Zur strahlenchemischen Zersetzung von in Wasser gelöstem und auf Aktivkohle adsorboiertem p-Chlorphenol

Im Rahmen dieser Arbeit wurde die strahlenchemische Zersetzung von in Wasser gelöstem und auf Aktivkohle adsorbiertem p-Chlorphenol untersucht.

Bei der γ-Bestrahlung einer wäßrigen p-Chlorphenollösung (C₀ = 500 ppm) erfolgt eine Dechlorierung. Parallel dazu verläuft die Bildung einer braunen Substanz, bei der es sich wahrscheinlich um Huminsäure oder ein Huminsäurederivat hundelt.

Auf Aktivkohle adsorbiertes p-Chlorphenol wird dagegen im untersuchten Beladungshöhenbereich (zwischen 19 und 45 mg p-Chlorphenol/g wasserfreie Kohle) unter den Bedingungen der strahlenchemisch induzierten Oxydation zu den Mineralisierungs-produkten Chlorid, Wasser und Kohlendioxid abgebaut. Neben der γendosis und der Beladungshöhe des p-Chlorphenols beeinflussen Texfur und Oberflächenchemie der verwendeten Aktivkohlen die Zersetzungsraten.     

Role of alkali cations for the excited state dynamics of liquid water near the surface

Time-resolved liquid jet photoelectron spectroscopy was used to explore the excited state dynamics at the liquid water surface in the presence of alkali cations. The data were evaluated with the help of ab initio calculations on alkali-water clusters and an extension of these results on the basis of the dielectric continuum model: 160 nm, sub-20 fs vacuum ultraviolet pulses excite water molecules in the solvent shell of Na(+) or K(+) cations and evolve into a transient hydrated complex of alkali-ion and electron. The vertical ionization energy of this transient is about 2.5 eV, significantly smaller than that of the solvated electron.     

Time-resolved photoelectron spectroscopy of solvated electrons in aqueous NaI solution

Time-resolved photoelectron spectroscopy was used to study the energetics and dynamics of solvated electrons in aqueous solution. Solvated electrons are generated by ultrafast photodetachment in a 100 mM aqueous NaI solution. Initially, an ensemble of strongly bound ("cold") solvated electrons and an ensemble of weakly bound ("hot") electrons in an unequilibrated solvent environment are observed. We report an ultrafast recombination channel for the "hot" electrons with a rate of (800 fs)(-1) which is in competition with thermalization occurring with a rate of (1.1 ps)(-1). The thermalized electrons recombine with the iodide radical with a rate of (22 ps)(-1). About 35% of the thermalized electrons escape geminate recombination and form free, solvated electrons. The vertical detachment energy for the solvated electron is determined to be 3.40 eV. No indication for a surface-bound electron at lower binding energies was observed.     

Microcalorimetric investigations on the influence of propolis on the bacterium micrococcus luteus

Propolis or bee-glue is the third important product of honey bees after honey and wax. Known for thousands of years for its curative effects it is finding evermore attention in alternative and classical therapy in recent times against, e.g. infections, inflammations, dermatologic diseases and in wound healing.

Microcalorimetric experiments were performed on the influence of several propolis samples from Germany, Uruguay, Ethiopia and of a commercial propolis tincture on growth and metabolism of the recommended gram-positive bacterium Micrococcus luteus. Propolis extracts were prepared following established recipies for the water-soluble and insoluble components and the precipitate.

Addition of these extracts to a growing M. luteus culture in different growth phases resulted in a strong decline of the heat production rate, a prolongation of the lag phase or an introduction of a new, second lag phase, while the form of the calorimetric power-time curve remained unchanged. The calorimetric response showed a linear dependence on the propolis concentration. Although the quantitative gain of the extracts from the different propolis samples was nearly constant, the effects varied considerably between the specimens used.

The calorimetric investigations were supplemented by polarographic oxygen monitoring and by the standard agar well technique to determine the growth inhibition factor of the propolis extracts.     

On higher order variational analysis in one and three dimensions for soft boundaries

For some problems in liquid crystal physics we need to use the Euler equation and the corresponding boundary equation in the three-dimensional case with soft boundaries. As a further complication the free energy expression, which should be minimized, might contain some second-order and third-order derivatives. These higher-order derivatives will cause the spatial derivatives of the boundary normal to appear in the boundary equation. Explicit formulae are given for the Euler equation and the corresponding surface equations for a general case. As an example, the theory is applied to nematic liquid crystals, where the general Euler equations and surface molecular fields are derived, including the effects of an imposed electric field.     

Sehr einfaches syntheseprinzip für formyl-verzweigte kohlenhydrate vom streptose-typ

n-Butylvinyl ehters, prepared by Wittig olefination of aldos-3-ulose derivatives react upon osmium tetraoxide hydroxylation with immediate formation of

branched carbohydrates.