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Optimal slag content for geopolymer composites under freeze-thaw cycles with different freezing temperatures

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第4期24卷 366-376页

作者： Lifeng FAN Weiliang ZHONG Guang WANG Yan Xi Faculty of Architecture Civil and Transportation EngineeringBeijing University of TechnologyBeijing 100124China

Improving the freeze-thaw resistance of geopolymers is of great significance to ensure their durability in cold regions. This study presents an experimental investigation of optimal slag content for geopolymer composites under freeze-thaw cycles with different freezing temperatures. Firstly, five kinds of geopolymer composites with 10.0%, 20.0%, 30.0%, 40.0%,and 50.0% slag contents and 1.0% fiber content were prepared. Freeze-thaw cycle tests at-1.0 ℃,-20.0 ℃, and-40.0 ℃ were carried out for these geopolymer composites and their physical and mechanical properties after the freeze-thaw cycle were tested. The results show that the porosity of the geopolymer composites decreases as the slag content increases. Their mass loss ratio and strength loss ratio increase gradually as the freezing temperature decreases. The mass loss ratio and strength loss ratio of geopolymer composites after freeze-thaw cycles all decrease as the slag content increases. Considering the physical and mechanical properties of geopolymers after freeze-thaw cycles, the optimal slag contents are 40.0% and 50.0%.

关键词： Geopolymer composites Freeze-thaw cycle Freezing temperature Slag content

Investigation of three different cooling treatments on dynamic mechanical properties and fragmentation characteristics of granite subjected to thermal cycling

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Underground Space 2022年第5期7卷 847-861页

作者： Lifeng Fan Han Li Yan Xi Beijing University of Technology Beijing 100124China

Underground thermal engineering such as geothermal exploitation usually involves the response of impact loads due to the drilling operation and blasting load.This study investigated the dynamic mechanical properties and fragmentation characteristics of granite subjected to thermal cycling under natural cooling,water cooling,and liquid nitrogen cooling.Firstly,split Hopkinson pressure bar tests were performed on granite under three different cooling methods to study the dynamic mechanical parameters with thermal cycles.Subsequently,the damage factors were calculated to evaluate the damage on granite and the relationship between damage and stress.Finally,the granite fragments after impact were sieved,and the fractal dimension and average fragment size were introduced to analyze the fragmentation characteristics.The results demonstrate that the degradation of dynamic mechanical properties mainly occurs in the first four thermal cycles;with the increase of damage factor,the stress decreases linearly under the three cooling methods,and the damage caused by liquid nitrogen cooling to granite is the most significant,followed by water cooling.Fragments of granite change from axial splitting failure to a more complex composite failure mode.In addition,with the decrease of the average fragment size,the fractal dimension of the granite gradually increases,resulting in the higher fragmentation degree and the better uniformity of fragmentation.

关键词： Split Hopkinson pressure bar Dynamic mechanical properties Fragmentation characteristics Cooling treatment

Spatially distributed damage in sandstone under stress-freeze-thaw coupling conditions

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第6期14卷 1910-1922页

作者： Lifeng Fan Yiding Fan Yan Xi Jingwei Gao College of Architecture and Civil Engineering Beijing University of TechnologyBeijing100124China

In the present study,we tried to understand the spatially distributed damage in sandstone samples under the coupled stress-freeze-thaw(SFT)conditions.Firstly,uniaxial compressive stresses(i.e.0 MPa,10 MPa,20 MPa,and 25 MPa)were applied to the samples,and then freeze-thaw(FT)cycles(0,8,16,and 24)were performed on the uniaxially stressed samples to realize the SFT coupling.Next,real-time CT scanning was conducted to observe the induced damage.The total porosity was introduced to quantitatively evaluate the damage degree.The local porosity variation,with the distance from the center of the sandstone sample,was analyzed to understand the spatial distribution of damage.Finally,the coupling effects of SFT on the damage gradient were discussed.The results indicate that the porosity rises with FT cycles,and the applied stresses can accelerate the increase in porosity.The damage increases exponentially with the distance from the center of the sample.The damage presents a spatial gradient distribution,not the commonly used uniform distribution in various studies.The damage gradient increases with FT cycles,and the increasing rate in damage gradient decreases at uniaxial stress of 0 MPa and 10 MPa first,but the increasing rate in damage gradient increases with FT cycles then at stress increasing to 20 MPa.

