Die innere Struktur von Proton und Neutron

The Science of Nature -     

Application of flotation for the separation of metal-loaded zeolites

Several industrial wastewater streams may contain heavy metal ions, which must be effectively removed, before the discharge or reuse of treated waters could take place. Different bonding materials, presenting selectivity and fast reaction kinetics for the removal of metals, have been examined for this purpose. The objective of the present paper was to investigate the application of dispersed-air flotation for the separation of metal-loaded sorbents. Two similar zeolite samples were applied as effective bonding agents for the removal of zinc, a toxic metal commonly found in many industrial wastewaters. This combined process, termed sorptive flotation, involves the preliminary scavenging of metal ions, by using the appropriate sorbent particles (usually present as ultrafine particulates), followed by flotation for the effective separation of them. The obtained results were very promising, as both metal and sorbent were effectively removed/separated from the dispersion.     

Molecular phylogeny of the American <Emphasis Type="Italic">Callinectes</Emphasis> Stimpson, 1860 (Brachyura: Portunidae), based on two partial mitochondrial genes

The genus Callinectes encompasses 16 species of commercially important swimming crabs. Most (13) occur on the Pacific and Atlantic coasts of the Americas. We compare mtDNA regions corresponding to 964 basepairs of the large (16S) and small (12S) ribosomal subunits among American Callinectes in order to examine phylogenetic relationships. The status of Callinectes affinis Fausto-Filho and Callinectes maracaiboensis Taissoun is questioned, and C. maracaiboensis is concluded to be a junior synonym of Callinectes bocourti A. Milne-Edwards, from which it cannot be consistently distinguished. We find two major lineages, one of which includes C. affinis, C. bocourti, Callinectes rathbunae Contreras, Callinectes sapidus Rathbun, and Callinectes toxotes Ordway. A second lineage is comprised of Callinectes arcuatus Ordway, Callinectes bellicosus (Stimpson), Callinectes danae Smith, Callinectes exasperatus (Gerstaecker), Callinectes larvatus Ordway, Callinectes ornatus Ordway, and Callinectes similis Williams. Definition of these clades is supported by previously described morphological differences in the length of the gonopods and shared physioecological adaptations. A calibrated molecular clock is used to estimate divergence of the two lineages near 13 mybp. Our analyses suggest that C. ornatus is the closest relative of C. arcuatus, and that C. affinis is closest to C. bocourti.     

Bestimmung von Mineralölkohlenwasserstoffen im Boden

The infra-red (IR) and the gas Chromatographic (GC) methods for the determination of mineral oil hydrocarbons in soils were examined in collaborative trials with regard to their accuracy and reproducibility. Natural, homogenized soils and soils spiked with mineral oil were used as standards. The soil matrix was composed relatively simply. The repeatability and reproducibility values obtained were about 5 % und 23 %, respectively. In contrast, the GC method revealed a considerably higher error range, especially by using the split/splitless technique. The degradation of mineral oil hydrocarbons in soils under different temperatures was investigated by IR throughout one year. The degradation rate at room temperature was about 25 %; at lower temperatures no degradation was detected. Thus, the spiked soils may be used as calibration standards for the mineral oil analysis.     

Carbon fixation and analysis of assimilates in a coral-dinoflagellate symbiosis

Freshly collected pieces of the hermatypic coral Acropora cf. scandens containing dinoflagellate endosymbionts (presumably Gymnodinium microadriaticum) were allowed to assimilated ¹⁴C from H¹⁴CO ₃ ^- in the light and in the dark. Time-dependent carbon uptake resulted in intense ¹⁴C-labelling of ethanol-soluble as well as of insoluble assimilates. About forty ¹⁴C-labelled assimilates have been identified. Polymeric (ethanol-insoluble) compounds achieve about 30% of total radiocarbon incorporation after 60 min incubation. Kinetics of ¹⁴C-labelling of single assimilates are analyzed. Percentages of typical photosynthates in the soluble fraction undergo characteristic time-dependent changes. Lipids proved to be the main accumulation products of carbon assimilation by incorporating more than 50% of ¹⁴C after 60 min photosynthesis. The data indicate that low-molecular weight photosynthates such as ¹⁴C-glycerol and ¹⁴C-glucose are rapidly converted to constituents of the polymeric fraction(s) of the coral. Besides peptides, polysaccharides, and lipophilic substances, considerable amounts of ¹⁴C are confined to skeletal CaCO₃ of the coral. The results are discussed with respect to trophic and metabolic interrelationships between the autotrophic dinoflagellates and the A. cf. scandens tissues.