Syntheses of (−)-8-EPI-Swainsonine and (−)-1,8-DI-FPI-Swainsonine,Stereoisomers of Indolizidine Alkaloid,Swainsonine

Recently, we have completed a total synthesis of swainsonine (l), (1S,2S,8R,8aR)-1,2,8-trihydroxyoctahydroindolizine, which exhibits remarkable physiological effects such as an α-mannosidase inhibitory activity, an immunoregulating activity and so on. In order to elucidate a relationship between structures and physiological activities, a congener of swainsonine has been synthesized. In this communication, we wish to report a synthesis of (-)-8-epi-swainsonine (2) and (-)-1,8-di-epi-swainsonine (2) from methyl 3-acetamido-2-0-acetyl-4,6-0-benzylidene-3-deoxy-α-D-glucopyranoside (4) and methyl 3-acetamido-2-0-acetyl-3-deoxy-4,6-di-0-mesyl-α-glucopyranoside-(14), respectively.     

A real-time sound field renderer based on digital Huygens' model

Modeling acoustical behavior in a room is complicated and computationally intense. Although many methods have been proposed for computer simulation and computers have become faster and faster, the procedure is deeply time-consuming as sound space increases. With the development of semiconductor technology, an alternative solution is to simulate and rebuild the sound field distribution using hardware. Compared with other methods, the method based on digital Huygens' model (DHM) is simple and easily implemented by hardware. In this paper, two schemes of DHM are derived to analyze sound propagation in a two-dimensional space, and are implemented by field programmable gate array (FPGA). In a two-dimensional space of size 2 m×2 m, surrounded by rigid walls, the hardware simulation results of both schemes agree well with the software simulation result, and the calculation errors are relatively small. Compared with the software-based FDTD, original scheme, and updated scheme, a hardware system with 1024 nodes implemented by a Xilinx FPGA chip XC5VLX330T-FF1738 speeds up 7.1, 5.5, and 3.6 times, respectively.     

System modeling and tracking control of mobile manipulator subjected to dynamic interaction and uncertainty

Trajectory tracking of a mobile manipulator is a challenging research because of its complex nonlinearity and dynamics. This paper presents an adaptive control strategy for trajectory tracking of a mobile manipulator system that consists of a wheeled platform and a modular manipulator. When a robot system moves in the presence of sliding, it is difficult to accurately track its trajectory by applying the backstepping approach, even if we employ a non-ideal kinematic model. To address this problem, we propose using a combination of adaptive fuzzy control and backstepping approach based on a dynamic model. The proposed control scheme considers the dynamic interaction between the platform and manipulator. To accurately track the trajectory, we propose a fuzzy compensator in order to compensate for modeling uncertainties such as friction and external disturbances. Moreover, to reduce approximation errors and ensure system stability, we include a robust term to the adaptive control law. Simulation results obtained by comparing several cases reveal the presence of the dynamic interaction and confirm the robustness of the designed controller. Finally, we demonstrate the effectiveness and merits of the proposed control strategy to counteract the modeling uncertainties and accurately track the trajectory.     

Studies on the syntheses of polymetalloxanes and their properties as a precursor for amorphous oxide. VII. Preparation and properties of polyzirconoxanes as a precursor for zirconia fibers by the hydrolysis of bis (ethyl acetoacetato) zirconium dialkoxide

Acid-catalyzed hydolysis of bis(ethyl acetoacetato) zirconium dialkoxide in methanol or THF was investigated. The hydrolysis of the chelates in the molar ratios of H₂O/ chelate = 1.0–2.0 and HCl/chelate = 0.1–0.2 provided concentrated solutions (ca. 83 wt %) of polyzirconoxanes (PZO) which showed excellent spinnability and stability to self-condensation. Continuous gel fibers were prepared by dry spinning the solutions. Polyzirconoxanes were isolated as powders when the concentrated solution was precipitated with hexane. Silylation allowed the investigation of the structure of PZO. It was confirmed to be the polymers of a low degree of polymerization with the ligand and hydroxy group as pendants. © 1992 John Wiley & Sons, Inc.     

