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Xiaohua Zhou

Publications and source records attributed to Xiaohua Zhou.

25 records · Page 2Linked to original sources
arXiv2013

Manipulate the coiling and uncoiling movements of Lepidoptera proboscis by its conformation optimizing

Many kinds of adult Lepidoptera insects possess a long proboscis which is used to suck liquids and has the coiling and uncoiling movements. Although experiments revealed qualitatively that the coiling movement is governed by the hydraulic mechanism and the uncoiling movement is due to the musculature and the elasticity, it needs a quantitative investigation to reveal how insects achieve these behaviors accurately. Here a quasi-one-dimensional (Q1D) curvature elastica model is proposed to reveal the mechanism of these behaviors. We find that the functions of internal stipes muscle and basal galeal muscle which locate at the bottom of proboscis are to adjust the initial states in the coiling and uncoiling processes, respectively. The function of internal galeal muscle which exists along proboscis is to adjust the line tension. The knee bend shape is due to the local maximal spontaneous curvature and is an advantage for nectar-feeding butterfly. When there is no knee bend, the proboscis of fruit-piercing butterfly is easy to achieve the piercing movement which induced by the increase of internal hydraulic pressure. All of the results are in good agreement with experiential observation. Our study provides a revelatory method to investigate the mechanical behaviors of other 1D biologic structures, such as proboscis of marine snail and elephant. Our method and results are also significant in designing the bionic devices.

q-bio.TO↗
arXiv2012

A one-dimensional continuous model for carbon nanotubes

The continuous two-dimensional (2D) elastic model for single-walled carbon nanotubes (SWNTs) provided by Tu and Ou-Yang in [Phys. Rev. B \textbf{65}, 235411 (2003)] is reduced to a one-dimensional (1D) curvature elastic model strictly. This model is in accordance with the isotropic Kirchhoff elastic rod theory. Neglecting the in-plane strain energy in this model, it is suitable to investigate the nature features of carbon nanotubes (CNTs) with large deformations and can reduce to the string model in [Phys. Rev. Lett. \textbf{76}, 4055 (1997)] when the deformation is small enough. For straight chiral shapes, this general model indicates that the difference of the chiral angle between two equilibrium states is about $π/6$, which is consistent with the lattice model. It also reveals that the helical shape has lower energy for per atom than the straight shape has in the same condition. By solving the corresponding equilibrium shape equations, the helical tube solution is in good agreement with the experimental result, and super helical shapes are obtained and we hope they can be found in future experiments.

cond-mat.mes-hall↗
arXiv2009

Periodic-cylinder vesicle with minimal energy

We give some details about the periodic cylindrical solution found by Zhang and Ou-Yang in [Phys. Rev. E 53, 4206(1996)] for the general shape equation of vesicle. Three different kinds of periodic cylindrical surfaces and a special closed cylindrical surface are obtained. Using the elliptic functions contained in \emph{mathematic}, we find that this periodic shape has the minimal total energy for one period when the period-amplitude ratio $β\simeq1.477$, and point out that it is a discontinuous deformation between plane and this periodic shape. Our results also are suitable for DNA and multi-walled carbon nanotubes (MWNTs)

cond-mat.soft↗
arXiv2009

Stability analysis of kinked DNA in $\mathcal{F}(K,τ)$ model

We phenomenologically analyze short DNA rings' stability by discussing the second variation of its elastic free energy. Through expanding the perturbation functions as Fourier series, we obtain DNA rings' stability condition in a general case. By reviewing the relationship between the Kirchhoff model and the worm-like road chain (WLRC) model, we insert a spontaneous curvature term which can partly reflect the twist angle's contribution to free energy in the WLRC model and name this extended model the EWLRC model. By choosing suitable spontaneous curvature, stability analysis in this model provide us with some useful results which are consistent with the experimental observations.

cond-mat.soft↗
arXiv2009

The First and Second Variation of the Total Energy of Closed Duplex DNA in Planar Case

DNA's shape mostly lies on its total energy $F$. Its corresponding equilibrium shape equations can be got by classical variation method: letting the first energy variation $δ^{(1)}F=0$. Here we not only provide the first variation $δ^{(1)}F$ but also give the second variation $δ^{(2)}F$ in planar case. Moreover, the general shape equations of DNA are obtained and a mistake in [Zhang, \emph{et al}. {\it Phys. Rev. E} {\bf 70} 051902 (2004)] is pointed out.

cond-mat.soft↗