岩石剪切破坏过程的RFPA~(2D)数值模拟

运用岩石破裂与失稳过程分析RFPA2D系统,对岩石剪切破裂过程进行了数值模拟研究。将剪切岩石视为非均匀弹-脆岩石材料,模拟结果再现了岩石剪切滑动形成从变形到破坏直至失稳的全过程,剪断面是滑动形成的主要形式,并首先在试样一端出现,然后再形成由一端及里的剪断面扩展直至另一端最后产生剪断面破坏贯通,形成统一的滑动面,岩石剪切破裂面分形维数还对应着剪断面的粗糙程度和力学行为。

2D Kinetics and Forced Dissociation of Selectin-ligand Bindings

Cell adhesion is crucial to many pathophysiological processes, such as inflammatory reaction and tumor metastasis. It is mediated by specific interactions between receptors and ligands, and provides the physical linkages among cells. For example, interactions between selectins and glycoconjugate ligands mediate leukocyte initially tethering to and subsequently rolling on vascular surfaces in sites of inflammation or injury, which is determined by their fast kinetic rates. To mediate cell adhesion, the interacting receptors and ligands must anchor to apposing surfaces of two cells or a cell and the substratum, i.e. , the so-called two-dimensional (2D) binding, which differs from interactions in the fluid phase, i.e. , the three-dimensional (3D) binding. How structural variations and surface environments of interacting molecules affect their 2D kinetics, and how external forces manipulate their dissociation has little been known quantitatively, and nowadays attracts more and more attentions.

AUTOROTATION OF TWO TANDEM TRIANGULAR CYLINDERS

The autorotation of two tandem triangular cylinders at different gap distances is investigated by numerical simulations. At the Reynolds number of 200， three distinct regimes are observed with the increase of gap distance: namely, angular oscillation, quasi-periodic autorotation and ‘chaotic’ autorotation. For various gap distances, the characteristic of vortex shedding and vortex interaction are discussed. The phase graphs (angular acceleration vs. angular velocity) and the power spectra of moment are analyzed to characterize the motion of the cylinder. The Lyapunov exponent is also calculated to identify the existence of chaos.

Parametric Analysis for Monitoring 2D Kinetics of Receptor-Ligand binding

Thermal fluctuation approach is widely used to monitor association kinetics of surface-bound receptor-ligand interactions. Various protocols such as sliding standard deviation (SD) analysis (SSA) and Page's test analysis (PTA) have been used to estimate two-dimensional (2D) kinetic rates from the time course of displacement of molecular carrier. In the current work, we compared the estimations from both SSA and modified PTA using measured data from an optical trap assay and simulated data from a random number generator. Our results indicated that both SSA and PTA were reliable in estimating 2D kinetic rates. Parametric analysis also demonstrated that such the estimations were sensitive to parameters such as sampling rate, sliding window size, and threshold. These results furthered the understandings in quantifying the biophysics of receptor-ligand interactions.

Sistema BCI mediante imaginación motora para control de movimiento en 2D

Sistema BCI mediante imaginación motora para control de movimiento en 2D