Quantitative r?ntgenspektralanalytische Bestimmung von Kalium, Rubidium, Strontium, Barium, Titan, Zirkonium und Phosphor

Zusammenfassung Am Malsburg-Granit, einem geologisch selbständigen Granitpluton im Südwest-Schwarzwald, wurde die lokale Heterogenität der Elemente Kalium, Rubidium, Titan, Zirkonium, Phosphor, Strontium und Barium mit Hilfe der Röntgenspektralanalyse bestimmt, um anschließend die Heterogenität des gesamten Gesteinskörpers zu erfassen.Die Analysenergebnisse sind reproduzierbar, wenn das Gesteinsmaterial nach systematischer Probenahme auf eine Korngröße <37 aufgemahlen wird. Es wurden die Fehler bestimmt, die durch Zählstatistik, das Meßverfahren und die Aufbereitung entstehen. Dabei ergab sich, daß die gefundenen Fehler für 95% Sicherheit stets kleiner sind als die Streuung der Elemente in einem Steinbruch bzw. im gesamten Granitkörper.

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Summary The local heterogeneity of K, Rb, Ti, Zr, P, Sr and Ba was determined by X-Ray Fluorescence Analysis as a first step in our investigations concerning the determination of the regional heterogeneity of a whole granite body of larger extent. The first granite of this series is the Malsburg-Granite in the South-West of the Black Forest.The analytical results are reproducible and accurate, if the rock samples are ground below 450 mesh. The errors and mean deviations caused by counting, instrumentation and preparation are small in comparison with those in a rock sample of an outcrop or the whole rock body.The method of X-Ray Fluorescence Analysis can be applied for the study of the mechanism of magmatic intrusion and differentiation.

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Auszug aus Dipl.-Arbeit H. Ackermann, 1962, Frankfurt/M, unveröffentlicht.

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Wir danken der Deutschen Forschungsgemeinschaft für apparative und finanzielle Hilfe.     

A relative organolithium stability scale derived from tin-lithium exchange equilibria. Substituent effects on the stability of alpha-oxy- and alpha-aminoorganolithium compounds

Quantitative thermodynamic stability scales of organolithium compounds can be derived from measurements of tin-lithium exchange equilibria. A DeltaG(eq) scale of alpha-oxy- and alpha-aminoorganolithium compounds was established, and quantitative stabilization effects of O-alkyl, O-alkoxyalkyl, O-carbamoyl, N-carbamoyl, and O-carbonyl groups of the alpha-carbanion are presented. It has been found that an alpha-oxycarbanion is far better stabilized by a carbonyl group as the O-substituent than by an alkyl or alkoxyalkyl group, while the anion-stabilizing effects of the different O-carbonyl substituents are comparable. An N-carbamoyl group was found to have a somewhat higher stabilizing effect than its O-carbamoyl counterpart. NMR data are presented that show that benzylic N- or O-substituted carbanions have highly planarized structures where the negative charge is highly delocalized. The stability data obtained from the tin-lithium exchanges can be easily converted into "effective pK" data that are useful for predicting the acid-base behavior of this type of organolithium species.     

Synthesis of type II beta-turn surrogate dipeptides based on syn-alpha-amino-alpha,beta-dialkyl-beta-lactams

The achiral bis(trimethylsilyl)methyl group acts as an efficient stereochemical determinant of the alpha-alkylation reaction in beta-branched alpha-phenyloxazolidinyl- or alpha-diphenyloxazolidinyl-beta-lactams and provides the first stereocontrolled access to syn-alpha-amino-alpha,beta-dialkyl(aryl)-beta-lactams. These products are readily transformed into type II beta-turn mimetic surrogates 2B. [reaction: see text]     

Castanospermine-trehazolin hybrids: a new family of glycomimetics with tuneable glycosidase inhibitory properties

Bicyclic azasugar glycomimetics related to castanospermine and trehazolin have been prepared from sugar carbodiimides via aminooxazoline intermediates; preliminary enzyme inhibition tests showed a marked dependence of the selectivity and potency towards alpha and beta-glucosidases upon the nature of the exocyclic substituent.     

