Fibre raman amplifier properties for applications to long-distance optical communications

This paper reviews recent theoretical and experimental studies on optical amplification by stimulated Raman scattering (Raman amplification) in single-mode optical fibres, and discusses its possible applications to long-distance optical communications. The fibre Raman amplifier can be used as an in-line optical amplifier in both repeaterless and non-regenerative all-optical repeater configurations. In the former application, signal transmission of over 400 km has been predicted theoretically, although high-power pump sources are considered to be required. In the latter configuration, in which optical fibre losses are compensated for by Raman gains, it has been shown that extremely long-distance transmission over more than 1000 km is feasible in terms of signal-to-noise ratio, where the distance achievable is mainly limited by the accumulation of Raman noise. Recent experimental demonstrations including bit-error rate measurements on the Raman amplified signal, and laser-diode pumped amplification, etc., are also reviewed. The results confirm the effectiveness of fibre Raman amplifiers in future long-haul systems.     

Direct observation of chemical oscillation at a water/nitrobenzene interface with a sodium-alkyl-sulfate system.

The oscillation of the interfacial tension and electrical potential at a water/nitrobenzene interface was observed with homologous anionic surfactant molecules, sodium-alkyl-sulfates. Concerning small molecules with a short hydrophobic carbon chain, the oscillation period and amplitude decreased with a decrease of the length of the alkyl chain. On the other hand, when surfactant molecules with a long hydrophobic carbon chain were used, no remarkable periodic oscillation occurred after the first oscillation. In all systems, an interfacial flow by Marangoni convection was observed when the oscillation took place. By monitoring the movement of carbon powder scattered on the liquid/liquid interface with a CCD camera, we could observe that the liquid/liquid interface expanded outward from the area on which the surfactant molecules adsorbed when the oscillation occurred. When the small molecule was used, the speed of expansion of the interface (flow speed) was small and shrinkage followed by expansion of the interface repeatedly occurred. However, when the large molecule was used, the flow speed was large and expansion occurred only one time. These results show that hydrodynamic factors and surface activities are important in chemical oscillation systems.     

Validation of a method for predicting the precision, limit of detection and range of quantitation in competitive ELISA.

The mathematical model for predicting the precision, limit of detection (LOD) and range of quantitation (ROQ) in a competitive enzyme-linked immunosorbent assay (ELISA) proposed by Hayashi et al. (Anal. Chem., 2004, 76, 1295) was validated. The model describes the relative standard deviation (RSD) of concentration estimates by the RSDs of pipetting volumes of analyte, enzyme-conjugated antigen, antibody and substrate solutions, and the standard deviation (SD) of inherent absorbances between the wells in an ELISA plate. For 6 kinds of direct competitive ELISA kits, the LOD and ROQ predicted by the model agreed well with those obtained by experiments with real samples. It was also confirmed that the model is applicable to the prediction of uncertainty that depends on the pipetting error of the viscous antiserum solution. The model was demonstrated to be useful for estimating the LOD and ROQ of competitive ELISA.     

On global integrability of BMO functions on general domains

Extending results of Staples and Smith-Stegenga, we characterize measurable subsets of a given domainD ⊃R ⁿ on which BMO(D) functions areL ^p integrable or exponentially integrable. In particular, we characterize uniform domains by the integrability of BMO functions. We also remark on the boundedness of domains satisfying a certain integrability condition for the quasihyperbolic metric.     

Chiral self-dimerization of vanadium complexes on a SiO2 surface: the first heterogeneous catalyst for asymmetric 2-naphthol coupling

The self-dimerized chiral assembly of vanadium-Schiff-base complexes was found to occur on a SiO2 surface and to be the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol with 100% selectivity and 90% enantioselectivity.     

Chemistry of organosilicon compounds 118. Novel ring contraction reaction of (η4-1,2-disilacyclohexadiene)iron tricarbonyls

1,1,2,2-Dimethyl-3,6-diphenyl-1,2-disilacyclohexadiene reacts with iron pentacarbonyl or diiron nonacarbonyl to give the corresponding (diene)iron tricarbonyl complex which undergoes novel ring contraction reaction to (η⁴-1,1-dimethyl-2,5-diphenyl-1-silacyclopentadiene)iron tricarbonyl on thermolysis at 160°C. Similar results were observed with 1,1,2,2-tetramethyl-3,4,5,6-tetraphenyl-1,2-disilacyclohexadiene.     

Formation Thermodynamics of Binary and Ternary Lanthanide(III) Complexes with 1,10-Phenanthroline and Chloride in N,N-Dimethylformamide

Formation thermodynamics of binary and ternary lanthanide(III) (Ln = La, Ce, Nd, Eu, Gd, Dy, Tm, Lu) complexes with 1,10-phenanthroline (phen) and the chloride ion have been studied by titration calorimetry and spectrophotometry in N,N-dimethyl-formamide (DMF) containing 0.2 mol-dm^–3 (C₂H₅)₄NClO₄ as a constant ionic medium at 25°C. In the binary system with 1,10-phenanthroline, the Ln(phen)³⁺ complex is formed for all the lanthanide(III) ions examined. The reaction enthalpy and entropy values for the formation of Ln(phen)³⁺ decrease in the order La > Ce > Nd, then increase in the order Nd < Eu < Gd < Dy, and again decrease in the order Dy > Tm > Lu. The variation is explained in terms of the coordination structure of Ln(phen)³⁺ that changes from eight to seven coordination with decreasing ionic radius of the metal ion. In the ternary Ln³⁺-Cl^–-phen system, the formation of LnCl(phen)²⁺, LnCl₂(phen)⁺, and LnCl₃(phen) was established for cerium(III), neodymium(III), and thulium(III), and their formation constants, enthalpies, and entropies were obtained. The enthalpy and entropy values are also discussed from the structural point of view.