Submergence induced changes of molecular species in membrane lipids in Arabidopsis thaliana

The composition of membrane lipids is sensitive to environmental stresses.Submergence is a type of stress often encountered by plants.However,how the molecular species of membrane lipids respond to submergence has not yet been characterised.In this study,we used a lipidomic approach to profile the molecular species of membrane lipids in whole plants of Arabidopsis thaliana that were completely submerged for three days.The plants survived one day of submergence,after which,we found that the total membrane lipids were only subtly decreased,showing significant decreases of monogalactosyldiacylglycerol(MGDG)and phosphatidylcholine(PC)and an increase of phosphatidic acid(PA);however,the basic lipid composition was retained.In contrast,three days of submergence caused plants to die,and the membranes deteriorated via the rapid loss of 96% of lipid content together with a 229% increase in PA.The turnover of molecular species from PG and MGDG to PA indicated that submergenceinduced lipid changes occurred through PA-mediated degradation.In addition,molecular species of extraplastidic PG degraded sooner than plastidic ones,lyso-phospholipids exhibited various patterns of change,and the double-bond index(DBI)remained unchanged until membrane deterioration.Our results revealed the unique changes of membrane lipids upon submergence and suggested that the major cause of the massive lipid degradation could be anoxia.

Computation method of zero-stress state of pneumatic stressed membrane structure

The whole analysis process of pneumatic stressed membrane structure contains nine states and seven analysis processes.The zero-stress state is the corner-stone of analysis and design of pneumatic stressed structure,and has significant impact on the pre-stressed state and load state.According to the logical model of the whole numerical analysis process of pneumatic stressed structure,a numerical analysis method to solve the zero-stress state from the elasticized equilibrium state was firstly proposed,called linear compatibility matrix M-P inverse method.Firstly,the pneumatic membrane stressed structure was transferred into grid structure by using membrane link to simulate membrane surface.Secondly,on the basis of equilibrium matrix theory of pin joint structure and small deformation assumption,compatibility equation of system was established.Thirdly,the unstressed length and elongation of links were calculated from the tension and material parameters of elasticized equilibrium state.Finally,using compatibility matrix M-P inverse,the nodal displacement was calculated by solving compatibility equation,the configuration of zero-stress state could be obtained through reverse superposition,and the stress was released.According to the algorithm,the program was coded with MATLAB.The correctness and efficiency of this method were verified by several numerical examples,and it could be found that one elasticized equilibrium state corresponded to one configuration of the zero-stress state.The work has theoretical significance and practical guidance value for pneumatic membrane structural design.

Effect of dual and new generation wide-base tire assembly on inverted pavements

The conventional flexible pavements have been constructed such that the stiffness of the layer reduces with depth.The crust thickness becomes significantly high for heavy traffic corridors resulting in the consumption of large quantities of construction materials and also increasing environmental pollution.Inverted pavements with the aggregate interlayer(AIL)or stress absorbing membrane interlayer(SAMI)are considered to be one of the alternatives for thick conventional flexible pavements for heavy traffic corridors.The AIL or SAMI is placed between a stiff cement-treated base and asphalt concrete layer to function as crack relief layers.This change in the composition alters the behaviour of inverted pavements compared to the conventional flexible pavements.On the other hand,wide-base tires are being increasingly preferred by trucking industries due to increased fuel economy and cargo capacity.However,the effect of wide-base tires on the performance of inverted pavements is yet to be investigated.In this study,the 3D finite element(FE)models of inverted pavements considering different crack relief layers were developed,and load from dual-wheel and wide-base tires were applied.The stress-strain evolution in the various layers of inverted pavements was investigated and discussed in this study.The results indicated the higher stress and strains due to wide base tires compared to the dual-wheel assembly.Further,pavement with SAMI was found to result in lower stress and strains in the asphalt concrete layer compared to AIL pavements.