有机化蒙脱土对XLPE/OMMT纳米复合电介质微观形态及水树枝老化特性的影响

文中采用熔融共混法分别制备了交联聚乙烯/有机化蒙脱土(XLPE/OMMT)纳米复合电介质,研究有机化蒙脱土种类对纳米复合电介质微观形态和水树枝老化特性的影响。对试样进行力学性能测试发现,OMMT质量分数为0.5%时,综合力学性能达到最佳;利用差示扫描量热法和扫描电子显微镜研究了试样的微观形态,经双十八烷基苄基季铵盐有机化改性并细化的有机化蒙脱土(OMMT3)起到明显的异相成核作用,使晶体更加完善,结晶度高达25.3%,晶体平均尺寸仅为16.67μm;采用水针电极法对各试样进行加速水树枝老化试验,剥离分散的OMMT3片层形成了更加曲折的迷宫路径,其对水分子的阻隔效应与XLPE交联网状结构对分子链运动束缚的共同作用,有效抑制了XLPE/OMMT3试样中水树枝的生长,引发概率下降至23.4%;傅里叶变换红外光谱对水树枝老化前后的化学结构进行了表征,纳米复合电介质水树区的羰基指数增加、羟基振动峰增强,表明水树枝老化是电化学降解的作用;在水树枝生长过程中,XLPE/OMMT3试样老化断链较少,表现出较优的耐热氧老化性能。

OsWRKY78 regulates panicle exsertion via gibberellin signaling pathway in rice

Panicle exsertion is one of the crucial agronomic traits in rice(Oryza sativa).Shortening of panicle exsertion often leads to panicle enclosure and severely reduces seed production.Gibberellin(GA)plays important roles in regulating panicle exsertion.However,the underlying mechanism and the relative regulatory network remain elusive.Here,we characterized the oswrky78 mutant showing severe panicle enclosure,and found that the defect of oswrky78 is caused by decreased bioactive GA contents.Biochemical analysis demonstrates that OsWRKY78 can directly activate GA biosynthesis and indirectly suppress GA metabolism.Moreover,we found OsWRKY78 can interact with and be phosphorylated by mitogen-activated protein kinase(MAPK)kinase OsMAPK6,and this phosphorylation can enhance OsWRKY78 stability and is necessary for its biological function.Taken together,these results not only reveal the critical function of OsWRKY78,but also reveal its mechanism via mediating crosstalk between MAPK and the GA signaling pathway in regulating panicle exsertion.

Extraction and Antioxidant Activity Analysis of Crude Polysaccharides from Wild Lactarius volemus Fr. in Yunnan Province

[ Objective ] This study aimed to investigate the optimal extraction process of crude polysaccharides from wild Lactarius volemus Fr. in Yunnan Province and preliminarily analyzed its antioxidant activity in vitro. [ Method ] With water extraction and alcohol precipitation method, the optimal conditions for extracting crude polysaccharides from wild L. volemus Ft. were screened by single-factor and orthogonal experiments. The antioxidant activity of the extracted crude polysac- charides was determined with DPPH assay. [ Result ] The optimal conditions for pigment removal with activated carbon were： activated carbon amount of 20 g/L, water bath time of 40 min, water bath temperature of40 ℃ ; the optimal conditions for extracting crude polysaccharides from wild L. vo/emus Fr. with hot water ex- traction method were： hot water extraction time of 3 h, solid-liquid ratio of 1： 45, extraction frequency of twice. Under the optimized extraction conditions, the yield of crude polysaccharides was 21.33 mg/g. In addition, the antioxidant activity of 0. 665 mg/ml crude polysaccharides was 52.46% ; the amount of crude polysac- eharides was proportional to the antioxidant activity. [ Conclusion] Hot water extraction method can be used as a high-efficiency extraction technology of crude pol- ysaecharides from wild L. volemus Fr. with simple operation and low costs. Crude polysaccharides extracted from L. volemus Ft. exhibited certain antioxidant activi- ty in vitro.

Study on the water-tree ageing characteristics of polyethylene/organic montmorillonite and crosslinked polyethylene/organic montmorillonite nanocomposites

