Luminescence of rare-earth ions in perovskite-type oxides: from basic research to applications

Luminescence of a rare-earth ion in SrTiO₃ or other perovskite-type oxides was used as a probe of physical properties of a host crystal, but not as a phosphor because observed luminescence efficiency was low. Recent investigations have shown that the luminescence efficiency of SrTiO₃:Pr³⁺ is intensified up to 200 times by addition of Al ions. This paper reviews experimental results on this phenomenon and discusses mechanism of the Al-addition effect. A survey was made to find other materials, the efficiency of which can be improved by the impurity addition. Host-to-activator energy transfer by a coupling of the band-edge recombination energy and an allowed transition of a rare-earth ion is essential to provide a high efficiency. A red phosphor, Al-added SrTiO₃:Pr³⁺, is promising for display applications.     

Self-discharge characteristics of an electric double-layer capacitor with polymer hydrogel electrolyte

An electric double-layer capacitor (EDLC) was assembled with the polymer hydrogel electrolyte prepared from cross-linked potassium poly(acrylate) (PAAK) and KOH aqueous solution, and the self-discharge characteristics were investigated. The EDLC cell with the polymer hydrogel electrolyte showed lower voltage decay on open circuit than that with a KOH aqueous solution. Moreover, it was found that the leakage current of the EDLC cell was markedly suppressed by using the polymer hydrogel electrolyte. The suppression was enhanced with increasing PAAK content in the electrolyte. These results strongly suggest that the PAAK plays an important role in the suppression of self-discharge.     

Design optimization of axial flow hydraulic turbine runner: Part I—an improved Q3D inverse method

With the aim of constructing a comprehensive design optimization procedure of axial flow hydraulic turbine, an improved quasi‐three‐dimensional inverse method has been proposed from the viewpoint of system and a set of rotational flow governing equations as well as a blade geometry design equation has been derived. The computation domain is firstly taken from the inlet of guide vane to the far outlet of runner blade in the inverse method and flows in different regions are solved simultaneously. So the influence of wicket gate parameters on the runner blade design can be considered and the difficulty to define the flow condition at the runner blade inlet is surmounted. As a pre‐computation of initial blade design on S2m surface is newly adopted, the iteration of S1 and S2m surfaces has been reduced greatly and the convergence of inverse computation has been improved. The present model has been applied to the inverse computation of a Kaplan turbine runner. Experimental results and the direct flow analysis have proved the validation of inverse computation. Numerical investigations show that a proper enlargement of guide vane distribution diameter is advantageous to improve the performance of axial hydraulic turbine runner. Copyright © 2002 John Wiley & Sons, Ltd.     

Total synthesis of dehydroaltenusin

The first total synthesis of dehydroaltenusin, a natural enzyme inhibitor, is described. The key step involves Suzuki-coupling reaction of an aryl triflate prepared from 2,4,6-trihydroxybenzoic acid with a catechol-derived boronic acid or boronic ester. The synthetic product was evaluated as a potent inhibitor against eukaryotic DNA polymerase α and other DNA polymerases.     

Electroreductive acylation of aromatic imines with acylimidazoles

The intermolecular reductive coupling of aromatic imines with acylimidazoles was effected by electroreduction in the presence of chlorotrimethylsilane and gave α-amino-α-aryl ketones. This method was also effective for the synthesis of α-amino-α-aryl esters using methoxycarbonylimidazole as an electrophile.     

Quantitative analysis of 17beta-estradiol in river water by fluorometric enzyme immunoassay using biotinylated estradiol.

