Folding State within a Hysteresis Loop: Hidden Multistability in Nonlinear Physical Systems.

Identifying hidden states in nonlinear physical systems that evade direct experimental detection is important as disturbances and noises can place the system in a hidden state with detrimental consequences. We study a cavity magnonic system whose main physics is photon and magnon Kerr effects. Sweeping a bifurcation parameter in numerical experiments (as would be done in actual experiments) leads to a hysteresis loop with two distinct stable steady states, but analytic calculation gives a third folded steady state "hidden" in the loop, which gives rise to the phenomenon of hidden multistability. We propose an experimentally feasible control method to drive the system into the folded hidden state. We demonstrate, through a ternary cavity magnonic system and a gene regulatory network, that such hidden multistability is in fact quite common. Our findings shed light on hidden dynamical states in nonlinear physical systems which are not directly observable but can present challenges and opportunities in applications.

Two-dimensional graphene+ as an anode material for calcium-ion batteries with ultra-high capacity: a first-principles study.

Multivalent-ion batteries have garnered significant attention due to their high energy density, low cost, and superior safety. Calcium-ion batteries (CIBs) are regarded as the next-generation energy storage systems for their abundant natural resources and bivalent characteristics. However, the absence of high-performance anode materials poses a significant obstacle to the progress of battery technology. Two-dimensional (2D) Dirac materials have excellent conductivity and abundant active sites, rendering them promising candidates as anode materials. A novel 2D Dirac material known as "graphene+" has been theoretically reported, exhibiting prominent properties including good stability, exceptional ductility, and remarkable electronic conductivity. By using first-principles calculations, we systematically investigate the performance of graphene+ as an anode material for CIBs. Graphene+ exhibits an ultra-high theoretical capacity (1487.7 mA h g-1), a small diffusion barrier (0.21 eV), and a low average open-circuit voltage (0.51 V). Furthermore, we investigate the impact of the electrolyte solvation on the performance of Ca-ion adsorption and migration. Upon contact with electrolyte solvents, graphene+ exhibits strong adsorption strength and rapid migration of Ca-ions on its surface. These results demonstrate the promising potential of graphene+ as a high-performance anode material for CIBs.

Strain-induced ferroelectric polarization reversal without undergoing geometric inversion in blue SiSe monolayer.

Ferroelectricity in two-dimensional (2D) systems generally arises from phonons and has been widely investigated. On the contrary, electronic ferroelectricity in 2D systems has been rarely studied. Using first-principles calculations, the ferroelectric behavior of the buckled blue SiSe monolayer under strain are explored. It is found that the direction of the out-of-plane ferroelectric polarization can be reversed by applying an in-plane strain. And such polarization switching is realized without undergoing geometric inversion. Besides, the strain-triggered polarization reversal emerges in both biaxial and uniaxial strain cases, indicating it is an intrinsic feature of such a system. Further analysis shows that the polarization switching is the result of the reversal of the magnitudes of the positive and negative charge center vectors. And the variation of buckling is found to play an important role, which results in the switch. Moreover, a non-monotonic variation of band gap with strain is revealed. Our findings throws light on the investigation of novel electronic ferroelectric systems.

Correction: Rich magnetic phase transitions and completely dual-spin polarization of zigzag PC3 nanoribbons under uniaxial strain.

Correction for 'Rich magnetic phase transitions and completely dual-spin polarization of zigzag PC3 nanoribbons under uniaxial strain' by Hui-Min Ni et al., Phys. Chem. Chem. Phys., 2023, https://doi.org/10.1039/d2cp05066h.

Rich magnetic phase transitions and completely dual-spin polarization of zigzag PC3 nanoribbons under uniaxial strain.

Among many modulation methods, strain engineering is often chosen for nanomaterials to produce tunable band gaps continuously. Inspired by the recently reported two-dimensional material PC3, we explore the tuning of strain on the spin-dependent transport properties of PC3 nanoribbons using the first-principle approach. Surprisingly, strain regulation achieves uninterrupted completely dual-spin polarization over a wide energy range near EF. Analysis reveals that the peculiar transmission spectra arise from the interesting evolution of the band structure, in which strain induces bands to shift and broaden/flatten. This results in triggering the transition of PC3NRs from bandgap-tunable bipolar magnetic semiconductors to spin-gapless semiconductors to ferromagnetic metals or half-metal magnets. Their unique performance demonstrates great potential in spintronics, and our study is expected to provide ideas and theoretical support for the design and application of novel PC3-based spintronic devices in the future.

