Ultra-high Q-factor quasi-BIC BaTiO3 metasurface for electro-optic modulation.

Metasurfaces play a crucial role in trapping electromagnetic waves with specific wavelengths, serving as a significant platform for enhancing light-matter interactions. In all kinds of dynamic modulation metasurfaces, electro-optic modulation metasurfaces have attracted much attention due to its advantages of fast, stable and high efficiency. In order to respond to the extremely weak refractive index change of the electro-optical effect of the materials, the metasurfaces are required to support optical signals with high Q values. The quasi-bound state in the continuum (Q-BIC) is often used to enhance the light-field modulation capability of metasurfaces and to improve the modulation sensitivity of electro-optic modulators due to its ability to generate high Q-factor resonances. However, the design of an electro-optic modulation metasurface that facilitates the application of voltage and achieves modulation efficiency of nearly 100% is still in urgent need of development. In this study, single-crystal BTO metasurfaces are modeled using finite-difference time-domain method, and the structural symmetry is broken to introduce a Q-BIC resonance to generate a high Q-factor optical signal of 2.45 × 104 for high-depth electro-optic modulation. By simulating an applied electric field of 143 V/mm on the metasurface, a slight refractive index change of BTO of 8 × 10-4 was produced, leading to an electro-optical intensity modulation depth of 100%. Furthermore, the nanostructure of the metasurface was carefully designed to facilitate nano-fabrication and voltage application, and it is ideal for the development of low-power, CMOS-compatible, and miniaturized electro-optic modulation devices. Although the results of this study are based on simulations, they provide a crucial theoretical basis and guidance for the realization of efficient and realistic design of dynamic metasurfaces.

Fault-Tolerant Control of Autonomous Underwater Vehicle Actuators Based on Takagi and Sugeno Fuzzy and Pseudo-Inverse Quadratic Programming under Constraints.

Autonomous Underwater Vehicles (AUVs) play a significant role in ocean-related research fields as tools for human exploration and the development of marine resources. However, the uncertainty of the underwater environment and the complexity of underwater motion pose significant challenges to the fault-tolerant control of AUV actuators. This paper presents a fault-tolerant control strategy for AUV actuators based onTakagi and Sugeno (T-S) fuzzy logic and pseudo-inverse quadratic programming under control constraints, aimed at addressing potential actuator faults. Firstly, considering the steady-state performance and dynamic performance of the control system, a T-S fuzzy controller is designed. Next, based on the redundant configuration of the actuators, the propulsion system is normalized, and the fault-tolerant control of AUV actuators is achieved using the pseudo-inverse method under thrust allocation. When control is constrained, a quadratic programming approach is used to compensate for the input control quantity. Finally, the effectiveness of the fuzzy control and fault-tolerant control allocation methods studied in this paper is validated through mathematical simulation. The experimental results indicate that in various fault scenarios, the pseudo-inverse combined with a nonlinear quadratic programming algorithm can compensate for the missing control inputs due to control constraints, ensuring the normal thrust of AUV actuators and achieving the expected fault-tolerant effect.

Tuneable Schottky contact of MoSi2N4/TaS2 van der Waals heterostructure.

The two-dimensional MoSi2N4 monolayer is an emerging semiconductor material that offers considerable promise due to its ultra-thin profile, tuneable mechanical properties, excellent optoelectronic properties and exceptional environmental stability. The van der Waals (vdW) heterostructure formed by stacking such two-dimensional monolayers has demonstrated superior performance across various domains. In this study, a vdW heterostructure combining the two-dimensional MoSi2N4 and TaS2 monolayers is examined using first-principles density functional theory. In its ground state, this van der Waals heterostructure establishes an ohmic contact with an exceptionally low potential barrier height. By modulating the vdW heterostructure with an applied electric field of -0.1 V/Å and under vertical stress, we discovered that MoSi2N4 and TaS2 can transition from an ohmic contact to a p-type Schottky with an ultra-low Schottky barrier height (SBH). Our observations may give valuable insights for designing reconfigurable, tuneable Schottky nano-devices with enhanced electronic and optical properties based on MoSi2N4/TaS2.

A platform for integrated spectrometers based on solution-processable semiconductors.

