Double Nuclei Research Articles

Role of spin-orbit strength in the prediction of closed shells in superheavy nuclei

Using the microscopic-macroscopic approach based on the modified two-center shell model, the ground-state shell corrections are analyzed as a function of spin-orbit strength for even-$Z$ superheavy nuclei in the $\ensuremath{\alpha}$-decay chains containing $^{295--300,302,304}120$ nuclei. The influence of the spin-orbit strength on the positions of shell closures and the description of the low-lying one-quasiparticle spectra for $^{251}\mathrm{Cf}, ^{243}\mathrm{Cm}, ^{243}\mathrm{Bk}$, and $^{251}\mathrm{Es}$ nuclei are studied in detail. The importance of studying the nuclear structure of actinides for predicting the next double magic nucleus beyond $^{208}\mathrm{Pb}$ is demonstrated.

Development of the laser isotope separation method to study for the neutrino-less double beta decay of 48Ca

Search for the ultra-rare process, neutrino-less double beta decay, is a powerful tool to test the Majorana nature of neutrinos. Among the potential double beta decay nuclei, 48Ca has the largest Q-value, hence we can expect the measurement with least background. On the other hand, due to its low natural abundance, isotope enrichment is essential to achieve the sensitivity in the region of interest (inverted/normal mass hierarchy of neutrinos).We have been developing a laser isotope separation method using a tunable semiconductor laser that can excite only a specific isotope (48Ca). The laser is irradiated perpendicular to the collimated calcium vapor beam. Only 48Ca atoms are separated by deflecting them from the original atomic beam by momentum transfer due to multiple absorption and emission of laser photons. The isotope separation is confirmed by irradiating an ionization laser and time-of-flight measurement.Following the success of the proof-of-principle experiment, we are now developing the mass production system which include efficient generation of atomic beams, frequency-stabilized high-power laser, efficient laser irradiation method, and collection method of deflected isotope beams. In this paper, we report on the status and prospects of these developments.

Photometry and Kinematics of Self-gravitating Eccentric Nuclear Disks

Abstract The Andromeda galaxy hosts an elongated nucleus with (at least) two distinct brightness peaks. The double nucleus can be explained by the projection of a thick, apsidally aligned eccentric nuclear disk of stars in orbit about the central black hole. Several nearby early-type galaxies have similar asymmetric nuclear features, indicating the possible presence of eccentric nuclear disks. We create simulated photometric (surface density) and kinematic (line-of-sight velocity) maps of eccentric nuclear disks using N-body simulations. We image our simulations from various lines of sight in order to classify them as double nuclei, offset nuclei, and centered nuclei. We explore the effects of mass segregation on the photometric maps, finding that heavier stars are concentrated in the brighter peak. The average line-of-sight velocity values are lower in an eccentric nuclear disk than for a circular ring about the supermassive black hole. The velocity dispersion values are higher and peak at the position of the supermassive black hole, which does not typically match the peak in photometry.

Role of acuK in Control of Iron Acquisition and Gluconeogenesis in Talaromyces marneffei.

Talaromyces marneffei is a dimorphic pathogenic fungus causing opportunistic infection in immunocompromised patients. It is a facultative intracellular pathogen and is usually found inside the host macrophages during infection. Alternative carbons and iron are the important nutrients associated with intracellular survival and pathogenesis of T. marneffei. This study reported the importance of the transcription factor AcuK in control of gluconeogenesis and iron acquisition in T. marneffei. Deletion of acuK gene in T. marneffei resulted in retardation of growth and germination in both mold and yeast phases. Microscopically, ΔacuK showed double nuclei hyphae. However, the yeast cells showed normal morphology. The ΔacuK failed to grow in iron-limiting conditions. Additionally, it could not grow in a medium containing gluconeogenic carbon sources. Moreover, ΔacuK showed higher susceptibility to macrophage killing than the wild type. These results demonstrated that AcuK controlled both iron acquisition and gluconeogenesis, and it could contribute to the pathogenicity of this fungus.

