Synthesis and photochemical property of polymers with pendant donor–acceptor-type norbornadiene moieties

The donor–acceptor-type norbornadiene (D–A NBD) 1,4,5,6-tetramethyl-3-phenyl-2,5-NBD-2-carboxylic acid was prepared by the Diels–Alder reaction of methyl 3-phenylprop-2-ynoate with 1,2,3,4-tetramethyl-1,3-cyclopentadiene. 1,4,5,6,7-Pentamethyl-3-phenyl-2,5-NBD-2-carboxylic acid was also synthesized in the same way. Styrene-type polymers with pendant D–A NBD moieties were prepared with a 100% degree of substitution (DS) by the reaction of D–A NBD carboxylic acids with poly[(p-chloromethyl)styrene] with 1,8-diazabicyclo[5.4.0]undecene-7 in dimethyl sulfoxide at 70 °C for 6 h. In the reaction of D–A NBD carboxylic acids with poly(2-chloroethyl vinyl ether), the DSs were about 60%. The photochemical valence isomerizations of all the NBD polymers proceeded smoothly with UV irradiation in tetrahydrofuran solutions and in the film state. In addition, the rate of the photochemical reaction of the NBD polymers increased efficiently by the addition of 4,4′-bis(diethylamino)benzophenone as a photosensitizer in a film state. The stored thermal energy of the irradiated polymers was also evaluated by differential scanning calorimetry to be 55–74 kJ/mol. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1764–1773, 2001     

Molecular-orbital structure in Be isotopes

The structure of ¹²Be is investigated using a microscopic α+α+4n model based on the molecular-orbit (MO) model. It is shown that the remark-able α-clustering and the contribution of the spin-orbit interaction make the binding of the state with the (3/2^?)²(1/2⁺)² configuration for the valence neutrons properly stronger in comparison with the closed p-shell (3/2^?)²(1/2^?)² configuration. The molecular-like structure of the C isotopes is also investigated using a microscopic α+α+α+n+n+... model.     

Improvement of focusing characteristics of a spiral plasmonic lens

We designed and fabricated a spiral plasmonic lens (PL) with multi-circular grooves to increase light intensity in a farfield region via the constructive interference of the light scattered by the multi-circular grooves. To compare the beam focusing characteristics of a spiral PL with multi-circular grooves with those of a conventional spiral PL, we simulated the electric field distribution of the PLs operating at a 405 nm wavelength. We confirmed that the light intensity increased about twofold at 0.75 μm above the PL surface owing to the effect of the multi-circular grooves. Furthermore, the circular grooves negligibly affect the full width at half-maximum of the focal spot, keeping the subwavelength size (～200 nm) of incident light.     

A novel method for analyzing solanesyl esters in tobacco leaves using atmospheric pressure chemical ionization/mass spectrometer

A direct and simple method for analyzing solanesyl esters found in tobacco leaves was developed. Sample preparation was performed by accelerated solvent extractor 200 (ASE200™) using n-hexane followed by evaporating solution in vacuo and dissolving residue with acetone. The separation of analytes was conducted through high-performance liquid chromatography (HPLC) equipped with an SIL-C18/5C™ column and the non-aqueous reversed phase chromatography (NARP) technique using acetone and acetonitrile as the mobile phase with a linear gradient. Atmospheric pressure chemical ionization/mass spectrometer (APCI/MS) in positive mode was used to detect solanesyl esters in the following conditions: capillary voltage 4000 V, corona current 10 μA, drying gas flow 5 mL/min, fragmentor voltage 200 V, nebulizer pressure 60 psi, and vaporizer temperature 500 °C. Each solanesyl ester was identified by the comparison of analyte with synthesized solanesyl esters. Quantification was conducted by selected ion monitoring (SIM) mode in order to detect the specific product ion (613.6 m/z) fragmented from solanesyl ester. The calibration curve was made in the range of 0.1–40 μg/mL with a regression coefficient over 0.999 on almost all solanesyl esters. The limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.01 to 0.05 μg/mL and from 0.03 to 0.15 μg/mL, respectively, on the SIM mode of MS for quantification. Recovery (%) ranged from about 80 to 120%. The direct quantification using the developed method succeeded in showing a different amount and composition of solanesyl esters among various tobacco leaves.     

Homogenization problem for stochastic partial differential equations of Zakai type

We discuss homogenization for stochastic partial differential equations (SPDEs) of Zakai type with periodic coefficients appearing typically in nonlinear filtering problems. We prove such homogenization by two different approaches. One is rather analytic and the other is comparatively probabilistic.     

Crystal structure of the high-pressure phase of hexahydro-1,3,5-trinitro-1,3,5-triazine (gamma-RDX)

The crystal structure of the high-pressure phase of hexahydro-1,3,5-trinitro-1,3,5-triazine (gamma-RDX), which is stable above 4 GPa at room temperature, was investigated by using infrared spectroscopy and powder X-ray diffraction measurements followed by Rietveld refinements using a diamond anvil cell (DAC). Although gamma and alpha phases were found to belong to the same space group Pbca, they exhibited a different crystal packing. The molecular structure of the gamma phase exhibited the same conformation as that of the alpha phase; however, the torsion angles of N-NO2 changed marginally.