The enzymatic depolymerization of polyethylene terephthalate(PET)offers a sustainable approach for the recycling of PET waste.Great efforts have been devoted to engineering PET depolymerases on the substrate binding c...The enzymatic depolymerization of polyethylene terephthalate(PET)offers a sustainable approach for the recycling of PET waste.Great efforts have been devoted to engineering PET depolymerases on the substrate binding cleft and the surrounding loops/α-helices on the surface.Here,we report the systematic engineering of whole β-sheet regions in the core of IsPETase(a PETase from Ideonella sakaiensis)via a fluorescent high-throughput screening assay.Twenty-one beneficial substitutions were obtained and iteratively recombined.The best variant,DepoPETase β,with an increase in the melting temperatures(T_(m))of 22.9℃,exhibited superior depolymerization performance and enabled complete depolymerization of100.5 g of untreated post-consumer PET(pc-PET;0.26% W_(enzyme)/W_(PET) enzyme loading)in liter-scale bioreactor at 50℃within 4 d.Crystallization and molecular dynamics simulations revealed that the improved activity and thermostability of DepoPETase β were due to enhanced hydrogen bonds and salt bridges in the β-sheet region,a more tightly packed structure of the core sheets and the surrounding helix,and improved binding of PET to the active sites.This study not only demonstrates the importance of engineering strategy in theβ-sheet region of PET hydrolases but also provides a potential PET depolymerase for large-scale PET recycling.展开更多
This study investigates the corrosion inhibition potential of Datura stramonium seed extracts on mild steel in 1.0 mol·L^(-1)HCl and 0.5 mol·L^(-1)H_(2)SO_(4),utilizing both ethanolic and aqueous extracts as...This study investigates the corrosion inhibition potential of Datura stramonium seed extracts on mild steel in 1.0 mol·L^(-1)HCl and 0.5 mol·L^(-1)H_(2)SO_(4),utilizing both ethanolic and aqueous extracts as ecofriendly inhibitors.Electrochemical techniques,thermodynamic studies,and quantum chemical calculations were employed to evaluate the adsorption mechanism and inhibitory action at the metal/electrolyte interface.Maximum inhibition efficie ncies of 93.1%in HCl and 97.7%in H_(2)SO_(4) were achieved with the ethanolic extract at a concentration of 0.2 g·L^(-1),while the aqueous extract demonstrated 93.8%inhibition in HCl and 96.6%in H_(2)SO_(4).Polarization curves indicated mixed-type inhibition with a slight anodic bias.The thermodynamic analysis of two extracts in both environments indicated that the K_(ads)increased and that theΔG_(ads)were close to-40 kJ·mol^(-1),suggesting that the adsorption followed the Langmuir isotherm,indicating a combination of physical and chemical adsorption.SEM/EDX analysis confirmed the formation of a protective layer,while quantum chemical studies further validated strong adsorption,evidenced by a lowΔE of 2.396 eV and an adsorption energy of-878 kcal·mol^(-1)(1kcal·mol^(-1)=4.18 kJ·mol^(-1)).These results demonstrate that Datura stramonium extracts are promising inhibitors,particularly in sulfuric acid,for industrial applications.Reason:Improved clarity,vocabulary,and technical accuracy while maintaining the original meaning.展开更多
Nucleation,which is the initial step of crystallization,critically governs the polymer crystallization behavior,influencing the crystallization temperature,kinetics,and morphology.However,the direct observation of the...Nucleation,which is the initial step of crystallization,critically governs the polymer crystallization behavior,influencing the crystallization temperature,kinetics,and morphology.However,the direct observation of the nucleation process in polymers remains elusive owing to spatial and temporal resolution limitations.This feature article summarizes the recent progress in understanding polymer nucleation within confined and interface-dominated environments,focusing on three representative systems:anodic aluminum oxide templates and nanocomposites containing nanoparticles or nanosheets.The interplay between finite size and interfacial effects has revealed some novel phenomena,such as homogeneous nucleation,surface nucleation,prefreezing,and supernucleation.展开更多
To study the distribution law and random characteristics of casting defects in steel castings,24 civil engineering structural cast steel joints were divided into two groups:simple cast steel joints and complex cast st...To study the distribution law and random characteristics of casting defects in steel castings,24 civil engineering structural cast steel joints were divided into two groups:simple cast steel joints and complex cast steel joints.Three kinds of nondestructive testing(NDT)methods,namely,visual,magnetic particle,and ultrasonic inspections,were used to detect the macroscopic defects in joints.The NDT results were then statistically analyzed.The results show that the unfused core support is a common defect of complex cast steel joints,and the defect can be seen visually,so excavation and repair welding should be carried out before castings leave factories.Casting cracks are extremely likely to occur in the intersection area of tubes,which is called the ultrasonic inspection blind zone.The occurrence probability of gas pores on simple cast steel joints is the largest,and the occurrence probability of core support incomplete fusions on complex cast steel joints is the largest.However,when cast steel joints are counted as a whole sample,the occurrence probability of gas pores is larger than that of core support incomplete fusions.Therefore,it is the most common defect in cast steel joints.展开更多
In this paper, we review our recent progress in the synthesis and application of styryl-capped polypropylene （PP-t- St）, an excellent reactive polyolefin that is both convenient and efficient in synthesis and facile...In this paper, we review our recent progress in the synthesis and application of styryl-capped polypropylene （PP-t- St）, an excellent reactive polyolefin that is both convenient and efficient in synthesis and facile and versatile in application for preparing advanced polypropylene materials via macromolecular engineering. The synthesis of PP-t-St is made possible by a unique chain transfer reaction coordinated by a bis-styrenic molecule, such as 1,4-divinylbenzene （DVB） and 1,2-bis（4- vinylphenyl）ethane （BVPE）, and hydrogen in typical C2-symmetric metallocene （e.g. rac-Me2Si（2-Me-4-Ph-Ind）2ZrC12, in association with methylaluminocene, MAO） catalyzed propylene polymerization. The regio-selective 2,1- insertion of the styrenic double bond in DVB or BVPE into the overwhelmingly 1,2-fashioned Zr-PP propagating chain enables substantial dormancy of the catalyst active site, which triggers selective hydrogen chain transfer that, with the formed Zr-H species ultimately saturated by the insertion of propylene monomer, results in an exclusive capping of the afforded PP chains by styryl group at the termination end. With a highly reactive styryl group at chain end, PP-t-St has been used as a facile building block in PP macromolecular engineering together with the employment of state-of-the-art synthetic polymer chemistry to fabricate broad types of new polypropylene architectures.展开更多
