Synthesis and structural characterization of mixed aluminum-gallium-offretites

A new synthesis procedure is reported for the preparation of mixed Al,Ga-offretites over the entire solid solution range 0 ≤ Ga/(Ga + Al) ≤ 1. The resulting materials are characterized by X-ray powder diffraction, adsorption microcalorimetry and multinuclear solid state NMR. The ²⁹Si MAS-NMR data are consistent with statistical occupancy of the T₁ and T₂ sites by aluminum and gallium, and also show no positive evidence for preferential siting effects between both framework metals. Isotropic chemical shifts and nuclear electric quadrupolar coupling constants for ²⁷Al and ⁷¹Ga have been obtained from a field-dependent analysis of the center of gravity in the MAS-NMR spectra. H-Al, Ga-offretites produced by ammonium exchange and subsequent calcination reveal evidence of partial demetallation of the framework with formation of extra-lattice metal species.     

Determination of digoxin in human-serum

Summary Four immunological assays (RIA, ELISA, EMIT, FPIA) for digoxin were characterized with respect to reproducibility, detection limit, selectivity, and accuracy, followed by the comparison with HPLC. Afterwards the serum samples of nearly 60 patients were analyzed by these five methods.It could be shown, that the reproducibility at 2 g/l was fairly good for all methods. Reliable analysis in the lower concentration range (< 1 g/l) was difficult with two assays, because of insufficient detection limits. There was a marked cross-reactivity to other digitalis glycosides. Moreover, correlation between the immunological methods and in comparison to the HPLC-method was low.

---

Bestimmung von Digoxin in HumanserumVergleich einiger immunologischer Assays mit einer vorgeschlagenen HPLC-Referenzmethode

     

Ground state and response properties of mercury clusters

The change of the cohesive energy and the optical absorption spectra of small singly sized Hg clusters is discussed. The cohesive energy allows one to determine the different regimes of chemical bonding. The optical spectra show an abrupt transition to a collective, plasmon-like absorption as a function of increasing cluster size. The position of the one plasmon peak is: 1) independent of the charge state, 2) nearly independent of cluster size, and 3) agrees with that of the classical Mie plasmon calculated from the experimental dielectric constants. The width of the plasmon peaks is discussed. A strong influence of electronic correlations on the cluster size dependence of the oscillator strength is observed.     

Über die umsetzung von N-fluorsulfonylisocyanat mit verschiedenen phosphorverbindungen

Zusammenfassung N-Fluorsulfonylisocyanat bildet mit Triphenylphosphin, Phosphorigsäuretrisdimethylamid und Phosphorigsäuretriäthylester 11-Addukte unterschiedlicher Stabilität. Die Bildung von N-Fluorsulfonylcarbodiimiden aus N-Fluorsulfonylisocyanat und dem Phospholenoxid 7 gelingt nicht, da die Reaktion auf der Stufe des N-Fluorsulfonylphospholenimins stehenbleibt.

---

Reaction of N-fluorosulfonyl isocyanate with phosphorus compounds

11-adducts of different stability are the products of the interaction of N-fluorosulfonylisocyanate with triphenylphosphine, phosphorous acid tris(dimethylamide), and triethyl phosphite. No N-fluorosulfonylcarbodiimides are formed from N-fluorosulfonylisocyanate and phospholene oxide (7), since the reaction does not proceed beyond the intermediate N-fluorosulfonylphospholene imine.

     

Comparison of a modified Kjeldahl and a vacuum fusion technique for determination of nitrogen in tantalum alloys

Results obtained for the determination of nitrogen in the tantalum alloys T-111 (Ta-8 W-2 Hf) and T-222 (Ta-10 W-2.5 Hf-0,1C) by Kjeldahl and vacuum fusion procedures are compared. Results obtained by each technique are shown for the determination of nitrogen m the MAB T-111 sample, two commercial T-111 samples and a commercial sample of T-222 alloy. In the 5-25 ppm range, the relative standard deviation was 3-9% by the Kjeldahl procedure and 4-8% by vacuum fusion. This is a measure of the homogeneity of the material as well as of the reproducibility of the results. The agreement of the results obtained by these two techniques increases confidence in the vacuum fusion results for nitrogen in tantalum.