One-third terabit/s transmission through 150 km ofdispersion-managed fiber

340 Gb/s (seventeen 20-Gb/s 2³¹-1 PRBS NRZ channels) were transmitted through 150 km of fiber with 50 km amplifier spacing. Chromatic dispersion penalties and four-photon mixing effects were minimized by dispersion management     

Efficient solution of large moments problems: Theory and small problem results

A banded matrix iterative solution method for linear simultaneous equations arising from thin wire moments problems has been applied to a variety of multiple wire configurations. Compared to Gaussian elimination, solution efficiencies around 5 to 10 and up to 23 have been obtained for problems with 100 unknowns for a solution accuracy of 1 percent. Greater efficiencies are obtained for less accurate solutions. Reasonable far-field patterns are found from currents with 30 percent error. The method is intended for large problems, for which good efficiencies are expected. Application of the method requires some expertise at the current stage of development.     

Tunable,continuous-wave,ultra-violet radiation around 300 nm by frequency-doubling a rhodamine 6G dye laser

By frequency doubling a cw Rhodamine 6G dye laser using an ADP crystal placed in the laser cavity, in excess of 30 mW of cw uv radiation has been generated. The radiation is tunable over the range 285–315 nm. The ADP crystal is cut with Brewster angle ends, and is located at the focus of cavity compensated for coma and astigmatism. Conversion efficiency is shown to be limited by the onset of thermally induced phase mismatching. Peak uv power can be increased to 85 mW by chopping the radiation from the pumping laser.     

Complete stereochemistry of neamphamide A and absolute configuration of the beta-methoxytyrosine residue in papuamide B

The absolute stereochemistry of the three unresolved structural components in neamphamide A (1) was determined to be (R)-beta-methoxy-L-tyrosine, (2R,3R,4S)-4-amino-7-guanidino-2,3-dihydroxyheptanoic acid, and (2R,3R,4R)-3-hydroxy-2,4,6-trimethylheptanoic acid. Stereochemical assignments were made by chemical degradation of 1, derivatization of the resulting products, and then spectroscopic and chromatographic comparison of the derivatives with synthetically prepared standards. Using the same analytical protocol developed for 1, the beta-methoxytyrosine residue in papuamide B (2) was found to be (R)-beta-methoxy-D-tyrosine. This represents a rare example of divergent stereochemistry in an unusual amino acid residue that is present in two closely related classes of peptides.     

Reaction of copper(II) with ferrocene and 1,1'-dimethylferrocene in aqueous acetonitrile: the copper(II/I) self-exchange rate

The kinetics of the reactions of copper(II) with ferrocene (Fc) and 1,1'-dimethylferrocene (Dmfc) have been studied at 25 degrees C in aqueous acetonitrile (AN) containing 50-97.5 vol % AN. With increasing % AN, the rate constant increases along with the driving-force for the reaction. The results are analyzed in terms of Marcus theory to estimate the Cu(II/I) electron self-exchange rate constant (k11) for the system. Over the solvent range studied, the calculated k11)changes from 1.1 x 10(-9) to 17 x 10(-9) M(-1) s(-1), with an average value of 5 x 10(-9). In addition, the structures of the trifluoromethanesulfonate salts of [Cu(AN)4]+, [Cu(OH2)2(AN)2]2+, and [Cu(AN)4]2+ are reported. It is found that the Cu-NCCH3 bond-length difference between the Cu(I) and Cu(II) oxidation states is only approximately 0.02 A.     

Synthesis of crescent aromatic oligoamides

[structures: see text] This article describes the synthetic procedures for the preparation of crescent (and helical) aromatic oligoamides developed in recent years in our laboratory. The large-scale preparation of a variety of monomers derived from various tetrasubstituted benzenes is presented. Three different strategies for constructing various oligomers consisting of meta- and meta/para-linked benzene residues are discussed. Factors affecting coupling efficiency and yields are analyzed. The developed synthetic methods have provided the basis for the preparation of longer oligomers and for the development of solid-phase synthesis.     

The crystal and molecular structure of dichloro-(bis-1,2-diphenylphosphinoethane)platinum(II)

Crystals of PtCl₂(PPh₂)(CH₂)₂(PPh₂) (1), produced from attempts to prepare hydridochloroplatinum complexes, are monoclinic, space groupP2 ₁ /c, with four molecules in a unit cell of dimensionsa=11.478(3),b=13.263(2)c=16.343(3) Å, and =99.00(2)°. The structure was solved by the heavy-atom method and refined by block-diagonal least-squares calculations with anisotropicthermal parameters;R=0.048 andR=0.061 for 1843 observed reflections. The crystal structure contains discrete well-resolved molecules. The Pt atom has distorted square-planar coordination with Pt-P 2.208(6), Pt-Cl 2.355 and 2.341(6) Å distances, and Cl-Pt-Cl 90.2(2) and P-Pt-P 86.3(2)° angles.