No abstract

Osteocytes are mechanosensitive bone cells, but little is known about their effects on tumor cells in response to mechanical stimulation. We treated breast cancer cells with osteocyte-derived conditioned medium (CM) and fluid flow-treated conditioned medium (FFCM) with 0.25 Pa and 1 Pa shear stress. Notably, CM and FFCM at 0.25 Pa induced the mesenchymal-to-epithelial transition (MET), but FFCM at 1 Pa induced the epithelial-to-mesenchymal transition (EMT). This suggested that the effects of fluid flow on conditioned media depend on flow intensity. Fluorescence resonance energy transfer (FRET)-based evaluation of Src activity and vinculin molecular force showed that osteopontin was involved in EMT and MET switching. A mouse model of tumorinduced osteolysis was tested using dynamic tibia loadings of 1, 2, and 5 N. The low 1 N loading suppressed tumor-induced osteolysis, but this beneficial effect was lost and reversed with loads at 2 and 5 N, respectively. Changing the loading intensities in vivo also led to changes in serum TGFβ levels and the composition of tumor-associated volatile organic compounds in the urine. Collectively, this study demonstrated the critical role of intensity-dependent mechanotransduction and osteopontin in tumorosteocyte communication, indicating that a biophysical factor can tangibly alter the behaviors of tumor cells in the bone microenvironment.

No abstract

Bone is a mechanosensitive tissue that adapts its mass, architecture and mechanical properties to external loading. Appropriate mechanical loads offer an effective means to stimulate bone remodeling and prevent bone loss. A role of in situ strain in bone is considered essential in enhancement of bone formation, and establishing a quantitative relationship between 3D strain distributions and a rate of local bone formation is important. Digital speckle pattern interferometry (DSPI) can achieve whole-field, non-contacting measurements of microscopic deformation for highresolution determination of 3D strain distributions. However, the current system does not allow us to derive accurate strain distributions because of complex surface contours inherent to biological samples. Through development of a custom-made piezoelectric loading device as well as a new DSPIbased force calibration system, we built an advanced DSPI system and integrated local contour information to deformation data. Using a mouse femur in response to a knee loading modality as a model system, we determined 3D strain distributions and discussed effectiveness and limitations of the described system. KeywordsBone strain; digital speckle pattern interferometry (DSPI); ESPI; mechanical loading; deformation and contour information

This paper describes full-field, three-dimensional, non-contact measurements of displacement and strain under high temperature condition based on digital image correlation (DIC). To conduct DIC measurements at high temperatures, two important factors need to be considered:(1) the ability of the coating to resist heat and withstand deformation without cracking or peeling off; (2) the radiation from the specimen's surface at high temperature. This paper proposes a solution to both of the most important issues in high temperature DIC measurement. First, different coating materials were investigated, and a procedure to generate a necessary speckle pattern required by DIC to resist heat and withstand deformation at high temperature has been developed. Second, a monochromatic illumination system in combination with a filter set has been studied to eliminate the radiation effect. A DIC system which enables a high temperature displacement and strain measurement up to 1100 • C is presented and demonstrated by experimental measurements.

No abstract

This paper presents a simple spatial phase shift shearography based on the Michelson interferometer. The Michelson interferometer based shearographic system has been widely utilized in industry as a practical nondestructive test tool. In the system, the Michelson interferometer is used as a shearing device to generate a shearing distance by tilting a small angle in one of the two mirrors. In fact, tilting the mirror in the Michelson interferometer also generates spatial frequency shift. Based on this feature, we introduce a simple Michelson interferometer based spatial phase shift shearography. The Fourier transform (FT) method is applied to separate the spectrum on the spatial frequency domain. The phase change due to the loading can be evaluated using a properly selected windowed inverse-FT. This system can generate a phase map of shearography by using only a single image. The effects of shearing angle, spatial resolution of couple charge device camera, and filter methods are discussed in detail. The theory and the experimental results are presented.

The main applications of temporal phase shift shearography are in NDT and strain measurement. Temporal Phase Shift Shearography for NDTThe most important application of temporal phase shift shearography, called digital shearography for simplicity, is for NDT, which enables flaws in objects/ materials to be found without damaging them. Compared to conventional NDT methods, such as ultrasonic, radiographic, magnetic article, dye penetrant, eddy current, and acoustic emission methods, digital shearography has the advantages of full-field measurement, high sensitivity, easy visualization, quick measurement speed, and real-time display of test results. Due to these distinct advantages, digital shearography has been widely accepted by the automotive and aerospace industries as a recommended NDT method for rubber and composite materials.1-2 The details of digital shearography for NDT have been described and discussed in Refs. 3 and 4. In this section, potentials and limitations of temporal phase shift shearography for NDT are reviewed, practical applications using different loading methods are demonstrated, and a few recent developments, such as NDT for testing relatively large objects and for measuring mirror-like surfaces, are presented and discussed.