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In the scene of paddy field rotary tillage, a real-time detection method of rotary tillage condition based on machine vision is proposed, and the quality of rotary tillage is evaluated by the index of residual stubble. The residual root stubble is selected as the research object, and the root stubble detection method based on the standard deviation of Y component in YCrCb space is proposed to determine the residual root stubble of soil after rotary tillage, which is divided into three levels: less root stubble, medium root stubble, and more root stubble. Finally, the accuracy of the algorithm is verified by field test and questionnaire survey. On the basis of manual evaluation, the accuracy rate of the working condition is 83.6 %, which provides a more accurate basis for the real-time adjustment of the control strategy for the unmanned operation of agricultural machinery in the field, and realizes the rotary tillage quality from qualitative evaluation to quantitative evaluation, and lays the foundation for the data of rotary tillage quality.

We propose the holographic reciprocity effect (HRE) to describe the relationship between the exposure duration (ED) and the growth rate of diffraction efficiency (GRoDE) in volume holographic storage. The HRE process is investigated experimentally and theoretically in order to avoid the diffraction attenuation. Herein, introducing the medium absorption, we present a comprehensive probabilistic model to describe the HRE. PQ/PMMA polymers are fabricated and investigated to reveal the influence of HRE on the diffraction characteristics through two recording approaches: pulsed exposure with nanosecond (ns) level and continuous wave (CW) exposure at the millisecond (ms) level. We obtain the holographic reciprocity matching (HRM) range of ED in PQ/PMMA polymers with 10−6~102 s level and improve the response time to microsecond (μs) order with no diffraction deficiency. This work can promote the application of volume holographic storage in high-speed transient information accessing technology.

Monolayer MoS2 has emerged as one of the most promising candidate materials for future semiconductor devices because of its fascinating physical properties and optoelectronic performance. Recently, the utilization of alkali metal compounds as promoters in CVD growth has been demonstrated to be a facile strategy for growing monolayer MoS2 and other 2D TMDs with large domain sizes. In this work, we systematically investigated the residues derived from alkali metal compounds and the spontaneous n-doping effect on monolayer MoS2 in alkali metal compound-promoted CVD growth. When using NaOH and other alkali metal compounds as promoters, it is found that the Raman peak of the A1g mode red shifted with a broadening width and the PL intensity of the A peak decreased with a red shift, which was attributed to the spontaneous n-doping effect during growth. Moreover, the growth using varying amounts of NaOH promoter suggests that the n-doping level could be controlled by the amount of promoter. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) showed the existence of cation-derived residues in the form of a Na-O cluster physiosorbed on top of monolayer MoS2, which was also confirmed by the transfer experiment. The NaOH treatment experiment and density functional theory (DFT) calculations demonstrate that sodium hydroxide clusters, which could be converted from a combination of Na-O clusters and water vapor, could produce an n-doping effect on monolayer MoS2. This study provides a facile route to controllably grow monolayer 2D materials with a desired doping level without further treatment.

In this work, we present a plasmonic platform capable of the enhanced electric field (E-field) intensity, tunable LSPR effect, and trapping nanoparticles in different configurations of Ag triangular nanoplates. Our nanostructures equip the higher structural anisotropy (larger aspect ratio, 10:1), which localize surface plasmons in the gap region and possess the great factor of E-field enhancement (~850). Tunable near-field enhanced hotspots of Ag nanoplates support different resonant modes from 350 to 1200 nm, and the distribution of electric field and trapping potential well can also be manipulated. The hotspots for dimer enhance the optical force (~3.2 nN) on 30-nm polystyrene nanoparticles with a power density as low as 1 mW/μm2, which shows brilliant trapping characteristics. The tetramer with higher periodic symmetry provides a deep potential well (~ $$1.3 \times {10^3}$$ kBT). It offers opportunities for the trapping and manipulating particles of nanoscale. And the nanogap structures pave a way for applications in surface-enhanced Raman scattering, surface-enhanced infrared absorption tunable biosensors.

