A Radio Frequency Non-reciprocal Network Based on Switched Low-loss Acoustic Delay Lines

This work demonstrates the first non-reciprocal network based on switched low-loss acoustic delay lines. A 21 dB non-reciprocal contrast between insertion loss (IL=6.7 dB) and isolation (28.3 dB) has been achieved over a fractional bandwidth of 8.8% at a center frequency 155MHz, using a record low switching frequency of 877.22 kHz. The 4-port circulator is built upon a newly reported framework by the authors, but using two in-house fabricated low-loss, wide-band lithium niobate (LiNbO3) delay lines with single-phase unidirectional transducers (SPUDT) and commercial available switches. Such a system can potentially lead to future wide-band, low-loss chip-scale nonreciprocal RF systems with unprecedented programmability.Comment: 4 pages, 7 figure

Phylogenetic delineation of regional biota: A case study of the Chinese flora

Biogeographical regionalization schemes have traditionally been constructed based on taxonomic endemism of families, genera, and/or species, and rarely incorporated the phylogenetic relationships between taxa. However, phylogenetic relationships are important for understanding historical connections within and among biogeographical regions. Phylogeny-based delineation of biota is a burgeoning and fruitful field that is expected to provide novel insights into the conservation of regional diversity and the evolutionary history of biota. Using the Chinese flora as an example, we compared regionalization schemes that were based on: (1) taxonomic endemism, (2) taxonomic dissimilarly, and (3) phylogenetic dissimilarly. Our results revealed general consistency among different regionalization schemes and demonstrated that the phylogenetic dissimilarly approach is preferable for biogeographical regionalization studies. Using the phylogenetic dissimilarly approach, we identified five phytogeographical regions within China: the Paleotropic, Holarctic, East Asiatic, Tethyan, and Qinghai-Tibet Plateau Regions. The relationship of these regions was inferred to be: (Paleotropic, ((East Asiatic + Holarctic) + (Tethyan + Qinghai-Tibet Plateau))