Polar-coordinate line-projection light-curing continuous 3D printing for tubular structures

3D printing techniques offer an effective method in fabricating complex radially multi-material structures.However,it is challenging for complex and delicate radially multi-material model geometries without supporting structures,such as tissue vessels and tubular graft,among others.In this work,we tackle these challenges by developing a polar digital light processing technique which uses a rod as the printing platform.The 3D model fabrication is accomplished through line projection.The rotation and translation of the rod are synchronized to project and illuminate the photosensitive material volume.By controlling the distance between the rod and the printing window,we achieved the printing of tubular structures with a minimum wall thickness as thin as 50 micrometers.By controlling the width of fine slits at the printing window,we achieved the printing of structures with a minimum feature size of 10 micrometers.Our process accomplished the fabrication of thin-walled tubular graft structure with a thickness of only 100 micrometers and lengths of several centimeters within a timeframe of just 100 s.Additionally,it enables the printing of axial multi-material structures,thereby achieving adjustable mechanical strength.This method is conducive to rapid customization of tubular grafts and the manufacturing of tubular components in fields such as dentistry,aerospace,and more.

环状RNA的产生、研究方法及功能

随着高通量测序技术的发展,环状RNA(circular RNAs,circRNAs)逐渐成为非编码RNA研究领域的热点。本文系统综述了环状RNA侧翼内含子自身互补配对驱动、RNA结合蛋白驱动以及套索驱动这3种环状RNA形成模型,并从高通量文库构建、生物信息学鉴别和常用的实验验证等3个方面对环状RNA的研究方法进行了介绍。同时,本文详细归纳了环状RNA作为microRNA(miRNA)或蛋白的海绵体、调控宿主基因的选择性剪接和表达、翻译成多肽等多种功能。最后通过系统综述植物环状RNA的特征及最新研究进展,为环状RNA在植物学中的进一步研究提供了新的视野。

A rolled Mg-8Al-0.5Zn-0.8Ce alloy with high strength-ductility synergy via engineering high-density low angle boundaries

Developing low-cost rolled Mg alloys with both high strength and ductility is desirable,while the improved strength is generally accompanied with decreased ductility.Here,by using rotated hard-plate rolling(RHPR)with a total thickness reduction of~85%,we obtained a Mg-8Al-0.5Zn-0.8Ce(wt.%,AZ80-0.8Ce)alloy with a high strength-ductility synergy,i.e.,the yield strength(YS),ultimate tensile strength(UTS)and elongation-to-failure(EF)are~308 MPa,~360 MPa and~13.8%,respectively.It reveals that the high YS is mainly originated from grain boundary strengthening(~212 MPa),followed by dislocation strengthening(~43 MPa)and precipitation hardening(~25 MPa).It is found that a relatively homogeneous fine grain structure containing a large fraction(~62%)of low angle boundaries(LABs)is achieved in the RHPRed alloy,which is benefit for the high tensile EF value.It demonstrates that LABs have important contributions to strengthening and homogenizing tensile deformation process,leading to the simultaneous high strength and high EF.Our work provides a new insight for fabrication of low-cost high performance Mg alloys with an excellent strength-ductility synergy.

Hardening effect and precipitation evolution of an isothermal aged Mg-Sm based alloy

The age-hardening behavior and precipitation evolution of an isothermal aged Mg-5Sm-0.6Zn-0.5Zr(wt.%) alloy have been systematically investigated by means of transmission electron microscopy(TEM) and atomic-resolution high-angle annular dark field scanning transmission electron microscopy(HAADF-STEM). The Vickers hardness of the present alloy increases first and then decreases with ageing time. The sample aged at 200 ℃ for 10 h exhibits a peak-hardness of 90.5 HV. In addition to the dominant β_(0)’ precipitate(orthorhombic,a = 0.642 nm, b = 3.336 nm and c = 0.521 nm) formed on {11-20}α planes, a certain number of γ’’ precipitate(hexagonal, a = 0.556 nm and c = 0.431 nm) formed on basal planes are also observed in the peak-aged alloy. Significantly, the basal γ’’ precipitate is more thermostable than prismatic β_(0)’ precipitate in the present alloy. β_(0)’ precipitates gradually coarsened and were even likely to transform into β_(1) phase(face centered cubic, a = 0.73 nm) with the increase of ageing time, which accordingly led to a gradual decrease in number density of precipitates and finally resulted in the decreased hardness and mechanical property in the over-aged alloys.

