Browsing by Subject "Excitation"

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    One-way reciprocal spoof surface plasmons and relevant reversible diodelike beaming
    (American Physical Society, 2013-05-15) Mutlu, M.; Cakmakyapan, S.; Serebryannikov, A. E.; Özbay, Ekmel
    One - way excitation of spoof surface plasmons (SPs) and strongly pronounced diodelike extraordinary transmission of linearly polarized waves in the beaming regime can be obtained by combining spoof SPs and cross-polarization conversion resonances. The reciprocal composite structure that is suggested to realize this mechanism consists of a symmetric metallic grating with a subwavelength slit and a metamaterial based ultrathin 90 degrees polarization rotator and, therefore, shows the broken spatial inversion symmetry. In contrast to the earlier studies of SP inspired transmission through subwavelength slits, asymmetric (one-way) beaming is demonstrated at normal incidence and for both s- and p-polarized incident waves. Furthermore, as an implication of Lorentz reciprocity, the studied diodelike mechanism is reversible, which manifests itself in that transmission is significant for one of the two opposite illumination directions at s polarization and for the other direction at p polarization. The obtained numerical and experimental results verify the general idea and enable us to select the optimal operation regimes.
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    Selective Hg(II) sensing with improved stokes shift by coupling the internal charge transfer process to excitation energy transfer
    (American Chemical Society, 2010) Atilgan, S.; Ozdemir, T.; Akkaya, E. U.
    Versatile chemistry of the Bodipy chromophore allows modular assembly of an excitation energy donor, acceptor, and a cation selective ligand in just a couple of steps. The new approach should be applicable in other designs which target molecular sensors with large Stokes shifts and red to near IR emission.
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    ItemOpen Access
    Spectrally selective imaging with wideband balanced steady-state free precession MRI
    (John Wiley and Sons Inc., 2016) Çukur, Tolga
    Purpose Unwanted, bright fat signals in balanced steady-state free precession sequences are commonly suppressed using spectral shaping. Here, a new spectral-shaping method is proposed to significantly improve the uniformity of stopband suppression without compromising the level of passband signals. Methods The proposed method combines binomial-pattern excitation pulses with a wideband balanced steady-state free precession sequence kernel. It thereby increases the frequency separation between the centers of pass and stopbands by π radians, enabling improved water-fat contrast. Simulations were performed to find the optimal flip angles and subpulse spacing for the binomial pulses that maximize contrast and signal efficiency. Results Comparisons with a conventional binomial balanced steady-state free precession sequence were performed in simulations as well as phantom and in vivo experiments at 1.5 T and 3 T. Enhanced fat suppression is demonstrated in vivo with an average improvement of 58% in blood-fat and 68% in muscle-fat contrast (P < 0.001, Wilcoxon signed-rank test). Conclusion The proposed binomial wideband balanced steady-state free precession method is a promising candidate for spectrally selective imaging with enhanced reliability against field inhomogeneities.