Isotope dilution analysis in column-coupling isotachophoresis

The use of isotope dilution technique to eliminate problems associated with demands for a high load capacity in column-coupling capillary isotachophoresis was studied. Determinations of phosphate present in a model mixture and in white wine served for the evaluation of this approach to quantitative analysis in isotachophoresis. A high selectivity of the analysis with acceptable accuracy and precision of the determination also in complex ionic mixtures in a short time are obvious advantages of this approach.     

A Selective Conversion of Benzylic Alcohols to the Corresponding Carbonyl Compounds by Means of an Ag(III) Complex

 Carbonyl compounds of the type XPhCOR (R = H, Me, Ph; X = H, Me, Cl, Br) are prepared in high yields by reaction of the corresponding benzylic alcohols XPhCHOHR with KNa₄ [Ag(HIO₆)₂]×12H₂O in alkaline solution. This method allows the selective oxidation of benzylic alcohols in compounds containing other types of alcoholic functional groups.     

An unusual decomposition of a complete 7-partite graph of order 28

A decomposition of the complete 7-partite graph on 28 vertices where each set in the partition has four vertices is given. Several unusual properties of this decomposition are discussed, giving rise to several natural questions.     

General variable neighborhood search for the continuous optimization

We suggest a new heuristic for solving unconstrained continuous optimization problems. It is based on a generalized version of the variable neighborhood search metaheuristic. Different neighborhoods and distributions, induced from different metrics are ranked and used to get random points in the shaking step. We also propose VNS for solving constrained optimization problems. The constraints are handled using exterior point penalty functions within an algorithm that combines sequential and exact penalty transformations. The extensive computer analysis that includes the comparison with genetic algorithm and some other approaches on standard test functions are given. With our approach we obtain encouraging results.     

Evaluation of a New LC Method for Analysis of Vancomycin Released from an Orthopaedic Drug Carrier System

Because of the increasing spread of antibiotic multiresistance, the drug vancomycin is a commonly used in orthopaedic surgery. The objective of our research was to develop a new method for analysis of the drug carrier systems—i.e. systems providing prolonged drug release—used in orthopaedics. The development of a pharmaceutical formulation requires a simple method for analysis of the active ingredient. For characterization of a drug release profile as a function of time, release of antibiotics from hydrophobic matrices was followed by in vitro tests. A rapid LC method, using a 2.1 mm × 150 mm, 5 μm particle, C₁₈ column and methanol–water–acetate buffer as mobile phase was developed for quantitative analysis of samples taken in drug release studies.

     

Comparison of photoluminescence and capacitance spectroscopies as efficient tools for interface characterisation of heterojunction solar cells

The correlation between diffusion capacitance and photoluminescence as a method of interface-defect density characterisation in amorphous silicon/crystalline silicon heterojunction solar cells is explored by numerical modelling and experimentally. At open circuit, the influence of the defect density at the front amorphous silicon/crystalline silicon interface and the surface recombination velocity of the minority carriers in the bulk depend on the doping level of the crystalline silicon and the critical contribution of the majority carriers. Experimental illustration is given for five series of solar cells with different doping levels, interface properties and back contacts. We observe agreement between simulation and experimental results and a correlation between the two methods of measurement of interface defects.     

The μ-dependence of the effective weak Hamiltonian andK→2π amplitudes in chiral-bag model

This paper studies the μ-dependence of the operator matrix elements. Although the μ-dependence must in principle cancel as illustrated in the paper by using a simple pedagogical model, in practice the choice of μ markedly influences the theoretical predictions forK→2π decays.     

Characterization of surface-active substances during a semi-field experiment on a phytoplankton bloom

The determination of surface-active substances (SAS) during the evolution of a phytoplankton bloom in a model plankton ecosystem was done by electrochemical methods. The separation and characterization of the organic material present were also done on XAD-8 resin columns. It was found that large amounts of the SAS, predominantly of the humic (fulvic) type, were present from the beginning of the experiment and partly masked the effects of organic substances released by phytoplankton. Although the transformation of the organic matter (consumption and/or excretion) was obvious, no general trend in the amount or type of surface-active matter was observed during the experiment.     

Hammer's X-ray problem is well-posed

Summary In un precedente articolo [2]G. Mägerl ed il secondo autore hanno dimostrato la buona posizione del problema ricostruttivo di Hammer, imponendo che il corpo convesso da ricostruire fosse contenuto in un preassegnato insieme limitato. Si dimostra qui che tale limitazione può essere tolta.Ricerca finanziata con fondi MPI.