Detachment from biofilms was evaluated using a mixed culture biofilm grown on primary wastewater in a tube reactor. The growth of biofilms and the detachment of biomass from biofilms are strongly influenced by hydrodynamic conditions. In a long-term study, three biofilms were cultivated in a biofilm tube reactor. The conducted experiments of biofilm growth and detachment can be divided into three phases: 1) an exponential phase with a rapid increase of the biofilm thickness, 2) a quasi-steady-state with spontaneous fluctuation of the biofilm thickness between 500 and 1,200 microm in the investigated biofilm systems, and 3) a washout experiment with increased shear stress in three to four steps after several weeks of quasi-steady-state. Whereas the biofilm thickness during the homogeneous growth phase can be regarded constant throughout the reactor, it was found to be very heterogeneous during the quasi-steady-state and the washout experiments. Growth and detachment during all three phases was simulated with the same one-dimensional biofilm model. For each of the three phases, a different detachment rate model was used. During the homogeneous growth phase, detachment was modeled proportional to the biofilm growth rate. During the quasi-steady-state phase, detachment was described by random detachment events assuming a base biofilm thickness. Finally, the washout experiment was simulated with detachment being a function of the biofilm thickness before the increase of the shear stress.

Es wird über 1H‐NMR‐Untersuchungen an Isophorondiamin (IPDA) und Isophorondiisocyanat (IPDI) sowie ausgewählter Folgeprodukte berichtet. Dem jeweiligen Hauptisomeren wurde zweifelsfrei die trans‐Konfiguration zugeordnet. Ebenso werden die 13C‐NMR‐Daten für eine Vielzahl von Folgeprodukten des n‐Butylisocyanats mitgeteilt. Mit Hilfe dieser Daten ist es nunmehr möglich, Abkömmlinge (cyclo)aliphatischer Isocyanate sicher zu charakterisieren. Das Datenmaterial ist auch in Hinblick auf die Analytik von Oligo‐ und Polymeren von Interesse.

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Ausgehend von petrochemischen Produkten auf der Basis Propylen oder Isobutylen werden eine Reihe neuer Synthesen fur 3,SDialkylpyridine beschrieben. So erhalt man au s2-Hydroxymethyl-2-methyl-l,3-propandiol (7), (3-Methyloxetan-3-y1)methanol (6), 2-Methylacrolein (8), Propionaldehyd-Formaldehyd-Aldoladdukten, 2-Methylen-1,3-propandiol (10) oder dessen Diacetat und Ammoniak, Methylamin oder Dimethylamin in Gegenwart von Katalysatoren unter Druck bei hoherer Temperatur 3,5-Dimethylpyridin (9). 3,5-Diathylpyridin (3) und 3,5-Dipentylpyridin sind aus den Homologen zuganglich. New Syntheses for 3,5-DialkylpyridinesA number of new syntheses for 3,5-dialkylpyridines using petrochemical compounds based on propene or isobutene is described. Thus 3,5-dimethylpyridine (9) is obtained when 2-hydroxymethyl-2-methyl-l,3-propandiol (7), (3-methyloxetan-3-yl)methanol (6), 2-methylacrolein (8) propionaldehyde-formaldehyde-aldol adducts, 2-methylene-l,3-propanediol(lO) or its diacetate are autoclaved with ammonia, methylamine or dimethylamine at elevated temperatures in the presence of catalysts. 3,5-Diethylpyridine (3) and 3,5-dipentylpyridine can be obtained from thc homologous compounds.3,5-Dialkylpyridine sind bisher wenig bearbeitet worden 1). Ihr Oxidationsprodukt, die Pyridin-3,5-dicarbonsaure, wurde lediglich durch spezielle, aufwendige Synthesen hergestellt 2 ) .Im Rahmen unserer Arbeiten fanden wir einige neue Synthesewege fur 3,5-Dimethylund 3,5-Diathylpyridin, durch die diese Verbindungen am petrochemischen GroBprodukten zuganglich werden.