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Abstract Although the multimessenger detection of the neutron star merger event GW170817 confirmed that mergers are promising sites producing the majority of nature’s heavy elements via the rapid neutron-capture process (r-process), a number of issues related to the production of translead nuclei—the actinides—remain to be answered. In this short review paper, we summarize the general requirements for actinide production in r-process and the impact of nuclear physics inputs. We also discuss recent efforts addressing the actinide production in neutron star mergers from different perspectives, including signatures that may be probed by future kilonova and γ-ray observations, the abundance scattering in metal-poor stars, and constraints put by the presence of short-lived radioactive actinides in the Solar system.

Abstract Nuclear astrophysics is an interdisciplinary research field of nuclear physics and astrophysics, seeking for the answer to a question, how to understand the evolution of the universe with the nuclear processes which we learn. We review the research activities of nuclear astrophysics in east and southeast Asia which includes astronomy, experimental and theoretical nuclear physics, and astrophysics. Several hot topics such as the Li problems, critical nuclear reactions and properties in stars, properties of dense matter, r-process nucleosynthesis, and ν-process nucleosynthesis are chosen and discussed in further details. Some future Asian facilities, together with physics perspectives, are introduced.

Nitrogen cycle is an essential process for environmental health. Dirammox (direct ammonia oxidation), encoded by the dnfT1RT2ABCD cluster, was a novel pathway for microbial N2 production defined in Alcaligenes ammonioxydans HO-1. Here, a copy of the cluster dnfT1RT2ABCD as a whole was proved to have existed and very conserved in all Alcaligenes genomes. Phylogenetic analyses based on 16S rRNA gene sequences and amino acid sequences of DnfAs, together with G + C content data, revealed that dnf cluster was evolved associated with the members of the genus Alcaligenes. Under 20% O2 conditions, 14 of 16 Alcaligenes strains showed Dirammox activity, which seemed likely taxon-related. However, the in vitro activities of DnfAs catalyzing the direct oxidation of hydroxylamine to N2 were not taxon-related but depended on the contents of Fe and Mn ions. The results indicated that DnfA is necessary but not sufficient for Dirammox activity. The fact that members of the genus Alcaligenes are widely distributed in various environments, including soil, water bodies (both freshwater and seawater), sediments, activated sludge, and animal–plant-associated environments, strongly suggests that Dirammox is important to the nitrogen cycle. In addition, Alcaligenes species are also commonly found in wastewater treatment plants, suggesting that they might be valuable resources for wastewater treatment.

A near-infrared (NIR) multichannel filter based on the use of a finite 1-D semiconductor metamaterial (MTM) photonic crystal (PC) is proposed. We consider a PC air/(AB)N/air, where N is the stack number, A is a dielectric layer, and B is a semiconductor MTM made of Al-doped ZnO (AZO) and ZnO. Resonant transmission peaks can be found in the frequency region where the permittivity of AZO/ZnO is negative. It is found that the channel number is equal to N - 1 for a given N and that resonant channels are located in a passband of the photonic band structure. Additionally, the channel positions are tunable, i.e., they can be tuned by the thicknesses of A and B, the filling factor of AZO, and the incidence angle as well. The design of NIR tunable multichannel filter is of technical use for semiconductor optoelectronics.

In astrophysical environments such as core-collapse supernovae and neutron star–neutron star or neutron star–black hole mergers where dense neutrino media are present, matter–neutrino resonances (MNRs) can occur when the neutrino propagation potentials due to neutrino–electron and neutrino–neutrino forward scattering nearly cancel each other. We show that neutrino flavor transformation through MNRs can be explained by multiple adiabatic solutions similar to the Mikheyev–Smirnov–Wolfenstein mechanism. We find that for the normal neutrino mass hierarchy, neutrino flavor evolution through MNRs can be sensitive to the shape of neutrino spectra and the adiabaticity of the system, but such sensitivity is absent for the inverted hierarchy.