In this study, porous polylactide（PLA） microspheres with different structures were prepared through the multiple emulsion solvent evaporation method. By changing organic solvents（ethyl acetate and chloroform） and ...In this study, porous polylactide（PLA） microspheres with different structures were prepared through the multiple emulsion solvent evaporation method. By changing organic solvents（ethyl acetate and chloroform） and adding effervescent salt NH4 HCO3 in the inner water phase, microspheres with porous capsular, matrix, microcapsular and multivesicular structures were prepared. The protein encapsulation and release, and the cell growth behavior of porous microspheres were further explored. Under the same inner water phase, microspheres prepared with chloroform had higher protein encapsulation efficiency and less protein release rate as compared with those prepared with ethyl acetate. Cell experiments showed that the relatively rough surface of microspheres prepared with chloroform was more favorable for the cell growth in comparison with the smooth surface of microspheres prepared with ethyl acetate. This study shows a simple and effective method to control the protein release and cell growth behaviors of polymer microspheres by tuning their porous structure.展开更多
A buckling-restrained steel plate shear wall(BRSPSW)structure with butterfly-shaped links on the lateral sides is introduced to improve the cooperative perfor-mance between the BRSPSW and the boundary frames.A one-spa...A buckling-restrained steel plate shear wall(BRSPSW)structure with butterfly-shaped links on the lateral sides is introduced to improve the cooperative perfor-mance between the BRSPSW and the boundary frames.A one-span two-story concrete-filled steel tube(CFT)column frame specimen equipped with lateral-side butterfly-shaped linked BRSPSWs(LBL-BRSPSWs)is evaluated under low-cycle reversed loading.A finite element(FE)model is developed and validated based on the test results.This FE model accurately simulates the failure modes and load-dis-placement curves.Parametric analyses are conducted on the butterfly-shaped links.The results show that the interactions between the CFT column frame and LBL-BRSPSWs are sig-nificantly influenced by the width ratio of the butterfly-shaped links,while the taper ratio and aspect ratio have relatively minor influences.Compared with traditional steel shear walls with four-sided connections,LBL-BRSPSWs reduce the additional axial forces and bending moments in the frame columns by 28%to 73%and 17%to 87%,respectively,with only a 9%to 30%decrease in the lateral resistance.The experimental and parametric analysis results indicate that setting butterfly-shaped links on the lateral sides of BRSPSWs can significantly enhance their cooperative performance with the boundary frame.The butterfly-shaped link width ratio has a linear relationship with the lateral-resistance performance of the specimens and the additional internal forces in the frame columns.To ensure that LBL-BRSPSW fails prior to the column frames,the link width ratio should be optimized.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
In this paper,we have calculated the structural,electronic,and optical properties of chalcogenide stannite Cu_(2)CdSnX4(X=S,Se,Te) materials.The calculations are based on the density functional theory (DFT) method and...In this paper,we have calculated the structural,electronic,and optical properties of chalcogenide stannite Cu_(2)CdSnX4(X=S,Se,Te) materials.The calculations are based on the density functional theory (DFT) method and are performed using the Cambridge sequential total energy package (CASTEP) code included in the Biovia Material Studio 20 software.All optical properties have been studied in a domain that extends energetically from 10 meV to 40 eV.Our results show that Cu_(2)CdSnX4(X=S,Se,Te) stannite exhibits absorption in the visible region,the refractive index decreases with increasing energy,and the refractive index values are n=3.2,3.73 and 3.75 for Cu_(2)CdSnS_(4),Cu_(2)CdSnSe_(4)and Cu_(2)CdSnTe_(4),respectively.They show also high conductivity,which implies that this material is promising for solar cells.These results argue in favor of the use of these materials in various potential applications.The density of state,band structures,and structural properties of Cu_(2)CdSnX4(X=S,Se,and Te) stannite are also studied in this work.展开更多
The rapid growth of the global population,coupled with increasing pollution levels,highlights the urgent need for sustainable and eco-friendly construction materials,such as unfired clay bricks.However,their widesprea...The rapid growth of the global population,coupled with increasing pollution levels,highlights the urgent need for sustainable and eco-friendly construction materials,such as unfired clay bricks.However,their widespread adoption remains limited due to certain performance drawbacks,particularly in thermal insulation,a critical factor in addressing climate change challenges.In this study,a plant-based waste-derived biopolymer was incorporated into unfired clay bricks to enhance their physicochemical and thermomechanical properties.The biopolymer was added at six different weight fractions(0%,1%,3%,7%,15%,and 20%)to systematically evaluate its impact on bulk density,porosity,capillary water absorption,thermal conductivity,specific heat capacity,and compressive strength.The results revealed a gradual decrease in porosity as the biopolymer content increased,leading to a 41%improvement in thermal conductivity at 20 wt%.However,the optimal balance between thermal efficiency and compressive strength was achieved at 7 wt%biopolymer;this result has been verified through a combination of experimental methods and modeling.Additionally,TRNSYS simulations confirmed the enhanced thermal performance,demonstrating a 9.74%increase in time lag and a 16%reduction in decrement factor,both of which contribute to optimizing building energy efficiency.Overall,this approach not only helps reduce environmental pollution but also enhances insulation capacity while lowering heating and cooling demands,thereby improving overall building performance.Biopolymer-reinforced unfired clay bricks thus represent a promising solution for advancing a low-carbon and sustainable construction industry,aligning with the United Nations Sustainable Development Goals(SDGs)for climate change mitigation and responsible resource management.展开更多
The production of cement and concrete using carbonated steel slag as a supplementary cementitious material achieves the dual benefits of efficient steel slag utilization and CO_(2)fixation.In this study,a combination ...The production of cement and concrete using carbonated steel slag as a supplementary cementitious material achieves the dual benefits of efficient steel slag utilization and CO_(2)fixation.In this study,a combination of microbial technology and a rotary kiln process was employed to expedite the carbonation of steel slag for fixation from cement kiln flue gas.This approach resulted in a significant increase in the CO_(2)-fixation rate,with a CO_(2)-fixation ratio of approximately 10%achieved within 1 h and consistent performance across different seasons throughout the year.Investigation revealed that both the CO_(2)-fixation ratio and the particle fineness are pivotal for increasing the soundness and reactivity of steel slag.When the CO_(2)-fixation ratio exceeds 8%and the specific surface area is at least 300 m2∙kg−1,the soundness issue of steel slag can be effectively addressed,facilitating the safe utilization of steel slag.Residual microbes present in the carbonated steel slag powder act as nucleating sites,increasing the hydration rate of the silicate phases in Portland cement to form more hydration products.Microbial regulation results in the biogenic calcium carbonate having smaller crystal sizes,which facilitates the formation of monocarboaluminate to increase the strength of hardened cement paste.At the same CO_(2)-fixation ratio,microbial mineralized steel slag powder exhibits greater hydration activity than carbonated steel slag powder.With a CO_(2)-fixation ratio of 10%and a specific surface area of 600 m^(2)∙kg^(−1),replacing 30%of cement clinker with microbial mineralized steel slag powder yields an activity index of 87.7%.This study provides a sustainable solution for reducing carbon emissions and safely and efficiently utilizing steel slag in the construction materials sector,while expanding the application scope of microbial technology.展开更多
