Umsetzung von Metall- und Metalloidverbindungen mit mehrfunktionellen Molekülen,XIX. Synthese von Amidoborazinen

Reaction of Metal and Metalloid Compounds with Polyfunctional Molecules. XIX. Synthesis of Amidoborazines By reaction of 2-chloro-1,3,4,5,6-pentamethylborazin with silylated carbonic acid amides and thioamides resp. the corresponding amidoborazines are obtained. By reaction of lithiated hexamethyldisilazane with 2-chloro-1,3,4,5,6-pentamethylborazine, the 2-hexamethyldisilazanyl-1,3,4,5,6-pentamethylborazine is formed. ¹H, ¹¹B, and ¹⁹F n.m.r. spectra, mass spectra and characteristic i.r. group frequencies are reported.     

Semiconductor gas sensors in bioreactor control

A simple semiconductor gas sensor (TGS 812) is used for the on-line measurement and control of indole during the production of l-tryptophan from indole and l-serine with immobilized E. coli cells. Indole is estimated in the reactor gas space. In combination with an automatic indole supply system, a feed-batch process became possible. The indole concentration was monitored and kept within the optimal range (300–600 mg l^?1). A simple gas-sensing electrode dipped in the reaction medium provides direct measurement of organic solvents and gases in the liquid. Such a system is suitable for on-line determination of ethanol (10–70 g l^?1) during continuous production of ethanol with immobilized yeast cells.     

Revision of the decay data of166–170Re,including new isomers167m,169mRe

The neutron-deficient rhenium isotopes^166–170Re were investigated using reactions of³²S with monoisotopic¹⁴¹Pr targets. Gamma-rays following the-decays of^166–169Re were measured for the first time. Four new-rays with energies of 4.70,4.83, 4.87, and 5.02 MeV were detected in addition to the known 5.50, 5.26, and 5.06 MeV-rays. Alpha-decaying isomer pairs were discovered in¹⁶⁷Re and¹⁶⁹Re. The measured half-lives are 2.3(2)s for¹⁶⁶Re, 3.4(4)s and 6.2(5)s for¹⁶⁷Re, 4.4(1)s for¹⁶⁸Re, 8.1(5)s and 16.3(8)s for¹⁶⁹Re, and 9.2(2)s for¹⁷⁰Re. The nuclear structure is discussed in terms of single-particle states.This work has been funded by the German Federal Minister for Research and Technology (BMFT) under contract number 06GÖ105     

On enhanced tuning capabilities of external cavity lasers using acousto-optic modulators

For an enhanced tuning of an external-cavity Littrow diode laser at 670 nm a new approach based on the frequency controlling of intra-cavity acousto-optic modulators (AOM) has been developed and tested. Using a method called “mode shaking” a nearly continuously laser tuning over a frequency range of 186 GHz (0.279 nm) within a time interval of 20 ms has been achieved. A further method called “far laser frequency jump” allows frequency changes of up to 1080 GHz (1.6 nm) between two spectral regions of the diode laser emission range within about 50 μs.     

Turbulent flow in a ribbed channel: Flow structures in the vicinity of a rib

PIV measurements are performed in a channel with periodic ribs on one wall. The emphasis of this study is to investigate the flow structures in the vicinity of a rib in terms of mean velocities, Reynolds stresses, probability density functions (PDF), and two-point correlations. The PDF distribution of u′ is bimodal in the separated shear layer downstream of the rib. The maximum Reynolds shear stresses occur at the leading edge of the rib. Based on quadrant analysis, it is found that ejection motions make a dominant contribution to the Reynolds shear stress in this region. Moreover, topology-based visualization is applied to the separation bubble upstream of the rib. Salient critical points and limit cycles are extracted, which gives clues to the physical processes occurring in the flow.     

Quantum aspects of chaos for three-level atoms interacting with two harmonic oscillators

We treat a simple generalization of the Jaynes-Cummings model to three-level atoms interacting with two harmonic oscillators. The model allows for classical chaos even in the rotating wave approximation, as was recently shown by Shepelyanski. Under conditions most favorable for classical chaos we find linear level repulsion à la Wigner.     

Massenspektrometrische Identifizierung von biogenen Aminen in Form ihrer 1-Dimethylamino-naphthalin-5-sulfonyl-Derivate

Zusammenfassung Von etwa 80 1-Dimethylamino-naphthalin-5-sulfonyl-(DANS-)Derivaten biogener Amine und verwandter Verbindungen mit unterschiedlichen strukturellen Elementen wurden die durch Elektronenstoß induzierten Fragmentierungen untersucht. Die Prinzipien dieser Fragmentierungen und die Brauchbarkeit der Massenspektrometrie bei niedrigem Auflösungsvermögen für die Identifizierung dünnschicht-chromatographisch getrennter DANS-Derivate biogener Amine aus Gewebsextrakten werden diskutiert.

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Mass spectrometric identification of biogenic amines as 1-dimethylamino-naphthalene-5-sulphonyl derivatives

The fragmentation by electron impact of approximately 80 1-dimethylamino-naphthalene-5-sulphonyl (DANS) derivatives of biogenic amines and related substances of different structural features has been studied. The principles of these fragmentations and the suitability of low resolution mass spectrometry for the identification of thin-layer chromatographically separated DANS-derivatives of biogenic amines from tissue extracts are discussed.