Reaction of 2,3-diphenylpyrazine 1-oxides with acetic anhydride

Some 2,3-diphenylpyrazine 1-oxides were heated with acetic anhydride to give the corresponding 2,3-di-acetoxy-2,3-dihydro-5,6-diphenylpyrazines. By X-ray diffraction analysis, the configuration of two acetoxyl groups was determined to be trans.     

Flexible Twin Open Ring Metro WDM Network

We have demonstrated a flexible twin open ring WDM network for metro applications. A pair of optical switches in the network keeps the fiber rings open to prevent signal circulation. Traffics are broadcast to every node and selected at the receiving side. Superior transmission and protection switching are proved.     

A Microoptic Network Unit Using Planar Microlens Array

We propose a new concept for an optical network unit using planar microlens array for fiber to the home networks. It is expected from this modeling that an optical coupling loss of 2.5 dB, a polarization dependent loss of 0.5 dB and an extinction ratio larger than 50 dB can be achieved. The structure design and its fabrication method are discussed.     

Singular vectors of the Virasoro algebra in terms of Jack symmetric polynomials

We present an explicit formula of the Virasoro singular vectors in terms of Jack symmetric polynomials. The parametert in the Virasoro central chargec=13-6(t+1/t) is just identified with the deformation parameter of Jack symmetric polynomialsJ (). As a by-product, we obtain an integral representation of Jack symmetric polynomials indexed by the rectangular Young diagrams.     

Complete thermal-unfolding profiles of oxidized and reduced cytochromes C

The complete thermal-unfolding profiles of both oxidized and reduced forms of cytochrome c551 (PA) from mesophilic Pseudomonas aeruginosa and cytochrome c552 (HT) from thermophilic Hydrogenobacter thermophilus were obtained by the newly developed pressure-proof cell compartment installed in a circular dichroic spectrometer, which facilitates protein thermal-unfolding experiments up to 180 degrees C. The thermodynamic cycle, which relates protein stability and redox function, indicated that the redox potentials of PA and HT in the native state are regulated by the stability of the oxidized proteins rather than by that of the reduced ones.     

New method for preparing saturated and unsaturated aliphatic polyurethanes

Saturated and unsaturated aliphatic polyurethane were obtained from three different routes. In route 1, 1,4-dichloro-2-butene, sodium cyanate, and methanol were reacted to give dimethyl 2-butene-1,4-dicarbamate. This is hydrogenated easily to give dimethyl butane-1,4-dicarbamate. Ester exchange reaction of this compound with glycol gave saturated aliphatic polyurethane. In another procedure, route 2, 1,4-dichloro-2-butene, sodium cyanate and excess glycol were reacted to give bis(ω-hydroxyalkyl)-2-butene-1,4-dicarbamate. This was hydrogenated to give bis(ω-hydroxyalkyl)-butane-1,4-dicarbamate. A glycol elimination reaction gave poly(polymethylene tetramethyl-enedicarbamate). By route 3, 1,4-dichloro-2-butene, sodium cyanate, and glycol were reacted to give poly(polymethylene 2-butene-1,4-dicarbamate), a new unsaturated aliphatic polyurethane.     

Single-crystal synthesis and structure refinement of the LiCoO2-LiAlO2 solid-solution compounds: LiAl0.32Co0.68O2 and LiAl0.71Co0.29O2

Single crystals of the LiCoO₂-LiAlO₂ solid solution compounds LiAl_0.32Co_0.68O₂ and LiAl_0.71Co_0.29O₂ were synthesized by a flux method using alumina crucibles. A single-crystal X-ray diffraction study confirmed the trigonal space group and the lattice parameters a=2.8056(11) Å, c=14.1079(15) Å, and c/a=5.028 for LiAl_0.32Co_0.68O₂, and a=2.8023(7) Å, c=14.184(4) Å, and c/a=5.061 for LiAl_0.71Co_0.29O₂. The crystal structures have been refined to the conventional values R=3.2% and wR=2.4% for LiAl_0.32Co_0.68O₂, and R=3.6% and wR=3.5% for LiAl_0.71Co_0.29O₂. The evidence of the location of Al atoms in the pseudotetragonal coordination (6c site), reported previously in LiAl_0.2Co_0.8O₂, could not be observed in the present electron density distribution maps in both LiAl_0.32Co_0.68O₂ and LiAl_0.71Co_0.29O₂. The octahedral distortion analysis indicated that the Al-substitution strongly affected the distortion of the LiO₆ octahedron in this solid-solution compound system, but hardly affected that of the (Al.Co)O₆ octahedron.     

Separation of Semiconducting Single‐Walled Carbon Nanotubes by Using a Long‐Alkyl‐Chain Benzenediazonium Compound

We designed and synthesized 4‐dodecyloxybenzenediazonium tetrafluoroborate ( 1 ), which preferentially reacts with metallic single‐walled carbon nanotubes (SWNTs) by kinetic control. We first determined the suitable experimental conditions for the preferential reaction of 1 with individually dissolved SWNTs by monitoring the decrease in absorbance for the metallic SWNT in the range of 400–650 nm in the absorption spectrum of the SWNTs. The reacted SWNTs were thoroughly rinsed with THF to obtain THF‐insoluble SWNTs. The Raman spectrum of the THF‐insoluble SWNTs showed a strong peak near 180 cm^?1, which corresponds to a semiconducting breathing band. The metallic breathing bands (≈220 cm^?1) and Breit–Wingner–Fano (BWF) modes (1520 cm^?1) corresponding to the metallic SWNTs were much weaker than those of the pristine SWNTs. We also confirmed that metallic peaks in the range of 400–650 nm in the absorption spectrum of THF‐insoluble SWNTs that were individually dissolved in an aqueous micelle of sodium cholate were almost nondetectable. All the results indicate that the THF‐insoluble SWNTs are semiconducting.     

Macro-azo-initiators composed of various polyesters: Their syntheses,thermal properties,and application to block copolymerization

Various aliphatic polyesters such as poly (ethyleneadipate), poly (tetramethylene adipate), poly (caprolactone), and poly (carbonate) were condensed with 4,4'-azobis-4-cyanopentanoyl chloride to prepare macro-azo-initiators. Their thermal properties, observed by differential scanning calorimetry, showed similar decomposition behavior to each other. Block copolymers containing each of these polyesters as a block segment combined with polystyrene or poly (methylmethacrylate) have been derived by the polymerization of monomers initiated with these macro-azo-initiators. © 1994 John Wiley & Sons, Inc.