Acquiring real-time spectral information in point-of-care diagnosis, internet-of-thing, and other lab-on-chip applications require spectrometers with hetero-integration capability and miniaturized feature. Compared to conventional semiconductors integrated by heteroepitaxy, solution-processable semiconductors provide a much-flexible integration platform due to their solution-processability, and, therefore, more suitable for the multi-material integrated system. However, solution-processable semiconductors are usually incompatible with the micro-fabrication processes. This work proposes a facile and universal platform to fabricate integrated spectrometers with semiconductor substitutability by unprecedently involving the conjugated mode of the bound states in the continuum (conjugated-BIC) photonics. Specifically, exploiting the conjugated-BIC photonics, which remains unexplored in conventional lasing studies, renders the broadband photodiodes with ultra-narrowband detection ability, detection wavelength tunability, and on-chip integration ability while ensuring the device performance. Spectrometers based on these ultra-narrowband photodiode arrays exhibit high spectral resolution and wide/tunable spectral bandwidth. The fabrication processes are compatible with solution-processable semiconductors photodiodes like perovskites and quantum dots, which can be potentially extended to conventional semiconductors. Signals from the spectrometers directly constitute the incident spectra without being computation-intensive, latency-sensitive, and error-intolerant. As an example, the integrated spectrometers based on perovskite photodiodes are capable of realizing narrowband/broadband light reconstruction and in-situ hyperspectral imaging.

Surface-Ligand-Modified CdSe/CdS Nanorods for High-Performance Light-Emitting Diodes.

Colloidal nanocrystals (NCs) play an important role in the field of optoelectronic devices such as photovoltaic cells, photodetectors, and light-emitting diodes (LEDs). The properties of NC films are strongly affected by ligands attached to them, which constitute a barrier for charge transport between adjacent NCs. Therefore, the method of surface modification by ligand exchange has been used to improve the electrical conductivity of NC films. However, surface modification to NCs in LEDs can also affect emission characteristics. Among NCs, nanorods have unique properties, such as suppression of nonradiative Auger recombination and linearly polarized light emission. In this work, CdSe/CdS nanorods (NRs) were prepared by the hot injection method. To increase the charge transport into CdSe/CdS NRs, we adopted ligand modification to CdSe/CdS NRs. Using this technique, we could shorten the injection barrier length between CdSe/CdS NRs and adjacent layers. It leads to a more balanced charge injection of electron/hole and a greatly increased current efficiency of CdSe/CdS NR-LEDs. In the NR-LEDs, the ligand exchange boosted the electroluminance, reaching a sixfold increase from 848 cd/m2 of native surfactants to 5600 cd/m2 of the exchanged n-octanoic acid ligands at 12 V. The improvement of CdSe/CdS NR-LED performance is closely correlated to the efficient control of charge balance via ligand modification strategy, which is expected to be indispensable to the future NR-LED-based optoelectronic system.

Bulk Photovoltaic Current Mechanisms in All-Inorganic Perovskite Multiferroic Materials.

After the discovery of bulk photovoltaic effect more than half a century ago, ferro-electrical and magneto-optical experiments have provided insights into various related topics, revealing above bandgap open voltages and non-central symmetrical current mechanisms. However, the nature of the photon-generated carriers responses and their microscopic mechanisms remain unclear. Here, all-inorganic perovskite Bi0.85Gd0.15Fe1-xMnxO3 thin films were prepared by a sol-gel process and the effects of Gd and Mn co-doped bismuth ferrites on their microtopography, grain boundries, multiferroic, and optical properties were studied. We discovered a simple "proof of principle" type new method that by one-step measuring the leakage current, one can demonstrate the value of photo generated current being the sum of ballistic current and shift current, which are combined to form the so-called bulk photovoltaic current, and can be related to the prototype intrinsic properties such as magneto-optical coupling and ferroelectric polarization. This result has significant potential influence on design principles for engineering multiferroic optoelectronic devices and future photovoltaic industry development.

DNA-enabled fluorescent-based nanosensors monitoring tumor-related RNA toward advanced cancer diagnosis: A review.

As a burgeoning non-invasive indicator for reproducible cancer diagnosis, tumor-related biomarkers have a wide range of applications in early cancer screening, efficacy monitoring, and prognosis predicting. Accurate and efficient biomarker determination, therefore, is of great importance to prevent cancer progression at an early stage, thus reducing the disease burden on the entire population, and facilitating advanced therapies for cancer. During the last few years, various DNA structure-based fluorescent probes have established a versatile platform for biological measurements, due to their inherent biocompatibility, excellent capacity to recognize nucleic and non-nucleic acid targets, obvious accessibility to synthesis as well as chemical modification, and the ease of interfacing with signal amplification protocols. After decades of research, DNA fluorescent probe technology for detecting tumor-related mRNAs has gradually grown to maturity, especially the advent of fluorescent nanoprobes has taken the process to a new level. Here, a systematic introduction to recent trends and advances focusing on various nanomaterials-related DNA fluorescent probes and the physicochemical properties of various involved nanomaterials (such as AuNP, GO, MnO2, SiO2, AuNR, etc.) are also presented in detail. Further, the strengths and weaknesses of existing probes were described and their progress in the detection of tumor-related mRNAs was illustrated. Also, the salient challenges were discussed later, with a few potential solutions.

