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During an aircraft taxiing on a water-contaminated runway, the worn tires with shallower grooves will significantly deteriorate the safety of take-off and landing. The hydrodynamics generated by the tire-water-pavement interaction is numerically studied using the coupling method of Smoothed Particle Hydrodynamics and Finite Element Method. By comparing a completely worn tire with a new tire, the effects of tire wear on water spray and water displacement drag are analyzed. With the increasing tire speed and water film depth, the water spray composed of bow wave and side plume increases, and the water displacement drag decomposed of wave- and film-generated components also increases. The effects of tire wear depend on the relative height of tire grooves to the water film depth. For the shallow water film with a depth smaller than the grooves height, the water spray and water displacement drag of new tire is much smaller than those of worn tire, because the groove drainage effect can work very well. While for the deep water film that completely floods the grooves, the water spray and water displacement drag of new tire are similar with those of worn tires, because the groove drainage effect cannot be fully utilized. [ABSTRACT FROM AUTHOR]

During the taxiing of an aircraft on a water-contaminated runway, the rolling tires impact water film resulting in a considerable water displacement drag and a large amount of spray, which will affect the safety of take-off and landing. The characteristics and flow mechanism of the water displacement drag generated by an elastic tire are numerically studied based on the coupling method of Smoothed Particle Hydrodynamics and Finite Element Method. The water displacement drag is divided into wave-generated drag and film-generated drag based on flow mechanism for the first time, and the former is much larger than the latter. The water displacement drag satisfies the Gaussian distribution along the rotation axis. The longitudinal grooves cause a significant increase in the wave-generated drag and a reduction in the film-generated drag. A simple potential flow model around a semi-infinite bluff body is proposed to reveal the flow physics of film-generated drag. Two drag formulas are proposed to quickly predict the wave-generated drag and film-generated drag. [ABSTRACT FROM AUTHOR]

Spinach (Spinacia oleracea L.) is one of most important leafy vegetables because of its high nutritional value and high oxalate content, which can be toxic with negative effects on human nutrition. Ammonium and nitrate can effectively regulate oxalate accumulation, although the mechanisms underlying the oxalate biosynthesis and regulation are still undetermined in plants. In the present study, we identified 25 putative genes that are involved in the oxalate biosynthetic and degradation pathway, before analyzing the oxalate content and the expression levels of the corresponding proteins under normal growth conditions, with or without ammonium and nitrate treatments, using high and low oxalate-accumulated spinach genotypes. The two cultivars exhibited different profiles of total oxalate and soluble oxalate accumulation. The high oxalate concentrations in spinach were as a result of the high transcription levels of the genes that are involved in oxalate biosynthesis under normal growth conditions, such as SoGLO2, SoGLO3, three SoOXACs, SoMLS, SoMDH1, SoMDH2, and SoMDH4. The results revealed that the ammonium and nitrate were able to control the oxalate content in leaves, possibly because of the different transcription levels of the genes. The oxalate content is regulated by complex regulatory mechanisms and is varied in the different varieties of spinach. The results from this research may be used to assist the investigation of the mechanism of oxalate regulation and breeding for reduced oxalate content in spinach. [ABSTRACT FROM AUTHOR]

The phenomenon of granular flows appears frequently in industrial and daily life. The particle–particle interaction plays an important role in granular flows, which makes the flows have some strong nonlinear characteristics and so different from the normal materials, either solids or liquids. Discrete element method (DEM) is a powerful tool to catch this interaction in meso-scopic scale. A brief review of DEM is presented, including some of our new works in this area. DEM can also be coupled with other CFD methods for simulations of solid–liquid suspension flow. An example of such coupling is presented in this article as well. [ABSTRACT FROM AUTHOR]

Diseases cause a significant loss in both yield and quality of spinach. The cell cycle signalling pathway plays a central role in balancing development and immunity of plants. Cyclin-Dependent Kinase Inhibitor (CKI) is a core cell cycle regulator. It has been found that two Arabidopsis CKIs, SIAMESE (SIM) and SMR1 (SIAMESE-Related 1), function redundantly not only as negative regulators of cell proliferation but also as positive regulators of plant immunity. In the spinach genome, we identified a homologue of Arabidopsis SIM, referred to asSpinacia oleraceaSIAMESE (SoSIM). To investigate the function of SoSIM, we introduced the35Spromoter-drivenSoSIM(35S:SoSIM) into Arabidopsissim smr1double mutants. Over-expression ofSoSIMphenocopied RNA interference ofCyclin-Dependent Kinase A1(CDKA1) which exhibited dwarf and serrated leaves, confirming that SIM is a CDK inhibitor. Arabidopsis wild-type trichomes are single and unicellular, whereassim smr1mutant trichomes are clustered and multicellular. SoSIM restored wild-type trichome phenotype ofsim smr1mutant. Thesim smr1mutants were susceptible to the avirulent pathogenPseudomonas syringaepv.maculicolaas compared with wild-type plants. Our data showed that the resistance of35S:SoSIM-transgenicsim smr1lines to the pathogen was fully restored, indicating that SoSIM activates plant immunity. These data verify that SoSIM functions as its Arabidopsis counterpart in inhibition of plant development and activation of plant immunity. Therefore, SoSIM can be explored to control the balance between development and immunity in spinach. [ABSTRACT FROM PUBLISHER]

Spinach (Spinacia oleracea L.) is a nutritious vegetable enriched with many essential minerals and vitamins. A reference spinach genome has been recently released, and additional spinach genomic resources are being rapidly developed. Therefore, there is an urgent need of a central database to store, query, analyze and integrate various resources of spinach genomic data. To this end, we developed SpinachBase (http://spinachbase.org), which provides centralized public accesses to genomic data as well as analytical tools to assist research and breeding in spinach. The database currently stores the spinach reference genome sequence, and sequences and comprehensive functional annotations of protein-coding genes predicted from the genome. The database also contains gene expression profiles derived from RNA-Seq experiments as well as highly co-expressed genes and genetic variants called from transcriptome sequences of 120 cultivated and wild Spinacia accessions. Biochemical pathways have been predicted from spinach protein-coding genes and are available through a pathway database (SpinachCyc) within SpinachBase. SpinachBase provides a suite of analysis and visualization tools including a genome browser, sequence similarity searches with BLAST, functional enrichment and functional classification analyses and functions to query and retrieve gene sequences and annotations. [ABSTRACT FROM AUTHOR]