Enantioselective total synthesis of pteridic acid A

Pteridic acid A, a potent plant growth promoter with auxin-like activity, was synthesized enantioselectively by using the Evans asymmetric aldol reaction as the key C-C bond forming step.     

Organogel of an 8-quinolinol platinum(II) chelate derivative and its efficient phosphorescence emission effected by inhibition of dioxygen quenching

A newly synthesized 8-quinolinol platinum(II) chelate derivative gelates various organic solvents, and the gel formed shows unique thermo- and solvatochromism of visible and phosphorescent colour in response to a sol-gel phase transition and possesses an attractive ability to inhibit dioxygen quenching of excited triplet states.     

Addition to electron deficient olefins of alpha-oxy carbon- centered radicals, generated from cyclic ethers and acetals by the reaction with alkylperoxy- lambda(3)-iodane

Thermal decomposition of 1-tert-butylperoxy-1,2-benziodoxol-3(1H)-one in cyclic ethers and acetals at 50 degrees C generates alpha-oxy carbon-centered radicals, which undergo an addition reaction with vinyl sulfones and unsaturated esters.     

Crystallinity of bulk polyacetylene

The fine structure of bulk trans-polyacetylene (PA) was investigated by x-ray diffraction. The degree of crystallinity 0.81, determined by Ruland's method, was significantly higher than the value for linear polyethylene. The disorder parameter k was 5, which is much larger than the value for polyethylene. These results led us to propose that PA crystals are more disordered than PE crystals owing to the higher rigidity of PA chains. Small-angle x-ray diffraction indicated that the crystal morphology is of the extended-chain type rather than lamellar. All results obtained in this work showed that the fine structure of PA bulk is such as to facilitate electrical conduction of bulk PA.     

Transient behavior of secondary emission of ZnTe under band-to-band excitation

Time characteristics of secondary emissions have been measured in ZnTe at 82K under the excitation into the fundamental absorption band by subnanosecond light pulses. The decay time of polariton luminescence has been determined to be about 100 ps. On the other hand, the time behavior of the intensity of the sharp 2LO-phonon line has been found to coincide with that of the exciting pulse. This result is consistent with the resonance Raman scattering mechanism.     

Two-dimensional wave run-up analysis by selective lumping finite element method

A new finite element technique for the analysis of wave run-up is presented in this paper. In this finite element approach, the movement of the shoreline is expressed by that of the nodal points at the wave front, and an auto mesh generation technique is effectively used. The present method is tested by the comparison with the experimental result of a channel with uniform slope, and two numerical examples are reported to show the efficiency of this method. As a final example, the tsunami run-up caused by the 1983 Nihonkai-Chubu earthquake is analysed and compared with actual records of the flooded area.     

Apparent horizons of time-symmetric initial value for three black holes

The apparent horizon of three black holes on a time-symmetric space-like hypersurface is examined. The area is computed for various values of separation parameters. Using Hawking's mass formula, we found that the maximum possible efficiency of energy release is no more than 8.44 × 10^-3 when the initial apparent horizon encloses three black holes.     

Effects of the three-spin interactions on the magnetic properties of a simple cubic Ising ferromagnet

For a spin one-half simple cubic Ising ferromagnet, the three-spin interaction are shown to have significant effects on the Curie temperature, the magnetization and the magnetic specific heat based on a calculation by the Bethe-Peierls theory.     

Carbon-13 NMR spectra of some epoxides derived from dicyclopentadiene

The ¹³C NMR spectra of a series of epoxides derived from endo- and exo-dicyclopentadiene and their partially hydrogenated compounds were determined to examine the substituent effects arising from the introduction of the oxirane ring in comparison with those found in other ring systems. The ¹³C signals of some epoxides were assigned by using lanthanide shift reagents. Characteristic substituent effects exerted by an oxirane ring were demonstrated. Marked steric γ-effects of ?8—13 ppm were observed at the bridge carbon signal in the bicyclo[2.2.1]heptane skeleton. Differences were found in the substituent effects between endo- and exo-dicyclopentadiene epoxides, and have been discussed in relation to the molecular geometry.