Decay Half-lives Research Articles

Effect of Age and Viscosity on Duration of Corneal Anesthesia with Topical 2% Lidocaine Administration.

Purpose: Formulation viscosity and patient-specific parameters such as age are important considerations in achieving patient comfort for prolonged anterior segment surgical procedures. In this study, we report pharmacodynamic and pharmacokinetic parameters of topical 2% lidocaine anesthetic decay based on formulation viscosity and subject age. Methods: Extemporaneous 2% lidocaine solution was compounded with varying percentages of carboxymethylcellulose (CMC) to adjust product viscosity. Juvenile and adult New Zealand White rabbits were utilized as a model for lidocaine-induced corneal anesthesia analysis. Following application of 20 μL in 1 eye of each animal, corneal sensitivity was measured using a Cochet-Bonnet esthesiometer at baseline and at 1-min intervals until recovery to baseline. Subsequent to washout period, the experiment was repeated for 3 replicate experiments. Results: A one-phase exponential decay model was utilized to describe rate of anesthesia decay. Bioavailability increased in a manner disproportionate to both tear film concentration and solution viscosity. In adult animals, half-life of anesthetic decay was found to range from 6.03 min with 2% lidocaine in 0.5% CMC to 9.45 min with 2% lidocaine in 1.5% CMC. In juveniles, half-life was found to be 4.46 and 3.58 min for 2% lidocaine in 1.5% CMC and commercial 2% lidocaine gel, respectively. Conclusions: Decay parameters of lidocaine-induced corneal anesthesia appear disparate from viscosity. It is postulated that viscosity-related increase in corneal contact time through reduced drainage plays a critical role in increasing bioavailability of topical anesthetics in our experimental findings, although nonlinear in character. Age is found to be an important mediator of lidocaine-induced corneal anesthesia.

Status of the NEXT experiment.

NEXT is an international experimental program aiming at the detection of 0\U0001d708ββ decay in 136Xe using a high-pressure gaseous xenon electroluminescent TPC. The technique allows for superb energy resolution, 1% FWHM at Q ββ , and topological discrimination based on the unique signature that a double electron produces in a gaseous medium. With ∼0.5 m in each dimension, NEXT-White (NEW) has been operating underground since 2016 at the Laboratorio Subterráneo de Canfranc (LSC), using xenon enriched to 90% 136Xe. Its purpose is to validate all aspects of the technology on a large scale and demonstrate its performance on 2\U0001d708ββ decay events. NEXT-100 will replace NEW and construction will start during 2021. It will deploy ∼97 kg of enriched xenon and demonstrate sensitivity to 0\U0001d708ββ decay half-lives on the scale of 1025 yr.

Artificial Thermal Quenching and Salt Crystallization Weathering Processes for the Assessment of Long-Term Degradation Characteristics of Some Sedimentary Rocks, Egypt

This research aims at investigating the deterioration of limestone rocks due to the influences of thermal quenching and salt crystallization weathering tests and predicting their long-term durability. Therefore, six types of limestones were quarried from different provinces of Egypt and subjected to 50 cycles of thermal quenching and 25 cycles of salt crystallization weathering processes. The porosity, Schmidt hammer rebound hardness, ultrasound pulse velocity, Brazilian tensile strength, and uniaxial compression strength were determined before and after weathering processes. In addition, the mathematical decay function model was developed to evaluate the degradation rate of samples against weathering processes. Results proved that the cyclic salt crystallization deteriorates the physico-mechanical characteristics of the studied limestone more strongly than the thermal quenching cycles do. The decay constant and half-life indexes obtained here indicate that the degradation rate differs for various limestone specimens under thermal and salt weathering processes. This model also showed that the deterioration rate of the studied rocks was higher during cyclic salt crystallization in comparison with thermal quenching. Therefore, the rock degradation rate and or long-term durability under cyclic thermal and salt processes can be estimated accurately. These results show that the studied limestones can be used as building stones in regions exposed to frequent cyclic thermal and salty weathering conditions for long periods without degradation. However, partial attention should be given to LSG limestone rocks characterized by increased porosity and water absorption characteristics.

