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To predict the impact resistance of steel fiber reinforced concrete (SFRC), 50 specimens with different fiber lengths and different fiber contents were loaded using ABAQUS finite element software to obtain data in this paper. Two machine learning (ML) models, backward propagation-artificial neural network (BP-ANN) and support vector machine (SVM), were used to train the data. The results show that in the prediction of the impact resistance of steel fiber reinforced concrete by this model, the deviation of the predicted values from the real values is small, and the two models are well fitted. To further optimize the model, the parameters of the prediction model were adjusted using the whale optimization algorithm (WOA) in this paper, and the accuracy of the optimized model was significantly improved. After optimization, the WOA-BP-ANN and WOA-SVM models have better generalization ability and higher prediction accuracy than the WOA-SVM model.

Plasmon-induced charge transfer causes electron-hole spatial separation at the metal-semiconductor interface, which plays a key role in photocatalytic and photovoltaic applications. The Schottky barrier formed at the metal-semiconductor interface can modify the hot carrier dynamics. Taking the Ag-TiO

Intervalley scattering involves microscopic processes that electrons are scattered by atomic-scale defects on nanometer length scales. Although central to our understanding of electronic properties of materials, direct characterization and manipulation of range and strength of the intervalley scattering induced by an individual atomic defect have so far been elusive. Using scanning tunneling microscope, we visualized and controlled intervalley scattering from an individual monovacancy in graphene. By directly imaging the affected range of intervalley scattering of the monovacancy, we demonstrated that it is inversely proportional to the energy, i.e., it is proportional to the wavelength of massless Dirac Fermions. A giant electron-hole asymmetry of the intervalley scattering is observed because that the monovacancy is charged. By further charging the monovacancy, the bended electronic potential around the monovacancy softened the scattering potential, which, consequently, suppressed the intervalley scattering of the monovacancy., 18 pages, 4 figures

Hot carriers generated by plasmonic damping have been suggested to promote photocatalysis, yet it remains unclear how the nonthermalized hot carriers dynamically activate and promote the energy transfer processes. Here, we present an Anderson-Newns model to describe the vibrational excitation and bond dissociation induced by plasmonic hot carriers. The nonthermal distribution of the hot carriers generated by plasmon damping is accounted for on equal footing with thermal carriers at a given temperature in the electron-molecule scattering. We found that the nonthermal electrons in the high energy region can, albeit in much smaller populations, provide an efficient and dominant channel for photodissociation especially in the low-temperature and quantum plasmon regime. Our model captures the wavelength dependence and reproduces the enhancement factors observed by experiments for oxygen dissociation on silver nanoparticles. It also paves a way to harvesting nonthermal plasmonic energy for photocatalysis in the quantum regime.

Metallic nanostructures can strongly absorb light through their plasmon excitations, whose nonradiative decay generates hot electron–hole pairs. When the metallic nanostructure is interfaced with a semiconductor, the spatial separation of hot carriers plays the central and decisive roles in photovoltaic and photocatalytic applications. In recent years, free-electron metals like Al have attracted tremendous attentions due to the much higher plasmon frequencies that could extend to the ultraviolet regime. Here, the plasmon excitations and charge separations at the Al–TiO2 interfaces have been investigated using quantum-mechanical calculations, where the atomic structures and electronic dynamics are all treated from first-principles. It is found that the high-frequency plasmon of Al produces abundant and broad-band hot-carrier distributions, where the electron–hole symmetry is broken by the presence of the semiconductor band gap. Such an asymmetric hot-carrier distribution provides two competing channels, which can be controlled either by tuning the laser frequency, or by harnessing the plasmon frequency through the geometry and shape of the metallic nanostructure. Our study suggests that the Al plasmon offers a versatile and tunable pathway for the charge transfer and separation, and has general implications in plasmon-assisted photovoltaics and photocatalysis.

Water and ions transport through graphene nanochannels has attracted considerable attention thanks to the possibility of dimensional control of the channel sizes down to single atomic layer. Using ...