The dispersion state of nanoparticles affects the properties of composites,and the crosslinking process of polymers affects the dispersion state of nanoparticles.In order to investigate the effects of crosslinking behaviour on the water-tree ageing characteristics of nanocomposite dielectrics at the molecular level,polyethylene/organic-montmorillonite(PE/organic montmorillonite(OMMT))and crosslinked polyethylene/organic-montmorillonite(XLPE/OMMT)nanocomposites were prepared by the melt blending method,after which the accelerated water-tree ageing experiments were conducted using a needle electrode.Fourier transform infrared spectroscopy,differential scanning calorimetry,successive self-nucleation annealing and scanning electron microscope(SEM)tests were conducted to characterise the properties of the samples before and after watertree ageing.The results indicate that the initiation probability and the length of water trees in XLPE/OMMT are less than those in PE/OMMT.The carbonyl index in the watertree area of the two nanocomposites increases,indicating that the water-tree ageing is the result of electrochemical degradation.The crystallisability of the water-tree area degrades,decreasing the crystallinity and the lamellar thickness.The growth of water trees destroys molecular chains and crystal structures,which results in local cracks.There are many holes for the water tree growth in the PE/OMMT specimen.However,the crosslinked meshwork not only restricts the movement of macromolecular chains but also increases the stability of the lamellar barrier effect of OMMT.The combination of the two effects significantly improves the water-tree resistance of the XLPE/OMMT nanocomposite.

High-speed high-resolution laser diode-based photoacoustic microscopy for in vivo microvasculature imaging

Laser diodes(LDs)have been considered as cost-effective and compact excitation sources to overcome the requirement of costly and bulky pulsed laser sources that are commonly used in photoacoustic microscopy(PAM).However,the spatial resolution and/or imaging speed of previously reported LD-based PAM systems have not been optimized simultaneously.In this paper,we developed a high-speed and high-resolution LD-based PAM system using a continuous wave LD,operating at a pulsed mode,with a repetition rate of 30 kHz,as an excitation source.A hybrid scanning mechanism that synchronizes a one-dimensional galvanometer mirror and a two-dimensional motorized stage is applied to achieve a fast imaging capability without signal averaging due to the high signal-to-noise ratio.By optimizing the optical system,a high lateral resolution of 4.8μm has been achieved.In vivo microvasculature imaging of a mouse ear has been demonstrated to show the high performance of our LD-based PAM system.

Research on the Grain Producers around the Year of Chinese Population Peak

The issue of "who will grow grain in the future in China" attracts more and more attention. We estimate the structure of China's grain producers at present,and summarize the phenomena and reasons why peasants would not like to grow grain. We analyze the agricultural population at the time of China's total population peak around 2033,and we predict there will be a multi-producer structure of grain growing.The household contracts will be as the basis of grain operations then,and the quantity of small-scale households will decrease but still be huge.The degree of organization of rural households will increase and the role of cooperatives will be strengthened remarkably. We propose the " quality" requirements to ensure the grain production,and note different special groups will be the new forces on farming and grain growing.

Combinations of Hd2 and Hd4 genes determine rice adaptability to Heilongjiang Province, northern limit of China

Heading date is a key trait in rice domestication and adaption, and a number of quantitative trait loci（QTLs）have been identified. The rice（Oryza sativa L.） cultivars in the Heilongjiang Province, the northernmost region of China,have to flower extremely early to fulfill their life cycle.However, the critical genes or different gene combinations controlling early flowering in this region have not been determined. QTL and candidate gene analysis revealed that Hd2/Ghd7.1/Os PRR37 plays a major role in controlling rice distribution in Heilongjiang. Further association analysis with a collection of rice cultivars demonstrated that another three major QTL genes（Hd4/Ghd7, Hd5/DTH8/Ghd8, and Hd1）also participate in regulating heading date under natural long day（LD） conditions. Hd2/Ghd7.1/Os PRR37 and Hd4/Ghd7 are two major QTLs and function additively. With the northward rice cultivation, the Hd2/Ghd7.1/Os PRR37 and Hd4/Ghd7 haplotypes became non-functional alleles. Hd1 might be non-functional in most Heilongjiang rice varieties,implying that recessive hd1 were selected during local rice breeding. Non-functional Hd5/DTH8/Ghd8 is very rare, but constitutes a potential target for breeding extremely early flowering cultivars. Our results indicated that diverse genetic combinations of Hd1, Hd2, Hd4, and Hd5 determined the different distribution of rice varieties in this northernmost province of China.

OsMKKK70 regulates grain size and leaf angle in rice through the OsMKK4-OsMAPK6-OsWRKY53 signaling pathway

Grain size and leaf angle are key agronomic traits that determine final yields in rice.However,the underlying molecular mechanisms are not well understood.Here we demonstrate that the Oryza sativa Mitogen Activated Protein Kinase Kinase Kinase OsMKKK70 regulates grain size and leaf angle in rice.Overexpressing OsMKKK70 caused plants to produce longer seeds.The osmkkk62/70 double mutant and the osmkkk55/62/70 triple mutant displayed significantly smaller seeds and a more erect leaf angle compared to the wild type,indicating that OsMKKK70 functions redundantly with its homologs Os MKKK62 and Os MKKK55.Biochemical analysis demonstrated that OsMKKK70 is an active kinase and that OsMKKK70 interacts with Os MKK4 and promotes Os MAPK6 phosphorylation.In addition,the osmkkk62/70 double mutant showed reduced sensitivity to Brassinosteroids(BRs).Finally,overexpressing constitutively active Os MKK4,Os MAPK6,and Os WRKY53 can partially complement the smaller seed size,erect leaf,and BR hyposensitivity of the osmkkk62/70 double mutant.Taken together,these findings suggest that OsMKKK70 might regulate grain size and leaf angle in rice by activating Os MAPK6 and that OsMKKK70,Os MKK4,Os MAPK6,and Os WRKY53 function in a common signaling pathway that controls grain shape and leaf angle.

