乙炔选择加氢反应中碳化钯的动态精细调控: 气氛和氧化锌助剂的作用

碳化钯通常被认为是乙炔选择加氢反应中原位生成的活性相,其生成有助于抑制次表面非选择性的氢化钯物种,从而实现高选择性乙炔加氢制乙烯的目标.次表面上碳化钯和氢化钯物种之间的竞争很大程度上决定了乙炔加氢反应的选择性.然而,由于实际反应环境的复杂性,反应环境下的两种物种之间的动态转化过程和竞争关系尚不清晰.特别是,反应环境(比如氢气组分)对碳化钯物种的调控机制仍不明确,也使得对碳化钯活性物种的精准调控变得困难.此外,氧化锌助剂作为乙炔选择加氢反应中最常用的助剂之一,存在典型的金属-氧化物界面相互作用,也会对渗碳过程产生重要影响.因此,从动态视角理解碳化钯物种的原位形成过程,对于精准设计和合成高性能乙炔选择加氢钯基催化剂具有重要的科学意义.近年来,先进原位表征光谱技术的不断发展使得从原子、分子层面理解原位过程机制成为可能.本文旨在通过先进的原位表征技术揭示乙炔选择加氢反应中碳化钯物种的动态生成过程,并进一步探究气氛环境、温度、助催化剂等参数对碳化钯物种的动态调控机制,从而为高性能乙炔选择加氢催化剂的精准设计和合成提供有力支撑.原位研究结果表明,在氢气升温还原条件下,空气焙烧后新鲜催化剂中氧化钯相首先转变为氢化钯相;随着还原温度升高,氢化钯相的含氢量逐渐降低.当切换至乙炔选择加氢反应原料气时,氢化钯相迅速分解为金属钯,并随着恒温碳化时间的延长,烃类裂解产生的碳原子逐渐渗入钯的体相,最终形成稳定的碳化钯活性相.通过移除乙炔加氢反应原料气氛中的氢气,考察了反应气中的氢气组分对碳化钯形成的调控机制.实验发现,在仅有乙炔和乙烯存在时,碳化过程仍能发生;而引入少量氢气(体积分数2.2%)后,碳化程度显著增强,C/Pd原子比从0.136提升至0.154.相变机理研究表明,氢气的引入促进了氢化钯物种的形成,并通过晶格扩张作用促进渗碳过程.此外,还研究了氧化锌助剂对原位渗碳过程的影响,揭示了氧化锌助剂对碳化钯的抑制作用.结合原位CO吸附漫反射红外光谱、准原位X射线光电子能谱分析发现,低温氢气还原下Pd-ZnO界面作用促进了微量表面PdZn合金的生成,从而抑制了碳的渗入.这种现象在不含氢气的碳化气氛中尤为显著,碳含量降低一个数量级(C/Pd原子比仅为0.019).在此基础上,通过调节反应条件,实现了对碳化钯物种碳含量的精准调控,并与反应活性关联,揭示了碳化钯含量与乙炔选择加氢反应活性之间的线性关系.电子结构表征和同位素实验进一步表明,Pd-C的电子相互作用促进了向Pd中心原子的电子转移,从而提高了氢气的活化解离能力和乙炔加氢反应活性.综上,本工作原位解析了碳化钯的动态形成过程,阐明了氢气辅助插碳和ZnO抑制插碳的微观机制,实现了碳化钯活性物种的精准调控,揭示了碳化程度与反应活性的线性关系,为高性能乙炔选择加氢催化剂设计提供了参考.

Effect of bubble morphology and behavior on power consumption in non-Newtonian fluids’aeration process

Due to a prolonged operation time and low mass transfer efficiency, the primary challenge in the aeration process of non-Newtonian fluids is the high energy consumption, which is closely related to the form and rate of impeller, ventilation, rheological properties and bubble morphology in the reactor. In this perspective, through optimal computational fluid dynamics models and experiments, the relationship between power consumption, volumetric mass transfer rate(kLa) and initial bubble size(d0) was constructed to establish an efficient operation mode for the aeration process of non-Newtonian fluids. It was found that reducing the d0could significantly increase the oxygen mass transfer rate, resulting in an obvious decrease in the ventilation volume and impeller speed. When d0was regulated within 2-5 mm,an optimal kLa could be achieved, and 21% of power consumption could be saved, compared to the case of bubbles with a diameter of 10 mm.