Creating a single-carbon vacancy introduces (quasi-)localized states for both σ and π electrons in graphene. Theoretically, interactions between the localized σ electrons and quasilocalized π electrons of a single-carbon vacancy in graphene are predicted to control its magnetism. However, experimentally confirming this prediction through manipulating the interactions remains an outstanding challenge. Here we report the manipulation of magnetism in the vicinity of an individual single-carbon vacancy in graphene by using a scanning tunnelling microscopy (STM) tip. Our spin-polarized STM measurements, complemented by density functional theory calculations, indicate that the interactions between the localized σ and quasilocalized π electrons could split the π electrons into two states with opposite spins even when they are well above the Fermi level. Via the STM tip, we successfully manipulate both the magnitude and direction of magnetic moment of the π electrons with respect to that of the σ electrons. Three different magnetic states of the single-carbon vacancy, exhibiting magnetic moments of about 1.6 μB, 0.5 μB, and 0 μB respectively, are realized in our experiment.

Our previous work demonstrated that graphene devices with monovacancy defects possess spin filtering effect which offers potential applications in spintronics. Here, using first-principles calculations, we further study the spin-dependent electron transport properties and spin filtering efficiency of graphene devices with double vacancies that are arrayed in parallel and serial connections. It is found that devices with vacancies in parallel connection follow classical Kirchhoff circuit law. Both spin-up and spin-down currents are amplified while spin filtering efficiency remains the same as compared to the monovacancy devices. In contrast, amplification of spin filtering efficiency is realized in devices with serially connected double vacancies. In addition, it is shown that the spin current can be flipped reversibly by nanomechanical deformation as we observed in devices with monovacancy. Our findings demonstrate the possibility to engineer the spin filtering effect for vacancy based spintronic devices.

Metallothioneins (MTs) are cysteine-rich, low-molecular-weight proteins. Plant MTs play important roles in detoxification and cellular redox regulation. In this study, hydroponic experiments of sugarcane ( Saccharum officinarum L. cv. Badila) were carried out to study the effects of CdCl2, ZnSO4, and CuCl2 treatments on plantlet growth. And then three kinds of heavy metal content in both shoots and roots of sugarcane were detected, showing an enrichment and tolerance ability to Cd2+, Zn2+, and Cu2+ in Badila seedlings. Three metallothionein genes, termed as ScMT 1 (accession number: KJ504373), ScMT 2-1-5 (accession number: MH191346), and ScMT 3 (accession number: KJ5043704), were isolated from Badila. ScMT 1 contained an open reading frame (ORF) of 228 bp encoding 75 amino acids residues. The first (52 bp) and second (176 bp) extrons of ScMT 1 were separated by an intron (283 bp). ScMT 2-1-5 contained an ORF of 246 bp encoding 81 amino acids residues. The first (64 bp), second (87 bp), and third (101 bp) extrons of ScMT2-1-5 were separated by two introns (483 bp and 853 bp). ScMT 3 contained an ORF of 198 bp encoding 65 amino acids residues. The first (50 bp) and second (148 bp) extrons of ScMT 3 were separated by an intron (259 bp). The deduce protein ScMT1, ScMT2-1-5, and ScMT3 were categorized into the subfamily of plant type1, type2, and type3 MTs, respectively. The expression profiles of the three genes under different heavy-metal stresses were investigated by real-time quantitative PCR (qRT-PCR) analysis. When treated with Cd2+, the expression of ScMT 2-1-5 was continuously and significantly up-regulated in both shoots and roots, while that of ScMT 1 showed a delayed up-regulation pattern. The expression of ScMT 3 showed a delayed up-regulation pattern in shoots and a trend of first raising and then suppressing in roots. The results suggested that ScMT 2-1-5 might play a more active role in response to Cd2+ in sugarcane while ScMT 3 might not, and ScMT 1 is involved in the molecular responses of Cd2+ stress at the later stage. When treated with Cu2+, the expression of ScMT 1 was continuously and significantly up-regulated, and that of ScMT 2-1-5 and ScMT 3 general up-regulated in shoots. As in the roots, the expression of both ScMT 1 and ScMT 2-1-5 showed a delayed up-regulation pattern which was significantly up-regulated at the later stage, while that of ScMT 3 significantly up-regulated at the early stage. It revealed that ScMT 1 cooperated with ScMT 2-1-5 and ScMT 3 is involved in the positive response to Cu2+ stress in roots, and might play a more positive role than ScMT 2-1-5 and ScMT 3, and the three genes are successively involved in the molecular responses of Cu2+ stress in roots. When treated with Zn2+, the expression of ScMT 1 and ScMT 3 increased only in shoots and roots, respectively. The expression of ScMT 2-1-5 was up-regulated at the early stage and then suppressed in both shoots and roots. It suggests that ScMT 1 and ScMT 3 mainly function in shoots and roots, respectively, when exposed to Zn2+ stress. ScMT 2-1-5 was involved in the molecular responses of Cd2+ stress at the early stage. ScMT 1, ScMT 2-1-5, and ScMT 3 showed similar or complementary expression patterns in different tissues of sugarcane when exposed to heavy metals, which revealed the functional diversity of sugarcane MTs in detoxification and cellular redox regulation, and their spatiotemporal coordination in mitigating or even preventing tissue injury caused by excessive heavy metals. The results provide a basic information for further research on mechanisms in the synergistic enhancement of tolerance to heavy metals for MTs family genes in the highly polyploid sugarcane.

