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AIM: To explore the effect of silent information regulator factor 2-related enzyme 1 (SIRT1) on modulating apoptosis of human lens epithelial cells (HLECs) and alleviating lens opacification of rats through suppressing endoplasmic reticulum (ER) stress. METHODS: HLECs (SRA01/04) were treated with varying concentrations of tunicamycin (TM) for 24h, and the expression of SIRT1 and C/EBP homologous protein (CHOP) was assessed using real-time quantitative polymerase chain reaction (RT-PCR), Western blotting, and immunofluorescence. Cell morphology and proliferation was evaluated using an inverted microscope and cell counting kit-8 (CCK-8) assay, respectively. In the SRA01/04 cell apoptosis model, which underwent siRNA transfection for SIRT1 knockdown and SRT1720 treatment for its activation, the expression levels of SIRT1, CHOP, glucose regulated protein 78 (GRP78), and activating transcription factor 4 (ATF4) were examined. The potential reversal of SIRT1 knockdown effects by 4-phenyl butyric acid (4-PBA; an ER stress inhibitor) was investigated. In vivo, age-related cataract (ARC) rat models were induced by sodium selenite injection, and the protective role of SIRT1, activated by SRT1720 intraperitoneal injections, was evaluated through morphology observation, hematoxylin and eosin (H&E) staining, Western blotting, and RT-PCR. RESULTS: SIRT1 expression was downregulated in TM-induced SRA01/04 cells. Besides, in SRA01/04 cells, both cell apoptosis and CHOP expression increased with the rising doses of TM. ER stress was stimulated by TM, as evidenced by the increased GRP78 and ATF4 in the SRA01/04 cell apoptosis model. Inhibition of SIRT1 by siRNA knockdown increased ER stress activation, whereas SRT1720 treatment had opposite results. 4-PBA partly reverse the adverse effect of SIRT1 knockdown on apoptosis. In vivo, SRT1720 attenuated the lens opacification and weakened the ER stress activation in ARC rat models. CONCLUSION: SIRT1 plays a protective role against TM-induced apoptosis in HLECs and slows the progression of cataract in rats by inhibiting ER stress. These findings suggest a novel strategy for cataract treatment focused on targeting ER stress, highlighting the therapeutic potential of SIRT1 modulation in ARC development.

Abstract FeSe is one of the most enigmatic superconductors. Among the family of iron-based compounds, it has the simplest chemical makeup and structure, and yet it displays superconducting transition temperature ( T c $T_{\text{c}}$ ) spanning 0 to 15 K for thin films, while it is typically 8 K for single crystals. This large variation of T c $T_{\text{c}}$ within one family underscores a key challenge associated with understanding superconductivity in iron chalcogenides. Here, using a dual-beam pulsed laser deposition (PLD) approach, we have fabricated a unique lattice-constant gradient thin film of FeSe which has revealed a clear relationship between the atomic structure and the superconducting transition temperature for the first time. The dual-beam PLD that generates laser fluence gradient inside the plasma plume has resulted in a continuous variation in distribution of edge dislocations within a single film, and a precise correlation between the lattice constant and T c $T_{\text{c}}$ has been observed here, namely, T c ∝ c − c 0 $T_{\text{c}} \propto \sqrt{c- c_{0}}$ , where c is the c-axis lattice constant (and c 0 $c_{0}$ is a constant). This explicit relation in conjunction with a theoretical investigation indicates that it is the shifting of the d xy $d_{\text{xy}}$ orbital of Fe which plays a governing role in the interplay between nematicity and superconductivity in FeSe.

Abstract Stark effect, the electric-field analogue of magnetic Zeeman effect, is one of the celebrated phenomena in modern physics and appealing for emergent applications in electronics, optoelectronics, as well as quantum technologies. While in condensed matter it has prospered only for excitons, whether other collective excitations can display Stark effect remains elusive. Here, we report the observation of phonon Stark effect in a two-dimensional quantum system of bilayer 2H-MoS2. The longitudinal acoustic phonon red-shifts linearly with applied electric fields and can be tuned over ~1 THz, evidencing giant Stark effect of phonons. Together with many-body ab initio calculations, we uncover that the observed phonon Stark effect originates fundamentally from the strong coupling between phonons and interlayer excitons (IXs). In addition, IX-mediated electro-phonon intensity modulation up to ~1200% is discovered for infrared-active phonon A 2u. Our results unveil the exotic phonon Stark effect and effective phonon engineering by IX-mediated mechanism, promising for a plethora of exciting many-body physics and potential technological innovations.

Abstract Chronic wounds are a major complication in patients with diabetes. Here, we identify a therapeutic circRNA and load it into small extracellular vesicles (sEVs) to treat diabetic wounds in preclinical models. We show that circCDK13 can stimulate the proliferation and migration of human dermal fibroblasts and human epidermal keratinocytes by interacting with insulin-like growth factor 2 mRNA binding protein 3 in an N6-Methyladenosine-dependent manner to enhance CD44 and c-MYC expression. We engineered sEVs that overexpress circCDK13 and show that local subcutaneous injection into male db/db diabetic mouse wounds and wounds of streptozotocin-induced type I male diabetic rats could accelerate wound healing and skin appendage regeneration. Our study demonstrates that the delivery of circCDK13 in sEVs may present an option for diabetic wound treatment.