基于数据治理的区域教育数字化转型研究

随着教育信息化的深入发展,其已逐渐从融合创新阶段向教育数字化转型演化。数据治理在教育数字化转型中发挥着关键作用,通过其技术与管理优势,推动教育领域不断变革。基于韦伯数据治理权变模型及开放系统互连参考模型(OSI),深入探讨区域教育数字化转型的内在机制与路径。研究结果表明,数据治理能有效促进智慧教育治理协同高效化,数字教育资源质优、多元化,高质量教育创新化,以及“三个课堂”常态化。为进一步推进区域教育数字化转型,提出优化顶层设计、稳固中枢数据层建设、强化应用层覆盖、全面开发教育资源的策略建议。如此,不仅能丰富教育数字化转型的理论体系,而且为我国区域教育数字化转型提供实践指导,具有重要的理论意义和实践价值。

A novel algorithm for evaluating cement azimuthal density based on perturbation theory in horizontal well

Cement density monitoring plays a vital role in evaluating the quality of cementing projects,which is of great significance to the development of oil and gas.However,the presence of inhomogeneous cement distribution and casing eccentricity in horizontal wells often complicates the accurate evaluation of cement azimuthal density.In this regard,this paper proposes an algorithm to calculate the cement azimuthal density in horizontal wells using a multi-detector gamma-ray detection system.The spatial dynamic response functions are simulated to obtain the influence of cement density on gamma-ray counts by the perturbation theory,and the contribution of cement density in six sectors to the gamma-ray recorded by different detectors is obtained by integrating the spatial dynamic response functions.Combined with the relationship between gamma-ray counts and cement density,a multi-parameter calculation equation system is established,and the regularized Newton iteration method is employed to invert casing eccentricity and cement azimuthal density.This approach ensures the stability of the inversion process while simultaneously achieving an accuracy of 0.05 g/cm^(3) for the cement azimuthal density.This accuracy level is ten times higher compared to density accuracy calculated using calibration equations.Overall,this algorithm enhances the accuracy of cement azimuthal density evaluation,provides valuable technical support for the monitoring of cement azimuthal density in the oil and gas industry.

Study of tree shrew biology and models: A booming and prosperous field for biomedical research

The tree shrew(Tupaia belangeri)has long been proposed as a suitable alternative to non-human primates(NHPs)in biomedical and laboratory research due to its close evolutionary relationship with primates.In recent years,significant advances have facilitated tree shrew studies,including the determination of the tree shrew genome,genetic manipulation using spermatogonial stem cells,viral vector-mediated gene delivery,and mapping of the tree shrew brain atlas.However,the limited availability of tree shrews globally remains a substantial challenge in the field.Additionally,determining the key questions best answered using tree shrews constitutes another difficulty.Tree shrew models have historically been used to study hepatitis B virus(HBV)and hepatitis C virus(HCV)infection,myopia,and psychosocial stress-induced depression,with more recent studies focusing on developing animal models for infectious and neurodegenerative diseases.Despite these efforts,the impact of tree shrew models has not yet matched that of rodent or NHP models in biomedical research.This review summarizes the prominent advancements in tree shrew research and reflects on the key biological questions addressed using this model.We emphasize that intensive dedication and robust international collaboration are essential for achieving breakthroughs in tree shrew studies.The use of tree shrews as a unique resource is expected to gain considerable attention with the application of advanced techniques and the development of viable animal models,meeting the increasing demands of life science and biomedical research.