Metallic nanostructures can strongly absorb light through their plasmon excitations, whose nonradiative decay generates hot electron-hole pairs. When the metallic nanostructure is interfaced with a semiconductor, the spatial separation of hot carriers plays the central and decisive roles in photovoltaic and photocatalytic applications. In recent years, free-electron metals like Al have attracted tremendous attentions due to the much higher plasmon frequencies that could extend to the ultraviolet regime. Here, the plasmon excitations and charge separations at the Al-TiO

Plasmon-induced electron-hole separation at metal-semiconductor interfaces is an essential step in photovoltaics, photochemistry, and optoelectronics. Despite its importance in fundamental understandings and technological applications, the mechanism and dynamics of the charge separation under plasmon excitations have not been well understood. Here, the plasmon-induced charge separation between a Ag20 nanocluster and a TiO2(110) surface is investigated using time-dependent density functional theory simulations. It is found that the charge separation dynamics consists of two processes: during the first 10 fs an initial charge separation resulting from the plasmon-electron coupling at the interface and a subsequent charge redistribution governed by the sloshing motion of the charge-transfer plasmon. The interplay between the two processes determines the charge separation and leads to the inhomogeneous layer-dependent distribution of hot carriers. The hot electrons are more efficient than the hot holes in the charge injection, resulting in the charge separation. Over 40% of the hot electron-hole pairs are separated spatially from the interface. Finally, the second TiO2 layer receives the most net charges from the Ag nanocluster rather than the interfacial layer. These results reveal the mechanism and dynamics of the charge separation driven by the surface plasmon excitation and have broad implications in plasmonic applications.

Plasmonic nanoclusters can strongly absorb light energy and generate hot carriers, which have great potentials in photovoltaic and photocatalytic applications. A vital step for those plasmonic applications is the charge transfer at the metal–semiconductor interface. The effect of the light polarization on the charge transfer has not been theoretically investigated so far. Here, we take the Ag–TiO2 system as a model system to study the polarization effect using time-dependent density functional theory simulations. We find that the charge transfer is sensitive to the light polarization, which has its origin in the polarization-dependent hot carrier distributions. For the linearly polarized light, it shows a sine-square dependence on the polar angle, indicating that the charge transfer response to the linear polarization can be decomposed into components perpendicular and parallel to the interface. We also find that there exists directional charge transfer with a circular light polarization. Our results demonstrate that the light polarization can significantly affect the charge transfer behavior and, thus, offer a new degree of freedom to manipulate the plasmonic applications.

Silicon, one of the most prevalent elements in the soil, is beneficial for plant growth and defense against different stresses. The silicon transporter gene (Lsi) plays an important role in the uptake and transport of silicon in higher plants. In this study, a total of 32 Lsi genes, including 20 SsLsi in sugarcane wild species Saccharum spontaneum, 5 ShLsi in Saccharum hybrid cultivar R570 and 7 SbLsi in sugarcane related species Sorghum bicolor, were identified and classified into three groups. Bioinformatics analysis showed that instability, hydrophobicity, localization of cell membranes and vacuoles were the main features of the Lsi proteins. Whole genome and segmental duplication contributed to the main expansion of Lsi gene family. Collinearity analysis of the Lsi genes showed that S. spontanum and R570 had a collinear relationship with monocotyledonous plants S. bicolor and Oryza sativa, but not with dicotyledonous plants Arabidopsis thaliana and Vitis vinifera. The replicated Lsi genes were mainly subjected to strong selection pressure for purification. The diverse cis-regulatory elements in the promoter of SsLsi, ShLsi and SbLsi genes suggested that they were widely involved in the response of plants to various stresses and the regulation of the growth and development. Transcriptome data and real time quantitative PCR analysis showed that the Lsi genes exhibited different expression profiles in sugarcane tissues and under Sporisorium scitamineum, drought and cold stresses. In addition, the cDNA and genomic DNA sequences of ShLsi6 that was homologous to SsLsi1b gene was cloned from Saccharum hybrid cultivar ROC22. Transient expression analysis showed that, compared with the control, Nicotiana benthamiana leaves which overexpressed the ShLsi6 gene showed a high sensitivity after inoculation with tobacco pathogens Ralstonia solanacearum and Fusarium solani var. coeruleum. This study provides important information for further functional analysis of Lsi genes and resistant breeding in sugarcane.

