Flow velocity profile of micro counter-current flows.

Flow velocity profiles of micro counter-current flow of aqueous and butylacetate phases in a microchannel having a width of 100 microm were measured by micro particle image velocimetry. In order to analyze the hydrodynamic characteristics of the counter-current flow, we derived a simple analytical model for the velocity profile. When flow rates of the aqueous and organic phases were 0.2 and 0.1 microl/min, the model agreed well with the experimental results. Predictions about the velocity profile will contribute to estimation of the extraction efficiency in the co-current and counter-current extraction process.     

On-chip thermal calibration with 8 CB liquid crystal of micro-thermal device

A temperature sensor integrated on a micro-device for biological experiments requires affordable, rapid and easy thermal calibration. However, such calibration cannot usually be done directly under the microscope, a fact that impedes biological experiments. We present in this paper an inexpensive and rapid method to achieve thermal calibration directly under the microscope. It is based on the use of a thermotropic liquid crystal: the 4-n-octyl-4-cyanobiphenyl (8 CB) exhibiting an isothermal phase change at 313 K that can be monitored optically. We demonstrate the advantages of this method by calibrating the temperature sensor integrated onto a micro-device.     

Effectiveness of a short training session for improving pipetting accuracy

The quality of diagnostic tests conducted by the Animal Quarantine Service (AQS) is critical to the safety of national livestock production. In procedures for tests such as polymerase chain reaction and enzyme-linked immunosorbent assay, measurement of tiny quantities of samples or reagents is quite common. Therefore, many efforts have been made to maintain the quality of micropipette operations, including routine calibration of equipment and training programs for operators. In this study, we developed a pilot training program to analyze the effects of training on pipetting accuracy, i.e., trueness and precision. The program involved a self-instruction A4-sized leaflet describing how to improve pipetting technique. Thirty-three staff members from seven AQS laboratories participated in the program. Each participant repeated sampling of 300 μL of distilled water 10 times before and after reading the leaflet, and the effects of training on the trueness and precision of the pipetting results were analyzed. To determine pipetting trueness, we examined the variation of the delivered volume from the target volume (300 μL) using the proportional odds mixture model. Our data demonstrated that participation in the training program and the level of experience with pipetting significantly improved trueness. Analysis of standard deviations of the ten samplings, as an indicator of precision, also showed that participation in the training program improves pipetting precision. Thus, our data supported the implementation of such simple, quick training sessions to improve pipetting trueness and precision in diagnostic laboratories.     

Total synthesis of epicoccamides A and D via olefin cross-metathesis

Epicoccamides A and D were synthesized through a route that utilizes fragment coupling via olefin cross-metathesis as a key step. The right-hand segment of the epicoccamides was synthesized by a tandem O-acylation–migration reaction, and the left-hand segments were stereoselectively synthesized through a modified version of Crich’s β-selective mannosylation. The previously assigned absolute configuration of the epicoccamide D was confirmed, and that of epicoccamide A was assigned as (5S,2′S) based on the NMR and CD spectra. This Letter provides the first example of the total synthesis of epicoccamide A.     

Untersuchung des Wassers

Ohne Zusammenfassung     

Simultaneous measurement of prolidase and prolinase activities in erythrocytes using an isotachophoretic analyser

The enantiomeric purity of the pharmaceutical D-penicillamine (I) has been determined by a novel high-performance liquid chromatographic technique involving the formation of 5,5-dimethylthiazolidine-4-carboxylic acid (III) by reaction of I with formaldehyde and separation of the optical antipodes by means of ligand exchange chromatography using the copper(II) complex of (2S,4R,2'RS)-4-hydroxy-1-(2'-hydroxydodecyl)proline, which is coated on a reversed-phase column. The limit of determination for the L-antipode is ca. 0.1%. The validation of the method is accomplished by comparison with an independent gas chromatographic procedure. Thirteen commercially available lots of I are shown to be of equally high enantiomeric purity (ca. 99.9%).