Modulation of edge defects on dual-spin filtering in zigzag ß-SiC7 nanoribbons.

The unique edge states of the zigzag ß-SiC7 nanoribbons aroused our attention, and therefore, based on first-principles calculations, we investigated their spin-dependent electronic transport properties by constructing controllable defects to modulate these special edge states. Interestingly, by introducing rectangular edge defects in the SiSi and SiC edge-terminated systems, not only the spin-unpolarized is successfully converted to completely spin-polarized, but also the direction of polarization can be switched, thus enabling a dual spin filter. The analyses further reveal that the two transmission channels with opposite spins are spatially separated and that the transmission eigenstates are highly concentrated at the relative edges. The specific edge defect introduced only suppresses the transmission channel at the same edge but reserves the transmission channel at the other edge. In addition, for the CSi and CC edge-terminated systems, an additional spin-down band exists due to spin splitting in the spin-up band at EF, so that besides the original spatially separated two spin-opposite channels, an extra spin channel is distributed at the upper edge, resulting in unidirectional fully spin-polarized transport. The peculiar spatially separated edge states and excellent spin filtering properties could open up further possibilities for ß-SiC7-based electronic devices in spintronics applications.

Metallic-semiconducting transition and spin polarized-unpolarized transition in a single molecule with a negative Poisson's ratio.

Different from conventional materials, structures with a negative Poisson's ratio (NPR) contract/expand laterally under a longitudinal compressive/tensile strain, usually exhibiting peculiar features. Through first-principles calculations, we investigate the electronic and transport properties of Pd9B16 molecules. Its Poisson's ratio is found to be negative under uniaxial strain along a specific direction. By contacting with Au nanowires, atomic Au chains and atomic C chain electrodes, two kinds of transitions for transmission states could be realized by the modulation of the strain and the contacting site, i.e., metallic-semiconducting transition and spin polarized-unpolarized transition. Further analysis shows that it is the suppression and shifting of density of states, caused by the strain or contacting electrodes, that trigger the transitions. Those findings combine NPR and spintronics at the single-molecule level, which may throw light on the development of nanoelectronic devices.

Electrically modulated reversible dual-spin filter in zigzag ß-SiC7 nanoribbons.

Compared with traditional magnetic approaches, electrical modulation of spin-polarized current can greatly reduce the energy consumption and scale of nanodevices and improve their operating speed, which has become a promising research field in spintronics. Motivated by the latest reported novel two-dimensional material ß-SiC7, we employ first-principles calculations to investigate its spin-dependent electron transport with diverse edge configurations. By introducing a gate voltage, the three-terminal device can not only switch between spin-unpolarized and fully spin-polarized states, but also easily change the polarization direction, behaving as an excellent electrically modulated reversible dual-spin filter. Surprisingly, an arbitrary proportion of spin-up and spin-down electron numbers is achieved, enabling precise control of spin polarization. Analysis reveals that it is attributed to the peculiar transmission spectrum, where two broad peaks with opposite spins are located around the Fermi level and respond differently to gate voltage. They belong to the spatially separated edge states originating from the p orbitals of the edge atoms. This feature is robust to different edge configurations of ß-SiC7 nanoribbons, indicating that this may be an intrinsic property of such systems, showing great potential for applications.

Electrically controlled spin reversal and spin polarization of electronic transport in nanoporous graphene nanoribbons.

Based on first-principles calculations, the spin-dependent electronic transport of nanoporous graphene nanoribbons is investigated. A three-terminal configuration is proposed, which can electronically control the spin polarization of transmission, instead of magnetic methods. By modulating the gate voltage, not only could the transmission be switched between completely spin up and spin down polarized states to realize a dual-spin filter, but also the spin polarization could be finely tuned between 100% and -100%. Any ratio of spin up to spin down transport electrons can be realized, providing more possibilities for the design of nanoelectronic devices. Further analysis shows that the transmission spectra, with two distinct transmission peaks with opposite spins around EF, are the key point, which are contributed by p orbitals. And such a phenomenon is robust to the width and length of the nanoporous graphene nanoribbons, suggesting that it is an intrinsic feature of these systems. The electrical control on spin polarization is realized in pure-carbon systems, showing great application potential.