Chemical Composition of Outbursting Comet C/2015 ER61 (PanSTARRS)

Abstract Comet C/2015 ER61 (PanSTARRS) is a long-period Oort cloud comet whose favorable approach to the inner parts of the solar system in 2017 April–May enabled us to characterize its primary volatile composition using the iSHELL spectrograph mounted on the 3 m NASA Infrared Telescope Facility (IRTF) on Maunakea, Hawaii. We used three iSHELL settings (covering ∼2.8–5.2 μm) to sample fluorescent emissions from H 2 O, OH, CH 3 OH, HCN, C 2 H 2 , NH 3 , CO, CH 4 , C 2 H 6 , H 2 CO, and OCS on multiple dates ranging from UT 2017 April 15 (shortly after its April 4 outburst) to May 13, nearly 30 days before the detection of its double nucleus. Our observations also offered the opportunity to obtain sensitive 3 σ upper limits for cyanoacetylene ( HC 3 N). We report rotational temperatures ( T rot ), production rates (Qs), abundance (mixing) ratios (relative to H 2 O and C 2 H 6 ), and spatial distributions in the coma. ER61 exhibits variability in production rates of many species on short (day-to-day) and long (pre- versus post-perihelion) timescales. The relative abundances of these volatile species remained consistent within uncertainties during our pre-perihelion observations but tended to decrease during our post-perihelion observations (with the exception of CH 3 OH and HCN). The short-timescale variability in the production rates of these volatiles could be due to diurnal effects (over the course of the rotation of the nucleus) and/or the effect of its outburst. The decrease in the production rates and hence the mixing ratios in some volatiles in post-perihelion dates could be due to the presence of seasonal effects in ER61.

Shaping the archipelago of stability by the competition of proton and neutron shell closures

The evolution of superheavy nuclei in proton and neutron number is explored by investigating the ground-state shell correction energy in the $Z=112\text{--}126$ and $N=170\text{--}190$ region of the $(Z,N)$ plane. Cuts through the $(Z,N)$-dependent distribution of shell corrections are chosen for constant neutron-proton differences as accessible in $\ensuremath{\alpha}$-decay chains and varying the neutron number at fixed charge number. A new approach is used, integrating elements of energy-density functional theory into the microscopic-macroscopic method. The topology of the shell correction implies for binding energies a distribution resembling in shape a ridge on a coral reef, formed by the competition of proton and neutron shell closures at $Z=114$ and $Z=120$, and $N=174$ and $N=184$, respectively. $^{288}\mathrm{Fl}$ is predicted as the next double magic nucleus after $^{208}\mathrm{Pb}$, and $^{304}120$ is identified as the most likely candidate for next-to-next double magic nucleus.

New results on nuclear magicity and possible extension of the nuclear landscape

In nuclear theory, there is always a quest for possible extensions of the nuclear landscape and extending our knowledge to the limits of nuclear existence. In this study, we examine the stability and structural properties of a wide range of nuclei in super- and ultra-heavy region in a phenomenological semi-microscopic approach. we calculated the shell correlation energy, residual pairing correction energy, two-nucleon separation energy and two-nucleon energy gap for 3670 even–even nuclei along [Formula: see text]-stability line and two-neutron driplines in the ranges [Formula: see text] with [Formula: see text] and [Formula: see text] with [Formula: see text], respectively. To assure reliability and confidence of the new results in the ultra-heavy region, we extended the search space to include heavy and super-heavy nuclei. We report 83 double magic nuclei and address the predominance of proton and neutron magic numbers. Our calculations reproduced known results on nuclear magicity and present strong evidences on islands of stability and magic numbers in super- and ultra-heavy regions. We also address shifts in nuclear magicity along the nuclear landscape close to the [Formula: see text]-stability line and close to the neutron rich regions.

