Unsupervised Color Segmentation with Reconstructed Spatial Weighted Gaussian Mixture Model and Random Color Histogram

Image classification and unsupervised image segmentation can be achieved using the Gaussian mixture model.Although the Gaussian mixture model enhances the flexibility of image segmentation,it does not reflect spatial information and is sensitive to the segmentation parameter.In this study,we first present an efficient algorithm that incorporates spatial information into the Gaussian mixture model(GMM)without parameter estimation.The proposed model highlights the residual region with considerable information and constructs color saliency.Second,we incorporate the content-based color saliency as spatial information in the Gaussian mixture model.The segmentation is performed by clustering each pixel into an appropriate component according to the expectation maximization and maximum criteria.Finally,the random color histogram assigns a unique color to each cluster and creates an attractive color by default for segmentation.A random color histogram serves as an effective tool for data visualization and is instrumental in the creation of generative art,facilitating both analytical and aesthetic objectives.For experiments,we have used the Berkeley segmentation dataset BSDS-500 and Microsoft Research in Cambridge dataset.In the study,the proposed model showcases notable advancements in unsupervised image segmentation,with probabilistic rand index(PRI)values reaching 0.80,BDE scores as low as 12.25 and 12.02,compactness variations at 0.59 and 0.7,and variation of information(VI)reduced to 2.0 and 1.49 for the BSDS-500 and MSRC datasets,respectively,outperforming current leading-edge methods and yielding more precise segmentations.

Research progress of femtosecond surface plasmon polariton

As the combination of surface plasmon polariton and femtosecond laser pulse,femtosecond surface plasmon polariton has both nanoscale spatial resolution and femtosecond temporal resolution,and thus provides promising methods for light field manipulation and light-matter interaction in extreme small spatiotemporal scales.Nowadays,the research on femtosecond surface plasmon polariton is mainly concentrated on two aspects:one is investigation and characterization of excitation,propagation,and dispersion properties of femtosecond surface plasmon polariton in different structures or materials;the other one is developing new applications based on its unique properties in the fields of nonlinear enhancement,pulse shaping,spatiotemporal super-resolved imaging,and others.Here,we introduce the research progress of properties and applications of femtosecond surface plasmon polariton,and prospect its future research trends.With the further development of femtosecond surface plasmon polariton research,it will have a profound impact on nano-optoelectronics,molecular dynamics,biomedicine and other fields.

振荡浮子式双浮体波浪能装置的阵列特性（英文）

As the energy supply problem worsens, the development and utilization of marine renewable energy have become a research hotspot. The development of wave energy is moving from the near shore to the distant sea. The power-generation efficiency of a single two-floating-body wave-energy converter is relatively low. To fully utilize wave energy and improve the wave-energy capture rate of a fixed sea area, arranging a two-floating-body wave-energy converter array is necessary. This paper first introduces the basic theory of multi-floating flow field, time-domain calculation method, and influence factor of the waveenergy converter array. Then, the development of AQWA software in Fortran language considers the effect of power takeoff. A calculation method based on ANSYS–AQWA is proposed to simulate the motion of the oscillating-buoy two-floating-body wave-energy converter. The results are compared with the experimental results from the National Renewable Energy Laboratory. Finally, the ANSYS–AQWA method is used to study the power characteristics of simple and complex arrays of wave-energy converters. The average power generation of simple arrays is largest at 0°, and the average power generation of complex arrays does not change with the wave direction. Optimal layout spacing exists for the simple and complex arrays. These findings can serve as a valuable reference for the large-scale array layout of wave-energy converters in the future.

聚集诱导发光荧光探针在生物成像中的研究进展

有机荧光生物探针在监测生命体物质活动中具有重要的意义。与量子点(quantum dots,QDs)、绿色荧光蛋白(green fluorescent protein,GFP)和传统的具有聚集诱导淬灭效应的荧光团相比,聚集诱导发光(aggregation-induced emission,AIE)探针具有聚集态荧光强、斯托克斯位移大、光稳定性好、细胞毒性小、操作简便等显著优点。因此,AIE探针已经被广泛应用于生物医学等领域。本文简要综述了近年来AIE探针在细胞器成像、细胞追踪、活体成像方面的研究进展。

Spatiotemporal Fourier transform with femtosecond pulses for on-chip devices

On-chip manipulation of the spatiotemporal characteristics of optical signals is important in the transmission and processing of information.However,the simultaneous modulation of on-chip optical pulses,both spatially at the nano-scale and temporally over ultra-fast intervals,is challenging.Here,we propose a spatiotemporal Fourier transform method for on-chip control of the propagation of femtosecond optical pulses and verify this method employing surface plasmon polariton(SPP)pulses on metal surface.An analytical model is built for the method and proved by numerical simulations.By varying space-and frequency-dependent parameters,we demonstrate that the traditional SPP focal spot may be bent into a ring shape,and that the direction of propagation of a curved SPP-Airy beam may be reversed at certain moments to create an S-shaped path.Compared with conventional spatial modulation of SPPs,this method offers potentially a variety of extraordinary effects in SPP modulation especially associated with the temporal domain,thereby providing a new platform for on-chip spatiotemporal manipulation of optical pulses with applications including ultrafast on-chip photonic information processing,ultrafast pulse/beam shaping,and optical computing.

