科学研究的第五范式——以智能驱动的材料设计为例

科学正在进入一个新时代——第五范式——它被认为是知识整合到不同领域的主要特征,是基于无所不在的机器学习系统的计算社区中智能驱动的工作。在此,我们通过在天河一号超级计算机系统上构建的催化材料专门设计的典型平台案例,生动地阐明了第五范式的本质,旨在促进第五范式在其他领域的培养。第五范式平台主要包括模型自动构建(原始数据提取)、指纹自动构建(神经网络特征选择)以及跨学科知识串联的重复迭代(“火山图”)。与分解一起进行的是对迭代中实现的体系结构的性能评估。通过讨论,第五范式的智能驱动平台可以极大地简化和改进研究中极其繁琐和具有挑战性的工作,并通过补偿机器学习中缺少样本和替代一些由于计算资源不足而导致的数值计算来实现数值计算与机器学习之间的相互反馈,从而加速探索过程。在数据驱动的学科中,跨学科专家的协同作用和对动态数据需求的急剧增长仍然是一个挑战。我们相信,对第五范式平台的一瞥可以为其在其他领域的应用铺平道路。

Exosomes from circ-Astn1-modified adipose-derived mesenchymal stem cells enhance wound healing through miR-138-5p/SIRT1/FOXO1 axis regulation

BACKGROUND Wound healing impairment is a dysfunction induced by hyperglycemia and its effect on endothelial precursor cells(EPCs)in type 2 diabetes mellitus.There is increasing evidence showing that exosomes(Exos)derived from adipose-derived mesenchymal stem cells(ADSCs)exhibit the potential to improve endothelial cell function along with wound healing.However,the potential therapeutic mechanism by which ADSC Exos contribute to wound healing in diabetic mice remains unclear.AIM To reveal the potential therapeutic mechanism of ADSC Exos in wound healing in diabetic mice.METHODS Exos from ADSCs and fibroblasts were used for high-throughput RNA sequencing(RNA-Seq).ADSC-Exo-mediated healing of full-thickness skin wounds in a diabetic mouse model was investigated.We employed EPCs to investigate the therapeutic function of Exos in cell damage and dysfunction caused by high glucose(HG).We utilized a luciferase reporter(LR)assay to analyze interactions among circular RNA astrotactin 1(circ-Astn1),sirtuin(SIRT)and miR-138-5p.A diabetic mouse model was used to verify the therapeutic effect of circ-Astn1 on Exo-mediated wound healing.RESULTS High-throughput RNA-Seq analysis showed that circ-Astn1 expression was increased in ADSC Exos compared with Exos from fibroblasts.Exos containing high concentrations of circ-Astn1 had enhanced therapeutic effects in restoring EPC function under HG conditions by promoting SIRT1 expression.Circ-Astn1 expression enhanced SIRT1 expression through miR-138-5p adsorption,which was validated by the LR assay along with bioinformatics analyses.Exos containing high concentrations of circ-Astn1 had better therapeutic effects on wound healing in vivo compared to wild-type ADSC Exos.Immunofluorescence and immunohistochemical investigations suggested that circ-Astn1 enhanced angiopoiesis through Exo treatment of wounded skin as well as by suppressing apoptosis through promotion of SIRT1 and decreased forkhead box O1 expression.CONCLUSION Circ-Astn1 promotes the therapeutic effect of ADSC-Exos and thus improves wound healing in diabetes via miR-138-5p absorption and SIRT1 upregulation.Based on our data,we advocate targeting the circ-Astn1/miR-138-5p/SIRT1 axis as a potential therapeutic option for the treatment of diabetic ulcers.

