Chips and Qi: microcomponent-based analysis in traditional Chinese medicine

Over the last 50 years or so Traditional Chinese medicine (TCM) has been subject to intensive basic and clinical research. Although the effectiveness and remarkable safety of TCM have been documented after controlled clinical studies, there are several herbal and animal parts that are toxic or difficult to identify. DNA polymorphism-based assays have recently been developed for the identification of herbal medicines. In this approach, small amounts of DNA are amplified by the polymerase chain reaction and the reactions products are analyzed by gel electrophoresis, sequencing, or hybridization with species-specific probes. With the DNA based identification of TCM materials as an example, chip-based analytical micro devices were developed with the goal of fabricating an integrated device that will enable sample preparation, amplification, and analysis on a single microchip-based device ("lab-on-a-chip"). The application of a silicon-based polymerase chain reaction microreactor and a DNA microarray for the DNA sequence-based identification of toxic medicinal plants is reported here.     

Phototitrimetric determination of sulfhydryl compounds witho-hydroxymercuribenzoic acid using dithiofluorescein as an indicator

Summary A phototitrimetric method for the determination of sulfhydryl compounds in an aqueous medium is described.o-Hydroxymercuribenzoic acid is used as a titrant with dithiofluorescein as an indicator. Disulfide amino acids like cystine and-substituted DL-cystines are reduced with sodium borohydride before titration. All amino acids were determined to the limit of 1.0mol with an error of less than 4%. A selective phototitrimetric method for the determination of-mercaptopyruvate in presence of cysteine and glutathione is described. This method can be extended to the microdetermination of other similar sulfhydryl compounds in biological materials.

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Zusammenfassung Eine phototitrimetrische Bestimmungsmethode für Sulfhydrylverbindungen in wäßriger Phase wurde beschrieben. Als Maßflüssigkeit diento-Hydroxymercuribenzoesäure, als Indikator Dithiofluorescein. Aminosäuredisulfide wie Cystin und-substituierte DL-Cystine werden vor der Titration mit Natriumborhydrid reduziert. Alle Aminosäuren lassen sich bis zur Größenordnung von 1,0Mol mit einem Fehler von weniger als 4% bestimmen. Eine selektive phototitrimetrische Bestimmung von-Merkaptopyruvat in Gegenwart von Cystein und Glutathion wurde angegeben. Das Verfahren läßt sich auch für andere Sulfhydrylverbindungen in biologischem Material anwenden.

     

A multiple regression model for urban traffic noise in Hong Kong

This article describes the roadside traffic noise surveys conducted in heavily built-up urban areas in Hong Kong. Noise measurements were carried out along 18 major roads in 1999. The measurement data included L10, L50, L90, Leq, Lmax, the number of light vehicles, the number of heavy vehicles, the total traffic flow, and the average speed of vehicles. Statistical analysis using the analysis of variance (ANOVA) and Tukey test (p<0.05) reveals that the total traffic flow and the number of heavy vehicles are the most significant factors of urban traffic noise. Multiple regression was used to derive a set of empirical formulas for predicting L10 noise level due to road traffic. The accuracy of these empirical formulas is quantified and compared to that of another widely used prediction model in Hong Kong--the Calculation of Road Traffic Noise. The applicability of the selected multiple regression model is validated by the noise measurements performed in the winter of 2000.     

Local convergence of quasi-Newton methods for B-differentiable equations

We study local convergence of quasi-Newton methods for solving systems of nonlinear equations defined by B-differentiable functions. We extend the classical linear and superlinear convergence results for general quasi-Newton methods as well as for Broyden's method. We also show how Broyden's method may be applied to nonlinear complementarity problems and illustrate its computational performance on two small examples.     

The effects of sample preparation methods on the variability of the electrospray ionization response for model drug compounds

A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd.     

Gamma-ray spectroscopy with relativistic exotic heavy-ions

Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors (segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed.     

Percolative transport in the vicinity of charge-order ferromagnetic transition in a hole-doped manganite

We report measurements of non-linear charge transport in epitaxial (La_1−x Pr _x )_0.7Ca_0.3MnO₃ thin films fabricated on (100) oriented SrTiO₃ single crystals by pulsed laser deposition. The end members of this series, namely Pr_0.7Ca_0.3MnO₃ and La_0.7Ca_0.3MnO₃ are canonical charge-ordered (CO) and ferromagnetic manganites, respectively. The onset of the CO state in Pr_0.7Ca_0.3MnO₃ is manifested by a pronounced insulating behavior below ∼ 200 K. The CO state remains stable even when a large (∼ 2×10⁵ V/cm) electric field is applied across the thin film samples. However, on substitution of Pr with La, a crossover from the highly resistive CO state to a state of metallic character is observed at relatively low electric fields. The current-voltage characteristics of the samples at low temperatures show hysteretic and history dependent effects. The electric field driven charge transport in the system is modelled on the basis of an inhomogeneous medium consisting of ferromagnetic metallic clusters dispersed in a CO background.