Theoretical calculation of alpha decay half-lives of Neptunium nuclei using modified generalized liquid drop model

We considered the α-decay half-lives of neptunium (ZNp = 93) nuclei in the case of deformed nuclei in the range 219 ≤ A ≤ 239 using the generalized liquid-drop model (GLDM) with 1977 nuclear proximity potential suggested by Blocki et al. (1977) [29]. Also, we analyzed the α-decay half-lives of Np isotopes within the WKB method and the Deformed Proximity Potential Model (DPPM). We consider the quadrupole and hexadecapole deformations at θ=0, θ=30, θ=45, and θ=90 degrees. The calculated half-lives and the alpha decay branching ratios are compared with experimental data and are in good agreement. We compared the results obtained with the corresponding experimental data and with the models UNIV, UDL, SemFIS, the Coulomb and Proximity Potential Model (CPPM), SLB and Royer and it is found that they match well over a wide range. The calculated results are in reasonable agreement with the experimental data. Therefore, DPPM gives reliable and accurate results for favored α-decays in the neptunium mass region.

Alternative routes for 64Cu production using an 18 MeV medical cyclotron in view of theranostic applications

Radiometals play a fundamental role in the development of personalized nuclear medicine. In particular, copper radioisotopes are attracting increasing interest since they offer a varying range of decay modes and half-lives and can be used for imaging (60Cu, 61Cu, 62Cu and 64Cu) and targeted radionuclide therapy (64Cu and 67Cu), providing two of the most promising true theranostic pairs, namely 61Cu/67Cu and 64Cu/67Cu. Currently, the most widely used in clinical applications is 64Cu, which has a unique decay scheme featuring β+-, β−-decay and electron capture. These characteristics allow its exploitation in both diagnostic and therapeutic fields. However, although 64Cu has extensively been investigated in academic research and preclinical settings, it is still scarcely used in routine clinical practice due to its insufficient availability at an affordable price. In fact, the most commonly used production method involves proton irradiation of enriched 64Ni, which has a very low isotopic abundance and is therefore extremely expensive. In this paper, we report on the study of two alternative production routes, namely the 65Cu(p,pn)64Cu and 67Zn(p, α)64Cu reactions, which enable low and high 64Cu specific activities, respectively. To optimize the 64Cu production, while minimizing the mass of copper used as a target in the first case, or the co-production of other copper radioisotopes in the second case, an accurate knowledge of the production cross sections is of paramount importance. For this reason, the involved nuclear reaction cross sections were measured at the Bern medical cyclotron laboratory by irradiating enriched 65CuO and enriched 67ZnO targets. On the basis of the obtained results, the production yield and purity were calculated to assess the optimal irradiation conditions. Several production tests were performed to confirm these findings.

Systematic calculations of cluster radioactivity half-lives in trans-lead nuclei* *This work is supported in part by the National Natura Science Foundation of China (12175100 and 11975132), the Construct Program of the Key Discipline in Hunan Province, the Research Foundation of Education Bureau of Hunan Province (18A237), the Natural Science Foundation of Hunan Province (2018JJ3324), the Innovation Group of Nuclear and

In the present work, based on the Wentzel-Kramers-Brillouin (WKB) theory, considering the cluster preformation probability (), we systematically investigate the cluster radioactivity half-lives of 22 trans-lead nuclei ranging from 221Fr to 242Cm. When the mass number of the emitted cluster 28, is obtained by the exponential relationship of to the α decay preformation probability () proposed by R. Blendowskeis [Phys. Rev. Lett. 61, 1930 (1988)], while is calculated through the cluster-formation model (CFM). When 28, is calculated through the charge-number dependence of on the decay products proposed by Ren [Phys. Rev. C 70, 034304 (2004)]. The half-lives of cluster radioactivity have been calculated by the density-dependent cluster model [Phys. Rev. C 70, 034304 (2004)] and by the unified formula of half-lives for alpha decay and cluster radioactivity [Phys. Rev. C 78, 044310 (2008)]. For comparison, a universal decay law (UDL) proposed by Qi [Phys. Rev. C 80, 044326 (2009)], a semi-empirical model for both α decay and cluster radioactivity proposed by Santhosh [J. Phys. G: Nucl. Part. Phys. 35, 085102 (2008)], and a unified formula of half-lives for alpha decay and cluster radioactivity [Phys. Rev. C 78, 044310 (2008)] are also used. The calculated results of our work, Ni's formula , and the UDL can well reproduce the experimental data and are better than those of Santhosh's model. In addition, we extend this model to predict the half-lives for 51 nuclei, whose cluster radioactivity is energetically allowed or observed but not yet quantified in NUBASE2020.

