A spectral Galerkin approximation of the Orr-Sommerfeld eigenvalue problem in a semi-infinite domain

Summary The convergence of a Galerkin approximation of the Orr-Sommerfeld eigenvalue problem, which is defined in a semi-infinite domain, is studied theoretically. In case the system of trial functions is based on a composite of Jacobi polynomials and an exponential transform of the semi-infinite domain, the error of the Galerkin approximation is estimated in terms of the transformation parametera and the numberN of trial functions. Finite or infinite-order convergence of the spectral Galerkin method is obtained depending on how the transformation parameter is chosen. If the transformation parameter is fixed, then convergence is of finite order only. However, ifa is varied proportional to 1/N ^{LE" BORDER="0">} with an exponent 0E" BORDER="0"><1, then the approximate eigenvalue converges faster than any finite power of 1/N asNLINE" BORDER="0">LE" BORDER="0">. Some numerical examles are given.     

Micro construction of poly(epsilon-caprolactone)/poly(L-lactic acid) blend film by solution casting under microwave irradiation

The micro construction of poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLLA) blend films fabricated by solution casting under microwave irradiation was investigated by selective enzymatic degradation and scanning electron microscopy (SEM). The results were totally different from the blends obtained by conventional methods. The blend was more homogeneous and the PCL continuous phase more compact as no spherulites and tiny zone separation were observed from the film surface and no PCL network was observed inside the film, and the degradation of a PCL plank by Pseudomonas lipase was significantly retarded. The distributed PLLA micro spheres were enlarged and amorphous. The thermal behavior of the blend by microwave heating revealed that PCL and PLLA underwent a melting process, which induced the variations of the PCL phase and PLLA spheres. The weight loss caused by degradation of the PCL/PLLA blend obtained by conventional methods (B50c) is greater than that of the blend obtained by microwave methods (B50m), which reflects the change in morphology from a loose PCL network (B50c) to a dense PCL plank (B50m).     

DIRECT SOMATIC EMBRYOGENESIS AND PLANT REGENERATION FROM PROTOPLAST-DERIVED CELLS OF WHEAT (Triticum aestivum L.)

Protoplasts were isolated from embryogenic calli derived from immature embryos ofwheat (Triticum aestivum L. cv. Jinan 177). The protoplasts were cultured in NMB mediumsupplemented with 1mg/L 2,4- D and 500mg/l casein hydrolysate (CH). The regenerated cellsfrom protoplasts divided to form somatic embryos directly. The somatic embryos grown to1.5- 2 mm in size directly developed into complete plants on solid MB medium without hor-mones.     

The use of chiral interaction reagents in the separation of D(−)-and L(+)-ascorbic acid by ion interaction reversed-phase HPLC

Summary An HPLC reversed-phase ion interaction reagent method is presented, which makes use of chiral compounds as the interaction reagents. By employing the optical isomeric forms of malic, tartaric and mandelic acids as the interaction reagents, a good separation of D(−) and L(+) ascorbic acid has been achieved. The method has also been applied to the identification of vitamin C in some medical formulations. The separation of te enantiomeric forms of DL malic acid has been attempted and a shor discussion is presented about the elution sequence in chromatographic separation of D- and L-enantiomers.     

L-histidine decarboxylase as a probe in studies on histamine

Because the Falck-Hillarp formaldehyde fluorescence method, which was superbly applied to identify catecholaminergic and serotonergic neurons, is not applicable to histamine, the first author (T.W.) developed an antibody to L-histidine decarboxylase (HDC) for identification of the histaminergic neuron system in the brain. The anti-HDC antibody was of great use for mapping the location and distribution of this histaminergic neuron system. (S)-alpha-fluoromethylhistidine, a specific and potent irreversible inhibitor of HDC, was also very useful in studies on functions of the neuron system. The activity of HDC is increased by various agents, treatments, and physiological conditions. We found new compounds that increased HDC activity (i.e., tetradecanoylphobol acetate (TPA), other tumor promoters, and staphylococcal enterotoxin A); and using mast cell-deficient mutant (W/W(v)) mice, we obtained evidence that this increase occurred in macrophages. To further characterize the mechanism of increases in HDC activity, the second author (H.O.) cloned human HDC cDNA and a human HDC gene. In studies on the regulation mechanism of the HDC gene, which is expressed only in limited types of cells such as mast cells, enterochromaffin-like cells in the stomach, cells in the tuberomammillary nucleus of the brain, and macrophages, CpG islands in the promoter region of the HDC gene were found to be demethylated in cells expressing the gene, whereas they are methylated in other cells that do not express the HDC gene. In collaboration with many other researchers, we developed HDC knockout mice. The resulting research is producing a lot of interesting findings in our laboratory as well as in others. In summary, HDC has been and will be useful in studies on functions of histamine.     

Xyloccensin L, a novel limonoid from Xylocarpus granatum

The isolation and structure elucidation of xyloccensin L from the stem bark of Xylocarpus granatum is described. Xyloccensin L is a highly oxidized heptacyclic A, B, D-seco limonoid with an α-8, 30-epoxy ring and a rare 1, 29 oxygen bridge.     

Simultaneous determination of noradrenaline and dopamine in Portulaca oleracea L. by capillary zone electrophoresis

A simple and rapid capillary electrophoretic method was developed for the simultaneous determination of noradrenaline (NA) and dopamine (DA) in Portulaca oleracea L. The buffer solution used in this method was 40 mM tris (hydroxymethyl) aminomethane (Tris)-H3PO4 at pH 2.00 containing 15% methanol. The effects of pH value, organic modifier, and applied voltage were investigated. The linear ranges of NA and DA were 0.5-100 microg/mL (r=0.9952) and 6.25-200 microg/mL (r=0.9992), respectively. The relative standard deviations of the corrected peak area were 6.73% and 4.26%, respectively. NA and DA in Portulaca oleracea L. were simultaneous determined successfully within 5.6 min. In this way, the contents of NA and DA in different parts (stem, leaves, and seeds) of P. oleracea L. and in different extracts of leaves with different solvents (distilled water, 50% methanol, and methanol) were studied.     

Mono- and Dioses of Glycyrrhiza glabra Root

Simple sugars were isolated from the ethanol extract of Glycyrrhiza glabra L. root. The component composition of the carbohydrate fraction was established using GC-MS (gas-chromatographic separation and mass-spectrometric analysis).