Dual-wavelength switchable single-mode lasing from a lanthanide-doped resonator.

The development of multi-wavelength lasing, particularly with the wavelength tuning in a wide spectral range, is challenging but highly desirable for integrated photonic devices due to its dynamic switching functionality, high spectral purity and contrast. Here, we propose a general strategy, that relies on the simultaneous design on the electronic states and the optical states, to demonstrate dynamically switchable single-mode lasing spanning beyond the record range (300 nm). This is achieved through integrating the reversely designed nanocrystals with two size-mismatched coupled microcavities. We show an experimental validation of a crosstalk-free violet-to-red single-mode behavior through collective control of asymmetric excitation and excitation wavelength. The single-mode action persists for a wide power range, and presents significant enhancement when compared with that in the microdisk laser. These findings enlighten the reverse design of luminescent materials. Given the remarkable doping flexibility, our results may create new opportunities in a variety of frontier applications.

Ultralarge anti-Stokes lasing through tandem upconversion.

Coherent ultraviolet light is important for applications in environmental and life sciences. However, direct ultraviolet lasing is constrained by the fabrication challenge and operation cost. Herein, we present a strategy for the indirect generation of deep-ultraviolet lasing through a tandem upconversion process. A core-shell-shell nanoparticle is developed to achieve deep-ultraviolet emission at 290 nm by excitation in the telecommunication wavelength range at 1550 nm. The ultralarge anti-Stokes shift of 1260 nm (~3.5 eV) stems from a tandem combination of distinct upconversion processes that are integrated into separate layers of the core-shell-shell structure. By incorporating the core-shell-shell nanoparticles as gain media into a toroid microcavity, single-mode lasing at 289.2 nm is realized by pumping at 1550 nm. As various optical components are readily available in the mature telecommunication industry, our findings provide a viable solution for constructing miniaturized short-wavelength lasers that are suitable for device applications.

A Data-Driven Scheme for Fault Detection of Discrete-Time Switched Systems.

This paper is concerned with the fault detection issue for a class of discrete-time switched systems via the data-driven approach. For the fault detection of switched systems, it is inevitable to consider the mode matching problem between the activated subsystem and the executed residual generator since the mode mismatching may cause a false fault alarm in all probability. Frequently, studies assume that the switching laws are available to the residual generator, by which the residual generator keeps the same mode as the system plant and then the mode mismatching is excluded. However, this assumption is conservative and impractical because many switching laws are hard to acquire in practical applications. This work focuses on the case of switched systems with unavailable switching laws. In view of the unavailability of switching information, the mode recognition is considered for the fault detection process and meanwhile, sufficient conditions are presented for the mode distinguishability. Moreover, a novel decision logic for the fault detection is proposed, based on which new algorithms are established for the data-driven realization. Finally, a benchmark case on a three-tank system is used to illustrate the feasibility and usefulness of the obtained results.

Achieving Circularly Polarized Surface Emitting Perovskite Microlasers with All-Dielectric Metasurfaces.

Micro- and nanolasers are miniaturized light sources with great potential in optical imaging, sensing, and communication. While various micro- and nanolasers have been synthesized, they are mostly linearly polarized and thus strongly restricted in many new applications, e.g., chiral resolution in synthetic chemistry, cancerous tissue imaging, information storage, and processing. Herein, we experimentally demonstrate the circularly polarized surface emitting perovskite lasers by integrating the as-grown perovskite microcrystals with an all-dielectric metalens. The perovskite microcrystal serves as an optical microcavity and produces linearly polarized laser emission, which is collected by a geometric phase based TiO2 metalens. The left-handed circularly polarized components are collimated by the metalens into a directional laser beam with a divergent angle of <0.9°, whereas the right-handed components are strongly diverged by the same metalens. Consequently, the right-handed circularly polarized components are filtered out, and perovskite lasers with high directionality and pure circular polarization have been experimentally realized.

A composite nanocarrier to inhibit precipitation of the weakly basic drug in the gastrointestinal tract.