A vectorial model for the nonlinear gradient force exerted on metallic Rayleigh nanoparticles

Optical tweezers have proved to be a powerful tool with a wide range of applications.The gradient force plays a vital role in the stable optical trapping of nano-objects.The scalar method is convenient and effective for analyzing the gradient force in traditional optical trapping.However,when the third-order nonlinear effect of the nano-object is stimulated,the scalar method cannot adequately present the optical response of the metal nanoparticle to the external optical field.Here,we propose a theoretical model to interpret the nonlinear gradient force using the vector method.By combining the optical Kerr effect,the polarizability vector of the metallic nanoparticle is derived.A quantitative analysis is obtained for the gradient force as well as for the optical potential well.The vector method yields better agreement with reported experimental observations.We suggest that this method could lead to a deeper understanding of the physics relevant to nonlinear optical trapping and binding phenomena.

AI-assisted cell identification and optical sorting[Invited]

Cell identification and sorting have been hot topics recently.However,most conventional approaches can only predict the category of a single target,and lack the ability to perform multitarget tasks to provide coordinate information of the targets.This limits the development of high-throughput cell screening technologies.Fortunately,artificial intelligence(AI)systems based on deep-learning algorithms provide the possibility to extract hidden features of cells from original image information.Here,we demonstrate an AI-assisted multitarget processing system for cell identification and sorting.With this system,each target cell can be swiftly and accurately identified in a mixture by extracting cell morphological features,whereafter accurate cell sorting is achieved through noninvasive manipulation by optical tweezers.The AI-assisted model shows promise in guiding the precise manipulation and intelligent detection of high-flux cells,thereby realizing semiautomatic cell research.

Recommendations for the Diagnosis and Treatment of Maternal SARS-CoV-2 Infection

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has spread worldwide and threatened human’s health.With the passing of time,the epidemiology of coronavirus disease 2019 evolves and the knowledge of SARS-CoV-2 infection accumulates.To further improve the scientific and standardized diagnosis and treatment of maternal SARS-CoV-2 infection in China,the Chinese Society of Perinatal Medicine of Chinese Medical Association commissioned leading experts to develop the Recommendations for the Diagnosis and Treatment of Maternal SARS-CoV-2 Infection under the guidance of the Maternal and Child Health Department of the National Health Commission.This recommendations includes the epidemiology,diagnosis,management,maternal care,medication treatment,care of birth and newborns,and psychological support associated with maternal SARS-CoV-2 infection.It is hoped that the recommendations will effectively help the clinical management of maternal SARS-CoV-2 infection.

Nonlinear optical trapping effect with reverse saturable absorption

Nonlinear responses of nanoparticles induce enlightening phenomena in optical tweezers. With thegradual increase in optical intensity, effects from saturable absorption (SA) and reverse SA (RSA) arise insequence and thereby modulate the nonlinear properties of materials. In current nonlinear optical traps,however, the underlying physical mechanism is mainly confined within the SA regime because thresholdvalues required to excite the RSA regime are extremely high. Herein, we demonstrate, both in theory andexperiment, nonlinear optical tweezing within the RSA regime, proving that a fascinating composite trappingstate is achievable at ultrahigh intensities through an optical force reversal induced through nonlinearabsorption. Integrated results help in perfecting the nonlinear optical trapping system, thereby providingbeneficial guidance for wider applications of nonlinear optics.

Optimization model research on efficacy in treatment of chronic urticaria by Chinese and Western Medicine based on a genetic algorithm

OBJECTIVE: To investigate the potential rules and knowledge of Traditional Chinese Medicine (TCM) and Western Medicine (WM) treatment on chronic urticaria (CU) based on data-mining methods. METHODS: Sixty patients with chronic urticaria, treated with TCM and WM, were selected. Gray correlation analyses were adopted to determine therapeutic efficacy. Association algorithms were utilized to ascertain the correlation between the disease course and treatment results. A genetic algorithm was applied to discover the optimization model in theTCM andWM treatment on CU. RESULTS: The total symptom scores after 4 weeks and 8 weeks of treatment in the TCM spleen-strengthening group correlated highly with the pretreatment total symptom score. The duration of treatment showed the greatest impact on the total symptom score. A quartic equation was established (y=-1.6403×10-6x4+0.00025576x3+0.0012819 x2-1.024x+79.5879, and x=106.9518, y=83.0036) using the genetic algorithm. CONCLUSION: TCM treatment had a better effect in the later stage, whereas WM was better in the early stage. The duration of disease course had an impact on the effects of treatment. If the average total symptom score before treatment was ≤ 83.0036, TCM or WM treatment could achieve better efficacy.

