Comprehensive on-line HPLC-GC for screening potential migrants from polypropylene into food: The effect of pulsed light decontamination as an example

High performance liquid chromatography (HPLC) was used for the fractionation of extracts from polypropylene (PP) films and coupled on-line to gas chromatography (GC) with automated transfer of the complete HPLC fractions (comprehensive on-line HPLC-GC, i.e. HPLCxGC). Flame ionization detection (FID) was used for the estimation of concentrations, mass spectrometry (MS) for identification work. This method was applied to investigate whether pulsed light (PL) treatment for the microbiological decontamination of polypropylene packaging materials produces reaction products requiring an evaluation to meet regulatory requirements. To demonstrate the safety of PL treatments with regard to the formation of reaction products, i.e. that no component is formed that could endanger human health, basically comprehensive analysis of components potentially migrating into food is required, but comprehensiveness cannot be proven and remains an approximation. The threshold concentration in the film was estimated either from the conventional European non-detection limit of 0.01 mg/kg food or the concept of the threshold of toxicological concern (TTC) for an unknown substance, i.e. an exposure to 0.15 μg per person and day. PL treatment of the films containing Irgafos 168 produced several new components exceeding these limits, i.e. a toxicological safety assessment would probably be required. No such peaks were detected for Tinuvin 326, Irganox 1076 and Chimassorb 81. No degradation of the polymer was detected.     

Janus carbosilane/phosphorhydrazone dendrimers synthesized by the ‘click’ Staudinger reaction

The first association of carbosilane dendrons (having a phosphine at the focal point) with phosphorhydrazone dendrons (having a thiophosphoryl azide at the focal point) has been successfully carried out by ‘Staudinger click’ reaction. The corresponding Janus dendrimers possess the characteristics of both components; they are oily as the carbosilane dendrons, and they can be easily functionalized as the phosphorhydrazone dendrons.     

Impedance-effects in capacity estimation

Formulas for the capacity of an unsignalized intersection for traffic streams which are subordinated to two or more streams of higher priority are developed. The case of only two conflicting streams analysed by Tanner (1962) is extended. The process at the intersection is modelled as a priority queuing system with Poisson input and service times depending on the work load.     

Imidazo[1,5-g][1,4]diazepines, TIBO analogues lacking the phenyl ring: synthesis and evaluation as anti-HIV agents.

The imidazo[1,5-g][1,4]diazepine derivatives 7a and 7b, analogues of TIBO lacking the aromatic ring, were prepared as part of a research program to find compounds displaying antiviral activity against HIV-2 and resistant strains of HIV-1. Condensation of N-trityl and N-tosyl 4-(2-chloroethyl)-imidazole with the appropriate amino alcohols gave compounds 10a-c and 16a-e. The hydroxyl group in these intermediates was activated toward closure of the [1,4]diazepine ring by either conversion to the corresponding chloro derivative, or by N → O transfer of the tosyl group. However, only cyclization to compounds 13a and 13b proved efficient. These products were converted to the target molecules 7 by reaction of their C-2 anion with S₈. In vitro evaluation of compounds 7a,b and 13,a,b in cell culture (CEM SS/HIV-1-LAI and CEM SS/HIV 1 nevirapine resistant cells) revealed that only 13b displayed minimal activity.     

λ-Shaped mesogens. Structure, phase formation and properties

This contribution is concerned with molecules composed of rigid linear segments which are connected in such a way that a λ-shape results. Such types of shape have been predicted to lead to an enhanced solubility in low molar mass solvents and in the melt state of flexible chain molecules. The theoretical treatment predicted additionally that such molecules should be able to form lyotropic and thermotropic liquid crystalline phases. Experimental data on the thermodynamic properties, the structure formation in the solid and fluid condensed state, the solubility in low molar mass solvents and selected optical and electro-optical properties are reported; these are in good agreement with the predictions.     

Production planning with time-dependent capacity bounds

In this paper, we examine the problem of finding minimum-cost production schedules that satisfy known demands over a finite planning horizon. A dynamic programming algorithm is developed to find these schedules for cases in which production in each period is constrained by a time-dependent capacity bound. The costs considered are production and inventory holding costs, and all cost functions are assumed to be nondecreasing and concave. The algorithm is an extension of Florian and Klein's method developed for problems in which capacity bounds are the same in all periods. Although the problem with time-dependent bounds is NP-complete, the algorithm is shown to be efficient when the capacity bounds are integer multiples of a common divisor and the largest multiplier is small. Hence, it is useful in applications in which production capacity is periodically increased by adding facilities of the same size.     

Ein Dimensionsbegriff in Wahrscheinlichkeitsräumen

Ohne Zusammenfassung     

Properties of nuclear matter in the Λ00-approximation for local potentials

In the Λ⁰⁰-approximation of the Green's function theory the nuclear matter properties have been calculated for several local potentials. All these potentials contain a hard core repulsion and match the experimentalS-wave phase-shifts. Due to the analytical form of these potentials one can obtain many results analytically. Thus the whole structure of this approximation becomes relatively transparent and can easily be calculated. Therefore this model can be used as an input for more complicated approximations. Furthermore one can also treat the optical potential problem. Te results for nuclear matter are comparable with the results for nonlocal potentials. The momentum distribution deviates more strongly from the independent particle model as in the case of nonlocal potentials.