Obesity is associated with impaired endothelial function assessed as flow-mediated vasodilation (FMD), the procedure of which involves transient brachial artery occlusion and following reactive hyperemia. Acute aerobic exercise can improve FMD. This study examined the effects of repeated FMD procedures and acute aerobic exercise on FMD in obese young men. Upper arm cuff inflation of 200 mmHg for 5 min and subsequent deflation was induced at 0, 1 and 2 h to examine effects of repeated FMD procedures on FMD in obese subjects, as well as in lean controls. To observe the combined effects of FMD procedures and acute exercise on FMD in obese subjects, 45 min moderate exercise was performed immediately after FMD procedure at 0 h, with the procedure repeated at 1 and 2 h. The results showed that, after repeated FMD procedures, FMD in obese subjects increased from 5.9 +/- 4.0% to 6.5 +/- 3.2% and 8.4 +/- 2.8% (P = 0.017), whereas FMD demonstrated no changes in lean controls (P = 0.90). After repeated FMD procedures and exercise, FMD in the obese subjects increased from 7.3 +/- 3.5% to 9.5 +/- 4.0% and 11.0 +/- 4.3% (P = 0.0004). The present findings demonstrate that both repeated FMD procedures and acute aerobic exercise improve FMD in obese subjects.

We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating (TFBG) for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber (SMF) and reduced-diameter SMF with the same tilt angle, and then excites two sets of superposed spectral combs of cladding modes. The cascaded TFBG with total length of 18 mm has a much wider wavelength range over 100 nm and narrower wavelength separation than that of a TFBG only in the SMF, enabling an enlarged range and a higher accuracy of refractive index measurement. The fabricated TFBG with the merits of enhanced sensing capability and temperature self-calibration presents great potentials in the biochemical sensing applications.

We achieve Fano-like resonances in an all-in-fiber structure embedded with an in-line Mach-Zehnder interferometer (MZI). A fiber Bragg grating is inserted into MZI's one arm to form a resonance, which functions as the discrete state of the Fano-like resonance to couple with the continuum propagating mode of MZI in the fiber core. A theoretical model predicts the controllable resonance lineshape by changing the phase difference between the MZI's two interference pathways. Fano-like resonances with an extinction ratio over 20 dB are experimentally observed, which are reliably tuned into Lorentzian and electromagnetically induced transparency-like resonances by versatile methods. The realization of Fano-like resonances with broad tunability in this all-in-fiber structure holds potentials in fiber-based applications of sensing, signal processing and nonlinear optics.

We report the autofocusing behaviors of ring Airy beams (RABs) embedded with two kinds of off-axial vortex singularities. The influences of embedded positions and topological charges of point and r vortices on the autofocusing dynamic are numerically and experimentally investigated. The results show that, for the first-order vortex, the embedded position significantly affects the focal field, and once the singularity is located on the main ring of RAB, the symmetric Bessel profile of the focal field will be broken, otherwise the Bessel-like focus can self-heal at the focal plane. However, for the higher-order vortex embedded near the main ring, it will split into several fundamental vortices and then separate with each other along the radial direction under the interaction with the RAB background. Our results hold potential for the practical application of RABs in the atmosphere and other propagation systems with perturbation and even singularities.

No abstract