1,720,973 research outputs found
Bioleaching of marmatite flotation concentrate with a moderately thermoacidophilic iron-oxidizing bacterial strain
No full textBioleaching of a marmatite flotation concentrate with a moderately thermoacidophilic iron-oxidizing bacterial strain (MLY) was investigated in batch experiments. Experimental results showed that the dissolution rate of marmatite was influenced markedly by pH, temperature, pulp density and particle size of ore. The bioleaching of the concentrate by the moderate thermophile was more effective when carried out under the higher acidity and temperature compared with Acidithiobacillus ferrooxidans. The adapted strain of the moderate thermophile could provide more rapid and complete oxidation of marmatite than its original strain and in the sterile control. (c) 2005 Elsevier Ltd. All rights reserved
Mechanism of wavy vortex and sign laws in flow past a bluff body: vortex-induced vortex
No full textAs reported in a previous work by Lin et al. (Acta Mech Sin, 2018. 10.1007/s10409-018-0758-z In the present paper, the theory of a vortex-induced vortex is introduced to explore mechanisms in a wavy vortex and applicable sign laws for uniform and incompressible flow past a fixed bluff body. Based on the analysis of the nearest-wall flow, two vortex-induced models for streamwise and vertical vortex pairs, respectively, are proposed under two boundary cases, denoting the induced vorticity introduced or distributed on and near the walls. As a result, the first sign law, for only streamwise and vertical components of vorticity, and the second sign law, for three components of vorticity, are obtained under their own particular conditions. The first sign law reveals the intrinsic physical relationship between streamwise and vertical vorticities, independent of the distribution of spanwise vortices in the whole flow field. It is also confirmed that the spanwise vortices, as well as the shear layers and wake width, distributed wavily across the span, are attributed to the introduced streamwise or vertical vortices. The two sign laws for vorticity are independent of the disturbed spanwise wavelength and the Reynolds number. Through the analysis of flow past the conic shroud, the two sign laws are successfully used to summarize typical spacial distributions of vorticity in three flow regions: on and near the front cylinder surfaces, the separated shear layers and the near wake.</p
Process Biochem.
No full textBioleaching processes of three zinc sulphides (marmatite, sphalerite and ZnS synthetically prepared) with Acidithiobacillus ferrooxidans and a moderately thermoacidophilic iron-oxidizing bacterium (MLY) were investigated by leaching experiments and electrochemical methods. Experimental results showed that marmatite had the highest dissolution rate in the presence of bacterial strains among the three zinc sulphides due to the difference of physicochemical property. Compared with synthetic ZnS, the part iron existed as pyrite contained in two concentrates and the dissolution of zinc sulphides was accelerated for galvanic cell effect. More Fe existed in the crystal lattice of marmatite solid solution were released to liquid phase and oxidized into Fe3+ ions by bacterial strains to accelerate the dissolution of marmatite during the bioleaching process. The bacterial leaching of zinc sulphides could become diffusion controlled when insufficient bacterial oxidation of the sulphur layer occurred, especially in the more rapid marmatite leaching reaction. The zinc sulphides bioleaching was significantly affected by mineralogical properties and leach solutions, which was supported by electrochemical measurements based on the working electrode of zinc sulphides-carbon paste electrode. The marmatite concentrate was more suitable for the extraction of zinc by the microbial leaching, when compared with the sphalerite and synthetic ZnS. (c) 2005 Elsevier Ltd. All rights reserved.Bioleaching processes of three zinc sulphides (marmatite, sphalerite and ZnS synthetically prepared) with Acidithiobacillus ferrooxidans and a moderately thermoacidophilic iron-oxidizing bacterium (MLY) were investigated by leaching experiments and electrochemical methods. Experimental results showed that marmatite had the highest dissolution rate in the presence of bacterial strains among the three zinc sulphides due to the difference of physicochemical property. Compared with synthetic ZnS, the part iron existed as pyrite contained in two concentrates and the dissolution of zinc sulphides was accelerated for galvanic cell effect. More Fe existed in the crystal lattice of marmatite solid solution were released to liquid phase and oxidized into Fe3+ ions by bacterial strains to accelerate the dissolution of marmatite during the bioleaching process. The bacterial leaching of zinc sulphides could become diffusion controlled when insufficient bacterial oxidation of the sulphur layer occurred, especially in the more rapid marmatite leaching reaction. The zinc sulphides bioleaching was significantly affected by mineralogical properties and leach solutions, which was supported by electrochemical measurements based on the working electrode of zinc sulphides-carbon paste electrode. The marmatite concentrate was more suitable for the extraction of zinc by the microbial leaching, when compared with the sphalerite and synthetic ZnS. (c) 2005 Elsevier Ltd. All rights reserved
Bioelectrochemistry