关键词： Rock damage Freeze-thaw(FT)cycles Uniaxial stress oupling effects

DI-3-n-butylphthalide exerts neuroprotective effects by modulating hypoxia-inducible factor 1-alpha ubiquitination to attenuate oxidative stress-induced apoptosis

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Neural Regeneration Research 2023年第11期18卷 2424-2428页

作者： Shuai Li Jingyuan Zhao Yan Xi Jiaqi Ren yanna Zhu yan Lu Deshi Dong Department of Pharmacy The First Affiliated Hospital of Dalian Medical UniversityDalianLiaoning ProvinceChina Regenerative Medicine Center The First Affiliated Hospital of Dalian Medical UniversityDalianLiaoning ProvinceChina Department of Cardiology Institute of Cardiovascular DiseasesThe First Affiliated Hospital of Dalian Medical UniversityDalianLiaoning ProvinceChina

DI-3-n-butylphthalide is used to treat mild and moderate acute ischemic stroke.However,the precise underlying mechanism requires further investigation.In this study,we investigated the molecular mechanism of DI-3-n-butylphthalide action by various means.We used hydrogen peroxide to induce injury to PC12cells and RAW264.7 cells to mimic neuronal oxidative stress injury in stroke in vitro and examined the effects of DI-3-n-butylphthalide.We found that DI-3-nbutylphthalide pretreatment markedly inhibited the reduction in viability and reactive oxygen species production in PC12 cells caused by hydrogen peroxide and inhibited cell apoptosis.Furthermore,DI-3-n-butylphthalide pretreatment inhibited the expression of the pro-apoptotic genes Bax and Bnip3.DI-3-nbutylphthalide also promoted ubiquitination and degradation of hypoxia inducible factor 1α,the key transcription factor that regulates Bax and Bnip3 genes.These findings suggest that DI-3-n-butylphthalide exhibits a neuroprotective effect on stroke by promoting hypoxia inducible factor-1α ubiquitination and degradation and inhibiting cell apoptosis.

关键词： blood-brain barrier Dl-3-n-butylphthalide hypoxia inducible factor 1α mitochondria neuroprotection oxidative stress reactive oxygen species stroke transcription factor ubiquitination

Singular Value Inequalities of Matrix Sum in Log-ma jorizations

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Acta Mathematica Sinica,English Series 2023年第2期39卷 375-386页

作者： Bo Yan Xi Fu Zhen ZHANG College of Mathematics Inner Mongolia Minzu UniversityTongliao028043China Department of Mathematics Nova Southeastern University3301 College Ave.Fort LauderdaleFL33314USA

We show some upper bounds for the product of arbitrarily selected singular values of the sum of two matrices.The results are additional to our previous work on the lower bound eigenvalue inequalities of the sum of two positive semidefinite matrices.Besides,we state explicitly Hoffman’s minimax theorem with a proof,and as applications of our main results,we revisit and give estimates for related determinant inequalities of Hua type.

关键词： Eigenvalue Hoffman minimax theorem Hua determinant inequality log-majorization majorization Minkowski determinant inequality singular value Wielandt minimax theorem

Zr-doped titanium lithium ion sieve and EP-granulated composite:Superb adsorption and recycling performance

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Particuology 2022年第10期20卷 100-110页

作者： Suyu Zhou xiaojing Guo xi yan yan Chen Wanzhong Lang The Education Ministry Key Laboratory of Resource Chemistry Shanghai Key Laboratory of Rare Earth Functional MaterialsDepartment of Chemistry and Chemical EngineeringShanghai Normal UniversityShanghai 200234China

Lithium ion sieve(LIS)has attracted great attention due to its high adsorption selectivity towards Li+.Herein,a new type of Zr-doped Ti-LIS(HZrTO)was synthesized by a simple calcination method.The adsorption capacity increased from 56.3 mgg-1(before doping)to 93.2 mgg-1 after doping in LiOH solution(lithium 1.8gL-1).The adsorption isotherm and adsorption kinetics of HZrTO accord with the Langmuir isotherm and the pseudo-second-order kinetic equation,respectively.Batch experiments showed that HZrTO has good stability and selectivity.In addition,HZrTO was granulated via epoxy resin(E-12),and the obtained granular adsorbent showed good adsorption capacity,excellent stability and high selectivity towards Li+.

关键词： Lithium ion sieve Lithium titanium oxide Zr-doped Granulation

The NAC transcription factor ONAC083 negatively regulates rice immunity against Magnaporthe oryzae by directly activating transcription of the RING-H2 gene OsRFPH2-6

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Journal of Integrative Plant Biology 2023年第3期65卷 854-875页

作者： yan Bi Hui Wang xi Yuan Yuqing yan Dayong Li Fengming Song National Key Laboratory for Rice Biology Institute of BiotechnologyZhejiang UniversityHangzhou 310058China College of Chemistry and Life Sciences Zhejiang Normal UniversityJinhua 321004China

NAC transcription factors(TFs) play critical roles in plant immunity by modulating the expression of downstream genes via binding to specific cis-elements in promoters. Here, we report the function and regulatory network of a pathogenand defense phytohormone-inducible NAC TF gene, ONAC083, in rice(Oryza sativa) immunity.ONAC083 localizes to the nucleus and exhibits transcriptional activation activity that depends on its C-terminal region. Knockout of ONAC083enhances rice immunity against Magnaporthe oryzae, strengthening pathogen-induced defense responses, and boosting chitin-induced pattern-triggered immunity(PTI), whereas ONAC083 overexpression has opposite effects. We identified ONAC083-binding sites in the promoters of 82genes, and showed that ONAC083 specifically binds to a conserved element with the core sequence ACGCAA. ONAC083 activated the transcription of the genes OsRFPH2-6, OsTrx1, and OsPUP4 by directly binding to the ACGCAA element. OsRFPH2-6, encoding a RING-H2 protein with an N-terminal transmembrane region and a C-terminal typical RING domain, negatively regulated rice immunity against M. oryzae and chitin-triggered PTI. These data demonstrate that ONAC083 negatively contributes to rice immunity against M. oryzae by directly activating the transcription of OsRFPH2-6 through the ACGCAA element in its promoter. Overall, our study provides new insight into the molecular regulatory network of NAC TFs in rice immunity.

