Zur Spektralanalyse kleiner Substanzmengen

Zusammenfassung Die qualitative und quantitative spektrochemische Analyse kleiner Substanz-mengen, z. B. von Mineralkörnern in der Größenordnung von l bis 30g, ist durch die Kathoden-schichtmethode nachMannkopff undPeters möglich. Die qualitative Analyse erfordert eine Abbildung des Bogens, die die speziellen Leuchteigenschaften der verschiedenen Elemente in der Kathodenschicht beachtet. Die quantitative Analyse verlangt verschiedene Eichkurven, um die verschiedene Selbstabsorption der zur Gehaltsbestimmung verwendeten Linien auszugleichen. Diese Unterschiede werden durch die wechselnde Substanzmenge und eventuell wechselnde Verdampfungsgeschwindigkeit bedingt. Zur Kontrolle dieser Verhältnisse empfiehlt sich die Bestimmung eines Selbstabsorptionswertes, am besten aus dem Vergleich von Multipletts, der über die (mittlere) Dampfdichte Auskunft gibt.

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Summary It is possible to make qualitative and quantitative spectrochemical analyses of small samples, for instance of grains of minerals of the order of 1 to 30g, by the cathode arc layer method ofMannkopff andPeters. The qualitative analysis requires a projection of the arc, which takes account of the special luminous properties of the various elements in the cathode layer. The quantitative analysis requires various calibration curves to compensate the diverse self-absorption of the lines used for determining the content. These differences are conditioned by the variation in the amount of substance and in some cases by the variation in the rate of volatilization. To control these relationships, it is advised to determine a self-absorption value, and this is best accomplished by means of a comparison of the multiplets, which yield information regarding the (mean) vapor density.

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Résumé L'analyse spectrochimique qualitative et quantitative de faibles quantités de substances, telles que des grains de minerais de 1 à 30,g peut être effectuée suivant la méthode de la couche cathodique deMannkopf etPeters. L'analyse qualitative exige une image de l'arc qui tienne compte des propriétés émissives des différents éléments dans la couche cathodique. L'analyse quantitative est basée sur différentes courbes d'étalonnage pour compenser l'auto-absorption des raies utilisées pour le dosage. Les différences d'autoabsorption résultent des quantités variables de matière et éventuellement de la vaporisation plus ou moins facile. Pour le contrôle de ces rapports la mesure d'un coefficient d'auto-absorption s'impose, de préférence par comparaison de multiplets qui donne des renseignements sur la densité de vapeur.

     

Modeling of material failure by the discrete element method

In this paper a two-dimensional discrete element method with rigid, polygonal particles is used to model material failure of granular as well as quasi-brittle materials. Different models for soft contact as well as cohesion between the particles are presented. The capabilities of the method are demonstrated simulating simplistic granular model materials as well as complex concrete specimens with an artificial microstructure. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Eine cyclische Methylendiphosphinsäure: 1,3‐Dihydroxy‐1,3‐dioxo‐1,2,3,4‐tetrahydro‐1λ5,3λ5‐[1,3]diphosphinin

A Cyclic Methylenediphosphinic Acid: 1,3‐Dihydroxy‐1,3‐dioxo‐1,2,3,4‐tetrahydro‐1λ⁵,3λ⁵‐[1,3]diphosphinine Strong acids protonate 1,3‐bis(dimethylamino)‐1λ⁵,3λ⁵‐[1,3]diphosphinine ( 5 ) to give the corresponding cation. The protonation is followed by hydrolytic cleavage of the dimethylamino groups resulting in the formation of the cyclic methylenediphosphinic acid ( 6 ).     

1,1,3,3,5,5-Hexakis(dimethylamino)-λ5-[1,3,5]triphosphinin – Darstellung,Kristallstruktur und NMR-Daten

1,1,3,3,5,5-Hexakis(dimethylamino)-λ⁵-[1,3,5]triphosphinine – Synthesis, Crystal Structure, and NMR Data Preparation of 1,1,3,3,5,5-hexakis(dimethylamino)-λ⁵-[1,3,5]triphosphinine ( 4 ) and the path of its formation from methyl-bis(dimethylamino)difluorophosphorane ( 1 ) and n-butyllithium are described. The chemical behaviour of compounds of type [R₂P=CH–]_n is compared with that of the isoelectronic dichlorophosphazenes [Cl₂P=N–]_n. The structure of 4 is eludicated by n.m.r. spectra and X-ray structural analysis.     

Utilizing Experiment and Theory to Evaluate Rhodamine B ethylenediamine as a Fluorescent Sensor for G-type Nerve Agents

Nerve gas mimic binding with Rhodamine B ethylenediamine (1) was studied in organic media. Binding of the nerve gas mimic, diethyl chlorophosphate (DCP), with the probe generated a non-fluorescent intermediate and a fluorescent product. Fluorescent and non-fluorescent products generated were identified using mass spectrometry and X-ray crystallography. Time-dependent density functional theory calculations were also used to investigate the electronic structure of the fluorescent probe in the ground and lowest lying π?→?π* singlet excited state. Though good agreement between theory and experiment can be obtained for the intense peak in the experimental spectrum using non-hybrid functionals, care must be taken when modelling these complexes due to the appearance of an n?→?π* transition that is too low in energy and appears to fall in the shoulders of the π?→?π* transitions.