Nine new secoiridoid glucosides from Jasminum nudiflorum

Phytochemical study of the leaves of Jasminum nudiflorum has led to the isolation of nine new secoiridoid glucosides, jasnudiflosides F-L (1-7), nudifloside D (8) and isooleoacteoside (9). The structures of these compounds were elucidated on the basis of chemical and spectroscopic evidence.     

Control of light pulse propagation with only a few cold atoms in a high-finesse microcavity

Propagation of a light pulse through a high-Q optical microcavity containing a few cold atoms (N<10) in its cavity mode is investigated experimentally. With less than ten cold rubidium atoms launched into an optical microcavity, up to 170 ns propagation lead time ("superluminal"), and 440 ns propagation delay time (subluminal) are observed. Comparison of the experimental data with numerical simulations as well as future experiments are discussed.     

Facile synthesis of chiral glycine using D-glucose as a chiral template

A facile synthetic method of chiral glycine and a new access to chiral acetic acid based on a concept of chirality transfer from glucose are described.     

An HPLC assay of hydroxyl radicals by the hydroxylation reaction of terephthalic acid

An HPLC assay for hydroxyl radicals is described. The hydroxyl radical was trapped by terephthalic acid (non-fluorescent), and 2-hydroxyl terephthalic acid (fluorescent) was quantitated by HPLC-fluorescence detection. At a terephthalic acid concentration of 4.25 mmol/L, the hydroxyl radical formed in the Fenton reaction was successfully assayed in the concentration range of hydrogen peroxide of 2.5-50 micro mol/L, where the concentration of Fe(II) was 50 micro mol/L. The fluorescence of 2-hydroxy terephthalate was stable at 24 h, and its detection limit by this method was 5 nmol/L (100 fmol).     

Non-steady state solidification of the Nd-123 superconducting oxides

Crystal growth of the melt-textured bulk Nd_1+xBa_2−xCu₃O_6+d (Nd123) superconducting oxides was investigated by employing isothermal undercooling solidification with hot-seeding in air. From the relationship between growth length and holding time, the Nd123 crystal was found to have almost stopped growing after a certain growth period, while the growth length increased proportionally to the holding time at an early stage of the crystal growth. As a result of quantitative analysis for the Nd123 crystal of which solidification was terminated, the distribution of the Nd/Ba substitution was observed to decrease in the Nd123 single crystal matrix from the seed crystal to the edge of the Nd123 crystals. Also, the substitution content at the edge of the Nd123 crystal, which corresponds to that at the final stage of the crystal growth, was found to be in good agreement with the minimum substitution of the Nd123 solid solution phase in the equilibrium phase diagram at this process temperature. These compositional changes could be explained using the equilibrium phase diagram as associated with the solid solution formation, which is responsible for the non-steady state solidification of the Nd123 crystals even for the isothermal undercooling processing.     

Mevashuntin, a novel metabolite produced by inhibition of the mevalonate pathway in Streptomyces prunicolor

Inhibition of the mevalonate pathway by an HMG-CoA reductase inhibitor, mevalotin, in Streptomyces prunicolor possessing both mevalonate and MEP pathways resulted in the production of a new metabolite mevashuntin that consisted of conjugated thiazolone and pyranonaphthoquinone moieties.     

Optically driven actuators using poly(vinylidene difluoride)

Optically driven actuators have a feature of a non-contact method supplied by light energy. A new method is proposed with three poly(vinylidene difluoride) (PVDF) cantilevers as the legs and a polymer film as the body. The PVDF cantilevers are coated with silver on one surface. When one side of the cantilever is irradiated by a laser beam, an electric field is produced along a cross-section of the cantilever by the pyroelectric effect and a mechanical displacement occurs by the piezoelectric effect. Its response time and its generated force are measured experimentally. Two types of optically driven actuators using PVDF film are proposed to move using different characteristics.     

Methanol vapor‐induced morphology and current–voltage characteristic changes in a cast‐coated nafion film/interdigitated microarray electrode

Methanol vapor‐induced membranous changes in a cast‐coated Nafion thin film were studied through current–voltage (I–V) characteristics with an interdigitated microarray (IDA) electrode and atomic force microscopy (AFM). The obtained I–V curves showed that the as‐prepared Nafion film was stable under humidified nitrogen gas; however, the I–V profile dramatically changed with exposure to methanol vapor. Next, the morphology of the film was compared before and after methanol exposure with AFM images. On the basis of our observations, we found that the as‐prepared film had an irregularly complicated microstructure, whereas the structure became homogeneous in appearance after 30 min of exposure to methanol gas. The alternating‐current conductivity data, showing almost the same magnitude before and after exposure, strongly suggested that the I–V profile shift was based on a change in an electrode reaction mechanism induced by a change in the junction at the Nafion/IDA electrode interface. Furthermore, the methanol vapor‐pre‐exposed Nafion was stable for further exposure to methanol vapor, water vapor, or both. With the stabilized film used in combination with the IDA electrode, a reversible change in the magnitude of the current was observed when the methanol/water vapor ratio was varied. This indicated that the electrode reaction had good reproducibility after the treatment. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1103–1109, 2002