Optical Devices for Optical Access Networks Recent Progress in Semiconductor Optical Devices and Optical Modules

Cost-effectiveness is essential in developing optical access network systems. To reduce system costs, both improved system and component technologies are required. Reducing the costs of optical devices and modules in an optical network unit is especially necessary. In this paper, the requirements for optical devices in optical access networks and modules are clarified. Moreover, we also review the recent progress in technologies for semiconductor optical devices and hybrid integration for low-cost optical modules in access networks.     

Synthesis and properties of polyamides derived from systematically halogenated terephthalic acids with fluorine,chlorine, or bromine atoms

Aromatic polyamides were prepared from systematically halogenated terephthalic acids with hexamethylene diamine, piperazine, 4,4′-diaminodiphenylether and p-phenylene diamine by interfacial or low temperature solution polycondensation. The halogenated terephthalic acids used have mono-, di-, or tetra-substituted fluorine, chlorine, or bromine atoms on the benzene ring. The nonhalogenated terephthalic acid was also used for the comparison. The effects of halogen substitution on the benzene ring on the synthesis and some properties of polymers were examined. Reduced specific viscosity decreased in the order F > Cl > Br by halogen substitution. The incorporation of halogen substituents on the ring led to a decrease of crystallinity and fluoro-substituents hindered the crystallization more strongly. The melting point (T_m) decreased in the order F > Cl > Br by mono-substitution, and Br > Cl > F by di-and tetra-substitution. The change of T_m caused by the difference of the number of halogen substituents differed depending on the rigidity of polymer chains. The flame-retardancy estimated by thermogravimetry, self-ignition, and flash-ignition test increased with increasing halogen content of the polymers. Solubility increased remarkably by halogen substitution. The peak temperature of tan δ decreased by halogen substitution. Some discussion was made on these effects of halogen substitution.     

Oscillation of solutions of second-order nonlinear self-adjoint differential equations

We are concerned with the oscillation problem for the nonlinear self-adjoint differential equation (a(t)x′)′+b(t)g(x)=0. Here g(x) satisfied the signum condition xg(x)>0 if x≠0, but is not imposed such monotonicity as superlinear or sublinear. We show that certain growth conditions on g(x) play an essential role in a decision whether all nontrivial solutions are oscillatory or not. Our main theorems extend recent results in a serious of papers and are best possible for the oscillation of solutions in a sense. To accomplish our results, we use Sturm's comparison method and phase plane analysis of systems of Liénard type. We also explain an analogy between our results and an oscillation criterion of Kneser-Hille type for linear differential equations.     

First total synthesis of murisolin

The first and concise total synthesis of murisolin (1) was accomplished using asymmetric alkynylation and Sonogashira coupling as the key steps. The threo/trans/threo-type THF ring moiety was constructed with excellent stereoselectivity by asymmetric alkynylation of 1,6-heptadiyne to alpha-tetrahydrofuranic aldehyde, which was also prepared via the asymmetric alkynylation.     

Investigation of airborne particles by inductively coupled plasma emission spectrometry calibrated with monodisperse aerosols

An emission spectrometric method for the investigation of airborne particles has been developed. Sample air was directly introduced into an ICP to vaporize and atomize the particles and to excite the atoms or ions. The emission signal from the ICP was observed as a flash for each particle when the particle concentration was sufficiently low. The flashes were converted into electric pulses, which were counted by a pulse height analyzer. Thus, for particles of homogeneous composition the particle concentration and size distribution were determined simultaneously for a given element. To calibrate the measuring system, monodisperse aerosols were prepared by using a vibrating orifice monodisperse aerosol generator. Sodium chloride, calcium nitrate and copper nitrate aerosols were generated using solutions of known concentrations. The concentration and size distribution of copper particles were determined in aerosols generated by a small arc at the switch of a lamp socket when a 200-W lamp was turned off. Most of the particles were less than 1μm in diameter with a peak distribution at 0.7 μm. The smallest particles measurable for calcium oxide and copper were 0.1 and 0.3 μm in diameter, respectively.     

A note on the convergence of multiconfigurational many-body perturbation theory

The convergence of multiconfigurational many-body perturbation theory (MC MBPT ) is discussed in connection with the intruder state. Its convergence properties are first examined with a fictitious three-level system employing a Hermitian version of MC MBPT , which permits a general model space. It is then applied to the H₂—H₂ and N₂ systems. The results suggest that a more extensive model space is likely to embrace new intruder states and the space extension be executed with due caution.     

Rapid high-performance liquid chromatographic determining technique of sulfamonomethoxine, sulfadimethoxine, and sulfaquinoxaline in eggs without use of organic solvents

A determining technique of sulfonamides (SAs) (sulfamonomethoxine (SMM), sulfadimethoxine (SDM), and sulfaquinoxaline (SQ)) in eggs, without use of organic solvents, is developed utilizing a high-performance liquid chromatography (HPLC) interfaced with a photo-diode array detector. The sample preparation was performed by homogenizing with perchloric acid solution using a handy ultrasonic-homogenizer followed by a centrifugal ultra-filtration unit. An analytical column and an isocratic mobile phase for HPLC are a reversed-phase C₄ column ( mm i.d.) and 0.18 mol l⁻¹ citric acid solution, respectively. The proposed technique was shown to be linear (r>0.998) over the concentration range 0.1-2.0 μg g⁻¹. Average recoveries of three SAs (spiked 0.05, 0.1, 0.15, and 0.2 μg g⁻¹) ranged from 80.3 to 88.4%, with relative standard deviations (R.S.D.s) between 3.4 and 5.8%. The practical detection limits and total time required for the analysis of one sample were < 0.05 μg g⁻¹ and <30 min, respectively. In all the processes, no organic solvents were used at all.     

Total synthesis of murisolins and evaluation of tumor-growth inhibitory activity

Convergent total syntheses of murisolin (1), natural 16,19-cis-murisolin 2, and unnatural 16,19-cis-murisolin 3 were accomplished by asymmetric alkynylation of alpha-tetrahydrofuranic aldehyde with a diyne and Sonogashira coupling with a gamma-lactone segment as the key steps. Stereoisomers of alpha-tetrahydrofuranic aldehyde were synthesized with high optical purity and the asymmetric alkynylation of these with 1,6-heptadiyne proceeded in good yield and with high diastereoselectivity. The cell-growth inhibition profile and COMPARE analysis of the synthetic compounds 1-3 were also investigated.     

Application of shielded column liquid chromatography for determination of sulfamonomethoxine, sulfadimethoxine, and their N4-acetyl metabolites in milk

A hazardous-chemical free method for simultaneous determination of sulfamonomethoxine (SMM), sulfadimethoxine (SDM), and their N4-acetyl metabolites in raw milk using shielded column liquid chromatography is developed. The target analytes are extracted by mixing with ethanol-acetic acid (97:3, v/v) followed by centrifugation. The procedure uses a Hisep shielded hydrophobic phase (SHP) column, isocratic elution with 0.1% acetic acid solution (pH 3.1, in water)-ethanol (75:25, v/v), and a photo-diode array detector. Average recoveries from samples spiked at 25-500 ng/ml for each drug were >81% with relative standard deviations within 5%. The limits of quantitation were <25 ng/ml.