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This work investigates the detailed difference between dielectric function models, the Mermin model and the full Penn algorithm (FPA) model, for the determination of an electron inelastic mean free path (IMFP) with optical energy loss function (ELF), as an extension of our previous study [Da et al., Surf. Interface Anal. 51, 627 (2019)] by using the simple Drude-type ELF. In the conventional normal Mermin (NM) model, the approximations of ELF by the Drude equation will introduce inevitable fitting error. In order to enhance the accuracy of the NM model, our previous proposed extended Mermin model [Da et al., Phys. Rev. Lett. 113, 063201 (2014)], which is renamed as a super-extended Mermin algorithm (SE-MA) now, is employed to eliminate the error by expanding the definition of Drude oscillators used in the NM. In the SE-MA, the Drude-like oscillators allow the existence of negative strengths to express the fine structures of phonon–electron scattering and the plasmon lifetime broadening effect. Because in our previous study, the simple Drude-type ELF cannot include these complex structures, in this work, the electron IMFPs are calculated for five realistic materials, Al, Si, Cu, Au, and MgO. The difference between IMFPs calculated by the SE-MA model and the FPA model is material dependent and is significant in the low energy region, which is analyzed by using the Fano plot. This is due to the more important role played by the plasmon lifetime broadening effect. [ABSTRACT FROM AUTHOR]

Two screw-thread pre-stressed high strength steel bars used in a wind turbine foundation fractured suddenly and unexpectedly after being loaded by a pre-stress for a number of hours. In this paper, on the one hand, a series of tests were conducted to determine the failure cause of the bars. The results suggest that the failure was caused by hydrogen-assisted cracking (HAC). An amount of hydrogen had invaded into the bars, and a number of inclusions were found in the bars. The large-size inclusions caused very high stress concentration around them, consequently resulting in excessive accumulation of hydrogen as the stress can enhance hydrogen diffusion and accumulation. The coexistence of high stress concentration and hydrogen accumulation around inclusions induced HAC, finally causing the failure. On the other hand, based on hydrogen-influenced cohesive zone modeling (CZM), finite element calculations were performed to simulate the crack initiation in the bars. The results indicate that the CZM has a potential to predict such kind of crack initiation assisted by hydrogen, and can offer a numerical technique to determine whether HAC may occur in an actual inclusion- and hydrogen-containing pre-stressed high strength steel structure. [ABSTRACT FROM AUTHOR]

Sophoridine is a type of alkaloid extract derived from the Chinese herb Sophora flavescens Ait (kushen) and possess a variety of pharmacological effects including anti-inflammation, antianaphylaxis, anti-cancer, anti-arrhythmic and so on. However, the effect of sophoridine on heart failure has not been known yet. In this study, the effect of sophoridine on heart failure was investigated using Sprague-Dawley (SD) rat model of chronic heart failure. Morphological results showed that in medium and high dose group, myofilaments were arranged orderly and closely, intermyofibrillar lysis disappeared and mitochondria contained tightly packed cristae compared with heart failure group. We investigated the Ca2+ induced Ca2+ transients and assessed the expression of ryanodine receptor (RyR2) and L-type Ca2+ channel (dihydropyridine receptor, DHPR). We found that the cytosolic Ca2+ transients were markedly increased in amplitude in medium (▵ F/F0=43.33±1.92) and high dose groups (▵ F/F0=47.21±1.25) compared with heart failure group (▵ F/F0=16.7±1.29, P<0.01), Moreover, we demonstrated that the expression of cardiac DHPR was significantly increased in medium- and high dose-group compared with heart failure rats. Our results suggest that sophoridine could improve heart failure by ameliorating cardiac Ca2+ induced Ca2+ transients, and that this amelioration is associated with upregulation of DHPR. [ABSTRACT FROM AUTHOR]

Residual stresses and deformation in the butt welding of an ultrathick tube-sheet in a large scale reactor are predicted by finite element method. The effect of applied load on residual stress and deformation has been discussed. When the tube-sheet is welded without any constraint and applied load, large angular deformation is generated due to the large amount of heat input, the nonuniform temperature distribution, and shrinkage. In order to decrease the angular deformation, a heavy load is applied at both ends of tube-sheet. With the applied load increase from 5×104 to 45×104kg, the deformation decreases but the residual stress increases. When the load is beyond 45×104kg, the deformation mode is changed from angular deformation to arch deformation. An optimized load of 45×104kg is determined. The zone of peak residual stress is increased as the applied load increases. Too heavy a load generates a serious constraint on deformation, which in turn leads to higher residual stress. [ABSTRACT FROM AUTHOR]

This paper used finite element method (FEM) to predict the residual stresses in repair weld of a stainless steel clad plate. The effects of clad metal thickness and base metal thickness on residual stresses have been investigated. The results show that large residual stresses have been generated in weld metal and heat affected zone (HAZ). The clad metal and base metal thickness have a great effect on residual stresses. With clad metal thickness increase, the deformation and plastic strain are increased to relax some residual stress, which leads to a decrease in residual stress. The repair structure has an angular deformation for the shrinkage of weld metal. The strength of base metal is great larger than that of clad metal, and therefore, the base metal has a constraint on the shrinkage of clad metal. As the base metal thickness increase, this constraint function is enhanced, which leads to an increase in residual stress, which provides a reference for the repair welding of stainless steel clad plate. [ABSTRACT FROM AUTHOR]

Co-electrodeposition of functionalized multi-walled carbon nanotubes (f-MWCNTs) with chitosan was performed on pieces of a stainless steel mainspring. Under moderate conditions, composite coatings with controllable thickness from a few hundred nanometers to tens of micrometers can be achieved. After coating an 8 microm composite layer on a piece of mainspring 120 microm thick (i.e. 6.7% increase in thickness), the Young's modulus of the mainspring was found to have increased by more than approximately 25%. Moreover, the coated mainsprings possess much stronger mechanical strength as demonstrated by fatigue tests. The significant enhancement of Young's modulus and intrinsic strength are mostly attributed to the effect exerted by the subtle combination of chitosan and MWCNT. In the current study, the intensive cross-linkages formed between the -COOH groups in f-MWCNTs and the hydroxyl (-OH) and amino (-NH2) groups in chitosan were exploited. The chitosan molecular chains and f-MWCNTs both chemically react and physically knot with each other, leading to a three-dimensional interlaced f-MWCNT/chitosan composite coating. The reported co-electrodeposition provides a simple approach to form a stable, reproducible and rigid f-MWCNTs composite coating, which leads to the realization of a high-performance mainspring with reinforced mechanical strength.