Observing the Time Evolution of the Multicomponent Nucleus of 3C 84

Abstract The advent of global millimeter-band very long baseline interferometry (VLBI) in recent years has finally revealed the morphology of the base of the two most prominent nearby, bright, extragalactic radio jets in M87 and 3C 84. The images are quite surprising considering the predictions of jet theory and current numerical modeling. The jet bases are extremely wide compared to expectations, and the nucleus of 3C 84 is very complicated. It appears as a double nucleus in 86 GHz observations with 50 μas resolution and a triple nucleus with 30 μas resolution with space-based VLBI by RadioAstron at 22 GHz. What is even odder is that the double and triple nuclei are arranged along an east–west line that is approximately orthogonal to the north–south large-scale jet on 150 μas−4 mas scales. We explore the emergence of an (east–west) double nucleus in the lower-resolution 43 GHz Very Long Baseline Array (VLBA) imaging from 2018 August to 2020 April. The double nucleus is marginally resolved. We exploit the east–west resolution associated with the longest baselines, ∼0.08 mas, to track a predominantly east–west separation speed of ≈0.086 ± 0.008c. We estimate that the observed mildly relativistic speed persists over a deprojected distance of ∼1900–9800 times the central, supermassive black hole gravitational radius (∼0.3–1.5 lt-yr) from the point of origin.

Legg-Calvé-Perthes’ disease. Congruent aspherity caused by physeal injury

IntroductionPerthes disease often produces a congruent nonspherical coxa. The most widely accepted cause is initial bone collapse, but some authors refer to physeal injury as the cause of this deformity. We analyze this elliptical process in cases of congruent nonspherical Perthes. MethodsRetrospective case-control study of 49 unilateral class III–IV Perthes cases that were not operated on. Results were compared with 49 healthy contralateral hips. The following radiological variables were determined both in AP and lateral projection, and at 4 points in time of the disease: ovalization index (OI), arthrotrochanteric distance, intraphysial angle, physeal narrowing, presence of double epiphyseal reosification nucleus, physeal length and Reimers index. ResultsThe initial OI was 1.7 in the early reosification phase and final OI was 2.07 at physeal closure. The OI in the control cases was invariably 1.4. There was a direct relation between a high index and the initial appearance of a double epiphyseal ossification nucleus, asymmetric physeal effacement and the increase of the intraphyseal angle in both radiographic projections. ConclusionsThe elliptical process of the femoral head occurs progressively throughout the disease and not only during bone collapse. It starts in the reosification phase and ends when growth stops. The initial risk signs found were the appearance of the double nucleus of reosification, the progressive angulation of the physis and the progressive increase in the rate of ovalization. Level of evidenceIII control cases.

Enfermedad de Legg-Calvé-Perthes. Estudio de la anesfericidad congruente causada por la lesión fisaria

IntroductionPerthes disease often produces a congruent nonspherical coxa. The most widely accepted cause is initial bone collapse, but some authors refer to physeal injury as the cause of this deformity. We analyze this elliptical process in cases of congruent nonspherical Perthes. MethodsRetrospective case-control study of 49 unilateral class III-IV Perthes cases that were not operated on. Results were compared with 49 healthy contralateral hips. The following radiological variables were determined both in AP and lateral projection, and at 4 points in time of the disease: ovalization index (OI), arthrotrochanteric distance, intraphysial angle, physeal narrowing, presence of double epiphyseal reosification nucleus, physeal length and Reimers index. ResultsThe initial OI was 1.7 in the early reosification phase and final OI was 2.07 at physeal closure. The OI in the control cases was invariably 1.4. There was a direct relation between a high index and the initial appearance of a double epiphyseal ossification nucleus, asymmetric physeal effacement and the increase of the intraphyseal angle in both radiographic projections. ConclusionsThe elliptical process of the femoral head occurs progressively throughout the disease and not only during bone collapse. It starts in the reosification phase and ends when growth stops. The initial risk signs found were the appearance of the double nucleus of reosification, the progressive angulation of the physis and the progressive increase in the rate of ovalization.

