Strong Transition Research Articles

New results on the decay spectroscopy of 254No with GABRIELA@SHELS

The structure of the nucleus has been studied for more than 20 years: the last publications on its decay spectroscopy are from LBNL [1], GSI [2], JYFL [3] and ANL [4]. Four decay schemes featuring two isomers have been published and are interpreted differently in terms of excitation energy and decay scheme of the 2 nd isomer and configuration assignments of both K-isomers. These discrepancies have triggered new experiments including this one, performed with the GABRIELA [5, 6] array, at the focal plane of the SHELS [7] separator at the FLNR, Dubna. The first part of this proceeding will present the experimental setup and the analysis techniques used to reveal the electromagnetic decay of the known isomers in 254No. The second part will focus on the new results obtained with more than 1 million 254No nuclei implanted in the focal plane detector. In particular, the internal conversion electron spectrum observed in the decay of the 8− K-isomer has revealed the presence of a strong transition, most likely E0, suggesting low-lying shape coexistence in this nucleus as predicted in [8, 9]. The γ-ray spectrum obtained from the decay of the short-lived 170 μs isomer has revealed new γ-ray lines putting in doubt the previous interpretations about this isomer decay.

Temperature control characteristics of intelligent cooling system for high-speed marine diesel engine

ABSTRACT To improve energy conservation and reduce emissions of an engine, this study applies intelligent thermal management to a cooling system. With a marine high-speed diesel engine as the research object, an intelligent cooling system based on controllable cooling components was developed. A variable-universe fuzzy control algorithm is designed to control an electronic thermostat, and a ‘T–S fuzzy control + BP-PID’ control algorithm is proposed to control standard electric drive pumps. The experimental results indicate that the intelligent cooling system considerably reduces the warm-up time, achieves accurate cooling, and effectively inhibits the hot immersion phenomenon. The intelligent control algorithm has control characteristics such as rapid response, strong adaptive ability, small overshoot, smooth transition, and high precision. The intelligent cooling system reduced the cooling-system power consumption by 5.52%–57.93%, fuel consumption rate by 1.43%–5.15%, smoke emission by 1.40%–4.69%, CO emission by 2.14%–6.03%, and HC emission by 7.41%–12.26%.

Photoluminescence and solid-state LED application based on pH-sensitive carbon quantum dots

Carbon quantum dots (CQDs) have attracted great interest on account of their outstanding physicochemical properties. Herein we study the optical properties of the CQDs (diamond structure) and observe interesting phenomenon of concurrent multiband luminescence across the whole visible region. What is more, the CQDs exhibit emission-dependent excitation and high pH-sensitive. The surface structural and luminescence investigation in conjunction with density functional theory calculation reveal that C(O)O, C(O)NH2, and C(O)OH-related surface defects in these CQDs lead to observed luminescence. The calculation shows that stronger transitions between band edges of C(O)NH2-terminated CQDs leads to relatively strong photoluminescence in strong contrast with usually weak emission in oxygen terminated CQDs. Finally, the solid-state LED devices with different emission colors were fabricated based on the pH-sensitive properties of the CQDs.

BaSn0.96-XZr0.04MXO3 (M = Mn, Fe or Co, x = 0, 0.02) for spin-based devices: Ferromagnetic properties

