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We study strong decays of the possible fully-charm tetraquarks recently observed by LHCb, and calculate their relative branching ratios through the Fierz rearrangement. Together with ...our previous QCD sum rule study, our results suggest that the broad structure around 6.2–6.8 GeV can be interpreted as an S-wave ccc¯c¯ tetraquark state with JPC=0++ or 2++, and the narrow structure around 6.9 GeV can be interpreted as a P-wave one with JPC=0-+ or 1-+. These structures were observed in the di-J/ψ invariant mass spectrum, and we propose to confirm them in the di-ηc,J/ψhc,ηcχc0, and ηcχc1 channels. We also propose to search for their partner states having the negative charge-conjugation parity in the J/ψηc,J/ψχc0,J/ψχc1, and ηchc channels.
In the framework of one-pion-exchange (OPE) model, we study the hidden-charm and charm-strange molecular pentaquark systems composed of a heavy baryon (Σc,Σc⁎) and a vector meson (K¯⁎,D¯⁎), where the ...S-D mixing effect is considered in our calculation. Our result shows that the ΣcD¯⁎ molecular state with (I=1/2,JP=3/2−) and the Σc⁎D¯⁎ molecular state with (I=1/2,JP=5/2−) exist in the mass range of the observed Pc(4380) and Pc(4450), respectively. Moreover, we predict two other hidden-charm molecular pentaquarks with configurations ΣcD¯⁎(I=3/2,JP=1/2−) and Σc⁎D¯⁎(I=3/2,JP=1/2−) and two charm-strange molecular pentaquarks Pcs(3340) and Pcs(3400) corresponding to the ΣcK¯⁎ configuration with (I=1/2,JP=3/2−) and the Σc⁎K¯⁎ configuration with (I=1/2,JP=5/2−), respectively. Additionally, we also predict some hidden-bottom Σb(⁎)B⁎ and Bc-like Σc(⁎)B⁎/Σb(⁎)D¯⁎ pentaquarks.
Target of rapamycin (TOR) is an evolutionarily conserved protein kinase that plays a central role in both plants and animals, despite their distinct developmental programs and survival strategies. ...Indeed, TOR integrates nutrient, energy, hormone, growth factor and environmental inputs to control proliferation, growth and metabolism in diverse multicellular organisms. Here, we compare the molecular composition, upstream regulators and downstream signaling relays of TOR complexes in plants and animals. We also explore and discuss the pivotal functions of TOR signaling in basic cellular processes, such as translation, cell division and stem/progenitor cell regulation during plant development.
PurposeExtreme support vector regression (ESVR) has been widely used in the design, analysis and optimization of engineering systems of its fast training speed and good computational ability. ...However, the ESVR model is only able to utilize one-fidelity information of engineering system. To solve this issue, this paper extends extreme support vector regression (ESVR) to a multi-fidelity surrogate (MFS) model which can make use of a few expensive but higher-fidelity (HF) samples and a lot of inaccurate but cheap low-fidelity (LF) samples, named ESVR-MFS.Design/methodology/approachIn the ESVR-MFS model, a kernel matrix is designed to evaluate the relationship between the HF and LF samples. The root mean square error of HF samples is used as the training error metric, and the optimal hyper-parameters of the kernel matrix are obtained through a heuristic algorithm.FindingsA number of numerical problems and three engineering problems are used to compare the ESVR-MFS model with the single-fidelity ESVR model and two benchmark MFS models. The results show that the ESVR-MFS model exhibits competitive performance in both numerical cases and practical cases tested in this work.Practical implicationsThe proposed approach exhibits great capability for practical multi-fidelity engineering design problems.Originality/valueA MFS model is proposed based on ESVR, which can make full use of the advantages of both HF data and LF data to achieve optimal results at same or lower cost.
