the nucleus. The half-lives of the proton-skinned isotopes along the isotopic chain decrease exponentially with increasing the proton-skin thickness, whereas the -value increases with . α-decay manifests itself as the second favorite decay mode of neutron-deficient nuclei, next to the -decay and before proton-decay. It is indicated as main, competing, and minor decay mode, at 21%, 7%, and 57%, respectively, of the investigated nuclei.

Porphyrins as ligands for 64copper: background and trends.

Porphyrins and 64Cu have emerged as a novel synergic option for applications in PET molecular imaging. Both the characteristics and photophysical properties of macrocyclic porphyrins and the relatively long half-life of the copper isotope, in addition to the increased tumor-specific uptake of porphyrins compared to normal cells, make this complex an attractive option not only for diagnosis but also for therapeutic applications. Herein, we present an overview of the latest results on the development of PET agents based on porphyrins and 64Cu, including methods used to improve the selectivity of these macrocycles when conjugated with biological units such as monoclonal antibodies, peptides or proteins.

Alpha-decay half-lives for isotopes of even-even nuclei: A temperature-dependent approach with Woods-Saxon potential

The alpha-decay process is investigated in the presence of the nuclear temperature. Using an analytical approach for the calculation of effective sharp radius and a new barrier potential, the half-lives for the even-even nuclei of Po, Pb, Ra, Rb, Rn, Th and U are derived and compared with the experimental data.

Alpha decay studies on Po isotopes using different versions of nuclear potentials

The alpha decays from 186-224Po isotopes have been studied using 25 different versions of nuclear potentials so as to select a suitable nuclear potential for alpha decay studies. The computed standard deviation of the calculated half-lives in comparison with the experimental data suggested that proximity 2003-I is the apt form of nuclear potential for alpha decay studies as it possesses the least standard deviation, $ \sigma =0.620$ . Among the different proximity potentials, proximity 1966 ( $ \sigma =0.630$ and proximity 1977 ( $ \sigma =0.636$ , are also found to work well in alpha decay studies with low deviation. Among other versions of nuclear potentials (other than proximity potentials), Bass 1980 is suggested to be a significant form of nuclear potential because of its good predictive power. However, while the other forms of potentials are able to reproduce the experimental data to some extent, these potentials cannot be considered as apposite potentials for alpha decay studies in their present form. Since the experimental correlation of the models is noticed to be satisfying, the alpha decay half-lives of certain Po isotopes that are not detected experimentally yet have been predicted.

Tissue-specific turnover rates of the nitrogen stable isotope as functions of time and growth in a cyprinid fish

Ecological applications of stable isotope data require knowledge on the isotopic turnover rate of tissues, usually described as the isotopic half-life in days (T0.5) or the change in mass (G0.5). Ecological studies increasingly analyse tissues collected non-destructively, such as fish fin and scales, but there is limited knowledge on their turnover rates. Determining turnover rates in situ is challenging, with ex situ approaches preferred. Correspondingly, T0.5 and G0.5 of the nitrogen stable isotope (δ15N) were determined for juvenile barbel Barbus barbus (5.5 ± 0.6 g starting weight) using a diet-switch experiment. δ15N data from muscle, fin and scales were taken during a 125 day post diet-switch period. Whilst isotopic equilibrium was not reached in the 125 days, the δ15N values did approach those of the new diet. The fastest turnover rates were in more metabolically active tissues, from muscle (highest) to scales (lowest). Turnover rates were relatively slow; T0.5 was 84 (muscle) to 145 (scale) days; G0.5 was 1.39 × body mass (muscle) to 2.0 × body mass (scales), with this potentially relating to the slow growth of the experimental fish. These turnover estimates across the different tissues emphasise the importance of estimating half-lives for focal taxa at species and tissue levels for ecological studies.

Consensus building for interlaboratory studies, key comparisons, and meta-analysis

Interlaboratory studies in measurement science, including key comparisons, and meta-analyses in several fields, including medicine, serve to intercompare measurement results obtained independently, and typically produce a consensus value for the common measurand that blends the values measured by the participants.Since interlaboratory studies and meta-analyses reveal and quantify differences between measured values, regardless of the underlying causes for such differences, they also provide so-called ‘top–down’ evaluations of measurement uncertainty.Measured values are often substantially over-dispersed by comparison with their individual, stated uncertainties, thus suggesting the existence of yet unrecognized sources of uncertainty (dark uncertainty). We contrast two different approaches to take dark uncertainty into account both in the computation of consensus values and in the evaluation of the associated uncertainty, which have traditionally been preferred by different scientific communities. One inflates the stated uncertainties by a multiplicative factor. The other adds laboratory-specific ‘effects’ to the value of the measurand.After distinguishing what we call recipe-based and model-based approaches to data reductions in interlaboratory studies, we state six guiding principles that should inform such reductions. These principles favor model-based approaches that expose and facilitate the critical assessment of validating assumptions, and give preeminence to substantive criteria to determine which measurement results to include, and which to exclude, as opposed to purely statistical considerations, and also how to weigh them.Following an overview of maximum likelihood methods, three general purpose procedures for data reduction are described in detail, including explanations of how the consensus value and degrees of equivalence are computed, and the associated uncertainty evaluated: the DerSimonian–Laird procedure; a hierarchical Bayesian procedure; and the Linear Pool. These three procedures have been implemented and made widely accessible in a Web-based application (NIST Consensus Builder).We illustrate principles, statistical models, and data reduction procedures in four examples: (i) the measurement of the Newtonian constant of gravitation; (ii) the measurement of the half-lives of radioactive isotopes of caesium and strontium; (iii) the comparison of two alternative treatments for carotid artery stenosis; and (iv) a key comparison where the measurand was the calibration factor of a radio-frequency power sensor.