Abstract The AV3Sb5 prototype kagome materials have been demonstrated as a versatile platform for exploring exotic properties in condensed matter physics, including charge density waves, superconductivity, non-trivial electron topology, as well as topological superconductivity. Here we identify that ANb3Bi5 (A = K, Rb, Cs) exhibit non-trivial coexisting superconductivity and topological properties via first-principles calculations. The negative formation energy and the absence of imaginary phonon dispersion demonstrate both thermodynamics and dynamics stabilities of ANb3Bi5 (A = K, Rb, Cs) under ambient conditions. By analytically solving the Allen-Dynes-modified McMillan formula, the superconducting transition temperatures are predicted to be 2.11, 2.15 and 2.21 K for KNb3Bi5, RbNb3Bi5, and CsNb3Bi5, respectively. More importantly, the kagome materials proposed here can be classified into $${{\mathbb{Z}}}_{2}$$ Z 2 topological metals due to the non-trivial topological index and the obvious surface states around the Fermi level. Such coexistence of superconductivity and non-trivial band characters in ANb3Bi5 (A = K, Rb, Cs) offer us more insights to study the relationship between superconductivity and topological properties, and to design innate topological superconductors.

Abstract Intense laser pulses can be used to demagnetize a magnetic material on an extremely short timescale. While this ultrafast demagnetization offers the potential for new magneto-optical devices, it poses challenges in capturing coupled spin-electron and spin-lattice dynamics. In this article, we study the photoinduced ultrafast demagnetization of a prototype monolayer ferromagnet Fe3GeTe2 and resolve the three-stage demagnetization process characterized by an ultrafast and substantial demagnetization on a timescale of 100 fs, followed by light-induced coherent A 1g phonon dynamics which is strongly coupled to the spin dynamics in the next 200–800 fs. In the third stage, chiral lattice vibrations driven by nonlinear phonon couplings, both in-plane and out-of-plane are produced, resulting in significant spin precession. Nonadiabatic effects are found to introduce considerable phonon hardening and suppress the spin-lattice couplings during demagnetization. Our results advance our understanding of dynamic charge-spin-lattice couplings in the ultrafast demagnetization and evidence angular momentum transfer between the phonon and spin degrees of freedom.

Abstract Delayed wound healing is a major complication of diabetes, and is associated with impaired cellular functions. Current treatments are unsatisfactory. Based on the previous reports on microRNA expression in small extracellular vesicles (sEVs), miR‐17‐5p‐engineered sEVs (sEVs17‐OE) and encapsulated them in gelatin methacryloyl (GelMA) hydrogel for diabetic wounds treatment are fabricated. SEVs17‐OE are successfully fabricated with a 16‐fold increase in miR‐17‐5p expression. SEVs17‐OE inhibited senescence and promoted the proliferation, migration, and tube formation of high glucose‐induced human umbilical vein endothelial cells (HG‐HUVECs). Additionally, sEVs17‐OE also performs a promotive effect on high glucose‐induced human dermal fibroblasts (HG‐HDFs). Mechanism analysis showed the expressions of p21 and phosphatase and tensin homolog (PTEN), as the target genes of miR‐17‐5p, are downregulated significantly by sEVs17‐OE. Accordingly, the downstream genes and pathways of p21 and PTEN, are activated. Next, sEVs17‐OE are loaded in GelMA hydrogel to fabricate a novel bioactive wound dressing and to evaluate their effects on diabetic wound healing. Gel‐sEVs17‐OE effectively accelerated wound healing by promoting angiogenesis and collagen deposition. The cellular mechanism may be associated with local cell proliferation. Therefore, a novel bioactive wound dressing by loading sEVs17‐OE in GelMA hydrogel, offering an option for chronic wound management is successfully fabricated.

Abstract Establishing a general model of heterogeneous ice nucleation has long been challenging because of the surface water structures found on different substrates. Identifying common water clusters, regardless of the underlying substrate, is one of the key steps toward solving this problem. Here, we demonstrate the presence of a common water cluster found on both hydrophilic Pt(111) and hydrophobic Cu(111) surfaces using scanning tunneling microscopy and non-contact atomic force microscopy. Water molecules self-assemble into a structure with a central flat-lying hexagon and three fused pentagonal rings, forming a cluster consisting of 15 individual water molecules. This cluster serves as a critical nucleus during ice nucleation on both surfaces: ice growth beyond this cluster bifurcates to form two-dimensional (three-dimensional) layers on hydrophilic (hydrophobic) surfaces. Our results reveal the inherent similarity and distinction at the initial stage of ice growth on hydrophilic and hydrophobic close-packed metal surfaces; thus, these observations provide initial evidence toward a general model for water-substrate interaction.