In this study, Zr and/or Mn, Fe or Co ions were used to induce a robust room temperature ferromagnetic nature in perovskite BaSnO3 for high performance information applications. Dilute magnetic semiconductor compositions with formula of BaSn0.96-XZr0.04MXO3 (M = Mn, Fe, Co, x = 0, 0.02) have been synthesized at 1150 °C. For all compositions, mono-phase of cubic BaSnO3 structure with very small impurities of SnO2 were recorded based on X-ray diffraction analysis. The relation between ionic size of dopants and crystal dimension of BaSnO3 suggests the of Sn4+-site by Zr4+, Mn2+, Fe2+ or Co2+ ions. Extended absorption tails to visible light region were found for BaSn0.94Zr0.04Mn0.02O3 and BaSn0.94Zr0.04Co0.02O3 samples, owing to strong defect band transition absorption. Due to the addition of Zr and/or Mn, Fe or Co ions high refine of BaSnO3 morphology from inhomogeneous large grains to well distribute small one were seen. The XPS results of BaSn0.96Zr0.04O3 and BaSn0.94Zr0.04Co0.02O3 samples confirm that Ba, Sn, O and Zr are in the oxidation states of +II, +IV, −II and +IV/+III, respectively. Magnetically, incorporation of 4 wt% Zr4+ ions (empty 4d-orbital) induced a full-saturated spin ferromagnetic order with saturation magnetization of 1.16 emu/g, retentivity of 0.11 emu/g and coercivity of 147 Oe. Also, codoping by Zr/Co ions stimulates a full-saturated spin ferromagnetic order with saturation magnetization of 1.36 emu/g, retentivity of 0.17 emu/g and coercivity of 149 Oe. The empty 4d-Zr4+ ions have high ability in reversing the diamagnetic nature of BaSnO3 to ferromagnetic one through interaction with oxygen vacancies. The outer 4d-shell of Zr and 3d-orbital of Co with the oxygen vacancies induce the strong magnetic exchange interaction. Through looking into the previous studies on the magnetic properties of BaSnO3, the recorded saturation magnetization of 4 wt% Zr and 4 wt% Zr + 2 wt% Co ions are remarkable values.

Reflective color filters based on SiO2/Cu multilayer stacks

Due to strong inter-band transitions, the optical response of copper exhibits a high light absorbance in the visible region of the spectrum, recovering blue wavelengths and reflecting a reddish color. In this contribution, copper is split into subwavelength thin films, which are separated by silicon dioxide dielectric layers to take advantage of photonic bandgaps, which subtract bands from the reflected light and, thus, give rise to a wide range of reflective colors, including blue. Using numerical simulations, we investigate the photonic bandgaps of SiO2/Cu stacks, enabled by Fabry–Pérot transmission resonances, which demonstrate the color tunability of these structures.

Microstructure evolution and mechanical properties of directionally solidified Al0.5CoCr1.3FeNi1.3(Ti, Si, B, C)0.3 multiphase complex concentrated alloy

Microstructure evolution and mechanical properties of Al0.5CoCr1.3FeNi1.3(Ti, Si, B, C)0.3 multiphase complex concentrated alloy (CCA) prepared by directional solidification combined with quenching during solidification (QDS) technique were studied. The directionally solidified (DS) samples were prepared at constant growth rates V ranging from 2.78 × 10−6 to 5.56 × 10−5 m/s, the constant temperature gradient in liquid at the solid-liquid interface of GL = 16.5 × 103 °C/m and then quenched at a cooling rate of about 50 °C/s. The solidification of the studied CCA begins with the growth of columnar FCC(A1) dendrites and is finalised by the formation of a multiphase microstructure in the interdendritic region. The DS samples subjected to isothermal annealing at 900 °C for 25 h show a strong brittle-ductile transition (BDT) behaviour characterised by brittle-ductile transition temperature (BDTT) between 650 and 700 °C at a strain rate of 1 × 10−4 s−1. The tensile deformation curves show only a strain hardening stage at test temperatures up to 650 °C. At temperatures ranging from 750 to 900 °C, the alloy shows anomalous strain hardening behaviour characterised by one strain hardening stage and three well-distinguished strain softening stages.

The Impact of Rural Location on Farmers’ Livelihood in the Loess Plateau: Local, Urban–Rural, and Interconnected Multi-Spatial Perspective Research

