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This study presents a parallel algorithm for high-dimensional quantum dynamics simulations in poly atomic reactions, integrating distributed- and shared-memory models. The distributions of the wave function and potential energy matrix across message passing interface processes are based on bundled radial and angular dimensions, with implementations featuring either two- or one-sided communication schemes. Using realistic parameters for the H + NH3 reaction, performance assessment reveals linear scalability, exceeding 90% efficiency with up to 600 processors. In addition, owing to the universal and concise structure, the algorithm demonstrates remarkable extensibility to diverse reaction systems, as demonstrated by successes with six-atom and four-atom reactions. This work establishes a robust foundation for high-dimensional dynamics studies, showcasing the algorithm's efficiency, scalability, and adaptability. The algorithm's potential as a valuable tool for unraveling quantum dynamics complexities is underscored, paving the way for future advancements in the field. [ABSTRACT FROM AUTHOR]

Free energy simulations that employ combined quantum mechanical and molecular mechanical (QM/MM) potentials at ab initio QM (AI) levels are computationally highly demanding. Here, we present a machine-learning-facilitated approach for obtaining AI/MM-quality free energy profiles at the cost of efficient semiempirical QM/MM (SE/MM) methods. Specifically, we use Gaussian process regression (GPR) to learn the potential energy corrections needed for an SE/MM level to match an AI/MM target along the minimum free energy path (MFEP). Force modification using gradients of the GPR potential allows us to improve configurational sampling and update the MFEP. To adaptively train our model, we further employ the sparse variational GP (SVGP) and streaming sparse GPR (SSGPR) methods, which efficiently incorporate previous sample information without significantly increasing the training data size. We applied the QM-(SS)GPR/MM method to the solution-phase SN2 Menshutkin reaction, N H 3 + C H 3 C l → C H 3 N H 3 + + C l − , using AM1/MM and B3LYP/6-31+G(d,p)/MM as the base and target levels, respectively. For 4000 configurations sampled along the MFEP, the iteratively optimized AM1-SSGPR-4/MM model reduces the energy error in AM1/MM from 18.2 to 4.4 kcal/mol. Although not explicitly fitting forces, our method also reduces the key internal force errors from 25.5 to 11.1 kcal/mol/ A ̊ and from 30.2 to 10.3 kcal/mol/ A ̊ for the N–C and C–Cl bonds, respectively. Compared to the uncorrected simulations, the AM1-SSGPR-4/MM method lowers the predicted free energy barrier from 28.7 to 11.7 kcal/mol and decreases the reaction free energy from −12.4 to −41.9 kcal/mol, bringing these results into closer agreement with their AI/MM and experimental benchmarks. [ABSTRACT FROM AUTHOR]

Bi-based materials can retain massive amounts of sodium ions through alloying and conversion reactions, resulting in excellent theoretical capacity. However, during the sodiation/desodiation process, there is always a significant volume change in the alloying reaction. In this work, TiO2-coated hexagonal-phase topological insulator (TI) Bi2Te3 composites grown on carbon cloth (CC) were prepared using a solvothermal reaction and an atomic layer deposition process (TiO2/Bi2Te3/CC) as anode materials for sodium-ion batteries without the need for a binder. Compared to the pure Bi2Te3 electrode, the optimized TiO2/Bi2Te3/CC composite exhibits a superior specific capacity of 450 mA h g−1, a high rate performance of 0.1 A g−1, and a high cycling stability of 100 cycles due to the inherent properties of TIs, contributed by the effective TiO2 cladding layer and large interfacial spacing of Bi2Te3. The enhanced reversible capacitance, rate capability, and cycling performances can be attributed to the heterointerfaces and excellent mechanical properties of TiO2, which balance the electronic structure of the building blocks and inhibit the detaching of Bi2Te3 due to large internal stresses. The amorphous TiO2/Bi2Te3/CC composite was treated in a tubular furnace to obtain crystalline TiO2/Bi2Te3/CC, and the electrochemical performance of the heterostructures formed by the TiO2 coating layer with different properties was compared. This work demonstrates the enormous potential for enhancing the sodium-ion storage capabilities of alloy electrode materials by constructing heterostructures. [ABSTRACT FROM AUTHOR]

Precisely controlling the microstructure of supported metal catalysts and regulating metal‐support interactions at the atomic level are essential for achieving highly efficient heterogeneous catalysts. Strong metal‐support interaction (SMSI) not only stabilizes metal nanoparticles and improves their resistance to sintering but also modulates the electrical interaction between metal species and the support, optimizing the catalytic activity and selectivity. Therefore, understating the formation mechanism of SMSI and its dynamic evolution during the chemical reaction at the atomic scale is crucial for guiding the structural design and performance optimization of supported metal catalysts. Recent advancements in in situ transmission electron microscopy (TEM) have shed new light on these complex phenomena, providing deeper insights into the SMSI dynamics. Here, the research progress of in situ TEM investigation on SMSI in heterogeneous catalysis is systematically reviewed, focusing on the formation dynamics, structural evolution during the catalytic reactions, and regulation methods of SMSI. The significant advantages of in situ TEM technologies for SMSI research are also highlighted. Moreover, the challenges and probable development paths of in situ TEM studies on the SMSI are also provided. [ABSTRACT FROM AUTHOR]