Plasma,the fourth state of matter,is characterized by the presence of charged particles,including ions and electrons.It has been shown to induce unique physical and chemical reactions.Recently,there have been increase...Plasma,the fourth state of matter,is characterized by the presence of charged particles,including ions and electrons.It has been shown to induce unique physical and chemical reactions.Recently,there have been increased applications of plasma technology in the field of multiscale functional materials'preparation,with a number of interesting results.This review will begin by introducing the basic knowledge of plasma,including the definition,typical parameters,and classification of plasma setups.Following this,we will provide a comprehensive review and summary of the applications(phase conversion,doping,deposition,etching,exfoliation,and surface treatment)of plasma in common energy conversion and storage systems,such as electrocatalytic conversion of small molecules,batteries,fuel cells,and supercapacitors.This article summarizes the structure-performance relationships of electrochemical energy conversion and storage materials(ECSMs)that have been prepared or modified by plasma.It also provides an overview of the challenges and perspectives of plasma technology,which could lead to a new approach for designing and modifying electrode materials in ECSMs.展开更多
Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rat...Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rates,and adequate strength remains a significant challenge for cemented rockfill.This study used a composite alkali activator to activate gangue cemented rockfill.The compressive strength,scanning electron microscopy,energy dispersive spectrometer,mercury intrusion porosimetry,X-ray diffraction,and thermogra-vimetric tests were carried out to investigate the effect of the composite alkali activator proportion on the compressive strength,micro-structure,and composition of the cemented rockfill.The calcium silicate hydrate(C–S–H)molecular model of cemented rockfill was con-structed to explore the fracture evolution of the nucleated molecular structure under tension.The results show that compressive strength initially increased and then decreased with the activator proportion,the optimal activator proportion of 1:2 resulted in a 31.25%increase in strength at 3 d.This reasonable activator proportion strengthens the pozzolanic effect of gangue,and consumes more calcium hydroxide to inhibit its agglomeration,ultimately achieving the densification of microstructure.The activator proportion inevitably substitutes calcium ions with sodium ions in the C–S–H molecular model.The 12%substitution of calcium ions increases the adhesion between silicon chain layers,which is beneficial to the interlayer stress transfer.This work proposes a method for preparing low-cost cemented rockfill from al-kali-activated gangue,which can be used for solid waste recycling and reducing cement consumption to achieve low-carbon goals.展开更多
In November 2024,the Global Solar Council announced that the world cumulative solar capacity reached 2 terawatts,twice as much as in mid-2022,clearly showing that solar energy is set to lead the energy transition.
Polybutene-1(PB-1) is a semi-crystalline polymer with excellent mechanical properties. However, its practical application is significantly hindered by the slow Form Ⅱ-Ⅰ transition, which can take up to several days ...Polybutene-1(PB-1) is a semi-crystalline polymer with excellent mechanical properties. However, its practical application is significantly hindered by the slow Form Ⅱ-Ⅰ transition, which can take up to several days to complete. While prior research established that long-chain branching(LCB) structures synthesized via ω-alkenylmethyldichlorosilane copolymerization-hydrolysis(ACH) chemistry markedly accelerate this transition, this work demonstrates that H-shaped LCB structures constructed through copolymerization with 1,9-decadiene exhibit the capability to facilitate Form Ⅱ-Ⅰ transition in most systems evaluated herein. However, low branching efficiency concurrently generates extended alkyl pendant chains, which impose pronounced steric-hindrance-driven suppression on the transition kinetics, thereby substantially diminishing the net acceleration effect of the LCB structures, even resulting in a net retardation effect in certain systems. Notably, a significant synergistic acceleration effect emerged between the H-shaped LCB structures and propylene comonomer units. These findings confirm that the H-shaped LCB structures play a role in promoting the Form II-I transformation process, which is independent of the synthetic pathways, thereby providing more strategies for addressing the long-standing processing problems of PB-1.展开更多
In this article,we have modeled the astroclimatic parameters using data from the fifth reanalysis series(ERA5)from the European Centre for Medium-Range Weather Forecasts over the period 2010-2020.These data have been ...In this article,we have modeled the astroclimatic parameters using data from the fifth reanalysis series(ERA5)from the European Centre for Medium-Range Weather Forecasts over the period 2010-2020.These data have been projected onto the site of the Roque de los Muchachos Observatory(ORM).The analysis covers the main parameters influencing the quality of astronomical observation,notably the vertical profiles of temperature,potential temperature,and optical turbulence(C_(n)~2),as well as the vertical wind distributions and seasonal behaviors of atmospheric turbulence,which are treated in detail by specifying the wind speed at the 200 hPa level(V200).Around this level,the wind at high altitude presents moderate speeds and a generally stable direction,conditions favorable for adaptive optics.The thermal profiles show good agreement with standard atmospheric models,with a well-defined tropopause and a stable stratosphere,as well as the integrated parameters such as seeing(free and total),isoplanatic angle,and coherence time.The results reveal a stratified and stable atmosphere,with turbulence predominantly concentrated in the lower troposphere.The thermal profiles show a good agreement with standard atmospheric models,with a well-defined tropopause and a stable stratosphere.The seasonality of the astroclimatic parameters indicates conditions particularly favorable for observation during the winter months,with the median of free seeing,total seeing,isoplanatic angle and a coherence time as respectively 0″.48,0″.72,2″,and 6 ms.These results confirm the strong potential of ORM as a reference astronomical site,capable of hosting high-precision observation instruments.The methodological approach employed also provides a replicable basis for the characterization of other candidate sites for the installation of ground-based telescopes.As a preliminary study,this work establishes a scientific basis for further on-site monitoring and detailed characterization of the ORM site.展开更多
