Determination of ten sulfonyl urea herbicides in unpolished rice by solid-phase extraction cleanup and LC-diode array detection

A liquid chromatographic (LC) method with diode array detection (DAD) was developed for screening of 10 sulfonyl urea herbicide residues in unpolished rice. The investigated herbicides were azimsulfuron, bensulfuron-methyl, chlorimuron-ethyl, chlorsulfuron, ethoxysulfuron, flazasulfuron, imazosulfuron, metsulfuron-methyl, pyrazosulfuron-ethyl and tribenuron-methyl. Acetonitrile-water (2:1) extracts of rice samples were cleaned up with solid-phase extraction cartridges (octadecylsilane-bonded silica (ODS) and graphitized carbon black (GCB)). Three fractions of the GCB eluate were taken for analysis using 3 separate injections in order to avoid interference in LC-DAD analysis and to reduce analyte coelution problems. Recoveries from rice samples fortified with the 10 herbicides at 0.05 and 0.2 microgram/g ranged from 46.6 to 119.6%, and coefficients of variation were 3.1-12.6%. The quantitation limits were 0.01-0.02 microgram/g.     

A new analytical method for gonyautoxins based on postcolumn HPLC

A new ion-pairing high-performance liquid chromatography (HPLC) method on a C30 column with a volatile mobile phase was developed to separate the gonyautoxin group (GTXs) from contaminants, allowing the utilization of liquid chromatography/mass spectrometry (LC/MS) with higher performance. A mobile phase consisting of 5 mmol/L heptafluorobutyric acid and 2% acetonitrile in 10 mmol/L ammonium acetate was adopted for separation of GTXs because the C30 column strongly retains GTXs under acidic conditions. The newly adopted method could efficiently separate GTXs from contaminants, especially in the toxic short-necked clam, whereas the routine HPLC so far used has poor resolution to separate GTXs from unknown interfering substances. In our method, GTXs were eluted in the order of GTX5, GTX3, GTX4, GTX2 and GTX1 from the C30 column, and were successfully determined by sonic spray ionization mass spectrometry (SSI-MS) with high sensitivity. This method is characterized by the combination of HPLC using a fluorescence detection system for PSP, and SSI-MS for measurement of the mass number.     

Characterization of the supermirror hard-x-ray telescope for the InFOCmuS balloon experiment

A hard-x-ray telescope is successfully produced for balloon observations by making use of depth-graded multilayers, or so-called supermirrors, with platinum-carbon (Pt/C) layer pairs. It consists of four quadrant units assembled in an optical configuration with a diameter of 40 cm and a focal length of 8 m. Each quadrant is made of 510 pieces of coaxially and confocally aligned supermirrors that significantly enhance the sensitivity in an energy range of 20-40 keV. The configuration of the telescope is similar to the x-ray telescope onboard Astro-E, but with a longer focal length. The reflectivity of supermirrors is of the order of 40% in the energy range concerned at a grazing angle of 0.2 deg. The effective area of a fully assembled telescope is 50 cm2 at 30 keV. The angular resolution is 2.37 arc min at half-power diameter 8.0 keV. The field of view is 12.6 arc min in the hard-x-ray region, depending somewhat on x-ray energies. We discuss these characteristics, taking into account the figure errors of reflectors and their optical alignment in the telescope assembly. This hard-x-ray telescope is unanimously afforded in the International Focusing Optics Collaboration for muCrab Sensitivity balloon experiment.     

High density culture of Coptis japonica cells increases berberine production

A high density culture method was devised to improve the yield of berberine from highly productive cells of Coptis japonica. By adjusting aeration and stirring, Coptis cells were cultured at densities of up to 75 g dm^?3 (dry weight) in a culture tank fitted with a hollow-paddle type stirrer. Whereas a maximum density of 30 g dm^?3 of C. japonica cells could be used in ordinary batch culture, 48 g dm^?3 could be used in a fed-batch culture in which the amounts of the nutrients in the medium were made proportional to the density of the inoculum. Moreover, in fed-batch culture done with modified medium, the composition of which had been determined from the amounts of components incorporated in cells grown at the usual density for ordinary batch culture, the cell yield was improved to 55 g dm^?3 and the berberine yield to 3.5 g dm^?3.     