Determination of methanol and ethanol by gas chromatrography following air sampling onto florisil cartridges and their concentrations at urban sites in the three largest cities in Brazil

A new sampling protocol was developed to determine methanol and ethanol in the gas phase, at low concentration levels, in urban atmospheres. The procedure involves collection of air samples (20.0-30.0 l) with three florisil cartridges connected in series, at a flow rate ranging from 1.0 to 2.0 l min(-1) and subsequent elution of the alcohols with water. Separation and quantification were done by gas chromatography (GC) coupled with a flame ionization detector, 'SPI' injector and column DB WAX (30 mx0.53 mmx1 mum). The minimum mass detected by the method, based on two times the average background mass on the blank cartridges, was 0.3 mug for both alcohols which, for a sampled volume of 30 l, resulted in detection limits of 7.6 and 5.3 ppbV for methanol and ethanol, respectively. The determined alcohol concentrations, in 42 different samples from the three largest cities in Brazil-S?o Paulo, Rio de Janeiro and Salvador-ranged from 72 ppbV to below the detection limit for methanol and from 355 to 12 ppbV for ethanol.     

Variability in phenolic composition of Hypericum androsaemum

The methanolic extracts of fifteen Hypericum androsaemum samples, growing spontaneously or cultivated in Portugal, were analysed by HPLC/DAD, allowing the identification of 9 phenolic compounds and the detection of 6 phloroglucinols. Total amounts of phenolics found ranged from 11 to 39 g/kg, and the influence of some factors which may be responsible for this variation is discussed. The individual compounds were also quantified. Four different phenolic profiles were found concerning both qualitative and quantitative composition, indicating the possible existence of chemical polymorphism.     

Synthesis and evaluation of isourea-type glycomimetics related to the indolizidine and trehazolin glycosidase inhibitor families

A practical synthesis of reducing isourea-derived azasugar glycomimetics related to the indolizidine and trehazolin glycosidase inhibitor families with different pK(a) values is disclosed. The polyhydroxylated bicyclic system was built from readily accessible hexofuranose derivatives through a synthetic scheme that involves the preparation of a 5-deoxy-5-carbodiimido adduct by triphenylphosphine-mediated tandem Staudinger--aza-Wittig-type coupling of azide and isothiocyanate precursors, intramolecular cyclization of a transient vic-hydroxycarbodiimide derivative, and nucleophilic addition of the endocyclic nitrogen atom of the generated 2-amino-2-oxazoline intermediate, with a pseudo-C-nucleoside structure, to the masked aldehyde group of the monosaccharide. The last step is pH-dependent so that the final compounds can pivot between the furanose and the 2-oxaindolizidine forms. Nevertheless, the indolizidine tautomer having the R configuration at the aminoacetalic center, fitting the anomeric effect, was the only species detected in solution at neutral or slightly acidic pH when starting from solutions at basic pH. Glycosidase inhibition tests (K(i) values down to 1.9 microM) showed a marked dependence of the selectivity and potency toward alpha- and beta-glucosidases upon the nature of the substituent at the exocyclic isourea nitrogen, shifting from alpha- to beta-selectivity when going from hydrophilic to hydrophobic substituents. Enzyme inhibition is also pH dependent, supporting a dominant role for the uncharged form of the polyhydroxyiminoindolizidine system in the inhibition of beta-glucosidases.     

Mechanical and softness characterization of “deco” and “micro” embossed tissue papers using finite element model (FEM) validation

Cellulose - An innovative approach of using a laboratory embossing prototype was carried out to develop and optimize tissue papers, to quantify the influence of “deco” and...     

Hörmander Representations and Hill Trajectories for Certain Partial Differential Operators

We consider some partial differential operators associated with Markov projections and describe their Hörmander representations. The corresponding Hill diffusion and drift trajectories are also studied.     

A colourful bond between art and chemistry

How can a work of art give us clues about scientific aspects? How can chemistry help a painter enhance his creativity and, above all, preserve the original characteristics of his work? Does an artist require scientific knowledge to innovate or, at least, not to be faked? Other symbiotic fields between art and science are: tattoos, as body art with physical and chemical consequences; pigments, as basic materials with interesting historiographical preparations; spectroscopy diagnosis, as very broad and thorough method of analysis (but also specific and non-intrusive); biosensors, as one of the applications of new pigments. Note also the interconnection between the several possible paths of science and art, which reflect new challenges with enormous potential investigated through a literature review and the application as a case study in an educational inquiry module.