With the strengthening of regional and urban–rural interactions, farmers’ livelihood activities are becoming increasingly complex, and environmental factors that influence farmers’ livelihoods have multi-spatial effects. Consequently, comprehending farmers’ livelihoods from a multi-spatial perspective is imperative. Based on surveys conducted in 65 villages and 451 households in Jia County on the Loess Plateau, China, rural locations were deconstructed into natural, traffic, and positional advantages to explore the relationships and mechanisms between the rural environment and farmers’ livelihood stability from local, urban–rural, and interconnected multi-spatial perspectives. We found that 77% of the villages achieved a moderate or high Rural Location Advantage Index (RLAI) rating; 45% still lack natural advantages and are mainly located in hilly and sandy areas because of the fragile ecological environment of the Loess Plateau. Additionally, the Livelihood Stability Index (LSI) was moderate overall, but with significant spatial heterogeneity, and 72% of farmers possess strong transition capacity and have shifted away from relying on monoculture as their primary livelihood strategy. While a certain coupling correspondence exists between the LSI and RLAI, the interaction is intricate rather than a simple linear agglomeration process. The spatial variation in the LSI results from the superposition or interaction of multi-spatial location factors. The rural–urban spatial location factors are the key control element of the LSI and the interaction between rural–urban and local spatial location factors has the greatest influence on the LSI. It is simple for interconnected spatial location factors to produce a scale correlation effect, and have non-negligible effects on farmers’ livelihoods when they interact with other spatial location factors. Understanding the impact of rural location on farmers’ livelihood from a multi-spatial perspective is of great practical significance for identifying the causes of spatial heterogeneity in livelihoods and enhancing multi-level policy coordination on rural revitalization and livelihood security.

Nu Electroweak baryogenesis: the scalar singlet strikes back

We perform a comprehensive scan of the parameter space of a general singlet scalar extension of the Standard Model to identify the regions which can lead to a strong first-order phase transition, as required by the electroweak baryogenesis mechanism. We find that taking into account bubble nucleation is a fundamental constraint on the parameter space and present a conservative and fast estimate for it so as to enable efficient parameter space scanning. The allowed regions turn out to be already significantly probed by constraints on the scalar mixing from Higgs signal strength measurements. We also consider the addition of new neutrino singlet fields with Yukawa couplings to both scalars and forming heavy (pseudo)-Dirac pairs, as in the linear or inverse Seesaw mechanisms for neutrino mass generation. We find that their inclusion does not alter the allowed parameter space from early universe phenomenology in a significant way. Conversely, there are allowed regions of the parameter space where the presence of the neutrino singlets would remarkably modify the collider phenomenology, yielding interesting new signatures in Higgs and singlet scalar decays.

Indications of octupole correlation in 84Sr

Excited states in the 84Sr nucleus were investigated via the 76Ge(12C,4n)84Sr reaction at a beam energy of 58 MeV. The de-excited γ-rays were detected using the Indian National Gamma Array (INGA) spectrometer at Inter-University Accelerator Center, New Delhi. Directional Correlation from Oriented (DCO) states ratio and the polarization asymmetry (Δ) measurements were done to confirm the spin-parity of the low-lying states. Eight new γ-ray transitions were placed in the level scheme of 84Sr. The systematic behaviour of energy staggering S(I) of the γ-band (Band 1 and Band 2) was compared with the γ-bands in the mass A ≈ 80 region and the nuclei of other mass regions with similar behaviour (odd-I down). The E1 character is confirmed for strong γ-ray transitions connecting Band 3 to the Yrast band. Comparison of new results such as B(E1)/B(E2) ratio, frequency ratio ω −/ω + and energy displacement ΔE in 84Sr with those of 72Se, 150Sm, 152Gd, 220Ra and 224Th nuclei suggests the presence of octupole correlations in 84Sr.

Symmetry Breaking and Cooperative Spin Crossover in a Hofmann-Type Coordination Polymer Based on Negatively Charged {FeII(μ2-[MII(CN)4])2}n2n- Layers (MII = Pd, Pt).