Neutrophil extracellular traps (NETs) have been considered a significant unfavorable factor for wound healing in diabetes, but the mechanisms remain unclear. The therapeutic application of small extracellular vesicles (sEVs) derived from mesenchymal stem cells (MSCs) has received considerable attention for their properties. Hypoxic preconditioning is reported to enhance the therapeutic potential of MSC-derived sEVs in regenerative medicine. Therefore, the aim of this study is to illustrate the detailed mechanism of NETs in impairment of diabetic wound healing and develop a promising NET-targeting treatment based on hypoxic pretreated MSC-derived sEVs (Hypo-sEVs). Excessive NETs were found in diabetic wounds and in high glucose (HG)-induced neutrophils. Further research showed that high concentration of NETs impaired the function of fibroblasts through activating endoplasmic reticulum (ER) stress. Hypo-sEVs efficiently promoted diabetic wound healing and reduced the excessive NET formation by transferring miR-17–5p. Bioinformatic analysis and RNA interference experiment revealed that miR-17–5p in Hypo-sEVs obstructed the NET formation by targeting TLR4/ROS/MAPK pathway. Additionally, miR-17–5p overexpression decreased NET formation and overcame NET-induced impairment in fibroblasts, similar to the effects of Hypo-sEVs. Overall, we identify a previously unrecognized NET-related mechanism in diabetic wounds and provide a promising NET-targeting strategy for wound treatment.

Abstract Understanding the microscopic mechanism of photoinduced sp2-to-sp3 structural transformation in graphite is a scientific challenge with great importance. Here, the ultrafast dynamics and characteristics of laser-induced structural transformation in graphite are revealed by non-adiabatic quantum dynamic simulations. Under laser irradiation, graphite undergoes an interlayer compression and sliding stage, followed by a key period of intralayer buckling and interlayer bonding to form an intermediate sp2-sp3 hybrid structure, before completing the full transformation to hexagonal diamond. The process is driven by the cooperation of charge carrier multiplication and selective phonon excitations through electron-phonon interactions, in which photoexcited hot electrons scattered into unoccupied high-energy conduction bands play a key role in the introduction of in-plane instability in graphite. This work identifies a photoinduced non-adiabatic transition pathway from graphite to diamond and shows far-reaching implications for designing optically controlled structural phase transition in materials.

Abstract The chiral charge density wave is a many-body collective phenomenon in condensed matter that may play a role in unconventional superconductivity and topological physics. Two-dimensional chiral charge density waves provide the building blocks for the fabrication of various stacking structures and chiral homostructures, in which physical properties such as chiral currents and the anomalous Hall effect may emerge. Here, we demonstrate the phase manipulation of two-dimensional chiral charge density waves and the design of in-plane chiral homostructures in 1T-TaS2. We use chiral Raman spectroscopy to directly monitor the chirality switching of the charge density wave—revealing a temperature-mediated reversible chirality switching. We find that interlayer stacking favours homochirality configurations, which is confirmed by first-principles calculations. By exploiting the interlayer chirality-locking effect, we realise in-plane chiral homostructures in 1T-TaS2. Our results provide a versatile way to manipulate chiral collective phases by interlayer coupling in layered van der Waals semiconductors.

Abstract The lattice geometry induced second-order topological corner states in breathing Kagome lattice have attracted enormous research interests, while the realistic breathing Kagome materials identified as second-order topological insulators are still lacking. Here, we report by first-principles calculations the second-order topological states emerging in two-dimensional d-orbital breathing Kagome crystals, i.e., monolayer niobium/tantalum chalcogenide halides M3QX7 (M = Nb, Ta; Q = S, Se, Te; X = Cl, Br, I). We find that the orbital degree of freedom of d orbitals can give rise to multiple sets of corner states. Combining fraction corner anomaly, orbital components and real space distribution of the corner states, we can also identify the topology of these corner states. Our work not only extends the lattice geometry induced second-order topological states to realistic materials, but also builds a clear and complete picture on their multiple sets of second-order topological states.

Here the author study Self-trapped exciton emission for multiphoton excited luminescence in ZnO nanoparticle which until now have not been explored. They provide a reason for the emission enhancement and apply these materials in optical imaging for a proof of concept.

Abstract Ferroptosis plays an essential role in the development of diabetes and its complications, suggesting potential therapeutic strategies targeting ferroptosis. Secretory autophagosomes (SAPs) carrying cytoplasmic cargoes have been recognized as novel nano‐warrior to defeat diseases. Here, it is hypothesized that SAPs derived from human umbilical vein endothelial cells (HUVECs) can restore the function of skin repair cells by inhibiting ferroptosis to promote diabetic wound healing. High glucose (HG)‐caused ferroptosis in human dermal fibroblasts (HDFs) is observed in vitro, which results in impaired cellular function. SAPs successfully inhibit ferroptosis in HG‐HDFs, thereby improving their proliferation and migration. Further research show that the inhibitory effect of SAPs on ferroptosis resulted from a decrease in endoplasmic reticulum (ER) stress‐regulated generation of free ferrous ions (Fe2+) in HG‐HDFs and an increase in exosome release to discharge free Fe2+ from HG‐HDFs. Additionally, SAPs promote the proliferation, migration, and tube formation of HG‐HUVECs. Then the SAPs are loaded into gelatin‐methacryloyl (GelMA) hydrogels to fabricate functional wound dressings. The results demonstrate the therapeutic effect of Gel‐SAPs on diabetic wounds by restoring the normal behavior of skin repair cells. These findings suggest a promising SAP‐based strategy for the treatment of ferroptosis‐associated diseases.

