Design of Dual-band Branch-Line Coupler Based on Shunt Open-Circuit DCRLH Cells

In this article, the shunt open-circuit dual composite right/left-handed (DCRLH) cell is initially proposed and one dual-band branch-line coupler based on the proposed cells is designed. It is found that, compared with DCRLH cell, the frequency selectivity, matching condition and adjustment range of the shunt open-circuit DCRLH cell improve greatly. Moreover, the shunt open-circuit DCRLH cell exhibits two adjustable frequency points with -90degrees phase shift within its first two passbands. In order to explore this exotic property effectively, the influence of the primary geometrical parameter is investigated through parametric analysis. Thus, one dual-band branch-line coupler based on the shunt open-circuit DCRLH cells is designed. Both simulated and measured results indicate that comparative performance is achieved. Different from part of previous dual-band branch line couplers, for the proposed coupler, the signs of phase difference of two output ports within the two operating frequency bands are identical with each other. This branch-line coupler is quite suitable for the application which is sensitive to the variation of phase difference and its effective area is compact

Isolation of phloem specific gene promoters for use in genetic engineering of insect resistance in rice

Towards the aim of producing transgenic rice with enhanced resistance to one of its phloem sap-sucking insect pests, the brown planthopper (BPH), two potential phloem-specific promoters, of the rice sucrose synthase-1 (RSsl) and the cucurbit phloem protein PP2 genes, were isolated and investigated. Using a PGR fragment of the maize sucrose synthase-1 (Shi) gene, genomic clones containing the RSsl and RSs2 (rice sucrose synthase-2) genes were isolated from a genomic library of rice (Oryza sativa L. Japonica) and characterised. A full- length RSsl gene from one of the genomic clones was sequenced, including 1756 bp of 5'-flanking sequence and 710 bp of 3'-flanking sequence. The gene had an identical intron-exon structure (16 exons and 15 introns) to the maize Shi gene. The RSsl 5'- flankmg region contained a number of promoter-like sequences, including putative exacting elements homologous to those found in several endosperm-specific, anaerobiosis-inducible, or phloem-specific promoters. The RSsl promoter region, including 1.9 kb 5'-flanking sequence, the first intron, the first exon, and the translational start codon, was fused with coding sequences for β-glucuronidase (GUS) and snowdrop (Galanthus navalis) lectin (GNA). Tobacco plants were transformed with these chimaeric genes in order to determine the expression pattern directed by the RSsl promoter. Histochemical and immunochemical assays demonstrated that the expression of both GUS and GNA was restricted to phloem cells in various tissues (i.e. stem, root, leaf, petiole) and in different transformants. In addition, GNA was detected by immunological assay in the honeydew excreted by peach potato aphids (Myzus persicae), also a phloem sap- sucking insect, feeding on RSsl-GNA transgenic tobacco plants. This provided direct evidence that GNA was not only expressed in the phloem tissue, but was also present in the phloem sap of transgenic tobacco plants. Since GNA has been shown to have antimetabolic effect against BPH, the RSsl-GNA construct is being used to transform rice plants by collaborating groups elsewhere. In order to isolate the phloem protein PP2 gene promoter, the PP2 polypeptide from 3 months old Cucurbita pepo plants was partially sequenced after in situ cleavage with cyanogen bromide vapour, giving 75 residues of sequence on two cyanogen . bromide fragments. Using an oligonucleotide probe based on this amino acid sequence, cDNA clones encoding PP2 were isolated from a C. pepo cDNA library constructed from mRNA of 3-5 days old seedling hypocotyls. A cDNA clone was used as probe to screen a C. pepo genomic library, and several genomic clones were isolated. Restriction mapping showed that these clones contained different genes, consistent with results from Southern blots of C. pepo genomic DNA probed with PP2 cDNA, in which multiple bands were detected in all restriction endonuclease digests. One of the clones was partially sequenced, and was shown to contain a gene encoding PP2. A 1.2 kb 5'-flanking region of this clone was fused with a GUS reporter gene, and this construct was used to transform tobacco. Initial histochemical analysis showed that this chimaeric gene was not expressed in the putative transgenic plants examined. Possible reasons for this failure are discussed

Quantum discord and geometry for a class of two-qubit states

We study the level surfaces of quantum discord for a class of two-qubit states with parallel nonzero Bloch vectors. The dynamic behavior of quantum discord under decoherence is investigated. It is shown that a class of X states has sudden transition between classical and quantum correlations under decoherence. Our results include the ones in M. D. Lang and C. M. Caves [Phys. Rev. Lett. 105, 150501 (2010)] as a special case and show new pictures and structures of quantum discord.Comment: 5 pages, 5 figure

Data Detection and Code Channel Allocation for Frequency-Domain Spread ACO-OFDM Systems Over Indoor Diffuse Wireless Channels

Future optical wireless communication systems promise to provide high-speed data transmission in indoor diffuse environments. This paper considers frequency-domain spread asymmetrically clipped optical orthogonal frequency-division multiplexing (ACOOFDM) systems in indoor diffuse channels and aims to develop efficient data detection and code channel allocation schemes. By exploiting the frequency-domain spread concept, a linear multi-code detection scheme is proposed to maximize the signal to interference plus noise ratio (SINR) at the receiver. The achieved SINR and bit error ratio (BER) performance are analyzed. A computationally efficient code channel allocation algorithm is proposed to improve the BER performance of the frequency-domain spread ACO-OFDM system. Numerical results show that the frequency-domain spread ACO-OFDM system outperforms conventional ACO-OFDM systems in indoor diffuse channels. Moreover, the proposed linear multi-code detection and code channel allocation algorithm can improve the performance of optical peak-to-average power ratio (PAPR