Dynamic Pricing of Tropical Fruits in Hainan Based on Internet of Things Technology

In recent years,the Internet of Things(IoT)technology has been widely used in the production and sales of tropical fruits,with strong practicability and wide application prospects.The tropical fruit dynamic pricing model based on the IoT technology can promote the healthy development of the tropical fruit industry in Hainan and ensure the income of fruit farmers.Based on IoT technology,the quality grade of tropical fruits in Hainan is obtained.According to the dynamic pricing strategy of revenue management,a dynamic pricing model based on the quality of tropical fruits and a dynamic pricing model based on consumer segmentation are established to study the dynamic pricing problem under the condition of maximum profit for tropical fruit sellers.The research results show that for different fruit quality and consumer groups,different pricing models are required for pricing,in order to get the maximum profit from tropical fruit sales.Sellers must flexibly adopt different dynamic pricing models to price tropical fruits to enhance the competitiveness of the tropical fruit industry.

有机荧光分子检测环境中金属离子的研究进展

随着污染物的排放日益增多,环境问题备受关注.金属离子作为重要的污染来源之一,对人们生活造成了极大的影响,并可能引发各种疾病.因此,快速灵敏地检测环境中的金属离子尤为重要.含有各种检测基团的有机染料通过表观颜色和荧光的变化,实现了对金属离子特异、灵敏的检测,表现出巨大的潜力.本文基于有机荧光分子的特殊光物理性质与共轭结构,综述了近年来有机金属离子探针常用的检测机理.所涉及的检测机理主要有光诱导电子转移(photoinduced electron transfer,PET)机理、分子内电荷转移(intramolecular charge transfer,ICT)机理、荧光共振能量转移(fluorescence resonance energy transfer,FRET)机理、跨键能量转移(through-bond energy transfer,TBET)机理、分子的聚集-解聚以及π共轭结构重排.此外,还对金属离子与探针之间的相互作用,以及探针的基本设计思路进行详细的讨论,并在目前研究的基础上对其发展前景进行展望.

Science with the 2.5-meter Wide Field Survey Telescope(WFST)

The Wide Field Survey Telescope(WFST) is a dedicated photometric surveying facility being built jointly by University of Science and Technology of China(USTC) and the Purple Mountain Observatory(PMO). It is equipped with a 2.5-meter diameter primary mirror, an active optics system, and a mosaic CCD camera with 0.73 gigapixels on the primary focal plane for highquality image capture over a 6.5-square-degree field of view. The installation of WFST near the summit of Saishiteng mountain in the Lenghu region is scheduled in summer of 2023, and the operation is planned to start three months later. WFST will scan the northern sky in four optical bands(u, g, r and i) at cadences from hourly/daily in the deep high-cadence survey(DHS) program, to semi-weekly in the wide field survey(WFS) program. During a photometric night, a nominal 30 s exposure in the WFS program will reach a depth of 22.27, 23.32, 22.84, and 22.31(AB magnitudes) in these four bands, respectively, allowing for the detection of a tremendous amount of transients in the low-z universe and a systematic investigation of the variability of Galactic and extragalactic objects. In the DHS program, intranight 90 s exposures as deep as 23(u) and 24 mag(g), in combination with target of opportunity follow-ups, will provide a unique opportunity to explore energetic transients in demand for high sensitivities, including the electromagnetic counterparts of gravitational wave events, supernovae within a few hours of their explosions,tidal disruption events and fast, luminous optical transients even beyond redshift of unity. In addition, the final 6-year co-added images, anticipated to reach g■25.8 mag in WFS or 1.5 mags deeper in DHS, will be of fundamental importance to general Galactic and extragalactic science. The highly uniform legacy surveys of WFST will serve as an indispensable complement to those of the Vera C. Rubin Observatory's Legacy Survey of Space and Time(LSST) that monitors the southern sky.

Numerical Experiment of the Solid Particle Erosion of Bionic Configuration Blade of Centrifugal Fan

In this paper, a bionic method was presented to improve the erosion resistance of blade of the centrifugal fan. A numerical investigation of the solid particle erosion on the standard and bionic configuration blade of 4-72N_o10C centrifugal fan was presented. The numerical study employs computational fluid dynamics （CFD） software, based on a finite volume method, in which the discrete phase model was used to modele the solid particles flow, and the Eulerian conservation equation was adopt to simulate the continuous phase. Moreover, user-defined function was used to define wear equation. The various diameters of the particles were taken into account. The positions of collision of standard and bionic fan blades were discussed, and two kinds of centrifugal fan blade wear were compared. The results show that the particles from the incident source with different positions have different processes of turning and movement when enter into the impeller. The trajectories of flow in the fan channel are significantly different for the particles with different diameters. Bionic fan blade have lower erosion rate than the standard fan blade when the particle size is 20 μm. The anti-erosion mechanism of the bionic fan blade was discussed.

