优化合成工艺的增韧预浸料树脂及其复合材料的性能

根据流变性能、凝胶时间等参数确定了预浸料树脂的基础配方,并根据固化后树脂浇注体表面质量优化预浸料树脂的合成工艺,降低能耗的同时解决了双氰胺分散不均的问题。引入气相纳米SiO_(2)组分作为增韧剂(最佳添加量为1%),增韧后树脂浇注体拉伸强度为74.41 MPa、冲击强度为20.23 kJ/m^(2),比原配方分别提高了72.64%和58.79%。最终确定预浸料树脂配方为E-51、E-20、NPCN704、双氰胺、二氯苯基二甲脲、气相纳米SiO_(2)和消泡剂的质量比50:30:20:7:2:1:0.2,根据差示扫描量热分析(DSC)的非等温曲线外推法确定树脂配方的固化工艺为100℃/1 h+130℃/2 h+150℃/2 h。将自制预浸料树脂与商用预浸料树脂进行浇注体和复合材料的力学性能对比,结果表明,自制预浸料树脂各项性能较为优异。采用真空辅助成型工艺制备了玻纤和碳纤增强自制预浸料树脂复合材料,树脂含量分别控制在40%和35%为宜。

人工智能与面向未来的学习分析

学习分析是指在教学活动中分析教和学活动的过程,是面向未来智能教育跨学科培养人才的关键技术。当前,如何通过对学习环境和学习活动数据的收集和分析,为学生提供新的学习机会,引起教育界前所未有的关注。而人工智能的迅速发展和在教育中的广泛运用,为以学习者为中心的数据分析提供了新的机会和挑战,也为解决教育教学中的许多棘手问题提供了新的可能。文章回顾了近几年国际上学习分析研究和应用方面所面临的挑战和主要成就;探讨未来学习分析发展中,如何从人工智能等相关技术和领域的研究中受益;剖析学习分析框架中数据收集、模型建立及实践应用中的关键问题;并运用大量的实证研究案例,展示学习分析在自主学习、发展学习策略、解决个人和小组合作学习评价问题中的应用潜力。在此基础上,文章从数据使用和获取、模型优化和实施、模型可解释性、学术研究四个层面,提出未来学习分析的研究建议。

Synergistic effects of peroxydisulfate on UV/O_(3) process for tetracycline degradation:Mechanism and pathways

Tetracycline(TC)as a typical emerging pollutant is becoming a serious threat to the environment and human health.A combined advanced oxidation technology of UV/Ozone(O_(3))/peroxydisulfate(PDS)process was developed to explore an efficient and economic treatment process of TC in wastewater.Furthermore,the reactive sites and transformation pathways of TC were explored and the toxicity of the intermediates was quantified with a quantitative structure-activity relationship(QSAR)assessment.The degradation performance of TC was substantially enhanced in UV/O_(3)/PDS process with a kobsof 0.0949 min-1,which was 2.3 times higher than UV/O_(3)and 3.2 times than sole UV.The results demonstrated that there was a superior synergistic effect of PDS on UV/O_(3)processes for the degradation of TC.Electron paramagnetic resonance(EPR)analysis and quenching experiments show that·OH,SO_(4)·-,O_(2)·-and1O_(2)all contributed to TC degradation in the UV/O_(3)/PDS process and exhibited a synergistic effect,which inhibited the generation of harmful products.In addition,the UV/O_(3)/PDS system can effectively degrade TC in a wide range of substrate concentrations and pH,and also showed excellent adaptability to various concentrations of anions(Cl-and HCO_(3)-).This study proves the feasibility of UV/O_(3)/PDS process for treating TC contaminated wastewater with complicated water matrix.

