A small water channel network is proposed for designing shallow water fields, and the network is applied to attain water wave cloaking. The design formula is derived from an analogy between waves in a water channel and in an electric circuit; an approach of a transmission line metamaterial is extended to water waves and the water channel is used as an alternative of the transmission line. The size of the water channel is sufficiently smaller than the wavelength and a number of the channels are periodically connected as a network. This small water channel network makes artificial wave fields, and it works for a wide band of frequencies. First, we make an isotropic network equivalent to a shallow water space with constant depth in order to validate the proposed design method. It shows no wave reflection at the interface due to impedance matching. After that, the proposed theory is applied to designing an anisotropic small water channel network for demonstrating shallow water cloaking. A cylinder is cloaked from waves by the network surrounding the cylinder. Both cases are confirmed with numerical computations by solving the boundary-value problem based on linear potential theory.
Arterial repair differences between paclitaxel-coated nitinol drug-eluting stent (DES) vs. bare-metal stent (BMS) up to 1 year after implantation in the superficial femoral artery (SFA) have not been well characterized. We compared angioscopic findings 1 year after implantation in the SFA of 22 DES in 18 patients and 12 BMS in 9 patients (follow-up period 354 ± 49 vs. 383 ± 81 days, P = 0.20). Neointimal coverage (NIC) was graded as: 0, stent struts exposed; 1, struts bulged into the lumen, although covered; 2, struts embedded by the neointima, but translucent; and 3, struts fully embedded and invisible. NIC was defined as heterogeneous when NIC grade variation was ≥1. Presence of thrombus and yellow plaques (YP) was assessed. Baseline patient and lesion characteristics were similar between the groups. In terms of procedural characteristics, stent diameter was smaller in DES than in BMS (6.5 ± 0.5 vs. 7.4 ± 0.8 mm, P = 0.0020). Both DES (grade 2 5 %, grade 3 95 %) and BMS (grade 3 100 %) revealed dominant NIC grades of 2 or 3 (P = 0.46), however, DES showed greater NIC heterogeneity than BMS (91 vs. 42 %, P = 0.004). Both thrombus and YP were more frequently observed in DES than in BMS (64 vs. 17 %, P = 0.001; 95 vs. 67 %, P = 0.042, respectively). In conclusion, although arterial repair was limited after DES implantation in the SFA, it was extensive at 1 year.
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