We report herein the synthesis and characterization of two unprecedented isomorphous spin-crossover two-dimensional coordination polymers of the Hofmann-type formulated {FeII(Hdpyan)2(μ2-[MII(CN)4])2}, with MII = Pd, Pt and Hdpyan is the in situ partially protonated form of 2,5-(dipyridin-4-yl)aniline (dpyan). The FeII is axially coordinated by the pyridine ring attached to the 2-position of the aniline ring, while it is equatorially surrounded by four [MII(CN)4]2- planar groups acting as trans μ2-bidentate ligands defining layers, which stack parallel to each other. The other pyridine group of Hdpyan, being protonated, remains peripheral but involved in a strong [MII-C≡N···Hpy+] hydrogen bond between alternate layers. This provokes a nearly 90° rotation of the plane defined by the [MII(CN)4]2- groups, with respect to the average plane defined by the layers, forcing the observed uncommon bridging mode and the accumulation of negative charge around each FeII, which is compensated by the axial [Hdpyan]+ ligands. According to the magnetic and calorimetric data, both compounds undergo a strong cooperative spin transition featuring a 10-12 K wide hysteresis loop centered at 220 (Pt) and 211 K (Pd) accompanied by large entropy variations, 97.4 (Pt) and 102.9 (Pd) J/K mol. The breaking symmetry involving almost 90° rotation of one of the two coordinated pyridines together with the large unit-cell volume change per FeII (ca. 50 Å3), and subsequent release of significantly short interlayer contacts upon the low-spin → high-spin event, accounts for the strong cooperativity.

Broadband ptychography using curved wavefront illumination.

We examine the interplay between spectral bandwidth and illumination curvature in ptychography. By tailoring the divergence of the illumination, broader spectral bandwidths can be tolerated without requiring algorithmic modifications to the forward model. In particular, a strong wavefront curvature transitions a far-field diffraction geometry to an effectively near-field one, which is less affected by temporal coherence effects. The relaxed temporal coherence requirements allow for leveraging wider spectral bandwidths and larger illumination spots. Our findings open up new avenues towards utilizing pink and broadband beams for increased flux and throughput at both synchrotron facilities and lab-scale beamlines.

Cerium Features in Kilonova Near-infrared Spectra: Implication from a Chemically Peculiar Star

Observations of the kilonova from the neutron star merger event GW170817 opened a way to study r-process nucleosynthesis directly using neutron star mergers. It is, however, challenging to identify individual elements in kilonova spectra due to a lack of complete atomic data, in particular at near-infrared (NIR) wavelengths. In this paper, we demonstrate that spectra of chemically peculiar stars with enhanced heavy-element abundances can provide us with an excellent astrophysical laboratory for kilonova spectra. We show that the photosphere of the late B-type, chemically peculiar star HR 465 has similar lanthanide abundances and ionization degrees with those in the line-forming region in a kilonova at ∼2.5 days after the merger. The NIR spectrum of HR 465 taken with Subaru/IRD indicates that Ce iii lines give the strongest absorption feature around 16000 Å and there are no other comparably strong transitions around these lines. The Ce iii lines nicely match with the broad absorption feature at 14500 Å observed in GW170817 with a blueshift of v = 0.1 c, which supports recent identification of this feature as Ce iii by Domoto et al.

High-Order Harmonics Generation in Selenium-Containing Plasmas

The studies of the high-order harmonics generated in Se-containing plasmas are reported. The ablation of selenium in a vacuum allowed for the formation of a plasma demonstrating high-order harmonics generation and resonance enhancement of the harmonic at the shortest wavelength reported so far (λ ≈ 22.9 nm, Eph ≈ 54.14 eV). This harmonic corresponds to the 35th order of the 800-nm-class lasers. The influence of the presence of selenium in the molecular state (ZnSe and HgSe) on the suppression of the resonance effect during harmonics generation in plasma is studied. The enhanced 35th harmonic was analyzed by different methods of plasma formation using nanosecond, picosecond, and femtosecond pulses. The enhancement factor of the resonance-enhanced harmonic was measured to be 32× compared with the neighboring lower-order harmonics in the case of the picosecond-pulses-induced Se plasma. The role of the strong ionic transition of Se in the region of 22.7 nm in the observation of the resonance-induced enhancement of a single harmonic is discussed.