The long-followed practice of using garlic cloves for garlic asexual reproduction has resulted in virus accumulation and genetic depression. Aerial bulbs, the preferred material for virus-free garlic seedling cultivation in vitro, undergo dormancy, but gibberellin can quickly break this state. In this study, exogenous GA3 was applied to dormant aerial bulbs and transcriptome sequencing was then performed using control and gibberellin-treated aerial bulbs. Genes differentially expressed in response to the gibberellin treatment were analyzed and screened and their relationship to GA3-induced dormancy break of aerial bulbs was explored. According to our results, exogenous GA3 was able to effectively break aerial bulb dormancy. Transcriptome sequencing uncovered 4931 and 74,636 genes that were respectively up- and down-regulated in response to gibberellin treatment. 37,957 differentially expressed genes were successfully assigned to KEGG pathways, among which the most DEGs were annotated in metabolism pathway (23,245 genes, accounting for 61.24%), followed by the genetic information processing pathway (9235 genes, accounting for 24.33%). More DEGs were enriched in spliceosome, ribosome, ribosome biogenesis in eukaryotes, and ubiquitin-mediated proteolysis pathways and the enrichment results were significant. In addition, carbohydrate and amino acid metabolism pathways are active. The significant DEGs related to calcium signaling, hormonal signaling, and transcription factors were screened out. Among them, the expression of DEGs related to hormonal signaling was consistent with the change of endogenous hormone content in aerial bulbs. Finally, the outcome of a qRT-PCR analysis was consistent with our transcriptome sequencing results, thus indicating that the latter was reliable.

In this paper, the dependence of random lasing properties on the gain volume in dye doped nematic liquid crystals was investigated. Because the pump beam was focused by a lens to excite the sample,...

Monolayer semiconducting two-dimensional (2D) materials are strongly emerging materials for exploring the spin-valley coupling effect and fabricating novel optoelectronic devices due to their unique structural symmetry and band structures. Due to their atomic thickness, their excitonic optical response is highly sensitive to the dielectric environment. In this work, we present a novel approach to reversibly modulate the optical properties of monolayer molybdenum disulfide (MoS2) via changing the dielectric properties of the substrate by laser irradiation and thermal annealing. We chose LiNbO3 as the substrate and recorded the PL spectra of monolayer MoS2 on LiNbO3 substrates with positive (P+) and negative (P-) ferroelectric polarities. A distinct PL intensity of the A peak was observed due to opposite doping by surface charges. Under light irradiation, the PL intensity of monolayer MoS2 on P+ Fe2O3-doped LiNbO3 gradually decreased with time due to the reduction of intrinsic p-doping, which originated from the drift of photo-excited electrons under a spontaneous polarization field and accumulation on the surface. The PL intensity was found to be restored by thermal annealing which could erase the charge redistribution. This study provides a strategy to reversibly modulate the optical properties of monolayer 2D materials on top of ferroelectric materials.

As an intrigued layered 2D semiconductor material, indium selenide (In2Se3) has attracted widespread attention due to its excellent properties. So far, the carrier dynamics of α-In2Se3 and β-In2Se3 are still lacking a comprehensive understanding, which is essential to enhancing the performance of In2Se3-based optoelectronic devices. In this study, we explored the ultrafast carrier dynamics in thin α-In2Se3 and β-In2Se3via transient absorption microscopy. For α-In2Se3 with a narrower bandgap, band filling and bandgap renormalization jointly governed the time evolution of the differential reflectivity signal, whose magnitude and sign at different delays were determined by the weights between the band filling and bandgap renormalization, depending on the carrier density. For β-In2Se3, whose bandgap is close to the probe photon energy, only positive differential reflectivity was detected, which was attributed to strong band filling effect. In both materials, the lifetime decreased and the relative amplitude of the Auger process increased, when the pump fluence was increased. These findings could provide further insights into the optical and optoelectronic properties of In2Se3-based devices.

This Letter proposes a random plasmonic laser in the metal–insulator–metal (MIM) structure, in which the dielectric core with gain is dispersed with circular dielectric nanoscatterers. The numerical results from finite-difference time-domain simulation indicate that scattering by the randomly distributed dielectric nanoscatterers in the MIM waveguide provides feedback to the random laser with surface plasmon. The design bypasses the requirement of a distributed feedback structure for the plasmonic waveguide-based nanolasers, which is challenging and expensive in fabrication. Additionally, the MIM structure makes this type of random laser easily applicable to nanoscale integrated photonic devices and circuits.

Utilizing determinant quantum Monte Carlo algorithm, the evolution of the

As monolayer graphene comprises only one single atomic layer, its physical and chemical properties could be easily tuned by the underlying substrate. However, it is still unknown how the distinct s...

