The purpose of this study was to determine the effect of extremely low frequency and weak magnetic fields (WMF) on cardiac myocyte Ca(2+) transients, and to explore the involvement of potassium channels under the WMF effect. In addition, we aimed to find a physical explanation for the effect of WMF on cardiac myocyte Ca(2+) transients. Indo-1 loaded cells, which were exposed to a WMF at 16 Hz and 40 nT, demonstrated a 75 ± 4% reduction in cytosolic Ca(2+) transients versus control. Treatment with the K(ATP) channel blocker, glibenclamide, followed by WMF at 16 Hz exposure, blocked the reduction in cytosolic calcium transients while treatment with pinacidil, a K(ATP) channel opener, or chromanol 293B, a selective potassium channel blocker of the delayed rectifier K(+) channels, did not inhibit the effect. Based on these finding and the ion cyclotron resonance frequency theory, we further investigated the effect of WMF by changing the direct current (DC) magnetic field (B(0) ). When operating different DC magnetic fields we showed that the WMF value changed correspondingly: for B(0)  = 44.5 µT, the effect was observed at 17.05 Hz; for B(0)  = 46.5 µT, the effect was observed at 18.15 Hz; and for B(0)  = 49 µT the effect was observed at 19.1 Hz. We can conclude that the effect of WMF on Ca(2+) transients depends on the DC magnetic field level.

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A compact, broadband double‐slot waveguide antenna is presented. The present design is an improvement of another double‐slot waveguide radiator proposed earlier by the authors. The antenna is characterized by high efficiency and moderate (less than 2.5:1) VSWR in more than 38% frequency band.

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