Chemical evolution models predict a gradual build-up of 13C in the Universe, based on empirical nuclear reaction rates and assumptions on the properties of stellar populations. However, old metal-poor stars within the Galaxy contain more 13C than is predicted, suggesting that further refinements to the models are necessary. Gas at high-redshift provides important supplementary information at metallicities |$-2\lesssim \left[{\rm Fe/H}\right]\lesssim -1$|⁠ , for which there are only a few measurements in the Galaxy. We obtained new, high-quality, VLT/ESPRESSO observations of the QSO B1331 |$+$| 170 and used them to measure 12C/13C in the damped Lyman- |$\alpha$| system (DLA) at |$z_{\rm abs}=1.776$|⁠ , with |$\left[{\rm Fe/H}\right]$| = −1.27. ai-vpfit , an artificial intelligence tool based on genetic algorithms and guided by a spectroscopic information criterion, was used to explore different possible kinematic structures of the carbon gas. Three hundred independent ai-vpfit models of the absorption system were produced using pre-set 12C/13C values, ranging from 4 to 500. Our results show that |${\rm ^{12}C / ^{13}C}=28.5^{+51.5}_{-10.4}$|⁠ , suggesting a possibility of 13C production at low metallicity. [ABSTRACT FROM AUTHOR]

Fusion is inherently safer than fission due to the absence of nuclear chain reactions. However, operating fusion power plants will not be risk free. There will still be numerous hazards that will need careful management in order to safely build, operate and ultimately decommission a fusion power plant. Ensuring a robust safety demonstration that covers all radiological and non-radiological hazards is therefore vitally important for the future permissioning and consenting of fusion power plants. The safety case for the STEP prototype plant will be developed in line with a set of safety philosophies, safety functional requirements and design safety principles to ensure that the safety case production process is consistent and robust. This article is part of the theme issue 'Delivering Fusion Energy – The Spherical Tokamak for Energy Production (STEP)'. [ABSTRACT FROM AUTHOR]

On October 22, 1934, in a fateful experiment, Enrico Fermi and his associates at the University of Rome discovered that neutrons in hydrogen-rich media slow down and acquire enhanced capability for nuclear reactions. The utilization of this phenomenon had far-reaching implications in science and world events. [ABSTRACT FROM AUTHOR]

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for 30F, 30Ne, 30Na, 30Mg, 30Al, 30Si, 30P, 30S, 30Cl, and 30Ar. The recommended values for the level energies and their percentage decay modes, level lifetimes, γ energies, γ branching ratios, transition probabilities, etc. are presented. Among these nuclides, 30F is unobserved and most likely particle unbound. Additional experimental data are required for firm spin-parity assignments of the low-lying excited levels of 30Ne. The most well studied nuclide is 30Si followed by 30P. The data for the most proton-rich nuclide 30Ar are presented following the recent work of 2018Xu04 and 2015Mu13. This evaluation for A=30 supersedes the previous one, 2010Ba29. [ABSTRACT FROM AUTHOR]

The goal of this work is to characterize the secondary neutron spectra produced by 1 GeV/u56Fe beam colliding with a thick cylindric aluminum target and to perform a quantitative comparison with simulated results obtained with Monte Carlo codes. The measurements were performed using extended-range Bonner sphere spectrometers at two positions (15° and 40°) with respect to the beam direction. The secondary radiation field was simulated using four Monte Carlo codes (FLUKA, MCNP6, Geant4 and PHITS) and several physical models of nuclei transport and interaction. Neutron and proton energy distributions were simulated for the experimental measurement positions. The simulated neutron spectra, together with data measured with Bonner sphere spectrometers, after carrying out the correction of the contributions induced by the secondary protons, were used as input for the MAXED spectrum unfolding code to obtain the measured neutron spectra. Unfolded neutron spectra were compared with simulated ones to carry out a quantitative analysis of the performance of the chosen Monte Carlo codes and their corresponding physical models. This comparison showed that, because of experimental uncertainties and physical models, there are no unique solutions for each measurement location, but a range of solutions where the true experimental neutron spectra probably lie. The results showed deviations between 4.23% and 8.42% for some simulated spectra. Regarding the total integral values of neutron fluence and ambient equivalent dose, the unfolded neutron spectra showed deviations lower than 2%. [ABSTRACT FROM AUTHOR]

This article presents a kinetic study of fusion burn waves in compressed deuterium-tritium and proton-boron plasmas. The study uses particle-in-cell simulations with Monte Carlo collisions to analyze the energy balance in the expansion of a hot-spot, capturing alpha particle heating and radiative losses. The simulations show that the energy radiated by the hot-spot is recaptured by the surrounding high-density fuel, resulting in a net fusion energy production that is twice the initial hot-spot energy. The study provides insights into the feasibility of proton-boron fusion as an alternative fusion fuel. The given text describes a simulation model for studying Coulomb collisions, fusion reactions, and bremsstrahlung radiation in high-density, highly-collisional systems. The model uses a binary Monte Carlo collision method to simulate these interactions between particles. The text explains the implementation of bremsstrahlung emission and inverse bremsstrahlung absorption in the simulation model. The model is verified through simulations of bremsstrahlung emission from an electron beam incident on solid boron, laser heating of a hydrogen plasma, and photon emission and absorption in a p-11B plasma. The given text discusses the results of simulations on various plasma scenarios. The simulations include laser heating of a hydrogen plasma, fusion burn waves in compressed DT and p-11B plasmas, and the measurement of radiation and fusion power density in a fully ionized p-11B plasma. The results show close agreement between the simulations and other [Extracted from the article]