The primary objective of this study is to develop an innovative theoretical model to accurately predict the thermophysicalproperties of hybrid nanofluids designed to enhance cooling in solar panel applications.This re...The primary objective of this study is to develop an innovative theoretical model to accurately predict the thermophysicalproperties of hybrid nanofluids designed to enhance cooling in solar panel applications.This researchlays the groundwork for our future studies,which will focus on photovoltaic thermal applications.These nanofluidsconsist of water and nanoparticles of alumina(Al_(2)O_(3)),titanium dioxide(TiO_(2)),and copper(Cu),exploringvolumetric concentrations ranging from 0%to 4%for each type of nanoparticle,and up to 10%for total mixtures.The developed model accounts for complex interactions between the nanoparticles and the base fluid,as well assynergistic effects resulting from the coexistence of different nanoparticles.Detailed simulations have shownexceptional agreement with experimental results,reinforcing the credibility of our approach in accurately capturingthe thermophysical behavior of these hybrid nanofluids.Based on these results,our study proposes significantadvancements in the design and optimization of nanofluids for cooling applications in solar panels.These developmentsare crucial for improving the efficiency of solar installations by mitigating overheating effects,providinga solid foundation for practical applications in this rapidly evolving field.展开更多
Aiming at the gas discharge problem in electric aircraft,this work studies the gas discharge characteristics at low-temperature sub-atmospheric pressure.A gas discharge shooting platform was built,and the discharge pr...Aiming at the gas discharge problem in electric aircraft,this work studies the gas discharge characteristics at low-temperature sub-atmospheric pressure.A gas discharge shooting platform was built,and the discharge process was photographed by intensified charge-coupled device(ICCD).A two-dimensional axisymmetric model of needle-plate electrode gas discharge was established,and three sets of Helmholtz equations were used to solve the photoionization.The results show that under the same voltage,the electric field intensity in the discharge process increases first,then decreases and finally increases again.The discharge speed increases with the increase of altitude,and the electron density in the streamer decreases with the increase of altitude.The development speed of the streamer in the middle stage is higher than that in the early stage,and the speed increases more obviously with the increase of altitude.The development speed of the streamer in the later stage is lower than that in the middle stage,but with the increase of altitude,the development speed of the streamer in the later stage is higher than that in the middle stage.展开更多
Chiral N-substituted amino amides and esters are ubiquitous scaffolds in pesticides and pharmaceutical chemicals,but their asymmetric synthesis remains challenging especially for those with multiple chiral centers.In ...Chiral N-substituted amino amides and esters are ubiquitous scaffolds in pesticides and pharmaceutical chemicals,but their asymmetric synthesis remains challenging especially for those with multiple chiral centers.In this study,IR104 from Streptomyces aureocirculatus was identified from 157 wild-type imine reductases for the synthesis of(S)-2-((R)-2-oxo-4-propylpyrrolidin-1-yl)butanamide(antiepileptic drug Brivaracetam)via dynamic kinetic resolution reductive amination from ethyl 3-formylhexanoate and(S)-2-aminobutylamide with high diastereoselectivity.To further improve the catalytic efficiency of IR104,its mutant D191E/L195I/E253S/M258A(M3)was identified by saturation mutagenesis and iterative combinatorial mutagenesis,which exhibited a 102-fold increase in the catalytic efficiency relative to that of wild-type enzyme and high diastereoselectivity(98:2 d.r.).Crystal structural analysis and molecular dynamics simulations provided some insights into the molecular basis for the improved activity of the mutant enzyme.The imine reductase identified in this study could accept chiral amino amides/esters as amino donors for the dynamic kinetic resolution reductive amination of racemicα-substituted aldehydo-esters,expanding the substrate scope of imine reductases in the dynamic kinetic resolution-reductive amination.Finally,IR104-M3 was successfully used for the preparation of Brivaracetam at gram scale.Using this mutant,various N-substituted amino amides/esters with two chiral centers were also synthesized with up to 99:1 d.r.and 96%yields and subsequently converted intoγ-andδ-lactams,providing an efficient protocol for the synthesis of these important compounds via enzymatic dynamic kinetic resolution-reductive amination from simple building blocks.展开更多
The study aimed to address the issue of elevated residual stress levels in dissimilar girth welds of cast steel joints.To achieve this,the hybrid welding technology,which yields high welding speeds while simultaneousl...The study aimed to address the issue of elevated residual stress levels in dissimilar girth welds of cast steel joints.To achieve this,the hybrid welding technology,which yields high welding speeds while simultaneously reducing residual stresses,has been introduced.This study utilizes a numerical simulation method to investigate the temperature and residual stress field in the hybrid welding of G20Mn5 casting-Q355 low-alloy steel welded pipe.A com-parison of the findings of this study with those of other welding processes revealed the technological advantages of hybrid welding.The research outcomes show that due to geometric discontinuities and material differences,the temperature field of the joint exhibits uneven distribution characteristics,and the peak temperatures on the Q355 steel side exceeds those on the G20Mn5 steel side.An evident stress gra-dient is present in the residual stress field of the joint post-welding,with peak stress located at the weld root on the Q355 steel.Compared with arc welding,the hybrid welding leads to decreased residual stresses and deformation,with high stress outside the heat-affected zone diminishing rapidly.Furthermore,it significantly improves the welding efficiency.This study elucidates the distribution and underlying causes of thermal and residual stress fields in dissimilar girth welds.This serves as a foundation for the application of hybrid welding technology in welded cast steel joints.展开更多
基金funded by the National Key Research and Development Program of China(2023YFC3903300)the Tianjin Synthetic Biotechnology Innovation Capacity Improvement Project(TSBICIPIJCP-003,TSBICIP-KJGG-009-0203,and TSBICIP-BRFI-005)the Innovation Fund of Haihe Laboratory of Synthetic Biology(22HHSWSS00018)。
文摘The enzymatic depolymerization of polyethylene terephthalate(PET)offers a sustainable approach for the recycling of PET waste.Great efforts have been devoted to engineering PET depolymerases on the substrate binding cleft and the surrounding loops/α-helices on the surface.Here,we report the systematic engineering of whole β-sheet regions in the core of IsPETase(a PETase from Ideonella sakaiensis)via a fluorescent high-throughput screening assay.Twenty-one beneficial substitutions were obtained and iteratively recombined.The best variant,DepoPETase β,with an increase in the melting temperatures(T_(m))of 22.9℃,exhibited superior depolymerization performance and enabled complete depolymerization of100.5 g of untreated post-consumer PET(pc-PET;0.26% W_(enzyme)/W_(PET) enzyme loading)in liter-scale bioreactor at 50℃within 4 d.Crystallization and molecular dynamics simulations revealed that the improved activity and thermostability of DepoPETase β were due to enhanced hydrogen bonds and salt bridges in the β-sheet region,a more tightly packed structure of the core sheets and the surrounding helix,and improved binding of PET to the active sites.This study not only demonstrates the importance of engineering strategy in theβ-sheet region of PET hydrolases but also provides a potential PET depolymerase for large-scale PET recycling.
