Stabilization of flavylium dye by incorporation into the pore of protonated zeolites

Flavylium dye, a model compound of natural anthocyanin, has a defect that its color stability is very poor. We have complexed the flavylium dye with protonated zeolites and succeeded to enhance both the thermal and chemical stability of the dye. The aqueous dispersion of the flavylium/zeolite complex maintains its color even at 353 K or at pH 9, under which conditions the aqueous solution of the flavylium loses its color immediately. The stability is enhanced when the dye is incorporated into the pore of the zeolites, and a large stabilization effect is obtained by a tight adsorption with a narrow pore, as long as the dye is incorporated into the pore. Because of its enhanced color stability, the flavylium dye incorporated in the zeolite pore can be a candidate for an environmentally friendly coloring material.     

Formulation of the rotational transformation of wave fields and their application to digital holography

Rotational transformation based on coordinate rotation in Fourier space is a useful technique for simulating wave field propagation between nonparallel planes. This technique is characterized by fast computation because the transformation only requires executing a fast Fourier transform twice and a single interpolation. It is proved that the formula of the rotational transformation mathematically satisfies the Helmholtz equation. Moreover, to verify the formulation and its usefulness in wave optics, it is also demonstrated that the transformation makes it possible to reconstruct an image on arbitrarily tilted planes from a wave field captured experimentally by using digital holography.     

Towards implementation of floating cast method for growing large‐scale high‐quality multicrystalline silicon ingot using designed double crucibles

We report on our attempt to scale up the floating cast method to grow high‐quality multicrystalline silicon ingot using specially designed double crucibles. The cross section of the grown ingot showed the large crystal grain size originating from initially formed dendrite crystals around the top of the melt. By using double crucibles, the residual melt was spontaneously removed from the inner crucible to the outer one at the final stage of the crystal growth. Performance of small‐scale solar cells revealed no significant changes between the top and the bottom part of the ingot except the edge of the bottom due to the non‐uniform removal of the melt. This suggests that strong contact of the ingot with the crucible was successfully avoided by the double crucibles. Therefore, the floating cast method combined with specially designed double crucibles is concluded to be feasible, which could be implemented to realize high‐quality multicrystalline silicon ingot for practical size wafers. Copyright © 2013 John Wiley & Sons, Ltd.     

Improvement of stability for organic solar cells by using molybdenum trioxide buffer layer

We demonstrated that the stability of organic solar cells (OSCs) under light irradiation is markedly enhanced by inserting a molybdenum trioxide (MoO₃) buffer layer between an anode layer of indium tin oxide (ITO) and a p-type layer of 5,10,15,20-tetraphenylporphyrin (H₂TPP) or N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD). The use of the MoO₃ layer also enhanced open-circuit voltages and power conversion efficiencies of the OSCs due to an increase in built-in potential. From results of stability test of hole-only α-NPD devices, we concluded that the OSC degradation occurs near the ITO/p-type layer interface and that the use of the MoO₃ layer can prevent the degradation at this interface.     

Epidemiology of genotypes of hepatitis C virus in Japanese patients with type C chronic liver diseases: a multi-institution analysis

Sixteen medical institutions in Japan collaborated in this study of the epidemiology of hepatitis C virus (HCV) genotypes. A total of 4176 patients with type C chronic liver disease, from the four main islands of Japan, were evaluated. Of those evaluated, 2794 had chronic hepatitis, 727 had liver cirrhosis and 655 had hepatocellular carcinoma. The HCV genotype of the patients was determined by an enzyme-linked immunosorbent assay based on serological genotype 1- and 2-specific recombinant peptides (SG-1 and SG-2, respectively) of the NS4 region. The prevalence of SG-1 and SG-2 HCV was similar in the four main islands of Japan. SG-1 HCV predominated in each disease category (69-76%). The percentage of patients with SG-1 HCV increased by 7%, while that of patients with SG-2 HCV decreased by 7%, as liver disease progressed in severity from chronic hepatitis to carcinoma (P < 0.001). Patients with either SG-1 or SG-2 had a similar mean age and history of blood transfusion. In conclusion, SG-1 HCV was found to predominate in Japan, and the HCV genotype was found to be related to the stage of hepatitis C disease.     

Clinical evaluation of a reagent for detection of DNA of Mycobacterium tuberculosis complex using the ligase chain reaction (LCR) method

We evaluated the clinical efficacy of LCR MTB, a reagent developed by Abbott in the USA, in the full automatic ligase chain reaction (LCR) for detection of DNA of M. tuberculosis complex using a thermostable ligase. Using 458 samples isolated from patients with tuberculosis, LCR was compared with a smear method and with a culture method, and was also compared with two other methods of gene amplification, MTD and Amplicor, using 340 and 200 of the 458 samples, respectively. The LCR method detected M. tuberculosis in 49.8% (228/458) of the samples, and was superior to the smear method (31.9%, 146/458) and the culture method (39.1%, 179/458) in sensitivity. The LCR method was also superior to the MTD and Amplicor methods; sensitivity were 37.9% (129/340) for MTD vs. 47.6% (162/340) for LCR, and 56.5% (113/200) for Amplicor vs. 59.5% (119/200) for LCR. These favorable results and the convenience of the LCR method, which enables rapid detection of target genes with a high degree of sensitivity, strongly suggest that LCR MTB is useful as a reagent for detection of M. tuberculosis using nucleic acid amplification.     

Evaluation of leak flow rate and jet impingement related to leak before break

Leak flow rate and jet impingement load are experimentally evaluated using very narrow and short artificial slits which simulate a through-wall fatigue crack. The following items are clarified in the experiments under BWR fluid conditions: (1) the leak flow rate from the rectangular slit is experimentally clarified and it agrees well with the analytical result when the estimated thermodynamic nonequilibrium parameter N in the present experiment is introduced; (2) the orifice effects are experimentally evaluated concerning the through-wall fatigue crack, in which the discharge coefficients C_D between 0.75 and 0.25 are obtained as a function of the exit to the stagnation area ratio A_e/A_o; (3) when very narrow and short slits are used in the jet impingement experiments, the maximum pressure on the target is higher than that of a large diameter pipe and it increases with the decrease of the flow path length to hydraulic diameter ratio L/D of the slit because of the thermodynamic nonequilibrium effect.     

Effect of mirror facets on lasing characteristics of distributed feedback InGaAsP/InP laser diodes at 1.5 µm range

The effect of mirror facets on lasing properties of distributed feedback (DFB) InGaAsP/InP laser diodes was studied theoretically and experimentally. A DFB laser with a window region was found to be suitable to examine the effect of mirror facets. The effective reflectivity of a window structure was calculated to be very small, typically as small as 0.03 percent for a few tens of micrometers of the window region. These small effective reflectivities were experimentally confirmed. Three kinds of DFB lasers, i.e., a double-window (DW), a single-window (SW), and a Fabry-Perot (FP), were discussed. Two modes with a separation corresponding to a so-called stopband appeared in a DW-DFB laser, in which almost no reflection at both ends was estimated. On the other hand, the threshold and the resonant wavelength of an SW- and an FP-DFB laser were found to be sensitive to the phases of corrugation at the facets. It turned out, however, that the mirror facet contributed to the single-mode operation due to an asymmetric resonant spectrum and to the reduction in the threshold. Although a low-threshold-current FP-DFB laser was experimentally obtained, the coincidence between the gain peak and the Bragg wavelengths was essential in this type. The SW-DFB laser seemed the most promising among the three types in terms of the stability of the single-mode operation.