Systematic study of α decay half-lives within the Generalized Liquid Drop Model with various versions of proximity energies * *Support by National Natural Science Foundation of China (10775061, 11175054, 11675066, 11665019, 11947229), the Fundamental Research Funds for the Central Universities (lzujbky-2017-ot04, lzujbky-2020-it01), and Feitian Scholar Project of Gansu province

It is universally acknowledged that the Generalized Liquid Drop Model (GLDM) has two advantages over other α decay theoretical models: introduction of the quasimolecular shape mechanism and proximity energy. In the past few decades, the original proximity energy has been improved by numerous works. In the present work, the different improvements of proximity energy are examined when they are applied to the GLDM for enhancing the calculation accuracy and prediction ability of α decay half-lives for known and unsynthesized superheavy nuclei. The calculations of α half-lives have systematic improvements in reproducing experimental data after choosing a more suitable proximity energy for application to the GLDM. Encouraged by this, the α decay half-lives of even-even superheavy nuclei with Z=112-122 are predicted by the GLDM with a more suitable proximity energy. The predictions are consistent with calculations by the improved Royer formula and the universal decay law. In addition, the features of the predicted α decay half-lives imply that the next double magic nucleus after 208Pb is 298Fl.

The MOSDEF survey: differences in SFR and metallicity for morphologically selected mergers at z ∼ 2

ABSTRACT We study the properties of 55 morphologically-identified merging galaxy systems at z ∼ 2. These systems are flagged as mergers based on features such as tidal tails, double nuclei, and asymmetry. Our sample is drawn from the MOSFIRE Deep Evolution Field (MOSDEF) survey, along with a control sample of isolated galaxies at the same redshift. We consider the relationships between stellar mass, star formation rate (SFR), and gas-phase metallicity for both merging and non-merging systems. In the local universe, merging systems are characterized by an elevated SFR and depressed metallicity compared to isolated systems at a given mass. Our results indicate SFR enhancement and metallicity deficit for merging systems relative to non-merging systems for a fixed stellar mass at z ∼ 2, though larger samples are required to establish these preliminary results with higher statistical significance. In future work, it will be important to establish if the enhanced SFR and depressed metallicity in high-redshift mergers deviate from the ‘fundamental metallicity relation,’ as is observed in mergers in the local universe, and therefore shed light on gas flows during galaxy interactions.

Dual AGN Candidates with Double-peaked [O iii] Lines Matching that of Confirmed Dual AGNs

Abstract We have performed a spectral decomposition to search for dual active galactic nuclei (DAGNs) in the Sloan Digital Sky Survey (SDSS) quasars with z < 0.25. Potential DAGN candidates are searched by referencing velocity offsets and spectral shapes of double-peaked [O iii] lines of known DAGNs. Out of 1271 SDSS quasars, we have identified 77 DAGN candidates. Optical and mid-infrared (MIR) diagnostic diagrams are used to investigate the ionizing source in the DAGN candidates. The optical diagnostic analysis suggests 93% of them are powered by AGNs, and MIR diagnostic analysis suggests 97% are powered by AGNs. About one-third of the SDSS images of the DAGN candidates show signs of tidal interaction, but we are unable to identify double nuclei in most of them due to the low spatial resolution of the archival imaging data available for most of the sample. The radio-loud fraction of the DAGN candidates (∼10%) is similar to that of typical AGNs.