Sugarcane, the main sugar crop harvested around the world, is sensitive to cold stress. miRNA plays an important role in plant response to abiotic stress. In order to discover the miRNAs that play a continuing role in sugarcane response to cold stress in a later period (2 d), four sugarcane small RNA libraries were constructed. In this study, a total of 144 miRNAs were identified. Among them, 32 miRNAs showed differential expression in two relatively cold tolerant and sensitive sugarcane cultivars (FN39 and ROC22). The expression tendency for ten randomly selected differentially expressed miRNAs and their predicted targets by qRT-PCR were consistent with those from sequencing data. To further investigate the miRNA role, ScmiR393 in sugarcane was selected and overexpressed in Arabidopsis. After a relatively long cold treatment, the over-expressed ScmiR393 Arabidopsis showed better growth than the wild type, and this phenomenon was supported by the higher anthocyanin and proline contents, lower MDA and H2O2 contents, and higher SOD, POD and CAT activities, as well as the induction of some cold resistant genes including CBFs. In addition, transcriptome analysis revealed that the overexpression of ScmiR393 inhibited the auxin signaling pathway by targeting TIR1, and this may also lead to ethylene signaling inhibition. Inhibited ethylene signaling may induce the cold-resistant genes and promote anthocyanin accumulation and bolting, eventually, the cold tolerance of Arabidopsis may be improved. This study contributes to the present sugarcane miRNA resource and shows an important role of ScmiR393 in plant response to cold stress.

Magnetism of graphene can be created by atomic defects, either hydrogen adsorption or single-carbon vacancy formation, owing to the unpaired $\ensuremath{\pi}$ electrons around the defects. Here we explore, based on rigorous first principles calculations, the possibility of voltage manipulation of two such types of $\ensuremath{\pi}$ magnetism in graphene via a scanning tunneling microscope tip. We find a remarkably different behavior. For the hydrogen, the magnetic moment can be switched on and off with voltage-induced doping, whereas, for the carbon vacancy, the spin splitting of the $\ensuremath{\pi}$ bands persists, almost independent of the extent of doping, due to the coupling between the $\ensuremath{\pi}$ and the $\ensuremath{\sigma}$ bonds. Furthermore, the local atomic structures near the vacancy can be reversibly manipulated by a coordination mechanism between an intermediate tip-defect distance and a moderate tip voltage, consequently leading to the reversal of spin polarization of the $\ensuremath{\pi}$ bands. Voltage control of the local magnetic states may open a new avenue for potential applications in spintronics.

The past decade has witnessed numerous discoveries of two-dimensional (2D) semimetals and insulators, whereas 2D metals were rarely identified. Borophene, a monolayer boron sheet, has recently emerged as a perfect 2D metal with unique electronic properties. Here we study collective excitations in borophene, which exhibit two major plasmon modes with low damping rates extending from the infrared to ultraviolet regime. The anisotropic 1D plasmon originates from electronic transitions of tilted Dirac cones in borophene, analogous to that in extreme doped graphene. These features enable borophene as an integrated platform of 1D, 2D, and Dirac plasmons, promising for directional polariton transport and broadband optical communication in next-generation optoelectronic devices.

In the present work, the coadsorption of the 4-(7-{10-[bis(4-hydroxy-phenyl)-amino]-anthracen-9-ylethynyl}-2-octyl-2H-benzotriazol-4-yl)-benzoic acid (TY6) dye and the chenodeoxycholic acid (CDCA) ...