基金supported by the NRF(National Research Foundation)of Koreafunded by the Basic Science Research Program through the Ministry of Education(2020R1I1A3052258)carried out with the support of the“2024 System Semiconductor Technology Development Support Project”of Chungbuk Technopark。
文摘This study investigates the corrosion inhibition potential of Datura stramonium seed extracts on mild steel in 1.0 mol·L^(-1)HCl and 0.5 mol·L^(-1)H_(2)SO_(4),utilizing both ethanolic and aqueous extracts as ecofriendly inhibitors.Electrochemical techniques,thermodynamic studies,and quantum chemical calculations were employed to evaluate the adsorption mechanism and inhibitory action at the metal/electrolyte interface.Maximum inhibition efficie ncies of 93.1%in HCl and 97.7%in H_(2)SO_(4) were achieved with the ethanolic extract at a concentration of 0.2 g·L^(-1),while the aqueous extract demonstrated 93.8%inhibition in HCl and 96.6%in H_(2)SO_(4).Polarization curves indicated mixed-type inhibition with a slight anodic bias.The thermodynamic analysis of two extracts in both environments indicated that the K_(ads)increased and that theΔG_(ads)were close to-40 kJ·mol^(-1),suggesting that the adsorption followed the Langmuir isotherm,indicating a combination of physical and chemical adsorption.SEM/EDX analysis confirmed the formation of a protective layer,while quantum chemical studies further validated strong adsorption,evidenced by a lowΔE of 2.396 eV and an adsorption energy of-878 kcal·mol^(-1)(1kcal·mol^(-1)=4.18 kJ·mol^(-1)).These results demonstrate that Datura stramonium extracts are promising inhibitors,particularly in sulfuric acid,for industrial applications.Reason:Improved clarity,vocabulary,and technical accuracy while maintaining the original meaning.
基金financially supported by the National Natural Science Foundation of China(Nos.21873109 and 21922308)。
文摘Nucleation,which is the initial step of crystallization,critically governs the polymer crystallization behavior,influencing the crystallization temperature,kinetics,and morphology.However,the direct observation of the nucleation process in polymers remains elusive owing to spatial and temporal resolution limitations.This feature article summarizes the recent progress in understanding polymer nucleation within confined and interface-dominated environments,focusing on three representative systems:anodic aluminum oxide templates and nanocomposites containing nanoparticles or nanosheets.The interplay between finite size and interfacial effects has revealed some novel phenomena,such as homogeneous nucleation,surface nucleation,prefreezing,and supernucleation.
基金The National Key R&D Program of China(No.2017YFC0805100)the National Natural Science Foundation of China(No.51578137)+1 种基金the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Open Research Fund Program of Jiangsu Key Laboratory of Engineering Mechanics。
文摘To study the distribution law and random characteristics of casting defects in steel castings,24 civil engineering structural cast steel joints were divided into two groups:simple cast steel joints and complex cast steel joints.Three kinds of nondestructive testing(NDT)methods,namely,visual,magnetic particle,and ultrasonic inspections,were used to detect the macroscopic defects in joints.The NDT results were then statistically analyzed.The results show that the unfused core support is a common defect of complex cast steel joints,and the defect can be seen visually,so excavation and repair welding should be carried out before castings leave factories.Casting cracks are extremely likely to occur in the intersection area of tubes,which is called the ultrasonic inspection blind zone.The occurrence probability of gas pores on simple cast steel joints is the largest,and the occurrence probability of core support incomplete fusions on complex cast steel joints is the largest.However,when cast steel joints are counted as a whole sample,the occurrence probability of gas pores is larger than that of core support incomplete fusions.Therefore,it is the most common defect in cast steel joints.
基金supported by the National Natural Science Foundation of China (Nos. 20734002, 51103163,51003106 and 51003105)Chinese Academy of Sciences (Directional key project on high performance polypropylene alloy resin development)
文摘In this paper, we review our recent progress in the synthesis and application of styryl-capped polypropylene （PP-t- St）, an excellent reactive polyolefin that is both convenient and efficient in synthesis and facile and versatile in application for preparing advanced polypropylene materials via macromolecular engineering. The synthesis of PP-t-St is made possible by a unique chain transfer reaction coordinated by a bis-styrenic molecule, such as 1,4-divinylbenzene （DVB） and 1,2-bis（4- vinylphenyl）ethane （BVPE）, and hydrogen in typical C2-symmetric metallocene （e.g. rac-Me2Si（2-Me-4-Ph-Ind）2ZrC12, in association with methylaluminocene, MAO） catalyzed propylene polymerization. The regio-selective 2,1- insertion of the styrenic double bond in DVB or BVPE into the overwhelmingly 1,2-fashioned Zr-PP propagating chain enables substantial dormancy of the catalyst active site, which triggers selective hydrogen chain transfer that, with the formed Zr-H species ultimately saturated by the insertion of propylene monomer, results in an exclusive capping of the afforded PP chains by styryl group at the termination end. With a highly reactive styryl group at chain end, PP-t-St has been used as a facile building block in PP macromolecular engineering together with the employment of state-of-the-art synthetic polymer chemistry to fabricate broad types of new polypropylene architectures.
