[Current application and prospect of accurate navigation technology in orthopaedic trauma]

In the past decades,a dramatic development of navigation technology in orthopaedic surgery has been witnessed. By assisting the localization of surgical region,verification of target bony structure,preoperative planning of fixation,intraoperative identification of planned entry point and direction of instruments or even automated insertion of implants,its ability and potential to reduce operation time,intraoperative radiation,surgical trauma,and improve accuracy has been proved. However,in contrast to the widespread use of navigation technology in arthroplasty,orthopaedic tumor,and spine surgery,its application in orthopaedic trauma is relatively less. In this manuscript,the main purpose is to introduce the technical principles of navigation devices,outline the current clinical application of navigation systems in orthopaedic trauma,analyze the current challenges confronting its further application in clinical practice and its prospect in the future.

Effective interaction of nonuniformly charged colloid spheres in a bulk electrolyte

The interaction energy between two like-charged colloid spheres with nonuniformly distributed surface charges immersed in a bulk electrolyte is calculated under the linearized Poisson-Boltzmann equation. The calculated results are sensitive to the relative orientations of the spheres due to the anisotropy of the distribution of charges on the sphere surface. The effective repulsive interaction after thermal average is weaker than the case when charges are uniformly distributed on the spheres, and with the increase of the nonuniformity, an attractive interaction between the two spheres emerges.

Polynomial scheme for time evolution of open and closed quantum systems

Based on the generating function of Laguerre polynomials, we propose a Laguerre polynomial expansion scheme in the calculation of the evolution of the time-dependent Schrödinger equation. Theoretical analysis and numerical tests show that the method is equally as good as the Chebyshev polynomial expansion method in efficiency and accuracy, with the additional merits that no scaling to the Hamiltonian is needed and it has wider suitability.

Reentrant wetting transition on surfactant solution surfaces

The wetting of polydimethylsiloxane oil drops on the surfaces of anionic surfactant sodium dodecylsulfate solutions is studied systematically by changing the bulk surfactant concentration. The wetting state changes from complete wetting to pseudopartial wetting at 0.3 cmc (critical micelle concentration) surfactant concentration and there is a reentrant transition back to complete wetting at 1.4 cmc. The measured free energy is consistent with the prediction of the wetting theory. The interaction potential minimum of the two surfaces of the oil film disappears at the reentrant point, which is speculated to be an effect of micelle formation in the solution.

Depletion interactions between two spherocylinders

The depletion interactions between two spherocylinders as functions of their separation and their relative orientation, induced by a small hard-sphere fluid, are calculated by Monte Carlo simulations using the acceptance ratio method (ARM). The torque on the spherocylinders is determined from the resulting potential. The calculation shows that the ARM is an effective way to obtain depletion interactions of spherocylinders. The depletion interaction under the Asakura-Oosawa (also excluded-volume) approximation is also calculated numerically.

The density distributions of the counterions and the coions confined in two similarly charged plates

By using the field-theoretic method, we established a unified systematic formulation of a model of counterions and coions confined in two similarly charged plates, and calculated the density distributions of counterions and coions with various coupling parameters by the two methods: Poisson-Boltzmann (PB) approach and the strong coupling (SC) theory, respectively. We also performed Monte Carlo simulations, and obtained the density distributions of counterions and coions with several different coupling parameters. Comparing our theoretical results with those from Monte Carlo simulation, we find that the PB approach is valid when the coupling parameter Xi is smaller than 1, but, as Xi > or = 1, the results by the PB approach deviate from the corresponding Monte Carlo simulation data, and the deviation gets larger with the coupling parameter increasing. This shows that the PB approach is completely invalid when the coupling parameter is equal to 1 or larger than 1. For the latter case, the development trend of the distribution curve calculated by SC theory agrees with that from Monte Carlo simulation as the coupling parameter increases. This demonstrates that the SC theory can give a qualitative available explanation on the density distribution of the counterions in the system in which the coupling parameters are strictly confined.

Entropic interactions on a colloidal sphere near the edge of a terrace

We calculated the entropic interactions between a colloidal sphere and the hard edge of a terrace by means of Monte Carlo simulation with the acceptance ratio method. Comparison with the Asakura-Oosawa approximation indicates that the AO approximation is more accurate in this model than other known models. Our simulation results are also in qualitative agreement with the experimental results obtained by A.D. Dinsmore et al.

Depletion potential near curved surfaces

We examine the depletion potential and force of a hard-sphere fluid on a single big hard sphere, located inside or outside of a hard spherical cavity, by Monte Carlo simulations to the hard-sphere fluid. The depletion potential is determined by the acceptance ratio method, while the force on the big sphere is obtained by two methods: numerical differentiation of the depletion potential and integration of the contact density of the fluid at the surface of the big sphere. The results are in excellent agreement with those obtained by density functional theory presented by Roth et al.