Input Power Conditions for Distributed Fiber Optic Temperature Sensors in Raman Optical Time-Domain Reflectometry

The critical power of the input pulse in which spontaneous Raman scattering is not seriously disturbed by stimulated Raman scattering in a fiber optic temperature sensor has been investigated experimentally and theoretically. The critical power determines the critical distance, which is nearly equal to the distance where optical time-domain reflectometry (OTDR) signal of the stimulated Raman scattering becomes maximum. From this fact, a new method to determine the critical input power with the OTDR system has been proposed, which may be applicable to most distributed fiber optic temperature sensors. It has been determined that the critical power of the input pulse is 4 watts for an infinitely long silica fiber.Presented at the International Commission of Optics Topical Meeting, Kyoto, 1994.     

On the Polar Decomposition of the Product of Two Operators and Its Applications

Let T = U|T| and S = V|S| be the polar decompositions. In this paper, we shall obtain the polar decomposition of TS as TS = UWV|TS|, where |T||S^*| = W||T||S^*|| is the polar decomposition. Next, we shall show that TS = UV|TS| is the polar decomposition if and only if |T| commutes with |S^*|. Lastly, we shall apply this result to binormal and centered operators. We shall obtain characterizations of these operator classes from the viewpoint of the polar decomposition.     

Synthesis, structure, and bonding of stable dialkylsilaketenimines

Stable (N-aryl)- and (N-alkyl)dialkylsilaketenimines R2SiCNR' [R = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl, R' = 2,6-diisopropylphenyl (2a) and 1-adamantyl (2b)] were synthesized as blue and red crystals by the reactions of isolable dialkylsilylene 3 with 2,6-diisopropylphenyl isocyanide and 1-adamantyl isocyanide. X-ray single-crystal analysis disclosed that molecular structures of 2a and 2b were close to each other and were characterized to be allenic rather than zwitterionic or a silylene-isocyanide complex. The bonding characteristics of silaketenimines are found to be affected strongly by the substituents on silicon and nitrogen atoms. Remarkable red-shift of the pi(Si=C) --> pi*(C=N) band of 2a [lambdamax/nm (epsilon) 647(156)] compared with that of 2b [465 nm (109)] is ascribed to lowering of the pi*(C=N) orbital level due to significant interaction between pi*(C=N) and pi*(N-aryl) orbitals.     

Chemistry of Ru(eta6-1,3,5-cyclooctatriene)(eta2-dimethyl fumarate)2

The chemistry of a novel zerovalent Ru complex, Ru(eta6-cot)(eta2-dmfm)2 (1) (cot=1,3,5-cyclooctatriene; dmfm=dimethyl fumarate), is reviewed with a focus on its reactivity toward phosphines, amines, and H2O, as well as arenes and p-quinones. A variety of novel zerovalent Ru complexes were synthesized from Ru(eta6-cot)(eta2-dmfm)2 (1), and it was shown that the complexes preferably bear both electron-donating and -accepting ligands simultaneously to exhibit thermodynamic stability. The first isolable zerovalent Ru aqua complexes were successfully prepared, and in these complexes, the generation of a chiral center on the O atom of the coordinated H2O was disclosed. In addition, the characteristic catalytic activity of 1 in organic synthesis was considered by reviewing recently developed novel reactions: (i) dimerization of 2,5-norbornadiene to pentacyclo[6.6.0.0(2,6).0(3,13).0(10,14)]tetradeca-4,11-diene (PCTD), (ii) intramolecular hydroamination of aminoalkynes to cyclic imines, (iii) formal [4+2] cycloaddition of alkynes with dmfm to trans-4-cyclohexene-1,2-dicarboxylates, and (iv) co-dimerization of dihydrofurans with alpha,beta-unsaturated esters to 2-alkylidenetetrahydrofurans. The products obtained here are expected to be used as novel functional organic monomers.     

Pd/TEMPO-catalyzed electrooxidative synthesis of biaryls from arylboronic acids or arylboronic esters

A facile electrooxidative method for synthesizing biaryls from arylboronic acids or arylboronic esters is described. In the presence of a catalytic amount of Pd(OAc)₂ and TEMPO, the electrooxidation of arylboronic acids or arylboronates gave the corresponding biaryls in moderate to excellent yields.     

Photoluminescence enhancement in manganese-doped magnesium stannate phosphors synthesized by millimeter-wave irradiation

We have investigated photoluminescence (PL) of Mg₂SnO₄:Mn phosphors synthesized by the irradiation with millimeter-wave of 24 GHz. The PL spectrum at room temperature is dominated by a green band peaking at 500 nm, suggesting the existence of tetrahedral Mn²⁺ sites. When the phosphors are grown by the millimeter-wave heating, the 500 nm band is so much intense compared to those by the electric furnace heating. To clarify the origin of the PL enhancement, we have carried out the measurements of scanning electron microscope (SEM) and electron spin resonance (ESR). The SEM image exhibits the growth of small round particles with an average size of 1.6 μm. Such well-grown micron-sized particles were not observed under the electric furnace heating. The ESR spectra exhibit six prominent lines, the intensity of which becomes greater for the phosphors obtained by the millimeter-wave heating. From this observation, it is supposed that the PL enhancement is mainly due to the increase in the number of tetrahedral Mn²⁺ sites. Therefore, the millimeter-wave heating has an important advantage over the electric furnace heating in the synthesis of Mg₂SnO₄:Mn phosphors.     

Synthesis of novel starburst and dendritic polyhedral oligosilsesquioxanes

The hydrosilylative reaction utilizing octakis(dimethylsiloxy)silsesquioxane and silsesquioxane disilanols bearing alkenylsilyl moieties produces a series of starburst-type giant silsesquioxanes and a second-generation dendritic molecule as well as a boron-containing one.