Axisymmetric compressive buckling of multi-walled carbon nanotubes under different boundary conditions

The paper studies the axisymmetric compressive buckling behavior of multi-walled carbon nanotubes （MWNTs） under different boundary conditions based on continuum mechanics model. A buckling condition is derived for determining the critical buckling load and associated buckling mode of MWNTs, and numerical results are worked out for MWNTs with different aspect ratios under fixed and simply supported boundary conditions. It is shown that the critical buckling load of MWNTs is insensitive to boundary conditions, except for nanotubes with smaller radii and very small aspect ratio. The associated buckling modes for different layers of MWNTs are in-phase, and the buckling displacement ratios for different layers are independent of the boundary conditions and the length of MWNTs. Moreover, for simply supported boundary conditions, the critical buckling load is compared with the corresponding one for axial compressive buckling, which indicates that the critical buckling load for axial compressive buckling can be well approximated by the corresponding one for axisymmetric compressive buckling. In particular, for axial compressive buckling of double-walled carbon nanotubes, an analytical expression is given for approximating the critical bucklingload. The present investigation may be of some help in fur- ther understanding the mechanical properties of MWNTs.

Toxicity-efficacy converting of ginseng combined with Fuzi Banxia incompatibility in heart failure stage of cor pulmonale

Objective：Fuzi Banxia is one of eighteen antagonisms,previous studies have shown that the incompatibility could play special effects in the specific condition of diseases and appropriate compatible environment.The present study aims to evaluate the toxicity-efficacy of ginseng combined with Fuzi Banxia incompatibility intervening in the heart failure stage of cor pulmonale and to explore its mechanism.Methods：Monocrotaline（MCT）-induced cor pulmonale were used in this study.Ultra high-resolution small animal ultrasound real-time imaging system and the right heart catheterization were used to estimate cardiac function.Semi automatic biochemical analyzer was used to test myocardial enzyme LDH,CK,and CK-MB in serum.The heart tissues were stained with HE,and TUNEL assay was used to assess the pathomorphological changes and myocardial apoptosis.The expression of hypertrophy and apoptosis associated genes：ANP,BNP,β-MHC,Bax,and Bcl-2 in the right ventricle were determined by RT-PCR.Results：Fuzi Banxia combined with ginseng obviously attenuated mortality,decreased RVHI,and increased cardiac index;RVSP and m PAP were significantly reduced,and EF and FS were raised obviously;Myocardial enzymes LDH,CK,and CK-MB were pronounced attenuated;heart diameter reduced,right ventricular dilatation was significantly decreased,inflammatory cell infiltration notably reduced,and cardiac apoptosis rate was decreased obviously.Meanwhile,the expression of hypertrophy-related ANP,BNP,andβ-MHC m RNA were up-regulated,the expression of apoptosis-related Bax m RNA was down-regulated,and the expression of anti-apoptosis-related Bcl-2 m RNA and Bcl-2/Bax ratio were upregulated.Conclusion：Ginseng compatible environment could attenuate cardiac toxicity of Fuzi Banxia incompatibility intervening in the heart failure stage of cor pulmonale,and improve cardiac function,which may be related to the expression of hypertrophy and apoptosis associated genes,and thus delay the occurrence and development of heart failure.