Non-dimensional analysis on blast wave propagation in foam concrete:Minimum thickness to avoid stress enhancement

Foam concrete is a prospective material in defense engineering to protect structures due to its high energy absorption capability resulted from the long plateau stage.However,stress enhancement rather than stress mitigation may happen when foam concrete is used as sacrificial claddings placed in the path of an incoming blast load.To investigate this interesting phenomenon,a one-dimensional difference model for blast wave propagation in foam concrete is firstly proposed and numerically solved by improving the second-order Godunov method.The difference model and numerical algorithm are validated against experimental results including both the stress mitigation and the stress enhancement.The difference model is then used to numerically analyze the blast wave propagation and deformation of material in which the effects of blast loads,stress-strain relation and length of foam concrete are considered.In particular,the concept of minimum thickness of foam concrete to avoid stress enhancement is proposed.Finally,non-dimensional analysis on the minimum thickness is conducted and an empirical formula is proposed by curve-fitting the numerical data,which can provide a reference for the application of foam concrete in defense engineering.

Protein changes in rice seedlings during the enhancement of chilling resistance by different stress pretreatment

The changes of proteins in the rice (Oryzasativa L.) Tesanai 2 seedling under salt (NaCl,4 g/L), heat shock (42℃, 3h ), and cold(14℃, 3d ) pretreatments were compared toexplore the mechanism of the cross adaptationto different environmental stresses. The chill-ing resistance of rice seedling after 1℃, 150pmol·msPFD(photo flux density) for 2d was enhanced distinctly by salt, heat shock,

Experimental investigation of electrode cycle performance and electrochemical kinetic performance under stress loading

Lithium-ion batteries suffer from mechano–electrochemical coupling problems that directly determine the battery life. In this paper, we investigate the electrode electrochemical performance under stress conditions, where seven tensile/compressive stresses are designed and loaded on electrodes, thereby decoupling mechanics and electrochemistry through incremental stress loads. Four types of multi-group electrochemical tests under tensile/compressive stress loading and normal package loading are performed to quantitatively characterize the effects of tensile stress and compressive stress on cycle performance and the kinetic performance of a silicon composite electrode. Experiments show that a tensile stress improves the electrochemical performance of a silicon composite electrode, exhibiting increased specific capacity and capacity retention rate, reduced energy dissipation rate and impedances, enhanced reactivity, accelerated ion/electron migration and diffusion, and reduced polarization. Contrarily, a compressive stress has the opposite effect, inhibiting the electrochemical performance. The stress effect is nonlinear, and a more obvious suppression via compressive stress is observed than an enhancement via tensile stress. For example, a tensile stress of 675 k Pa increases diffusion coefficient by 32.5%, while a compressive stress reduces it by 35%. Based on the experimental results, the stress regulation mechanism is analyzed. Tensile stress loads increase the pores of the electrode material microstructure, providing more deformation spaces and ion/electron transport channels. This relieves contact compressive stress, strengthens diffusion/reaction, and reduces the degree of damage and energy dissipation. Thus, the essence of stress enhancement is that it improves and optimizes diffusion, reaction and stress in the microstructure of electrode material as well as their interactions via physical morphology.

Nanomechanical sensor for rapid and ultrasensitive detection of tumor markers in serum using nanobody

Early cancer diagnosis requires ultrasensitive detection of tumor markers in blood.To this end,we develop a novel microcantilever immunosensor using nanobodies(Nbs)as receptors.As the smallest antibody(Ab)entity comprising an intact antigen-binding site,Nbs achieve dense receptor layers and short distances between antigen-binding regions and sensor surfaces,which significantly elevate the generation and transmission of surface stress.Owing to the inherent thiol group at the C-terminus,Nbs are covalently immobilized on microcantilever surfaces in directed orientation via one-step reaction,which further enhances the stress generation.For microcantilever-based nanomechanical sensor,these advantages dramatically increase the sensor sensitivity.Thus,Nb-functionalized microcantilevers can detect picomolar concentrations of tumor markers with three orders of magnitude higher sensitivity,when compared with conventional Ab-functionalized microcantilevers.This proof-of-concept study demonstrates an ultrasensitive,label-free,rapid,and low-cost method for tumor marker detection.Moreover,interestingly,we find Nb inactivation on sensor interfaces when using macromolecule blocking reagents.The adsorption-induced inactivation is presumably caused by the change of interfacial properties,due to binding site occlusion upon complex coimmobilization formations.Our findings are generalized to any coimmobilization methodology for Nbs and,thus,for the construction of high-performance immuno-surfaces.