Application of high pressure induced by water-freezing to the direct catalytic asymmetric three-component List-Barbas-Mannich reaction

High pressure induced by water-freezing has been successfully applied to the direct catalytic asymmetric-three component List-Barbas-Mannich reaction, in which higher yield and better enantioselectivity can be realized than those from the reaction at room temperature under 0.1 MPa.     

Birefringence simulation of annealed ingot of magnesium fluoride single crystal

We developed a method for simulating birefringence of an annealed ingot of MgF₂ single crystal for lithography optics. This method provides the optical path difference caused by crystal symmetry and residual stress existing in the crystal. The method consists of the heat conduction analysis, the residual stress analysis and the birefringence analysis. Because there exists no experimental data on the inelastic behavior of MgF₂ single crystal, the residual stress was estimated with the elastic thermal stress analysis using the finite element method by assuming a stress-free temperature. In this analysis, the temperature dependence of material properties and crystal anisotropy were taken into account. In the birefringence analysis, the distributions of optical path difference were calculated by an approximate method using the result of the residual stress analysis. This approximate method uses the average stress along the wave normal and is equivalent to the exact method in case of low stress dealt with the present study. In this analysis, it is possible to consider both the intrinsic birefringence and the stress birefringence in any crystal orientation. The distribution of the optical path difference in the annealed ingot obtained from the present calculation agrees qualitatively with that of the experiment. Its calculated value also agrees reasonably well with that of the experiment, when a stress-free temperature is adequately selected.     

Mobility performance of a rigid wheel in low gravity environments

To investigate influences of gravity on mobility of wheeled rovers for future lunar/planetary exploration missions, model experiments of a soil-wheel system were performed on an aircraft during variable gravity maneuvers. The experimental set-up consists of a single rigid wheel and a soil bed with two kinds of dry sands: lunar soil simulant and Toyoura sand. The experimental results revealed that a lower gravity environment yields higher wheel slippage in variable gravity conditions. In addition to the partial gravity experiments, the same experiments with variable wheel load levels were also performed on ground (1 g conditions). The on-ground experiments produced opposite results to those obtained in the partial gravity experiments, where a lower wheel load yields lower slippage in a constant gravity environment. In low gravity environments, fluidity (flowability) of soil increases due to the confining stress reduction in the soil, while the effect of the wheel load on sinkage decreases. As a result, both of these effects are canceled out, and gravity seemingly has no effect on the wheel sinkage. In the meantime, in addition to the effect of wheel load reduction, the increase of the soil flowability lessens the shear resistance to the wheel rotation, as a result of which the wheel is unable to hold sufficient traction in low gravity environments. This suggests that the mobility of the wheel is governed concurrently by two mechanisms: the bearing characteristics to the wheel load, and the shearing characteristics to the wheel rotation. It appears that, in low gravity, the wheel mobility deteriorates due to the relative decrease in the driving force while the wheel sinkage remains constant. Thus, it can be concluded that the lunar and/or Mars’ gravity environments will be unfavorable in terms of the mobility performance of wheels as compared to the earth’s gravity condition.     

Parallel algorithms for variational inequalities over the Cartesian product of the intersections of the fixed point sets of nonexpansive mappings

This paper presents a framework of iterative algorithms for the variational inequality problem over the Cartesian product of the intersections of the fixed point sets of nonexpansive mappings in real Hilbert spaces. Strong convergence theorems are established under a certain contraction assumption with respect to the weighted maximum norm. The proposed framework produces as a simplest example the hybrid steepest descent method, which has been developed for solving the monotone variational inequality problem over the intersection of the fixed point sets of nonexpansive mappings. An application to a generalized power control problem and numerical examples are demonstrated.     