The landscape of gene-CDS-haplotype diversity in rice:Properties,population organization,footprints of domestication and breeding,and implications for genetic improvement

Polymorphisms within gene coding regions represent the most important part of the overall genetic diversity of rice.We characterized the gene-coding sequence-haplotype(gcHap)diversity of 45963 rice genes in 3010 rice accessions.With an average of 226±390 gcHaps per gene in rice populations,rice genes could be classified into three main categories:12865 conserved genes,10254 subspecific differentiating genes,and 22844 remaining genes.We found that 39218 rice genes carry>255179 major gcHaps of potential functional importance.Most(87.5%)of the detected gcHaps were specific to subspecies or populations.The inferred proto-ancestors of local landrace populations reconstructed from conserved predominant(ancient)gcHaps correlated strongly with wild rice accessions from the same geographic regions,supporting a multiorigin(domestication)model of Oryza sativa.Past breeding efforts generally increased the gcHap diversity of modern varieties and'caused significant frequency shifts in predominant gcHaps of 14266 genes due to independent selection in the two subspecies.Low frequencies of“favorable”gcHaps at most known genes related to rice yield in modern varieties suggest huge potential for rice improvement by mining and pyramiding of favorable gcHaps.The gcHap data were demonstrated to have greater power than SNPs for the detection of causal genes that affect complex traits.The rice gcHap diversity dataset generated in this study would facilitate rice basic research and improvement in the future.

The First High-quality Reference Genome of Sika Deer Provides Insights into High-tannin Adaptation

Sika deer are known to prefer oak leaves,which are rich in tannins and toxic to most mammals;however,the genetic mechanisms underlying their unique ability to adapt to living in the jungle are still unclear.In identifying the mechanism responsible for the tolerance of a highly toxic diet,we have made a major advancement by explaining the genome of sika deer.We generated the first high-quality,chromosome-level genome assembly of sika deer and measured the correlation between tannin intake and RNA expression in 15 tissues through 180 experiments.Comparative genome analyses showed that the UGT and CYP gene families are functionally involved in the adaptation of sika deer to high-tannin food,especially the expansion of the UGT family 2 subfamily B of UGT genes.The first chromosome-level assembly and genetic characterization of the tolerance to a highly toxic diet suggest that the sika deer genome may serve as an essential resource for understanding evolutionary events and tannin adaptation.Our study provides a paradigm of comparative expressive genomics that can be applied to the study of unique biological features in non-model animals.

Fiber structures and material science in optical fiber magnetic field sensors

Magnetic feld sensing plays an important role in many felds of scientifc research and engineering applications.Benefting from the advantages of optical fbers,the optical fber-based magnetic feld sensors demonstrate characteristics of light weight,small size,remote controllability,reliable security,and wide dynamic ranges.This paper provides an overview of the basic principles,development,and applications of optical fber magnetic feld sensors.The sensing mechanisms of fber grating,interferometric and evanescent feld fber are discussed in detail.Magnetic fuid materials,magneto-strictive materials,and magneto-optical materials used in optical fber sensing systems are also introduced.The applications of optical fber magnetic feld sensors as current sensors,geomagnetic monitoring,and quasi-distributed magnetic sensors are presented.In addition,challenges and future development directions are analyzed.

Hydrophilic/underwater superoleophobic graphene oxide membrane intercalated by TiO2 nanotubes for oil/water separation

Membrane technology for oil/water separation has received increasing attention in recent years. In this study, the hydrophilic/underwater superoleophobic membrane with enhanced water permeability and antifouling ability were fabricated by synergistically assembling graphene oxide （GO） nanosheets and titanium dioxide （TiO2） nanotubes for oil/water separation. GO/TiO2 membrane exhibits hydrophilic and underwater superoleophobic properties with water contact angle of 62° and under water oil contact angle of 162.8°. GO/TiO2 membrane shows greater water permeability with the water flux up to 531 L/ （m^2·h·bar）, which was more than 5 times that of the pristine GO membrane. Moreover, GO/TiO2 membrane had excellent oil/water separation efficiency and anti-oil-fouling capability, as oil residual in filtrate after separation was below 5 mg/L and flux recovery ratios were over 80%.The results indicate that the intercalation of TiO2 nanotubes into adjacent GO nanosheets enlarged the channel structure and modified surface topography of the obtained GO/TiO2 membranes, which improved the hydrophilicity, permeability and anti-oil-fouling ability of the membranes, enlightening the great prospects of GO/TiO2 membrane in oil-water treatment.