Short-Term Dynamic Radar Quantitative Precipitation Estimation Based on Wavelet Transform and Support Vector Machine

Currently,Doppler weather radar in China is generally used for quantitative precipitation estimation(QPE)based on the Z–R relationship.However,the estimation error for mixed precipitation is very large.In order to improve the accuracy of radar QPE,we propose a dynamic radar QPE algorithm with a 6-min interval that uses the reflectivity data of Doppler radar Z9002 in the Shanghai Qingpu District and the precipitation data at automatic weather stations(AWSs)in East China.Considering the time dependence and abrupt changes of precipitation,the data during the previous 30-min period were selected as the training data.To reduce the complexity of radar QPE,we transformed the weather data into the wavelet domain by means of the stationary wavelet transform(SWT)in order to extract high and low-frequency reflectivity and precipitation information.Using the wavelet coefficients,we constructed a support vector machine(SVM)at all scales to estimate the wavelet coefficient of precipitation.Ultimately,via inverse wavelet transformation,we obtained the estimated rainfall.By comparing the results of the proposed method(SWTSVM)with those of Z=300×R1.4,linear regression(LR),and SVM,we determined that the root mean square error(RMSE)of the SWT-SVM method was 0.54 mm per 6 min and the average Threat Score(TS)could exceed 40%with the exception of the downpour category,thus remaining at a high level.Generally speaking,the SWT-SVM method can effectively improve the accuracy of radar QPE and provide an auxiliary reference for actual meteorological operational forecasting.

Manufacture of Nano-Sized Particle-Reinforced Metal Matrix Composites:A Review

Compared to the micro-sized particle-reinforced metal matrix composites, the nano-sized particle-reinforced metal matrix composites possess superior strength, ductility, and wear resistance, and they also exhibit good elevated temperature properties. Therefore, the nano-sized particle-reinforced metal matrix composites are the new potential material which could be applied in many industry fields. At present, the nano-sized particle-reinforced metal matrix composites could be manufactured by many methods. Different kinds of metals, predominantly A1, Mg, and Cu, have been employed for the production of composites reinforced by nano-sized ceramic particles such as carbides, nitrides, and oxides. The main drawbacks of these synthesis methods are the agglomeration of the nano-sized particles and the poor interface between the particles and the metal matrix. This work is aimed at reviewing the ex situ and in situ manufacturing techniques. Moreover, the distinction between the two methods is discussed in some detail. It was agreed that the in situ manufacturing technique is a promising method to fabricate the nano-sized particle-reinforced metal matrix composites.

Profiling of circular RNA N^(6)-methyladenosine in moso bamboo(Phyllostachys edulis)using nanopore-based direct RNA sequencing

N6-methyladenosine(m^(6)A)is a prevalent modification in messenger RNAs and circular RNAs that play important roles in regulating various aspects of RNA metabolism.However,the occurrence of the m^(6)A modification in plant circular RNAs has not been reported.A widely used method to identify m^(6)A modifications relies on m^(6)A-specific antibodies followed by next-generation sequencing of precipitated RNAs(MeRIP-Seq).However,one limitation of MeRIP-Seq is that it does not provide the precise location of m^(6)A at single-nucleotide resolution.Although more recent sequencing techniques such as Nanopore-based direct RNA sequencing(DRS)can overcome such limitations,the technology does not allow sequencing of circular RNAs,as these molecules lack a poly(A)tail.Here,we developed a novel method to detect the precise location of m^(6)A modifications in circular RNAs using Nanopore DRS.We first enriched our samples for circular RNAs,which we then fragmented and sequenced on the Nanopore platform with a customized protocol.Using this method,we identified 470 unique circular RNAs from DRS reads based on the back-spliced junction region.Among exonic circular RNAs,about 10%contained m^(6)A sites,which mainly occurred around acceptor and donor splice sites.This study demonstrates the utility of our antibody-independent method in identifying total and methylated circular RNAs using Nanopore DRS.This method has the additional advantage of providing the exact location of m^(6)A sites at single-base resolution in circular RNAs or linear transcripts from non-coding RNA without poly(A)tails.