Background Purpose Methods Results Conclusions In‐vivo monitoring methods of carbon ion radiotherapy (CIRT) includes explorations of nuclear reaction products generated by carbon‐ion beams interacting with patient tissues. Our research group focuses on in‐vivo monitoring of CIRT using silicon pixel detectors. Currently, we are conducting a prospective clinical trial as part of the In‐Vivo Monitoring project (InViMo) at the Heidelberg Ion Beam Therapy Center (HIT) in Germany. We are using an innovative, in‐house developed, non‐contact fragment tracking system with seven mini‐trackers based on the Timepix3 technology developed at CERN.This article focuses on the implementation of the mini‐tracker in Monte Carlo (MC) based on FLUKA simulations to monitor secondary charged nuclear fragments in CIRT. The main objective is to systematically evaluate the simulation accuracy for the InViMo project.The implementation involved integrating the mini‐tracker geometry and the scoring mechanism into the FLUKA MC simulation, utilizing the finely tuned HIT beam line. The systematic investigation included varying mini‐tracker angles (from 15∘$15^\circ$ to 45∘$45^\circ$ in 5∘$5^\circ$ steps) during the irradiation of a head‐sized phantom with therapeutic carbon‐ion pencil beams. To evaluate our implemented FLUKA framework, a comparison was made between the experimental data and data obtained from MC simulations. To ensure the fidelity of our comparison, experiments were performed at the HIT using the parameters and setup established in the simulations.Our research demonstrates high accuracy in reproducing characteristic behaviors and dependencies of the monitoring method in terms of fragment distributions in the mini‐tracker, track angles, emission profiles, and fragment numbers. Discrepancies in the number of detected fragments between the experimental data and the data obtained from MC simulations are less than 4% for the angles of interest in the InViMo detection system.Our study confirms the potential of our simulation framework to investigate the performance of monitoring inter‐fractional anatomical changes in patients undergoing CIRT using secondary nuclear charged fragments escaping from the irradiated patient. [ABSTRACT FROM AUTHOR]

Material expelled from binary neutron star (BNS) mergers can harbour r-process nucleosynthesis and power a kilonova (KN), both intimately related to the astrophysical conditions of the ejection. In turn such conditions indirectly depend on the equation of state (EOS) describing matter inside the neutron star. Therefore, in principle the above observables can hold valuable information on nuclear matter, as the merger gravitational wave signal already does. In this work, we consider the outcome of a set of BNS merger simulations employing different finite-temperature nuclear EOSs. The latter are obtained from a Skyrme-type interaction model where nuclear properties, such as the incompressibility and the nucleon effective mass at saturation density, are systematically varied. We post-process the ejecta using a reaction network coupled with a semi-analytic KN model, to assess the sensitivity on the input EOS of the final yields and the KN light curves. Both of them are found to be non-trivially influenced by the EOS, with the overall outcome being dominated by the heterogeneous outflows from the remnant disc, hosting a variable degree of neutron-rich material. The dynamical ejecta can be more directly related to the EOS parameters considered; however, we find their role in the yields production and the KN emission too entangled with the other ejecta components, in order to infer solid correlations. This result highlights the strong degeneracy that intervenes between the merger outcome and the behaviour of the intrinsic nuclear matter, and places itself as a limit to the employment of EOS-constraining approaches of such kind. [ABSTRACT FROM AUTHOR]

We compute the structure of a Newtonian, multi-ion radiation-mediated shock (RMS) for different compositions anticipated in various stellar explosions. We use a multifluid RMS model that incorporates electrostatic coupling between the different plasma constituents as well as Coulomb friction in a self-consistent manner, and approximates the effect of pair creation and the presence of free neutrons in the shock upstream on the shock structure. We find that under certain conditions a significant velocity separation is developed between different ions in the shock downstream and demonstrate that in fast enough shocks ion–ion collisions may trigger fusion and fission events at a relatively high rate. Our analysis ignores anomalous coupling through plasma microturbulence, which might reduce the velocity spread downstream below the activation energy for nuclear reactions. A rough estimate of the scale separation in RMS suggests that for shocks propagating in binary neutron star (BNS) merger ejecta, the anomalous coupling length may exceed the radiation length, allowing a considerable composition change behind the shock via inelastic collisions of |$\alpha$| particles with heavy elements at shock velocities |$\beta _\mathrm{ u}\gtrsim 0.25$|⁠. A sufficient abundance of free neutrons in the shock upstream, as expected during the first second after the merger, is also expected to alter the ejecta composition through neutron capture downstream. The resultant change in the composition profile may affect the properties of the early kilonova emission. The generation of microturbulence due to velocity separation can also give rise to particle acceleration that might alter the breakout signal in supernovae and other systems. [ABSTRACT FROM AUTHOR]