关键词： ACGCAA element immunity Magnaporthe oryzae ONAC083 OsRFPH2-6 rice

Rich defects and nanograins boosted formaldehyde sensing performance of mesoporous polycrystalline ZnO nanosheets

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Rare Metals 2022年第7期41卷 2292-2304页

作者： Le-xi Zhang Ming-Mei Zhao yan-yan Yin Yue xing Li-Jian Bie School of Materials Science and Engineering Tianjin Key Laboratory for Photoelectric Materials and DevicesKey Laboratory of Display Materials and Photoelectric Devices(Ministry of Education)National Demonstration Center for Experimental Function Materials EducationTianjin University of TechnologyTianjin 300384China Department of Environmental Science and Engineering Nankai University Binhai CollegeTianjin 300270China

Comprehensive consideration of structural and electronic sensitization is of significant importance for rational design and assembly of high-performance gas sensors based on metal oxides.In this work,hierarchically mesoporous ZnO nanosheets are synthesized via a hydrothermal method followed by calcination.Material characterization reveals polycrystalline feature of these ZnO nanosheets rich in mesopores and defects.Gas sensing performance of as-synthesized ZnO nanosheets was sys-tematically investigated,taking formaldehyde as probe molecules.Compared with commercial ZnO nanoparticles,ZnO nanosheets exhibited enhanced formaldehyde sensing properties,including lower operation temperature,higher sensitivity,faster response,and smaller detection limit.Notably,the response(S=227.4)of ZnO nanosheets to 200×10^(-6) formaldehyde is about 17 times larger than that of ZnO nanoparticles(S=13.5).Excluding effects of grain size and surface area,enhanced sensing properties,especially response value,are credited in large part to synergistic actions of surface defects,grain boundaries,as well as unique structural advantage of ZnO nanosheets.Furthermore,this work offers a guideline for boosting performance of metal oxide-based gas sensors via surface defect control and grain boundary construction.

关键词： performance polycrystalline grain

Ultrafine Ru nanoparticles anchored on core-shell structured zeolite-carbon for efficient catalysis of hydrogen generation

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Rare Metals 2023年第7期42卷 2324-2334页

作者： Yue-Wei Wei Guang yang xi-xi Xu yan-yan Liu Nai-xin Kang Bao-Jun Li Yong-Zhao Wang Yong-xiang Zhao School of Chemistry and Chemical Engineering Shanxi UniversityTaiyuan030006China Engineering Research Center of Ministry of Education for Fine Chemicals Shanxi UniversityTaiyuan030006China Tobacco College of Henan Agricultural University Zhengzhou450002China College of Science Henan Agricultural UniversityZhengzhou450002China ISM UMR CNRS Nº5255Univ.BordeauxTalence Cedex33405France Research Center of Green Catalysis College of ChemistryZhengzhou UniversityZhengzhou450001China

As a promising route to hydrogen production,hydrolysis of ammonia borane(AB)aqueous solution requires efficient and stable catalysts.In this paper,a carbon-coated zeolite is prepared by high temperature calcination using glucose as carbon source.Ultrafine Ru nanoparticles are anchored on the composite support with core-shell structure using a simple in situ reduction method.The prepared catalyst expressed outstanding catalytic activity in the hydrolytic dehydrogenation of AB.The effects of support prepared by different synthesis parameters on the performance of catalyst are investigated.The Ru/S-1@C(RSC-2)catalyst exhibited the highest catalytic activity for hydrolytic dehydrogenation of AB with a turnover frequency of 892 min^(-1)at room temperature.This performance is superior to that of many catalysts previously reported.The excellent catalytic activity is attributed to the carbon layer on catalyst surface effectively limiting the aggregation of Ru nanoparticles in the hydrolysis reaction.The zeolite also plays a role in preactivation of water.This pre-activation accelerates the ratelimiting step of water dissociation in the reaction.The kinetic studies for determining the activation energy(E_(a)=36.8 kJ·mol^(-1))were based on reaction temperature.The effects of catalyst concentration,AB concentration and NaOH concentration on hydrolysis rate of AB were further investigated.The high-performance catalysts and the preparation method in this study have wide application prospects in the field of clean energy.

关键词： Ammonia borane Ruthenium Hydrogen generation Carbon Zeolite