Genome wide association analysis identifies candidate genes for fruit quality and yield in Actinidia eriantha

Quality and yield are the primary concerns in kiwifruit breeding,but research on the genetic mechanisms of fruit size,shape,and ascorbic acid(ASA)content is currently very limited,which restricts the development of kiwifruit molecular breeding.In this study,we obtained a total of 8.88 million highly reliable single nucleotide polymorphism(SNP)markers from 140 individuals from the natural hybrid offspring of Actinidia eriantha cv.‘White’using whole genome resequencing technology.A genome-wide association study was conducted on eight key agronomic traits,including single fruit weight,fruit shape,ASA content,and the number of inflorescences per branch.A total of 59 genetic loci containing potential functional genes were located,and candidate genes related to single fruit weight,fruit length,ASA content,number of inflorescences per branch and other traits were identified within the candidate interval,such as AeWUSCHEL,AeCDK1(cell cycle dependent kinase),AeAO1(ascorbic oxidase)and AeCO1(CONSTANS-like 4).After constructing an RNAi vector for AeAO1 and injecting it into the fruit of cv.‘Midao 31’to interfere with the expression of the AeAO1 gene,the results showed that the activity of ascorbic oxidase in the fruit of‘Midao 31’significantly decreased,while the content of ASA significantly increased.This study provides valuable insights into the genetic basis of variation in A.eriantha fruit traits,which may benefit molecular marker-assisted breeding efforts.

Achievable hole concentration at room temperature as a function of Mg concentration for MOCVD-grown p-GaN after sufficient annealing

Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper.Different annealing conditions were applied to obtain sufficient activation for p-GaN samples with different Mg doping ranges.Hole concentration,resistivity and mobility were characterized by room-temperature Hall measurements.The Mg doping concentration and the residual impurities such as H,C,O and Si were measured by secondary ion mass spectroscopy,confirming negligible compensations by the impurities.The hole concentration,resistivity and mobility data are presented as a function of Mg concentration,and are compared with literature data.The appropriate curve relating the Mg doping concentration to the hole concentration is derived using a charge neutrality equation and the ionized-acceptor-density[N-(A)^(-)](cm^(−3))dependent ionization energy of Mg acceptor was determined asE_(A)^(Mg)=184−2.66×10^(−5)×[N_(A)^(-)]1/3 meV.

An Efficient Reliability-Based Optimization Method Utilizing High-Dimensional Model Representation and Weight-Point Estimation Method

The objective of reliability-based design optimization(RBDO)is to minimize the optimization objective while satisfying the corresponding reliability requirements.However,the nested loop characteristic reduces the efficiency of RBDO algorithm,which hinders their application to high-dimensional engineering problems.To address these issues,this paper proposes an efficient decoupled RBDO method combining high dimensional model representation(HDMR)and the weight-point estimation method(WPEM).First,we decouple the RBDO model using HDMR and WPEM.Second,Lagrange interpolation is used to approximate a univariate function.Finally,based on the results of the first two steps,the original nested loop reliability optimization model is completely transformed into a deterministic design optimization model that can be solved by a series of mature constrained optimization methods without any additional calculations.Two numerical examples of a planar 10-bar structure and an aviation hydraulic piping system with 28 design variables are analyzed to illustrate the performance and practicability of the proposed method.

Acidic/hypoxia dual-alleviated nanoregulators for enhanced treatment of tumor chemo-immunotherapy

Chemotherapy plays a crucial role in triple-negative breast cancer (TNBC) treatment as it not only directly kills cancer cells but also induces immunogenic cell death. However, the chemotherapeutic efficacy was strongly restricted by the acidic and hypoxic tumor environment. Herein, we have successfully formulated PLGA-based nanoparticles concurrently loaded with doxorubicin (DOX), hemoglobin (Hb) and CaCO3 by a CaCO3-assisted emulsion method, aiming at the effective treatment of TNBC. We found that the obtained nanomedicine (DHCaNPs) exhibited effective drug encapsulation and pH-responsive drug release behavior. Moreover, DHCaNPs demonstrated robust capabilities in neutralizing protons and oxygen transport. Consequently, DHCaNPs could not only serve as oxygen nanoshuttles to attenuate tumor hypoxia but also neutralize the acidic tumor microenvironment (TME) by depleting lactic acid, thereby effectively overcoming the resistance to chemotherapy. Furthermore, DHCaNPs demonstrated a notable ability to enhance antitumor immune responses by increasing the frequency of tumor-infiltrating effector lymphocytes and reducing the frequency of various immune-suppressive cells, therefore exhibiting a superior efficacy in suppressing tumor growth and metastasis when combined with anti-PD-L1 (αPD-L1) immunotherapy. In summary, this study highlights that DHCaNPs could effectively attenuate the acidic and hypoxic TME, offering a promising strategy to figure out an enhanced chemo-immunotherapy to benefit TNBC patients.