Monolayer MoS

As an intrigued layered 2D semiconductor material, indium selenide (In

Monolayer semiconducting two-dimensional (2D) materials are strongly emerging materials for exploring the spin-valley coupling effect and fabricating novel optoelectronic devices due to their unique structural symmetry and band structures. Due to their atomic thickness, their excitonic optical response is highly sensitive to the dielectric environment. In this work, we present a novel approach to reversibly modulate the optical properties of monolayer molybdenum disulfide (MoS

Optical microscopy is believed to be an efficient method for identifying layer number of two-dimensional (2D) materials. However, since illuminants, cameras and their parameters are different from lab to lab, it is impossible to identify layer numbers merely by comparing a given optical image with standard or calculated images under standard conditions. Here we reported an image reconstruction method, converting raw optical images acquired by arbitrary illuminants and cameras into reconstructed images under the condition of specified illuminant and specified camera. After image reconstruction, the color differences of each layer number roughly equaled those calculated under the specified condition. By comparing the color differences in the reconstructed image with those calculated under the specified condition, the layer numbers of 2D materials in our lab and published papers, including MoS2, WS2, and WSe2, were unambiguously identified. This study makes optical microscopy a precise method to identify layer numbers of 2D materials on known substrates.

Light quality is an important environmental factor that drives photosynthesis and regulates plant growth and development. The purpose of this study was to investigate effects of light quality on sugar metabolism of tomato fruit. Tomato variety ‘Micro-Tom’ was used as the test material. After a 30-day cultivation period, seedlings were moved to an artificial climate chamber and grown under different light conditions: ratio of red and blue light, 1:1 (RB11), ratio of red and blue light, 3:1 (RB31), ratio of red and blue light, 5:1 (RB51), ratio of red and blue light, 7:1 (RB71), and white light as the control (CK). Fruit were harvested at the mature green, breaker, and ripe stages. The soluble sugar, total soluble solids, glucose, fructose, and sucrose contents in developing tomato fruit were highest under the RB31 condition. To further investigate effects of light quality on tomato fruit sugar metabolism, proteomic analysis using total proteins extracted from the CK and RB31-treated tomato fruit revealed that nine, three, and two proteins related to sugar metabolism were differentially accumulated between the CK and RB31-treated fruit at mature green, breaker, and ripe stages, respectively. Seven of them were up-regulated and the rest were down-regulated. The transcript abundances of these corresponding genes were analyzed by qRT-PCR. The expression levels of 12 genes were consistent with the protein abundances, but expression levels of xylose isomerase and l-iditol 2-dehydrogenase did not correlate with their protein abundances.

Polyphosphonates and phosphonate oligomers are a group of flame retardants that have gained much attention in recent years. Produced under the brand name Nofia, 1 they are now commercially used to flame retard different resins such as polyesters, polycarbonate, polyurethanes, epoxies, unsaturated polyesters, and polyureas. Phosphonates can be used as the single flame retardant but recently, it was also shown, that phosphonates can support other non-halogenated and halogenated flame retardants. FRX Polymers has been screening many systems including replacement of antimony trioxide as the synergist in flame retardant formulations that are based on halogenated flame retardants. The present article discusses examples of the use of phosphonates in reinforced thermoplastic and thermoset applications.

Modes and dispersion properties of nonlinear plasmonic waveguide made of a Kerr-type dielectric slab bounded by a graphene parallel plate have been studied. The influence of nonlinear coefficient on the dispersion relation was investigated. In the case of a wide nonlinear waveguide, three branches are always present in the dispersion relation, thus three modes exist in the waveguide. However, for a narrow nonlinear waveguide, only one branch exists in the dispersion relation for high values of the nonlinear coefficient. Moreover, the control of dispersion properties of nonlinear dielectric-graphene waveguide is achieved by adjusting the width of waveguide and nonlinear coefficient.

Monolayer MoS2, processing flexibility and remarkable physical properties derived from its direct bandgap feature, has been endowed to be one of the potential materials for practical applications s...

Utilizing determinant quantum Monte Carlo algorithm, the evolution of the d-wave pairing in the Hubbard model on the square lattice tuned by the periodically modulated hopping amplitudes is studied. The hopping amplitudes are homogeneous in the x ˆ -direction, while in the y ˆ -direction the hopping amplitudes are modulated with period P, where t y = t + d t , t y ′ = t − ( P − 1 ) d t , and the modulation period P equals 2, 3 and 4 lattice spacings. The latter two modulation periods are motivated by the observation of period-3 and period-4 stripe order in cuprate superconductors. For all the periods P, we find that the modulated hopping inhomogeneity enhances the d-wave pairing and an optimal inhomogeneity exists.

