In-crystal and surface charge transport of electric-field-induced carriers in organic single-crystal semiconductors

Gate-voltage dependence of carrier mobility is measured in high-performance field-effect transistors of rubrene single crystals by simultaneous detection of the longitudinal conductivity sigma(square) and Hall coefficient R(H). The Hall mobility mu(H) (identical with sigma(square)R(H)) reaches nearly 10 cm(2)/V s when relatively low-density carriers (<10(11) cm(-2)) distribute into the crystal. mu(H) rapidly decreases with higher-density carriers as they are essentially confined to the surface and are subjected to randomness of the amorphous gate insulators. The mechanism to realize high carrier mobility in the organic transistor devices involves intrinsic-semiconductor character of the high-purity organic crystals and diffusive bandlike carrier transport in the bulk.     

Increase in aminobutyrate aminotransferase and cholineacetyltransferase in cerebrum of aged rats

We previously reported an increase in aminobutyrate aminotransferase (GABA-T) activity in the cerebrum of Alzheimer patients. In the present study, we investigated whether such findings are common in the usual aging process as well. We examined the activity of various enzymes, which were examined in the previous study, in the cerebrum of Wistar-Kyoto rats and spontaneously hypertensive rats. In the two strains, we compared the enzyme activities between the two groups of animals, 5 weeks and 13 weeks of age. In both strains, the older animals had significantly higher activities of GABA-T and choline acetyltransferase (ChAc-T). In spite of other enzymatic changes coexisting, the above two enzymes were suggested by discriminant function analysis to be playing a major role in the multiple enzymatic changes in the cerebrum of the animals.     

Synthesis and fundamental properties of methacrylate polymer containing five-membered cyclic trithiocarbonate group

4-(1,3-Dithia-2-thioxocyclopenthyl)methacrylate (TCMA), containing the five-membered trithiocarbonate moiety, was prepared from glycidyl methacrylate (GMA) through 2,3-epithiopropyl methacrylate (ETMA). At first step, GMA was converted to ETMA by the reaction using thiourea. At second step, ETMA was reacted efficiently with carbon disulfide in the presence of a catalytic amount of 1,2-dimethyltetrahydropyrimidine to give TCMA. The polymerization of TCMA proceeded under standard radical conditions to give the polymeric TCMA in 94% yield. The copolymerizations of TCMA with ethyl acrylate (EA) or acrylonitrile (AN) were conducted by changing the feed molar ratios of the monomers, in which the corresponding copolymers were obtained in over 83% yields. In addition, the obtained polymers showed the high values of refractive index over ca. 1.6 due to the presence of the cyclic trithiocarbonate structure.     

A rigid C3v-symmetrical host for saccharide recognition: 1,3,5-tris(2-hydroxyaryl)-2,4,6-trimethylbenzenes

A rigid C(3v)-symmetrical host molecule, syn-1,3,5-tris(2-hydroxy-5-pentylphenyl)-2,4,6-trimethylbenzene, was readily obtained via Suzuki coupling and thermal atropisomerization. The host molecule effectively associated with various saccharides by multipoint hydrogen bonds, whereas its anti-atropisomer and analogue lacking in methyl groups showed much weaker association with saccharides. Thermodynamic analyses suggested that the difference of the association strength was caused by entropic factors.     

Fabrication of spatial walk-off polarizing film exhibiting a large split angle by oblique silicon deposition

A spatial walk-off polarizing film with a large split angle was fabricated by use of the oblique deposition method. The film is composed of slanted needlelike microcolumns of a-Si that are separated by resultant fine voids. The polarization-splitting characteristics of the film were clearly observed. The maximum split angle at a wavelength of 1.55mum was as large as 20 degrees , more than three times greater than those of existing polarizers such as those constructed of rutile and calcite.