Application of non-equilibrium dendrite growth model considering thermo-kinetic correlation in twin-roll casting

Upon non-equilibrium solidifications, dendrite growth, generally as precursor of as-solidified structures,has severe effects on subsequent phase transformations. Considering synergy of thermodynamics and kinetics controlling interface migration and following conservation of heat flux in solid temperature field, a more flexible modeling for the dendrite growth is herein developed for multi-component alloys,where, two inherent problems, i.e. correlation between thermodynamics and kinetics(i.e. the thermokinetic correlation), and theoretical connection between dendrite growth model and practical processing,have been successfully solved. Accordingly, both the thermodynamic driving force G and the effective kinetic energy barrier Qeffhave been found to control quantitatively the dendrite growth(i.e. especially the growth velocity, V), as reflected by the thermo-kinetic trade-off. Compared with previous models, it is the thermo-kinetic correlation that guarantees quantitative connection between the practical processing parameters and the current theoretical framework, as well as more reasonable description for kinetic behaviors involved. Applied to the vertical twin-roll casting(VTC), the present model, realizes a good prediction for kissing points, which influences significantly alloy design and processing optimization.This work deduces quantitatively the thermo-kinetic correlation controlling the dendrite growth, and by proposing the parameter-triplets(i.e. G-Qeff-V), further opens a new beginning for connecting solidification theories with industrial applications, such as the VTC.

Ultrahigh-performance mesoporous ZnMn2O4 microspheres as anode materials for lithium-ion batteries and their in situ Raman investigation

Currently, lithium-ion batteries play a key role in energy storage; however, their applications are limited by their low energy density. Here, we design a facile method to prepare mesoporous ZnMn2O4 microspheres with ultrahigh rate performance and ultralong cycling properties by finely tuning the solution viscosity during synthesis. When the current density is raised to 2 A·g^-1, the discharge capacity is maintained at 879 mA·h·g^-1 after 500 cycles. The electro- chemical properties of mesoporous ZnMn2O4 microspheres are better than that for most reported ZnMn2O4. To understand the electrochemical processes on the mesoporous ZnMn2O4 microspheres, in situ Raman spectroscopy is used to investigate the electrode surface. The results show that mesoporous ZnMn2O4 microspheres have a great potential as an alternative to commercial carbon anode materials.

Generalized stability criterion for controlling solidification segregation upon twin-roll casting

Macro-and micro-segregation formed upon twin-roll casting(TRC)can be inherited from sub-rapid solid-ification to solid-state transformation,even to plastic deformation,thus deteriorating drastically mechan-ical properties of as-produced thin sheets.Although many works focusing mainly on controlling fields of thermal,concentration and convection have been reported,how to control artificially and quantitatively the segregation using a theoretical connection between processing parameters and solidification models,has not been realized,yet.Regarding it,a systematical framework integrating non-equilibrium dendritic growth and overall solidification kinetics with the TRC parameters,was constructed applying a general-ized stability(GS)conception deduced from transient thermodynamic driving force△G^(t)and transient ki-netic energy barrier Q_(eff)^(t)evolving upon solidification.Departing from this framework considering synergy of thermodynamics and kinetics(i.e.,thermo-kinetic synergy),a criterion of high△G^(t)-high GS guaranteed that the macro(i.e.,the centerline)and the micro(i.e.,the edge)segregation can be suppressed by in-creasing△G^(t)and GS at the beginning and the ending stage of sub-rapid solidification,respectively.This typical thermo-kinetic combination producing the microstructure can be inherited into the plastic de-formation,as reflected by corresponding strength-ductility combinations.This work realized quantitative controlling of TRC by a theoretical connection between processing parameters and solidification models,where,an optimization for sub-rapid solidification segregation using the GS conception including△G^(t)and Q_(eff)^(t)has been performed.

Neutralization of SARS-CoV-2 pseudovirus using ACE2-engineered extracellular vesicles

The spread of coronavirus disease 2019(COVID-19)throughout the world has resulted in stressful healthcare burdens and global health crises.Developing an effective measure to protect people from infection is an urgent need.The blockage of interaction between angiotensin-converting enzyme 2(ACE2)and S protein is considered an essential target for anti-severe acute respiratory syndrome coronavirus 2(SARS-Co V-2)drugs.A full-length ACE2 protein could be a potential drug to block early entry of SARS-Co V-2 into host cells.In this study,a therapeutic strategy was developed by using extracellular vesicles(EVs)with decoy receptor ACE2 for neutralization of SARS-Co V-2.The EVs embedded with engineered ACE2(EVs-ACE2)were prepared;the EVs-ACE2 were derived from an engineered cell line with stable ACE2 expression.The potential effect of the EVs-ACE2 on anti-SARS-Co V-2 was demonstrated by both in vitro and in vivo neutralization experiments using the pseudovirus with the S protein(S-pseudovirus).EVs-ACE2 can inhibit the infection of S-pseudovirus in various cells,and importantly,the mice treated with intranasal administration of EVs-ACE2 can suppress the entry of S-pseudovirus into the mucosal epithelium.Therefore,the intranasal EVs-ACE2 could be a preventive medicine to protect from SARS-Co V-2 infection.This EVs-based strategy offers a potential route to COVID-19 drug development.

