Serendipitous synthesis of a ditwistane: a one-step access!

4-tert-Butyl-2-cyclohexen-1-one dimerizes in THF solution via its kinetic enolate, leading to di-tert-butylditwistane 8 in up to 36% yield (−78 °C → room temp., protonolysis, flash chromatography). X-ray crystallography shows that 8 incorporates one R and one S enantiomer of the starting ketone; none of the diastereomeric ditwistanes epi-8, epi’-8 or iso-8 was isolated. This means that the formation of 8 proceeds with mutual kinetic resolution and 100% induced diastereoselectivity.     

Über die dilatometrisch indizierten Titrationen

With the help of a dilatometer which permits the continuous determination of volume changes occuring in chemical reactions in aqueous solutions, the volume change during the precipitation of BaSO₄ was followed and applied to the determination of the endpoint of the precipitation. In the case of precipitations of 1 mM BaSO₄ the end-point determination can be reproduced with a standard deviation of less than 0.2%. A strict linearity between the amount of Na₂SO₄ applied and the position of the end-point does not exist. However, a correction factor could be established, so that the absolute determination of sulphate is possible (standard deviation 0.2%). The time required to carry out a single measurement is about 1.5 min. The acid concentration does not influence the composition. On the other hand, the composition was shown to be considerably dependent on Na⁺ and NH₄ ⁺ ions. The presence of the cation N(CH₃)₄ ⁺ does not alter the composition of the precipitate. It is obviously too big to substitute the Ba²⁺ ion.     

Zur Natur der Aluminiumsilicatniederschläge aus Na2H2SiO4-und AlCl3-Lösungen bei neutraler Reaktion

On addition, at neutral reaction, of increasing amounts of AlCl₃ solutions to 0.005 m Na-silicate solutions, in which the silicate anions are monomeric, amorphous, almost Na⁺-free precipitates are formed being at first characterised by a higher atomic Al:Si ratio than the total Al:Si mixing ratio. With increasing Al:Si addition, the Al:Si ratio of the precipitates increases until — at a 3:1 ratio in both the liquid and the solid phase — a definite, “saturated” compound, {[(OH)₂AlO]₃SiOH · aq}, is formed. In this compound the silicate anions are monomeric and not condensable at room temperature. This is valid, too, for precipitates from Al:Si > 3 which contain, besides the “saturated” compound, free Al hydroxide. The first-mentioned precipitates with Al:Si < 3, however, contain polymeric Si units which easily condense to more high-polymeric silicate anions.     

Correction to: Fatou closedness under model uncertainty

Positivity - There is an error in Proposition&nbsp;3.10. In fact, the stated proof only shows     

The Bounded Axiom A Forcing Axiom

We introduce the Bounded Axiom A Forcing Axiom (BAAFA). It turns out that it is equiconsistent with the existence of a regular ∑₂‐correct cardinal and hence also equiconsistent with BPFA. Furthermore we show that, if consistent, it does not imply the Bounded Proper Forcing Axiom (BPFA) (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Klinische Bedeutung und Technik der Blutbleibestimmung mit Zeeman-AAS

Zusammenfassung Nach einem kurzen Überblick über die klinischen Aspekte von Bleivergiftungen wird eine einfache direkte Methode zur Blutbleibestimmung beschrieben. Sie beruht auf Zeeman-AAS mit Feststoff-Graphitrohr-Küvette und Matrixisoformierung mit 1%iger Phosphorsäure und ist gut geeignet für die klinische Routineanalyse.

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Clinical significance and technique of blood-lead determination with Zeeman AAS

Summary After a short review concerning the clinical aspects of lead intoxication, a simple direct determination is described for lead in blood and urine. It is based on Zeeman AAS with solid graphite tube cuvette and matrix isoformation with 1% phosphoric acid, and is useful in clinical routine analysis.

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Vorgetragen anläßlich des Kolloquiums Stand und Perspektive der Feststoffanalyse mit AAS, Wetzlar, 8.–10. 10. 1984     

Fermionic atoms in a three dimensional optical lattice: observing Fermi surfaces, dynamics, and interactions

We have studied interacting and noninteracting quantum degenerate Fermi gases in a three-dimensional optical lattice. We directly image the Fermi surface of the atoms in the lattice by turning off the optical lattice adiabatically. Because of the confining potential, gradual filling of the lattice transforms the system from a normal state into a band insulator. The dynamics of the transition from a band insulator to a normal state is studied, and the time scale is measured to be an order of magnitude larger than the tunneling time in the lattice. Using a Feshbach resonance, we increase the interaction between atoms in two different spin states and dynamically induce a coupling between the lowest energy bands. We observe a shift of this coupling with respect to the Feshbach resonance in free space which is anticipated for strongly confined atoms.