The dark diffusion enhancement process (DDEP) caused by photopolymerization during the pre-exposure of TI/PMMA (titanocene dispersed methyl methacrylate matrix) polymers was theoretically analyzed and experimentally investigated, revealing the holographic grating enhancement of TI/PMMA polymers in the post-exposure process without additional operations. The diffusion of photo-initiators and photoproducts dominated the grating enhancement process after exposure. We adopted two pre-exposure methods, long-time (second level) and short-time (millisecond level) laser exposure, at 532 nm, to investigate the DDEP during the post-exposure process. A five-fold enhancement in grating strength was achieved in consecutive long-time pre-exposures, while a two-fold grating development was examined after short-time exposure. Additionally, the exposure durations and repetition rates influenced the grating increment of the DDEP. This study provided a basis for the feasibility of holographic application in TI/PMMA photopolymers via the dark diffusion effect.

Tunable polarizing direction of random lasing emission by an applied electric field which radiated from the lateral end face of homogeneously aligned, dye-doped nematic liquid crystal (NLC) cell was demonstrated for the first time, to the best of our knowledge. The lasing emission was partially polarized in the direction along the director of the NLC without the applied electric field. By tuning the applied electric field, the NLC director could be rotated to arbitrary direction from homogeneous to homeotropic alignment, resulting in the polarizing direction of lasing emission to any direction from parallel to perpendicular to the substrate surface in the end face.

Background: Garlic (Allium sativum L.) has high medical and edible value, but is prone to producing green pigment during storage, which seriously affects product quality. Herein, we found multiple metabolic pathways involved in green pigment formation by analyzing the transcriptome and proteome changes of garlic stored at 4 °C for 0 day (DS0), 10 days (DS1), 15 days (DS2) and 40 days (DS3). Results: In this work, we found that porphobilinogen is a precursor of garlic green pigment and the citrate cycle (TCA cycle) can promote the formation of garlic green pigment by increasing the content of porphobilinogen. The salicylic acid (SA) inhibits garlic greening, whereas the lignin synthesis pathway positively correlates with greening. In addition to the above metabolic pathways, other pathways may be associated with the formation of garlic’s green pigment, such as glycolysis/gluconeogenesis, pyruvate metabolism and fatty acid metabolism. It has been reported that pyruvate and amino acids play a role in garlic greening, which were also demonstrated in this study. Conclusion: our results have important implications for understanding the mechanism of green pigment formation in garlic.

BackgroundLight is the main source of energy and, as such, is one of the most important environmental factors for plant growth, morphogenesis, and other physiological responses. MicroRNAs (miRNAs) are endogenous non-coding RNAs that contain 21–24 nucleotides (nt) and play important roles in plant growth and development as well as stress responses. However, the role of miRNAs in the light response is less studied. We used tomato seedlings that were cultured in red light then transferred to blue light for 2 min to identify miRNAs related to light response by high-throughput sequencing.ResultsA total of 108 known miRNAs and 141 predicted novel miRNAs were identified in leaf samples from tomato leaves treated with the different light qualities. Among them, 15 known and 5 predicted novel miRNAs were differentially expressed after blue light treatment compared with the control (red light treatment). KEGG enrichment analysis showed that significantly enriched pathways included zeatin biosynthesis (ko00908), homologous recombination (ko03440), and plant hormone signal transduction (ko04075). Zeatin biosynthesis and plant hormone signal transduction are related to plant hormones, indicating that plant hormones play important roles in the light response.ConclusionOur results provide a theoretical basis for further understanding the role of miRNAs in the light response of plants.

We provide a simple method for accurately interface angle sensing using the spin Hall effect of light (SHEL) with minimum observable angles of 2.4 × 10–5 rad and 1.2 × 10–6 rad for the azimuth angle and pitch angle, respectively.

CH3NH3PbI3 (MAPbI3) exhibits distinctive properties for applications in photovoltaics, light emitting devices, photodetectors, and fuel cells. The working temperature of an optoelectronic device affects the photophysical properties of the active material, which is closely related to the device performance. In MAPbI3, these properties are intimately connected with its crystalline structure which is temperature dependent. Here, we study the photoluminescence (PL) behavior of MAPbI3 microwires (MWs) under recursive tetragonal-to-cubic and cubic-to-tetragonal phase transitions induced by temperature cycles from 40 °C (tetragonal phase) to 80 °C (cubic phase). MWs emission exhibited an initial redshift in wavelength by increasing the temperature from the tetragonal to the cubic phase, but after several thermal cycles, this trend reversed and the emission blueshifted. In both phases independently, the emission blueshifted and became stronger with increasing the cycles. The results indicate a thermal cycling-dependent PL and a gradual crystalline structure deformation due to a reiterated change in the MWs lattice, which implies variation in the electronic bandgap along the heating–cooling process. The alteration of the electronic band structure was corroborated by thermal cycling-reflectance measurements. The awareness behavior of material properties upon phase transitions and temperature fluctuations is of great importance for the optimization of optoelectronic devices.