We theoretically investigate the transmission properties at an interface between a dielectric and a lossy single-negative (SNG) material. The transmission property is specifically investigated in the refractive angle calculated by the inhomogeneous wave theory. With the existence of a loss in an SNG material, the calculated refractive angle can be negative. That is, the negative refraction phenomenon, which is an important consequence in a double-negative (DNG) material, can also be found in an SNG material. We analyze the refractive angle as functions of the angle of incidence, the wave frequency, and the loss. For the epsilon-permittivity SNG material, the frequency-dependent negative refractive angle is shown to possess a critical frequency at which the absolute value in the negative refractive angle attains a maximum.

In this work, we investigate the far-infrared wave properties for a ferroelectric material, i.e., lithium tantalate $(\hbox{LiTaO}_{3})$, in the double-negative region, i.e., both the real parts of permittivity and permeability are negative. The analysis has been done based on the calculated surface impedances for three model structures, i.e., material occupying semi-infinite space (structure I), material of a slab immersed in free space (structure II), and a layered structure made of film on a dielectric substrate (structure III). It is found that the surface impedance spectrum exhibits resonant behavior. In structure I, there are only two resonant points, which arise mainly from the pole of permeability and the zero of permittivity. In structure II, multiple resonances can be found, and they strongly rely on the film thickness. Finally, we specifically investigate the substrate resonant phenomenon in structure III.

Nitrogen (N2) gas in the atmosphere is partially replenished by microbial denitrification of ammonia. Recent study has shown that Alcaligenes ammonioxydans oxidizes ammonia to dinitrogen via a process featuring the intermediate hydroxylamine, termed "Dirammox" (direct ammonia oxidation). However, the unique biochemistry of this process remains unknown. Here, we report an enzyme involved in Dirammox that catalyzes the conversion of hydroxylamine to N2. We tested previously annotated proteins involved in redox reactions, DnfA, DnfB, and DnfC, to determine their ability to catalyze the oxidation of ammonia or hydroxylamine. Our results showed that none of these proteins bound to ammonia or catalyzed its oxidation; however, we did find DnfA bound to hydroxylamine. Further experiments demonstrated that, in the presence of NADH and FAD, DnfA catalyzed the conversion of 15N-labeled hydroxylamine to 15N2. This conversion did not happen under oxygen (O2)-free conditions. Thus, we concluded that DnfA encodes a hydroxylamine oxidase. We demonstrate that DnfA is not homologous to any known hydroxylamine oxidoreductases and contains a diiron center, which was shown to be involved in catalysis via electron paramagnetic resonance experiments. Furthermore, enzyme kinetics of DnfA were assayed, revealing a Km of 92.9 ± 3.0 μM for hydroxylamine and a kcat of 0.028 ± 0.001 s-1. Finally, we show that DnfA was localized in the cytoplasm and periplasm as well as in tubular membrane invaginations in HO-1 cells. To the best of our knowledge, we conclude that DnfA is the first enzyme discovered that catalyzes oxidation of hydroxylamine to N2. [ABSTRACT FROM AUTHOR]

Elements heavier than iron are being created in massive, explosive astrophysical scenarios such as core-collapse supernovae and neutron star mergers. Heavy element nucleosynthesis is a very complex process that requires the knowledge of the properties, mainly nuclear masses, neutron capture and beta-decay rates, of thousands of nuclei. However, due to the limitations of current experimental facilities, only a relatively small number of nuclei have so far been studied experimentally. Given the amount of nuclei, and the regions of the nuclear chart involved in the heavy element nucleosynthesis, it is necessary to use models that can be reliably applied to even the most exotic nuclei. Thus, the use of microscopic nuclear structure models presents itself as the logical choice, because the underlying microscopic theory of nuclear interaction is expected to be valid across the whole nuclear chart. In this manuscript, we present the results of a large-scale calculation of β-decay rates using a fully self-consistent theoretical framework based on the relativistic nuclear energy density functional. Taking into account the first-forbidden transitions, we are able to determine the regions of the nuclear chart where these transitions are critical for the description of the decay rates. Finally, we examine the β-delayed neutron emission in all neutron-rich nuclei, from the valley of stability to the limits of nuclear binding. The results of the study are applied in an r-process simulations where we obtain an improved description of the r-process abundance pattern. [ABSTRACT FROM AUTHOR]