基金financially supported by the National Natural Science Foundation of China(Nos.51003109,51025314 and 50573085)
文摘In this study, porous polylactide（PLA） microspheres with different structures were prepared through the multiple emulsion solvent evaporation method. By changing organic solvents（ethyl acetate and chloroform） and adding effervescent salt NH4 HCO3 in the inner water phase, microspheres with porous capsular, matrix, microcapsular and multivesicular structures were prepared. The protein encapsulation and release, and the cell growth behavior of porous microspheres were further explored. Under the same inner water phase, microspheres prepared with chloroform had higher protein encapsulation efficiency and less protein release rate as compared with those prepared with ethyl acetate. Cell experiments showed that the relatively rough surface of microspheres prepared with chloroform was more favorable for the cell growth in comparison with the smooth surface of microspheres prepared with ethyl acetate. This study shows a simple and effective method to control the protein release and cell growth behaviors of polymer microspheres by tuning their porous structure.
基金The National Key Research and Development Program of China(No.2023YFC3805005)Shanghai Municipal Science and Technology Commission Research Program(No.22DZ1201404).
文摘A buckling-restrained steel plate shear wall(BRSPSW)structure with butterfly-shaped links on the lateral sides is introduced to improve the cooperative perfor-mance between the BRSPSW and the boundary frames.A one-span two-story concrete-filled steel tube(CFT)column frame specimen equipped with lateral-side butterfly-shaped linked BRSPSWs(LBL-BRSPSWs)is evaluated under low-cycle reversed loading.A finite element(FE)model is developed and validated based on the test results.This FE model accurately simulates the failure modes and load-dis-placement curves.Parametric analyses are conducted on the butterfly-shaped links.The results show that the interactions between the CFT column frame and LBL-BRSPSWs are sig-nificantly influenced by the width ratio of the butterfly-shaped links,while the taper ratio and aspect ratio have relatively minor influences.Compared with traditional steel shear walls with four-sided connections,LBL-BRSPSWs reduce the additional axial forces and bending moments in the frame columns by 28%to 73%and 17%to 87%,respectively,with only a 9%to 30%decrease in the lateral resistance.The experimental and parametric analysis results indicate that setting butterfly-shaped links on the lateral sides of BRSPSWs can significantly enhance their cooperative performance with the boundary frame.The butterfly-shaped link width ratio has a linear relationship with the lateral-resistance performance of the specimens and the additional internal forces in the frame columns.To ensure that LBL-BRSPSW fails prior to the column frames,the link width ratio should be optimized.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金supported by the University Sultan Moulay Slimane,Beni Mellal,Morocco。
文摘In this paper,we have calculated the structural,electronic,and optical properties of chalcogenide stannite Cu_(2)CdSnX4(X=S,Se,Te) materials.The calculations are based on the density functional theory (DFT) method and are performed using the Cambridge sequential total energy package (CASTEP) code included in the Biovia Material Studio 20 software.All optical properties have been studied in a domain that extends energetically from 10 meV to 40 eV.Our results show that Cu_(2)CdSnX4(X=S,Se,Te) stannite exhibits absorption in the visible region,the refractive index decreases with increasing energy,and the refractive index values are n=3.2,3.73 and 3.75 for Cu_(2)CdSnS_(4),Cu_(2)CdSnSe_(4)and Cu_(2)CdSnTe_(4),respectively.They show also high conductivity,which implies that this material is promising for solar cells.These results argue in favor of the use of these materials in various potential applications.The density of state,band structures,and structural properties of Cu_(2)CdSnX4(X=S,Se,and Te) stannite are also studied in this work.
文摘The rapid growth of the global population,coupled with increasing pollution levels,highlights the urgent need for sustainable and eco-friendly construction materials,such as unfired clay bricks.However,their widespread adoption remains limited due to certain performance drawbacks,particularly in thermal insulation,a critical factor in addressing climate change challenges.In this study,a plant-based waste-derived biopolymer was incorporated into unfired clay bricks to enhance their physicochemical and thermomechanical properties.The biopolymer was added at six different weight fractions(0%,1%,3%,7%,15%,and 20%)to systematically evaluate its impact on bulk density,porosity,capillary water absorption,thermal conductivity,specific heat capacity,and compressive strength.The results revealed a gradual decrease in porosity as the biopolymer content increased,leading to a 41%improvement in thermal conductivity at 20 wt%.However,the optimal balance between thermal efficiency and compressive strength was achieved at 7 wt%biopolymer;this result has been verified through a combination of experimental methods and modeling.Additionally,TRNSYS simulations confirmed the enhanced thermal performance,demonstrating a 9.74%increase in time lag and a 16%reduction in decrement factor,both of which contribute to optimizing building energy efficiency.Overall,this approach not only helps reduce environmental pollution but also enhances insulation capacity while lowering heating and cooling demands,thereby improving overall building performance.Biopolymer-reinforced unfired clay bricks thus represent a promising solution for advancing a low-carbon and sustainable construction industry,aligning with the United Nations Sustainable Development Goals(SDGs)for climate change mitigation and responsible resource management.
基金sponsored by the National Key Research and Development Program of China(2021YFB3802000 and 2021YFB3802004)the National Natural Science Foundation of China(52172016).
