On complete and micropolar-based incomplete strain gradient theories for periodic lattice structures

The micropolar(MP) and strain gradient(SG) continua have been generally adopted to investigate the relations between the macroscopic elastic constants and the microstructural geometric parameters. Owing to the fact that the microrotation in the MP theory can be expressed in terms of the displacement gradient components, we may regard the MP theory as a particular incomplete SG theory called the MPSG theory,compared with the existing SG theories which are deemed complete since all the SGs are included. Taking the triangular lattice comprising zigzag beams as an example, it is found that as the angle of the zigzag beams increases, the bending of the beams plays a more important role in the total strain energy, and the difference between the results by the two theories gradually decreases. Finally, the models are verified with the pure bending and simple shear of lattices by comparing with the results obtained by the finite element method(FEM)-based structure analyses.

On band gaps of nonlocal acoustic lattice metamaterials:a robust strain gradient model

We have proposed an"exact"strain gradient(SG)continuum model to properly predict the dispersive characteristics of diatomic lattice metamaterials with local and nonlocal interactions.The key enhancement is proposing a wavelength-dependent Taylor expansion to obtain a satisfactory accuracy when the wavelength gets close to the lattice spacing.Such a wavelength-dependent Taylor expansion is applied to the displacement field of the diatomic lattice,resulting in a novel SG model.For various kinds of diatomic lattices,the dispersion diagrams given by the proposed SG model always agree well with those given by the discrete model throughout the first Brillouin zone,manifesting the robustness of the present model.Based on this SG model,we have conducted the following discussions.(Ⅰ)Both mass and stiffness ratios affect the band gap structures of diatomic lattice metamaterials,which is very helpful for the design of metamaterials.(Ⅱ)The increase in the SG order can enhance the model performance if the modified Taylor expansion is adopted.Without doing so,the higher-order continuum model can suffer from a stronger instability issue and does not necessarily have a better accuracy.The proposed SG continuum model with the eighth-order truncation is found to be enough to capture the dispersion behaviors all over the first Brillouin zone.(Ⅲ)The effects of the nonlocal interactions are analyzed.The nonlocal interactions reduce the workable range of the well-known long-wave approximation,causing more local extrema in the dispersive diagrams.The present model can serve as a satisfactory continuum theory when the wavelength gets close to the lattice spacing,i.e.,when the long-wave approximation is no longer valid.For the convenience of band gap designs,we have also provided the design space from which one can easily obtain the proper mass and stiffness ratios corresponding to a requested band gap width.

Integrin β5 subunit regulates hyperglycemia-induced vascular endothelial cell apoptosis through FoxO1-mediated macroautophagy

Background:Hyperglycemia frequently induces apoptosis in endothelial cells and ultimately contributes to microvascular dysfunction in patients with diabetes mellitus(DM).Previous research reported that the expression of integrins as well as their ligands was elevated in the diseased vessels of DM patients.However,the association between integrins and hyperglycemia-induced cell death is still unclear.This research was designed to investigate the role played by integrin subunit β5(ITGB5)in hyperglycemia-induced endothelial cell apoptosis.Methods:We used leptin receptor knockout(Lepr-KO)(db/db)mice as spontaneous diabetes animal model.Selective deletion of ITGB5 in endothelial cell was achieved by injecting vascular targeted adeno-associated virus via tail vein.Besides,we also applied small interfering RNA in vitro to study the mechanism of ITGB5 in regulating high glucose-induced cell apoptosis.Results:ITGB5 and its ligand,fibronectin,were both upregulated after exposure to high glucose in vivo and in vitro.ITGB5 knockdown alleviated hyperglycemia-induced vascular endothelial cell apoptosis and microvascular rarefaction in vivo.In vitro analysis revealed that knockdown of either ITGB5 or fibronectin ameliorated high glucose-induced apoptosis in human umbilical vascular endothelial cells(HUVECs).In addition,knockdown of ITGB5 inhibited fibronectin-induced HUVEC apoptosis,which indicated that the fibronectin-ITGB5 interaction participated in high glucose-induced endothelial cell apoptosis.By using RNA-sequencing technology and bioinformatic analysis,we identified Forkhead Box Protein O1(FoxO1)as an important downstream target regulated by ITGB5.Moreover,we demonstrated that the excessive macroautophagy induced by high glucose can contribute to HUVEC apoptosis,which was regulated by the ITGB5-FoxO1 axis.Conclusion:The study revealed that high glucose-induced endothelial cell apoptosis was positively regulated by ITGB5,which suggested that ITGB5 could potentially be used to predict and treat DM-related vascular complications.

