Synthesis of a highly luminescent three-dimensional pyrene dye based on the spirobifluorene skeleton

We have synthesized a highly luminescent (log e > 5.0, F > 0.9) pyrene dye based on a spirobifluorene skeleton [2,2',7,7'-tetrakis(7-tert-butyl-1-pyrenyl)-9,9'-spirobi[9H-fluorene; 4-PySBF]. The use of spirobifluorene prevents fluorescence quenching by intramolecular energy transfer and/or electron transfer among the chromophores in the excited state. The emission spectra of 4-PySBF exhibited a red shift of 20 nm in comparison to a model compound [9,9'-dioctyl-2,7-bis(7-tert-butyl-1-pyrenyl)-9H-fluorene; 2-PyF], but its UV-Vis spectrum remained unchanged.     

Peierls mechanism of the metal-insulator transition in ferromagnetic hollandite K2Cr8O16

Synchrotron x-ray diffraction experiment shows that the metal-insulator transition occurring in a ferromagnetic state of a hollandite K(2)Cr(8)O(16) is accompanied by a structural distortion from the tetragonal I4/m to monoclinic P112(1)/a phase with a √2×√2×1 supercell. Detailed electronic structure calculations demonstrate that the metal-insulator transition is caused by a Peierls instability in the quasi-one-dimensional column structure made of four coupled Cr-O chains running in the c direction, leading to the formation of tetramers of Cr ions below the transition temperature. This provides a rare example of the Peierls transition of fully spin-polarized electron systems.     

9,9′‐spirobifluorene‐containing polycarbonates: Transparent polymers with high refractive index and low birefringence

Syntheses of 2,2′‐bisalcoholic group‐substituted 9,9′‐spirobifluorene monomers 2 were performed by the reaction of 2,2′‐dihydroxy‐9,9′‐spirobifluorene 2a with haloalcohols. Polycarbonates consisting of 9,9′‐spirobifluorene skeleton in the main chain (PC 4 ) were synthesized by the polycondensation of 2,2′‐bisalcoholic monomers 2 and triphosgene or diphenyl carbonate. PC 4 showed good thermal stability: the 5% weight loss temperature was over 330 °C under both nitrogen and air atmospheres. The glass transition temperature was in a range of 16–269 °C estimated by differential scanning calorimetry, depending on the flexibility of the alkylene or oxyethylene chains of 2 . PC 4 showed high solubility toward ordinary organic solvents such as CHCl₃, benzene, and THF, making possible the preparation of the flexible thin films. Very high refractive index in a range of 1.62–1.66 at 589 nm was observed although PC 4 consists only of C, H, and O atoms, whereas very low degree of birefringence was confirmed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3658–3667, 2010     

Direct evidence for degradation of esperamicin A1 with thiol confirmed by fast-atom bombardment mass spectrometry.

A degradation of esperamicin A1, which is a potent antitumor antibiotic having DNA-cleaving activity, was studied by fast-atom bombardment (FAB) mass spectrometry. It was proved that the degradation easily occurs via the thiol group(s) in the matrix solution and not by a FAB-induced reaction. It was concluded that from the FAB mass spectra of all non-volatile compounds, the molecular weight should be determined by using at least two chemically different matrices.     

Crosstalk Suppression in Header Recognition Unit Using Time-Space Conversion

We demonstrate a suppression effect of a crosstalk among a target and similar header signals using the header recognition filter designed by a design technique of the multiple-object discriminant filter.     

Design and Evaluation of Computer Generated Hologram with Binary Subwavelength Structure Designed by Deterministic Process

A binary subwavelength structure for multilevel phase modulation can be designed by our previously proposed deterministic design method without iterative optimization method. To use our design technique in various applications of a computer generated hologram (CGH) like an array illuminator, beam-shaping, signal processing, and so on, an image quality of a reconstructed image from a CGH has become much more important. In this paper, we verify the image quality of a reconstructed image from a CGH designed by our method in terms of the modulation transfer function (MTF) and the spatial resolution. Simulation results show that our technique can theoretically achieve a MTF of more than 99% over a wide range and a spatial resolution of less than 9.66μm.     

Chemical effects in high-resolution nickel Kalpha X-ray fluorescence spectra.

The nickel Kalpha spectra of oxides, halides (NiF2, K2NiF6, NiCl2, NiBr2), complex compounds, and metal are measured with two different double-crystal X-ray fluorescence spectrometers. The peak shifts and line width changes due to the changes in the chemical states are reported. High reproducibility has been shown for the chemical shift and line width measurements. The DV-Xalpha molecular orbital calculation at the ground and the 1s(-1) hole states was performed to prove that the chemical effect originats from the charge-transfer mechanism.