Results of experimental and theoretical investigations on generation of terahertz radiation at the interaction of femtosecond laser pulses with a metal surface are presented. Investigations are performed with the laser pulse intensities higher compared with that used in papers [Opt. Lett.29, 2674 (2004); Opt. Lett.30, 1402 (2005)]. The most effective generation is observed for p-polarized optical pulses with incidence angles in the range 5°-10° (from the surface), depending on the kind of metal. For the copper, the exponential growth of terahertz pulse energy with the increase of optical pulse energy was registered. Theoretical interpretation for some of the experimental results is proposed based on the model of free electrons in metal.
This study aims to establish the relationship between ambient parameters and the diversity, composition, and function of microbial communities that predominate at each stage of the co-composting of food and agricultural waste. Culture-based and culture-independent methods were used to investigate the changes in the microbiota. The favorable conditions of high initial humidity and C/N ratio caused a decrease in the richness and biodiversity of the microbiota when such conditions existed. During the thermophilic stage, the total microbial number increased, and active mineralization of organic matter was carried out by members of the genera Bacillus, Caldibacillus, Aspergillus, and Penicillium. The fungal community was sensitive to drastic temperature changes. Byssochlamys dominated among fungi during the transition from the mesophilic to the thermophilic stage and during cooling. The biodiversity increased with time and was associated with the dynamics of germination and nitrification indices, so that the more diverse the microbial community, the higher the properties of compost that stimulate plant growth and development. The microbial community of the mature compost, together with mineral plant nutrients ready for consumption and humic compounds, make this compost a good soil additive.
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