Corneal epithelial permeability: Ethnic differences between Asians and non-Asians

PurposeTo ascertain whether a difference in the permeability of the corneal epithelium to fluorescein (P_dc) exists between Asians and non-Asians.MethodsFrom a multi-study database we extracted 632 records of baseline, open-eye P_dc measurements taken on both eyes of 176 subjects. Subjects were awake for a minimum of 4 h before measurement, and were free of ocular disease and central corneal staining. P_dc was transformed by natural logarithm to better approximate normality for statistical tests.ResultsThe mean ln(P_dc) in the Asian group was significantly greater than in the non-Asian group [−2.34 ln(nm/s) vs. −2.58 ln(nm/s); p < 0.001].ConclusionsCompared with non-Asians, Asians exhibited a less negative ln(P_dc), which translates to a higher P_dc and a more permeable corneal epithelium. We speculate that this may be related to anatomic differences responsible for greater eyelid tension in Asians.     

雪菊醇提物对糖尿病气阴两虚证候细胞代谢物的影响

目的研究雪菊醇提物对体外诱导气阴两虚证候细胞代谢物的影响。方法噻唑蓝实验检测细胞毒性;采用核磁共振(nuclear magnetic resonance,NMR)代谢组学方法检测证候细胞裂解液和细胞培养上清液中内源性代谢物变化;用多元统计分析差异性代谢物与通路的变化。结果建立糖尿病气阴两虚证候细胞模型,雪菊醇提物干预后改善了细胞生长活力。代谢组学结果显示:本实验的所有样本点都分布在95%的置信区间内(即散点图的4个区域中),聚类分布显著,且可信度较高。代谢物分析发现与正常组相比,证候细胞模型组的异亮氨酸、亮氨酸、α-葡萄糖和琥珀酸的含量显著上升(P0.05或P0.01),果糖含量显著下调(P0.05);与证候细胞模型组相比,雪菊醇提物组的脂肪酸、脯氨酸、甘油磷酯酰胆碱、抗坏血酸、α-葡萄糖含量显著下调(P0.05或P0.01)。差异性代谢物主要涉及氨基酸代谢途径、丙酮酸代谢途径及乙醛酸盐和二羧酸盐代谢途径。结论采用代谢组学技术进行全面、整体性的分析雪菊醇提物对糖尿病气阴两虚证细胞内代谢物的影响,为雪菊降低不同证候糖尿病的药用性功效提供基础理论依据。     

Entropy-Controlled Artificial Anisotropic Diffusion for the Numerical Solution of Conservation Laws Based on Algorithms from Image Processing

In image processing are nonlinear anisotropic diffusion filters used to construct suitable filter algorithms for denoising, edge enhancement, and edge detection. We applied a nonlinear anisotropic diffusion operator in the context of the numerical solution of a scalar hyperbolic conservation law. It turns out that algorithms currently used in image processing are very well suited for the design of nonlinear higher-order dissipative terms. In particular we stabilize a central scheme, known for its oscillatory behavior, by the construction of a nonlinear diffusion term. This means constructing a diffusion matrix consisting of eigenvectors parallel and perpendicular to discontinuities and eigenvalues denoting the amount of dissipation depending on the local strength of the gradients. These directions are used to steer the amount of dissipation, which means suppressing diffusion across the shock front and using the perpendicular direction to enable the necessary diffusion to stabilize the underlying second-order scheme. This new approach allows a multidimensional view to the concept of artificial dissipation. We take the concept of entropy production in the vicinity of shock regions as an indicator for the steering of the diffusion matrix. In smooth regions, which obey an entropy equality instead of an entropy inequality, no information about the diffusion direction and strength is needed. So we add as a stabilizing term diffusion parallel to the characteristics, which turns out to be the Lax–Wendroff diffusion rate. In the case of unsteady regions we use the entropy production to blend between this diffusion term and an—still second-order—extra diffusion term with diffusion parallel to the gradient of the entropy production.