Kupplungsreaktionen von Diazoniumbetainen mit 1,6-Methano[10]-annulenderivaten und ihre Cyclisierungsreaktionen zu Heterocyclen

Summary Coupling reactions of the diazoniumbetaines2, 4, 6a, 6b, 6c with derivatives of 1,6-methano[10]annulene1a–c and/or -naphthol7 yield the dyes3a–c, 5a, 5c, 8a–c, 9, 11. The syntheses of different triazine derivatives12a–c, 13a–c, 15, 16, and17a, 17c are described.

Herrn Kollegen Gerhard Schwenker mit den besten Wünschen zum 65. Geburtstag gewidmet     

Die Carotinoide der Blüten von Rosa foetida

Carotenoids in petals of Rosa foetida The petals of Rosa foetida, HERRM ., a species of prime importance in the history of breeding true yellow garden roses, have been analysed for carotenoids for the first time. The following components were identified: β-carotene ( 1 , 4,5%), lutein ( 2 , 8%), zeaxanthin ( 3 , 17,4%), auroxanthin ( 4 , 30,8%), luteoxanthin ( 5 , 21,9%), violaxanthin ( 6 , 9,2%) and neochrome ( 7 , 4,1%). Not identified carotenoids (4,1%) contained probably mutatoxanthin, antheraxanthin and apocarotenals. Thus the brillant yellow colour of R. foetida flowers is due mainly to carotenoid epoxides.     

Uniform semiclassical self-consistent-field calculations of vibrational resonance energies and widths

Using the Breit—Wigner definition of a resonance, we calculate both resonance positions and widths for a model non-separable hamiltonian, using a uniform semiclassical self-consistent-field (SCF) method. Excellent agreement with recent complex-coordinate quantum SCF calculations is obtained.     

The membrane free sonoelectroanalytical determination of trace levels of lead and cadmium in human saliva

In this paper, square wave anodic stripping voltammetry (SWASV), synergistically coupled with an ultrasonically enhanced preconcentration step has been shown to yield a quantitative determination of lead and cadmium in human saliva at a membrane free in situ plated mercury thin film glassy carbon electrode. The sensitivity was facilitated by acoustic streaming which promoted efficient mass transport to the electrode thus reducing sampling times. Cavitation was responsible for cleaning and activating the electrode surface, this was essential in order to obtain a reproducible and representative signal. In silent conditions electrode fouling leading to fluctuations in the baseline current and signal depression, precluded accurate quantitative analyses. The results presented herein provide an extension to the proof of concept given in the authors' earlier work, with the analysis of lead in human saliva as opposed to artificial saliva reported. We also address the hitherto unreported detection and determination of cadmium in this medium. Results for both were independently verified by inductively coupled plasma-mass spectroscopy (ICP-MS). Close agreement between lead concentration determined by sono-SWASV and independent and blind ICP-MS is reported for human saliva samples having a total lead content of 0.92 microg L(-1) and 5 microg L(-1) with a detection limit of 0.5 microg L(-1). Microaddition calibration data for cadmium additions of 0.0125 microg L(-1) to samples spiked with 2.5 microg L(-1) and 5.0 microg L(-1) (reflecting levels in workers occupationally exposed) exhibited close agreement with the known total cadmium in the samples. A detection limit of 1 microg L(-1) cadmium in saliva has been established.     

Characterization of noncovalent complexes formed between minor groove binding molecules and duplex DNA by electrospray ionization-mass spectrometry

The noncovalent complex formed in solution between minor groove binding molecules and an oligonucleotide duplex was investigated by electrospray ionization-mass spectrometry (ESI-MS). The oligonucleotide duplex formed between two sequence-specific 14-base pair oligonucleotides was observed intact by ESI-MS and in relatively high abundance compared to the individual single-stranded components. Only sequence-specific A:B duplexes were observed, with no evidence of random nonspecific aggregation (i.e., A:A or B:B) occurring under the conditions utilized. Due to the different molecular weights of the two 14-base pair oligonucleotides, unambiguous determination of each oligonucleotide and the sequence-specific duplex was confirmed through their detection at unique mass-to-charge ratios. The noncovalent complexes formed between the self-complementary 5′-dCGCAAATTTGCG-3′ oligonucleotide and three minor groove binding molecules (distamycin A, pentamidine, and Hoechst 33258) were also observed. Variation of several electrospray ionization interface parameters as well as collision-induced dissociation methods were utilized to characterize the nature and stability of the noncovalent complexes. The noncovalent complexes upon collisional activation dissociated into single-stranded oligonucleotides and single-stranded oligonucleotides associated with a minor groove binding molecule. ESI-MS shows potential for the study of small molecule-oligonucleotide duplex interactions and determination of small molecule binding stoichiometry.     

LiM2(NCN)Br3 (M = Sr,Eu): Synthesis and Crystal Structures of Solid‐State Carbodiimides with Empty Tetrahedral Metal Entities

Two solid‐state carbodiimide compounds, LiM₂(NCN)Br₃ (M = Sr, Eu), with characteristic empty tetrahedral M₄ entities have been synthesized using a flux route, and their structures were determined by single‐crystal X‐ray diffraction. The new phases LiSr₂(NCN)Br₃ and LiEu₂(NCN)Br₃ are isotypical with the corresponding iodides and crystallize in the cubic system (( , Z = 16) but with smaller unit cells (a = 14.641(1) Å for LiSr₂(NCN)Br₃ and 14.572(1) Å for LiEu₂(NCN)Br₃). The extended structures comprise two interpenetrating three‐dimensional networks: the first one is built from isolated M₄ tetrahedra capped by NCN^2? anions on their triangular faces while the second is made from vertex‐sharing LiBr₆ octahedra. The linear NCN^2? anions exhibit the symmetrical carbodiimide shape and serve as linkers between the tetrahedral entities.     

Investments in stochastic maximum flow networks

Each are (i, j) of the network has capacity _ij where _ij is a non-negative random variable. The capacity of any arc may be reduced increased by an amountu _ij 0 at a cost ofc _ij u _ij . The objective is to maximizev–Kc _ij u _ij wherev is the expected maximum flow. This problem is formulated as a two-stage linear program under uncertainty. Each feasible generates a constraint where is the probability arc (i, j) is in the minimum cut set and the expected value of the maximum flow under . The formulation is later generalized to include certain conditions under which the increase in capacity of an arc may be a non-deterministic function of the investmentc _ij u _ij .     

The effect of a coriolis force on Taylor-Couette flow

Taylor-Couette flow subject to a Coriolis force is studied experimentally and numerically. In the experiment, the Couette apparatus is mounted on a turntable with the axis of the cylinders orthogonal to the rotation vector of the turntable. The Coriolis force stabilizes the fluid against the onset of Taylor vortices and alters the velocity fields, both above and below the transition from the initial flow. At small dimensionless turntable frequencies, the transition yields time-independent Taylor vortices which are tilted with respect to the cylinder axis. At larger there is a direct transition to turbulence. We determine the first-order correction to the classical Couette initial flow, to account for the effects of the Coriolis force, by expanding in powers of. We present numerical results for the axial velocity (the only nonvanishing correction term to order) in the infinite-cylinder approximation.