Bulgarian Academy of Sciences

About: Bulgarian Academy of Sciences is a government organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Coupling constant & Catalysis. The organization has 17989 authors who have published 36276 publications receiving 642820 citations. The organization is also known as: Bulgarian Academy of Sciences，簡稱：BAS & Balgarska Akademiya na Naukite.

Degradation of keratin and collagen containing wastes by newly isolated thermoactinomycetes or by alkaline hydrolysis

Abstract: Aims: The aim of this study was to develop a method for microbial degradation of indigenous keratin wastes and to compare it with a method of alkaline hydrolysis Methods and Results: Native sheep skin and wool were chosen as a model mixture of collagen and keratin wastes discarded by the leather and fur industries Suitable conditions were found for hydrolysis of this mixture by four newly isolated thermoactinomycete strains Another set of experiments was carried out using alkaline hydrolysis of keratin wastes It was shown that microbial hydrolysates contained predominantly low molecular peptides and amino acids, including essential ones, while the alkaline hydrolysis produced predominantly peptides of higher molecular weight Conclusion: A simple and a low-cost method was proposed for rapid and effective biodegradation of keratin wastes using Thermoactinomyces strains Significance and Impact of the Study: The proposed method could find application in agriculture for preparing mixtures containing valuable peptides and amino acids

Femtosecond laser ablation of nickel in vacuum

Abstract: We present an experimental characterization and a theoretical analysis of ultrashort laser ablation of a nickel target, which highlights the more general and peculiar features of femtosecond (fs) laser ablation of metals. The study has been carried out by using visible (527 nm) laser pulses of ≈ 300 fs duration. The vacuum expansion dynamics of the ablated species has been investigated by using fast photography and optical emission spectroscopy, while the fs laser pulse–metal interaction has been studied theoretically by means of molecular dynamics simulations. Special attention has been given to the study of the dependence of ablation depth on laser fluence, which has been carried out by comparing the SEM analysis of micro-holes drilled into the nickel samples with the predictions of the theoretical model. The main outcomes of our investigation, which are very satisfactorily reproduced and accounted for by the theoretical model, are (i) the nonlinear dependence of the ablation yield on the laser fluence, and its reliance to the electron heat diffusion, in the process of redistribution of the absorbed energy, (ii) the splitting of the material blow-off into two main classes of species, atoms and nanoparticles, characterized by different expansion dynamics, and (iii) the different degrees of heating induced by the laser pulse at different depths into the material, which causes the simultaneous occurrence of various ablation mechanisms, eventually leading to atoms and nanoparticles ejection.