A sensitive and simple immunoassay to determine 17beta-estradiol (E2) in fresh water was developed. The method is based on a solid-phase avidin-biotin binding assay and solid phase extraction. The binding event of E2 to the antibody is detected indirectly by the competitive reaction between E2 and biotinylated estradiol (BE) as a tracer for the limited binding sites of antibodies immobilized onto the wall of a microtiter plate. Namely, E2 concentrations are determined from the strong interaction between BE and avidin conjugated with horseradish peroxidase (avidin-HRP). In order to achieve a sensitive measurement for the binding of BE to the antibody immobilized on the microtiter plate substrate, QuantaBlu fluorogenic peroxidase substrate (QFPS) was employed. The detection limit and the linear range of E2 determination were 27 pM and 27 - 7480 pM, respectively. The relative standard deviations (RSD) for the E2 assay were between 0.3 and 12.0% (n = 3). The cross-reactivities of several other estrogens in this assay system were also investigated. No serious influences from any cross-reaction caused by other estrogens tested in this experiment were observed. The determination of E2 in water samples from eight rivers and a marsh in Hokkaido was performed by the immunoassay combined with solid phase extraction. It was found that the concentration of E2 was in the range between 0.06 and 67 pM.     

Instability and mode transition analysis of a hydrogen-rich combustion in a model afterburner

Combustion instabilities were investigated experimentally for a hydrogen-rich combustion in a model afterburner installed at the end of a high-enthalpy wind tunnel. Air was supplied at 0.3 MPa and 950 K. The combustion instabilities were studied with the time-resolved measurements of a near-infrared (NIR) emission from water molecules over 780 nm using a high-speed video camera. Pressure was also measured in the combustor. The pressure and the NIR images were analyzed by data-driven approach, which include the fast Fourier transform (FFT), the wavelet transform, the dynamic mode decomposition (DMD) and the Gaussian process latent variable methods (GP-LVM). Thermoacoustic instability was observed under a rich condition, and the amplitude of the pressure oscillation was the maximum at the overall equivalence ratio of approximately 2.4 or 2.7 as a result of the FFT. The combustion dynamics were investigated in detail for an experimental run at the equivalence ratio of 2.4. A pressure spectrogram indicated a flame–vortex interaction with a Strouhal number of 0.5 (2300 Hz), thermoacoustic instability (560 Hz), and their transitions with the wavelet transform. For NIR images, the same tendency was also observed in the spectrogram of the modes obtained by the Gabor-filtered DMD, which could clearly resolve the high-order harmonic modes of the flame–vortex interaction and the thermoacoustic instability. Furthermore, NIR images were analyzed with GP-LVM to study the evolution of the combustion dynamics in a three-dimensional latent space. Recurrence plots with the Euclidean distance function were used to visualize the evolutions of the combustion dynamics. A limit cycle behavior of the flame–vortex interaction was clearly observed, whereas the limit cycle of the thermoacoustic instability showed more complicated behaviors. The transition behaviors of the instabilities were observed in the recurrence plots in detail, indicating that the flame–vortex interaction excited the fourth harmonic mode of the thermoacoustic instability, followed by the basic mode.     

Synthesis of 1,5-Anhydro- 2-deoxy- 4-O-phosphono-3-O-tetradecanoyl-2-[(3R)- and (3S)-3-Tetradecanoyloxytetradecanamido]-D-glucitol (GLA-40) Related to Bacterial Lipid A

The diastereoisomeric pair of a biologically active, lipid A-subunit analogs named in the title have been synthesized, starting from 2-amino-l,5-anhydro-2-deoxy-4,6-0-isopropylidene-D-glucitol and optically active 3-hydroxytetradecanoic acid.     

Femtosecond Polarization Switching in the Crystal of a [CrCo] Dinuclear Complex

Capability to control macroscopic molecular properties with external stimuli offers the possibility to exploit molecules as switching devices of various types. However, application of such molecular‐level switching has often been limited by its speed and thus efficiency. Herein, we demonstrate ultrafast, photoinduced polarization switching in the crystal of a [CrCo] dinuclear complex by ultrafast pump–probe spectroscopy in the visible and mid‐infrared regions. The photoinduced polarization switching was found to have a time constant of 280 fs, which makes the [CrCo] complex crystal the fastest polarization‐switching material realized using the metastable state. Moreover, the pump–probe data in the visible region reveal the pronounced appearance of coherent nuclear wavepacket motion with a frequency as low as 22 cm^?1, which we attribute to a lattice vibrational mode. The pronounced non‐Condon effect for its resonance Raman enhancement implies that this mode couples the relevant electronic states, thereby facilitating the ultrafast polarization switching.