Oryza sativa mediator subunit OsMED25 interacts with OsBZR1 to regulate brassinosteroid signaling and plant architecture in rice

Brassinosteroids(BRs)are plant-specific steroid hormones which regulate plant growth,development,and adaptation.Transcriptional regulation plays key roles in plant hormone signaling.A mediator can serve as a bridge between gene-specific transcription factors and the RNA polymerase machinery,functioning as an essential component in regulating the transcriptional process.However,whether a mediator is involved in BR signaling is unknown.Here,we discovered that Oryza sativa mediator subunit 25(Os MED25)is an important regulator of rice BR signaling.Phenotypic analyses showed that the Os MED25-RNAi and osmed25 mutant presented erect leaves,as observed in BR-deficient mutants.In addition,the Os MED25-RNAi and osmed25 mutant exhibited decreased BR sensitivity.Genetic analysis indicated that Os MED25-RNAi could suppress the enhanced BR signaling phenotype of Osbzr1-D.Further biochemical analysis showed that Os MED25 interacts with Os BZR1 in vivo,and Os MED25 is enriched on the promoter of Os BZR1 target genes.RNA sequencing analysis indicated that Os MED25 affects the expression of approximately 45%of Os BZR1-regulated genes and mainly functions as a corepressor of Os BZR1.Together,these findings revealed that Os MED25 regulates rice BR signaling by interacting with Os BZR1 and modulating the expression of Os BZR1 target genes,thus expanding our understanding of the roles of mediators in plant hormone signaling.

员工-组织双赢:发展型人力资源管理实践的影响及其作用机制

基于员工-组织双赢的视角,考察了发展型人力资源管理实践对员工工作绩效与工作幸福感的影响及其边界条件与作用机制。获取到53家企业的53名主管和152名员工在两个时间点的有效配对数据,通过多层次线性模型检验发现:发展型人力资源管理实践对员工的工作绩效和工作幸福感有显著正向影响;人力资本在上述过程中发挥了中介作用;组织学习目标导向不仅正向调节了发展型人力资源管理实践与人力资本的关系,并且调节了人力资本在发展型人力资源管理实践与工作绩效和工作幸福感之间的中介作用。

High-efficiency breeding of early-maturing rice cultivars via CRISPR/Cas9-mediated genome editing

Rice is a staple food for more than half of the human population.It has been estimated that by 2030,40%more rice needs to be produced in order to meet the growing demand（Khush,2005）.One of the strategies to improve rice productivity is to enlarge rice growth areas, such as the northward expansion of the growth region in Heilongjiang Province, the northernmost region of China （Li et al., 2015）. However, the northward cultivation is accompanied with daylength extension and temperature decrease, which are unfavor- able for rice, a tropical short-day plant, to complete flowering and seed setting. Thus, the need for early-maturing rice cultivars with extremely low photoperiod sensitivity is urgent.

bZIP71 delays flowering by suppressing Ehd1 expression in rice

Flowering time is a fundamental factor determining the global distribution and final yield of rice(Oryza sativa).Although diverse flowering time genes have been reported in this crop,the transcriptional regulation of its key flowering genes are poorly understood.Here,we report that a basic leucine zipper transcription factor,bZIP71,functions as a flowering repressor.The overexpression of bZIP71 delays flowering,while the bzip71 mutant flowers early in both long-day and short-day conditions.A genetic analysis showed that the regulation of flowering by bZIP71 might be independent of Heading date 2(Hd2),Hd4,and Hd5.Importantly,bZIP71 directly associates with the Early heading date 1(Ehd1)promoter and represses its transcription,and genetically the function of bZIP71 is impaired in the ehd1 mutant.Moreover,bZIP71 interacts with major components of polycomb repressive complex 2(PRC2),SET domain group protein 711(SDG711),and Fertilization independent endosperm 2(FIE2),through which bZIP71 regulates the H3K27me3 level of Ehd1.Taken together,we present a transcriptional regulatory mechanism in which bZIP71 enhances the H3K27me3 level of Ehd1 and transcriptionally represses its expression,which not only offers a novel insight into a flowering pathway,but also provides a valuable putative target for the genetic engineering and breeding of elite rice cultivars.