Gas-phase abundance ratios between C2H4O2 isomers methyl formate (MF), glycolaldehyde (GA), and acetic acid (AA) are typically on the order of 100:10:1 in star-forming regions. However, an unexplained divergence from this neat relationship was recently observed toward a collection of sources in the massive protocluster NGC 6334I; some sources exhibited extreme MF:GA ratios, producing a bimodal behavior between different sources, while the MF:AA ratio remained stable. Here, we use a three-phase gas-grain hot-core chemical model to study the effects of a large parameter space on the simulated C2H4O2 abundances. A combination of high gas densities and long timescales during ice-mantle desorption (∼125–160 K) appears to be the physical cause of the high MF:GA ratios. The main chemical mechanism for GA destruction occurring under these conditions is the rapid adsorption and reaction of atomic H with GA on the ice surfaces before it has time to desorb. The different binding energies of MF and GA on water ice are crucial to the selectivity of the surface destruction mechanism; individual MF molecules rapidly escape the surface when exposed by water loss, while GA lingers and is destroyed by H. Moderately elevated cosmic-ray ionization rates can increase absolute levels of "complex organic molecule" (COM) production in the ices and increase the MF:GA ratio, but extreme values are destructive for gas-phase COMs. We speculate that the high densities required for extreme MF:GA ratios could be evidence of COM emission dominated by COMs desorbing within a circumstellar disk. [ABSTRACT FROM AUTHOR]

We present a new set of reference materials, the ND70‐series, for in situ measurement of volatile elements (H2O, CO2, S, Cl, F) in silicate glass of basaltic composition. The materials were synthesised in piston cylinders at pressures of 1 to 1.5 GPa under volatile‐undersaturated conditions. They span mass fractions from 0 to 6% m/m H2O, from 0 to 1.6% m/m CO2 and from 0 to 1% m/m S, Cl and F. The materials were characterised by elastic recoil detection analysis for H2O, by nuclear reaction analysis for CO2, by elemental analyser for CO2, by Fourier transform infrared spectroscopy for H2O and CO2, by secondary ion mass spectrometry for H2O, CO2, S, Cl and F, and by electron probe microanalysis for CO2, S, Cl and major elements. Comparison between expected and measured volatile amounts across techniques and institutions is excellent. It was found however that SIMS measurements of CO2 mass fractions using either Cs+ or O− primary beams are strongly affected by the glass H2O content. Reference materials have been made available to users at ion probe facilities in the US, Europe and Japan. Remaining reference materials are preserved at the Smithsonian National Museum of Natural History where they are freely available on loan to any researcher. [ABSTRACT FROM AUTHOR]

The elastic and inelastic scattering of deuterons on 10B nuclei and the 10B(d, t)9B reaction were studied at a deuteron energy of 14.5 MeV. In inelastic scattering, differential cross-sections for transitions to 10B states at excitation energies, Ex, of 0.718 MeV (1+), 2.154 MeV (1+), and 3.59 MeV (2+) were measured. The cross-sections of the (d, t) reaction were measured for the ground (3/2−) and excited states of the 9B nucleus at Ex = 2.361 MeV (5/2−) and 2.79 MeV (5/2+). An analysis of the corresponding angular distributions was carried out using the coupled channel method. As a result of the calculations, the values of the quadrupole deformation parameters (β2 ≈ 0.7 ± 0.1) for various transitions in the 10B nucleus in inelastic scattering were extracted. From the analysis of the (d, t) reaction, the values of spectroscopic amplitudes (SA = 0.67 and SA = 0.94) for transitions to the states of the 9B nucleus were extracted. The results obtained here, taking into account possible measurement errors, are in good agreement with the previously obtained data and the theoretical predictions. [ABSTRACT FROM AUTHOR]

This paper focuses on the highly radioactive, long-lasting nuclear waste produced by the currently operating fission reactors and on the sensitive issue of spent fuel reprocessing. Also included is a short description of the fission process and a detailed analysis of the more hazardous radioisotopes produced either by secondary reactions occurring in the nuclear installations or by decay of the fission fragments. The review provides an overview of the strategies presently adopted to minimize the harmfulness of the nuclear waste to be disposed, with a focus on the development and implementation of methodologies for the spent fuel treatments. The partitioning-conditioning and partitioning-transmutation options are analyzed as possible solutions to decrease the presence of long-lived highly radioactive isotopes. Also discussed are the chemical/physical approaches proposed for the recycling of the spent fuel and for the reusing of some technologically relevant isotopes in industrial and pharmaceutical areas. A brief indication is given of the opportunities offered by innovative types of reactors and/or of new fuel cycles to solve the issues presently associated with radioactive waste. [ABSTRACT FROM AUTHOR]

Estimations of counting rates of neutron spectrometers in experiments on controlled fusion with magnetic confinement, as well as calculations of energy resolved flux densities of fusion neutrons from plasma to the walls of a reactor require spatial integration of the local, usually anisotropic function of the neutron source. The integrated modeling consists of three main stages. First, sources of fast particles in beam- or wave-heated plasma are calculated. The next stage deals with spatial, energetic, and angular velocity distributions of plasma ions. Finally, double differential rate coefficients of nuclear fusion reactions are computed. This article describes calculations of spatial distributions of nuclear fusion reaction rates in classical and spherical tokamaks and the anisotropy of the neutron yield and spectra. The results are based on analytical formulas for energetic and angular distributions of the local source of fusion products in plasma. Examples of energetic spectral densities of neutron fluxes on first walls are presented, as well as energy resolved counting rates of collimated neutron spectrometers for perpendicular and tangential lines of sight. [ABSTRACT FROM AUTHOR]