文摘The production of cement and concrete using carbonated steel slag as a supplementary cementitious material achieves the dual benefits of efficient steel slag utilization and CO_(2)fixation.In this study,a combination of microbial technology and a rotary kiln process was employed to expedite the carbonation of steel slag for fixation from cement kiln flue gas.This approach resulted in a significant increase in the CO_(2)-fixation rate,with a CO_(2)-fixation ratio of approximately 10%achieved within 1 h and consistent performance across different seasons throughout the year.Investigation revealed that both the CO_(2)-fixation ratio and the particle fineness are pivotal for increasing the soundness and reactivity of steel slag.When the CO_(2)-fixation ratio exceeds 8%and the specific surface area is at least 300 m2∙kg−1,the soundness issue of steel slag can be effectively addressed,facilitating the safe utilization of steel slag.Residual microbes present in the carbonated steel slag powder act as nucleating sites,increasing the hydration rate of the silicate phases in Portland cement to form more hydration products.Microbial regulation results in the biogenic calcium carbonate having smaller crystal sizes,which facilitates the formation of monocarboaluminate to increase the strength of hardened cement paste.At the same CO_(2)-fixation ratio,microbial mineralized steel slag powder exhibits greater hydration activity than carbonated steel slag powder.With a CO_(2)-fixation ratio of 10%and a specific surface area of 600 m^(2)∙kg^(−1),replacing 30%of cement clinker with microbial mineralized steel slag powder yields an activity index of 87.7%.This study provides a sustainable solution for reducing carbon emissions and safely and efficiently utilizing steel slag in the construction materials sector,while expanding the application scope of microbial technology.
基金National Natural Science Foundation of China,Grant/Award Numbers:52002052,52073252,52372235Science and Technology Department of Zhejiang Province,Grant/Award Number:2023C01231+2 种基金Key Research and Development Project of Science and Technology Department of Sichuan Province,Grant/Award Number:2022YFSY0004the Open Project Program of the State Key Laboratory of New textile Materials and Advanced Processing Technologies,Grant/Award Number:FZ2021009Key Laboratory of Engineering Dielectrics and Its Application(Harbin University of Science and Technology),the Ministry of Education,Grant/Award Numbers:KFM202202,KFM202302,KFM202303。
文摘Plasma,the fourth state of matter,is characterized by the presence of charged particles,including ions and electrons.It has been shown to induce unique physical and chemical reactions.Recently,there have been increased applications of plasma technology in the field of multiscale functional materials'preparation,with a number of interesting results.This review will begin by introducing the basic knowledge of plasma,including the definition,typical parameters,and classification of plasma setups.Following this,we will provide a comprehensive review and summary of the applications(phase conversion,doping,deposition,etching,exfoliation,and surface treatment)of plasma in common energy conversion and storage systems,such as electrocatalytic conversion of small molecules,batteries,fuel cells,and supercapacitors.This article summarizes the structure-performance relationships of electrochemical energy conversion and storage materials(ECSMs)that have been prepared or modified by plasma.It also provides an overview of the challenges and perspectives of plasma technology,which could lead to a new approach for designing and modifying electrode materials in ECSMs.
基金supported by the Key Research and Development Special Tasks of Xinjiang,China (No.2022B01051-2)the National Natural Science Foundation of China (Nos.U23B2091,42372328,and 52478253)+1 种基金the Natural Science Foundation of Jiangsu Province,China (No.BK20240209)the Science and Technology Program Special Fund of Jiangsu Province (Frontier Leading Technology Basic Research) Major projects,China (No.BK 20222004)
文摘Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rates,and adequate strength remains a significant challenge for cemented rockfill.This study used a composite alkali activator to activate gangue cemented rockfill.The compressive strength,scanning electron microscopy,energy dispersive spectrometer,mercury intrusion porosimetry,X-ray diffraction,and thermogra-vimetric tests were carried out to investigate the effect of the composite alkali activator proportion on the compressive strength,micro-structure,and composition of the cemented rockfill.The calcium silicate hydrate(C–S–H)molecular model of cemented rockfill was con-structed to explore the fracture evolution of the nucleated molecular structure under tension.The results show that compressive strength initially increased and then decreased with the activator proportion,the optimal activator proportion of 1:2 resulted in a 31.25%increase in strength at 3 d.This reasonable activator proportion strengthens the pozzolanic effect of gangue,and consumes more calcium hydroxide to inhibit its agglomeration,ultimately achieving the densification of microstructure.The activator proportion inevitably substitutes calcium ions with sodium ions in the C–S–H molecular model.The 12%substitution of calcium ions increases the adhesion between silicon chain layers,which is beneficial to the interlayer stress transfer.This work proposes a method for preparing low-cost cemented rockfill from al-kali-activated gangue,which can be used for solid waste recycling and reducing cement consumption to achieve low-carbon goals.
文摘In November 2024,the Global Solar Council announced that the world cumulative solar capacity reached 2 terawatts,twice as much as in mid-2022,clearly showing that solar energy is set to lead the energy transition.
基金financially supported by the National Natural Science Foundation of China (Nos. 52173013 and 52373015)。
文摘Polybutene-1(PB-1) is a semi-crystalline polymer with excellent mechanical properties. However, its practical application is significantly hindered by the slow Form Ⅱ-Ⅰ transition, which can take up to several days to complete. While prior research established that long-chain branching(LCB) structures synthesized via ω-alkenylmethyldichlorosilane copolymerization-hydrolysis(ACH) chemistry markedly accelerate this transition, this work demonstrates that H-shaped LCB structures constructed through copolymerization with 1,9-decadiene exhibit the capability to facilitate Form Ⅱ-Ⅰ transition in most systems evaluated herein. However, low branching efficiency concurrently generates extended alkyl pendant chains, which impose pronounced steric-hindrance-driven suppression on the transition kinetics, thereby substantially diminishing the net acceleration effect of the LCB structures, even resulting in a net retardation effect in certain systems. Notably, a significant synergistic acceleration effect emerged between the H-shaped LCB structures and propylene comonomer units. These findings confirm that the H-shaped LCB structures play a role in promoting the Form II-I transformation process, which is independent of the synthetic pathways, thereby providing more strategies for addressing the long-standing processing problems of PB-1.