For weakly basic drugs, the sharp decrease of drug solubility and the following drug precipitation after drugs transferring from the gastric fluid to the intestinal fluid in the gastrointestinal (GI) tract is a main reason for the poor oral bioavailability of drugs. Here, an anticoagulant dabigatran etexilate (DE) was used as a model drug, and a composite nanocarrier system of DE was developed to improve the drug dissolution by decreasing the drug leakage in the stomach and inhibiting the drug precipitation in the intestinal tract. With the encapsulation of drugs in nanocarriers, the precipitation percentage of DE in composite nanocarriers was 22.25 ± 3.88% in simulated intestinal fluid, which was far below that of the commercial formulation. Moreover, the relative bioavailability of DE-loaded composite nanocarriers (456.58%) was greatly enhanced and the peak of its activated partial thromboplastin time was also significantly prolonged (p < .01) compared with the commercial formulation, indicating that the anticoagulant effect of DE was effectively improved. Therefore, the designed composite nanocarrier system of DE presents great potentials in improving the therapeutic efficiency and expanding the clinical applications of poorly water-soluble weakly basic drugs.

All-dielectric metasurface for high-performance structural color.

The achievement of structural color has shown advantages in large-gamut, high-saturation, high-brightness, and high-resolution. While a large number of plasmonic/dielectric nanostructures have been developed for structural color, the previous approaches fail to match all the above criterion simultaneously. Herein we utilize the Si metasurface to demonstrate an all-in-one solution for structural color. Due to the intrinsic material loss, the conventional Si metasurfaces only have a broadband reflection and a small gamut of 78% of sRGB. Once they are combined with a refractive index matching layer, the reflection bandwidth and the background reflection are both reduced, improving the brightness and the color purity significantly. Consequently, the experimentally demonstrated gamut has been increased to around 181.8% of sRGB, 135.6% of Adobe RGB, and 97.2% of Rec.2020. Meanwhile, high refractive index of silicon preserves the distinct color in a pixel with 2 × 2 array of nanodisks, giving a diffraction-limit resolution.

An ultra-sensitive T 2-weighted MR contrast agent based on Gd3+ ion chelated Fe3O4 nanoparticles.

An ultra-sensitive T 2-weighted MR imaging contrast agent was prepared based on Fe3O4 nanoparticles and Gd3+ ions (Fe3O4@Gd). Amino modified Fe3O4 nanoparticles were conjugated to diethylenetriamine pentaacetic acid, and finally coordinated with Gd3+ ions. The nanoparticles had a uniform morphology with a size of 100 nm and a Gd/Fe mass ratio of 1/110. The r 2 (transverse relaxivity) of the Fe3O4 nanoparticles increased from 131.89 mM-1 s-1 to 202.06 mM-1 s-1 after coordination with Gd3+ ions. MR measurements showed that the aqueous dispersion of Fe3O4@Gd nanoparticles had an obvious concentration-dependent negative contrast enhancement. Hepatoma cells were selected to test the cytotoxicity and MR imaging effect. The application of Fe3O4@Gd nanoparticles as contrast agents was also exploited in vivo for T 2-weighted MR imaging of rat livers. All the results showed the effectiveness of the nanoparticles in MR diagnosis.

Stretchable All-Dielectric Metasurfaces with Polarization-Insensitive and Full-Spectrum Response.

Mechanical stretching has been an effective way to achieve widely tunable optical response in artificial nanostructures. However, the typical stretchable optical devices produce exactly the reverse effects for two orthogonal linear polarizations, significantly hindering their practical applications in many emerging systems. Herein, we demonstrate an approach for a mechanically tunable all-dielectric metasurface with polarization insensitivity and full-spectrum response in the visible range from 450 to 650 nm. By embedding a TiO2 metasurface in a polydimethylsiloxane substrate and stretching it in one direction, we find that the distinct reflection colors of two orthogonal linear polarizations can be tuned across the entire visible spectrum simultaneously. Encryption and display of information have also been realized with the same technique. The corresponding calculations show that the spectral responses of light with polarizations perpendicular and parallel to the strain are determined by two different mechanisms, that is, the near-field mutual interaction and the grating effects. This research shall shed light on stretchable and wearable photonics.

Incipient winding fault detection and diagnosis for squirrel-cage induction motors equipped on CRH trains.

Stator/rotor winding faults are the common faults in squirrel-cage induction motor systems, which motivates the study of incipient fault detection and isolation (IFDI) to improve the safety and reliability of CRH (China Railway High-speed) trains. In this paper, a dynamic model for squirrel caged induction motor in d-q coordinate system is established firstly, further, the models and characteristics of incipient broken-rotor-bar fault and turn-to-turn short fault are analyzed. After that, a novel robust diagnosis design is proposed for the possible incipient stator/rotor winding faults. Experimental analyses show that the detection and isolation scheme designed in this paper provides high sensitivity and accurate isolation to incipient winding faults.