Magnetic skyrmions have attracted considerable attention recently for their huge potential in spintronic applications. Generally skyrmions are big compared to the atomic lattice constant, which ...allows for the Ginzburg-Landau type description in the continuum limit. Such a description successfully captures the main experimental observations on skyrmions in B20 compound without inversion symmetry. Skyrmions can also exist in inversion-symmetric magnets with competing interactions. Here, we derive a general Ginzburg-Landau theory for skyrmions in these magnets valid in the long-wavelength limit. We study the unusual static and dynamical properties of skyrmions based on the derived Ginzburg-Landau theory. We show that an easy axis spin anisotropy is sufficient to stabilize a skyrmion lattice. Interestingly, the skyrmion in inversion-symmetric magnets has a new internal degree of freedom associated with the rotation of helicity, i.e., the "spin" of the skyrmion as a particle, in addition to the usual translational motion of skyrmions (orbital motion). The orbital and spin degree of freedoms of an individual skyrmion can couple to each other, and give rise to unusual behavior that is absent for the skyrmions stabilized by the Dzyaloshinskii-Moriya interaction. The derived Ginzburg-Landau theory provides a convenient and general framework to discuss skyrmion physics and will facilitate the search for skyrmions in inversion-symmetric magnets.
In this work, we systematically study the mass spectrum of the fully heavy tetraquark in an extended chromomagnetic model, which includes both color and chromomagnetic interactions. Numerical results ...indicate that the energy level is mainly determined by the color interaction, which favors the color-sextet |(QQ)6c (Q¯Q¯)6¯c ⟩ configuration over the color-triplet |(QQ)3¯c (Q¯Q¯)3c ⟩ one. The chromomagnetic interaction mixes the two color configurations and gives small splitting. The ground state is always dominated by the color-sextet configuration. We find no stable state below the lowest heavy quarkonium pair thresholds. Most states may be wide since they have at least one S-wave decay channel into two S-wave mesons. One possible narrow state is the 1+ bbb¯c¯ state with a mass 15719.1 MeV. It is just above the ηbB¯c threshold. But this channel is forbidden because of the conservation of the angular momentum and parity.
Skyrmions are disklike objects that typically form triangular crystals in two-dimensional systems. This situation is analogous to the so-called pancake vortices of quasi-two-dimensional ...superconductors. The way in which Skyrmion disks or "pancake Skyrmions" pile up in layered centrosymmetric materials is dictated by the interlayer exchange. Unbiased Monte Carlo simulations and simple stabilization arguments reveal face centered cubic and hexagonal close packed Skyrmion crystals for different choices of the interlayer exchange, in addition to the conventional triangular crystal of Skyrmion lines. Moreover, an inhomogeneous current induces a sliding motion of pancake Skyrmions, indicating that they behave as effective mesoscale particles.
Bayesian reliability assessment plays an integral role in determining the success of product development and deployment into the market, especially when limited information is available to estimate ...the reliability of products. Nevertheless, the Bayesian reliability approach has untapped research potential when it is used to evaluate systems consisting of dependent components, that is, a situation that reflects real‐world conditions. This study addresses the research gap by applying a copula to encode the dependency structure between the failure rates of the components, particularly for the simple series systems. Unfortunately, this study found that Bayesian aggregation error still occurs when information is used at different levels. By employing Monte Carlo simulation and classification tree learning, this study also investigates the key factors affecting such error over a wide range of possible scenarios and derives useful guidelines for reliability practitioners so that they can choose a more suitable analysis under certain circumstances.
Guest‐induced host–guest assembly in metal–organic frameworks (MOFs) has become a critical strategy to achieve circularly polarized luminescence (CPL). Herein, chiral metal–organic clusters (MOCs) ...induced CPL of achiral MOF are reported. Enantiopure titanium‐oxo clusters (R/S‐TOCs) are effectively loaded into the pores of a fluorescent, highly stable MOF NU‐901 thin film by using a liquid‐phase epitaxial layer‐by‐layer encapsulation method. The resulting chiral TOCs@NU‐901 MOF thin films exhibit strong chirality, intense photoluminescence, and excellent CPL performance with the highest dissymmetry factor (±0.025) reported so far for the downshifted MOF‐based materials. Further, the comparison experiments and density functional theory (DFT) calculations demonstrate that the excellent performance benefited from the strong chirality and charge transfer caused by the significant π–π interactions between the host (MOF) and guest (R/S‐TOCs). This novel chiral MOCs induced approach provides a powerful toolbox for new host–guest CPL thin film materials.
Novel chiral guests‐induced metal–organic framework (MOF) thin films by liquid‐phase epitaxial layer‐by‐layer encapsulation strategy for high circularly polarized luminescence (CPL) are reported. Thanks to the chirality and charge transfers caused by the significant π–π interactions in the host–guest combination, the resulting host–guest MOF thin film exhibits excellent CPL with the highest glum (±0.025) among the downshifted MOFs‐based materials.
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