Abstract We employ first-principles calculations combined with self-consistent phonon theory and Boltzmann transport equations to investigate the thermal transport and thermoelectric properties of full-Heusler compound Na2TlSb. Our findings exhibit that the strong quartic anharmonicity and temperature dependence of the Tl atom with rattling behavior plays an important role in the lattice stability of Na2TlSb. We find that soft Tl-Sb bonding and resonant bonding in the pseudocage composed of the Na and Sb atoms interaction is responsible for ultralow κ L. Meanwhile, the multi-valley band structure increases the band degeneracy, results in a high power factor in p-type Na2TlSb. The coexistence of ultralow κ L and high power factor presents that Na2TlSb is a potential candidate for thermoelectric applications. Moreover, these findings help to understand the origin of ultralow κ L of full-Heusler compounds with strong quartic anharmonicity, leading to the rational design of full-Heusler compounds with high thermoelectric performance.

A detailed experimental study of ethanol spray swirling flames was performed in an axial bluff body stabilized burner. The characteristics of the non-reacting and reacting sprays were recorded by particle imaging velocimetry (PIV) and planar laser-induced fluorescence (PLIF) of the OH radical. A few typical flames with different structures (outer-side-flame-lifting, stable, and near-blow-off) were compared and analyzed. The parameters of the spray, including the spray half-angle (α) and droplet number density (nd), are quantified, and it has been found the flame structure and stability were strongly correlated with the droplet distribution. Several parameters of the flow field, such as velocity magnitude (|U| vorticity (ωz), and turbulent kinetic energy (TKE), are quantitively analyzed, and it is observed that the local strain rate rose as the air flow rate increased, which is not conducive to local flame stability. Regarding the flame, quantities such as progress variable (), flame height (Lf), lift–off height (hlf), and symmetry factor (Snd and S) are calculated, and it can be observed that the flame symmetry keeps worsening when approaching blow–off, and the inner flame branch exhibits a worse stabilization than the outer one. Our comprehensive investigations offer a deeper understanding of stable combustion in such two–phase flames.

The shift current effect, in materials lacking inversion symmetry, may potentially allow the performance of photovoltaics to surpass the Shockley-Queisser limit for traditional p-n junction-based photovoltaics. Although the shift-current effect has been studied from first principles via second-order perturbation theory, an understanding of the dynamics of hot carriers is still lacking. We investigate the dynamics of the shift current in monolayer WS_{2} via real-time propagation time-dependent density functional theory (rt-TDDFT). We find that the shift current can be generated within 10–20 fs after turning on the lights, and dissipates within approximately a few tens of femtoseconds after turning off the lights. This property can be used for ultrafast photon detection. This work provides an important step toward understanding the dynamics of shift-current effects, which is crucial for device applications.

A close look at Google’s GNoME inorganic materials dataset (Merchant et al 2023 Nature 624 80–85), and 11 things you would like to know.

DFT + U is a widely used treatment in the density functional theory (DFT) to deal with correlated materials that contain open-shell elements, whereby the quantitative and sometimes even qualitative failures of local and semi-local approximations can be corrected without much computational overhead. However, finding appropriate U parameters for a given system and structure is non-trivial and computationally intensive, because the U value has generally a strong chemical and structural dependence. In this work, we address this issue by building a machine learning (ML) model that enables the prediction of material- and structure-specific U values at nearly no computational cost. Using Mn–O system as an example, the ML model is trained by calibrating DFT + U electronic structures with the hybrid functional results of more than 3000 structures. The model allows us to determine an accurate U value (MAE = 0.128 eV, R ^2 = 0.97) for any given Mn–O structure. Further analysis reveals that M–O bond lengths are key local structural properties in determining the U value. This approach of the ML U model is universally applicable, to significantly expand and solidify the use of the DFT + U method.

The Mott insulator provides an excellent foundation for exploring a wide range of strongly correlated physical phenomena, such as high-temperature superconductivity, quantum spin liquid, and colossal magnetoresistance. A Mott insulator with the simplest degree of freedom is an ideal and highly desirable system for studying the fundamental physics of Mottness. In this study, we have unambiguously identified such an anticipated Mott insulator in a van der Waals layered compound Nb_{3}Cl_{8}. In the high-temperature phase, where interlayer coupling is negligible, density functional theory calculations for the monolayer of Nb_{3}Cl_{8} suggest a half-filled flat band at the Fermi level, whereas angle-resolved photoemission spectroscopy experiments observe a large gap. This observation is perfectly reproduced by dynamical mean-field theory calculations considering strong electron correlations, indicating a correlation-driven Mott insulator state. Since this half-filled band derived from a single 2a_{1} orbital is isolated from all other bands, the monolayer of Nb_{3}Cl_{8} is an ideal realization of the celebrated single-band Hubbard model. Upon decreasing the temperature, the bulk system undergoes a phase transition, where structural changes significantly enhance the interlayer coupling. This results in a bonding-antibonding splitting in the Hubbard bands, while the Mott gap remains dominant. Our discovery provides a simple and seminal model system for investigating Mott physics and other emerging correlated states.

