In situ conversion electron Mössbauer spectrometry applied to the study of the corrosion products formed in solution

The new gas-flow type detector chamber was designed for thein situ CEM spectrometric study of solid-liquid interface. The chamber has both a proportional counter and a solution cell. A sample was immersed in the solution of the lower part of the chamber and a CEM spectrum was collected in the upper after emersion of the sample by continuous rotation of it. It was found that a control of a revolution rate of a sample and the counting gas flow rate was important for good performance. Thein situ CEMS was applied to the analysis of corrosion products formed on a steel in various solutions and its usefulness was demonstrated.     

Mössbauer study on surface crystallization behavior of amorphous Fe90Zr10 alloy ribbon

The precipitous drop of crystallization temperature at the surface of amorphous Fe₉₀Zr₁₀ ribbon is confirmed by TMS and CEMS. The deficiency in Zr at the surface amorphous phase, caused by the absorption and the diffusion of oxygen, is found to be responsible for it. The final crystalline products are assigned to α-Fe, Fe₃Zr and Fe₂Zr, whereas only α-Fe precipitates at the surfaces. Moreover, it is indicated that the crystallization behavior of the bulk is influenced by the ambient gases during annealing and quite different between in vacuum and in air.     

Polysilsesquioxane containing tributylstannyl groups as intermediary derivative for organofunctionalization

Poly(phenylsilsesquioxane) containing tributylstannyl groups (TBPSQ) was a useful intermediate for the synthesis of organofunctionalized polysilsesquioxane ( 2 ). The reaction of TBPSQ and monochlorosilane ( 1 ), which possessed an organofunctional group, proceeded under mild and neutral conditions to give 2 with the elimination of tributylstannylchloride. The combined use of the different chlorosilanes 1 enabled the ready preparation of multifunctionalized polysilsesquioxanes 2 . The number‐average molecular weights and dispersions of 2 were almost the same as those of starting TBPSQ. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 286–292, 2002     

A simple tunable short-pulse XeCl laser with high spectral brightness

A simple tunable short-pulse XeCl laser system with a compact Blumlein circuit is described. In this system, radiation from a XeCl amplifier in order to achieve a wide tunable range and high spectral brightness. The generated radiation is tunable over 307.6–308.6 nm and the maximum peak power is 3 MW. Output pulse duration is shorter than 0.8 ns FWHM with a bandwidth of about 4 pm.     

On the Kernel of the Reciprocity Map of Normal Surfaces over Finite Fields

The reciprocity map of a smooth proper variety over a finite field is known to have a trivial kernel and dense image. In this paper, we investigate the reciprocity map of a normal surface proper over a finite field and give two examples of normal projective surfaces whose reciprocity maps are not injective.     

Nickel-mediated carboxylative cyclization of enynes

Nickel-mediated carboxylative cyclization of α,ω-enyne using carbon dioxide was investigated. Oxidative cycloaddition of enynes having an electron withdrawing group on alkene to a zero-valent nickel complex smoothly proceeded to provide nickelacyclopentene intermediates, which regioselectively reacted with CO₂ at the Csp³-nickel bond, giving cyclized carboxylation products in good yields.     

Unified Total Synthesis of 3‐epi‐Ryanodol,Cinnzeylanol, Cinncassiols A and B,and Structural Revision of Natural Ryanodol and Cinnacasol

Ryanodane diterpenoids structurally share an extremely complex fused ring system, but differ in the substitution patterns of the hydroxy groups. Since these congeners exhibit various biologically important functions, their efficient chemical constructions have been greatly anticipated. We previously accomplished the total synthesis of ryanodine ( 1 ) using pentacycle 8 as the advanced intermediate. Here, we report the unified total syntheses of four distinct diterpenoids, 3‐epi‐ryanodol ( 3 ), cinnzeylanol ( 4 ), cinncassiols B ( 5 ), and A ( 6 ), from 8 , all within 10 steps. A series of highly optimized chemo‐ and stereoselective reactions and protecting‐group manipulations enabled assembly of the densely oxygenated structures of 3 – 6 . Furthermore, the present synthetic studies established the C13S stereochemisty of 5 – 7 and revised the proposed structures of natural ryanodol ( 2 ) and cinnacasol ( 7 ) to be those of 3 and 6 , respectively.