LATS1 Promotes B-ALL Tumorigenesis by Regulating YAP1 Phosphorylation and Subcellular Localization

Objective YAP1 plays a dual role as an oncogene and tumor suppressor gene in several tumors;differentiating between these roles may depend on the YAP1 phosphorylation pattern.The specific function of YAP1 in B cell acute lymphoblastic leukemia(B-ALL),however,is currently unclear.Thus,in the present study,the role of YAP1 in B-ALL was investigated using relevant cell lines and patient datasets.Methods The effects of shRNA-mediated knockdown on YAP1 and LATS1 levels in the NALM6 and MOLT-4 cell lines were examined using Western blotting,quantitative real-time polymerase chain reaction,flow cytometry,immunostaining,and nude mouse subcutaneous tumorigenesis experiments.Gene expression levels of Hippo pathway-related molecules before and after verteporfin(VP)treatment were compared using RNA-Seq to identify significant Hippo pathway-related genes in NALM6 cells.Results Patients with ALL showing high YAP1 expression and low YAP1-Ser127 phosphorylation levels had worse prognoses than those with low YAP1 protein expression and high YAP1-Ser127 phosphorylation levels.YAP1-Ser127 phosphorylation levels were lower in NALM6 cells than in MOLT-4 and control cells;YAP1 was distributed in the nuclei in NALM6 cells.Knockdown of YAP1 inhibited MOLT-4 and NALM6 cell proliferation and arrested the NALM6 cell cycle in the G0/G1 phase.Before and after VP treatment,the expression of the upstream gene LATS1 was upregulated;its overexpression promoted YAP1-Ser127 phosphorylation.Further,YAP1 was distributed in the plasma.Conclusion LATS1 may downregulate YAP1-Ser127 phosphorylation and maintain B-ALL cell function;thus,VP,which targets this axis,may serve as a new therapeutic method for improving the outcomes for B-ALL patients.

A hybrid contact approach for modeling soil-structure interaction using the material point method

The grid-based multi-velocity field technique has become increasingly popular for simulating the Material Point Method(MPM)in contact problems.However,this traditional technique has some shortcomings,such as(1)early contact and contact penetration can occur when the contact conditions are unsuitable,and(2)the method is not available for contact problems involving rigid-nonrigid materials,which can cause numerical instability.This study presents a new hybrid contact approach for the MPM to address these limitations to simulate the soil and structure interactions.The approach combines the advantages of point-point and point-segment contacts to implement contact detection,satisfying the impenetrability condition and smoothing the corner contact problem.The proposed approach is first validated through a disk test on an inclined slope.Then,several typical cases,such as granular collapse,bearing capacity,and deformation of a flexible retaining wall,are simulated to demonstrate the robustness of the proposed approach compared with FEM or analytical solutions.Finally,the proposed method is used to simulate the impact of sand flow on a deformable structure.The results show that the proposed contact approach can well describe the phenomenon of soil-structure interaction problems.

The study of lithographic variation in resistive random access memory

Reducing the process variation is a significant concern for resistive random access memory(RRAM).Due to its ultrahigh integration density,RRAM arrays are prone to lithographic variation during the lithography process,introducing electrical variation among different RRAM devices.In this work,an optical physical verification methodology for the RRAM array is developed,and the effects of different layout parameters on important electrical characteristics are systematically investigated.The results indicate that the RRAM devices can be categorized into three clusters according to their locations and lithography environments.The read resistance is more sensitive to the locations in the array(~30%)than SET/RESET voltage(<10%).The increase in the RRAM device length and the application of the optical proximity correction technique can help to reduce the variation to less than 10%,whereas it reduces RRAM read resistance by 4×,resulting in a higher power and area consumption.As such,we provide design guidelines to minimize the electrical variation of RRAM arrays due to the lithography process.

