Matrix Solid-Phase Dispersion Micro-Extraction of Pesticides from Single Insects with Subsequent GC–MS Analysis

A simple multiresidue method based on matrix solid-phase dispersion (MSPD) micro-extraction was studied to determine various organophosphorus (OPPs) and pyrethroid pesticides in single insects. Optimisation of the relevant parameters showed that, in the case of OPPs and permethrin, extraction from 40 mg of isopod (Porcellio scaber) and the use of C₈-bonded silica and 100 L of ethyl acetate were the best conditions, while silica and 3.5 mL of n-hexane were optimal for the less polar pyrethroids. Subsequently, 1 L (ethyl acetate) or 20 L (n-hexane) of the extracts were analysed by GC–MS without any further clean-up. The limits of detection (LODs), in the SIM mode, were 5–80 ng g^–1 for most OPPs and trans-permethrin (cis-permethrin 0.3 ng g^–1) when using the C₈-bonded silica/ethyl acetate procedure, and 5–35 ng g^–1 for the pyrethroids when using the silica/n-hexane procedure. The recoveries of the OPPs and pyrethroids from the isopods were 52–94%. The practicality of the proposed method was studied for pesticides in isopods which had been fed polluted leaves.     

Historic papers in physics — The case of Hugo Martin Tetrode, 1895–1931

Conclusions It appears from the foregoing discussion that the results of citation analysis can be interpreted, in the investigated case, as indicators for either the direct use which is made of a paper in research, or for the visibility of its author as a pioneer in a (sub)-discipline. In the last case the citation scores primarily reflect the dynamics of the relevant scientific discipline.More generally the case-study indicates the potential usefulness of combining citation analysis with more conventional ways of evaluating the role articles play and have played in science.The authors wish to thank Prof. H. B. G. Casimir who first brought the work of H. M. Tetrode the their attention.     

Application of PDF Modeling to Swirling and Nonswirling Turbulent Jets

The turbulence modeling in probability density function (PDF) methods is studied through applications to turbulent swirling and nonswirling co-axial jets and to the temporal shear layer. The PDF models are formulated at the level of either the joint PDF of velocity and turbulent frequency or the joint PDF of velocity, wave vector, and turbulent frequency. The methodology of wave vector models (WVMs) is based on an exact representation of rapidly distorted homogeneous turbulence, and several models are constructed in a previous paper [1]. A revision to a previously presented conditional-mean turbulent frequency model [2] is constructed to improve the numerical implementation of the model for inhomogeneous turbulent flows. A pressure transport model is also implemented in conjunction with several velocity models. The complete model yields good comparisons with available experimental data for a low swirl case. The individual models are also assessed in terms of their significance to an accurate solution of the co-axial jets, and a comparison is made to a similar assessment for the temporal shear layer. The crucial factor in determining the quality of the co-axial jet simulations is demonstrated to be the proper specification of a parameter ratio in the modeled source of turbulent frequency. The parameter specification is also shown to be significant in the temporal shear layer.     

On the nature of pulsars

The paper contains a relatively non-technical summary of some recent work by the author and Jeremy Butterfield. The goal is to find a way of assigning meaningful truth values to propositions in quantum theory: something that is not possible in the normal, instrumentalist interpretation. The key mathematical tool is presheaf theory where multi-valued, contextual truth values arise naturally. We show how this can be applied to quantum theory, with the ‘contexts’ chosen to be Boolean subalgebras of the set of all projection operators.     

Bestimmung von Wolfram durch potentiometrische Titration mit Chrom(II)

Zusammenfassung Gestützt auf die vollständige Kenntnis der effektiven Redoxpotentiale gelingt die reduktometrische Titration von Wolfram mit Chrom(II) in beliebigen Gemischen. Nur Titan stört. Die Bestimmung erfolgt in 9 M HCl bei 55° C, zur Indizierung dient eine Goldelektrode. Es tritt keine Abweichung von der idealen Stöchiometrie und kein Blindwert auf. Die Streuung um die Regression beträgt s _Ry =0,74 mg W (mit f _R =11) bei 92 bis 276 mg W, auch in Gegenwart von Eisen. Anwendungen auf Ferrowolfram, Stahl, Hartmetallvorlegierung und silikatisches Material werden beschrieben.

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Determination of tungsten by potentiometric titration with chromium(II)

Summary Based on the complete knowledge of the conditional redox potentials the reductometric determination of tungsten with chromium(II) in any mixture is possible. Only titanium interferes. The titration is performed in 9 M HCl at 55° C and indicated by a gold electrode. There is neither a deviation from stoichiometry nor a blank value. The standard deviation is s=0.74 mg W (withf=11) in the range of 92–276 mg W, also in presence of iron. Applications to ferrotungsten, steel, hard metal alloy and siliceous material are described.

Wir danken Herrn Prof. F. Umland für die Förderung unserer Arbeiten sowie Frl. P. Klenner und Frau U. Görs für ihre Mithilfe.     

Supercooling of the disordered vortex lattice in Bi(2)Sr(2)CaCu(2)O(8+delta)

Time-resolved local induction measurements near the vortex lattice order-disorder transition in optimally doped Bi(2)Sr(2)CaCu(2)O(8+delta) crystals show that the high-field, disordered phase can be quenched to fields as low as half the transition field. Over an important range of fields, the electrodynamical behavior of the vortex system is governed by the coexistence of ordered and disordered vortex phases in the sample. We interpret the results as supercooling of the high-field phase and the possible first-order nature of the order-disorder transition at the "second magnetization peak."