Mosaic disease is a major viral disease that severely compromises sugar content and cane production. Among mosaic disease pathogens, Sorghum mosaic virus (SrMV) is the most prevalent one. To better understand the interaction mechanism between sugarcane and SrMV, samples of SrMV-infected and virus-free leaves of sugarcane cultivar ROC22 were deep sequenced and the sequencing data was confirmed by qRT-PCR. In total, 89,338 unigenes, 481 differentially expressed unigenes and 51 homologous sequences of Potyvirus host interactor (PHI) genes were obtained. The RNA-seq data implied that, the increase of SrMV replication from endoplasmic reticulum (ER) to chloroplast led to chloroplasts damage, following the initiation of differential expression of genes related to Ca2 +, ROS, cytokinin, auxin, and ethylene signaling, and also the transcription of some defense related genes. Among 51 PHIs, the upregulation of a calmodulin-related protein gene and an ethylene-inducible transcription factor gene in two SrMV-resistant and two SrMV-susceptible sugarcane cultivars under SrMV infection suggests that these two genes could be used as potential gene knockout targets for creating SrMV incompatible germplasm. Besides, based on its inverse expression pattern in the SrMV-resistant and -susceptible sugarcane cultivars, genes encoding heat shock protein 70, chloroplastic rieske Fe/S protein, reticulon homology domain protein and salicylic acid binding protein 3 might be used as the potential markers for identifying the resistance or susceptibility of sugarcane materials to SrMV. This study should help to understand the molecular mechanisms underlying SrMV-resistance of sugarcane cultivars.

It has been shown recently that the magnetic state of single-atom vacancy in graphene can be manipulated reversibly by mechanical deformation. Here, we investigate the possibility to flip the spin current of a model graphene device using nanomechanical distortion. Extensive first-principles calculations show that spin polarized currents can be altered by applying a shear distortion. The magnetic transitions in the central device, which is associated with the reversal of spin polarization of the π band of the vacancy state, lead to current flip with a spin filtering efficiency up to 17% (and a maximum change by 24% upon distortion). Our result opens the possibility to control spin transport properties in graphene and has potential applications in spintronics such as spin valves and spin transistors.

The ratoon stunting disease (RSD), caused by the bacterium Leifsonia xyli subsp. xyli (Lxx), is one of the most economically devastating diseases impacting sugarcane. RSD causes significant yield losses and variety degradation. Diagnosis of RSD is challenging because it does not exhibit any discernible internal and external symptoms. Moreover, the Lxx bacteria are very small and difficult to isolate, cultivate, and detect. In this study, conventional polymerase chain reaction (PCR), real-time quantitative PCR (RT-qPCR), and Lxx-loop-mediated isothermal amplification (Lxx-LAMP) were utilized to specifically detect the presence of Lxx pathogens in the juice from Lxx-infected sugarcane stalks and an Lxx-pMD18-T recombinant plasmid. The results showed that Lxx was a highly specific causal pathogen for RSD. All three techniques provided great reproducibility, while Lxx-LAMP had the highest sensitivity. When the DNA extract from Lxx-infected sugarcane juice was used as a template, Lxx-LAMP was 10 and 100 times more sensitive than RT-qPCR and conventional PCR, respectively. When the Lxx-pMD18-T recombinant plasmid was used as a template, Lxx-LAMP was as sensitive as RT-qPCR but was 10 times more sensitive than conventional PCR. Based on the Lxx-LAMP detection system established, adding 0.4 μM loop primers (LF/LP) can accelerate the reaction and reduce the total time required. In addition, the optimal amount of Bst DNA polymerase for Lxx-LAMP reactions was determined to be 6.0 U. The results provide technical support for the detection of RSD Lxx pathogen that will help manage sugarcane RSD.

It usually costs energy to create a surface, so to reduce the instability of a material, it is often desirable to reduce the surface area. However, it has been reported recently that the instability of lead halide perovskites, which are promising materials for high efficiency and low cost solar cells, can be improved by reducing the dimensions of the perovskites from the three-dimensional (3D) bulk to that of two-dimensional (2D) films. So far, there is a lack of general understanding about this unusual behavior, i.e., why a 2D slab cut out of the 3D bulk material could be more stable than the 3D material. Here, we carry out a systematic and comparative study on the thermodynamic stability of 2D and 3D perovskites using the first-principles method based on density functional theory. Taking CsPbBr3 and MAPbI3 as prototype examples, we show that the thermodynamic stability of the 2D perovskite originates from the asymmetric surface properties of this material: the AX-terminated 2D APbX3 are more stable than the PbX2-terminated 2D counterpart due to fewer surface dangling bonds. The MAI-terminated 2D MAPbI3 becomes even more stable than its 3D counterpart due to relaxation of the hydrogen bonds at the surface. Our results thus provide deep insights into the stability of 2D slabs versus 3D host materials, which shall be useful for improving the stability of perovskites and designing new 2D materials.