文摘In this article,we have modeled the astroclimatic parameters using data from the fifth reanalysis series(ERA5)from the European Centre for Medium-Range Weather Forecasts over the period 2010-2020.These data have been projected onto the site of the Roque de los Muchachos Observatory(ORM).The analysis covers the main parameters influencing the quality of astronomical observation,notably the vertical profiles of temperature,potential temperature,and optical turbulence(C_(n)~2),as well as the vertical wind distributions and seasonal behaviors of atmospheric turbulence,which are treated in detail by specifying the wind speed at the 200 hPa level(V200).Around this level,the wind at high altitude presents moderate speeds and a generally stable direction,conditions favorable for adaptive optics.The thermal profiles show good agreement with standard atmospheric models,with a well-defined tropopause and a stable stratosphere,as well as the integrated parameters such as seeing(free and total),isoplanatic angle,and coherence time.The results reveal a stratified and stable atmosphere,with turbulence predominantly concentrated in the lower troposphere.The thermal profiles show a good agreement with standard atmospheric models,with a well-defined tropopause and a stable stratosphere.The seasonality of the astroclimatic parameters indicates conditions particularly favorable for observation during the winter months,with the median of free seeing,total seeing,isoplanatic angle and a coherence time as respectively 0″.48,0″.72,2″,and 6 ms.These results confirm the strong potential of ORM as a reference astronomical site,capable of hosting high-precision observation instruments.The methodological approach employed also provides a replicable basis for the characterization of other candidate sites for the installation of ground-based telescopes.As a preliminary study,this work establishes a scientific basis for further on-site monitoring and detailed characterization of the ORM site.
文摘The primary objective of this study is to develop an innovative theoretical model to accurately predict the thermophysicalproperties of hybrid nanofluids designed to enhance cooling in solar panel applications.This researchlays the groundwork for our future studies,which will focus on photovoltaic thermal applications.These nanofluidsconsist of water and nanoparticles of alumina(Al_(2)O_(3)),titanium dioxide(TiO_(2)),and copper(Cu),exploringvolumetric concentrations ranging from 0%to 4%for each type of nanoparticle,and up to 10%for total mixtures.The developed model accounts for complex interactions between the nanoparticles and the base fluid,as well assynergistic effects resulting from the coexistence of different nanoparticles.Detailed simulations have shownexceptional agreement with experimental results,reinforcing the credibility of our approach in accurately capturingthe thermophysical behavior of these hybrid nanofluids.Based on these results,our study proposes significantadvancements in the design and optimization of nanofluids for cooling applications in solar panels.These developmentsare crucial for improving the efficiency of solar installations by mitigating overheating effects,providinga solid foundation for practical applications in this rapidly evolving field.
文摘Aiming at the gas discharge problem in electric aircraft,this work studies the gas discharge characteristics at low-temperature sub-atmospheric pressure.A gas discharge shooting platform was built,and the discharge process was photographed by intensified charge-coupled device(ICCD).A two-dimensional axisymmetric model of needle-plate electrode gas discharge was established,and three sets of Helmholtz equations were used to solve the photoionization.The results show that under the same voltage,the electric field intensity in the discharge process increases first,then decreases and finally increases again.The discharge speed increases with the increase of altitude,and the electron density in the streamer decreases with the increase of altitude.The development speed of the streamer in the middle stage is higher than that in the early stage,and the speed increases more obviously with the increase of altitude.The development speed of the streamer in the later stage is lower than that in the middle stage,but with the increase of altitude,the development speed of the streamer in the later stage is higher than that in the middle stage.
文摘Chiral N-substituted amino amides and esters are ubiquitous scaffolds in pesticides and pharmaceutical chemicals,but their asymmetric synthesis remains challenging especially for those with multiple chiral centers.In this study,IR104 from Streptomyces aureocirculatus was identified from 157 wild-type imine reductases for the synthesis of(S)-2-((R)-2-oxo-4-propylpyrrolidin-1-yl)butanamide(antiepileptic drug Brivaracetam)via dynamic kinetic resolution reductive amination from ethyl 3-formylhexanoate and(S)-2-aminobutylamide with high diastereoselectivity.To further improve the catalytic efficiency of IR104,its mutant D191E/L195I/E253S/M258A(M3)was identified by saturation mutagenesis and iterative combinatorial mutagenesis,which exhibited a 102-fold increase in the catalytic efficiency relative to that of wild-type enzyme and high diastereoselectivity(98:2 d.r.).Crystal structural analysis and molecular dynamics simulations provided some insights into the molecular basis for the improved activity of the mutant enzyme.The imine reductase identified in this study could accept chiral amino amides/esters as amino donors for the dynamic kinetic resolution reductive amination of racemicα-substituted aldehydo-esters,expanding the substrate scope of imine reductases in the dynamic kinetic resolution-reductive amination.Finally,IR104-M3 was successfully used for the preparation of Brivaracetam at gram scale.Using this mutant,various N-substituted amino amides/esters with two chiral centers were also synthesized with up to 99:1 d.r.and 96%yields and subsequently converted intoγ-andδ-lactams,providing an efficient protocol for the synthesis of these important compounds via enzymatic dynamic kinetic resolution-reductive amination from simple building blocks.
基金The SEU Innovation Capability Enhancement Plan for Doctoral Students(No.CXJH_SEU 24115)Marine Economic Development Project of Guangdong Province(No.GDNRC[2022]25).
文摘The study aimed to address the issue of elevated residual stress levels in dissimilar girth welds of cast steel joints.To achieve this,the hybrid welding technology,which yields high welding speeds while simultaneously reducing residual stresses,has been introduced.This study utilizes a numerical simulation method to investigate the temperature and residual stress field in the hybrid welding of G20Mn5 casting-Q355 low-alloy steel welded pipe.A com-parison of the findings of this study with those of other welding processes revealed the technological advantages of hybrid welding.The research outcomes show that due to geometric discontinuities and material differences,the temperature field of the joint exhibits uneven distribution characteristics,and the peak temperatures on the Q355 steel side exceeds those on the G20Mn5 steel side.An evident stress gra-dient is present in the residual stress field of the joint post-welding,with peak stress located at the weld root on the Q355 steel.Compared with arc welding,the hybrid welding leads to decreased residual stresses and deformation,with high stress outside the heat-affected zone diminishing rapidly.Furthermore,it significantly improves the welding efficiency.This study elucidates the distribution and underlying causes of thermal and residual stress fields in dissimilar girth welds.This serves as a foundation for the application of hybrid welding technology in welded cast steel joints.