All-optical manipulation of micrometer-sized metallic particles

Optical traps use focused laser beams to generate forces on targeted objects ranging in size from nanometers to micrometers. However, for their high coefficients of scattering and absorption, micrometer-sized metallic particles were deemed non-trappable in three dimensions using a single beam. This barrier is now removed. We demonstrate, both in theory and experiment, three-dimensional(3D) dynamic all-optical manipulations of micrometersized gold particles under high focusing conditions. The force of gravity is found to balance the positive axial optical force exerted on particles in an inverted optical tweezers system to form two trapping positions along the vertical direction. Both theoretical and experimental results confirm that stable 3D manipulations are achievable for these particles regardless of beam polarization and wavelength. The present work opens up new opportunities for a variety of in-depth research requiring metallic particles.

Multifunctional geometric phase optical element for high-efficiency full Stokes imaging polarimetry

Polarization imaging finds applications in many areas, such as photoelasticity, ellipsometry, and biomedical imaging. A compact, snapshot, and high-efficiency imaging polarimeter is highly desirable for many applications.Here, based on a single multifunctional geometric phase optical element(GPOE), a new method is proposed for high-efficiency snapshot imaging polarimetry. With tailored spatially varying orientation of each anisotropic unit cell, the GPOE works highly efficiently as both a spin sorter and a half-wave plate, enabling snapshot retrieving of a full Stokes vector of incident light. The designed GPOE is implemented in the form of liquid crystal fabricated with a photo-alignment technology, and its application in imaging polarimetry is experimentally demonstrated by retrieving full Stokes parameters of a cylinder vector beam. This method can also work in the form of plasmonic or dielectric metasurfaces, enabling ultra-compact polarization detection systems by monolithic integration with other devices such as metalenses.

Enhancing plasmonic trapping with a perfect radially polarized beam

Strong plasmonic focal spots, excited by radially polarized light on a smooth thin metallic film, have been widely applied to trap various micro-and nano-sized objects. However, the direct transmission part of the incident light leads to the scattering force exerted on trapped particles, which seriously affects the stability of the plasmonic trap.Here we employ a novel perfect radially polarized beam to solve this problem. Both theoretical and experimental results verify that such a beam could strongly suppress the directly transmitted light to reduce the piconewton scattering force, and an enhanced plasmonic trapping stiffness that is 2.6 times higher is achieved in experiments.The present work opens up new opportunities for a variety of research requiring the stable manipulations of particles.

Wide-field in situ multiplexed Raman imaging with superresolution

Because of the fingerprint-like specificity of its characteristic spectrogram, Raman spectral imaging has been applied widely in various research areas. Using a combination of structured illumination with the surface-enhanced Raman scattering(SERS) technique, wide-field Raman imaging is developed with a significant improvement in spatial resolution. As a result of the relatively narrow Raman characteristic peaks, optically encoded SERS nanoparticles can be used to perform multiplexed imaging. The results show excellent superresolution wide-field multiplexed imaging performance. The developed technique has extraordinary potential for applications in biological imaging and other related fields.

Single-particle trapping and dynamic manipulation with holographic optical surface-wave tweezers

Optical surface waves have widely been used in optical tweezers systems for trapping particles sized from the nanoto microscale,with specific importance and needs in applications of super-resolved detection and imaging if a single particle can be trapped and manipulated accurately.However,it is difficult to achieve such trapping with high precision in conventional optical surface-wave tweezers.Here,we propose and experimentally demonstrate a new method to accurately trap and dynamically manipulate a single particle or a desired number of particles in holographic optical surface-wave tweezers.By tailoring the optical potential wells formed by surface waves,we achieved trapping of the targeted single particle while pushing away all surrounding particles and further dynamically controlling the particle by a holographic tweezers beam.We also prove that different particle samples,including gold particles and biological cells,can be applied in our system.This method can be used for different-type optical surface-wave tweezers,with significant potential applications in single-particle spectroscopy,particle sorting,nano-assembly,and others.