Effectiveness of theme based intervention model on students’ vision literacy and status / 中国学校卫生

Objective@#To explore the effectiveness eye caring theme based intervention model in the improvement of students’ vision, and to provide a systematic method for pupils’ visual intervention.@*Methods@#A total of 965 students in the same grade of the three schools were divided into intervention group(482) and control group(483) at a 1∶1 ratio match. The intervention group received a one year intervention through the design of the series of eye caring theme activities, and the control group did not receive any intervention.@*Results@#The mean values of visual related knowledge literacy improvement in the intervention group and the control group were 7.08 and 2.18, respectively, with a significant difference( t =92.18, P <0.05); The mean values of improvement of vision related belief literacy in the intervention group and the control group were 7.88 and 4.57, respectively, and the difference was statistically significant( t =45.57, P <0.05); The mean values of visual related behavior literacy improvement in the intervention group and the control group were 17.41 and 2.21. The differences were statistically significant( t =117.37, P <0.05); The mean values of total vision improvement in the intervention group and the control group were 10.80 and 2.99, respectively, and the differences were statistically significant( t =87.74, P <0.05); The mean values of the parents’ improvement in children’s vision health care in the intervention group and the control group were 13.33 and 0.80, respectively, and the difference was statistically significant( t =128.76, P <0.05); The mean values of visual acuity reduction in the intervention group and the control group were 0.07 and 0.71, respectively, and the differences were statistically significant( t =128.00, P <0.05).@*Conclusion@#Theme based intervention can improve students’ visual literacy, especially visual behavior literacy, and can effectively slow down the deterioration of students’ vision.

TiO2 metasurfaces: From visible planar photonics to photochemistry.

TiO2 metasurfaces have been intensively studied in the past few years. To date, the TiO2 metadevices only used their high reflective index (n). The controllable light extinction coefficient (k) of TiO2 has not been exploited yet. Here, we converted TiO2 metasurfaces to black TiO2 metasurfaces and explored their new opportunities in photochemistry. A complementary metal oxide semiconductor (CMOS)-compatible technique has been developed to reversibly and precisely control the absorption of TiO2 metasurfaces without spoiling their internal nanostructures. Consequently, two types of black TiO2 metasurfaces were realized for photochemical experiments. The metasurface with an ultrawide absorption band can substantially enhance the white light absorption and accelerate the solar-based photochemistry process by a factor of 18.7. The other metasurface with an absorption band of <20 nm only responded to the resonant wavelengths, making the photochemistry process capable of being monitored in real time. In addition, the reversible switch between normal and black states makes TiO2 metasurfaces suitable for dynamic metadevices as well.

Mass-Manufactural Lanthanide-Based Ultraviolet B Microlasers.

Lanthanide (Ln3+ )-based ultraviolet B (UVB) microlasers are highly desirable for diagnostics and phototherapy. Despite their progress, the potential applications of UVB microlasers are strongly hindered by their low optical gain, weak light confinements, and poor device repeatability. Herein, a novel all-in-one approach to solve the above limitations and realize mass-manufactural UVB microlasers is reported. The gain coefficient at 289 nm is improved from two aspects, i.e., the enhanced absorption via LiYbF4 :Tm(1mol%)@LiYbF4 @LiLuF4 core-shell-shell nanocrystals and the suppression of competitive ultraviolet emissions. Consequently, by spin-coating the solution onto a patterned SiO2 substrate, high-quality Ln3+ -based microdisks are formed by self-assembly on each SiO2 pillar and UVB whispering-gallery-mode lasers are realized. The resulted lasing threshold is an order of magnitude smaller than the shortest deep-ultraviolet emission at 310.5 nm. Importantly, the lasing wavelengths and mode numbers of UVB lasers are highly controllable and repeatable, making them suitable for mass production for the first time.

Multiple incipient sensor faults diagnosis with application to high-speed railway traction devices.

This paper deals with the problem of incipient fault diagnosis for a class of Lipschitz nonlinear systems with sensor biases and explores further results of total measurable fault information residual (ToMFIR). Firstly, state and output transformations are introduced to transform the original system into two subsystems. The first subsystem is subject to system disturbances and free from sensor faults, while the second subsystem contains sensor faults but without any system disturbances. Sensor faults in the second subsystem are then formed as actuator faults by using a pseudo-actuator based approach. Since the effects of system disturbances on the residual are completely decoupled, multiple incipient sensor faults can be detected by constructing ToMFIR, and the fault detectability condition is then derived for discriminating the detectable incipient sensor faults. Further, a sliding-mode observers (SMOs) based fault isolation scheme is designed to guarantee accurate isolation of multiple sensor faults. Finally, simulation results conducted on a CRH2 high-speed railway traction device are given to demonstrate the effectiveness of the proposed approach.