Distribution of copper in the vicinity of a deactivated mining site at Carajás in the Amazon region of Brazil

In this work the re-fixation of mobilized copper (Cu) that was released from a deactivated pilot Cu ore dressing plant in the tropical rain forest at Southeastern Amazon (Carajás) was studied. Samples of top soils, decay leaf litter deposited on soils, roots and leaves of standing biomass were taken for the determination of Cu concentration in order to evaluate the distribution of it between different environmental compartments. In the sampling points near to the now extinct plant, total Cu concentrations in the soil reached an average value of 2140 microg g(-1) above the natural level of about 40 microg g(-1), being that bioavailable Cu estimated by DTPA method varied from 1.9 to 20.7% of this total. From the data was possible to calculate that the soil compartment is able to hold around 10 kg Cu/m(2) of ground. Roots of the standing biomass in that area hold around 17 g Cu/m(2), while the Cu content in leaves showed to be largely independent of the Cu level in the soil. Copper in the leaves was estimated as around 1g/m(2) of ground area. In turn, the decay leaf litter deposited on soil can hold about 1.6 g Cu/m(2). The terrestrial system surrounding the abandoned pilot plant demonstrated great buffer capacity to retain mobile Cu released by anthropogenic activities in the area.     

Isolation,characterisation and efficacy of the bacterial strain Lysinibacillus sphaericus YMM in biodegradation of malathion insecticide in liquid media

A new isolate of bacterium Lysinibacillus sphaericus YMM capable of degrading malathion insecticide in liquid media was isolated and characterised. Biodegradation factors were investigated using Plackett–Burman factorial design, and the rest of the insecticide was monitored by high-performance liquid chromatography analysis. The near optimum conditions for degradation of 200 mg malathion/L were 30 mL medium, 2% of L. sphaericus suspension (0.70 OD_600nm), pH 5,10 g/L glucose, 1.0 g/L NaCl, 0.3 g/L MgSO₄, 1.0 g/L NH₄Cl and incubation for 24 h without yeast extract and peptone or beef extract. In addition, the significant variables including the medium volume, inoculum and incubation time were further optimised using Box–Behnken response surface design. These conditions were found to be 30.10% medium and inoculum of 0.706 (OD_600nm) for 23.636 h of incubation to achieve 98.974% degradation. Therefore, L. sphaericus YMM showed a potential degradation of malathion. Further studies should be conducted to understand the mechanism of biodegradation in liquid media.     

Attributing the resistance against simulated tree gum of an acrylic/melamine film loaded with an active silicone additive to its surface free energy

The present work reports preparation of acrylic/melamine based clearcoats with different loadings of a functionalized polysiloxane additive. The resulting films were applied over a black basecoat automotive coating system. Dynamic mechanical thermal analysis (DMTA), contact angle measurement, optical microscopy and gonio-spectrophotometery were utilized to investigate the mechanical (viscoelastic/viscoplastic), surface and optical properties of the coating system before and after exposure to Arabic gum (simulated tree gum). The resistance of film surface against gum attack showed high dependence on gum adhesion to the films. It was revealed that depreciation of surface free energy of additive loaded films could greatly improve their behavior against gum, apparently due to their enhanced non-stick characteristic. Tg and loss peak height also increased, indicating that additive did not negatively influence coating curing state. However, at loading contents exceeding 4 wt% both Tg and loss peak height decreased, revealing that a phase separation had occurred. The improved resistance of films against Arabic gum was corresponded to the low clearcoat shrinkage and crack formation. Weaker interactions between gum and clearcoat surface was seen in presence of additive. The shape and size of defects (of gum exposed films) were also significantly changed.     

Stripper configurations for CO2 capture by aqueous monoethanolamine

Absorption/stripping with amine solvents is a practical tail end technology for CO₂ capture from coal-fired power plants. One of the inhibiting costs of this technology is the energy requirement for solvent regeneration in the stripper, but novel configurations can help reduce this requirement by making the process more reversible. This work looked at several configurations with varying levels of complexity to determine the most useful method for arranging process units. Evaluated configurations included multi-stage flash, multi-pressure columns, and advanced stripping columns. Using a higher number of pressure stages, packing in place of equilibrium flashes, and vapor recompression were all reasonable methods to reduce the overall equivalent work requirement, but the most significant improvement was seen with an interheated column. The interheated column and simple stripper required 33.4 kJ/mol CO₂ and 35.0 kJ/mol CO₂ of work, respectively, at their optimum lean loadings.     

From activity cliffs to target-specific scoring models and pharmacophore hypotheses

The role of activity cliffs in drug discovery projects is certainly two-edged: on the one hand, they often lead to the failure of QSAR modeling techniques; on the other, they are highly valuable for identifying key aspects of SARs. In the presence of activity cliffs the results of purely ligand-based QSAR approaches often remain puzzling, and the resulting models have limited predictive power. Herein we present a new approach for the identification of structure-based activity cliffs (ISAC). It uses the valuable information of activity cliffs in a structure-based design scenario by analyzing interaction energies of protein-ligand complexes. Using the relative frequency at which a protein atom is involved in activity cliff events, we introduce a novel visualization of hot spots in the active site of a protein. The ISAC approach supports the medicinal chemist in elucidating the key interacting atoms of the binding site and facilitates the development of pharmacophore hypotheses. The hot spot visualization can be applied to small data sets in early project phases as well as in the lead optimization process. Based on the ISAC approach, we developed a method to derive target-specific scoring functions and pharmacophore constraints, which were validated on independent external data sets in virtual screening experiments. The activity-cliff-based approach shows an improved enrichment over the generic empirical scoring function for various protein targets in the validation set.     

Photokatalytische Systeme. XXI. Zum Mechanismus der Photoreduktion von Kaliumchromat in Alkoholen

Photocatalytic Systems. XXI. On the Mechanism of the Photoreduction of Potassium Chromate in Alcohols The photolysis of crown ether complexes of potassium chromate in several alcohols has been investigated by e.s.r.-spectroscopy. Two different relatively long-lived Cr(V) intermediates formed by different reaction pathways have been observed. Radicalic oxidation products of the alcohols (alkoxy and hydroxyalkyl radicals as well as fragmentation products) and of the crown ether have been detected by spin trapping.