Design of Radioiodinated Pharmaceuticals: Structural Features Affecting Metabolic Stability towards in Vivo Deiodination.

Radioiodinated pharmaceuticals are convenient tracers for clinical and research investigations because of the relatively long half‐lives of radioactive iodine isotopes (i.e., 123I, 124I, and 131I) and the ease of their chemical insertion. Their application in radionuclide imaging and therapy may, however, be hampered by poor in vivo stability of the C–I bond. After an overview of the use of iodine in biology and nuclear medicine, we present here a survey of the catabolic pathways for iodinated xenobiotics, including their biodistribution, accumulation, and biostability. We summarize successful rational improvements in the biostability and conclude with general guidelines for the design of stable radioiodinated pharmaceuticals. It appears to be necessary to consider the whole molecule, rather than the radioiodinated fragment alone. Iodine radionuclides are generally retained in vivo on sp2 carbon atoms in iodoarenes and iodovinyl moieties, but not in iodinated heterocycles or on sp3 carbon atoms. Iodoarene substituents also have an influence, with increased in vivo deiodination in the cases of iodophenols and iodoanilines, whereas methoxylation and difluorination improve biostability.

Production of Zr-89 using sputtered yttrium coin targets

An increasing interest in zirconium-89 (89Zr) can be attributed to the isotope's half-life which is compatible with antibody imaging using positron emission tomography (PET). The goal of this work was to develop an efficient means of production for 89Zr that provides this isotope with high radionuclidic purity and specific activity. We investigated the irradiation of yttrium sputtered niobium coins and compared the yields and separation efficiency to solid yttrium coins. The sputtered coins were irradiated with an incident beam energy of 17.5MeV or 17.8MeV providing a degraded transmitted energy through an aluminum degrader of 12.5MeV or 12.8MeV, respectively, with various currents to determine optimal cyclotron conditions for 89Zr production. Dissolution of the solid yttrium coin took 2h with 50mL of 2M HCl and dissolution of the sputtered coin took 15–30min with 4mL of 2M HCl. During the separation of 89Zr from the solid yttrium coins, 77.9 ± 11.2% of the activity was eluted off in an average of 7.3mL of 1M oxalic acid whereas for the sputtered coins, 91 ± 6% was eluted off in an average of 1.2mL of 1M oxalic acid with 100% radionuclidic purity. The effective specific activity determined via DFO-SCN titration from the sputtered coins was 108±7mCi/μmol as compared to 20.3mCi/μmol for the solid yttrium coin production. ICP-MS analysis of the yttrium coin and the sputtered coins showed 99.99% yttrium removed with 178μg of yttrium in the final solution and 99.93–100% of yttrium removed with remaining range of 0–42μg of yttrium in the final solution, respectively. The specific activity calculated for the solid coin and 3 different sputtered coins using the concentration of Zr found via ICP-MS was 140±2mCi/μmol, 300±30mCi/μmol, 410±60mCi/μmol and 1719±5mCi/μmol, respectively. Labeling yields of the 89Zr produced via sputtered targets for 89Zr- DFO-trastuzumab were >98%. Overall, these results show the irradiation of yttrium sputtered niobium coins is a highly effective means for the production of 89Zr.

The Effect of Parasite Infection on Stable Isotope Turnover Rates of δ15N, δ13C and δ34S in Multiple Tissues of Eurasian Perch Perca fluviatilis.

Stable isotope analysis of commercially and ecologically important fish can improve understanding of life-history and trophic ecology. However, accurate interpretation of stable isotope values requires knowledge of tissue-specific isotopic turnover that will help to describe differences in the isotopic composition of tissues and diet. We performed a diet-switch experiment using captive-reared parasite-free Eurasian perch (Perca fluviatilis) and wild caught specimens of the same species, infected with the pike tapeworm Triaenophorus nodulosus living in host liver tissue. We hypothesize that metabolic processes related to infection status play a major role in isotopic turnover and examined the influence of parasite infection on isotopic turn-over rate of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) in liver, blood and muscle. The δ15N and δ13C turnovers were fastest in liver tissues, followed by blood and muscle. In infected fish, liver and blood δ15N and δ13C turnover rates were similar. However, in infected fish, liver and blood δ13C turnover was faster than that of δ15N. Moreover, in infected subjects, liver δ15N and δ13C turnover rates were three to five times faster than in livers of uninfected subjects (isotopic half-life of ca.3-4 days compared to 16 and 10 days, respectively). Blood δ34S turnover rate were about twice faster in non-infected individuals implying that parasite infection could retard the turnover rate of δ34S and sulphur containing amino acids. Slower turnover rate of essential amino acid could probably decrease individual immune function. These indicate potential hidden costs of chronic and persistent infections that may have accumulated adverse effects and might eventually impair life-history fitness. For the first time, we were able to shift the isotope values of parasites encapsulated in the liver by changing the dietary source of the host. We also report variability in isotopic turnover rates between tissues, elements and between infected and parasite-free individuals. These results contribute to our understanding of data obtained from field and commercial hatcheries; and strongly improve the applicability of the stable isotope method in understanding life-history and trophic ecology of fish populations.