The field of nuclear science has considerably advanced since its beginning just over a century ago. Today, the science of rare isotopes is on the cusp of a new era with theoretical and computing advances complementing experimental capabilities at new facilities internationally. In this article we present a vision for the science of rare isotope beams (RIBs). We do not attempt to cover the full breadth of the field; rather, we provide a perspective and address a selection of topics that reflect our own interests and expertise. We focus in particular on systems near the drip lines, where one often finds nuclei that are referred to as exotic and where the role of the nuclear continuum is only just starting to be explored. An important aspect of this article is its attempt to highlight the crucial connections between nuclear structure and the nuclear reactions required to fully interpret and leverage the rich data to be collected in the next years at RIB facilities. Further, we connect the efforts in structure and reactions to key questions of nuclear astrophysics. [ABSTRACT FROM AUTHOR]

In nuclear medicine radionuclides are used in diagnosis and therapy. They can be produced in cyclotrons with different nuclear reactions. Overall goal is the optimization of the yield of the desired radionuclide which is possible by changing different experimental parameters. To test the influence of these parameters to obtain an optimal yield, simulation programs like PHITS and FLUKA can be used. In first studies (see Klink et al. [Testing the suitability of FLUKA and PHITS to predict the outcome of radionuclide production. Radiat. Eff. Defects Solids2023, 178 (1–2), 111–125]) the experimental yields of nuclide productions were compared with simulation results of different target designs with perpendicular and inclined configuration. In this paper we focus on the effect of inclination since it was one of the problematic cases of the previous study [Klink et al. Testing the suitability of FLUKA and PHITS to predict the outcome of radionuclide production. Radiat. Eff. Defects Solids2023, 178 (1–2), 111–125]. Different beam profiles were varied in the simulations to determine its influence on the simulated yields. The choice of the beam profile has a great influence on simulating irradiations of inclined targets. With a known beam profile and other experimental conditions, FLUKA can be used to simulate nuclide productions of inclined targets with small deviations compared to the experimental yields. In conclusion, FLUKA can be used to determine the yield of unknown nuclide production with different target designs. [ABSTRACT FROM AUTHOR]

Strong metallicity-dependent winds dominate the evolution of core He-burning, classical Wolf–Rayet (cWR) stars, which eject both H and He-fusion products such as |$^{14}$| N, |$^{12}$| C, |$^{16}$| O, |$^{19}$| F, |$^{22}$| Ne, and |$^{23}$| Na during their evolution. The chemical enrichment from cWRs can be significant. cWR stars are also key sources for neutron production relevant for the weak s-process. We calculate stellar models of cWRs at solar metallicity for a range of initial Helium star masses (12–50  |$\rm M_{\odot }$|⁠), adopting recent hydrodynamical wind rates. Stellar wind yields are provided for the entire post-main sequence evolution until core O-exhaustion. While literature has previously considered cWRs as a viable source of the radioisotope |$^{26}$| Al, we confirm that negligible |$^{26}$| Al is ejected by cWRs since it has decayed to |$^{26}$| Mg or proton-captured to |$^{27}$| Al. However, in Paper I, we showed that very massive stars eject substantial quantities of |$^{26}$| Al, among other elements including N, Ne, and Na, already from the zero-age-main-sequence. Here, we examine the production of |$^{19}$| F and find that even with lower mass-loss rates than previous studies, our cWR models still eject substantial amounts of |$^{19}$| F. We provide central neutron densities (N |$_{n}$|⁠) of a 30  |$\rm M_{\odot }$| cWR compared with a 32  |$\rm M_{\odot }$| post-VMS WR and confirm that during core He-burning, cWRs produce a significant number of neutrons for the weak s-process via the |$^{22}$| Ne(⁠|$\alpha$|⁠ ,n) |$^{25}$| Mg reaction. Finally, we compare our cWR models with observed [Ne/He], [C/He], and [O/He] ratios of Galactic WC and WO stars. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) stellar evolution models are widely used across various astrophysical fields, however they are still dominated by important uncertainties that deeply affect their predictive power. Among those, the merging of independent convective regions is a poorly understood phenomenon predicted by some 1D models but whose occurrence and impact in real stars remain very uncertain. Being an intrinsically multi-D phenomenon, it is challenging to predict the exact behaviour of shell mergers with 1D models. In this work, we conduct a detailed investigation of a multiple shell merging event in a 20 M |$_\odot$| star using 3D hydrodynamic simulations. Making use of the active tracers for composition and the nuclear network included in the 3D model, we study the merging not only from a dynamical standpoint but also considering its nucleosynthesis and energy generation. Our simulations confirm the occurrence of the merging also in 3D, but reveal significant differences from the 1D case. Specifically, we identify entrainment and the erosion of stable regions as the main mechanisms that drive the merging, we predict much faster convective velocities compared to the mixing-length theory velocities, and observe multiple burning phases within the same merged shell, with important effects for the chemical composition of the star, which presents a strongly asymmetric (dipolar) distribution. We expect that these differences will have important effects on the final structure of massive stars and thus their final collapse dynamics and possible supernova explosion, subsequently affecting the resulting nucleosynthesis and remnant. [ABSTRACT FROM AUTHOR]