Latest Results from the CUORE Experiment

The Cryogenic Underground Observatory for Rare Events (CUORE) is the first cryogenic experiment searching for 0nu beta beta decay that has been able to reach the one-tonne mass scale. The detector, located at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy, consists of an array of 988 {mathrm{TeO}}_{2} crystals arranged in a compact cylindrical structure of 19 towers. CUORE began its first physics data run in 2017 at a base temperature of about 10 mK and in April 2021 released its 3{mathrm{rd}} result of the search for 0nu beta beta , corresponding to a tonne-year of mathrm{TeO}_{2} exposure. This is the largest amount of data ever acquired with a solid state detector and the most sensitive measurement of 0nu beta beta decay in {}^{130}mathrm{Te} ever conducted . We present the current status of CUORE search for 0nu beta beta with the updated statistics of one tonne-yr. We finally give an update of the CUORE background model and the measurement of the {}^{130}mathrm{Te}2nu beta beta decay half-life and decay to excited states of {}^{130}mathrm{Xe}, studies performed using an exposure of 300.7 kg yr.

Properties and synthesis of the superheavy nucleus Fl114298

The one-nucleon separation energy ${S}_{n}$, two-nucleon separation energy ${S}_{2n}$, one-proton separation energy ${S}_{p}$, two-proton separation energy ${S}_{2p}, \ensuremath{\alpha}$-decay energy ${Q}_{\ensuremath{\alpha}}, \ensuremath{\alpha}$-decay half-life and spontaneous fission half-life of $Z=114$ isotopes and $N=184$ isotones are calculated by the finite-range droplet model (FRDM2012). It is found that $N=184$ is a neutron magic number, and $Z=114$ is a proton magic number. The properties of $Z=114$ isotopes and $N=184$ isotones provide a vital signal that $_{114}^{298}\mathrm{Fl}$ may be a spherical double-magic nucleus and also the center of the stability island of superheavy nuclei. Based on this, we began to investigate the optimal conditions for the synthesis of superheavy nucleus $_{114}^{298}\mathrm{Fl}$ within the dinuclear system model. To produce such neutron-rich compound nucleus, we consider using the extremely neutron-rich radioactive beams to bombard actinide targets. The evaporation residue cross section of superheavy nuclei synthesized by radioactive beam is analyzed in detail. Finally, we suggest that for the synthesis of $_{114}^{298}\mathrm{Fl}$, the radioactive beam-induced fusion reaction $^{64}\mathrm{Ti}+^{238}\mathrm{U}$ in the $4n$ evaporation channel with an excitation energy of 43 MeV is optimal.

A Physical Model of Tropical Cyclone Central Pressure Filling at Landfall

Abstract We derive a simple physically based analytic model that describes the pressure filling of a tropical cyclone (TC) over land. Starting from the axisymmetric mass continuity equation in cylindrical coordinates, we derive that the half-life of the decay of the pressure deficit between the environment and TC center is proportional to the initial radius of maximum surface wind speed. The initial pressure deficit and column-mean radial inflow speed into the core are the other key variables. The assumptions made in deriving the model are validated against idealized numerical simulations of TC decay over land. Decay half-lives predicted from a range of initial TC states are tested against the idealized simulations and are in good agreement. Dry idealized TC decay simulations show that without latent convective heating, the boundary layer decouples from the vortex above leading to a fast decay of surface winds while a midlevel vortex persists.

Double Beta Decay: A Shell Model Approach

Studies of weak interaction in nuclei are important tools for testing different aspects of the fundamental symmetries of the Standard Model. Neutrinoless double beta decay offers an unique venue of investigating the possibility that neutrinos are Majorana fermions and that the lepton number conservation law is violated. Here, I use a shell model approach to calculate the nuclear matrix elements needed to extract the lepton-number-violating parameters of a few nuclei of experimental interest from the latest experimental lower limits of neutrinoless double beta decay half-lives. The analysis presented here could reveal valuable information regarding the dominant neutrinoless double beta decay mechanism if experimental half-life data become available for different isotopes. A complementary shell model analysis of the two-neutrino double beta decay nuclear matrix elements and half-lives is also presented.