Strain and interfacial engineering to accelerate hydrogen evolution reaction of two-dimensional phosphorus carbide

Hydrogen,regarded as a promising energy carrier to alleviate the current energy crisis,can be generated from hydrogen evolution reaction(HER),whereas its efficiency is impeded by the activity of catalysts.Herein,effective strategies,such as strain and interfacial engineering,are imposed to tune the catalysis performance of novel two-dimensional(2D)phosphorus carbide(PC)layers using first-principle calculations.The findings show that P site in pristine monolayer PC(ML-PC)exhibits higher HER performance than C site.Intriguingly,constructing bilayer PC sheet(BL-PC)can change the coordinate configuration of P atom to form 3-coordination-P atom(3-co-P)and 4-coordination-P atom(4-co-P),and the original activity of 3-co-P site is higher than the 4-co-P site.When an external compressive strain is applied,the activity of the 4-co-P site is enhanced whereas the external strain can barely affect that of 3-co-P site.Interestingly,the graphene substrate enhances the overall activity of the BL-PC because the graphene substrate optimizes the?GH*value of 4-co-P site,although it can barely affect the HER activity of 3-co-P site and ML-PC.The desirable properties render 2 D PC-based material promising candidates for HER catalysts and shed light on the wide utilization in electrocatalysis.

Analysis of diagnosis and treatment of traditional Chinese medicine for COVID-19 nucleic acid

Since the outbreak of coronavirus disease 2019(COVID-19),the author has been involved in the treatment of COVID-19 in the first line.It is found that some patients had a long viral nucleic acid negative time,and even the course of the disease lasted more than 40 days.After a thorough investigation of the root causes,it is found the four possible causes were:"Blood stasis syndrome"is difficult to remove;"Damp heat"sticky greasy;Stubborn basic diseases;weak constitution.All the patients treated with traditional Chinese medicine have turned negative,and now the typical cases were analyzed and summarized in order to provide reference for the traditional Chinese medicine treatment and scientific research of the patients with COVID-19 who were difficult to turn negative.

Competitive assembling strategy to construct carbon nitride homojunctions for boosting photocatalytic performance

Both morphology and composition have a great influence on the properties and functions of materials,however,how to rational modulate both of them to achieve their synergistic effects has been a longstanding expectation.Herein,we demonstrate a competitive assembling strategy for the construction of metal-free graphite carbon nitride(CN)homojunctions in which morphology and composition can be easily controlled simultaneously by only changing the ratio of assembly raw materials.These homojunctions are comprised of porous nanotubular S-doped CN(SCN)grafted with CN nanovesicles,which are derived from thermal polycondensation of melamine-thiocyanuric acid(M-T)/melamine-cyanuric acid(M-C)supramolecular hybrid blocks.This unique architecture and component engineering endows the novel SCN-CN homojunction with abundant active sites,enhanced visible trapping ability,and intimate interface contact.As a result,the synthesized SCN-CN homojunctions demonstrate high photocatalytic activity for hydrogen evolution and pollutant degradation.This developed strategy opens up intriguing opportu-nities for the rational construction of intricate metal-free heterostructures with controllable architecture and interfacial contact for applications in energy-related fields.

Evaluation of service-induced microstructural damage for directionally solidified turbine blade of aircraft engine

Turbine blades of gas turbine engines usually suffer from severe operational conditions characterized by high temperature and stress. Severe operational conditions during service cause microstructural changes in turbine blades and degrade their mechanical properties. In this study, service-induced microstructural damages in serviced turbine blades manufactured from a directionally solidified superalloy were evaluated. The observed microstructural damage of the turbine blade mainly involves the coarsening and rafting of γ' precipitates. The leading edge of 60% height of the turbine blades undergone most severe microstructural damage with significant microstructural evolution at this area. Microstructural damage affects the mechanical properties such as Vickers hardness, that is,Vickers hardness decreases as the equivalent diameter decreases. Microstructural damage shows great positiondependent feature as service temperature and radial stress on blade changes. With the aid of energy-dispersive spectrometer(EDS) analysis on carbide, the transformation of carbide does not exist. In addition, no topological closed-packed phase exists in the turbine blade.