Abstract Methods to probe and understand the dynamic response of materials following impulsive excitation are important for many fields, from materials and energy sciences to chemical and neuroscience. To design more efficient nano, energy, and quantum devices, new methods are needed to uncover the dominant excitations and reaction pathways. In this work, we implement a newly-developed superlet transform—a super-resolution time-frequency analytical method—to analyze and extract phonon dynamics in a laser-excited two-dimensional (2D) quantum material. This quasi-2D system, 1T-TaSe2, supports both equilibrium and metastable light-induced charge density wave (CDW) phases mediated by strongly coupled phonons. We compare the effectiveness of the superlet transform to standard time-frequency techniques. We find that the superlet transform is superior in both time and frequency resolution, and use it to observe and validate novel physics. In particular, we show fluence-dependent changes in the coupled dynamics of three phonon modes that are similar in frequency, including the CDW amplitude mode, that clearly demonstrate a change in the dominant charge-phonon couplings. More interestingly, the frequencies of the three phonon modes, including the strongly-coupled CDW amplitude mode, remain time- and fluence-independent, which is unusual compared to previously investigated materials. Our study opens a new avenue for capturing the coherent evolution and couplings of strongly-coupled materials and quantum systems.

The Su-Schrieffer-Heeger (SSH) model is a prototypical model of topological states, initially proposed to describe spinless electrons on a one-dimensional (1D) dimerized lattice. Here, the authors realize a 2D SSH model in a rectangular lattice of silicon atoms on a silver substrate, observing gapped Dirac cones by angle-resolved photoemission spectroscopy.

Conventional silicon-based transistors, which sit at the heart of every computer, are fast approaching the limit of miniaturisation. Here, Meng et al demonstrate a field-effect transistor composed of a single rutheniumdiarylethene molecule with large on/off ratio.

Based on gear transmission conjugate-curve theory research， taking the internal meshing gear transmission with curve element as the object， general meshing equation of spatial conjugate curves along the designated contact angle position is derived and general expressions of space conjugate curves under internal contact conditions are also obtained. According to space equidistant-enveloping method， conjugate surfaces which inherit the meshing characteristics of spatial conjugate curves are generated and three contact types including convex-to-convex， convex-to-plane and convex-to-concave forms are proposed if changing the relative motion position and equidistant radius. Taking the spatial cylindrical spiral curve as an example， combined with the theoretical analysis results and given design parameters， three-dimensional solid models of internal meshing gear pair with convex-to-concave contact are established. The pressure angle on the tooth surface contact point is defined and calculation method of sliding ratio for the mated tooth surfaces is also put forward in terms of space conjugate curves. Calculation and analysis of the contact locus of conjugated internal meshing tooth surfaces are conducted. Further studies on meshing characteristics， contact mechanics and manufacturing method of tooth profiles will be carried out.

Abstract Light-modulated electron-phonon coupling (EPC) is significant in many intriguing phenomena including light-enhanced superconductivity, polaron formation, and hidden charge orders, which provides a powerful strategy to engineer materials’ functionalities on demand. Here we explore EPC in photoexcited graphene during the ultrafast photocarrier dynamics with a phonon bath. Via analysing energy transport between electrons and phonons, light-induced EPC enhancement by more than one order of magnitude is demonstrated, which originates from the dynamic distribution of photoexcited carriers out of equilibrium. Excellent agreements between theory and experiment have been achieved, justifying the validity of the present approach for extracting excited-state dynamic properties. Our result unravels a crucial impact of photoexcitation on EPC by modulating the density and distribution of photocarriers, and provides a useful strategy for tracking ultrafast EPC in real time.

Cs2Ag1−x Na x In1−y Bi y Cl6 with high photoluminescence quantum yield (PLQY) and broadband emission due to self‐trapped excitons (STEs) is one of the promising candidates for single‐emitter‐based white light–emitting materials and devices. Considering fundamental physical mechanisms, structure design and performance optimization of devices, comprehensive knowledge of the elasticity, and thermal properties are imperative to understand the formation of STEs in Cs2Ag1−x Na x In1−y Bi y Cl6 and minimize thermomechanical stresses induced device failure, respectively. However, its elastic and thermal properties are still poorly understood. Herein, the first angle‐resolved Brillouin light scattering (BLS) measurements study for a bulk Cs2Ag0.4Na0.6InCl6:0.04%Bi3+ crystal is reported, and the first‐principles calculations of phonon dispersions are used to further validate our experimental results. Using the measured Brillouin frequency shifts, we evaluate the low elasticity of Cs2Ag0.4Na0.6InCl6:0.04%Bi3+: C 11 = 38.63, C 12 = 16.11, and C 44 = 10.20 GPa, which supports the thesis that STEs exist in semiconductors with excitons and a soft lattice. Additionally, an ultralow‐acoustic Debye temperature (87 K) and lattice thermal conductivity (1.03 W m−1 K−1) along the [111] direction of Cs2Ag0.4Na0.6InCl6:0.04%Bi3+, which indicates the weak interatomic interactions and elasticity are estimated. Furthermore, a general approach is also provided to investigate the elastic and thermal properties of materials with different crystal structures utilizing angle‐resolved BLS spectroscopy.

Photoexcitation in Weyl semimetals is recently reported to induce topological phase transitions useful for ultrafast switching devices. Here, the authors predict that the symmetry of the atomic orbitals comprising the Weyl bands in response to linear light polarization allows for not only annihilation but also separation of Weyl quasiparticles.

