Bio-mechanochemical synthesis of silver nanoparticles with antibacterial activity

By using a bio-mechanochemical approach combining mechanochemistry (ball milling) and green synthesis for the first time, silver nanoparticles (Ag NPs) with antibacterial activity were successfully synthesized. Concretely, eggshell membrane (ESM) or Origanum vulgare L. plant (ORE) and silver nitrate were used as environmentally friendly reducing agent and Ag precursor, respectively. The whole synthesis took 30?min in the former and 45?min in the latter case. The photon cross-correlation measurements have shown finer character of the product in the case of milling with Origanum. UV–Vis measurements have shown the formation of spherical NPs in both samples. TEM study has revealed that both samples are composites of nanosized silver nanoparticles homogenously dispersed within the organic matrices. It has shown that the size and size distribution of the silver nanoparticles is smaller and more uniform in the case of eggshell membrane matrix implying lower silver mobility within this matrix. The antibacterial activity was higher for the silver nanoparticles synthesized with co-milling with Origanum plant than in the case of milling with eggshell membrane.     

Simplification of separation of the reaction mixture after transesterification of vegetable oil

A heterogeneous reaction mixture is formed by transesterification of vegetable oils. The reaction mixture contains mainly methyl esters of higher fatty acids and glycerol. From this mixture, biodiesel is gained by spontaneous sedimentation in the gravitational field. The sedimentation can be considerably accelerated by controlled addition of water. It was found that addition of small amounts of water to the crude reaction mixture significantly affected the mixture, and substantial changes in the speed of the separation took place. Considerable differences in the composition and quality of the ester and glycerol phases occurred. The optical properties (transmittance and refractive indices) of the heterogeneous reaction mixture are changed after addition of water; this change can be observed spectrophotometrically. This method is applicable to all types of vegetable oils including waste frying oils.     

Multiscale modelling of nanoindentation test in copper crystal

The nanoindentation test in the dislocation free crystal of copper is simulated by a nonlinear elastic finite element analysis coupled with both ab initio calculations of the ideal shear strength and crystallographic considerations. The onset of microplasticity, associated with the pop-in effect identified in experimental nanoindentation tests (creation of first dislocations), is assumed to be related to the moment of achieving the value of the ideal shear strength for the copper crystal. Calculated values of the critical indentation depth lie within the range of experimentally observed pop-ins in the copper crystal. The related indentation load is somewhat lower than that observed in the experiment.     

Neue Methode zur Unterscheidung der Rohmilch von dauer- und momenterhitzter Milch

Ohne Zusammenfassung     

Spatial Directional Radiance Caching

We present a new approach for accelerated global illumination computation in scenes with glossy surfaces. Our algorithm combines sparse illumination computation used in the radiance caching algorithm with BRDF importance sampling. To make this approach feasible, we extend the idea of lazy illumination evaluation, used in the caching approaches, from the spatial to the directional domain. Using importance sampling allows us to apply caching not only on low-gloss but also on shiny materials with high-frequency BRDFs, for which the radiance caching algorithm breaks down.     

Alumina/MWCNTs composites by aqueous slip casting and pressureless sintering

Slip casting of stabilized aqueous suspensions followed by pressureless sintering was used for preparation of dense Al₂O₃/MWCNTs composites. The suspensions were stabilized by commercial polyelectrolyte dispersant Darvan C–N. In order to increase the stability, the pH value of the suspension was adjusted to ∼10. At this pH the highest ζ-potential values of the alumina powder and of the MWCNTs functionalised in boiling nitric acid were achieved. Two different agents, namely ammonium hydroxide and sodium hydroxide, were used for the pH adjustment. Their influence on the viscosity of suspensions and on consolidation and densification behaviour of the Al₂O₃/MWCNT composites was evaluated. The effect of ammonium hydroxide was more pronounced, as confirmed by lower viscosity of the suspension, higher sintered density, and fine-grained microstructure of the sintered composites. The Al₂O₃/t-MWCNTs composites with 0.1 wt% of the MWCNTs, with 99.9% relative density, the mean size of alumina grains ∼1 μm, and homogeneously distributed carbon nanotubes were prepared by the pressureless sintering at 1500 °C.     

Biomass ash-based mineral admixture prepared from municipal sewage sludge and its application in cement composites

Biomass as the biodegradable fraction of both agricultural products and industrial and municipal waste is currently a versatile energy resource. It can be stored and converted in practically any form of energy carrier and also into biochemicals and biomaterials from which, once they have been used, the energy content can be recovered to generate electricity, heat, or transport fuels. Moreover, the residues of its incineration can often be reused as pozzolanic additions to cement which can be considered as an environmentally friendly way of their disposal. In this paper, municipal sewage sludge with the organic carbon content of 27% was used for the preparation of biomass ash that should potentially find use as environmentally friendly mineral admixture to construction binders. Based on physical and chemical characterization of the raw material that showed a suitable chemical and phase composition, organic matter in a significant amount, and no thermal decomposition processes above 700 °C, biomass ash was produced. The biomass ash was obtained by incineration of sewage sludge at 700 °C, and mechanical activation contained 52% of amorphous phase which correlates with its good pozzolanic activity. The concentration of heavy metals, soluble chlorides, nitrates, and sulfates in biomass ash is found well below the standard permissible values. The composites prepared with a biomass ash dosage of 10, 20, and 30 wt% of Portland cement exhibited good functional properties. The increase in porosity up to 6% and decrease in compressive strength up to 3% were satisfactory. The results of leaching tests showed that composites with biomass ash contain only trace amounts of chlorides, nitrates, and sulfates. Apparently, the chlorides contained in biomass ash (0.7 mg/g) were immobilized in the cement matrix because the amounts of leached chlorides (0.04 wt%) were the same for all composites and well below the permissible limit for concrete. As revealed by the X-ray diffraction and thermogravimetric analyses, a significant decrease in portlandite content with increasing biomass ash content confirmed the pozzolanic reaction in biomass ash containing composite mixes. The environmental assessment showed a significant decrease in both carbon dioxide production and energy consumption with the increasing biomass ash content. For the composite with 30% biomass ash dosage, it was 21% of CO₂ and 11% of energy, as compared with the reference mix. The combination of good functional and environmental parameters of the analyzed composites makes good prerequisites for their application in construction industry. Taylor-made mineral admixture on biomass ash basis can find a broad use as eco-efficient admixture to cement- and lime-based binders.