Lokale Kennzeichnungen der Minimalhyperregelflächen

Generalized ruled hypersurfaces are generated by a one-parameter family of (n–2)-dimensional linear subspaces of the n-dimensional Euclidean space E_n. In this paper we give local characterizations of generalized ruled hypersurfaces with an everywhere vanishing mean curvature.     

Iodine-129 and natural iodine-127 in deer thyroids from the environment of a small nuclear fuel reprocessing plant and from sites remote from nuclear facilities

Concentrations of the fission product¹²⁹I and natural¹²⁷I were determined in deer thyroids collected in the environment of the small Karlsruhe nuclear fuel reprocessing plant (WAK) and in a region remote from¹²⁹I sources of nuclear facilities. The isotopic ratio¹²⁹I/¹²⁷I in thyroids from the environment of WAK varies from 1.0×10^–6 to 12.9×10^–6, which is about one order of magnitude higher than the¹²⁹I/¹²⁷I ratios in thyroids from deer in a region remote from nuclear facilities. These ratios were between 0.2×10^–6 and 0.7×10^–6.     

Dry deposition velocity of iodine-129 onto grass as obtained by field measurements in the environment of a nuclear fuel reprocessing plant

The deposition velocity of gaseous organic¹²⁹I species from the exhaust air stack of the Karlsruhe reprocessing plant onto pasture grass was measured by a field experiment. By simultaneously measuring the amount of¹²⁹I deposited per unit area of pasture grass and the time integrated mean air concentration of¹²⁹I a deposition velocity of V_g=5.8×10^–1 /cm s^–1/ onto pasture grass was determined.     

Stereocontrolled synthesis of angularly fused tricyclic ring systems by means of 1-metalla-1,3,5-hexatrienes (M=Cr, W)

An efficient pathway for the stereocontrolled synthesis of functionalized, angularly fused tricyclic ring systems from readily available (1-alkynyl)carbene complexes [(OC)(5)M=C(OEt)C(triple bond)CR] (M=Cr, W; R=Ph, c-C(6)H(9)) is described. The synthesis involves the formation of a 1-metalla-1,3,5-hexatriene from the (1-alkynyl)carbene tungsten complex [(OC)(5)W=C(OEt)C(triple bond)C-c-C(6)H(9)] and a secondary amine, and its thermally induced pi-cyclization to a tetrahydroindene, which undergoes a spontaneous isomerization to another tetrahydroindene. Condensation of these tetrahydroindenes with pyran-2-ylidene complexes derived from (1-alkynyl)carbene complexes [(OC)(5)M=C(OEt)C(triple bond)CPh] (M=Cr, W) proceeds smoothly giving angularly fused tricyclic ring systems, rearrangement of which may generate spiro(cyclopentane-1,1-indanes) as side products. The synthesis is highly versatile and can be applied to the formation of various ring systems, such as steroid-type ring skeletons.