No full textThe electrochemical behaviors of a marmatite - carbon paste electrode with the chemical leaching of Fe3+ ions, or the microbial leaching using Acidithiobacillus ferrooxidans, were compared. The cyclic voltammograms of the electrode in the presence and absence of bacterial strains showed that the leaching process of marmatite was carried out by the different reactions occurring in the interface of the marmatite electrode - leach liquid. The polarization currents of the electrode under the differently applied potentials suggested that the microbial leaching of marmatite could be accelerated by the applied potential. The SEM observations indicated that the corrosion pits formed in the electrode surface were similar to the attached bacterial cells in shape and size, other than that by the chemical leaching of Fe3+ ions. The contact leaching of the attached cells on the mineral substrate played an important role on the dissolution of marmatite in addition to the chemical leaching of Fe3+ ions. (c) 2005 Elsevier B.V. All rights reserved.The electrochemical behaviors of a marmatite - carbon paste electrode with the chemical leaching of Fe3+ ions, or the microbial leaching using Acidithiobacillus ferrooxidans, were compared. The cyclic voltammograms of the electrode in the presence and absence of bacterial strains showed that the leaching process of marmatite was carried out by the different reactions occurring in the interface of the marmatite electrode - leach liquid. The polarization currents of the electrode under the differently applied potentials suggested that the microbial leaching of marmatite could be accelerated by the applied potential. The SEM observations indicated that the corrosion pits formed in the electrode surface were similar to the attached bacterial cells in shape and size, other than that by the chemical leaching of Fe3+ ions. The contact leaching of the attached cells on the mineral substrate played an important role on the dissolution of marmatite in addition to the chemical leaching of Fe3+ ions. (c) 2005 Elsevier B.V. All rights reserved
Electrochem. Commun.
No full textThe electrochemical behavior of marmatite-carbon paste electrode in the presence and absence of Acidithiobacillus ferrooxidans was investigated by electrochemical impedance spectroscopy (EIS) measurement. The effects of the concentration of Fe3+ ions, bacterial strain and temperature on the EIS spectra of the marmatite electrode were examined. The experimental data indicated that the impedance diagrams of the marmatite electrode in the different electrolytes had the similar features with two semicircles in the higher frequency range and a line in the lower frequency range. An equivalent circuit has been considered for the analysis of the EIS spectra of the marmatite electrode in the solution of 10 g/L Fe2+ ions without and with microorganisms. The fitting of experimental data along with a preliminary estimation for the characteristic parameters of the impedance model could validate the proposed mechanism, which suggested that the dissolution of marmatite proceeded by the similar kinetic processes occurring in the marmatite-solution interface in the different systems during the leaching process. (c) 2005 Elsevier B.V. All rights reserved.The electrochemical behavior of marmatite-carbon paste electrode in the presence and absence of Acidithiobacillus ferrooxidans was investigated by electrochemical impedance spectroscopy (EIS) measurement. The effects of the concentration of Fe3+ ions, bacterial strain and temperature on the EIS spectra of the marmatite electrode were examined. The experimental data indicated that the impedance diagrams of the marmatite electrode in the different electrolytes had the similar features with two semicircles in the higher frequency range and a line in the lower frequency range. An equivalent circuit has been considered for the analysis of the EIS spectra of the marmatite electrode in the solution of 10 g/L Fe2+ ions without and with microorganisms. The fitting of experimental data along with a preliminary estimation for the characteristic parameters of the impedance model could validate the proposed mechanism, which suggested that the dissolution of marmatite proceeded by the similar kinetic processes occurring in the marmatite-solution interface in the different systems during the leaching process. (c) 2005 Elsevier B.V. All rights reserved
Bioleaching of marmatite flotation concentrate by adapted mixed mesoacidophilic cultures in an air-lift reactor
No full textBioleaching of marmatite flotation concentrate by the adapted strains of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans in mixed cultures was carried out at initial pH of 2.0, temperature of 35 degrees C, particle size of -42 mu m (over 90%), pulp density of 15% and air flow of 500 L min(-1) in a 10-L air-lift reactor. Experimental results showed that the addition of Fe(2+)ion was favorable to improving the growth and activity of leaching bacteria and increasing the dissolution rate of marmatite. In the leaching system with Fe 21 ions added, the weight loss of the concentrate was over 70%, the leaching ratio of zinc was over. 80% and the concentration of zinc ions in the leach liquor was about 50 g L-1 after 10 days of bioleaching. The technological feasibility of a microbiological process using the adapted strains of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans in mixed cultures for extracting zinc from a marmatite flotation concentrate has been demonstrated. (c) 2004 Published by Elsevier B.V
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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