Effects of Finite Deformed Length in Carbon Nanotubes

The effect of finite deformed length is demonstrated by squashing an armchair (10,10) single-walled carbon nanotube with two finite tips. Only when the deformed length is long enough, an effectual metal-semiconductor-metal heterojunction can be formed in the metallic tube. The effect of finite deformed length is explained by the quantum tunnelling effect. Furthermore, some conceptual designs of nanoscale devices are proposed from the metal-semiconductor-metal heterojunction.Comment: 4 pages, 4 figure

Obesity and Heart Diseases, a Worsened Epidemic in Recent Decades

Overweight and obesity are major risk factors for a number of chronic diseases, including diabetes, cardiovascular diseases and metabolic diseases. Obesity induces serious heart diseases such as hypertension, heart failure, and coronary disease by multiple mechanisms. The endothelial dysfunction and artherosclerosis induced by obesity lead to the result of coronary artery disease. In addition, obesity is a substantial public health crisis worldwide, and internationally, with the prevalence increasing rapidly in numerous industrialized nations. Worldwide, 39% of adults aged 18 years and over were overweight in 2014, and 13% were obese. The first choice of treatment is weight loss by life-style modification, such as diet and exercise. Medication and surgery are for moderate obese patients with comorbidity. How to find the appropriate method of weight losing is the most important issue

Role of Symmetry in the Transport Properties of Graphene Nanoribbons under Bias

The intrinsic transport properties of zigzag graphene nanoribbons (ZGNRs) are investigated using first principles calculations. It is found that although all ZGNRs have similar metallic band structure, they show distinctly different transport behaviors under bias voltages, depending on whether they are mirror symmetric with respect to the midplane between two edges. Asymmetric ZGNRs behave as conventional conductors with linear current-voltage dependence, while symmetric ZGNRs exhibit unexpected very small currents with the presence of a conductance gap around the Fermi level. This difference is revealed to arise from different coupling between the conducting subbands around the Fermi level, which is dependent on the symmetry of the systems.Comment: 4 pages, 4 figure

Structural Trends Interpretation of the Metal-to-Semiconductor Transition in Deformed Carbon Nanotubes

Two mechanisms that drive metal-to-semiconductor transitions in single-walled carbon nanotubes are theoretically analyzed through a simple tight-binding model. By considering simple structural trends, the results demonstrate that metal-to-semiconductor transitions can be induced more readily in metallic zigzag nanotubes than in armchair nanotubes. Furthermore, it is shown that both mechanisms have the effect of making the two originally equivalent sublattices physically distinguishable.Comment: 4 pages, 4 figure