Time effects of rice straw and engineered bacteria on reduction of exogenous Cu mobility in three typical Chinese soils

Globally,copper(Cu)accumulation in soils is a major environmental concern.Agricultural organic waste and some bacterial species can readily absorb metals in an eco-friendly manner,and thus are commonly used in metal-contaminated soil remediation.This study investigates the change in Cu fractions during the aging process and the time effects of rice straw(RS)and engineered bacteria(EB)(Pseudomonas putida X4/pIME)on reduction of Cu mobility.Three typical Chinese soils(red,cinnamon,and black soils)were incubated with RS or RS+EB in the presence of exogenous Cu for 24 months.The soil physicochemical properties,reactive soil components,Cu fractions,and Cu mobility were determined over time.The Cu mobility factor(MF)values were the lowest in the black soil(6.4-9.2)because of its high organic carbon and clay contents.The additions of both RS and RS+EB accelerated Cu stabilization during the aging process in all three soils.The Cu MF values decreased with time during the initial 20 months;however,the MF values increased thereafter in all soils,which might be due to the reduction of humic substances and amorphous iron oxides and the increase in iron oxides complexed on the organic matter.The reduction rates of Cu MF were similar after 16,24,and more than 24 months in the red,cinnamon,and black soils,respectively,indicating that RS and RS+EB could limit Cu mobility at different times in various soils.The RS treatment showed the greatest efficiency in reducing Cu mobility in the red,cinnamon,and black soils after 12,12,and 8 months of incubation,respectively.The RS+EB treatment was more efficient than the RS treatment in the red soil during the initial 8 months of the incubation period.Our study provides theoretical support for Cu risk assessments and RS supplementation for Cu remediation in different soils.

A hybrid membrane process for simultaneous thickening and digestion of waste activated sludge

A hybrid membrane process for simultaneous sludge thickening and digestion(MSTD)was studied.During one cycle(15 d)of operation under a hydraulic retention time of 1 d,the concentration of mixed liquor suspended solids(MLSS)continuously increased from about 4 g·L^(–1)to 34 g·L^(–1),and the mixed liquor volatile suspended solids(MLVSS)increased from about 3 g·L^(–1)to over 22 g·L^(–1).About 42%of the MLVSS and 39%of the MLSS reduction were achieved.The thickening and digestion effects in the MSTD were further analyzed based on a mass balance analysis.Test results showed that biopolymers and cations of biomass were gradually released to the bulk solution during the process.It was also found that the capillary suction time,colloidal chemical oxygen demand,soluble microbial products,viscosity,and MLSS had significant positive correlations with the membrane fouling rate,whereas extracellular polymeric substances,polysaccharides,and proteins extracted from biomass had negative impacts on membrane fouling.

Expanding the Scope of CRISPR/Cpfl-Mediatec Senome Editing in Rice

Dear Editor The CRISPR/Cas gene editing system offers great potential for functional genomics in plants and crop improvement. The spec- ificity of Cas-directed DNA cleavage is strictly determined by a chimeric single guide RNA （sgRNA） and a short protospacer adjacent motif （PAM） in the genome （Cong et al., 2013; Zetsche et al., 2015）. The widely used SpCas9 and its variants have been shown to recognize PAM sequences in the canonical form NGG and non-canonical NGA, NAG, or NGCG in plants （Miao et al., 2013; Ma et al., 2015; Hu et al., 2016）. CRISPR/Cpfl, a new class 2 CRISPR/Cas system, was recently exploited as an alternative tool for genome editing in various organisms, including plants （Zetsche et al., 2015; Kim et al., 2017; Tang et at., 2017; Wang et al., 2017; Xu et al., 2017）. Cpfl utilizes a thymidine-rich PAM site, TTTN, and is guided by a single CRISPR RNA （crRNA） （Zetsche et al., 2015）.