Exploring gate insulator materials for 2D transistors and their defect properties is of importance for device performance optimization. In this work, the structural and electronic properties of intrinsic vacancies in the CaF 2 single layer and its heterostructures with monolayer MoS 2 are investigated from first-principles calculations. V Ca introduces a shallow defect level close to the VBM, whereas V F introduces a deep level below the CBM. In both cases, spin polarization is observed. Overall, V F has a relatively lower formation energy than V Ca, except for the extreme Ca-rich case. Thus, V F should be dominant in CaF 2. The band offset between CaF 2 and MoS 2 is determined to be type-I, with large offsets at both the conduction band and valence band. With the presence of vacancies in CaF 2, the type-I band offset is preserved. The electron or hole on the defect states will transfer from CaF 2 to MoS 2 due to the large band offset, and spin polarization vanishes. Nevertheless, there are no defect states inside the gap or around the band edge of MoS 2, and the electronic properties of MoS 2 are almost intact. Compared with h-BN that has a small valence band offset with MoS 2 and could introduce in-gap defect states, CaF 2 can be a good candidate to serve as the dielectric layer of MoS 2-based transistors.

The effect of shear distortion on the vacancy induced magnetism in graphene is investigated using extensive first-principles calculations. It is found that shear distortion can lead to magnetic transition between two states with high and low magnetic moments. Such a transition is reversible and results from the breaking of the in-plane symmetry of the local atoms, which reverses spin polarization of the π bands of the vacancy states near the Fermi level and leads to the change of magnetic transition by 1 µB. This finding opens the possibility for nanomechanical control of graphene magnetism and has potential applications in spintronics and magnetic sensing.

We investigate a series of phenothiazine (PT)-based organic dyes by adopting different donors and different donor substitution positions as photosensitisers for application in dye-sensitised solar cells (DSSCs). First-principles calculations reveal systematic improvements of key parameters including light-harvesting efficiency, redox potential, electron injection and non-linear optical properties with donor substitutions. The non-planar structure also suppresses dye aggregation and reduces the rate of internal charge recombination. In particular, photosensitisers with combination of donor functional groups show outstanding performance on these key parameters. This study demonstrates that PT-based dyes with the studied donor groups could serve as excellent candidates of photosensitisers for future DSSC applications.

The surface plasmon resonance (SPR) of metal nanoparticles exhibits quantum behaviors as the size decreases owing to the transitions of quantized conduction electrons, but most studies are limited to the monotonous SPR blue-shift caused by off-resonant transitions. Here, we demonstrate the nonmonotonous SPR red-shift caused by resonant electron transitions and photocatalytic activity enhanced by the quantum plasmon resonance of colloidal gold nanoparticles. A maximal SPR wavelength and the largest photocatalytic activity are observed in the quantum regime for the first time for the gold nanoparticles with a diameter of 3.6 nm. Theoretical analysis based on a quantum-corrected model reveals the evolution of SPR with quantized electron transitions and well explains the nonmonotonous size-dependencies of the SPR wavelength and absorption efficiency. These findings have profound implications for the understanding of the quantum nature of the SPR of metal nanoparticles and their applications in areas ranging from photophysics to photochemistry.

Metallic nanocavities exhibit extremely high spectral sensitivity to geometrical variations and are promising for sensing applications. Here, the sensitivity of a cubic dimer cavity, to picometer gap variation, is analysed in a model, which takes into account the phase shift of scattering at the boundaries and the quantum tunnelling effect in the small gap limit. The resonance wavelengths are expressed in terms of the plasmon frequency, the medium dielectric function, and the geometry of the gap. The sensitivity of the resonance wavelength to the gap width variation is found to be as high as 1 nm pm−1. While the resonance wavelengths depend on the materials’ dielectric functions, the sensitivity is found to scale universally as a function of gap distance. In the sub-nanometer regime, electron tunnelling across the gap starts to suppress the plasmonic field, setting the limit of sensitivity of such a dimer cavity. The results given by the analytical model are complemented by numerical simulations using Comsol. Our model reveals the origin and universal behaviours of the sensitivity of the cavity plasmon and provides guidance for the design of new sensitive rulers at the picometer scale.