We consider r-process nucleosynthesis in outflows from black hole accretion discs formed in double neutron star and neutron star-black hole mergers. These outflows, powered by angular momentum transport processes and nuclear recombination, represent an important - and in some cases dominant - contribution to the total mass ejected by the merger. Here we calculate the nucleosynthesis yields from disc outflows using thermodynamic trajectories from hydrodynamic simulations, coupled to a nuclear reaction network.We find that outflows produce a robust abundance pattern around the second r-process peak (mass number A ~ 130), independent of model parameters, with significant production of A < 130 nuclei. This implies that dynamical ejecta with high electron fraction may not be required to explain the observed abundances of r-process elements in metal poor stars. Disc outflows reach the third peak (A ~ 195) in most of our simulations, although the amounts produced depend sensitively on the disc viscosity, initial mass or entropy of the torus, and nuclear physics inputs. Some of our models produce an abundance spike at A = 132 that is absent in the Solar system r-process distribution. The spike arises from convection in the disc and depends on the treatment of nuclear heating in the simulations. We conclude that disc outflows provide an important - and perhaps dominant - contribution to the r-process yields of compact binary mergers, and hence must be included when assessing the contribution of these systems to the inventory of r-process elements in the Galaxy. [ABSTRACT FROM AUTHOR]

We have performed r-process calculations for matter ejected dynamically in neutron star mergers based on a complete set of trajectories from a three-dimensional relativistic smoothed particle hydrodynamic simulation with a total ejected mass of ~1.7 x 10-3M⊙. Our calculations consider an extended nuclear network, including spontaneous, β- and neutron-induced fission and adopting fission yield distributions from the ABLA code. In particular we have studied the sensitivity of the r-process abundances to nuclear masses by using different models. Most of the trajectories, corresponding to 90% of the ejected mass, follow a relatively slow expansion allowing for all neutrons to be captured. The resulting abundances are very similar to each other and reproduce the general features of the observed r-process abundance (the second and third peaks, the rare-earth peak, and the lead peak) for all mass models as they are mainly determined by the fission yields. We find distinct differences in the predictions of the mass models at and just above the third peak, which can be traced back to different predictions of neutron separation energies for r-process nuclei around neutron number N = 130. In all simulations, we find that the second peak around A ~ 130 is produced by the fission yields of the material that piles up in nuclei with A ≳ 250 due to the substantially longer β-decay half-lives found in this region. The third peak around A ~ 195 is generated in a competition between neutron captures and β decays during r-process freeze-out. The remaining trajectories, which contribute 10% by mass to the total integrated abundances, follow such a fast expansion that the r process does not use all the neutrons. This also leads to a larger variation of abundances among trajectories, as fission does not dominate the r-process dynamics. The resulting abundances are in between those associated to the r and s processes. The total integrated abundances are dominated by contributions from the slow abundances and hence reproduce the general features of the observed r-process abundances. We find that, at timescales of weeks relevant for kilonova light curve calculations, the abundance of actinides is larger than the one of lanthanides. This means that actinides can be even more important than lanthanides to determine the photon opacities under kilonova conditions. Moreover, we confirm that the amount of unused neutrons may be large enough to give rise to another observational signature powered by their decay. [ABSTRACT FROM AUTHOR]