Genetic analysis and fine mapping of a grain size QTL in the smallgrain sterile rice line Zhuo201S

The development and application of the small-grain rice sterile line Zhuo201S(Z201S)has demonstrated its potential for mechanized hybrid rice seed production,leading to significant cost reductions.However,the molecular mechanism responsible for the small-grain size characteristic of Z201S remains unclear.In this study,we conducted a genetic analysis using near-isogenic lines constructed from Z210S,a small-grain rice sterile line,and R2115,a normal-grain variety.The results revealed that the small-grain trait in Z201S is governed by a single partially dominant gene which also enhances grain number.Through mapping,we localized the causal gene to the short arm of chromosome 2,within a 113 kb physical region delimited by the molecular markers S2-4-1 and LB63.Transgenic analysis and gene expression assays indicated LOC_Os02g14760 as the most likely candidate gene,suggesting that the small-grain size trait of Z201S is controlled by a novel locus that has not been previously identified.

Suppression of the m/n=2/1 tearing mode by electron cyclotron resonance heating on J-TEXT

Stabilization of tearing modes and neoclassical tearing modes is of great importance for tokamak operation.Electron cyclotron waves(ECWs)have been extensively used to stabilize the tearing modes with the virtue of highly localized power deposition.Complete suppression of the m/n=2/1 tearing mode(TM)by electron cyclotron resonance heating(ECRH)has been achieved successfully on the J-TEXT tokamak.The effects of ECW deposition location and power amplitude on the 2/1 TM suppression have been investigated.It is found that the suppression is more effective when the ECW power is deposited closer to the rational surface.As the ECW power increases to approximately 230 k W,the 2/1 TM can be completely suppressed.The island rotation frequency is increased when the island width is reduced.The experimental results show that the local heating inside the magnetic island and the resulting temperature perturbation increase at the O-point of the island play dominant roles in TM suppression.As the ECW power increases,the 2/1 island is suppressed to smaller island width,and the flow shear also plays a stabilizing effect on small magnetic islands.With the stabilizing contribution of heating and flow shear,the 2/1 TM can be completely suppressed.

立人·吃人·救人——以细读《狂人日记》为中心

鲁迅在早期就明确提出“立人”思想,进而提出立国的愿景。“立精神的人”,即平等、自由、独立的自我主体性个人。欲要“立人”,首要步骤是深刻地、历史地、全方位地暴露“吃人”的旧文化旧习惯,揭露其残酷性、非伦理性和虚伪性。描述和表现“吃人”并不是终极目标,其深层理想则是“救人”。鲁迅在《狂人日记》中使用近半的篇幅反复多次劝告“吃人”的人不要再“吃人”了,要真心悔改。“吃人”是暴露,“救人”则是深层的目标。

Diagnosis of indirectly driven double shell targets with point-projection hard x-ray radiography

We present an application of short-pulse laser-generated hard x rays for the diagnosis of indirectly driven double shell targets. Coneinserted double shell targets were imploded through an indirect drive approach on the upgraded SG-II laser facility. Then, based on thepoint-projection hard x-ray radiography technique, time-resolved radiography of the double shell targets, including that of their near-peakcompression, were obtained. The backlighter source was created by the interactions of a high-intensity short pulsed laser with a metalmicrowire target. Images of the target near peak compression were obtained with an Au microwire. In addition, radiation hydrodynamicsimulations were performed, and the target evolution obtained agrees well with the experimental results. Using the radiographic images, arealdensities of the targets were evaluated.

quarTeT: a telomere-to-telomere toolkit for gap-free genome assembly and centromeric repeat identification

A high-quality genome is the basis for studies on functional,evolutionary,and comparative genomics.The majority of attention has been paid to the solution of complex chromosome structures and highly repetitive sequences,along with the emergence of a new‘telomere-to-telomere(T2T)assembly’era.However,the bioinformatic tools for the automatic construction and/or characterization of T2T genome are limited.Here,we developed a user-friendly web toolkit,quarTeT,which currently includes four modules:AssemblyMapper,GapFiller,TeloExplorer,and CentroMiner.First,AssemblyMapper is designed to assemble phased contigs into the chromosome-level genome by referring to a closely related genome.Then,GapFiller would endeavor to fill all unclosed gaps in a given genome with the aid of additional ultra-long sequences.Finally,TeloExplorer and CentroMiner are applied to identify candidate telomere and centromere as well as their localizations on each chromosome.These four modules can be used alone or in combination with each other for T2T genome assembly and characterization.As a case study,by adopting the entire modular functions of quarTeT,we have achieved the Actinidia chinensis genome assembly that is of a quality comparable to the reported genome Hongyang v4.0,which was assembled with the addition of manual handling.Further evaluation of CentroMiner by searching centromeres in Arabidopsis thaliana and Oryza sativa genomes showed that quarTeT is capable of identifying all the centromeric regions that have been previously detected by experimental methods.Collectively,quarTeT is an efficient toolkit for studies of large-scale T2T genomes and can be accessed at http://www.atcgn.com:8080/quarTeT/home.html without registration.