Transition metal dichalcogenides (TMDs) are a class of materials with various useful properties, and it is worthwhile to have a thorough evaluation of the characteristics of the TMDs, most importantly, their structural stability and exfoliability, in a systematic fashion. Here, by employing high-throughput first-principles calculations, we investigate the vast phase space of TMDs, including 16 bulk phases and 6 monolayer phases for all possible TMD combinations [comprising (3d, 4d, 5d) transition-metal cations and (S, Se, Te) anions], totaling 1386 compounds. Through the ‘bird-view’ of the as-large-as-possible configurational and chemical space of TMDs, our work presents comprehensive energy landscapes to elucidate the thermodynamic stability as well as the exfoliability of TMDs, which are of vital importance for future synthesis and exploration towards large-scale industrial applications.

A kind of internal gear drive with three contact points is presented in the article. Firstly, the pinion with circular-arc form and the internal gear with parabola-circular form are proposed, respectively. General equations of tooth profiles are provided. Furthermore, according to gear geometry, mathematical model of the pinion and the internal gear are generated and their tooth surfaces equations are derived. Meanwhile, based on design parameters, 3D solid models of the new gear pair with three contact points are developed utilizing modeling software. Finally, meshing characteristics of generated new gear pair are analyzed, such as sliding ratios and contact stress conditions. General corresponding comparisons with other internal gear drive are also discussed. Research conclusions show that the new internal gear pair with three contact points has low sliding ratios and high contact strength.

Abstract Understanding hot carrier dynamics between plasmonic nanomaterials and its adsorbate is of great importance for plasmon‐enhanced photoelectronic processes such as photocatalysis, optical sensing and spectroscopic analysis. However, it is often challenging to identify specific dominant mechanisms for a given process because of the complex pathways and ultrafast interactive dynamics of the photoelectrons. Here, using CO2 reduction as an example, the underlying mechanisms of plasmon‐driven catalysis at the single‐molecule level using time‐dependent density functional theory calculations is clearly probed. The CO2 molecule adsorbed on two typical nanoclusters, Ag20 and Ag147, is photoreduced by optically excited plasmon, accompanied by the excitation of asymmetric stretching and bending modes of CO2. A nonlinear relationship has been identified between laser intensity and reaction rate, demonstrating a synergic interplay and transition from indirect hot‐electron transfer to direct charge transfer, enacted by strong localized surface plasmons. These findings offer new insights for CO2 photoreduction and for the design of effective pathways toward highly efficient plasmon‐mediated photocatalysis.

Charge density wave (CDW) order is an emergent quantum phase that is characterized by periodic lattice distortion and charge density modulation, often present near superconducting transitions. Here, we uncover a novel inverted CDW state by using a femtosecond laser to coherently reverse the star-of-David lattice distortion in 1T-TaSe2. We track the signature of this novel CDW state using time- and angle-resolved photoemission spectroscopy and the time-dependent density functional theory to validate that it is associated with a unique lattice and charge arrangement never before realized. The dynamic electronic structure further reveals its novel properties that are characterized by an increased density of states near the Fermi level, high metallicity, and altered electron–phonon couplings. Our results demonstrate how ultrafast lasers can be used to create unique states in materials by manipulating charge-lattice orders and couplings.

The last few decades have witnessed the extraordinary advances in theoretical and experimental tools, which have enabled the manipulation and monitoring of ultrafast dynamics with high precisions. For modeling dynamical responses beyond the perturbative regime, computational methods based on time-dependent density functional theory (TDDFT) are the optimal choices. Here, we introduce TDAP (time-dependent ab initio propagation), a first-principle approach that is aimed at providing robust dynamic simulations of light-induced, highly nonlinear phenomena by real-time calculation of combined photonic, electronic, and ionic quantum mechanical effects within a TDDFT framework. We review the implementation of real-time TDDFT with numerical atomic orbital formalisms, which has enabled high-accuracy, large-scale simulations with moderate computational cost. The newly added features, i.e., the time-dependent electric field gauges and controllable ionic motion make the method especially suitable for investigating ultrafast electron-nuclear dynamics in complex periodic and semiperiodic systems. An overview of the capabilities of this first-principle method is provided by showcasing several representative applications including high-harmonic generation, tunable phase transitions, and new emergent states of matter. The method demonstrates a great potential in obtaining a predictive and comprehensive understanding of quantum dynamics and interactions in a wide range of materials at the atomic and attosecond space-time scale.

The physical origins of charge density waves in 1T-TiSe2 and their response to ultrafast excitation have long been a topic of theoretical and experimental debate. Here the authors present an ab initio theory that successfully captures the observed dynamics of charge density wave formation.

Strong-field photoemission is the emission of electrons driven by a strong electric field of light. Here the authors demonstrate a highly non-linear strong-field photoemission, approaching the 40th power-law scaling, from carbon nanotubes, yielding a photoemission current with up to 100% carrier-envelope phase modulation depth.

Molecular sieving is important for proton exchange fuel cells, water desalination and gas separation, but achieving optimal proton conductivity and selectivity is difficult. Here the authors use theory to show that a graphdiyne membrane is promising for proton transport in aqueous media at room temperature.

