Non-Destructive Inspection of Concrete Structures Using an Acceleration Pickup
The present paper proposes a method for detecting cracks or honeycombs in concrete structures using an acceleration pickup. The sensor on the concrete surface observes the stationary waves which are generated inside the structures depending on the depth of the crack (if there is a crack) or the bottom of the structure (if there are no cracks or honeycombs). The method measures the depths of the reflection planes (such as cracks or honeycombs) accurately by modeling the sensor output as an output of a linear dynamic system with unknown parameters and by applying a maximum likelihood method. The method is shown to be quite effectively applied to measure the depths of cracks and honeycombs
Fabrication of the micro-gripper with a force sensor for manipulating a cell
A novel micro-gripper has been designed and fabricated to manipulate the small object like a cell. In order to gripping the cell, it should be no restriction to use the micro-gripper in the water. Since the mechanical type micro-gripper is little affected by a surrounding so as to use freely in any environment, compared with other type micro-grippers, it is suitable to treat the cell. In addition, it can reduce the deformation of the cell and control the gripping force flexibly. A point to be considered to manipulate the cell is the force working on the cell and the deformation of the cell according to the applied force. On the gripper a piezo-resistive sensor is integrated for sensing the gripping force. Using the fabricated micro-gripper, micro-glass beads can be successfully manipulated in the water. The resistor of the piezoresistive sensor is successfully changed according to the force on the micro-gripper. If on-going feedback experiment in the gripper system is finished successfully, the proposed micro-gripper can be utilized for manipulating the cell
Mechanical and failure properties of single attached cells under compression.
Eukaryotic cells are continuously subjected to mechanical forces under normal physiological conditions. These forces and associated cellular deformations induce a variety of biological processes. The degree of deformation depends on the mechanical properties of the cell. As most cells are anchorage dependent for normal functioning, it is important to study the mechanical properties of cells in their attached configuration. The goal of the present study was to obtain the mechanical and failure properties of attached cells. Individual, attached C2C12 mouse myoblasts were subjected to unconfined compression experiments using a recently developed loading device. The device allows global compression of the cell until cell rupture and simultaneously measures the associated forces. Cell bursting was characterized by a typical reduction in the force, referred to as the bursting force. Mean bursting forces were calculated as 8.7+/-2.5 microN at an axial strain of 72+/-4%. Visualization of the cell using confocal microscopy revealed that cell bursting was preceded by the formation of bulges at the cell membrane, which eventually led to rupturing of the cell membrane. Finite element calculations were performed to simulate the obtained force-deformation curves. A finite element mesh was built for each cell to account for its specific geometrical features. Using an axisymmetric approximation of the cell geometry, and a Neo-Hookean constitutive model, excellent agreement between predicted and measured force-deformation curves was obtained, yielding an average Young's modulus of 1.14+/-0.32 kPa.