Establishment of human cerebral organoid systems to model early neural development and assess the central neurotoxicity of environmental toxins

Human brain development is a complex process,and animal models often have significant limitations.To address this,researchers have developed pluripotent stem cell-derived three-dimensional structures,known as brain-like organoids,to more accurately model early human brain development and disease.To enable more consistent and intuitive reproduction of early brain development,in this study,we incorporated forebrain organoid culture technology into the traditional unguided method of brain organoid culture.This involved embedding organoids in matrigel for only 7 days during the rapid expansion phase of the neural epithelium and then removing them from the matrigel for further cultivation,resulting in a new type of human brain organoid system.This cerebral organoid system replicated the temporospatial characteristics of early human brain development,including neuroepithelium derivation,neural progenitor cell production and maintenance,neuron differentiation and migration,and cortical layer patterning and formation,providing more consistent and reproducible organoids for developmental modeling and toxicology testing.As a proof of concept,we applied the heavy metal cadmium to this newly improved organoid system to test whether it could be used to evaluate the neurotoxicity of environmental toxins.Brain organoids exposed to cadmium for 7 or 14 days manifested severe damage and abnormalities in their neurodevelopmental patterns,including bursts of cortical cell death and premature differentiation.Cadmium exposure caused progressive depletion of neural progenitor cells and loss of organoid integrity,accompanied by compensatory cell proliferation at ectopic locations.The convenience,flexibility,and controllability of this newly developed organoid platform make it a powerful and affordable alternative to animal models for use in neurodevelopmental,neurological,and neurotoxicological studies.

Ultra-thin circularly polarized lens antenna based on single-layered transparent metasurface

Circularly polarized （CP） lens antenna has been applied to numerous wireless communication systems based on its unique advantages such as high antenna gain, low manufacturing cost, especially stable data transmission between the transmitter and the receiver. Unfortunately, current available CP lens antennas mostly suffer from high profile, low aperture efficiency as well as complex design. In this paper, we propose an ultra-thin CP lens antenna based on the designed single- layered Pancharatnam-Berry （PB） transparent metasurface with focusing property. The PB metasurface exhibits a high transmissivity, which ensures a high efficiency of the focusing property. Launched the metasurface with a CP patch antenna at its focal point, a low-profile lens antenna is simulated and measured. The experimental results show that our lens antenna exhibits a series of advantages including high radiation gain of 20.7 dB, aperture efficiency better than 41.3%, and also narrow half power beam width （HPBW） of 13°at about 14GHz. Our finding opens a door to realize ultra-thin transparent metasurface with other functionalities or at other working frequencies.

Is clustered seismicity an indicator of regional stress?Insights from earthquake sequences in Yongning-Luguhu faulted basin,Southwest China

Using hypocenter relocation,moment tensor inversion,stress field inversion,and fault slip tendency analysis,this study systematically investigated three M5.5-5.8 earthquake sequences that occurred after 2000 in the Yongning-Luguhu faulted basin in the middle of the Lijiang-Xiaojinhe fault zone within the Sichuan-Yunnan block,Southwest China.Our results show that since the 2008 Wenchuan earthquake,the tectonic stress pattern in this area may have changed and that b-values estimated for the earthquake sequences show evidence of an increasing trend in stress in the study area.Seismicity in the small-scale faulted basin adjacent to the large-scale fault zone is a possible indicator of regional stress.We also note that the aftershocks of the M5.7 earthquake sequence in 2012 and the M5.5 earthquake sequence in 2022 show relatively clear fluid diffusion-triggering characteristics.Overpressure of deep fluids is still the main factor driving seismic activity in the region,and we propose that the background tectonic stresses have not yet reached critical levels.