Mössbauer spectroscopic study of photo-sensitive organic–inorganic hybrid system, (SP)[Fe(II)Fe(III)(dto)3](dto = C2O2S2, SP = spiropyran)

A photo-sensitive organic–inorganic hybrid system (SP)[Fe^IIFe^III(dto)₃] (SP = spiropyran, dto = C₂O₂S₂), has recently been developed, where the photo-isomerization of the intercalated spiropyran in solid state triggers the change of the magnetic properties, including the ferromagnetic transition temperature from 5 to 22 K. We performed ⁵⁷Fe Mössbauer measurement in order to probe the microscopic states of iron ions in (SP)[Fe^IIFe^III(dto)₃] and have investigated the photo-induced effect on them. The sample without UV-irradiation shows the charge transfer phase transition between 200 and 70 K and the higher and lower temperature phases coexist below 70 K, whereas the UV-irradiated sample does not undergo the charge transfer phase transition and the higher temperature phase is stable between 200 and 6 K.     

Synthetic study of biphenylquinolizidine alkaloids I. Asymmetric total synthesis of lasubine I featuring organocatalyzed asymmetric intramolecular aza-Michael addition

A new procedure for the asymmetric total synthesis of lythraceous alkaloids with a 4-arylquinolizidine skeleton was developed, which involved an organocatalyzed asymmetric intramolecular aza-Michael addition.     

Artabotryols A – E,New Lanostane Triterpenes from the Seeds of Artabotrys odoratissimus

Six new lanostane triterpenes, artabotryols A, B, C1, C2, D, and E ( 1, 2, 3a, 3b, 4 , and 5 , resp.) have been isolated from the seeds of Artabotrys odoratissimus (Annonaceae). Their structures have been established as (3α,22S,25R)‐3‐hydroxy‐22,26‐epoxylanost‐8‐en‐26‐one ( 1 ), (3α,22S,25R)‐22,26‐epoxylanost‐8‐ene‐3,26‐diol ( 2 ), (3α,22S,25R,26R)‐26‐methoxy‐22,26‐epoxylanost‐8‐en‐3‐ol ( 3a ), (3α,22S,25R, 26S)‐26‐methoxy‐22,26‐epoxylanost‐8‐en‐3‐ol ( 3b ), (3α,22S,25R)‐3,22‐dihydroxylanost‐8‐en‐26‐oic acid ( 4 ) and (3α,7α,11α,22S,25R)‐3,7,11‐trihydroxy‐22,26‐epoxylanost‐8‐en‐26‐one ( 5 ) by spectroscopic studies and chemical correlations.     

Colorimetric Calibration of Video Cameras Using Two Color Constancy Models

Colorimetric calibration of color imaging devices is important to realize device independent color reproductions. However the calibration for digital or video cameras is difficult because a color image is acquired for unknown objects under various unknown illuminants. An experiment was carried out based on two computational color constancy models, the finite-dimensional linear model and the spectral sharpening model, to estimate colorimetric values using image data of a color chart captured by video camera. We estimated the colorimetric values by using a single reference reflectance with known spectral reflectance in a color chart under an unknown illuminant. The accuracy was evaluated by color differences in CIELAB color space and was compared on three different color charts under three different illuminants including a fluorescent lamp. It was confirmed that the two computational models do not require prior knowledge of illuminants and surfaces. The finite-dimensional linear model gave more accurate results than the spectral sharpening model in the simulations and experiments.     

Control of peroxyoxalate chemiluminescence by nitrogen-containing ligand quenching: turning off and on by ligand-metal ion host-guest interactions

The control of peroxyoxalate chemiluminescence (PO-CL) by the coordination of nitrogen-containing ligands and metal cations was investigated. Turning the CL off and on was done by PO-CL using 15-monoazacrown-5-tethered anthracene and alkali metal ions. CL quenching and regeneration was also observed in the separated molecular system of 15-monoazacrown-5 and the fluorophores. CL quenching by a number of ligands bearing dipicolylamino groups was evaluated by these PO-CL reactions and found to be closely related to their oxidation potentials, which is dependent on the Weller rate law for electron exchange and this provides strong support for the existence of the CIEEL PO-CL process. When Zn²⁺ or Cu²⁺ are added to the PO-CL system quenched by the ligand, N-[2-(2,2′-dipicolylamino)ethyl]aniline, CL was turned on because the electron donating ability of the ligands was modulated. This was controlled by the coordination of the studied metal ions and, therefore, this system results in CL because of host-guest interactions.