αdecay of Po and Rn isotopes using different choices of impinging frequency

A comprehensive study of $\ensuremath{\alpha}$ particle emergence from $^{188\text{--}218}\mathrm{Po}$ isotopes is carried out within the framework of the preformed cluster model (PCM). The mass asymmetry coordinate and the interfragment separation play crucial roles in the identification of the most probable decay channel and the barrier penetration of decay fragments. First, the barrier characteristics are studied using two choices of radii [with surface diffuseness (${C}_{i}$) and without surface diffuseness (${R}_{i}$)]. The fragmentation behavior of $^{188}\mathrm{Po}$, $^{202}\mathrm{Po}$, and $^{218}\mathrm{Po}$ isotopes is explored for the identification of the most probable decay channel in view of the structure of the fragmentation potential. The $\ensuremath{\alpha}$ decay is found to be the most prominent decay mode in the chosen set of isotopes. The preformation and penetrative probability of the decay fragments is studied with respect to increase in the neutron number of the parent nucleus. The $\ensuremath{\alpha}$ decay half-lives of polonium isotopes are calculated using classical assault frequency (${\ensuremath{\nu}}_{c}$) and quantum mechanical assault frequency (${\ensuremath{\nu}}_{q}$) and a comparison is made with the experimental data. Here, the term assault frequency is basically the impinging frequency of an $\ensuremath{\alpha}$ particle near the surface of the parent nucleus. Further, the $\ensuremath{\alpha}$ decay half-lives of the $^{198\text{--}220}\mathrm{Rn}$ isotopes are calculated using the effective assault frequency (${\ensuremath{\nu}}_{e}$) parameter, and a comparison is made with the available experimental data.

Calculation of two-proton radioactivity and application to Be9, Li6,7, He3,6, and H2,3 emissions

The $2p$ radioactivity half-lives have been calculated within a tunneling process through the potential barrier determined from the original version of the generalized liquid drop model and quasimolecular shapes. The sparse experimental data on the $2p$ radioactivity half-lives of the $^{12}\mathrm{O}$, $^{16}\mathrm{Ne}$, $^{19}\mathrm{Mg}$, $^{45}\mathrm{Fe}$, $^{48}\mathrm{Ni}$, $^{54}\mathrm{Zn}$, and $^{67}\mathrm{Kr}$ nuclei are roughly reproduced when taking into account the ${Q}_{2p}^{exp}$ value. An analytic formula is provided to obtain rapidly these different half-lives. Using the ${Q}_{2p}$ values extracted from the recent Nubase2020 table, extrapolations to other perhaps possible $2p$ emitters are proposed. Within the same approach, formulas to determine the $^{9}\mathrm{Be}$, $^{6,7}\mathrm{Li}$, $^{3,6}\mathrm{He}$, and $^{2,3}\mathrm{H}$ decay half-lives at low excitation energy are also provided.

Calculation of $$\alpha $$-decay half-lives for isotopes around $$N=Z$$ using different proximity-type potentials

Calculation of $$\alpha $$-decay half-lives for isotopes around $$N=Z$$ using different proximity-type potentials

Unified description of α decay and cluster radioactivity using the neural network approach and universal decay law

The α decay and cluster radioactivity half-life of nuclei are calculated uniformly. The universal decay law (UDL) (Qi et al 2009 Phys. Rev. Lett. 103 072501) is refitted to include minimum angular momentum effect and unpaired nucleon effect. The UDL formula and neural network approach to describe α decay and cluster radioactivity half-life calculations were improved. We used the UDL formulas and neural network approach to predict the cluster radioactivity half-life of actinide nuclei and α decay half-life of superheavy nuclei Z = 117–120. We hope to contribute to the discovery of new atomic nucleus cluster radioactivity phenomena and theoretical studies of α decay of superheavy nuclei.

Proton 3D tracking and emission time from a short-lived isomer with ACTAR TPC

An experiment was conducted at the GANIL/LISE3 facility to produce the 10+ isomer of 54Ni and measure its proton radioactivity decay branches. The proton detection was achieved with the ACTAR TPC device that enabled the separation of the small signal of the emitted proton from the large signal of the implanted ion, while the decay half-life is of the order of 150 ns. From the measured data, the emitted proton track length and the decay time of the ion can be extracted simultaneously. The full proton radioactivity pattern could be established, with two emission branches and their relative branching ratio. Data processing and analysis that allowed to identify and separate the ion and the proton signals in order to reconstruct the particles trajectories and decay time are detailed. The evaluation of the detection efficiency for the proton radioactivity branches based on a full simulation is described.