A novel receiver-transmitter metasurface for a high-aperture-efficiency Fabry-Perot resonator antenna

This paper presents a novel coupled receiver-transmitter metasurface(MS)which is used to realize a high-aperture-efficiency Fabry-Perot resonator antenna.The unit cell of the MS adopts a slot-coupling procedure to realize energy transmission from the receiver patch to the radiator patch.This approach makes it easier to independently control the transmission magnitude and phase.Based on this characteristic,the transmission coefficients of different unit cells on the MS can be optimized by a genetic algorithm.Then,nearly uniform electric amplitude and phase distribution across the aperture field of the antenna are achieved.Therefore,the gain and aperture efficiency of the antenna are improved.A prototype of the optimized antenna is fabricated and measured to validate the design.The measured gain of the fabricated antenna reaches 17.3 dBi with an aperture efficiency of 94.5%.A higher aperture efficiency is obtained with the proposed antenna which has a low profile and simple structure.

Planar Dual-Band Electrically Small Antenna Based on Double-Negative Metamaterials

A coaxially fed dual-band electrically small antenna based on double-negative metamaterials is presented in this letter. The antenna consists of a microstrip patch antenna as driven element and a double-negative metamaterials shell as parasitic element. Nearly complete matching of the entire system to a 50 Ω source without any matching network is achieved at 299 MHz and 837 MHz, with ka = 0.444 and 1.242 respectively. Measured performance agrees with simulations, and the proposed antenna has considerable radiation efficiency and is suitably employed for VHF and UHF applications.

Twisted Phosphors that Violate Kasha's Exciton Model in Organic Systems

Kasha's exciton model proposes that T1 energy levels of organic compounds are insensitive to molecular aggregation and microenvironment change because of negligible small transition dipole moments of T1 states.This model holds true in most organic systems till now.Here we report the fabrication of twisted organic phosphors with intramolecular charge transfer characters and flexible molecular structures.When doped into different organic matrices,the twisted phosphor adopts different conformation,exhibits distinct phosphorescence colors and T1 energy levels,which violates Kasha's exciton model in organic system.Given that the change of phosphorescence colors and maxima can be readily distinguished by human eyes and conventional instrument,the twisted phosphors would be exploited as a new type of molecular probe,which would exhibit potential application in optical sensing and stimuli-responsive systems.

A Two-color Single-molecule Sequencing Platform and Its Clinical Applications

DNA sequencers have become increasingly important research and diagnostic tools over the past 20 years.In this study,we developed a single-molecule desktop sequencer,GenoCare 1600(GenoCare),which utilizes amplification-free library preparation and two-color sequencing-by-synthesis chemistry,making it more user-friendly compared with previous single-molecule sequencing platforms for clinical use.Using the GenoCare platform,we sequenced an Escherichia coli standard sample and achieved a consensus accuracy exceeding 99.99%.We also evaluated the sequencing performance of this platform in microbial mixtures and coronavirus disease 2019(COVID-19)samples from throat swabs.Our findings indicate that the GenoCare platform allows for microbial quantitation,sensitive identification of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)virus,and accurate detection of virus mutations,as confirmed by Sanger sequencing,demonstrating its remarkable potential in clinical application.

Bio-inspired Flow Sensing and Prediction for Fish-like Undulating Locomotion： A CFD-aided Approach

Feedback flow information is of significance to enable underwater locomotion controllers with higher adaptability and efficiency within varying environments. Inspired from fish sensing their external flow via near-body pressure, a computational scheme is proposed and developed in this paper. In conjunction with the scheme, Computational Fluid Dynamics （CFD） is employed to study the bio-inspired fish swimming hydrodynamics. The spatial distribution and temporal variation of the near-body pressure of fish are studied over the whole computational domain. Furthermore, a filtering algorithm is designed and implemented to fuse near-body pressure of one or multiple points for the estimation on the external flow. The simulation results demonstrate that the proposed computational scheme and its corresponding algorithm are both effective to predict the inlet flow velocity by using near-body pressure at distributed spatial points.