In-situ preparation of robust self-lubricating composite coating from thermally sprayed ceramic template

The self-lubricating ceramic coatings that can control friction and wear have attracted researchers’widespread attention.However,the poor interfacial bonding between lubricants and ceramics and the deterioration of mechanical properties due to a tribological design limit their practical applications.Here,a robust self-lubricating coating was fabricated by an in-situ synthesis of MoS_(2)/C within inherent defects of thermally sprayed yttria-stabilized zirconia(YSZ)coatings.The edge-pinning by noncoherent endows hybrid coatings with excellent interfacial strength,increasing their hardness(HV)and cohesive strength.Furthermore,owing to the formation of a well-covered robust lubricating film at a frictional interface,a coefficient of friction(COF)can be reduced by 79.6%to 0.15,and a specific wear rate(W)drops from 1.36×10^(−3) to 6.27×10^(−7) mm^(3)·N^(−1)·m^(−1).Combining outstanding mechanical properties and tribological performance,the hybrid coating exhibits great application potential in controlling friction and wear.Importantly,this strategy of introducing the target materials into the inherent defects of the raw materials to improve the relevant properties opens new avenues for the design and preparation of composite materials.

Single-atom nanozymes with axial ligand-induced self-adaptive conformation in alkaline medium boost chemiluminescence

Mimicking the structure of natural enzymes for designing advanced alternatives provides great opportunities to address the bottleneck of enzyme-involved chemiluminescence(CL). Herein, according to theoretical calculations, we found that an endogenous axial ligand of M-N-C single-atom nanozymes(SAzymes), originating from OH-spontaneously bonding to the metal center in an alkaline medium, can self-adaptively change its strength to facilitate intermediate steps. Furthermore, the lowest energy barrier of the rate-determining step and the strongest affinity and fastest electron transfer with luminol anion endow CoN-C with the highest peroxidase-like activity. Guided by the theoretical calculations, a series of M-N-C SAzymes(M=Fe, Co,Ni) were synthesized to boost CL, where Co-N-C SAzymes with superior catalytic activity and high selective generation of O_(2)·- were validated. As a proof-of-concept, Co-N-C SAzymes were employed for sensitive detection of acetylcholinesterase and organophosphorus pesticide.

Dynamics of cavity soliton driven by chirped optical pulses in Kerr resonators

Recent researches have demonstrated that pulsed driving is an effective method to increase the temporal overlap between cavity soliton(CS)and pump field,thereby increasing the pump-to-comb conversion efficiency.The amplitude-modulated inhomogeneity of the background wave causes the solitons to drift toward edges of the driving pulse.To eliminate the mul-tiple temporal trapping positions,induced by the spontaneous symmetry breaking,we propose the chirped pulse driving for deterministic single soliton generation.We theoretically explain the physical mechanism of the chirp pulse driving,as the combination of amplitude and phase modulation.Our numerical simulations demonstrate the chirp is responsible for the single soliton generation.A detailed investigation for dynamics of CSs sustained by chirped pulses,shows the recovery of spontaneous symmetry breaking.In addition,the desynchronized chirped pulse driving is also considered here.Considering a weak chirp parameter,the desynchronization-dependent trapping position diagram is divided into multiple areas including two CSs,a single CS,two oscillating CSs,and no CS.With a sufficient chirp parameter considered,the trapping position curve becomes a monotonous function of the desynchronized drift velocity,which indicates deterministic single soliton generation.

The CCAAT/Enhancer Binding Protein Beta(cebpb)is essential for the development of enveloping layer(EVL)in zebrafish

Epiboly,the coordinated spreading of the enveloping layer(EVL),the yolk syncytial layer(YSL)and the deep cells(DCs)toward the vegetal pole,is required for gastrulation.Interference with the EVL leads to early developmental failure.However,the genetic factors underlying EVL differentiation are so far unknown.By in-depth analyzing of single-cell sequencing data from 4 h post fertilization zebrafish embryos,we identified 105 genes(FDR<0.05)which showed highly specific EVL expression,among which the transcription factor cebpb and genes(krt18,cldne,cldnb,krt4,krt5)involved in cell-cell junction formation were exclusively expressed in EVL.To explore the role of cebpb in EVL differentiation,we knocked down its expression by morpholino-labeled antisense RNA.The morphant embryos showed disrupted EVL and developmental termination prior to epiboly.In accordance,expression of the EVL specific cell-adhesion molecule genes were significantly reduced.Thus,cebpb is the earliest EVL marker and essential for EVL differentiation in zebrafish.The elucidation of the specific EVL gene set provides us new insights into the molecular mechanisms underlying EVL differentiation.