Directly Modulated 10 Gb/s Signal Transmission over 320 km of Negative Dispersion Fiber for Regional Metro Network

We demonstrate the transmission of directly modulated 10-Gb/s WDM signals over 320 km of negative dispersion fiber (dispersion:-2.5 ps/km/nm @1550 nm) without dispersion compensation. The results indicate that a regional metro WDM network could be implemented cost-effectively by using the proposed negative dispersion fiber and direct modulated lasers.     

Synthesis and performance of cyclic phosphorus-containing flame retardants

A series of organo-cyclic phosphorus compounds were synthesized in an attempt to find an efficient flame retardant (FR) for acrylonitrile-butadiene-styrene (ABS). The success of synthesis was confirmed by ¹H and ³¹P NMR. Thermogravimetric analysis (TGA) results reveal that cyclic phosphorus compounds synthesized in this study show almost one step degradation between 250 and 400 °C and are believed to work in the vapour phase rather than in the condensed phase. From UL-94 test, V-0 rating was achieved at 15-35 wt% loading of cyclic or cyclic alkyl phosphonate FR and no rating at 35 wt% loading of cyclic phosphate for ABS. On the other hand, a much lower loading (7.5%) was needed to obtain V-0 rating for polycarbonate when 3,9-diphenyl-3,9-dioxa-2,4,8,10-tetraoxa-3,9-diphosphaspiro-5,5-undecane (PBPP) was added as FR. All the results show that the flame retarding effect is strongly dependent on the P content of the FR incorporated. The flame retardant mechanism of cyclic phosphorus compounds is also discussed.     

Preferentially linear connection of gold nanoparticles in derivatization with phosphorothioate oligonucleotides

A gold nanosphere in water is considered to attain special stability in derivatization like an artificial atom when the octet rule is satisfied by forming four covalent bonds with two 5'-phosphorothioate-modified oligonucleotide molecules. Owing to this, the hybridization of two mutually complementary gold-bound oligonucleotides makes gold nanospheres preferentially connected linearly by duplexes to produce strands like linear artificial molecules. We have then fixated the linear strands of DNA-linked gold nanospheres by reducing Ag(+) ion clusters immobilized around duplexes to show the absorption spectrum of silver-coated artificial-molecular nanorods.     

Experimental study of dielectrophoresis and liquid dielectrophoresis mechanisms for particle capture in a droplet

This work presents a microfluidic system that can transport, concentrate, and capture particles in a controllable droplet. Dielectrophoresis (DEP), a phenomenon in which a force is exerted on a dielectric particle when it is subjected to a non-uniform electric field, is used to manipulate particles. Liquid dielectrophoresis (LDEP), a phenomenon in which a liquid moves toward regions of high electric field strength under a non-uniform electric field, is used to manipulate the fluid. In this study, a mechanism of droplet creation presented in a previous work that uses DEP and LDEP is improved. A driving electrode with a DEP gap is used to prevent beads from getting stuck at the interface between air and liquid, which is actuated with an AC signal of 200 V(pp) at a frequency of 100 kHz. DEP theory is used to calculate the DEP force in the liquid, and LDEP theory is used to analyze the influence of the DEP gap. The increment of the actuation voltage due to the electrode with a DEP gap is calculated. A set of microwell electrodes is used to capture a bead using DEP force, which is actuated with an AC signal of 20 V(pp) at a frequency of 5 MHz. A simulation is carried out to investigate the dimensions of the DEP gap and microwell electrodes. Experiments are performed to demonstrate the creation of a 100-nL droplet and the capture of individual 10-μm polystyrene latex beads in the droplet.     

Selective Lead Adsorption by Recombinant Escherichia coli Displaying a Lead-Binding Peptide

A highly specific lead-binding peptide ThrAsnThrLeuSerAsnAsn was displayed on Escherichia coli, and lead adsorption characteristics of the recombinant bacteria were investigated. Cell surface-displayed peptide was expressed under the control of an arabinose promoter using outer membrane protein C (OmpC_t) as an anchoring motif. The optimal induction period and arabinose concentration for the expression of peptide-fused OmpC_t were determined to be 2 h and 0.001 g/L, respectively. Selective adsorption of Pb²⁺ onto recombinant cells was verified with individual or combinatory use of four metal ions, Pb²⁺, Ni²⁺, Co²⁺, and Cu²⁺; the amount of bound Pb²⁺ onto the biosorbents was significantly higher than the other metal ions. The adsorption isotherm of recombinant cells for Pb²⁺ followed the Langmuir isotherm with a maximum adsorption loading (q _max) of 526 μmol/g dry cell weight.     