Plasmonic tweezers: for nanoscale optical trapping and beyond

Optical tweezers and associated manipulation tools in the far field have had a major impact on scientific and engineering research by offering precise manipulation of small objects.More recently,the possibility of performing manipulation with surface plasmons has opened opportunities not feasible with conventional far-field optical methods.The use of surface plasmon techniques enables excitation of hotspots much smaller than the free-space wavelength;with this confinement,the plasmonic field facilitates trapping of various nanostructures and materials with higher precision.The successful manipulation of small particles has fostered numerous and expanding applications.In this paper,we review the principles of and developments in plasmonic tweezers techniques,including both nanostructure-assisted platforms and structureless systems.Construction methods and evaluation criteria of the techniques are presented,aiming to provide a guide for the design and optimization of the systems.The most common novel applications of plasmonic tweezers,namely,sorting and transport,sensing and imaging,and especially those in a biological context,are critically discussed.Finally,we consider the future of the development and new potential applications of this technique and discuss prospects for its impact on science.

siRNA-functionalized lanthanide nanoparticle enables efficient endosomal escape and cancer treatment

Attaching DNA/RNA to nanomaterials is the basis for nucleic acid-based assembly and drug delivery.Herein,we report that small interfering RNA(siRNA)effectively coordinates with ligand-free lanthanide nanoparticles(NaGdF4 NPs),and forms siRNA/NaGdF4 spherical nucleic acids(SNA).The coordination is primarily attributed to the interaction between Gd and phosphate backbone of the siRNA.Surprisingly,an efficient encapsulation and rapid endosomal escape of siRNA from the endosome/lysosome were achieved,due to its flexible ability to bound to phospholipid head of endosomal membrane,thereby disrupting the membrane structure.Resorting to the dual properties of NaGdF4 NPs,siRNA loading,and endosomal escape,siRNA targeting programmed cell death-ligand 1(siPD-L1)/NaGdF4 SNA triggers significant gene silencing in vitro and in vivo,and effectively represses the tumor growth in both CT26 tumor model and 4T1 orthotopic murine model.

Biosafety materials:Ushering in a new era of infectious disease diagnosis and treatment with the CRISPR/Cas system

Despite multiple virus outbreaks over the past decade,including the devastating coronavirus disease 2019(COVID-19)pandemic,the lack of accurate and timely diagnosis and treatment technologies has wreaked havoc on global biosecurity.The clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated proteins(Cas)system has the potential to address these critical needs for tackling infectious diseases to detect viral nucleic acids and inhibit viral replication.This review summarizes how the CRISPR/Cas system is being utilized for the treatment and diagnosis of infectious diseases with the help of biosafety materials and highlights the design principle and in vivo and in vitro efficacy of advanced biosafety materials used to deal with virus attacks.

Imaging ultrafast evolution of subwavelengthsized topography using single-probe structured light microscopy

Imaging ultrafast processes in femtosecond(fs) laser–material interactions such as fs laser ablation is very important to understand the physical mechanisms involved. To achieve this goal with high resolutions in both spatial and temporal domains, a combination of optical pump–probe microscopy and structured illumination microscopy can be a promising approach, but suffers from the multiple-frame method with a phase shift that is inapplicable to irreversible ultrafast processes such as ablation. Here, we propose and build a wide-field singleprobe structured light microscopy(SPSLM) to image the ultrafast three-dimensional topography evolution induced by fs lasers, where only a single imaging frame with a single structured probe pulse is required for topography reconstruction, benefiting from Fourier transform profilometry. The second harmonic of the fs laser is used as the structured probe light to improve spatial lateral resolution into the subwavelength region of ~478 nm, and the spatial axial and temporal resolutions are estimated to be ~22 nm and ~256 fs, respectively. With SPSLM, we successfully image the ultrafast topography evolution of a silicon wafer surface impacted by single and multiple fs pulses. The variable formation and evolution of the laser induced periodic surface structures during an ultrashort time are visualized and analyzed. We believe that SPSLM will be a significant approach for revealing and understanding various ultrafast dynamics, especially in fs laser ablation and material science.

Facilitated tip-enhanced Raman scattering by focused gap-plasmon hybridization

Tip-enhanced Raman scattering(TERS)spectroscopy is a nondestructive and label-free molecular detection approach that provides high sensitivity and nanoscale spatial resolution.Therefore,it has been used in a wide array of applications.We demonstrate a gap-plasmon hybridization facilitated by a bottom-illuminated TERS configuration.The gap-plasmon hybridization effect is first performed with the finite-difference time-domain method to optimize the parameters,and experiments are then conducted to calibrate the performance.The results demonstrate an enhancement factor of 1157 and a spatial resolution of 13.5 nm.The proposed configuration shows great potential in related surface imaging applications in various fields of research.