With a suitable half-life and abundant radiolabeling strategy, 225Ac has become one of the most promising radionuclides in the area of targeted alpha therapy. However, limited radionuclide supply is threatening the development of 225Ac related endoradiotherapy dramatically. As the parent nuclide of 225Ac, 229Th can be produced via 226Ra(3n, 2ß)229Th reaction in a nuclear reactor. However, related practice has not been conducted in large scale, since the nuclear reaction pathway for producing 229Th is complicated. In this work, the feasibility of producing 225Ac/229Th in a reactor was confirmed by systematic theoretical calculations, and a procedure that combines irradiation with separation process was proposed. The results show that 176 MBq of 229Th can be produced by irradiating 1.0 g of 226Ra with a neutron flux density of 1 × 1015 n cm-2 s1 for 90 days. This will generate 150 MBq of 225Ac monthly from a radionuclide generator, which is sufficient for the single treatment cycle of 200 patients each year considering the radioactivity loss in radiochemical separation, transfer and radiolabeling process. In addition, this irradiation process will also produce 37.8 GBq 227Ac for the preparation of 227Ac-227Th-223Ra generator. In general, the production of 225Ac by neutron irradiation of 226Ra in reactor is practicable and holds potential to alleviate the shortage of current supply of 225Ac. [ABSTRACT FROM AUTHOR]

A thorough understanding of nuclear reaction rates at low energies is essential for improving our understanding of energy generation in stars and primordial and stellar nucleosynthesis. At low energies, fusion reactions between charged particles are strongly suppressed by the presence of the Coulomb barrier, which classically inhibits the penetration of one nucleus into another. The barrier penetration causes the cross section to have a steep energy dependence at low energies, making cross section measurements very challenging. Furthermore, little is known about the impact of surrounding electrons in stellar plasmas that are currently beyond the reach of experiments. As a result, measuring the bare cross sections as accurately as possible is essential. Reaction rate measurements at very low energies have been made possible in recent years by the development of high-current low-energy accelerators as well as enhanced target and detection methods. Nevertheless, the presence of atomic electrons, which alter the Coulomb barrier by screening the nuclear charge and increase the cross section at low energies compared to the case of bare nuclei, complicates these observations. A review of the experimental and corresponding theoretical work on laboratory electron screening performed so far will be presented. [ABSTRACT FROM AUTHOR]

Purpose: In this paper we compare the main AB-BNCT facilities worldwide in terms of neutron-producing nuclear reactions, existing technologies and machines, and induced radioactivity both at the target and at the beam shaping assembly (BSA) level, by the resulting neutron beam. We also provide information on several aspects of the Buenos Aires project. Methods: A comparison is made of the different active AB-BNCT projects and facilities worldwide using the information available in the literature. The radioactivity induced by both the direct beams (protons or deuterons) at the targets (7Li, 9Be and 13C) and the neutron beams at the BSAs is discussed. The main technical features of the Argentina project are presented. Results: There are a number of different facilities for Accelerator-Based BNCT (AB-BNCT) worldwide, some already working and even treating patients and some under development and construction. They range from high-energy 30 MeV cyclotrons (using the 9Be(p,n) reaction), medium-energy RFQ-DTL accelerators (at 8 and 10 MeV using likewise the 9Be(p,n) reaction), low-energy electrostatic, both Tandem and single-ended, and RFQ machines (working on 7Li(p,n) at about 2.5 MeV), to a very low-energy single-ended electrostatic quadrupole accelerator, ESQ (working on 9Be(d,n) or 13C(d,n) at 1.45 MeV). This last accelerator, its ancillary systems and the associated facility is being developed and constructed at the National Atomic Energy Commission of Argentina. An important aspect about these facilities, relevant for their long term sustainability, is the production of radioactivity, which should be kept at a minimum according to the ALARA criterium, both at the neutron production target, by the primary beam, and at the Beam Shaping Assembly (BSA), by the induced neutrons. In a 30 day period with an operation schedule of 8 h a day the 7Li(p,n) at 2.3 MeV option produces 2.1 TBq of 7Be (30 mA), the Be(p,n) option at 8 MeV only produces prompt radiation while at 30 MeV (1 mA) other reaction channels are open which produce 0.39 TBq of 7Be and 4.2 GBq of 3H. The 13C(d,t) reaction produces 0.78 GBq of 3H. Conclusions: The use of exothermal deuteron-induced Be(d,n) and 13C(d,n) reactions allows us to use the smallest energy machine, at 1.45 MeV, for AB-BNCT. It is shown that among the systems proposed the 13C(d,n) solution is the one with the lowest overall activation (target + BSA). Coupled to an AlF3 BSA (which undergoes no long term activation), a 30 mA deuteron beam on a 13C target can deliver a good quality BNCT treatment for a deep seated brain tumor in one hour. [ABSTRACT FROM AUTHOR]

Controlling the precise growth of atoms is necessary to achieve manipulation of atomic composition and atomic position, regulation of electronic structure, and an understanding of reactions at the atomic level. Herein, we report a facile method for ordered anchoring of zero-valent platinum and manganese atoms with single-atom thickness on graphdiyne under mild conditions. Due to strong and incomplete charge transfer between graphdiyne and metal atoms, the formation of metal clusters and nanoparticles can be inhibited. The size, composition and structure of the bimetallic nanoplates are precisely controlled by the natural structure-limiting effect of graphdiyne. Experimental characterization clearly demonstrates such a fine control process. Electrochemical measurements show that the active site of platinum-manganese interface on graphdiyne guarantees the high catalytic activity and selectivity (~100%) for alkene-to-diol conversion. This work lays a solid foundation for obtaining high-performance nanomaterials by the atomic engineering of active site. This work reports a facile method for growing highly ordered Pt and Mn bimetallic single atomic layers on graphdiyne. This fully activates loaded metal atoms and results in in high activity and selectivity for electrocatalytic alkene-to-diol conversion [ABSTRACT FROM AUTHOR]