Two distinct pathways for the formation of hydroxy FA from linoleic acid by lactic acid bacteria

Twenty-three of 86 strains of lactic acid bacteria transformed linoleic acid into hydroxy FA. Two distinct conversion pathways were in operation. Two strains of Lactobacillus acidophilus and a strain of Pediococcus pentosaceus produced 13(S)-hydroxy-9-octadecenoic acid [13(S)-OH 18∶1] and 10,13-dihydroxyoctadecanoic acid (10,13-OH 18∶0) as main and minor products, respectively, whereas 13 strains, including L. casei subsp. casei, L. paracasei subsp, paracasei, L. rhamnosus, L. lactis subsp. cremoris, and Streptococcus salivarius subsp. thermophilus produced 10-hydroxy-12-octadecenoic acid (10-OH 18∶1). Seven strains of L. plantanum converted linoleic acid to 10-hydroxyoctadecanoic acid (10-OH 18∶0) through 10-OH 18∶1 Linoleic acid at 2 g/L was converted by L. acidophilus LFO13951^T to 1.3 g of 13(S)-OH 18∶1 and 0.09 g of 10,13-OH 18∶0 in 7 d. Lactobacillus paracasei subsp. paracasei JCM 1111 produced 10-OH 18∶1 in 91% yield, and L. plantarum JCM 8341, 10-OH 18∶0 in 59% yield from linoleic acid (2 g/L) under optimal conditions. To our knowledge, this is the first report on the production of 13(S)-OH 18∶1 by lactic acid bacteria other than ruminal bacteria, and of 10,13-OH 18∶0 by any bacteria.     

Limits on the accuracy of 3-D thickness measurement in magnetic resonance images--effects of voxel anisotropy

Measuring the thickness of sheet-like thin anatomical structures, such as articular cartilage and brain cortex, in three-dimensional (3-D) magnetic resonance (MR) images is an important diagnostic procedure. This paper investigates the fundamental limits on the accuracy of thickness determination in MR images. We defined thickness here as the distance between the two sides of boundaries measured at the subvoxel resolution, which are the zero-crossings of the second directional derivatives combined with Gaussian blurring along the normal directions of the sheet surface. Based on MR imaging and computer postprocessing parameters, characteristics for the accuracy of thickness determination were derived by a theoretical simulation. We especially focused on the effects of voxel anisotropy in MR imaging with variable orientation of sheet-like structure. Improved and stable accuracy features were observed when the standard deviation of Gaussian blurring combined with thickness determination processes was around square root of 2/2 times as large as the pixel size. The relation between voxel anisotropy in MR imaging and the range of sheet normal orientation within which acceptable accuracy is attainable was also clarified, based on the dependences of voxel anisotropy and the sheet normal orientation obtained by numerical simulations. Finally, in vitro experiments were conducted using an acrylic plate phantom and a resected femoral head to validate the results of theoretical simulation. The simulated thickness was demonstrated to be well-correlated with the actual in vitro thickness.     

Frequency stabilization of a laser diode with use of light-induced birefringence in an atomic vapor

We present a simple modulation-free technique to stabilize a laser frequency to the Doppler-free spectra of an atomic vapor. Polarization spectroscopy with use of a balanced polarimeter allows us to obtain a background-free dispersion signal suitable for high-speed and robust frequency stabilization. We employed the method to the 5S(1/2) F = 2 --> 5P(3/2) F' = 3 transition of 87Rb atoms. The achieved feedback bandwidth was approximately 100 kHz, and an efficient suppression of the frequency noise in a laboratory environment was attained.