Supersymmetric non-linear σ model onE 8/SO(10)×SU(3)×U(1)

We calculate the Kähler potential of theE ₈/SO(10)×SU(3)×U(1) homogeneous space. Some quasi Nambu-Goldstone fermions living in the corresponding supersymmetric non-linear σ model are identified with the usual three families of quarks and leptons, and one mirror family. We also show that the dynamical breakdown of supersymmetry does not occur in this model.     

Lindbladione and related naphthoquinone pigments from a myxomycete Lindbladia tubulina

Lindbladione (1), 7-methoxylindbladione (2), and 6, 7-dimethoxylindbladione (3) have been isolated from a myxomycete Lindbladia tubulina and their structures were elucidated by spectral data.     

Alkali metal ion-selective electrodes based on relevant alkali metal ion doped manganese oxides

Potentiometric properties of manganese oxides doped with alkali metal ions (Na⁺, K⁺, Rb⁺ and Cs⁺), which were prepared by heating mixed solutions (starting solution) of each alkali metal and Mn²⁺ ions, were examined. Electrodes based on mixed phases of Nao₄₄MnO₂/Mn₂O₃ and hollandite KMn₈O₁₆/M₂O₃ found by X-ray powder diffraction (XRD) exhibited Na⁺- and K⁺-selective responses with a near-Nernstian slope, respectively, when the molar ratio of alkali metal ion to Mn²⁺ ion in the starting solution was 0.1. When no alkali metal ions were added in the manganese oxide films, no significant potentiometric response was observed to any alkali metal ions. The selectivity coefficients of these electrodes were = 6.7 × 10^–2, = 7.1 × 10^–3, < 9 × 10^–4 and < 9x 10^–4 for the Na_0.44MnO₂/Mn₂O₃, and <4 × 10^–4 <4x 10^–4, =60 × 10^–2 ×10^–4, < 4 × 10^–4, for the KMn₈O₁₆/Mn₂O₃, respectively. Electrodes based on manganese oxides made from mixed solutions of Rb⁺/Mn²⁺ and Cs⁺/Mn²⁺ also responded to the respective primary ions, that is, Rb⁺ and Cs⁺ ions, although XRD patterns for the manganese oxides thus made did not show any peaks except for Mn₂O₃ (bixbyite); it was concluded in these cases that some amorphous type manganese oxides were formed in the Rb⁺/Mn²⁺ and Cs⁺/Mn²⁺ systems and they responded to the respective ions. Conditioning of these electrodes in an aerated indifferent electrolyte solution, 0.1M tetramethylammonium nitrate (TMA-NO₃), for relatively long time, typically more than 2 hours, was found to be a prerequisite for near-Nernstian response to the respective alkali metal ions. During this electrode conditioning, vacant sites (template) suitable in size for selective uptake of primary ions seemed to be formed by releasing the doped alkali metal ions from the solid phase into the adjacent electrolyte solution accompanying oxidation of the manganese oxide film.     

Synthesis, stereochemistry, and reactions of 2,5-diphenylsilacyclopentenes

1,1-Disubstituted derivatives of 2,5-diphenylsilacyclopent-3-enes, namely those having the 1,1-diphenyl, 1,1-dimethyl, 1-alkoxy-1-methyl and 1,1-dialkoxy, were prepared by a one-pot reaction of (1E, 3E)-1,4-diphenyl-1,3-butadiene and dichlorosilanes in the presence of magnesium. Each silacyclopentene was formed as a mixture of one trans and two cis isomers. 1-Ethoxy-1-methyl-2,5-diphenylsilacyclopent-3-ene and 1,1-diethoxy-2,5-diphenylsilacyclopent-3-ene were reacted with optically active alcohols to furnish the corresponding diastereomers. The absolute configuration of one of these diastereomers was determined by X-ray structure analysis. The mixture of cis and trans diastereomers was lithiated by lithium diisopropylamide (LDA) to obtain the trans forms selectively, with the stereoselectivity being determined by NOE experiments.