Facile synthesis and superior photocatalytic and electrocatalytic performances of porous B-doped g-C_3N_4 nanosheets

As a low-cost visible-light-driven metal-free catalyst, graphitic carbon nitride(g-CN) has attracted increasing attention due to its wide applications for solar energy conversion, environmental purification,and organic photosynthesis. In particular, the catalytic performance of g-CNcan be easily modulated by modifying morphology, doping, and copolymerization. Simultaneous optimization, however, has little been achieved. Herein, a facile one-pot strategy is developed to synthesize porous B-doped g-CNnanosheets by using HBOand urea as the precursor during thermal polymerization. The resultant B-doped g-CNnanosheets retain the original framework of bulk g-CN, while induce prominently enhanced visible light harvesting and narrowing band gap by 0.32 eV compared to pure g-CN. Moreover, the adsorption capacity and photodegradation kinetics of methylene blue(MB) under visible light irradiation over B-doped g-CNnanosheets can be improved by 20.5 and 17 times, respectively. The synthesized porous B-doped g-CNnanosheets also exhibit higher activities than pure g-CNas bifunctional electrocatalyst for both oxygen evolution reaction(OER) and oxygen reduction reaction(ORR). The enhanced catalyst performance of porous B-doped g-CNnanosheets stems from the strong synergistic effect originating from the larger exposed active sites generated by the exfoliation of g-CNinto nanosheets and the porous structure, as well as the better conductivity owing to B-doping. This work provides a simple, effective, and robust method for the synthesis of g-CN-based nanomaterial with superior properties to meet the needs of various applications.

Amorphous B-doped graphitic carbon nitride quantum dots with high photoluminescence quantum yield of near 90% and their sensitive detection of Fe^(2+)/Cd^(2+)

Graphitic carbon nitride quantum dots(CNQDs) are emerging as attractive photoluminescent(PL)materials with excellent application potential in fluorescence imaging and heavy-metal ion detection. However, three limitations, namely, low quantum yields(QYs), self-quenching,and excitation-dependent PL emission behaviors, severely impede the commercial applications of crystalline CNQDs.Here we address these three challenges by synthesizing borondoped amorphous CNQDs via a hydrothermal process followed by the top±down cutting approach. Structural disorder endows the amorphous boron-doped CNQDs(B-CNQDs)with superior elastic strain performance over a wide range of pH values, thus effectively promoting mass transport and reducing exciton quenching. Boron as a dopant could fine-tune the electronic structure and emission properties of the PL material to achieve excitation-independent emission via the formation of uniform boron states. As a result, the amorphous B-CNQDs show unprecedented fluorescent stability(i.e., no obvious fading after two years) and a high QY of 87.4%;these values indicate that the quantum dots obtained are very promising fluorescent materials. Moreover, the B-CNQDs show bright-blue fluorescence under ultraviolet excitation when applied as ink on commercially available paper and are capable of the selective and sensitive detection of Fe^(2+) and Cd^(2+) in the parts-per-billion range. This work presents a novel avenue and scientific insights on amorphous carbon-based fluorescent materials for photoelectrical devices and sensors.

Chlorine doped graphitic carbon nitride nanorings as an efficient photoresponsive catalyst for water oxidation and organic decomposition

Rationally engineering the microstructure and electronic structure of catalysts to induce high activity for versatile applications remains a challenge. Herein, chlorine doped graphitic carbon nitride(Cl-doped g-C3N4) nanorings have been designed as a superior photocatalyst for pollutant degradation and oxygen evolution reaction(OER). Remarkably, Cl-doped g-C3N4 nanorings display enhanced OER performance with a small overpotential of approximately 290 m V at current density of 10 m A cm^-2 and Tafel slope of 83 m V dec-1, possessing comparable OER activity to precious metal oxides RuO2 and IrO2/C. The excellent catalytic performance of Cl-doped g-C3N4 nanorings originates from the strong oxidation capability,abundant active sites exposed and efficient charge transfer. More importantly, visible light irradiation gives rise to a prominent improvement of the OER performance, reducing the OER overpotential and Tafel slope by 140 m V and 28 m V dec^-1, respectively, demonstrating the striking photo-responsive OER activity of Cl-doped g-C3N4 nanorings. The great photo-induced improvement in OER activity would be related to the efficient charge transfer and the·OH radicals arising spontaneously on CN-Cl100 catalyst upon light irradiation. This work establishes Cl-doped g-C3N4 nanorings as a highly competitive metal-free candidate for photoelectrochemical energy conversion and environmental cleaning application.

