On-line continuous monitoring of glucose or lactate by ultraslow microdialysis combined with a flow-through nanoliter biosensor based on poly(m-phenylenediamine) ultra-thin polymer membrane as enzyme electrode

A miniaturised flow-through biosensor with a cell volume of only a few nanoliters was developed in our laboratory. The biosensor can be directly coupled to a microdialysis or ultrafiltration probe. Sampling and continuous on-line monitoring can thus be carried out at submicroliter levels and as a consequence quantitative recoveries of the analyte of interest are achieved. Via this method excessive calibration procedures, as are necessary with conventional microdialysis, are avoided. Here, the construction and the performance of such a biosensor for the continuous on-line monitoring of glucose and lactate will be presented. The biosensor is based on the amperometric detection of hydrogen peroxide after conversion of the analyte of interest by an immobilised oxidoreductase enzyme. Immobilisation of the enzyme is performed through electropolymerisation of m-phenylenediamine. Strategies to improve the performance (e.g. linearity, selectivity and stability) of the miniaturised biosensor are discussed and ex vivo and in vivo experiments carried out thus far demonstrate the potential of this miniaturised flow-through biosensor.     

Super transfer in doped LaFeO3

The effects of doping the orthoferrite LaFeO₃ with Ga, Ni, Cr, Sc and Al on the hyperfine fields at the⁵⁷Fe nuclei are investigated and discussed. The dependence of the magnetic hyperfine field at 4.2 K on the kind of nearest neighbour can be described in terms of a supertransfer model based upon the LCAO method.     

Prenylindoles from Tanzanian Monodora and Isolona species

6-(3-Methyl-but-2-enyl)-1,3-dihydro-indol-2-one, annonidine F [3-[6-(3-methyl-but-2-enyl)-1H-indolyl]-6-(3-methyl-but-2-enyl)-1H-indole], 1H-indole-5-carbaldehyde, 6-(3-methyl-2-butenyl)-1H-indole, 6-(3-methyl-buta-1,3-dienyl)-1H-indole, 6-(4-oxo-but-2-enyl)-1H-indole and 3-geranylindole were isolated from Monodora angolensis (Annonaceae) while 3-(1,1-dimethyl-but-2-enyl)-5-(3-methyl-but-2-enyl)-1H-indole (caulidine A), 4-[3-(1,1-dimethyl-but-2-enyl)-1H-indol-5-yl]-but-3-en-2-one (caulidine B), 5-(3-methyl-2-butenyl)-1H-indole and 5-(3-methylbuta-1,3-dienyl)-1H-indole were obtained from Isolona cauliflora (Annonaceae); structural determination by spectroscopic analysis. Some of the prenylindoles had antifungal and antimalarial activities.     

Kolloidchemie und Phasenlehre

Ohne Zusammenfassung(Zweite Mitteilung.)     

One-Parametric Linear-Quadratic Optimization Problems

We consider families of optimization problems with quadratic object function and affine linear constraints, which depend smoothly on one real parameter. For a generic subclass of such problems only three different types of (generalized) critical points occur, whereas in the general case (of nonlinear one-parameter families of constrained optimization problems on R ⁿ ) five types are to be distinguished. We clarify the theoretical background of these phenomena and illustrate the underlying mechanism with simple examples.     

On Some Generalizations of the Travelling-Salesman Problem

We discuss generalized travelling-salesman problems where nodes are visited either once or not, and a penalty cost is incurred for each unvisited node. The generalization includes the longest-path problem and the shortest-path problem with specified nodes to be visited. A new transformation of generalized into standard travelling-salesman problem is presented. We give computational results for the shortest-path problem with specified nodes. The transformation makes it possible to solve symmetric problems with a relatively large number of specified nodes, which cannot be solved by previously published algorithms based on a linear assignment relaxation. Furthermore, we show how to obtain improved lower bounds for a special Euclidean-type variant.