A promising route to realize solar-to-chemical energy conversion resorts to water splitting using plasmon photocatalysis. However, the ultrafast carrier dynamics and underlying mechanism in such processes has seldom been investigated, especially when the single-atom catalyst is introduced. Here, from the perspective of quantum dynamics at the atomic length scale and femtosecond time scale, we probe the carrier and structural dynamics of plasmon-assisted water splitting on an Ag-alloyed Pt single-atom catalyst, represented by the Ag19Pt nanocluster. The substitution of an Ag atom by the Pt atom at the tip of the tetrahedron Ag20 enhances the interaction between water and the nanoparticle. The excitation of localized surface plasmons in the Ag19Pt cluster strengthens the charge separation and electron transfer upon illumination. These facts cooperatively turn on more than one charge transfer channels and give rise to enhanced charge transfer from the metal nanoparticle to the water molecule, resulting in rapid plasmon-induced water splitting. These results provide atomistic insights and guidelines for the design of efficient single-atom photocatalysts for plasmon-assisted water splitting.

Stratified swirled flame is widely used in gas turbines and aero engines to achieve low emissions. However, the limitation of implementing laser diagnostic in real combustors acquires more accurate measurements of field information in the flame, especially the unsteady heat release, which relates to a lot of important phenomena, such as combustion instability and blow-off. The present study employs large eddy simulation (LES) combined with a detailed OH* chemiluminescence reaction mechanism to validate the chemiluminescent image of OH* in a stratified swirled flame at the atmosphere condition. 10 kHz particle image velocimetry images and OH* filtered images are recorded during the experiment. The heat release and flow structure of the stratified swirled flame at two different fuel stratification ratios show distinguished flame shapes. In general, the velocity results of LES have good agreement with the measurement. The numerical OH* and heat release comparison reveals a strong dependence on the local strain rate and turbulence level of OH* emissions. It is also noticed that the wrong flame shapes may be deduced from the Abel inversed OH* image since the signals are weak in the outer recirculation zone. This indicates that the strain rate in different regions of stratified swirl flame has a significant impact on OH* signal distribution. The results provide insight into the ability of chemiluminescent emissions, such as OH*, to indicate heat release in more complex industrial flames.

It remains a challenge to fully control molecular electronics. Here, Meng et al. show a reversible two-mode single-molecule switch, where the conductance through the molecular backbone is controlled by an in situ chemical gating via bias-dependent trans–cis isomerisation on an azobenzene sidegroup.

Controlling ferroelectric polarization is conventionally achieved by applying electric fields, mechanical force or similar. Here reversible switching of the bulk polarization of a BiFeO3 thin film is demonstrated by pattering aqueous solution on to the surface enabling large-scale switching.

The fatigue strength of a gear tooth surface is affected by various factors, which subsequently impacts the transmission performance of gears. Usually, shot peening treatment is carried out during processing to improve the performance of gears. Most current studies focus on theoretical descriptions and simulation analyses of shot peening treatment. However, in this paper, the relationships among shot peening treatment, residual stress, and bending fatigue strength of a gear tooth surface are discussed, through experimental methods. Based on X-ray stress analysis, at select locations on the test samples, the residual stresses on gear tooth surfaces with and without shot peening treatment are determined and contrasted. The results show that shot peening treatment can effectively increase the residual stress on gear tooth surfaces. In addition, an electromagnetic resonance fatigue tester is used to analyze the bending fatigue strength of gear tooth surfaces. The test results indicate that the bending fatigue strength of the gear teeth with shot peening is higher than that of the gear teeth without shot peening. The obtained conclusions lay the foundation for further practical engineering applications of gears.

The study of the flame under the acoustic excitation contributes to the study of flame self-excited thermoacoustic instability. Although non-premixed combustion is widely used in industry, research on its combustion instability characteristics is relatively few. This paper experimentally studies the response of a non-premixed swirl flame under excitation. The geometry modifications are the length of the inlet section which is set to be 0.245 m, 0.345 m and 0.445 m and the installation of separation plates. Through the analysis of flame response behavior at different excitation frequencies, combined with the calculation of acoustic mode, we find that for the 0.245 m and 0.345 m inlet length cases, the maximum flame heat release fluctuation responds near 144 Hz. This mode is due to the resonance of the fuel pipe. For the 0.445 m inlet length cases, the maximum flame heat release responds near 134 Hz. This mode is a mixed mode of fuel pipe and combustion chamber. The maximum flame response occurs at the point where the pressure fluctuation reaches the maximum in the inlet section. The image analysis shows the same mode distinction trend between short and long inlet length. Besides, the removing of separation plates leads to a more stable response of the flame in low inlet airflow rate. However, at high airflow rate, the flame tends to be more unstable. Moreover, the higher acoustic forcing frequency than quarter-wave mode will cause the quarter-wave resonant frequency to appear. The results of our work can benefit the implications of thermoacoustic instability in non-premixed flame.

Non-Hermitian (NH) topological states, such as the doubly-degenerate nodes dubbed as exceptional points (EPs) in Bloch band structure of 2D lattices driven by gain and loss, have attracted much recent interest. We demonstrate theoretically that in the three-site edge-centered lattices, i.e. the so-called line-graph lattices, such as kagome lattice which is a line graph of hexagonal lattice, there exist three types of triply-degenerate EPs evolving intriguingly on another set of line graphs in the reciprocal space. A single TEP (STEP) with ±1/3 topological charge moves faithfully along the edges of reciprocal line graphs with varying gain and loss, while two STEPs merge distinctively into one unconventional orthogonal double TEP (DTEP) with ±2/3 charge at the vertices, which is characterized with two ordinary self-orthogonal eigenfunctions but one surprising ‘orthogonal’ eigenfunction. Differently, in a modified line-graph lattice with an off-edge-center site, the ordinary coalesced state of DTEPs emerges with three identical self-orthogonal eigenfunctions. Such NH states and their evolution can be generally realized in various artificial systems, such as photonic and sonic crystals, where light and sonic vortex beams with different fractional twisting can be found. Our findings shed new light on fundamental understanding of gapless topological states in NH systems in terms of creation and evolution of high-order EPs, and open up new research directions to further link line graph and flow network theory coupled with topological physics, especially under non-equilibrium gain/loss conditions.