Electrically precise control of the spin polarization of electronic transport at the single-molecule level.

Compared with the conventional magnetic means (such as ferromagnetic contacts), controlling a spin current by electrical methods could largely reduce the energy consumption and dimensions of nano-devices, which has become a focus of research in spintronics. Inspired by recent progress in the synthesis of an iron-based metal-organic nanostructure, we investigate the spin-dependent electronic transport of the molecule of Fe3-terpyridine-phenyl-phenyl-terpyridine-Fe3 (Fe3-TPPT-Fe3) through first-principles calculations, and propose a three-terminal device without ferromagnetics. By applying a gate voltage, not only the spin polarization can be switched between 100% and -100% to achieve a dual-spin filter, but also its fine regulation can be realized, where the transmission with any ratio of spin-up to spin-down electron numbers is achievable. Analysis shows that the particular transmission spectra are the key mechanism, where two peaks reside discretely on both sides of the Fermi level with opposite spins. Such a feature is found to be robust to the number of Fe atoms and TPPT chain length, suggesting that it is an intrinsic feature of such systems and very conducive to practical applications. The electrical control (such as an electric field) of spin polarization is realized at the single-molecule level, showing great application potential.

Functional Analysis of Sheep POU2F3 Isoforms.

POU domain class 2 transcription factor 3 (POU2F3) plays an important role in keratinocyte proliferation and differentiation. Our previous study identified four sheep POU2F3 transcript variants (POU2F3-1, POU2F3-2, POU2F3-3, and POU2F3-4), encoding three POU2F3 protein isoforms (POU2F3-1, POU2F3-2, and POU2F3-3). However, the functional differences among the three POU2F3 isoforms remain unknown. The objective of this study was to determine the tissue expression pattern of the four POU2F3 transcript variants in sheep and to investigate the functional differences in cell proliferation among the three POU2F3 isoforms. Quantitative RT-PCR analysis showed that the four POU2F3 transcripts were ubiquitously expressed in all tested adult sheep tissues, and POU2F3-1 exhibited higher expression level than the other three POU2F3 transcript variants in skin (P < 0.05). Cell proliferation assay showed that overexpression of any one of the three POU2F3 isoforms significantly inhibited the proliferation of sheep fetal fibroblasts and HaCaT cells at 48 and 72 h after transfection (P < 0.05). POU2F3-3 had less inhibitory effect on cell proliferation than POU2F3-1 and POU2F3-2 (P < 0.05), and POU2F3-1 and POU2F3-2 had similar inhibitory effects (P > 0.05). Dual luciferase reporter assays demonstrated that overexpression of any one of the three POU2F3 isoforms significantly inhibited the promoter activities of keratin 14 (KRT14) and matrix metalloproteinase 19 (MMP19) genes (P < 0.05). POU2F3-3 had less inhibitory effect on the promoter activities of KRT14 and MMP19 genes than POU2F3-1 and POU2F3-2 (P < 0.05), and POU2F3-1 and POU2F3-2 had similar inhibitory effects (P > 0.05). These results suggest three sheep POU2F3 isoforms have similar functional effects, but to a different extent.

Associations among sleep symptoms, physical examination, and polysomnographic findings in children with obstructive sleep apnea.

PURPOSE: The relationships among PSG findings, OSA symptoms, and tonsil and adenoid size are not clear. In this study, we aimed to investigate the associations between pediatric OSA and tonsil and adenoid size using subjective (OSA-18 questionnaire) and objective (PSG) measurements. METHODS: 101 consecutive patients aged from 2 to 12 years (mean age, 5.4 ± 2.2 years; boys, 72.3%) diagnosed with OSA were enrolled in two age groups (2-6 years group and 7-12 years group) and underwent PSG and lateral cephalometric radiography. Tonsil size and the adenoid-nasopharyngeal (A/N) ratio were determined. Quality of life and sleep symptoms were measured using the Chinese version OSA-18 questionnaire. Demographic and clinical data were obtained. RESULTS: 75 and 26 patients were separately enrolled in 2-6 years group and 7-12 years group. In 2-6 years group, the multiple linear regression revealed that tonsil size and A/N ratio were associated with log apnea-hypopnea index (AHI), and the Spearman's rank correlation reflected a positive correlation between log AHI and the OSA-18 sleep disturbance score (r = 0.362, P = 0.001). Log OSA-18 score was correlated with tonsil size (r = 0.349, P = 0.002) but not the A/N ratio in 2-6 years group. Finally, no significant associations were observed between log OSA-18 scores and log AHI in all patients. CONCLUSION: As PSG stays the golden standard for diagnoses of pediatric OSA, physical examinations and quality-of-life assessments are needed to fully assess the impact of OSA on children.

