The SU6 Clebsch-Gordan coefficients for the reduction of (35) ⊗ (35) to (35), and (56) ⊗ (35) to (56)

A convenient definition of the basis vectors of SU₆ representations is given. The most important Clebsch-Gordan coefficients are calculated.     

Lithium alkyl assisted coupling of a 2-cyano-2,3-dihydro-1H-1,3,2-diazaborole to give tBuNCH=CHN(tBu)BC(iPr)=N-BN(tBu)CH=CHNtBu

Reaction of 2-cyano-1,3,2-diazaborole tBuNCH=CHN(tBu)BCN (2) with half an equivalent of isopropyllithium afforded compound tBuNCH=CHN(tBu)BC(iPr=N-BN(tBu)CH=CHNtBu (7). In contrast to this, a 1:1 stoichiometry of the reactants led to tBuNCH=CHN(tBu)BiPr (6) as the product of a nucleophilic substitution process at the boron atom. Similarly, regardless of the molar ratio of reactants employed, treatment of 2 with cyclopropyllithium, isobutyllithium or phenyllithium afforded solely substitution products tBuNCH=CHN(tBu)BR [R =cPr (12); Ph (13); iBu (14)].     

Fluorescence lifetime and quantum efficiency for 5d → 4f transitions in Eu2+ doped chloride and fluoride crystals

An investigation of the relevant parameters for broadly tunable lasers utilizing the efficient, broad-band 5d → 4f emission in a number of Eu²⁺ doped metal fluorides, chlorides, and fluoro-chlorides has been performed. Results of measurements of absorption and emission spectra, quantum efficiencies, and fluorescence lifetimes in MF₂ and MCl₂ (M = Ca, Ba, Sr) and MFCl (M = Ba, Sr) are presented. A calculation of the pump energy threshold for laser action in CaF₂ : Eu²⁺ based on our spectroscopic data is made. Although the estimation indicated that laser threshold in CaF₂ : Eu can be easily achieved, strong excited-state absorption in this system was found to prohibit laser oscillation.     

Hexafluoroacetone as a Protecting and Activating Reagent. <Emphasis Type="Italic">N</Emphasis>- and <Emphasis Type="Italic">O</Emphasis>-Glycosylation of Isoserine and Isocysteine

Summary. Starting from HFA-protected malic and thiomalic acid a series of O- and N-glycoconjugates suitable for peptide and depsipeptide modification has been synthesized.     

Einzelbestimmung einfacher Alkylphenole im ppb-Bereich in Trink- und Oberfl?chenwasser

Zusammenfassung Die einwandfreie analytische Bestimmung von Phenolen im ppb-Bereich sowie die Differenzierung natürlicher und künstlicher Phenole ist nach den bisherigen Methoden nicht oder nur unzureichend möglich. Daher wird eine Methode beschrieben, die nach einer dreistufigen Anreicherung um den Faktor 10000 und nach gleichzeitiger Abtrennung störender Begleitstoffe diese geringen Phenolkonzentrationen in den Arbeitsbereich der Papier- und Gas-Chromatographie bringt. Dadurch kann eine Einzelbestimmung der Phenole, Kresole und Xylenole in ppb-Konzentrationen durchgeführt und eine Unterscheidung zwischen industriellen Phenolen (C₆-C₈) und Phenolen biologischen Ursprungs (vorwiegend höhere Phenolderivate) getroffen werden.

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Summary By the methods hitherto applied the correct analytical determination of phenols in the ppb-range as well as the differentiation of natural and artificial phenols has not or only inadequately been possible. Therefore, a method is described to increase these low concentrations of phenols up to the range required for paper or gas chromatography after enriching the phenols by a factor of 10,000 and eliminating disturbing substances. This permits an individual determination of phenols, cresols, and xylenols in the ppb-range and also a distinction between industrial phenols (C₆-C₈) and phenols of biological origin.

     

Rohrströmung mit schwachem Drall

Summary The steady laminar flow at high Reynolds' numbers in a straight tube of circular cross-section is investigated under the condition that swirl is present. Given any axially symmetrical distribution of the rotational velocities, the flow downstream is calculated in the special case that the rotational velocities are small compared to the axial velocity. The problem is reduced to an eigen-value problem of an ordinary linear differential equation of second order, the theory of which is developed in detail. Numerical values for the five lowest eigen-values and the corresponding eigen-functions are given. As an example, the decay of an initially rigid rotation is considered.

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HerrnFr. A. Willers zum siebzigsten Geburtstag     

Ultrafast core-hole-induced dynamics in water probed by x-ray emission spectroscopy

The isotope effect and excitation-energy dependence have been measured in the oxygen K-edge x-ray emission spectrum (XES). The use of XES to monitor core decay processes provides information about molecular dynamics (MD) on an ultrafast time scale through the O1s lifetime of a few femtoseconds. Different nuclear masses give rise to differences in the dynamics and the observed isotope effect in XES is direct evidence of the importance of such processes. MD simulations show that even the excitation-energy dependence in the XES is mainly related to differences in core-excited-state dynamics.