Modeling Steady-State Biofilms with Dual-Substrate Limitations

This Technical Note presents a systematic analysis of a steady-state biofilm model for the simultaneous utilization of an electron donor and an electron acceptor. It shows that the flux of the electron donor is balanced by the flux of the electron acceptor and the concentrations of the two substrates linearly depend on each other in a steady-state biofilm. An analytical solution can be derived for the substrate fluxes into the biofilm as direct functions of the bulk substrate concentrations. This analytical solution, not much more complicated than the one given by the classic single-substrate biofilm model, eliminates the need to identify the rate-liming factor from the two substrates prior to using it. Comparing the single-substrate and the dual-substrate biofilm models shows that the difference between the two for predicting the flux of the limiting substrate of a deep biofilm can be significant when the bulk concentration of the nonlimiting substrate becomes comparable with or less than its Monod half-saturation constant.     

Metallchelate ungesättigter 1,2-Dithioäther

Metal Chelates of Unsaturated 1,2-Dithioethers The dialkyl- and diaralkyldithioethers of ethylenebisthiol (edt) and xylenedithiol form cationic 1:2 chelates with the d⁸-metal ions Ag^I and Cu^I, which have been isolated and characterized. Pd^II- and Pt^II-halides yield neutral mixed ligand complexes of the type Me (L L) X₂ (L L = dithioether, X = halogen). The dibenzyldithioether of edt is cleaved oxidatively by Cu^II and yields dibenzyldisulfide, Cu^I and an unidentified product.     

cis-Diaminedichloroplatinum(II) complexes reversibly bound to water-soluble polyaspartamide carriers for chemotherapeutic applications. II: Platinum coordination to ethylenediamine ligands attached to poly(ethylene oxide)-grafted carrier polymers

In continuation of previous investigations aiming at the development of macromolecular metal complexes for biomedical use, this communication describes poly(alkylene oxide)-grafted polymeric platinum complexes. The platinum-containing macromolecules are obtained from presynthesized polyaspartamide carriers bearing poly(ethylene/propylene oxide) side chains and hydroxyethyl side groups as hydrosolubilizing units in addition to ethylenediamine side group terminals for metal coordination. Platination is brought about by treatment of the carriers with tetrachloroplatinate(II) ion in aqueous solution at 25–60°C. pH 4–6. The polymeric products, purified by dialysis in aqueous solution, are isolated by freeze-drying in yields of 60–80%. Platinum contents are in the range of 4–15%. The metal is bound to the carrier through chelation with the ethylenediamine ligands, forming square-planarcis-dichloroethylenediamine-platinum(II) complex species as side-chain terminals. Initially, the product polymers dissolve smoothly in water. Although on room-temperature storage in the solid state they gradually turn insoluble as a consequence of intermolecular solid-state interaction, solubility is retained on low-temperature storage and in frozen aqueous solutions.     

Crosslinking of atactic polypropylene by the system peroxide-pentaerythritol tetraallyl ether

The influence of the concentration of peroxide (mainly dicumyl peroxide) and pentaerythritol tetraallyl ether as coagent and the effect of temperature on the crosslinking of atactic polypropylene (a-PP) with molar mass 12 000g/mol were investigated. Using this system, crosslinking of 40mass% of a-PP at 160°C was obtained. The problems associated with the mechanism for crosslinking of a-PP are discussed.