Edge-modulated dual spin-filter effect in zigzag-shaped buckling Ag2S nanoribbons.

Unlike MoS2, single-layered Ag2S nanoribbons (Ag2SNRs) exhibit a nonmetal-shrouded and a zigzag-shaped buckling structure and possess two distinct edges, S- or Ag-terminated ones. By performing first principle calculations, the spin-dependent electron transport of Ag2SNRs in a ferromagnetic state has been investigated. It is found that the SS- and AgAg-terminated Ag2SNRs exhibit semi-metallic characteristics, but with opposite spin-polarized directions. And AgS-terminated ones show metallic characteristics, but with completely spin-unpolarized transmission. That is to say, all three states, i.e., spin up polarized, spin down polarized and spin unpolarized ones, could be achieved by modulating the edge geometry. Further analysis shows that, the spatial separation on edges of the energy states with different spins around EF is responsible for the switch in the three states. The system could operate as a dual spin-filter, and the direction of the spin polarization can be switched by the edge morphology. Furthermore, calculations show that such a phenomenon is robust to the width of the ribbon and strain, showing great application potential.

Peripheral blood immunological parameters of children with adenoid hypertrophy with otitis media with effusion: propensity score matching.

PURPOSE: To evaluate peripheral blood immunological parameters and the possible correlation with age, gender and adenoid size in children with adenoid hypertrophy with OME. METHODS: A total of 664 children with adenoid hypertrophy were initially enrolled in our study, of which 83 had concomitant OME. To minimize selection bias, we performed one to two propensity score matching (PSM) between children with and without OME. After PSM, 80 children with OME (OME group) and 157 children without OME (adenoid hypertrophy [AH] group) were selected. The patients' peripheral blood samples were prepared prior to surgery and their immunological parameters were compared between groups. RESULTS: Compared to the AH group, the serum level of C3 was significantly higher in the OME group (0.88 ± 0.01 g/L vs. 0.94 ± 0.02 g/L; p = 0.014), which was the only independent risk factor for OME (odds ratio 13.58, 95% confidence interval 1.25-147.99; p = 0.032). However, no such difference was seen for serum immunoglobulin (IgG, IgA, IgM, IgE), T cell subsets (CD3+, CD4+ and CD8+ T cells), or lymphocytes and monocytes. Further subgroup analyses showed that in children ≤ 5 years old, the C3 level was significantly higher in OME patients (p = 0.023). A subgroup analysis based on sex indicated that there was a significantly higher level of serum C3 (p = 0.009) and lower CD3+ and CD4+ T cells (p = 0.010 and p = 0.021, respectively) in girls with OME compared to those without OME. No association between immunological parameters and adenoid size was found. CONCLUSIONS: There were no significant differences in cellular immunology and humoral immune indicators in children with adenoid hypertrophy with or without OME. In children ≤ 5 years old, significantly higher serum C3 levels in patients with OME demonstrate excessively activated C3 in comparison to patients without OME. For girls, a higher serum level of C3 with a lower amount of CD3+ and CD4+ T cells may be associated with OME.

Edge morphology induced rectifier diode effect in C3N nanoribbon.

