Mode selection and phase locking of sidelobe-emitting semiconductor laser arrays via reflection coupling from an external narrow-bandwidth grating

A phase locked array design, utilizing direct reflection feedback between adjacent cavities by an external grating, is analyzed and proposed. The narrow grating reflection bandwidth causes longitudinal mode selection, while the array geometry causes transverse wavenumber selection through the coupling strength. As a result, only one among the free running cavity eigenmodes can couple effectively into a phase locked collective eigenmode. The coupled array mode is experiencing the high reflectivity of the grating and surpasses the low gain of the free running modes, that experience only a much lower reflectivity from the cavity edge antireflective coating. These results suggest that in-phase locking and single mode operation can be achieved simultaneously through the use of an external narrow-bandwidth grating

Resistance of <i>Rhodococcus ruber</i> biofilms to CuO nanoparticles depending on exopolymer matrix composition

Background. The widespread use of copper oxide nanoparticles (CuO NPs) increases their release into the environment, which leads to accumulation in trophic chains. Bacterial biofilms are more resistant to physico-chemical factors compared to planktonic cells due to an exopolymer matrix (EPM) consisting of polysaccharides, proteins, lipids and nucleic acids. Rhodococcus actinobacteria are promising for environmental biotechnology due to biodegradation of petroleum products, pesticides and other organic pollutants, as well as bioaccumulation of heavy metals.   The aim. To investigate effects of CuO NPs on the viability of Rhodococcus ruber IEGM 231 cells in biofilms and the dynamics of EPM components.   Methods. R. ruber biofilms were grown on microscopy cover glass with CuO NPs and EPM components were studied using confocal laser scanning microscopy (CLSM) by differentiating staining with LIVE/DEAD to determine the number of living and dead cells, Nile Red for lipids, FITC for proteins and Calcofluor White for betapolysaccharides.   Results. It was found that R. ruber biofilms grown in a mineral medium with1.0 vol.% n-hexadecane are more resistant to CuO NPs compared to biofilms growing in a rich culture medium (meat-peptone broth). This was due to more intensive EPM formation, which plays a major role in protecting cells from the bactericidal action of nanometals. A weak stimulating effect of a low (0.001 g/l) concentration of CuO NPs on biofilm formation was registered. Dynamics and localization of main EPM components were monitored during prolonged (24–72 h) biofilm cultivation with CuO NPs. When exposed to high (0.01–0.1 g/l) concentrations of CuO NPs, a consistently high lipid content and an increase in concentrations of polysaccharides and proteins were revealed.   Conclusion. Understanding the complex interaction mechanisms of nanometals and biofilms will contribute to the development of effective biocatalysts based on immobilized bacterial cells. Also, the obtained data can be used to combat unwanted biofilms with the help of metal nanoparticles

Behaviour pattern of rock mass haulage energy intensity in deep pits

A significant portion of mineral deposits developed by open-pit mining is opened to the full depth by road transport ramps without the use of combined transport. In most cases, this is dictated by the high rate of a pit deepening and multi-stage development. In this study, the energy intensity of rock mass (RoM) haulage from the working zone of a pit to the surface is considered at several hierarchical levels. Mineframe software was used to study 3D-models of open pits with different slope angles in order to test the method of analytical calculation of a pit volume that allowed ensuring accuracy under a wide range of mining conditions. The findings of the research are as follows: with an increase in the pit bottom diameter, the zone of stabilization of rock mass lifting (haulage) height shifts to greater target depths. An increase in the pit slope angles entails shifting the weighted average height to deeper elevations. By increasing the pit target depth, combined modes of transport become more economical in comparison with dump trucks due to an increase in the total volume of rock mass. Depending on the comparison purpose, it was proposed to use different types of energy intensity. For a broad estimation of the rationality of the pair “scheme of opening – mode of transport” for open pits, the ratio of potential energy intensities of rock mass haulage of a considered option of a pit opening and its basic option without transport berms was used. The ratio of potential energy intensities as a function of a pit depth was determined. The values of total energy intensity of rock mass haulage from a pit to the surface were also established

Spontaneous magnetization of aluminum nanowires deposited on the NaCl(100) surface

We investigate electronic structures of Al quantum wires, both unsupported and supported on the (100) NaCl surface, using the density-functional theory. We confirm that unsupported nanowires, constrained to be linear, show magnetization when elongated beyond the equilibrium length. Allowing ions to relax, the wires deform to zig-zag structures with lower magnetization but no dimerization occurs. When an Al wire is deposited on the NaCl surface, a zig-zag geometry emerges again. The magnetization changes moderately from that for the corresponding unsupported wire. We analyse the findings using electron band structures and simple model wires.Comment: submitted to PHys. Rev.