Roles of tensor and isoscalar pairing interactions in β-decay calculations for possible r-process waiting point nuclei with N ~ 82 and 126* *Supported by the National Natural Science Foundation of China (11575120, 11822504), and Science Specialty Program of Sichuan University (2020SCUNL210)

In this study, we adopt the self-consistent Hartree-Fock-Bogoliubov (HFB) theory with the proton-neutron quasi-particle random phase approximation (pnQRPA) based on the Skyrme force for calculation of the β − decay half-lives for nuclei with N ~ 82 and 126 on possible r-process paths. In the calculations, the Skyrme interaction (e.g., SKO') is adopted, and the tensor interaction is added self-consistently in both HFB and QRPA calculations. We systematically study how the half-life is changed by varying the strength of the triplet-even (TE) and triplet-odd (TO) components as well as the IS pairing. We find that a variation in strength of the IS pairing of approximately 20% does not produce a substantial effect on β-decay rates with or without the tensor force, while a strength variation of the TO tensor force considerably affects the change in the β-decay half-lives for the very neutron rich N ~ 82 and 126 isotonic chains. In addition, with the inclusion of the tensor force, the GT decay becomes dominant for very neutron-rich nuclei.

Final Result on the Neutrinoless Double Beta Decay of ^{82}Se with CUPID-0.

CUPID-0, an array of Zn^{82}Se cryogenic calorimeters, was the first medium-scale demonstrator of the scintillating bolometers' technology. The first project phase (March 2017-December 2018) allowed the most stringent limit on the neutrinoless double beta decay half-life of the isotope of interest, ^{82}Se, to be set. After a six month long detector upgrade, CUPID-0 began its second and last phase (June 2019-February 2020). In this Letter, we describe the search for neutrinoless double beta decay of ^{82}Se with a total exposure (phase I+II) of 8.82 kg yr^{-1} of isotope. We set a limit on the half-life of ^{82}Se to the ground state of ^{82}Kr of T_{1/2}^{0ν}(^{82}Se)>4.6×10^{24} yr (90% credible interval), corresponding to an effective Majorana neutrino mass m_{ββ}<(263-545) meV. We also set the most stringent lower limits on the neutrinoless decays of ^{82}Se to the 0_{1}^{+}, 2_{1}^{+}, and 2_{2}^{+} excited states of ^{82}Kr, finding 1.8×10^{23} yr, 3.0×10^{23} yr, and 3.2×10^{23} yr (90% credible interval) respectively.

A unified formula for $$\alpha $$ decay half-lives

A unified formula for $$\alpha $$ decay half-lives

Neutrino masses and mass hierarchy: evidence for the normal hierarchy

The latest cosmological constraints on the sum of neutrino masses, in combination with the latest laboratory measurements on oscillations, provide “decisive” Bayesian evidence for the normal neutrino mass hierarchy. We show that this result holds across very different prior alternatives by exploring two extremes on the range of prior choices. In fact, while the specific numerical value for the Evidence depends on the choice of prior, the Bayesian odds remain greater than 140:1 across very different prior choices. For Majorana neutrinos this has important implications for the upper limit of the neutrino-less double beta decay half life and thus for the technology and resources needed for future double beta decay experiments.

Theoretical calculations of the alpha decay half-lives of 166−190Pt

Calculations of the α-decay half-lives of Pt isotopes have been carried out using the modified Gamow-like model (MGLM) and deformed Woods-Saxon potential model. In order to see the effect of using deformed nuclear potential on the α-decay half-lives of the Platinum isotopes, the spherical Woods-Saxon potential has also been employed in the computation. When compared with experimental data, all the modelsgive very good descriptions of the experimental half-lives. The comparison also suggests that the calculated half-lives considering deformation give better agreement with the experimental data than the results using spherical configuration. New parameter values were obtained for the MGLM model (termed MGLM2). The MGLM2 model gives better descriptions of the half-lives than the MGLM1 model.