Benzimidazole-based receptor for Zn2+ recognition in a biological system: a chemosensor operated by retarding the excited state proton transfer

A new benzimidazole-based receptor was developed with potential functional groups for excited state proton transfer (ESPT) through keto–enol tautomerism. The enol form of the receptor selectively recognizes Zn²⁺, allowing it to be used as a ratiometric fluorescence sensor in DMSO/CH₃CN (1:9, v/v). The binding event triggers a blue-shifted band through the modulation of charge transfer transitions. The sensor is applicable for recognizing Zn²⁺ in the cytoplasm of Saccharomyces cerevisiae.     

Ultrahigh density arrays of toroidal ZnO nanostructures by one-step cooperative self-assembly processes: mechanism of structural evolution and hybridization with Au nanoparticles

A quick protocol for the fabrication of ultrahigh density arrays of toroidal ZnO nanostructures with tailored structures on a substrate surface is presented based on the one-step spin coating of a common solution composed of inverse micelles of polystyrene-block-poly(4-vinyl pyridine) copolymers (PS-b-P4VP) and sol-gel precursors without the need of conventional complex lithographic techniques. ZnO toroids decorated with gold nanoparticles are also obtained by subsequent loading and reduction of metallic precursors. It was elucidated that the diethanolamine moiety in the sol-gel precursors, which induces selective swelling and structural reorganization of the P4VP core blocks, plays a key role in the generation of toroidal nanostructures. Toroidal ZnO nanostructures embedded in a PS-b-P4VP matrix films or arrays of pure wurtzite ZnO nanorings are obtained by calcination under inert atmosphere. The structural parameters of the toroidal nanostructures such as the width, height, diameter of the rims as well as the spacing of their 2D arrays are controlled by employing PS-b-P4VP with different molecular weight and varying the mixing protocols.     

Selective Semihydrogenation of Alkynes on Shape‐Controlled Palladium Nanocrystals

A systematic study on the selective semihydrogenation of alkynes to alkenes on shape‐controlled palladium (Pd) nanocrystals was performed. Pd nanocrystals with a cubic shape and thus exposed {100} facets were synthesized in an aqueous solution through the reduction of Na₂PdCl₄ with L ‐ascorbic acid in the presence of bromide ions. The Pd nanocubes were tested as catalysts for the semihydrogenation of various alkynes such as 5‐decyne, 2‐butyne‐1,4‐diol, and phenylacetylene. For all substrates, the Pd nanocubes exhibited higher alkene selectivity (>90 %) than a commercial Pd/C catalyst (75–90 %), which was attributed to a large adsorption energy of the carbon–carbon triple bond on the {100} facets of the Pd nanocubes. Our approach based on the shape control of Pd nanocrystals offers a simple and effective route to the development of a highly selective catalyst for alkyne semihydrogenation.     

Sesquiterpenes from Rhizomes of Cyperus rotundus with Cytotoxic Activities on Human Cancer Cells in vitro

Two new sesquiterpenes, cyperusol A₃ ( 1 ) and 3β‐hydroxycyperenoic acid ( 2 ), along with three known sesquiterpenes, britanlin E ( 3 ), 1β,4α‐dihydroxyeudesm‐11‐ene ( 4 ), and 11,12‐dihydroxyeudesm‐4‐en‐3‐one ( 5 ), were isolated from the AcOEt‐soluble fraction of rhizomes of Cyperus rotundus L. The structures of 1 and 2 were elucidated by physical and spectroscopic methods (¹H‐ and ¹³C‐NMR, 2D‐NMR, and MS). All of the isolates, 1 – 5 , were evaluated for their cytotoxic activities against human ovarian cancer cells (A2780) and endometrial adenocarcinoma cells (Ishikawa) using MTT assays.