Novel photoactive aggregates of rhodamine 6G: dequenched and quasi-stable aggregates induced by a dewetting process

Self-organized rhodamine 6G particles prepared by wetting/dewetting process of an ethanol solution on a hydrophilic glass surface exhibits fluorescence without quenching, showing a sharp linewidth of 2nm with a large redshift, which indicates an existence of dye aggregates, similar to J-aggregates, inside the particle. Polarized evanescent field excitation showed that the dye molecule's transition moment along the pi-conjugation was oriented unidirectionally within particles and parallel to the substrate surface. This deduced dye orientation showed correlation between adjacent, but separated, particles and pointed roughly 45 degrees off the dewetting direction. In contrast, the particles of another pi-conjugated NK1420 dye, J-aggregates of which grows easily from an oversaturated solution, showed dye orientation along the dewetting direction preferably, still indicating the effect of self-organization, however based on a different mechanism. An annealing procedure revealed that both aggregates are in quasi-stable states, which is consistent with the rapidness of the dewetting process that may lead to crystallization in nonequilibrium.     

Ion beam modification of TiO2 films prepared by Cat-CVD for solar cell

The effects of nitrogen ion bombardment on TiO₂ films prepared by the Cat-CVD method have been studied to improve the optical and electrical properties of the material for use in Si thin film solar cells. The refractive index n and the dark conductivity of the TiO₂ film increased with irradiation time. The refractive index n of the TiO₂ film was changed from 2.1 to 2.4 and the electrical conductivity was improved from 3.4 × 10^− 2 to 1.2 × 10^− 1 S/cm by the irradiation. These results are due to the formation of Ti-N bonds and oxygen vacancies in the film.     

New Approach for Macro Porous RB‐SiC Derived from SiC/Novolac‐type Phenolic Composite

A novel fabrication route to make macroporous silicon carbide (SiC) has been proposed in this study. The route is composed of the following two steps: the fabrication of porous α‐SiC/novolac‐type phenolic composite using hexamethylenetetramine (HMT) as a curing/blowing agent for the novolac monomer and a conventional reaction‐bonded (RB) sintering of the composite. The α‐SiC/novolac‐type phenolic composite was carbonized at 800°C for 2 h in N₂ gas and then reacted with the molten silicon at 1450°C for 30 min under vacuum, resulting in the macroporous RB‐SiC with an open porosity of 48% and relatively large pore size of ~110 μm. The compressive strength of the macroporous RB‐SiC was 113 MPa, which is relatively high compared to those reported for macroporous SiC of equivalent porosities and pore sizes.     

Deuterium NMR analysis of dimer liquid crystals

Summary Deuterium NMR measurements have been performed for dimer liquid crystals (DLC) having structures such as NC-O(CH₂)_nO-CN (CBA) with n=9, 10. Fully deuterated CBAs with n=9 and 10 exhibit, respectively, three and four splittings in the D-NMR spectra. By using partially deuterated samples, the signals corresponding to the largest splittings were found to include contributions from the - and -CD₂ groups. The origins of the rest of the signals were elucidated by the RIS method previously established. Characteristic properties of the nematic mesophase were estimated for CBA-10. The results were found to be consistent with those of the previous analysis on Griffin et al.'s DLC.     

Sulfur-bridged polycyclic aromatic compounds

When polycyclic aromatic hydrocarbons are heattreated with an excess amount of sulfur in evacuated closed tubing, they react with sulfur, liberating hydrogen sulfide; after removing unreacted sulfur, dark-colored compounds in the form of an amorphous solid are obtained. These compounds possess semiconductive properties; the electrical resistivity is greatly reduced from that of the original hydrocarbons. The ESR absorption of these compounds is characterized by the large g-value, which is due to sulfur-centered unpaired electrons.From these findings, with the results of chemical analysis, we can assume that the polycyclic aromatic nuclei crosslink with each other through the sulfur-bridges, which are good electron transport paths, and yield the aromaticity of the molecule. The sulfur-bridged polycyclic aromatic hydrocarbons can be considered as the structural model of chars and cokes. The ESR studies of a violanthrene-sulfur compound were carried out during its heat-treatment up to 1000°C.     

Deuterium NMR analysis of main-chain polymer liquid crystals

Summary Deuterium NMR measurements have been performed for main-chain polymer liquid crystals having structures such as {Ø-OC(O)-Ø-O(CD₂)_nO-Ø-C(O)O-Ø-O(CH₂)_nO}_x with n = 9, 10. D-NMR spectra obtained in the nematic mesophase are compared with those previously reported for the dimer liquid crystals of the type NC---O(CD₂)_nO---CN with n = 9, 10, Although resolutions are relatively poor in the polymer spectrum, the general profiles of the spectra were found to be similar to those of the corresponding dimer. The results of the RIS analysis suggest that the spatial configurations of the spacer are nearly identical between the dimer and polymer. It has been concluded that the observed enhancement in the quadru-polar splittings should arise largely from a higher orientational ordering of the molecular axis in the polymeric system.     

Random-coiled conformation of polypeptide chains

Summary Random-coiled conformation of poly(L-leucine), which has -branched side-chain, was theoretically analyzed by a conformational energy calculation based on intra-residue interactions. Calculated characteristic ratio 7.62 was obtained by using the transformation matrix statistically averaged over the entire side-chain conformational space of L-Leu residue. This value is smaller than those of poly(L-phenylalanine) (11.24) and poly(L-tyrosine) (12.33) which have -branched side-chain.     

Measuring the effect of police surveillance on the prevention of traffic accidents

An approach for estimating the effect of preventive measures taken against traffic accidents is presented. A simple stochastic model as to the process of accident occurrence is provided and the relationship among vulnerable behavior, collisions, and police surveillance is formalized. Here vulnerable behavior is defined as the state prior to the collision in the process of accident occurrence, and police surveillance is selected as one of the preventive measures against the accident.

The procedures by which the model can be applied in practice are shown for the case of intersection accidents, and the effects of some intersection surveillance forms on accident prevention are calculated. The results suggest that police surveillance which affects vulnerable behavior reduces accidents and that each collision category differently has the most effective surveillance form.

It is concluded that vulnerable behavior, which increases the likelihood of accident occurrence, provides a more sensitive safety measure than accidents.