The structure relaxation of carbon nanotube

A simple macroscopic continuum elasticity theory (CET) is used to calculate the structure relaxation of single-wall carbon nanotube (SWNT), an analytic formula is obtained. We also expand an atomic scale three-parameter empirical model [ T. Lenosky {\emph et al.} Nature 355, 333(1992)] in order to correctly describe the bond-length change effects. The structure relaxation of SWNT expected by the model is good in agreement with our CET results, and very well consistent with the previous calculation from a first principles local density function approximation. Using the expanded Lenosky model, we calculate the strain energy of bending tube. The obtained results are good in agreement with the previous theoretical expectation. It shows the model may be a good simple replacement of some more sophisticated methods on determining carbon networks deformations.Comment: 9 pages, 4 eps figure

The strain energy and Young's Moduli of single-wall Carbon nanotubules calculated from the electronic energy-band theory

The strain energies in straight and bent single-walled carbon nanotubes (SWNTs) are calculated by taking account of the total energy of all the occupied band electrons. The obtained results are in good agreement with previous theoretical studies and experimental observations. The Young's modulus and the effective wall thickness of SWNT are obtained from the bending strain energies of SWNTs with various cross-sectional radii. The repulsion potential between ions contributes the main part of the Young's modulus of SWNT. The wall thickness of SWNT comes completely from the overlap of electronic orbits, and is approximately of the extension of $\pi$ orbit of carbon atom. Both the Young's modulus and the wall thickness are independent of the radius and the helicity of SWNT, and insensitive to the fitting parameters. The results show that continuum elasticity theory can serve well to describe the mechanical properties of SWNTs.Comment: 12 pages, 2 figure

Determinants of depressive symptoms in older outpatients with cardiometabolic diseases in a Japanese frailty clinic: Importance of bidirectional association between depression and frailty.

IntroductionFrailty and depression may play important roles in the management of older patients with cardiometabolic diseases. We explored the determinants of depressive symptoms and their association with frailty among patients with cardiometabolic diseases (hypertension, diabetes, and atrial fibrillation) in a cross-sectional study.MethodsA total of 633 outpatients aged 65 years or older with cardiometabolic disease and suspected symptoms of frailty participated in this study. Depressive symptoms, physical activity, and social network were assessed using the Geriatric Depression Scale (GDS)-15, International Physical Activity Questionnaire, and Lubben Social Network Scale-6 (LSNS-6), respectively. Frailty was evaluated using the Kihon Checklist (KCL) based on the Comprehensive Geriatric Assessment (CGA), the modified Cardiovascular Health Study (mCHS), and the Clinical Frailty Scale (CFS). Binomial logistic regression analysis was used to examine the determinants of depressive symptoms and their association with frailty.ResultsDepressive symptoms with GDS-15 scores ≥ 5 were present in 43.6% of the patients. In logistic regression, after adjusting for covariates, the determinants of depressive symptoms in all patients were lack of social network, low years of education, and frailty. In contrast, in logistic regression with frailty as the dependent variable, depressive symptoms were independently associated KCL-defined frailty (OR = 6.28, 95% CI: 4.13-9.55) and mCHS-defined frailty (OR = 2.66, 95% CI: 1.70-4.17), but not with CFS. Similarly, significant associations between depression and frailty were observed in patients with hypertension, diabetes, or atrial fibrillation.ConclusionsLack of social networks, low education, and frailty based on the KCL and mCHS were important determinants of depressive symptoms in all patients. The relatively strong associations between depressive symptoms and frailty based on CGA in patients with hypertension, diabetes, or atrial fibrillation suggest that the assessment of depressive symptoms is of great importance in clinical practice in those patients at high risk of frailty