An effective method for millimeter-wave (mmW) carrier generation from a dual-transverse-mode microsquare laser is experimentally demonstrated. By directly modulating the dual-mode microsquare laser at 6.7 GHz, multiple sidebands are generated due to enhanced modulation nonlinearity, and the lasing modes with an interval of 40 GHz are phase-locked. MmW carriers up to 47 GHz, corresponding to seven times that of the modulation frequency, are achieved with a linewidth below 10 Hz. The single-sideband phase noises of the signals keep the same level after transmission over 2.5 km of optical fiber.
Our previous studies revealed that interstitial fluid (ISF) can flow in the perivascular and adventitial connective tissues along the blood vessels from the extremities to heart and lungs. Here, we aim to clarify the regulatory mechanisms and circulatory pathways of adventitial ISF, which may be a novel systemic circulation distinguished from blood circulation. By fluorescent imaging and speckle tracking velocimetry to record the femoral adventitial ISF, the adventitial ISF flow was found to be regulated by heartbeat and respiration. Under physiological conditions, the ISF flow rate decreased when the heart rate reduced, increased when breath was holding, and a pulsed ISF flow occurred during heavy breathing. During cardiac or respiratory cycle, it was showed that each dilation or contraction of the heart and lungs can generate a to-and-fro motion of the adventitial ISF along the femoral veins. By real-time fluorescent imaging and spectral micro-CT to display the adventitial ISF circulatory pathways, it was found that the heart and lungs work together to regulate the adventitial ISF to flow centripetally along the major arteries and veins of the systemic vasculature into the myocardium, then into the lungs via the pulmonary arteries and return to the heart via the pulmonary veins, forming an adventitial ISF circulation. Functionally, the adventitial ISF circulatory pathway is a promising novel route for organ-targeted extravascular drug delivery.
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