A new synthesis of fervenulin 4-oxide

The reaction of 1,3-dimethyl-6-hydrazino-5-nitrosouracil (1) with Vilsmeier reagent (dimethylformamide-phosphorus oxychloride) afforded fervenulin 4-oxide (II) in good yield.     

Synthesis of visible-light reactive TiO2−xNy photocatalyst by mechanochemical doping

Yellowish TiO_2−xN_y was prepared by a novel mechanochemical nitrogen-doping method. The samples were prepared by a high-energy ball milling of P25 titania with different nitrogen sources such as hexamethylenetetramine, urea or ammonium carbonate, followed by calcination in air at 400 °C. The high mechanical energy accelerated the phase transformation of anatase to rutile, while the existence of the nitrogen reagents tended to block the transformation. The calcination treatment slightly increased the crystallinity of the prepared titania. The prepared powders possessed two absorption edges at around 400 and 540 nm and showed an excellent photocatalytic ability for the oxidation of nitrogen monoxide under visible light irradiation. Under the irradiation of visible light with wavelengths of >510 nm, nitrogen monoxide could be continuously removed by the nitrogen doped titania prepared from the P25 titania-hexamethylenetetramine mixture, while the powders prepared using urea and ammonium carbonate as nitrogen sources showed lower activities. This mechanochemical technique might be widely useful for doping oxides with nonmetallic elements.     

Maximal subbundles of vector bundles on a curve

For a rank 2 vector bundle E on a non-singular projective curve of genus g, the theorem of Nagata tells us that deg E-2 max deg Fg where the maximum is taken over all sub line bundles F of E. We generalize this result to vector bundles of arbitrary rank.     

The effect of crystalline phase on the fluorescence characteristics of solid cyclohexane and bicyclohexyl

Emission from cyclohexane and bicyclohexyl solids has been found to critically depend on their crystalline structure. The emission spectrum of cyclohexane suddenly blue-shifts 2900 cm^?1 on cooling below its solid—solid phase transition temperature (?87.1°C). The bicyclohexyl emission intensity sharply decreases on freezing to solid and then again sharply recovers at a heretofore unreported phase transition temperature (≈ 0°C) with the spectrum 2500 cm^?1 blue-shifted from that of the liquid. The results are discussed utilizing the partial Rydberg nature of the excited cycloalkane states.     

BEHAVIOR OF HETEROEXCIMER SYSTEMS IN SINGLE BILAYER LIPOSOMES

Abstract— Behavior of heteroexcimers formed between pyrene moieties incorporated at varying depths from the charged surface of vesicles and exogeneous N, N-dimethylaniline during the lifetime of excited pyrene moiety have been investigated by means of fluorescence measurements and laser photolysis. Fluorescence studies show that the fluorescence quenching kinetics in liposomes is rather similar to that in homogeneous bulk solutions, in contrast to the case of ordinary micellar solutions. Weak heteroexcimer fluorescence as well as transient absorption bands of ion radicals produced as a consequence of electron transfer from the amine to the excited pyrenyl group were observed. Comparison of the present results with those in homogeneous solutions indicates that the polar environment where dielectric constant is as large as 10 is attained in the hydrocarbon core of the liposomes. The polar environment of the fatty acid chains suggests the presence of water molecules penetrated into the hydrocarbon core.     

Precipitation behavior of 1,1,Di-(p-hydroxyphenyl)-cyclohexane clathrate crystals from acetone solutions containingd-limonene

The precipitation behavior of 1,1-di(p-hydroxyphenyl)cyclohexane (DHC) from acetone solutions containing d-Limonene (1-methyl-4(I-methylethenyl)cyclohexene) was studied. From the pure acetone solution or the solutions containing a small amount of d-Limonene crystals (B) precipitated, which clathrate only acetone with a guest/host (G/H) molar ratio of 1.0. However, when thed-Limonene concentration is increased to more than ca. 2 mol/L, crystals (A) precipitated which had a different habit from the B crystals. In the A crystalsd-Limonene is clathrated together with a large amount of acetone and the G/H value ofd-Limonene increases with the concentration in the solution up to the maximum value of 0.2. As the diffraction patterns of the A and B crystals are similar, it is assumed that a part of the acetone molecules in the B crystals are replaced byd-Limonene molecules. The acetone in the A crystals escapes rapidly, but thed-Limonene remains for a long time. This may indicate that the large molecule ofd-Limonene cannot diffuse rapidly within the host lattice owing to three-dimensional hindrance. It was clear that the solubility of the A crystals is higher than that of the B crystals and the transformation from the'metastable A to the stable B crystals proceeds during the crystallization of A crystals.     

Isotactic poly(acrylonitrile) via ultraviolet irradiation of acrylonitrile-urea canal complex

Isotactic poly(acrylonitrile) (PAN) has been prepared by means of a conventional ultraviolet (UV) irradiation apparatus without γ-ray sources; an acrylonitrile-urea canal complex was directly formed at the surface of the UV (Hg) emission tube at low temperatures (～ ?78°C). When the complex was UV-irradiated at this temperature, a stereoregular polymer was formed in the canal. The ¹³C-NMR analyses indicate that (1) these PAN are rich in isotactic configuration, (2) the extent of the isotactic triad is in the range of 56?71%, and (3) the penultimate unit effect, 4 (mm) (rr)/(mr)², is linearly correlated with the ultimate unit effect, (mm)/(rr). From the plots of log{4(mm)(rr)/(mr)²} vs log{(mm)/(rr)}, the anomaly in the polymerization of AN is discussed. The molecular characteristics of the UV canal PAN such as molecular weight, etc., were briefly noted. © 1995 John Wiley & Sons, Inc.     

An Unusual Mixed-guest Inclusion Compound. Crystal Structures of the Host Compound Hexakis(3-hydroxy-3,3-diphenylprop-2-ynyl)benzene, and its Inclusion Compound with Acetonitrile and Benzene

The crystal structures of the -phase of hexakis(3-hydroxy-3,3-diphenylprop-2-ynyl)benzene (1), and its inclusion compound with acetonitrile and benzene (2) have been determined by single crystal diffraction. 2 was further characterised by nuclear magnetic resonance spectroscopy, and thermal analysis. The inclusion of benzene by this host appears to depend on the presence of acetonitrile.