Optical Second Harmonic Generation and Relaxation Dynamics of Aligned Azo-Dyes in Sol-Gel Derived Organic-Inorganic Film

An Azo-dye doped organic-inorganic hybrid film was prepared by the sol-gel technique, and optical second-harmonic (SH) nonlinearities were measured as a function of the poling conditions. Azo-dye molecules dispersed in poly-vinylpyrrolidone were complexed with the hydrolyzed silicon-alkoxide. The Maker-fringe pattern composed of a fine oscillating pattern on a broad component, and the highest second-order nonlinear coefficient, d ₃₃, was 0.83 pm/V when poled at 175°C and 4 kV. The analysis of the decay curves of the SH intensities at 150–190°C predicted the relaxation time of about 3 years at room temperature.     

Hybridization of layered niobates with cationic dyes

The hybridization of two different types of organic polycations, 1,1’-dimethyl-4,4’-bipyridinium dications (methyl viologen, MV²⁺) and 5,10,15,20-tetrakis(N-methyl-pyridinium-4-yl)-21H,23H-porphine tetracations (TMPyP⁴⁺), into layered niobates was investigated to construct an efficient dye-modified semiconductor for solar conversion and storage. Two different methods were employed for the direct intercalation of the cationic species, i.e., conventional ion-exchange with K₄Nb₆O₁₇ · 3H₂O as the starting host and a novel acid-base neutralization method with H₄Nb₆O₁₇ as the starting host. These two methods showed totally different behavior and the characteristic features of both will be discussed in relation to the structure of the hybrid formed, the amount of absorption observed for the guest molecules and the intercalation rates. An analysis of the photo-induced electron-transfer reactions will also be discussed to show how control of the intercalation of guest molecules affects the photofunctionality of these unique hybrids.     

Transport of monosaccharides through a liquid membrane mediated by lipophilic alkaline earth metal complexes

Lipophilic alkaline earth metal complexes, prepared from the corresponding metal hydroxides and phosphoric acid diesters, are quite effective for the transport of some monosaccharides, especially ribose, across a chloroform liquid membrane under neutral conditions.     

A 40 GHz band SIS receiver using Nb/Al?AlOx/Nb array junctions

A 40 GHz band SIS mixer receiver has been built using Nb/Al–AlOx/Nb array junctions and a 4.3 K closed cycle helium refrigerator. The minimum conversion loss of the mixer is 2±1 dB and the single sideband receiver noise temperature (T_RX (SSB)) is as low as 110±10 K at 36 GHz. T_RX (SSB) is almost constant in the IF bandwidth of 600 MHz. The mixer saturation level is as high as 15 nW, which is comparable to the injected LO power.Nobeyama Radio Observatory (NRO), a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a cosmic radio observing facility open for outside users.     

Efficient 521 nm all-fiber laser: splicing Pr(3+)-doped ZBLAN fiber to end-coated silica fiber

We demonstrated a green all-fiber laser by splicing both ends of a Pr(3+)-doped ZBLAN fiber to silica fibers, whose ends were coated with a dielectric thin film. The output power and the slope efficiency were 322 mW and 53%, respectively, and the coupled pump power of the two blue GaN pump lasers in the silica fiber core was 652 mW. We estimated that the damage threshold of the spliced structure was at least 21 MW/cm2. This splicing technique should be applicable for other wavelengths and glass fibers having low melting temperatures.     

Role of intracellular contents to facilitate supercooling capability in beech (Fagus crenata) xylem parenchyma cells

In order to find the possible role of intracellular contents in facilitating the supercooling capability of xylem parenchyma cells, changes in the temperature of supercooling levels were compared before and after the release of intracellular substances from beech xylem parenchyma cells by DTA. Various methods were employed to release intracellular substances from xylem parenchyma cells and all resulted in a reduction of supercooling ability. It was concluded that the reduction of supercooling ability primarily resulted from changes of intracellular conditions, including the release of intracellular contents or their mixing with extracellular solutions, rather than due to changes of cell wall structures. It is therefore suggested that any unidentified intracellular contents may function to facilitate supercooling capability in xylem parenchyma cells.     

Synthesis and optical properties of new conjugated polymers composed of 1,3,4‐thiadiazole and 2,5‐dialkoxybenzene rings

Intramolecular cyclization of precursor polyhydrazides derived from hydrazine and four 2,5‐dialkoxyterephthalic acids by direct polycondensation with Lawesson's reagent afforded new conjugated polymers constituted of 1,3,4‐thiadiazole and 2,5‐dialkoxybenzene units. The polymers emitted bluish green light in solution and green light in solid state in spite of the coexistence of non‐cyclized hydrazide linkage in the backbones, the Stokes shifts being 91–138 nm in the solid state. It was suggested that these polymers have appropriate lengths of conjugation backbones based on the 1,3,4‐thiadiazole moiety.