21.9-Gb/s PDM-OFDM Transmission With 2-b/s/Hz Spectral Efficiency Over 1000 km of SSMF

Abstract-We discuss optical multi-band orthogonal frequency division multiplexing (OFDM) and show that by using multiple parallel OFDM bands, the required bandwidth of the digital-to-analogue/ analogue-to-digital converters and the required cyclic prefix can significantly be reduced. With the help of four OFDM bands and polarization division multiplexing (PDM) we report continuously detectable transmission of 10 121.9-Gb/s (112.6-Gb/s without OFDM overhead) at 50-GHz channel spacing over 1,000-km standard single mode fiber (SSMF) without any inline dispersion compensation. In this experiment 8 QAM subcarrier modulation is used which confines the spectrum of the 121.9 Gb/s PDM-OFDM signal within a 22.8 GHz optical bandwidth. Moreover, we propose a digital signal processing method to reduce the matching requirements for the wideband transmitter IQ mixer structures required for PDM-OFDM. Index Terms-Chromatic dispersion compensation, fiber-optic transmission systems, long-haul transmission, orthogonal frequency-division multiplexing (OFDM)

Phylogeography of White-Spotted Charr (Salvelinus leucomaenis) Inferred from Mitochondrial DNA Sequences

The white-spotted charr (Salvelinus leucomaenis) is a coldwater-adapted fish distributed in far-eastern Asia. To assess phylogeographic patterns of this species over most of its range in the Japanese archipelago and Sakhalin Island, Russia, we examined nucleotide sequences of the mitochondrial DNA (mtDNA) cytochrome b region (557 bp) in 141 individuals from 50 populations. A total of 33 (5.5%) nucleotide positions were polymorphic and defined 29 haplotypes. Phylogenetic analysis assigned the observed haplotypes to four main clades, which were characterized by the idiosyncrasies and discontinuity of geographic distributions. The nested clade analyses revealed that the geographical distribution patterns of some haplotypes and clades were explained by historical event such as past fragmentation. Although substantial genetic differentiation was found among the four main clades, their geographic distributions overlapped extensively in several regions. Since white-spotted charr can potentially use both freshwater and marine environments, coexistence among different lineages can be attributed to secondary contact through range expansion by migratory individuals during multiple glacial periods after interglacial isolation. Finally, our data demonstrate that the current subspecies designation does not reflect the phylogeography of this species based on mtDNA analysis. Hierarchical analysis (AMOVA) also showed that genetic variation was far more pronounced within subspecies than among subspecies (i.e., among discrete regions). These results suggest that each population, rather than each subspecies, must be treated as an evolutionarily significant unit

Clinical performance of polymer-coated paclitaxel-eluting stent implanted for diffuse and calcified superficial femoral artery stenotic lesions: Insights from a patient on hemodialysis

In recent years, various devices have been approved for peripheral artery disease with femoropopliteal lesions. However, treatment of long, calcified, and diffused lesions is still challenging because these lesions are associated with restenosis. This report described the case of an 82-year-old man with bilateral severely calcified and diffused long lesions in the superficial femoral artery that was treated using polymer-coated paclitaxel-eluting stent and interwoven nitinol stent. After 6 months, in-stent restenosis was observed at the implantation site of the interwoven nitinol stents. Polymer-coated paclitaxel-eluting stents were deployed at the in-stent restenosis site. After another 6 months, angiography and intravascular ultrasound imaging revealed no restenosis at the polymer-coated paclitaxel-eluting stent site. Optical coherence tomography was also performed, revealing that the stent struts were well covered by neointima, which was very thin at approximately 0.1 mm. This representative case demonstrated substantial differences in the effects of devices; in other words, the superiority of polymer-coated paclitaxel-eluting stent in treating long, diffuse, and calcified lesions indicated that its implantation is a reasonable option when the initial gain was obtained following sufficient vessel preparation