Sensors based on evanescent field perturbation of microresonators.

We consider a whispering gallery mode (WGM) sensor where a dielectric perturber extends into the evanescent tail of the microresonator. The position of the perturber rather than the morphology of the resonator is modified by a change in the measured property, inducing a shift in the WGM. This approach can be used for both three-dimensional (spheres, toroids) and planar (disks, rings) resonator geometries. We demonstrate, through analysis and experiments, the feasibility of this sensor approach for both geometries by using a sphere resonator and an on-chip ring resonator. Experiments show that the motion of the perturber across the evanescent tail on the resonator's outer surface leads to a measurable shift in the resonator WGM. In the latter experiment, a ferromagnetic structure is attached to the perturber stem so that the system acts as a magnetic field detector. The results show a consistent relationship between the mode shift and the magnetic field strength.

Experimental Insight into the Hemodynamics and Perfusion of Radiological Contrast in Patent and Non-patent Aortic Dissection Models.

PURPOSE: In a curved vessel such as the aortic arch, the velocity profile closer to the aortic root is normally skewed towards the inner curvature wall, while further downstream along the curve, the velocity profile becomes skewed towards the outer wall. In an aortic dissection (AD) disease, blood velocities in the true lumen (TL) and false lumen (FL) are hypothesized to depend on the proximity of the entry tear to the root of aortic arch. Faster velocity in the FL can lead to higher hemodynamic loading, and pose tearing risk. Furthermore, the luminal velocities control the perfusion rate of radiological contrast media during diagnostic imaging. The objective in this study is to investigate the effect of AD disease morphology and configuration on the blood velocity field in the TL and FL, and on the relative perfusion of radiological enhancement agents through the dissection. METHODS: Eight in vitro models were studied, including patent and non-patent FL configurations. Particle image velocimetry (PIV) was used to quantify the AD velocity field, while laser-induced fluorescence (LIF) was implemented to visualize dynamical flow phenomena and to quantify the perfusion of injected dye, in mimicry of contrast-enhanced computed tomography (CT). RESULTS: The location of the proximal entry tear along the aortic arch in a patent FL had a dramatic impact on whether the blood velocity was higher in the TL or FL. The luminal velocities were dependent on the entry/reentry tear size combination, with the smaller tear (whether distal or proximal) setting the upper limit on the maximal flow velocity in the FL. Upon merging near the distal reentry tear, the TL/FL velocity differential gave rise to the roll up and shedding of shear layer vortices that convected downstream in close proximity to the wall of the non-dissected aorta. In a non-patent FL, the flow velocity was practically null with all the blood passing through the TL. LIF imaging showed much slower perfusion of contrast dye in the FL compared to the TL. In a patent FL, however, dye had a comparable perfusion rate appearing around the same time as in the TL. CONCLUSIONS: Blood velocities in the TL and FL were highly sensitive to the exact dissection configuration. Geometric case A1R, which had its proximal entry tear located further downstream along the aortic arch, and had its entry and reentry tears sufficiently sized, exhibited the highest FL flow velocity among the tested models, and it was also higher than in the TL, which suggest that this configuration had elevated hemodynamic loading and risk for tearing. In contrast-enhanced diagnostic imaging, a time-delayed acquisition protocol is recommended to improve the detection of suspected cases with a non-patent FL.

Percutaneous coronary intervention increases leptin and decreases adiponectin levels.

OBJECTIVE: The study was designed to examine the effect of percutaneous coronary intervention (PCI) on adiponectin and leptin levels. We have previously demonstrated that PCI triggers a systemic inflammatory response. We hypothesized that inflammation participates in the pathogenesis of diabetes mellitus and the metabolic syndrome by modulating levels of adiponectin and leptin. DESIGN: Prospective study in which inflammation was induced by PCI. PATIENTS: Forty-eight patients with stable coronary artery disease and without diabetes mellitus. MEASUREMENTS: High-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), leptin and adiponectin were measured at baseline and 48 h after the procedure. RESULTS: Following PCI, hs-CRP increased by 211%, IL-6 by 87% and leptin by 19%, while adiponectin decreased by 14% (P < 0.001 for all). The change in IL-6 correlated with that in hs-CRP (rho = 0.32; P = 0.027), as did the changes in IL-6 and leptin (rho = 0.31; P = 0.03). The change in adiponectin, however, did not correlate with the change in any of the other markers. CONCLUSION: This study demonstrates that PCI affects the levels of adiponectin and leptin within 48 h. These effects may be secondary to the inflammatory response triggered by PCI.