All-dielectric metasurfaces offer remarkable properties including high efficiency and flexible control of the optical response. However, extreme, narrow bandwidth is a limitation that lowers applicability of these structures in photonic sensing applications. In this work, we numerically design and propose a switchable quarter-wave plate by hybridizing an all-dielectric metasurface with graphene. By using a single layer of graphene between a highly refractive index silicon and a silica substrate, the transmissive resonance is enhanced and broadened. Additionally, integrating graphene with silicon effectively modulates the Q-factor and the trapped magnetic modes in the silicon. A stable birefringence output is obtained and manipulated through the structure dimensions and the Fermi energy of graphene. A 95% polarization conversion ratio is achieved through converting linearly polarized light into circularly polarized light, and a 96% ellipticity ratio is obtained at the resonance wavelength. The structure is compact and has an ultrathin design thickness of 0 . 1 λ , in the telecommunication region. The above properties are essential for integration into photonic sensing devices and the structure has potential for compatibility with the CMOS devices.

In-plane anisotropy, as one of the most intriguing properties of newly rediscovered 2D black phosphorus (BP), supplies another degree of freedom to design novel optical and optoelectronic devices. Here, the optical in-plane anisotropy of few-layer BP was directly visualized and studied by scanning polarization modulation microscopy (SPMM). The polarization analysis and experiment showed that the SPMM signal was dependent on the polarization angle of the laser beam in a sinusoidal way, by which the crystallographic orientation of BP was determined. The differential reflectance (ΔR = Rzz – Rac) showed the excitation wavelength and thickness dependence, which was well explained by considering the anisotropic multireflection effect. The intrinsic anisotropic complex refractive indices (n + iκ) were also derived on the basis of the Fresnel equation.

Conventional all-dielectric metasurfaces show remarkable properties including high efficiency and tunability of the optical response. However, extreme narrow bandwidth is a limitation that reduce their application in the photonic sensor devices. In this work, an efficient hybrid silicon-graphene metasurface is numerically proposed and designed. Through the sandwiched graphene layer, the structure shows unique quarter-wave properties, tunable through the dimensions of silicon, the Fermi energy of graphene, and an external gate voltage. Dynamic tuning is achieved by reversing the gate voltage: circular polarization state is switched between the right- and the left-handed states by reversing the gate voltage. A 95% polarization conversion ratio and a 96% ellipticity ratio are obtained while converting linearly polarized light into circularly polarized light in the near infrared. Additionally, by integrating graphene with silicon, the Q-factor and the trapped magnetic modes in the silicon are effectively modulated. The structure is compact and has an ultrathin design thickness of ∼0.1 λ, in the telecommunication wavelength. The above properties are essential for integration into photonic sensing devices and for compatibility with the CMOS devices.

Self-assembled organic-inorganic CH3NH3PbI3 perovskite microwires (MWs) upon humidity exposure along several weeks were investigated by photoluminescence (PL) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). We show that, in addition to the common perovskite decomposition into PbI2 and the formation of a hydrated phase, humidity induced a gradual PL redshift at the initial weeks that is stabilized for longer exposure (~ 21 nm over the degradation process) and an intensity enhancement. Original perovskite Raman band and XRD reflections slightly shifted upon humidity, indicating defects formation and structure distortion of the MWs crystal lattice. By correlating the PL, Raman, and XRD results, it is believed that the redshift of the MWs PL emission was originated from the structural disorder caused by the incorporation of H2O molecules in the crystal lattice and radiative recombination through moisture-induced subgap trap states. Our study provides insights into the optical and structural response of organic-inorganic perovskite materials upon humidity exposure.

The structures, circular dichroism (CD) spectra and nonlinear optical (NLO) responses of a series of inorganic double-helix chains, PnLin (n = 6–12), have been investigated using the quantum chemistry method. P–P and P–Li interactions play a major role in stabilizing double-helix chains. The distinctive CD spectra of the double-helix frameworks (namely, a sharp negative CD band at short-wavelength region and a positive CD band at long-wavelength region) become obvious with increasing number of PLi units. The NLO response augments with the length of the double-helix chains, and the contribution of the axial component along the chain direction gradually becomes crucial simultaneously. Synergistic effects, a decrease of crucial electronic transition energies and charge transfer excitation give rise to enhanced NLO responses. In particular, the electronic transitions from the highest occupied molecular orbital to the lowest unoccupied molecular orbital make significant contributions not only to the positive CD bands in the long-wavelength region, but also to the NLO responses of the double-helix PnLin (n = 6–12) chains.