1,720,983 research outputs found
Evaluación de la capacidad de adsorción acuosa de plomo mediante intercambiadores catiónicos preparados a partir de aserrín por medio del método de xantación.
No full textTesis (Químico) -- Universidad de Cartagena. Facultad de Ciencias Exactas y Naturales. Programa de Química, 2015El principal interés de este trabajo es modificar químicamente la superficie del aserrín con el fin de aumentar su capacidad para remover metales pesados de soluciones acuosas y evaluar su factibilidad para adsorber Pb, determinando sus capacidades de adsorción
Espectroscopia de Absorción Atómica. Manual teórico-practico
No full textTrabajo de ascenso - - Universidad de Cartagena. Facultad de ciencias Exactas y Naturales. Programa de Química Farmacia, 1997La presente investigación busca promover la implementación de prácticas, Espectroscopia de absorción atomic
Adsorción de mercurio y cadmio en carbón subbituminoso oxidado-xantado, sulfonado o activado y resina sintética comercial
No full textThe combustion of low rank coal produces environmental impacts due to its low heat of combustion and high heteroatom content which has promoted its alternative uses as an adsorbent. A subbituminous coal (CS) was oxidized with air at 150°C on a fixed bed for 4 hours and xanthated with carbon disulfide in a basic solution, at 30°C. The resulting xanthated coal (CX) was evaluated for the adsorption of Hg2+ and Cd2+ from 0,100, 1,000, 12.48, 124.8 y 998.3mg/L aqueous solutions; metal concentrations were determined by atomic absorption spectrometry. CX was compared against CS, a sulfonated CS, activated CS (CAp), a commercial activated carbon (CAC), and a commercial synthetic resin (RC) in terms of Hg2+ and Cd2+ adsorption. RC showed the highest adsorption capacity (concentration factor 98%) followed by theCX (concentration factor 96%). The adsorption of cadmium on the sulfonated CS was 0.56meq/g, lower than that of CX, 1.85meq/g. In general, Hg2+ was less adsorbed than Cd2+; the adsorption capacities decreased in the order: RC, CX, sulfonated CS, activated CS, CS, and CAC. CX showed a better Cd2+ adsorption, 81% against 15%, than a non-oxidized 40-hours-xanthated coal, which shows that oxidation of coal increased the amount of oxygenated groups that enhanced xanthation.La combustión del carbón de bajo rango produce impactos ambientales por su bajo calor de combustión y alto contenido de heteroátomos, lo que ha promovido sus usos alternativos, como adsorbente. Un carbón subbituminoso (CS), se oxidó con aire a 150°C, en un lecho fijo, durante cuatro horas y se xantó con disulfuro de carbono en solución bá- sica, a 30°C. Este carbón xantado (CX), se evaluó para la adsorción de Hg2+ y Cd2+ de soluciones acuosas de 0,100, 1,000, 12,48, 124,8 y 998,3mg/L; los metales, se determinaron por espectrometría de absorción atómica. CX se comparó con CS, CS sulfonado y CS activado (CAp), además de un carbón activado comercial (CAC) y una resina sintética comercial (RC), en términos de su capacidad de adsorción de metales. RC mostró la más alta capacidad de adsorción (factor de concentración 98%), seguido por CX (factor de concentración 96%). En general, el Hg2+ se adsorbió menos que el Cd2+ y las capacidades de adsorción siguieron el orden, de mayor a menor: RC, CX, CAp, CS, y CAC. CX también mostró una mejor adsorción de Cd2+, 81% vs. 15%, que un carbón xantado no oxidado, lo que muestra que la oxidación previa del carbón aumentó la cantidad de grupos oxigenados que, a su vez, aumentaron la xantació
Mercury and cadmium adsorption in subbituminous xanthated, sulfonated or activated carbon and commercial synthetic resin
No full textThe combustion of low rank coal produces environmental impacts due to its low heat of combustion and high heteroatom content which has promoted its alternative uses as an adsorbent. A subbituminous coal (CS) was oxidized with air at 150°C on a fixed bed for 4 hours and xanthated with carbon disulfide in a basic solution, at 30°C. The resulting xanthated coal (CX) was evaluated for the adsorption of Hg2+ and Cd2+ from 0,100, 1,000, 12.48, 124.8 y 998.3mg/L aqueous solutions; metal concentrations were determined by atomic absorption spectrometry. CX was compared against CS, a sulfonated CS, activated CS (CAp), a commercial activated carbon (CAC), and a commercial synthetic resin (RC) in terms of Hg2+ and Cd2+ adsorption. RC showed the highest adsorption capacity (concentration factor 98%) followed by theCX (concentration factor 96%). The adsorption of cadmium on the sulfonated CS was 0.56meq/g, lower than that of CX, 1.85meq/g. In general, Hg2+ was less adsorbed than Cd2+; the adsorption capacities decreased in the order: RC, CX, sulfonated CS, activated CS, CS, and CAC. CX showed a better Cd2+ adsorption, 81% against 15%, than a non-oxidized 40-hours-xanthated coal, which shows that oxidation of coal increased the amount of oxygenated groups that enhanced xanthation.La combustión del carbón de bajo rango produce impactos ambientales por su bajo calor de combustión y alto conte-nido de heteroátomos, lo que ha promovido sus usos alter-nativos, como adsorbente. Un carbón subbituminoso (CS), se oxidó con aire a 150°C, en un lecho fijo, durante cuatro horas y se xantó con disulfuro de carbono en solución bá-sica, a 30°C. Este carbón xantado (CX), se evaluó para la adsorción de Hg2+ y Cd2+ de soluciones acuosas de 0,100, 1,000, 12,48, 124,8 y 998,3mg/L; los metales, se determi-naron por espectrometría de absorción atómica. CX se com-paró con CS, CS sulfonado y CS activado (CAp), además de un carbón activado comercial (CAC) y una resina sintética comercial (RC), en términos de su capacidad de adsorción de metales. RC mostró la más alta capacidad de adsorción (factor de concentración 98%), seguido por CX (factor deconcentración 96%). En general, el Hg2+ se adsorbió me-nos que el Cd2+ y las capacidades de adsorción siguieron el orden, de mayor a menor: RC, CX, CAp, CS, y CAC. CX también mostró una mejor adsorción de Cd2+, 81% vs. 15%, que un carbón xantado no oxidado, lo que muestra que la oxidación previa del carbón aumentó la cantidad de grupos oxigenados que, a su vez, aumentaron la xantación.Incluye referencias bibliográfica
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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