The two-dimensional material C3N has a honeycomb structure similar to graphene, but its heterogeneity of carbon and nitrogen elements makes it multifunctional. By performing a first-principles study, we find that edge morphology induces interesting electronic transport properties in step-like heterojunction devices composed of width-variable zigzag C3N nanoribbons. As long as the right part has an edge of all-carbon morphology, negative differential resistance and rectification effects will occur. If both edges are not of all-carbon morphology due to the presence of N atoms, a forward-conducting and reverse-blocking rectifier diode behavior will appear. These phenomena originate from the peculiar electronic structure of the zigzag C3N nanoribbons. The number of energy bands crossing the Fermi level gradually decreases from 2 to 0 as the number of all-carbon edges decreases, realizing a transition from metal to semiconductor. The band gap determines the cut-off region at low bias and the presence of an interface barrier causes the cut-off state to continue under high reverse bias. Diverse edge morphologies, simple cutting methods and rich electronic transport properties make C3N materials competitive in nanodevice applications.

Edge defect switched dual spin filter in zigzag hexagonal boron nitride nanoribbons.

Unlike graphene nanoribbons, zigzag monolayer hexagonal boron nitride nanoribbons (ZBNNRs) possess two distinct edges (B and N edges). Using first-principles calculations, we investigate the spin-dependent electronic transport of ZBNNRs with edge defects. It is found that the defects could make the system operate as a dual spin filter, where the direction of spin polarization is switched by the defect. Further analysis shows that the transmission eigenchannels for the opposite spins reside spatially separated on opposite edges. The defect on one edge could suppress the transmission for only one spin component, but preserve that for the other spin, resulting in a dual spin filter effect. This effect is found to be unaffected by the width of the ribbon and the length of the defect. Moreover, by constructing defects on both edges, the system exhibits two transmission peaks with opposite spins residing discretely on both sides of the Fermi level, suggesting that an electrically controlled dual spin filter based on ZBNNRs is also realizable. As controllable defects have been experimentally fabricated on monolayer boron nitride [T. Pham, A. L. Gibb, Z. Li, S. M. Gilbert, C. Song, S. G. Louie and A. Zettl, Nano Lett., 2016, 16, 7142-7147], our results may shed light on the development of B/N-based spintronic devices.

A progressive metal-semiconductor transition in two-faced Janus monolayer transition-metal chalcogenides.

Breaking the symmetry in the out-of-plane direction in two-dimensional materials to trigger distinctive electronic properties has long been predicted. Inspired by the recent progress in the experimental synthesis of a sandwiched S-Mo-Se structure (Janus SMoSe) at the monolayer limit [Zhang et al., ACS Nano, 2017, 11, 8192-8198], we investigate the transport and electronic structure of two-faced XMoY monolayers (X, Y = O, S, Se and Te) through first-principles calculations. It is found that all the monolayers are semiconductors except OMoTe, which is metallic. Interestingly, the "parents" of OMoTe (MoO2 and MoTe2) are both semiconductors. Further analysis shows that it is the out-of-plane asymmetry-induced strain that results in the metal-semiconductor transition between Janus OMoTe and its parents. By increasing the ratio of O atoms in one face of MoTe2, a progressive decreasing trend of the bandgap, as well as the transition to metallic, is found. In addition, a transition from the direct band gap semiconductor to the indirect one is also observed in the process. This could be used as an effective way to precisely control electronic structures, e.g., the bandgap. Different from other methods, this method uses the intrinsic features of the material, which can persist without the need of additional equipment. Moreover, such a modulating method is expected to be extended to many other transition-metal chalcogenides, showing great application potential.

[Post-transcriptional regulation of chicken PPARγ transcript variant 3 by upstream open reading frame].