Lithium has broad applications in several emerging industries and fields, including high energy batteries, energy storage, aerospace, and controlled nuclear reactions. Currently, the discrepancy between the supply and demand for lithium resources increases, and its distribution is uneven. Within the framework of the "Belt and Road" Initiative, the lithium trade pattern evolves constantly. However, the trade pattern of lithium in the nations along the "Belt and Road" is likely to face substantial repercussions in modern world of unilateral protectionism and geopolitical conflicts. Taking the social network analysis approach as a tool, this study first examines the characteristics of the lithium trade network structure as it has evolved over the years in the Belt and Road countries, from 2000 to 2022. Additionally, this study uses the quadratic assignment problem approach to analyze the factors influencing the evolution of the lithium trade network. The study shows that: (1) The spatial patterns of import and export trade network of lithium in countries along the route has a certain path dependence. And the market is mainly concentrated in East Asia, Central and Eastern Europe, South America and Southeast Asia. (2) The network density of the countries along the route has increased year after year, but it remains low. And the fluctuation of the network's reciprocity has increased, with a huge magnitude of variation. The number of core countries in the network has decreased over time, but the core-periphery structure has stayed largely steady. China, Chile, and South Korea are the network's main node countries. (3) Regarding the influencing factors, the differences in economic and technological development between these countries have a beneficial impact on the formation of lithium trade; whether or not regional trade agreements have been signed, the differences about average tax rates for mineral products, bordering countries, and similar languages and cultures are all conducive to the establishment of close trade links. The contribution of this essay is of paramount importance for understanding different countries' role along the Belt and Road in the lithium trade network pattern, and promoting regional trade cooperation. [ABSTRACT FROM AUTHOR]

Developing atomically dispersed metal on nitrogen‐doped carbon (M─N─C) catalyst provides a promising strategy to convert CO2 into high‐valued chemicals and achieve artificially closed carbon cycles. However, it is challenging to tune the structure and coordination of N─M bond that further improve the intrinsic activity and selectivity of CO2RR. Herein, CuNi atomic clusters embedded in Ni/Cu dual atomic sites catalysts (CuNiAC@Ni/Cu─N─C) are designed and successfully manipulated to regulate the coordination environment for M─N─C catalysts to enhance the CO2 electroreduction reaction (CO2RR). The most active configuration in CuNiAC@Ni/Cu─N─C catalyst is CuNi atomic cluster connected with 2N‐bridged (Ni‐Cu)N5, in which two N atoms are shared with NiN4 and CuN3 moieties verified by both systematic advanced characterizations and density function theory (DFT) calculations. The results have revealed the integration between CuNi atomic cluster and N4Ni/CuN3 dual‐metal atomic sites that optimize the electronic redistribution and narrow the bandgap, thereby decreasing the energy barrier of the potential determination step and promoting CO production. [ABSTRACT FROM AUTHOR]

In actual atmospheric environments, Ni/Al composites subjected to high-velocity impact will undergo both intermetallic reaction and oxidative combustion simultaneously, and the coupling of mechanical and multiple chemical processes leads to extremely complex characteristics of energy release. This work employs ReaxFF molecular dynamics simulations to investigate the impact-induced deformation and energy release of a core–shell-structured Ni/Al nanoparticle in an oxygen environment. It was found that Al directly undergoes fragmentation, while Ni experiences plastic deformation, melting, and fragmentation in sequence as the impact velocity increased. This results in the final morphology of the nanoparticles being an ellipsoidal-clad nanoparticle, spherical Ni/Al melt, and debris cloud. Furthermore, these deformation characteristics are strongly related to the material property of the shell, manifested as Ni shell–Al core particle, being more prone to breakage. Interestingly, the dissociation phenomenon of Ni–Al–O clusters during deformation is observed, which is driven by Ni dissociation and Al oxidation. In addition, the energy release is strongly related to the deformation behavior. When the nanoparticle is not completely broken (Ni undergoes plastic deformation and melting), the energy release comes from the oxidative combustion of Al fragments and the intermetallic reaction driven by atomic mixing. When the nanoparticle is completely broken, the energy release mainly comes from the oxidative combustion of the debris cloud. At the same time, the promoting effect of oxygen concentration on the energy release efficiency is examined. These findings can provide atomic insights into the regulation of impact-induced energy release for reactive intermetallic materials. [ABSTRACT FROM AUTHOR]