Collision avoidance radar for trains is pregnant for safety transportation. In order to realize low cost and high performance of azimuth accuracy, we have developed MMW (Milli-Meter Wave) radar, which employs switched phased array and frequency stepped technology. This paper analyses the radiation patterns of transmitting/receiving antennas and compensation method for amplitude/phase errors of synthetic wideband frequency stepped signal. To confirm the operation of the radar, low cost millimeter-wave collision avoidance radar was fabricated. Lots of experiments confirmed a high azimuth and range resolution.

The electronic transport and thermoelectric properties in n -type doped monolayer MoS _2 are investigated by a parameter-free method based on first-principles calculations, electron–phonon coupling (EPC), and Boltzmann transport equation (BTE). Remarkably, the calculated electron mobility μ ∼ 47 cm ^2 V ^−1 s ^−1 and thermoelectric power factor σS ^2 ∼ 2.93 × 10 ^−3 W m ^−1 K ^−2 at room temperature are much lower than the previous theoretical values (e.g. μ ∼ 130–410 cm ^2 V ^−1 s ^−1 and σS ^2 ∼ 2.80 × 10 ^−2 W m ^−1 K ^−2 ), but agree well with the most recent experimental findings of μ ∼ 37 cm ^2 V ^−1 s ^−1 and σS ^2 ∼ 3.00 × 10 ^−3 W m ^−1 K ^−2 . The EPC projections on phonon dispersion and the phonon branch dependent scattering rates indicate that the acoustic phonons, especially the longitudinal acoustic phonons, dominate the carrier scattering. Therefore, a mobility of 68 cm ^2 V ^−1 s ^−1 is achieved if only the acoustic phonons induced scattering is included, in accordance with the result of 72 cm ^2 V ^−1 s ^−1 estimated from the deformation potential driven by acoustic modes. Furthermore, via excluding the scattering from the out-of-plane modes to simulate the EPC suppression, the obtained mobility of 258 cm ^2 V ^−1 s ^−1 is right in the range of 200–700 cm ^2 V ^−1 s ^−1 measured in the samples with top deposited dielectric layer. In addition, we also compute the lattice thermal conductivity κ _L of monolayer MoS _2 using phonon BTE, and obtain a κ _L ∼ 123 W m ^−1 K ^−1 at 300 K.

Two-dimensional (2D) topological insulators (TIs) and Chern insulators (CIs) promise quantum spin Hall (QSH) and quantum anomalous Hall (QAH) states without dissipation. By combining first-principles calculations with Wannier functions-based tight-binding (TB) modeling, we demonstrate that the graphenelike BC _3 , which was fabricated early in experiment, can become 2D TIs and CIs through suitable decoration of adatoms. For the thallium (Tl) decorated BC _3 systems, three low-energy structures with the same stoichiometry of BC _3 Tl, whose stabilities are verified by the ab initio evolutionary algorithm, are found to be robust 2D TIs with the largest topologically nontrivial band gap of about 224 meV. For the transition metal atoms adsorbed BC _3 , three (2 × 2) BC _3 systems with one adatom of technetium (Tc), rhenium (Re), or ruthenium (Ru) are found to be good CIs with the ferromagnetic moments of 1 to 2 μ _B , nontrivial gaps of 38–50 meV, and nonzero Chern numbers of −1 to 1. These properties indicate that the systems of graphenelike BC _3 with adatoms are good platforms for the study of QSH and QAH effects.

Orientational dependence of catalytic activity for water splitting reaction on a two-dimensional gold cluster supported on MgO/Ag(001) has been identified using first-principles calculations. Strong oscillations are found in water adsorption energy, the dissociation barrier, and the binding energy of the dissociated H atom, with two different orientational patterns. These two patterns correlate with the wavefunction symmetry of frontier orbitals of selected quantum well states (QWSs). This finding reveals a new aspect of orbital symmetry in catalytic reactions without involving changes in the shape or size of the atomic cluster, and is promising for potential applications in chemical reactions using the orbital degree of freedom of QWSs.

In recent years, the innovative applications of integrated augmented reality (AR) into educational settings had increased rapidly in Taiwan. AR provides the scene of the real world while interacting with the virtual and physical objects and increases students' learning motivation. This paper presents an empirical study that investigated the middle-school students learning health education courses related to human body structure knowledge integrating AR technology with different learning style preferences. A two-way t-test was applied to examine the experimental (AR-based) or control (traditional lecture) group in health education courses for four consecutive weeks, comparing with pre-test and post-test scores. The findings revealed that students in the AR experimental group apparently had a higher learning achievement than the students in the control group. Moreover, students with different learning styles had the significant differences in learning achievement. The research outcomes provided the practical implications for educators in incorporating AR applications for enhancing learning motivation and to study the differences in students' learning style.