Multi-brane cosmology

5D warped extra dimension models with multiple 3-branes can naturally realize multiple hierarchical mass scales which are ubiquitous in physics beyond the Standard Model. We discuss cosmological consequences of such multi-brane models with stabilized radions. It is confirmed that for temperatures below the scale of the IR brane at the end of the extra dimension, we recover the ordinary expansion of the Universe, with the Hubble expansion rate determined by sum of the physical energy densities on all 3-branes where they are localized. In addition, we explore the cosmology for temperatures above the scales of the intermediate and IR branes where the Universe is described by a spacetime with the 3-branes replaced by an event horizon. As the temperature of the Universe cools down, phase transitions are expected to take place, and the intermediate and IR branes come out from behind the event horizon. The Goldberger-Wise mechanism for radion stabilization has a well-known problem of having a supercooled phase transition, which typically does not get completed in time. This problem is even more severe when an intermediate brane is introduced, whose scale is well above TeV, as the corresponding Hubble rate is much larger. We circumvent the problem by employing an alternative mechanism for radion stabilization with dark Yang-Mills fields, which prevents a long supercooling epoch, but still allows the strong first order phase transitions. As a result, the phase transitions in our multi-brane Universe predict a stochastic gravitational wave background with a unique multi-peak signature, which is within the sensitivity reach of future space-based gravitational wave observers. We also show that there are N − 1 radions for an N 3-brane set-up, unlike a recent claim that there exists only one radion.

Phase transition of the two Higgs doublets in early universe

In this paper, we study the phase transition of the two Higgs-doublets model (2HDM) and consider a scenario of a electroweak phase transition at alignment limit. Using the Cornwall–Jackiw–Tomboulis formalism at finite temperature, we consider the phase transition of the aligned 2HDM in the two-loop double-bubble contribution. By requirement of Goldstone theorem, the effective potential is corrected and the results show that the system obeys a second-order phase transition. A possible thermal history of the early universe has been treated out: the universe undergoes a smooth crossover in the SM, a second-order phase transition in this model before going to a strong first-order transition in the new physics as in recent 2HDMs and supersymmetry (from the EW symmetric to the broken phase).

Detectability of a phase transition in neutron star matter with third-generation gravitational wave interferometers

ABSTRACT Possible strong first-order hadron-quark phase transitions in neutron star interiors leave an imprint on gravitational waves, which could be detected with planned third-generation interferometers. Given a signal from the late inspiral of a binary neutron star (BNS) coalescence, assessing the presence of such a phase transition depends on the precision that can be attained in the determination of the tidal deformability parameter, as well as on the model used to describe the hybrid star equation of state. For the latter, we employ here a phenomenological meta-modelling of the equation of state that largely spans the parameter space associated with both the low-density phase and the quark high density compatible with current constraints. We show that with a network of third-generation detectors, a single loud BNS event might be sufficient to infer the presence of a phase transition at low baryon densities with an average Bayes factor B ≈ 100, up to a luminosity distance ($\mathcal {D}_\mathrm{ L} \lesssim$ 300 Mpc).

Comparison of different Gaussian quadrature rules for lattice Boltzmann simulations of noncontinuum Couette flows: From the slip to free molecular flow regimes

The lattice Boltzmann (LB) method can be formulated directly from the Boltzmann equation with the Bhatnagar–Gross–Krook assumption. This kinetic origin stimulates wide interest in applying it to simulate flow problems beyond the continuum limit. In this article, such a thought is examined by simulating Couette flows from the slip to free molecular flow regimes using the LB models equipped with different discrete velocity spaces, derived from the half-range Gauss Hermite (HGH), Gauss Legendre (GL), Gauss Kronrod (GK), and Gauss Chebyshev first and second quadrature rules. It is found that the conventional HGH-based LB models well describe noncontinuum Couette flows in the slip and weak transition flow regimes. Nonetheless, they suffer from significant errors with the further increasing Knudsen number, even if a large number of discrete velocities have been employed. Their results contrast with those by the LB models derived from the other Gaussian quadrature rules, which have far better accuracy at large Knudsen numbers. In particular, the GL- and GK-based LB models well capture the velocity fields of Couette flows in the strong transition and free molecular flow regimes. These numerical simulations in this article highlight the importance of velocity discretization for the LB simulations at different Knudsen numbers. They reveal that the LB models based on the Gauss Hermite (GH) quadrature rule are not always the best choice for simulating low-speed bounded flows at moderate and large Knudsen numbers; under strong noncontinuum conditions, those non-GH-based LB models proposed in this article have yielded more accurate results.