Revisiting the Complex Nuclear Region of NGC 6240 with Chandra

Abstract We present a reanalysis of the cumulative ACIS-S Chandra data set pointed at the double active galactic nuclei (AGNs) of the NGC 6240 merging galaxy, focusing on the hard energy bands containing the hard spectral continuum (5.5–5.9 keV), the redshifted Fe i Kα line (6.0–6.4 keV), and the redshifted Fe xxv line (6.4–6.7 keV). We have used the full Chandra telescope angular resolution and modeled the Chandra point-spread function (PSF) by comparing a preflight calibration model to the data for the two bright AGNs. With two complementary approaches—(1) studying the residuals after PSF subtraction and (2) producing reconstructed Expectation through Markov Chain Monte Carlo (EMC2) images—we are able to resolve structures extending from ∼1 kpc to <200 pc in the S AGN. The latter are within the sphere of influence of this BH. We find significant extended emission in both continuum and Fe lines in the ∼2″ (∼1 kpc) region surrounding the nuclei, in the region between the N and S AGN, and in a sector of PA 120–210 deg. extending to the SE from the centroid of the S AGN surface brightness. The extended Fe i Kα emission is likely to originate from the fluorescence of X-ray photons interacting with dense molecular clouds, providing a complementary view to recent high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) studies. The nonthermal emission is more prevalent in the region in between the two active X-ray nuclei and in the N AGN. We do not find strong evidence of X-ray emission associated with the third nucleus recently proposed for NGC 6240.

Ellipsoidal process of the femoral head in Legg-Calvé-Perthes disease. Part I.

Legg-Calvé-Perthes disease (LCPD) often produces a residual deformity, typically consistent with coxa magna, coxa plana, and ellipsoidal shape. Depending on the degree of asphericity and flatness, this morphology was classified by Stulberg in stages III and IV. Thus far, few studies have investigated physeal injury as an etiological cause or evaluated its progressive profile throughout Waldenström's reossification stage and the remodelling stage. In this study, we analysed the ellipsoidal process of the femoral head. This was a retrospective control case study involving 83 unoperated hips with LCPD and Stulberg stages III and IV outcome. The data were compared with those obtained for 49 healthy contralateral hips (control). The Ellipsoidal Index, the presence of a double epiphyseal reossification nucleus, physeal narrowing, intraphyseal angle, epiphyseal height, diameter of the head, and Reimer's Index were determined. Measurements were performed at four-time points: the year the reossification stage was initiated, the final growth stage, and two equally spaced time points in between. The Ellipsoidal Index gradually increased throughout the course of the disease from 1.6 in the initial reossification stage to 2.0 at the end of growth. In the control cases, this value was consistently 1.4. More ellipsoidal deformity was observed in Stulberg stage IV versus Stulberg stage III patients (P < 0.05). Moreover, there was a direct link between a high Ellipsoidal Index and the appearance of a double reossification nucleus, a physeal narrowing in the area underlying the anterosuperior nucleus, intraphyseal angle. Reimer's Index showed a gradual extrusion from baseline to the end of growth (26.1 versus 31.8, respectively; P < 0.05). The ellipsoidal process of the femoral head occurs gradually throughout the reossification and remodelling stages. This was linked to the appearance of a double epiphyseal nucleus, gradual extrusion, an angulated physis appearance, an asymmetrical narrowing of the physis and a high Ellipsoidal Index, which may be indicative of poor prognosis. Levels of Evidence for Primary Research Question: Level III, case-control study.

Outburst and Splitting of Interstellar Comet 2I/Borisov

Abstract We present Hubble Space Telescope observations of a photometric outburst and splitting event in interstellar comet 2I/Borisov. The outburst, first reported with the comet outbound at ∼2.8 au, was caused by the expulsion of solid particles having a combined cross section ∼100 km2 and a mass in 0.1 mm sized particles ∼2 × 107 kg. The latter corresponds to ∼10−4 of the mass of the nucleus, taken as a sphere of radius 500 m. A transient “double nucleus” was observed on UT 2020 March 30 (about 3 weeks after the outburst), having a cross section ∼0.6 km2 and corresponding dust mass ∼105 kg. The secondary was absent in images taken on and before March 28 and in images taken on and after April 3. The unexpectedly delayed appearance and rapid disappearance of the secondary are consistent with an origin through rotational bursting of one or more large (meter-sized) boulders under the action of outgassing torques, following their ejection from the main nucleus. Overall, our observations reveal that the outburst and splitting of the nucleus are minor events involving a negligible fraction of the total mass: 2I/Borisov will survive its passage through the planetary region largely unscathed.