Unified description of different soils based on the superloading and subloading concepts

Geotechnical engineering often involves different types of geomaterials,such as sandy soil and clayey soil.Existing studies have confirmed that these soils have some common features,i.e.their mechanical behaviors depend not only on the inherent characteristics but also on their initial states.To describe the main mechanical behaviors of different soils within a simple and reasonable constitutive framework is of great significance for the numerical analysis on geotechnical engineering.This paper first introduces a model based on the concepts of superloading and subloading,which considers the“state dependence”(effects of overconsolidation and structure)of soil and only adds two material parameters compared with the Cam-Clay model.Secondly,conventional triaxial tests are systematically carried out on four types of soils(i.e.sand,silty clay,clay,and intermediate soil)with different initial void ratios,and the mechanical similarities and differences of these soils are discussed uniformly.After that,six material parameters of these soils are uniformly determined based on the concepts of superloading and subloading,and then used in constitutive calculations to verify the feasibility.The calculated results show a good agreement with test data,indicating that the model based on the concepts of superloading and subloading has great potential for describing the general mechanical behaviors of different soils within a unified framework.This work is expected to be applied to constitutive selection and parameter determination in the geotechnical numerical analysis of complex soil profiles.

Responses of arid plant species diversity and composition to environmental factors

An oasis is a unique natural landscape in arid and semi-arid areas,significant for regulating regional microclimates and hydrological processes in deserts.However,little is known regarding the response of natural oasis plants communities to various environmental factors.Nineteen sample plots(50 m×50 m)were selected in the Daliyabuyi Oasis in the Taklimakan Desert hinterland based on the location of groundwater monitoring wells and 76 vegetation quadrats(25 m×25 m)were established.A two-way indicator species analysis,Mantel test,detrended correspondence analysis,canonical correspondence analysis(CCA),and hierarchical partitioning were used to provide an in-depth analysis of community classification,species composition,and environmental interpretation of the oasis.A generalized linear model was used to verify the results which showed that the current oasis community could be divided into four types according to the dominant species,which is controlled by soil moisture.Measurement of species composition and distribution of communities showed significant differences between species diversity of individual community types.Variations in groundwater depth affects patterns of species diversity which is sensitive to richness,while the degree of surface water disturbance affects the pattern of species evenness.Moreover,the CCA ordination map showed that community distribution and diversity characteristics have their own preferences in habitat gradients.The study concluded that the species dominance of the community and the composition and distribution are not dominated by a single factor.There are differences in the scale and effect of different water resource types in maintaining community characteristics.

Reabsorption of intervertebral disc prolapse after conservative treatment with traditional Chinese medicine:A case report

BACKGROUND Conservative treatments have been reported to diminish or resolve clinical symptoms of lumbar intervertebral disc herniation(LIDH)within a few weeks.CASE SUMMARY Computed tomography and magnetic resonance imaging(MRI)of the lumbar region of a 25-yearold male diagnosed with LIDH showed prolapse of the L5/S2 disc.The disc extended 1.0 cm beyond the vertebral edge and hung along the posterior vertebral edge.The patient elected a conservative treatment regimen that included traditional Chinese medicine(TCM),acupuncture,and massage.During a follow-up period of more than 12 mo,good improvement in pain was reported without complications.MRI of the lumbar region after 12 mo showed obvious reabsorption of the herniation.CONCLUSION A conservative treatment regimen of TCM,acupuncture,and massage promoted reabsorption of a prolapsed disc.