Design of an ultrasonic motor with multi-vibrators

This paper presents and verifies a new idea for constructing an ultrasonic motor （USM）. The stator contains several vibrators fabricated by bonding piezoelectric ceramics （PZTs） to a metal base. When two alternating current （AC） voltages with a 90° phase difference are applied to the PZTs, longitudinal and bending modes are excited in the vibrator. The bending vibrations of the vibrators are stacked to form the torsional vibration of the stator, ultimately generating longitudinal-torsional composite vibration. Both vibrators and the stator are excited to the resonance state. A standing wave is formed by superposition of longitudinal and torsional modes. The proposed motor is an in-plane vibration motor because the vibrations of the stator are in the circumferential plane. The finite element method （FEM） is used to validate the feasibility of the proposed motor. The fabricated stator contains five vibrators. The tested resonance frequencies of longitudinal and torsional modes are 44.42 kHz and 43.83 kHz, respectively. The stall torque is 0.3 N＇m and no-load speed is 45 r/min. The highest efficiency is 30%. The applied driving voltage is 100 Vo.p （peak voltage） at 43.9 kHz. The designed motor is a parallel-actuated integral motor. It allows the vibrators to operate synchronously, and overcomes asynchronous issues that occur in traditional multi-vibrator motors.

Acid-induced topological morphology modulation of graphitic carbon nitride homojunctions as advanced metal-free catalysts for OER and pollutant degradation

Topological morphology that dominates the surface electronic properties of nanostructures plays a key role in producing desired materials for versatile functions and applications in many fields,but its modulation for specific functions remains a big challenge.Herein,we report an acid-induced method to prepare S-doped graphitic carbon nitride/graphitic carbon nitride(S-CN/CN)homojunction by simply pyrolyzing a supramolecular precursor synthesized from melamine and H_(2)SO_(4).The topological morphology and electronic structure of CN homojunction can be easily adjusted only by changing the ratio of raw materials.Moreover,the topological morphology of S-CN/CN homojunction can be further adjusted from hollow cocoon to 2D nanosheets by changing the annealing conditions.The optimized S-CN/CN homojunction shows highly efficient in charge transfer and separation and exhibits superior OER activity and high ability to degrade organic pollutants.Impressively,S-CN/CN nanosheets only demand low overpotential of301 m V to drive a current density of 10 m Acm^(-2)in 1 M KOH media,and the corresponding Tafel slope is only 57.71 m V/dec,which is superior to the most advanced precious metal Ir O_(2)catalyst.Moreover,under visible light irradiation,its photodegradation kinetic rate of Rh B is 2.38,which is 47.6 times higher than that of bulk CN.This work provides useful guidance for designing and developing efficient multifunctional metal-free catalysts.

Effects of coke charging pattern on burden movement in COREX melter gasifier based on physical simulation

A three-dimensional semicircle cold model of COREX melter gasifier(MG)was established,and the effects of coke charging pattern on burden movement were investigated by adopting this model.The burden flow pattern of packed bed was measured with different coke charging amounts,coke charging positions,and coke sizes.The results show that the solid flow pattern presents a change from straight line type to reverse U type and finally to W type in MG with traditional coke charging,while the burden flow pattern experiences the change from straight line type to W type with platform and finally W type under center coke charging,and the solid flow pattern presents a change from straight line type to W type with platform and finally W type under intermediate coke charging.The difference demonstrates that coke charging pattern affects the uniform descending in MG to some degree.The burden in the coke charging zone keeps a straight line descending.No matter what kind of coke charging pattern is adopted,the burden residence time is shortened with the increase in coke charging amount,and the vertex of deadman decreases obviously,which is conducive to the renewal of the deadman.The appropriate coke charging amount and coke size should be well controlled at 8.7%and 5 mm,respectively.The results are useful not only in developing further understanding of solid flow in MG but also in verifying different mathematical models,particularly the coupled discrete element method with computational fluid dynamics simulation which has been increasingly used in the literature.