Temperature Dependence of the Symmetry Energy Components for Finite Nuclei

We investigate the temperature dependence of the volume and surface components of the nuclear symmetry energy (NSE) and their ratio in the framework of the local density approximation. The results of these quantities for finite nuclei are obtained within the coherent density fluctuation model (CDFM). The CDFM weight function is obtained using the temperature-dependent proton and neutron densities calculated through the HFBTHO code that solves the nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical transformed deformed harmonic-oscillator basis. We present and discuss the values of the volume and surface contributions to the NSE and their ratio obtained for the Ni, Sn, and Pb isotopic chains around double-magic 78Ni, 132Sn, and 208Pb nuclei. The results for the T-dependence of the considered quantities are compared with estimations made previously for zero temperature showing the behavior of the NSE components and their ratio, as well as with the available experimental data. The sensitivity of the results on various forms of the density dependence of the symmetry energy is studied. We confirm the existence of “kinks” of these quantities as functions of the mass number at T = 0 MeV for the double closed-shell nuclei 78Ni and 132Sn and the lack of “kinks” for the Pb isotopes, as well as the disappearance of these kinks as the temperature increases.

Ultradiffuse galaxies in the IC 1459 group from the VEGAS survey

ABSTRACT Using deep g, r, i imaging from the VST Early-type GAlaxy Survey (VEGAS), we have searched for ultradiffuse galaxies (UDGs) in the IC 1459 group. Assuming they are group members, we identify nine galaxies with physical sizes and surface brightnesses that match the UDG criteria within our measurement uncertainties. They have mean colours of g − i = 0.6 and stellar masses of ∼108 M⊙. Several galaxies appear to have associated systems of compact objects, e.g. globular clusters. Two UDGs contain a central bright nucleus, with a third UDG revealing a remarkable double nucleus. This appears to be the first reported detection of a double nucleus in a UDG – its origin is currently unclear.

An approximation to the Woods–Saxon potential based on a contact interaction

We study a non-relativistic particle subject to a three-dimensional spherical potential consisting of a finite well and a radial $\delta$-$\delta'$ contact interaction at the well edge. This contact potential is defined by appropriate matching conditions for the radial functions, thereby fixing a self adjoint extension of the non-singular Hamiltonian. Since this model admits exact solutions for the wave function, we are able to characterize and calculate the number of bound states. We also extend some well-known properties of certain spherically symmetric potentials and describe the resonances, defined as unstable quantum states. Based on the Woods-Saxon potential, this configuration is implemented as a first approximation for a mean-field nuclear model. The results derived are tested with experimental and numerical data in the double magic nuclei $^{132}$Sn and $^{208}$Pb with an extra neutron.

RILIS laser ion source development for ISOL systems at RISP

The Resonance Ionization Laser Ion Source (RILIS) system has been developed for the future on-line laser ion source for a new heavy ion accelerator, RAON, in Korea. A tunable laser system consisting of four Ti:Sapphire lasers pumped by a Nd:YAG laser has been set up for the application in the RILIS laser ion source development in the ISOL facility of the Rare Isotope Science Project (RISP)/IBS. As a milestone of extraction of rare isotopes produced through uranium fission, double magic nucleus of 132Sn is our first target. Three step resonance ionization schemes with four laser wavelengths, at 286 nm, 301 nm, 811 nm and 823 nm, have been investigated for Sn. In this paper, we present the recent results and the current status of the hot-cavity type laser ion source development in the off-line ion source test facility of RISP, including measurements of ionization efficiency and mass resolving power.