Ultrasonic Fabrication of Polymer Plate Reactors with a Surface Coating

Microreactors offer several advantages compared to the industrial scale when developing new chemical processes. Especially the production and investment costs are low if polymer microreactors are generated by ultrasonic processes. In order to observe the chemical reaction and the flow configuration, these microreactors need to be optically transparent, mechanically stable, and chemically inert to several reagents. The manufacturing process of a transparent polymer plate reactor with a chemically inert surface coating by ultrasonic fabrication is described. Experimental characterization of the microreactors showed that they are leak tight up to a pressure difference of at least 300 kPa and the mixing times are in the range of milliseconds.     

Nutrient redistribution by grazing cattle drives patterns of topsoil N and P stocks in a low-input pasture ecosystem

Nutrient cycles in grassland often involve net transfers from some areas to others. Here, we analyse patterns of N and P transfers by cattle in two grazing periods, and their relationships to soil P and N stocks in an unfertilised old pasture with a history of >50 years grazing. Net transfers were assessed from spatial patterns of nutrient ingestion and excretion. Total soil N and P were determined at 0–5, 5–10, 10–30 and 30–60 cm. All analyses were performed with a spatial resolution of 10 × 10 m² or higher. Data were geostatistically interpolated. Nutrients accumulated in the flat crest zone and were depleted in the steeper areas. Nutrient ingestion was less and excretion higher in the accumulation zone (and vice versa in the depletion zone) revealing that both components of grazer-driven net transfers of nutrients promoted the development of accumulation/depletion zones. Topsoil stocks of N and P were closely correlated with excreta density and net transfers of N (P < 0.001), whereas N and P at 30–60 cm displayed only weak or no correlation. Redistribution involved a small fraction of the soil stocks: nutrients grazed in two periods were equivalent to 0.8% of N and 0.2% of P of the whole pasture (0–60 cm). These factors suggest that topsoil nutrient distribution was modified by long-term stable patterns of net transfers of nutrients. The excess of N in the accumulation zone (N in accumulation zone minus N in depletion zone, in 0–60 cm) was 11 times larger than that of annual (i.e. short-term) net transfers; but for P, it was 30 times larger. This contrast likely derived from leaching/volatilization losses of N in the accumulation zone and only small inputs of biologically fixed N in the depletion zone. The nitrogen status of vegetation (Nitrogen Nutrition Index) had a strong effect on herbage production throughout the pasture, while the Phosphorus Nutrition Index indicated no limitation, except in urine patches.     

Congratulations to Vladimir Viktorovich Baulin

Soil Mechanics and Foundation Engineering -     

Enhanced π-π interactions between a C60 fullerene and a buckle bend on a double-walled carbon nanotube

In situ low-voltage aberration corrected transmission electron microscopy (TEM) observations of the dynamic entrapment of a C₆₀ molecule in the saddle of a bent double-walled carbon nanotube is presented. The fullerene interaction is non-covalent, suggesting that enhanced π-π interactions (van der Waals forces) are responsible. Classical molecular dynamics calculations confirm that the increased interaction area associated with a buckle is sufficient to trap a fullerene. Moreover, they show hopping behavior in agreement with our experimental observations. Our findings further our understanding of carbon nanostructure interactions, which are important in the rapidly developing field of low-voltage aberration corrected TEM and nano-carbon device fabrication.      

Synthesis and characterization of cytidine derivatives that inhibit the kinase IspE of the non-mevalonate pathway for isoprenoid biosynthesis

The enzymes of the non-mevalonate pathway for isoprenoid biosynthesis are attractive targets for the development of novel drugs against malaria and tuberculosis. This pathway is used exclusively by the corresponding pathogens, but not by humans. A series of water-soluble, cytidine-based inhibitors that were originally designed for the fourth enzyme in the pathway, IspD, were shown to inhibit the subsequent enzyme, the kinase IspE (from Escherichia coli). The binding mode of the inhibitors was verified by co-crystal structure analysis, using Aquifex aeolicus IspE. The crystal structures represent the first reported example of a co-crystal structure of IspE with a synthetic ligand and confirmed that ligand binding affinity originates mainly from the interactions of the nucleobase moiety in the cytidine binding pocket of the enzyme. In contrast, the appended benzimidazole moieties of the ligands adopt various orientations in the active site and establish only poor intermolecular contacts with the protein. Defined binding sites for sulfate ions and glycerol molecules, components in the crystallization buffer, near the well-conserved ATP-binding Gly-rich loop of IspE were observed. The crystal structures of A. aeolicus IspE nicely complement the one from E. coli IspE for use in structure-based design, namely by providing invaluable structural information for the design of inhibitors targeting IspE from Mycobacterium tuberculosis and Plasmodium falciparum. Similar to the enzymes from these pathogens, A. aeolicus IspE directs the OH group of a tyrosine residue into a pocket in the active site. In the E. coli enzyme, on the other hand, this pocket is lined by phenylalanine and has a more pronounced hydrophobic character.     

Industrial cultural determinants of technological developments: Skill transfer or power transfer?

This paper discusses the social effects resulting from the transfer of knowledge and skill both in the spheres of production and machine design. Relevant design determinants and their impact on technological developments are discussed within the theoretical framework of industrial cultures. Two types of skill transfer are analysed in connection with different production philosophies — one more Tayloristic, the other more workshop-oriented. Finally, the paper discusses the relation of both philosophies to the requirements of future production concepts.