IceCube has detected many TeV–PeV neutrinos, but their astrophysical origins remain largely unknown. Motivated by the observed late-time X-ray/optical bumps in some gamma-ray bursts (GRBs), we examine the correlation between IceCube neutrinos and GRBs allowing delayed neutrinos ∼days after the prompt gamma-rays. Although we have not found any definitive correlation, up to ∼10% of the events observed so far at IceCube may have been neutrinos produced by the late-time GRB activities at ∼1 day. Assuming a connection between some IceCube events and the late GRB bumps, we show in a model-independent way that GRB sites capable of producing late ∼PeV neutrinos should be nonrelativistic or mildly relativistic. We estimate the diffuse neutrino flux from such sources and find that they can possibly account for a few IceCube events. Future observations of high-energy neutrinos and late-time GRB afterglows can further test the above proposed connection. [ABSTRACT FROM AUTHOR]

A protoneutron star produced in a core-collapse supernova (CCSN) drives a wind by its intense neutrino emission. We implement active–sterile neutrino oscillations in a steady-state model of this neutrino-driven wind to study their effects on the dynamics and nucleosynthesis of the wind in a self-consistent manner. Using vacuum mixing parameters indicated by some experiments for a sterile νs of ∼1 eV in mass, we observe interesting features of oscillations due to various feedback. For the higher νs mass values, we find that oscillations can reduce the mass-loss rate and the wind velocity by a factor of ∼1.6–2.7 and change the electron fraction critical to nucleosynthesis by a significant to large amount. In the most dramatic cases, oscillations shift nucleosynthesis from dominant production of 45Sc to that of 86Kr and 90Zr during the early epochs of the CCSN evolution. [ABSTRACT FROM AUTHOR]

The discovery of a binary neutron star merger (NSM) through both its gravitational wave and electromagnetic emission has revealed these events to be key sites of r-process nucleosynthesis. Here, we evaluate the prospects of finding the remnants of Galactic NSMs by detecting the gamma-ray decay lines from their radioactive r-process ejecta. We find that 126Sn, which has several lines in the energy range 415–695 keV and resides close to the second r-process peak, is the most promising isotope, because of its half-life t1/2 = 2.30(14) × 105 yr being comparable to the ages of recent NSMs. Using a Monte Carlo procedure, we predict that multiple remnants are detectable as individual sources by next-generation γ-ray telescopes which achieve sub-MeV line sensitivities of ∼10−8–10−6γ cm−2 s−1. However, given the unknown locations of the remnants, the most promising search strategy is a systematic survey of the Galactic plane and bulge extending to high Galactic latitudes. Individual known supernova remnants which may be misclassified NSM remnants could also be targeted, especially those located outside the Galactic plane. Detection of a moderate sample of Galactic NSM remnants would provide important clues to unresolved issues such as the production of actinides in NSMs, properties of merging NS binaries, and even help distinguish them from rare supernovae as current Galactic r-process sources. We also investigate the diffuse flux from longer-lived nuclei (e.g., 182Hf) that could in principle trace the Galactic spatial distribution of NSMs over longer timescales, but find that the detection of the diffuse flux appears challenging even with next-generation telescopes. [ABSTRACT FROM AUTHOR]