Alternative practices to pesticide use in the Guadeloupe banana belt: Do biophysical constraints limit agroecological transitions?

CONTEXTIn the French West Indies, the banana sector has made a transition from systems heavily reliant on synthetic inputs to more agroecological systems. However, despite abundant literature on the performance of these systems, few studies have described the mechanisms involved in this transition at the level of individual farms. OBJECTIVEThis article aims to understand the drivers of diverse individual agroecological transitions on banana farms in Guadeloupe towards alternative practices to the use of pesticides with a specific focus on the role of biophysical constraints at territorial scale. METHODThe methodological approach was based on three complementary steps to grasp the spatio-temporal determinants of these transitions: (1) a mapping of biophysical constraints on the scale of a territory spanning 2510 ha of farmland, (2) a mapping of the land use changes between 2010 and 2019 at the plot scale over 1680 plots, and (3) an evaluation of the agroecological transition over ten years of 20 farms located in four previously determined constraint zones. RESULTS AND CONCLUSIONSWe show that some farms in the study area face multiple constraints linked to biophysical factors (sigatoka pressure and slope), and that there are links between these various constraints and land use changes (e.g. abandonment, diversification and maintenance of banana production). A more detailed analysis of the farms shows the emergence of five transition types over the last ten years: farms with a weak transition, farms with a weak transition despite having governance over their productive resources, farms with a moderate transition, farms with an organic-based agroecological transitions, and farms with a strong agroecological transition. The biophysical constraints of these farms affected these transitions, however changes in legislation or access to organic certification also supported changes. There is room for progress to intensify the transition of these systems, but this requires specific recommendations for these different types. SIGNIFICANCEThe mixed method used in this study is helpful to diagnose changes in time and space of farms in agroecological transition and assess their real room for maneuver.

Differential Shannon Entropies Characterizing Electron-Nuclear Dynamics and Correlation: Momentum-Space Versus Coordinate-Space Wave Packet Motion.

We calculate differential Shannon entropies derived from time-dependent coordinate-space and momentum-space probability densities. This is performed for a prototype system of a coupled electron-nuclear motion. Two situations are considered, where one is a Born-Oppenheimer adiabatic dynamics, and the other is a diabatic motion involving strong non-adiabatic transitions. The information about coordinate- and momentum-space dynamics derived from the total and single-particle entropies is discussed and interpreted with the help of analytical models. From the entropies, we derive mutual information, which is a measure for the electron-nuclear correlation. In the adiabatic case, it is found that such correlations are manifested differently in coordinate- and momentum space. For the diabatic dynamics, we show that it is possible to decompose the entropies into state-specific contributions.

Giant Bulk Electrophotovoltaic Effect in Heteronodal-Line Systems.

The realization of a giant and continuously tunable second-order photocurrent is desired for many nonlinear optical (NLO) and optoelectronic applications, which remains a great challenge. Here, based on a two-band model, we propose a concept of the bulk electrophotovoltaic effect, that is, an out-of-plane external electric field (E_{ext}) that can continuously tune in-plane shift current along with its sign flip in a heteronodal-line (HNL) system. While strong linear optical transition around the nodal loop may potentially generate giant shift current, an E_{ext} can effectively control the radius of the nodal loop, which can continuously modulate the shift-vector components inside and outside the nodal loop holding opposite signs. This concept has been demonstrated in the HNL HSnN/MoS_{2} system using first-principles calculations. The HSnN/MoS_{2} heterobilayer can not only produce a shift-current conductivity with magnitude that is one to two orders larger than other reported systems, but it can also realize a giant bulk electrophotovoltaic effect. Our finding opens new routes to create and manipulate NLO responses in 2D materials.