Time-frequency analysis of wheel-rail shock in the presence of wheel flat

Against the deficiencies of traditional time domain and frequency domain analysis in detecting wheel-rail （W-R） system hidden risks which wheel flats generate, the time-frequency characteristics of W-R shock caused by wheel flat are analyzed and the vehicle-rail dynamic model with wheel flat is investigated. The 10 degrees of freedom （DOF） vehicle model is built up. 90-DOF rail model is constructed. The wheel flat excitation model is built up. The vehicle-track coupling dynamic model including wheel flat excitation is set up through nonlinear Hertzian contact theory. The vertical accelerations of axle box are calculated at different speeds and flat sizes based on the vehicle-track coupling dynamic model with wheel flat. Frequency slice wavelet transform （FSWT） is employed to analyze time- frequency characteristics of axle box accelerations to detect the W-R noncontact risks, which the traditional time domain or frequency domain method does not analyze. The results show that the small flat size and high running speed lead to high frequency W-R impact. Large flat size and high running speed result in momentary loss of W-R contact, and there exist security risks between wheel and rail. The conclusion that the phase of axle box accelerations is same to W-R forces lays a theoretical foundation of monitoring W-R contact safety from axle box acceleration instead of traditional W-R force detection.

Ultrawideband chromatic aberration-free meta-mirrors

Chromatic aberration-free meta-devices(e.g.,achromatic meta-devices and abnormal chromatic meta-devices)play an essential role in modern science and technology.However,current efforts suffer the issues of low efficiency,narrow operating band,and limited wavefront manipulation capability.We propose a general strategy to design chromatic aberration-free meta-devices with high-efficiency and ultrabroadband properties,which is realized by satisfying the key criteria of desirable phase dispersion and high reflection amplitudes at the target frequency interval.The phase dispersion is tuned successfully based on a multiresonant Lorentz model,and high reflection is guaranteed by the presence of the metallic ground.As proof of the concept,two microwave meta-devices are designed,fabricated,and experimentally characterized.An achromatic meta-mirror is proposed within 8 to 12 GHz,and another abnormal chromatic meta-mirror can tune the reflection angle as a linear function.Both meta-mirrors exhibit very high efficiencies(85%to 94%in the frequency band).Our findings open a door to realize chromatic aberration-free meta-devices with high efficiency and wideband properties and stimulate the realizations of chromatic aberration-free metadevices with other functionalities or working at higher frequency.

Advanced charge transfer technology for highly efficient and long-lived TADF-type organic afterglow with near-infrared light-excitable property

Heavy atom effects and n-π*transitions have been frequently reported to enhance room-temperature organic phosphorescence efficiency but lead to shortage of phosphorescence lifetimes.Unlike these reported studies,we conceive the incorporation of advanced charge transfer(CT)technology to boost room-temperature organic afterglow efficiency and simultaneously maintain afterglow lifetimes.Here we design difluoroboronβ-diketonate(BF2bdk)CT compounds with moderate singlet-triplet splitting energy(ΔEST)of around 0.4 e V,and relatively large spin-orbit coupling matrix elements(SOCME(S_(1)-T_(1)),1–10 cm^(-1))to achieve efficient intersystem crossing(ISC)and moderate rates of reverse intersystem crossing(kRISC,1–10 s^(-1)).The advanced CT technology,which includes multiple electron-donating groups and orthogonal donor-acceptor arrangement,have been found to narrowΔESTand enhance both ISC and RISC.Meanwhile,the organic matrices suppress nonradiative decay of BF2bdk’s T1states by their rigid microenvironment.Consequently,thermally activated delayed fluorescence(TADF)-type organic afterglow materials can be achieved with afterglow efficiency up to 83.0%,long lifetimes of 433 ms,excellent processablility,as well as advanced anti-counterfeiting and information encryption.Furthermore,with the aid of up-conversion materials and through radiative energy transfer,TADF-type afterglow materials with aqueous dispersity and near-infrared light-excitable property have been achieved,which paves the way for biomedical applications.