Peroxisome proliferator-activated receptor gamma (PPARγ) is a critical regulator of adipogenesis. Our previous study showed that unlike human and mouse PPARγ transcripts, several chicken PPARγ transcript variants contain upstream open reading frames (uORFs) in their 5'untranslated region (5'TR). To decipher the role of uORFs in post-transcriptional regulation of chicken PPARγ gene, we constructed wild-type (psiCHECK2-cPPARγ3-5'UTR-WT) and a uORF mutant (the upstream ATG (uATG) was mutated to stop codon TGA) 5'UTR reporters (psiCHECK2-cPPARγ3- 5'UTR-Mut) of chicken PPARγ transcript variant 3 (cPPARγ3). These two reporters were individually transfected into immortalized chicken pre-adipocytes (ICPA) and DF1 cells, and the renilla luciferase (hRluc) activity and mRNA expression level were detected by reporter assay and qRT-PCR. The results showed that the hRluc activity of the mutated 5'UTR was significantly higher than that of the wild-type 5'UTR in ICPA cells (P<0.01), and the hRluc activity of the mutated 5'UTR tended to be higher than that of the wild-type 5'UTR in DF1 cells, but this difference did not reach statistical significance (P>0.05). The qRT-PCR analysis showed, in ICPA cells, the hRluc mRNA expression was significantly lower in the cells transfected with the mutated 5'UTR construct than in the cells transfected with the wild-type 5'UTR construct (P<0.01). In DF1 cells, the hRluc mRNA expression tended to be lower in the cells transfected with the mutated 5'UTR construct than in the cells transfected with the wild-type 5'UTR construct, but this difference did not reach statistical significance (P>0.05). To further gain insight into the post-transcriptional regulation of cPPARγ3 by the uORF, we constructed the expression plasmids bearing the full-length coding region of chicken PPARγ gene plus either wild-type or mutant uORF 5'UTR (pcDNA3.1-cPPARγ3-WT and pcDNA3.1-cPPARγ3-Mut). These two constructed PPARγ expression plasmids were individually transiently transfected into both ICPA and DF1 cells, and PPARγ mRNA and protein levels were assayed by qRT-PCR and western blotting. The result showed that in both cell lines, PPARγ mRNA expression was significantly lower in the cells transfected with pcDNA3.1-cPPARγ3-Mut than in the cells transfected with pcDNA3.1-cPPARγ3-WT (P<0.05). In contrast, western blot analysis showed that PPARγ protein level was significantly higher in the cells transfected with pcDNA3.1-cPPARγ3-Mut than in the cells transfected with pcDNA3.1-cPPARγ3-WT (P<0.001). Taken together, our results demonstrate that the uORF in 5'UTR of the cPPARγ3 inhibits its translation.

Hydrogen peroxide is a critical regulator of the hypoxia-induced alterations of store-operated Ca2+ entry into rat pulmonary arterial smooth muscle cells.

To investigate the association between store-operated Ca2+ entry (SOCE) and reactive oxygen species (ROS) during hypoxia, this study determined the changes of transient receptor potential canonical 1 (TRPC1) and Orai1, two candidate proteins for store-operated Ca2+ (SOC) channels and their gate regulator, stromal interaction molecule 1 (STIM1), in a hypoxic environment and their relationship with ROS in pulmonary arterial smooth muscle cells (PASMCs). Exposure to hypoxia caused a transient Ca2+ spike and subsequent Ca2+ plateau of SOCE to be intensified in PASMCs when TRPC1, STIM1, and Orai1 were upregulated. SOCE in cells transfected with specific short hairpin RNA (shRNA) constructs was almost completely eliminated by the knockdown of TRPC1, STIM1, or Orai1 alone and was no longer affected by hypoxia exposure. Hypoxia-induced SOCE enhancement was further strengthened by PEG-SOD but was attenuated by PEG-catalase, with correlated changes to intracellular hydrogen peroxide (H2O2) levels and protein levels of TRPC1, STIM1, and Orai1. Exogenous H2O2 could mimic alterations of the interactions of STIM1 with TRPC1 and Orai1 in hypoxic cells. These findings suggest that TRPC1, STIM1, and Orai1 are essential for the initiation of SOCE in PASMCs. Hypoxia-induced ROS promoted the expression and interaction of the SOC channel molecules and their gate regulator via their converted product, H2O2.

Hydrogenated carbon nanotube-based spin caloritronics.

Spin caloritronics has drawn much attention as it combines thermoelectrics and spintronics together. Carbon-based structures, such as graphene, have been found to exhibit different kinds of spin caloritronic features. However, a study of spin caloritronics in carbon nanotubes (CNTs) is still lacking. Using first-principles calculations, we investigate the spin-Seebeck effect (SSE) in partially hydrogenated CNTs. It is found that linear hydrogenation could make CNTs acquire magnetism and exhibit the spin-Seebeck effect. Moreover, an odd-even effect of the SSE is observed, where the even cases could be used as spin-Seebeck diodes. Further analysis shows that, it is induced by the difference of band structures, where the band structure of a tube is a combination of that of graphene-nanoribbon parts "divided" by hydrogenation. This mechanism could be extended to nanotubes with different diameters, showing great application potential. We believe that our results are very useful for the development of nanotube-based spin caloritronic devices.