Li–Al–O materials are interesting for several applications. Herein, a Li–Al–O thin‐film materials library, deposited by inert magnetron sputtering and postdeposition annealing in O2 atmosphere, is used to study the effects of different annealing temperatures (300–850 °C) and durations (1 min to 7 h) on crystallinity and composition of the films. X‐ray photoelectron spectroscopy depth profiling reveals inhomogeneous compositional depth profiles of conventionally annealed films (300–650 °C, 3–7 h) with increased Li contents toward the film surface and increased Al contents toward the film–substrate interface, as confirmed by a combination of Rutherford backscattering spectrometry and deuteron‐induced nuclear reaction analysis. The minimum temperature for the formation of crystalline LiAlO2 in the otherwise amorphous films is 550 °C. The undesired inhomogeneous depth profiles are transformed into homogeneous ones by rapid thermal annealing (750–850 °C, 1–10 min), while simultaneously causing the formation of crystalline LiAlO2. Therefore, rapid thermal annealing is shown to be more suitable than conventional annealing for the thermal processing of Li–Al–O thin films. Moreover, this conclusion is expected to have broader relevance beyond Li–Al–O materials, as it is likely to apply to other Li metal oxides, of which there are many technologically relevant ones. [ABSTRACT FROM AUTHOR]

Study of the nuclear structure of nuclides used for medical diagnosis using positron emission tomography (PET) is presented in this work. These nuclides are 11C, 13N, 15O and 18F, which are unstable by emitting β+ particles. They have half-lives of several minutes, which make them suitable radionuclides for PET. These radionuclides are produced through nuclear reactions using a cyclotron.  Studying the nuclear structure of these light nuclides is performed through the shell model. The full space of the p-shell model is used for the p-shell nuclei, and the full space of the sd-shell model for the sd-shell nucleus. The study includes calculations of magnetic moments and quadrupole electric moments. Calculations of form factors are presented to give predictions for future experimental studies. Protons and neutrons’ effective charges are used to include core-polarization effects. The single-particle states used in the calculations are those of the harmonic oscillator potential. Excellent agreement is obtained between the calculated observables and the available experimental data. [ABSTRACT FROM AUTHOR]

Based on the ab initio scheme developed by the authors for calculating the asymptotic characteristics of decay channels of nuclear states—the method of orthogonal functions of cluster channels—an approach has been created that makes it possible to directly implement the results of ab initio calculations of -nucleon wave functions, as well as the partial decay widths of resonant states of compound nucleus obtained through their use, into calculations of cross sections for resonance nuclear reactions. Both calculated and reliably measured resonance energies can be employed in these calculations. Using the examples of such a theoretical analysis of the reaction cross sections for He and He, the efficiency of this approach and the wide prospects of its use in nuclear spectroscopy are demonstrated. [ABSTRACT FROM AUTHOR]

Fuel retention in plasma-facing components (PFCs) is a critical issue in future nuclear fusion reactors operating with Deuterium-Tritium (DT) regarding nuclear safety and fulfillment of the T cycle. However, during DT plasma operation, highly energetic neutrons will induce damage in the lattice of W PFCs causing enhanced fuel retention in defects or traps. Laser-Induced Breakdown Spectroscopy (LIBS) is a potential tool to monitor the T-content in situ in PFCs of future nuclear fusion devices. This article presents an ex situ study on pre-damaged W material after D plasma exposure to qualify the method and mimic conditions expected in a reactor. ITER grade W samples were displacement-damaged by 10.8 MeV W ions to a damage dose of 0.23 dpa and exposed to low temperature deuterium plasma at low energy in PlaQ. The resulting deuterium concentration was analyzed by using 3He Nuclear Reaction Analysis (depth resolution of ≈ 150 nm) as a well-established method, and LIBS (picosecond laser pulses, depth resolution of 15 nm). The sample with the highest deuterium concentration showed a deuterium-rich zone up to a depth of 1.13 μm using both techniques. This is close to the expected W ion-induced damage depth of ≈ 1 μm. The results imply that LIBS as an in situ technique for tritium monitoring could be a viable option for a reactor. [ABSTRACT FROM AUTHOR]

The production of light, energetic and low-flux ions as a secondary beam caused by nuclear reaction can be used in various branches of nuclear physics. Due to the limited availability of energy in small laboratories equipped with electrostatic accelerators, accessing energetic light particles is crucial. For this purpose, selected nuclear reactions were introduced. In this research, primary proton, deuterium and helium-3 beams with energy less than 2 MeV were used for samples with a thickness of 1019 atom.cm-2 and the yield of reactions was obtained. The laboratory setup was designed in such a way that in addition to the access to the nuclear reaction products with a suitable yield, favorable conditions were provided for the extraction and transfer of the reaction products as well as their interaction with the sample. In these exothermic nuclear reactions, the yield is in the order of 106 particles and secondary proton and alpha particles with energies of 4 to18.5 MeV have been obtained. Also, the selected reactions are in accordance with the radiation protection protocols of similar laboratories. [ABSTRACT FROM AUTHOR]

Excitation functions of alpha-particle induced nuclear reactions on natSn have been presented in the 11–40 MeV energy range. In the present study, the stacked-foil activation technique followed by offline gamma-ray spectrometry was used to measure the production of 119Te, 121Te, 122Sb and 126Sb from alpha-particle induced reactions on natSn. The TALYS nuclear code was used to calculate the theoretical predictions of the excitation functions of natSn(α,x) nuclear reactions. The measured data of the above-mentioned nuclear reactions were compared with the theoretical predictions and the experimental results available from EXFOR. In this study, covariance analysis was performed to calculate the uncertainty propagation in the measured cross sections. [ABSTRACT FROM AUTHOR]