The mechanical characterization of brain tissue at high loading velocities is vital for understanding and modeling Traumatic Brain Injury (TBI). The most severe form of TBI is diffuse axonal injury (DAI) which involves damage to individual nerve cells (neurons). DAI in animals and humans occurs at strains > 10% and strain rates > 10/s. The mechanical properties of brain tissues at these strains and strain rates are of particular significance, as they can be used in finite element human head models to accurately predict brain injuries under different impact conditions. Existing conventional tensile testing machines can only achieve maximum loading velocities of 500 mm/min, whereas the Kolsky bar apparatus is more suitable for strain rates > 100/s. In this study, a custom-designed high rate tension device is developed and calibrated to estimate the mechanical properties of brain tissue in tension at strain rates < 90/s, while maintaining a uniform velocity. The range of strain can also be extended to 100% depending on the thickness of a sample. The same apparatus can be used to characterize the dynamic behavior of skin and other soft biological tissues by using appropriately sized load cells with a capacity of 10 N and above.
Princeton University（普林斯顿大学）；Max Planck Institute for the Physics of Complex Systems（马克斯·普朗克复杂系统物理研究所）；Max Planck Institute of Molecular Cell Biology and Genetics（马克斯·普朗克分子细胞生物学与遗传学研究所）；Center for Systems Biology Dresden（德累斯顿系统生物学中心）；University of California, Santa Barbara（加州大学圣塔芭芭拉分校）
Shape-tension coupling produces nematic order in an epithelium vertex model
Rudolf Peierls Centre For Theoretical Physics, University of Oxford（鲁道夫·派尔斯理论物理中心，牛津大学）；School of Science and Engineering, University of Dundee（邓迪大学科学与工程学部）；School of Life Sciences, University of Dundee（邓迪大学生命科学学部）
Max Planck Institute for the Physics of Complex Systems（马克斯·普朗克复杂系统物理研究所）；Max Planck Institute of Molecular Cell Biology and Genetics（马克斯·普朗克分子细胞生物学与遗传学研究所）；Center for Systems Biology Dresden（德累斯顿系统生物学中心）
Mechanical Stress Inference for Two Dimensional Cell Arrays
许多形态发生过程涉及上皮组织的机械重排，其由精确调节的细胞骨架力和细胞黏附驱动。细胞的机械状态和细胞间粘附不仅是调控的目标，而且本身可能是协调发育过程的信号。然而，因为难以在亚细胞尺度上直接测量机械应力{ \it in vivo}，所以对发育机制的作用知之甚少。在这里，我们提出了一种替代方法，利用最近的进展，在现场成像的形态发生过程，并使用计算分析的高分辨率图像的上皮组织，以推断细胞内和细胞之间的相对大小的力量。我们模拟细胞内的压力和界面张力，允许这些参数从细胞到细胞，从接口到接口。假设上皮细胞层接近机械平衡，我们使用观察到的二维细胞阵列的几何形状来推断界面张力和细胞内压力。在这里，我们提出了建议的机械逆方法的数学公式，并将其应用于分析的上皮细胞层观察到的腹侧沟形成在{ \it果蝇}胚胎和毛细胞的过程中确定在鸟类耳蜗。分析揭示了前一过程中的力学各向异性和后一过程中与细胞分化相关的力学异质性。该方法为细胞和组织力学模型的定量和详细的实验测试开辟了一条道路。
Contact inhibition of locomotion and mechanical cross-talk between cell-cell and cell-substrate adhesion determines the pattern of junctional tension in epithelial cell aggregates
