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© Copyright: 2015 Magbanua et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source

This paper intends to show that the low-amplitude effects, in particular the attenuation proportional to the frequency from very low frequencies up to the kilohertz range, are connected with the motion of dislocations in cracks. The measurements have been made of the resonant frequencies and the internal friction of spherical rock speciments, including Solenhofen limestone, Indiana limestone, Westerley Granite, Friedensville sphalerite, galena, magnetite, and olivine of small grain sizes. The different types of stresses are thus easily determined through the various modes of motion. On the basis of dislocation motion in cracks, it is shown that the ratio of the radial Q to the torsional Q is about 0.8 and is nearly independent of the crystal structure. This result is in agreement with the measurements, which vary from about 0.6 to 0.9. From longitudinal and torsional measurements of cylinders, the torsional Q's are nearly twice those for the longitudinal mode. The model used also agrees with the variation of velocity and Q with the external pressure. [ABSTRACT FROM AUTHOR]

By using the resonant vibrations of metal spheres it is possible to separate the contributions involving different amounts of shear, hydrostatic, and longitudinal strain merely by choosing the appropriate resonant frequencies. Birch [J. Geophys. Res. 80, 756-764 (1975)] has applied this method to the radical, spheriodal, and torsional modes of metals, glasses, and rocks. He has shown that if there is no loss connected with the hydrostatic component of vibration, the ratio of the Q of the radial mode to the Q of the torsional modes should be 9 to 1 whereas his measurements of steel indicated a ratio of about 3 to 1. We have measured several cubic metals (Al, Fe, Ta, Nb, W, V, and α-brass) and have found that this ratio of Q's varies systematically with elastic anisotrophy. It is shown that the difference in the elastic constants of adjacent grains introduces a shearing stress in the body of the material which adds a component of the internal friction proportional to the anisotropic factor minus one which accounts for the drop in Q for a longitudinal vibration. For the radical mode the much larger effect has not been explained and the value of K found is experimental. [ABSTRACT FROM AUTHOR]

The pre-stack Kirchhoff migration is implemented for delivering wavelet stretch-free imaged data, if the migration is (ideally) limited to the wavelet corresponding to a target horizon. Avoiding wavelet stretch provides long-offset imaged data, far beyond what is reached in conventional migration and results in images from the target with improved vertical and lateral resolution and angular illumination. Increasing the range of imaged offsets also increases the sensitivity to event-crossing, velocity errors and anisotropy. These issues must be addressed to fully achieve the greatest potential of this technique. These ideas are further illustrated with a land survey seismic data application in Texas, U.S.

Size selection via filtration offers an antigen-independent approach for the enrichment of rare cell populations in blood of cancer patients. We evaluated the performance of a novel approach for multiplex rare cell detection in blood samples from metastatic breast (n = 19) and lung cancer patients (n = 21), and healthy controls (n = 30) using an automated microfluidic filtration and multiplex immunoassay strategy. Captured cells were enumerated after sequential staining for specific markers to identify circulating tumor cells (CTCs), circulating mesenchymal cells (CMCs), putative circulating stem cells (CSCs), and circulating endothelial cells (CECs). Preclinical validation experiments using cancer cells spiked into healthy blood demonstrated high recovery rate (mean = 85%) and reproducibility of the assay. In clinical studies, CTCs and CMCs were detected in 35% and 58% of cancer patients, respectively, and were largely absent from healthy controls (3%, p = 0.001). Mean levels of CTCs were significantly higher in breast than in lung cancer patients (p = 0.03). Fifty-three percent (53%) of cancer patients harbored putative CSCs, while none were detectable in healthy controls (p<0.0001). In contrast, CECs were observed in both cancer and control groups. Direct comparison of CellSearch® vs. our microfluidic filter method revealed moderate correlation (R2 = 0.46, kappa = 0.47). Serial blood analysis in breast cancer patients demonstrated the feasibility of monitoring circulating rare cell populations over time. Simultaneous assessment of CTCs, CMCs, CSCs and CECs may provide new tools to study mechanisms of disease progression and treatment response/resistance.