Localized delivery of nanomedicine and antibodies for combating COVID-19

The severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)pandemic has been a major health burden in the world.So far,many strategies have been investigated to control the spread of COVID-19,including social distancing,disinfection protocols,vaccines,and antiviral treatments.Despite the significant achievement,due to the constantly emerging new variants,COVID-19 is still a great challenge to the global healthcare system.It is an urgent demand for the development of new therapeutics and technologies for containing the wild spread of SARS-CoV-2.Inhaled administration is useful for the treatment of lung and respiratory diseases,and enables the drugs to reach the site of action directly with benefits of decreased dose,improved safety,and enhanced patient compliance.Nanotechnology has been extensively applied in the prevention and treatment of COVID-19.In this review,the inhaled nanomedicines and antibodies,as well as intranasal nanodrugs,for the prevention and treatment of COVID-19 are summarized.

Aging Behavior of Nano-SiC/2014Al Composite Fabricated by Powder Metallurgy and Hot Extrusion Techniques

The aging-hardening kinetics of powder metallurgy processed 2014Al alloy and its composite have been studied. The existence of n-SiC particulates leads to the increase of peak hardness. Interestingly, the aginghardening peak of the composite takes place at earlier time than that of the unreinforced alloy. Transmission electron microscopy（TEM） studies indicated that the major precipitation phases are Al_5Cu_2Mn_3 and θ′（Al_2Cu）. Besides, Ω phase appeared in both specimens at peak hardening condition, which has been rarely observed previously in aluminum metal matrix composites without Ag. Accelerated aging kinetics and increased peak hardness may be attributed to the higher dislocation density resulted from the mismatch of coefficients of thermal expansion between n-SiC and 2014Al matrix. The results are beneficial to fabricating high performance composites for the application in automobile field such as pistons, driveshaft tubes, brake rotors, bicycle frames, railroad brakes.

Multi-omics of Circular RNAs and Their Responses to Hormones in Moso Bamboo(Phyllostachys edulis)

Circular RNAs(circRNAs)are endogenous non-coding RNAs with covalently closed structures,which have important functions in plants.However,their biogenesis,degradation,and function upon treatment with gibberellins(GAs)and auxins(1-naphthaleneacetic acid,NAA)remain unknown.Here,we systematically identified and characterized the expression patterns,evolutionary conservation,genomic features,and internal structures of circRNAs using RNase R-treated libraries from moso bamboo(Phyllostachys edulis)seedlings.Moreover,we investigated the biogenesis of circRNAs dependent on both cis-and trans-regulation.We explored the function of circRNAs,including their roles in regulating microRNA(miRNA)-related genes and modulating the alternative splicing of their linear counterparts.Importantly,we developed a customized degradome sequencing approach to detect miRNA-mediated cleavage of circRNAs.Finally,we presented a comprehensive view of the participation of circRNAs in the regulation of hormone metabolism upon treatment of bamboo seedlings with GA and NAA.Collectively,our study provides insights into the biogenesis,function,and miRNA-mediated degradation of circRNAs in moso bamboo.

Inhaled heparin polysaccharide nanodecoy against SARS-CoV-2 and variants

To the Editor:As of January 27,2022,there were 363,062,293 cases and 5,645,884deaths from the COVID-19 pandemic1.The prevalent mutated strains have aggravated the global pandemic2.SARS-Co V-2 is highly mutable,and the mutations on the spike(S)protein resulted in a high transmission of COVID-19 and vaccine breakthrough infection3.For example,there is a notable decrease in neutralizing ability of BNT162b2 vaccination-elicited antibodies against the Delta and other variants4,5,and attenuation of peak viral burden and vaccine effectiveness are reduced with Delta variant6.

Author correction to"Neutralization of SARSCoV-2 pseudovirus using ACE2-engineered extracellular vesicles"[Acta Pharmaceutica Sinica B 12(2022)1523-1533]

The authors regret in the initially published version of this article,there is a misapplied image in Fig.3C.The corrected Fig.3 is provided below.