New insights into the formation of ammonium nitrate from a physical and chemical level perspective

High levels of fine particulate matter(PM_(2.5))is linked to poor air quality and premature deaths,so haze pollution deserves the attention of the world.As abundant inorganic components in PM_(2.5),ammonium nitrate(NH_(4)NO_(3))formation includes two processes,the diffusion process(molecule of ammonia and nitric acid move from gas phase to liquid phase)and the ionization process(subsequent dissociation to form ions).In this study,we discuss the impact of meteorological factors,emission sources,and gaseous precursors on NH4NO3 formation based on thermodynamic theory,and identify the dominant factors during clean periods and haze periods.Results show that aerosol liquid water content has a more significant effect on ammonium nitrate formation regardless of the severity of pollution.The dust source is dominant emission source in clean periods;while a combination of coal combustion and vehicle exhaust sources is more important in haze periods.And the control of ammonia emission is more effective in reducing the formation of ammonium nitrate.The findings of this work inform the design of effective strategies to control particulate matter pollution.

Highly efficient heritable genome editing in wheat using an RNA virus and bypassing tissue culture.

Genome editing provides novel strategies for improving plant traits,but relies on current genetic transformation and plant regeneration procedures,which can be inefficient.We have engineered a barley stripe mosaic virus(BSMV)-based sgRNA delivery vector(BSMV-sg)that is effective in performing heritable genome editing in Cas9-transgenic wheat plants.Mutated progenies were present in the next generation at frequencies ranging from 12.9%to 100%in three different wheat varieties,and 53.8%to 100%of mutants were virus-free.We also achieved multiplex mutagenesis in progeny using a pool of BSMV-sg vectors harboring different sgRNAs.Furthermore,we devised a virus-induced transgene-free editing procedure(VITF-Edit)to generate Cas9-free wheat mutants by crossing BSMV-infected Cas9-transgenic wheat pollen with wild-type wheat.Our study provides a robust,convenient and tissue culture-free approach for genome editing in wheat through virus infection.

Generation of thermosensitive male-sterile maize by targeted knockout of the ZmTMS5 gene

Maize（Zea mays L.）is one of the most important cereal crops,with a global production of 1.02 billion tons in 2013（Baldaufa et al.,2016）.Heterosis is widely used to increase the productivity of maize,and the first commercial hybrid maize was introduced in the 1930s（Duvick,2001）.

Transient expression of a TaGRF4-TaGIF1 complex stimulates wheat regeneration and improves genome editing

Genome editing is an unprecedented technological breakthrough but low plant regeneration frequencies and genotype dependence hinder its implementation for crop improvement. Here, we found that transient expression of a complex of the growth regulators TaGRF4 and TaGIF1(TaGRF4-TaGIF1) increased regeneration and genome editing frequency in wheat. When we introduced synonymous mutation in the miR396 target site of TaGRF4, the resulting complex(mTaGRF4-TaGIF1) performed better than original TaGRF4-TaGIF1. Use of m TaGRF4-TaGIF1 together with a cytosine base editor targeting TaALS resulted in 2-9-fold increases in regeneration and transgene-free genome editing in 11 elite common wheat cultivars. Therefore, m TaGRF4-TaGIF1 will undoubtedly be of great value in crop improvement and especially in commercial applications, since it greatly increased the range of cultivars available for transformation.

Biolistic Genetic Transformation of a Wide Range of Chinese Elite Wheat(Triticum aestivum L.)Varieties

Wheat （Triticum aestivum L.） is a major staple food crop worldwide. It is economically important because it can be grown in a wide range of climates and geographic regions, and it has made an enormous contribution to the increase in global food production over the past four decades （Dixon et al., 2009）. Wheat is produced on more than 18% of the arable land in the world, and is the most cultivated crop after maize and rice （FAOSTAT data, 2014）. Despite its global strategic significance, progress in genomic and genetic engineering research on wheat has lagged behind that on other major crops due to the difficulty of culturing tissues, and the complexity of its hexaploid genome. The first successful wheat trans- formation was achieved by particle bombardment （Vasil et al., 1992）. Since then additional transgenic wheat plants have been obtained by various transformation methods （Harwood, 2011）. Microprojectile bombardment is considered to be a promising method, since it is robust, versatile and relatively efficient in terms of gene delivery.

关于纳米弹性窄带的回弹时间研究

我们通过数值模拟和理论建模两种方法研究了纳米尺寸单晶铜窄带的回弹行为,分析了回弹时间的各种影响因素.通过固定窄带两端并于其中点施加静荷载,使窄带产生初始弯曲.随后通过移除中点静何载促使回弹行为发生.本研究分别使用分子动力学模拟软件LAMMPS和考虑表面张力的连续力学模型对纳米弹性窄带回弹进行了研究.研究发现表面张力的增加会导致回单时间的增加.研究结果还表明回弹行为与窄带初始弯曲程度和窄带厚度均具有密切联系.此外,对比分子动力学模拟和连续模型所得结果,我们还发现两种方法获得的回弹时间处于同一量级.这一结论十分独特且有意义,因为目前分子动力学模拟结果在时间尺度上往往与实验结果存在巨大差异、我们相信,本研究关于回弹这一自发运动的研究有助于在一定程度上阐述分子动力学模拟所得的变形行为时间尺度远小于实验结果的原因.