The plasmon opens up the possibility to efficiently couple light and matter at subwavelength scales. In general, the plasmon frequency, intensity, and damping are dependent on the carrier density. These dependencies, however, are disadvantageous for stable functionalities of plasmons and render fundamentally a weak intensity at low frequency, especially for the Dirac plasmon (DP) widely studied in graphene. Here we demonstrate a new type of DP, emerging from a Dirac nodal-surface state, which can simultaneously exhibit a density-independent frequency, intensity, and damping. Remarkably, we predict the realization of anomalous DP (ADP) in 1D topological electrides, such as Ba_{3}CrN_{3} and Sr_{3}CrN_{3}, by first-principles calculations. The ADPs in both systems have a density-independent frequency and high intensity, and their frequency can be tuned from terahertz to midinfrared by changing the excitation direction. Furthermore, the intrinsic weak electron-phonon coupling of anionic electrons in electrides affords an added advantage of low-phonon-assisted damping and hence a long lifetime of the ADPs. Our Letter paves the way to developing novel plasmonic and optoelectronic devices by combining topological physics with electride materials.

The stability of magnetic states is essential for potential spintronic applications. Here we report on the thermal stability of magnetic states of monovacancy graphene using ab initio molecular dynamics simulations. At room temperature, thermal fluctuations of the graphene lattice induce a rapid magnetic switching between two states with a high and low magnetic moment, indicating that due to the instability of the atomic structure of the vacancy, the associated magnetic moment is thermodynamically unstable. Lowering the temperature can significantly reduce the rate of the switching process and enhance the resident time on the high magnetic state. It stabilizes in the high magnetic state at as low as 30 K. Analyzing the atomic trajectories and the instant electronic structures confirms that these two magnetic states in MD simulations correspond to the magnetic and nonmagnetic states reported in the literatures. Such fluctuations of local magnetic moments are associated with the vertical displacement of the carbon atoms with the unsaturated dangling bond. This study reveals the dynamical correlation between atomic movement and the magnetic switching, and a comprehensive picture of vacancy magnetism in graphene. It has implications in graphene based spintronic devices.

Background Sugarcane (Saccharum spp. hybrids) is considered the most globally important sugar-producing crop and raw material for biofuel. Insect attack is a major issue in sugarcane cultivation, resulting in yield losses and sucrose content reductions. Stem borer (Diatraea saccharalis F.) causes serious yield losses in sugarcane worldwide. However, insect-resistant germplasms for sugarcane are not available in any collections all over the world, and the molecular mechanism of insect resistance has not been elucidated. In this study, cry1Ac transgenic sugarcane lines were obtained and the biological characteristics and transgene dosage effect were investigated and a global exploration of gene expression by transcriptome analysis was performed. Results The transgene copies of foreign cry1Ac were variable and random. The correlation between the cry1Ac protein and cry1Ac gene copies differed between the transgenic lines from FN15 and ROC22. The medium copy lines from FN15 showed a significant linear relationship, while ROC22 showed no definite dosage effect. The transgenic lines with medium copies of cry1Ac showed an elite phenotype. Transcriptome analysis by RNA sequencing indicated that up/down regulated differentially expressed genes were abundant among the cry1Ac sugarcane lines and the receptor variety. Foreign cry1Ac gene and endogenous borer stress-related genes may have a synergistic effect. Three lines, namely, A1, A5, and A6, were selected for their excellent stem borer resistance and phenotypic traits and are expected to be used directly as cultivars or crossing parents for sugarcane borer resistance breeding. Conclusions Cry1Ac gene integration dramatically improved sugarcane insect resistance. The elite transgenic offspring contained medium transgene copies. Foreign cry1Ac gene integration and endogenous borer stress-related genes may have a synergistic effect on sugarcane insect resistance improvement. Electronic supplementary material The online version of this article (10.1186/s12870-018-1536-6) contains supplementary material, which is available to authorized users.