1,720,959 research outputs found
Adsorption of alizarin, Eriochrome blue black R, and fluorescein using different iron oxides as adsorbents
Get PDFThis work presents kinetic and thermodynamic analysis of the adsorption of three dyes: alizarin, eriochrome blue black R, and fluorescein onto goethite, Co-goethite, and magnetite of medium Brunauer-Emmett-Teller surface area. The adsorption of the dyes on the oxides is fast. Fluorescein exhibits the lowest level adsorption for all adsorbents with goethite being the most efficient adsorbent when milligrams of dye per gram of oxide are considered. The Langmuir isotherm is the most appropriate for describing the adsorption data for the following systems: alizarin-magnetite and eriochrome and fluorescein with the three adsorbents, while alizarin-goethite and alizarin-Co-goethite show better fits with Freundlich isotherm. Molecular modeling using MM2 was used to analyze the steric effects on adsorption.Fil: Pirillo, Silvina. Universidad Nacional del Sur. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; Argentin
The effect of pH in the adsorption of Alizarin and Eriochrome Blue Black R onto iron oxides
Get PDFThe adsorption process of two dyes as a function of pH on three different adsorbents (goethite, Co-goethite, and magnetite) has been analyzed. Typical anionic adsorption behavior was observed for both dyes onto goethite and Co-goethite. The adsorption level was practically constant in the range of pH studied when the adsorbent was magnetite. The constant capacitance model (CCM) was employed to fit the experimental results. The surface complexes proposed from the adsorption data were in agreement with the patterns obtained from FTIR spectroscopy and a molecular mechanics calculation. Goethite has very good performance as adsorbent of Alizarin and Eriochrome Blue Black R. The presence of a foreign cation in Co-goethite does not improve the adsorption abilities of goethite. At low pH, the amounts of Alizarin and Eriochrome Blue Black R adsorbed on goethite and Co-goethite are similar. However, a higher dependence with the increase of pH is observed by Eriochrome Blue Black R. On magnetite, the dye adsorption shows less affinity for both dyes. Electronic and steric considerations can explain the trends found in the adsorption of the two dyes on the three iron oxides studied in this work. © 2009 Elsevier B.V. All rights reserved.Fil: Pirillo, Silvina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; Argentin
Density functional study of acrolein adsorption on Pt (111)
Get PDFThe electronic structure and bonding of acrolein (propenal) adsorption on Pt (111) were studied by density functional calculations (DFT). We optimized different adsorption configurations on the surface using the VASP code. The energetic study indicates that acrolein trans isomers are less stable on the Pt surface than cis configurations, which have a similar stability in all cases. We found that the inclusion of Van der Waals (vdW) corrections does not change the obtained adsorption geometries or preferential sites relative energies. We also analyzed the evolution of the chemical bonding changes in the adsorbate and the metal surface by crystal orbital overlap population (COOP) and overlap population (OP) analysis of selected bonds. Except for the h1 configuration, the adsorption of acrolein on the surface is mainly due to the formation of CePt bonds. We also found that the acrolein C pz orbital, perpendicular to the surface, play an important role in the adsorption, as well as Pt pz and dz 2 orbitals, whose lobes are well oriented to overlap with the adsorbate orbitals.Fil: Pirillo, Silvina. Universidad Nacional del Sur. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Química del Sur; ArgentinaFil: López Corral, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Química del Sur; ArgentinaFil: German, Estefania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; ArgentinaFil: Juan, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentin
Supported biocatalysts for Alizarin and Eriochrome Blue Black R degradation using hydrogen peroxide
Get PDFThe goal of this manuscript was to study the immobilization of horseradish peroxidase (HRP) and hematin on different supports at selected conditions to be used in the removal of two synthetic dyes: Alizarin Red (AR) and Eriochrome Blue Black R (EBBR). Reuse in the target reactions was tested for the best biocatalysts. Three supports were selected: magnetite-activated carbon Fe 3O 4/C, activated carbon C and chitosan CS. Several reasons led to discard the use of Fe 3O 4/C and C as supports for hematin and HRP. CS-glutaraldehyde (GA)-HRP not only has low ability to remove EBBR, but also the enzymatic activity of HRP could not be separated from the dye adsorption on CS. However, some adsorptive functions of CS-GA were lost when HRP was supported on it. In the case of CS-GA-hematin, the most important factors for EBBR removal are dye concentration and mass of catalyst, whereas the temperature has almost no effect on the conversion of dye, considering in all cases the H 2O 2 concentration (0.021M) constant. There was not a marked decrease in the removal of AR even after the ninth reuse in the case of CS-GA-hematin. For EBBR removal, with CS-GA-HRP, in the second reuse the catalyst was completely deactivated, whereas with CS-GA-hematin this was found only in the fourth reuse.Fil: Pirillo, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Química; Argentin
A DFT study of cyclopropane adsorption on Pt(1 1 1) : electronic structure and bonding
No full textWe have studied the adsorption of cyclopropane (c-C3H6) on Pt(1 1 1) by means of the density functional theory (DFT). We have investigated the preferential adsorption geometry, considering different adsorption sites and bonding configurations for the molecular adsorbate. We have also computed the electronic structure and bonding interactions by means of density of states (DOS), crystal orbital overlap population (OPDOS), and overlap population (OP) analysis. Our results show a small preference for Bridge and Top adsorption sites with the cyclopropane ring parallel to the surface. PtC equilibrium distance is ∼3.5 Å and a weak bond is formed during adsorption. The main bonding interaction comes from the PtH overlap population. Pt 5pz orbitals play an important role in the bonding between c-C3H6 and the surface. We have found that Van der Waals (vdW) corrections to the energies improve the adsorption values without changing the preferential site geometries.Fil: German, Estefania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: López Corral, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Pirillo, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Juan, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Brizuela, Graciela Petra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentin
An accurate UV/visible method to quantify proteins and nzymes:Impact of aggregation, buffer concentration and the nature of the standard
Get PDFA simple, fast and low cost UV/visible based method to quantify proteins or enzymes is presented. This method avoids some drawbacks found using conventional techniques. Representative proteins and enzymes such as bovine serum albumin (BSA), insulin (Ins.), Rhizomucor meihei lipase (RML), Candida rugosa lipase (CRL) and horseradish peroxidase (HRP) were assayed as model. Experiments revealed that the aggregation of the enzyme/protein molecules in aqueous solution was the main cause of inaccurate results obtained with the simple UV/visible method. It was determined that aggregation of proteins/ enzymes in aqueous solutions follows a reversible mechanism that could be reverted by simple magnetic stirring treatment. The results achieved within this study warn about common error sources in protein quantification by UV/visible based methods and clearly shows the magnitude of the mistakes that could be achieved if aggregation and other factors are not considered.Fil: Lassalle, Verónica Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Pirillo, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Rueda, Elsa Haydee. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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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