The kilonova emission observed following the binary neutron star merger event GW170817 provided the first direct evidence for the synthesis of heavy nuclei through the rapid neutron capture process (r process). The late-time transition in the spectral energy distribution to near-infrared wavelengths was interpreted as indicating the production of lanthanide nuclei, with atomic mass number A≳140. However, compelling evidence for the presence of even heavier third-peak (A≈195) r-process elements (e.g., gold, platinum) or translead nuclei remains elusive. At early times (∼days) most of the r-process heating arises from a large statistical ensemble of β decays, which thermalize efficiently while the ejecta is still dense, generating a heating rate that is reasonably approximated by a single power law. However, at later times of weeks to months, the decay energy input can also possibly be dominated by a discrete number of α decays, 223Ra (half-life t1/2=11.43  d), 225Ac (t1/2=10.0  d, following the β decay of 225Ra with t1/2=14.9  d), and the fissioning isotope 254Cf (t1/2=60.5  d), which liberate more energy per decay and thermalize with greater efficiency than β-decay products. Late-time nebular observations of kilonovae which constrain the radioactive power provide the potential to identify signatures of these individual isotopes, thus confirming the production of heavy nuclei. In order to constrain the bolometric light to the required accuracy, multiepoch and wideband observations are required with sensitive instruments like the James Webb Space Telescope. In addition, by comparing the nuclear heating rate obtained with an abundance distribution that follows the solar r abundance pattern, to the bolometric lightcurve of AT2017gfo, we find that the yet-uncertain r abundance of 72Ge plays a decisive role in powering the lightcurve, if one assumes that GW170817 has produced a full range of the solar r abundances down to mass number A∼70. [ABSTRACT FROM AUTHOR]

Purpose: To compare the diagnostic accuracy of plasma aldosterone concentration (PAC), plasma renin activity (PRA) and aldosterone-to-renin ratio (ARR) in primary aldosteronism (PA) using radioimmunoassay (RIA) and chemiluminescence immunoassay (CLIA) methods. Methods: Both RIA and CLIA were used to analyze the PAC, PRA and ARR with subjects in standing or supine position, before and after a saline infusion test (SIT). The correlation between RIA and CLIA was measured by regression analysis. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic accuracy by RIA and CLIA. Results: A positive correlation was found between PAC and PRA after SIT using RIA and CLIA (0.1745 and 0.3085, respectively). A positive correlation was found between the PAC and PRA in standing and supine position using RIA and CLIA (0.3979 vs 0.2399 and 0.1885 vs 0.4032, respectively). There was no obvious difference in AUCs of PAC, PRA, and ARR between RIA and CLIA (PAC: 0.91 vs. 0.89; PRA: 0.88 vs. 0.87; ARR: 0.93 vs. 0.92). In standing posture, the AUCs of PAC, PRA and ARR using RIA were 0.63, 0.72 and 0.78, respectively, and the results of CLIA were 0.65, 0.75 and 0.82, respectively. In supine posture, the AUC of PAC, PRA and ARR using RIA was 0.65, 0.68 and 0.71, respectively, and the results of CLIA were 0.68, 0.70 and 0.79, respectively. Conclusion: Chemiluminescent assay is reliable for diagnosis of PA when compared with radioimmunoassay. [ABSTRACT FROM AUTHOR]

One promising electromagnetic signature of compact object mergers are kilonovae: approximately isotropic radioactively powered transients that peak days to weeks post-merger. Key uncertainties in kilonova modeling include the emission profiles of the radioactive decay products—non-thermal -particles, -particles, fission fragments, and -rays—and the efficiency with which their kinetic energy is absorbed by the ejecta. The radioactive energy emitted, along with its thermalization efficiency, sets the luminosity budget and is therefore crucial for predicting kilonova light curves. We outline uncertainties in the radioactivity, describe the processes by which the decay products transfer energy to the ejecta, and calculate time-dependent thermalization efficiencies for each particle type. We determine the net thermalization efficiency and explore its dependence on r-process yields—in particular, the production of -decaying translead nuclei—and on ejecta mass, velocity, and magnetic fields. We incorporate our results into detailed radiation transport simulations, and calculate updated kilonova light curve predictions. Thermalization effects reduce kilonova luminosities by a factor of roughly 2 at peak, and by an order of magnitude at later times (15 days or more after explosion). We present analytic fits to time-dependent thermalization efficiencies, which can be used to improve light curve models. We revisit the putative kilonova that accompanied gamma-ray burst 130603B, and estimate the mass ejected in that event. We find later time kilonova light curves can be significantly impacted by -decay from translead isotopes; data at these times may therefore be diagnostic of ejecta abundances. [ABSTRACT FROM AUTHOR]