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Background: Circular RNA (circRNA) has been proven to play a critical role in breast cancer progression. Therefore, this study was designed to clarify the role and underlying molecular mechanisms of circ-disintegrin and metalloproteinase 9 (circ-ADAM9) in breast cancer. Methods: A quantitative real-time polymerase chain reaction (RT-qPCR) was conducted to assess the expression levels of circ-ADAM9, microRNA-383-5p (miR-383-5p), and profilin 2 (PFN2). Cellular growth curves of breast cancer cells were determined by colony-forming assay. Cell viability and apoptosis were measured by MTT and flow cytometry, respectively. The protein expression level was analyzed by western blot. Cell migration and invasion were evaluated by wound healing and Transwell assays. A xenograft experiment was established to clarify the functional role of circ-ADAM9 inhibition in vivo. The interactions among circ-ADAM9, miR-383-5p, and PFN2 were analyzed by dual-luciferase reporter, RNA immunoprecipitation (RIP), and RNA pull-down assays. Results: We found that circ-ADAM9 was upregulated in breast cancer tissues and cells compared to controls. Inhibition of circ-ADAM9 expression impaired proliferation, migration, and invasion, but increased radiosensitivity and apoptosis in breast cancer cells; besides, radiotherapy combined with circ-ADAM9 inhibition showed significant inhibitory effects on tumor growth. The functional effects of circ-ADAM9 were related to miR-383-5p, a target of circ-ADAM9. Overexpression of miR-383-5p-mediated malignant behaviors and radiosensitivity of breast cancer cells were dependent on PFN2. Conclusion: Circ-ADAM9 was found to participate in breast cancer progression through targeting the miR-383-5p/PFN2 axis. [ABSTRACT FROM AUTHOR]

It is highly desired yet challenging to obtain analytical approximate solutions to strongly nonlinear oscillators accurately and efficiently. Here we propose a new approach, which combines the homotopy concept with a "residue-regulating" technique to construct a continuous homotopy from an initial guess solution to a high-accuracy analytical approximation of the nonlinear problem, namely the residue-regulating homotopy method (RRHM). In our method, the analytical expression of each order homotopy-series solution is associated with a set of base functions which are preselected or generated during the previous order of approximations, while the corresponding coefficients are solved from deformation equations specified by the nonlinear equation itself and the auxiliary residue functions. The convergence region, rate, and final accuracy of the homotopy are controlled by a residue-regulating vector and an expansion threshold. General procedures of implementing RRHM are demonstrated using the Duffing and Van der Pol–Duffing oscillators, where approximate solutions containing abundant frequency components are successfully obtained, yielding significantly better convergence rate and performance stability compared to the other conventional homotopy-based methods. [ABSTRACT FROM AUTHOR]

Dynamic measurement of femtometer-displacement vibrations in mechanical resonators at microwave frequencies is critical for a number of emerging high-impact technologies including 5G wireless communications and quantum state generation, storage, and transfer. However, the resolution of continuous-wave laser interferometry, the method most commonly used for imaging vibration wavefields, has been limited to vibration amplitudes just below a picometer at several gigahertz. This is insufficient for these technologies since vibration amplitudes precipitously decrease for increasing frequency. Here we present a stroboscopic optical sampling approach for the transduction of coherent super high frequency vibrations. Phase-sensitive absolute displacement detection with a noise floor of 55 fm/√Hz for frequencies up to 12 GHz is demonstrated, achieving higher bandwidth and significantly lower noise floor simultaneously compared to previous work. An acoustic microresonator with resonances above 10 GHz and displacements smaller than 70 fm is measured using the presented method to reveal complex mode superposition, dispersion, and anisotropic propagation. Methods for imaging vibrations in mechanical resonators have been limited to picometer amplitudes and frequencies above 2 GHz. Here, the authors use a stroboscopic optical sampling approach, with simultaneous high bandwidth and low noise-floor, and measure 70 fm displacements out to 12 GHz. [ABSTRACT FROM AUTHOR]