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Search Results: 1 - 10 of 3392 matches for " Elemental análisis "
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Composición elemental y contenido de metales en sedimentos marinos de la bahía Mejillones del Sur, Chile: evaluación ambiental de la zona costera Elemental composition and metal contents in the marine sediments of Mejillones del Sur Bay, Chile: an environmental assessment of the coastal zone
Jorge Valdés,Abdel Sifeddine
Latin american journal of aquatic research , 2009,
Abstract: Se midió la concentración de carbono total, nitrógeno total, azufre total, materia orgánica, Ni, Cd, Pb, Cu y Zn en sedimentos costeros (10 m de profundidad de columna de agua) de ocho sectores de la bahía Mejillones. La composición elemental de los sedimentos sería el resultado de la abundante materia orgánica autóctona presente en este sistema costero. El orden de abundancia de los metales analizados fue: Zn > Cu > Ni > Pb > Cd. La concentración de metales no se explicaría por el contenido de materia orgánica ni la composición granulométrica de los sedimentos costeros. La evaluación del contenido de metales en los sedimentos, mostró que el Ni, Zn y Pb estarían levemente enriquecidos en la actualidad, aún cuando los valores se mantienen dentro de un rango cercano a los niveles preindustriales. El análisis del dendrograma de similitud de los sectores de estudio separó la línea de costa de Mejillones en dos grandes zonas; una asociada a la actividad industrial desarrollada en la bahía, y otra correspondiente al área de desarrollo urbano de Mejillones con características similares a aquellos ambientes libres de actividad antrópica directa. The total carbon, total nitrogen, total sulphur, organic matter, Ni, Cd, Pb, Cu, and Zn concentrations were measured in coastal sediments (10 m water depth) at eight stations in Mejillones Bay. The elemental composition of these sediments is a function of the autochthonous organic matter generated in this coastal system. The order of abundance for the metals was: Zn > Cu > Ni > Pb > Cd. The metal content is not explained by the organic matter content or grain size of these coastal sediments. The evaluation of the concentration metals in the sediments showed that Ni, Zn, and Pb are slightly enriched at the present, although with values that are similar to preindustrial concentrations. A cluster analysis of the similarity in the study area separated the Mejillones coast into two main zones: one related to the industrial activity developed in this bay and the other related to the urban develop of Mejillones city, with characteristics similar to environments free of direct human activity.
New observations on a pottery fragment with incised deer from the Cova de l’Or (Beniarés, Alacant)
Domingo Sanz, Inés,Roldan García, Clodoaldo,Ferrero Calabuig, José,García Borja, Pablo
Trabajos de Prehistoria , 2007,
Abstract: The red external surface of a vessel, decorated with an incised group of deer from Cova de l’Or, has been long considered characteristic of the application of the almagra technique. However, the results of the elemental analysis of this fragment, compared with the results of another vessel with almagra decoration from the same site, call into question the application of this technique in the first vessel. In addition, searching for parallels for the schematic incised motifs of the vessel, in both ceramic decorations and rock art, we have concluded that rather than deer the represented animals are hinds. La coloración rojiza de la superficie externa del fragmento cerámico con decoración de cervidos incisos de la Cova de l’Or se ha interpretado tradicionalmente como evidencia de la aplicación de la técnica de la almagra. Sin embargo, el análisis elemental del fragmento y la comparación de los resultados con los obtenidos a partir de otro fragmento con decoración a la almagra del mismo yacimiento, permite cuestionar la utilización de dicha técnica en el primero de ellos. Así mismo, la búsqueda de paralelos para los motivos esquemáticos incisos del vaso, tanto entre las decoraciones cerámicas como en arte parietal, nos lleva a sugerir que más que ciervos pudiera tratarse de representaciones de ciervas.
Carnap y Husserl: a propósito de la constitución de la experiencia Carnap and Husserl: About Constitution of the Experience
Carlos Alberto Cardona Suárez
Diánoia , 2010,
Abstract: En el presente artículo se desarrollan tres tareas. (i) Se presenta un mapa de posibles y antagónicas lecturas del Aufbau de Carnap y se favorece una lectura kantiana con rasgos fenomenológicos. (ii) Se identifica críticamente una dificultad central del Aufbau cuando se exige el carácter instantáneo de las experiencias elementales. (iii) Se propone una alternativa para minimizar la dificultad atendiendo algunas sugerencias propuestas por Husserl en Experiencia y juicio, aun cuando se advierte acerca de la necesidad de formular serias revisiones a la geometría conceptual del Aufbau. This paper carries out three tasks. (i) It presents a map of possible and antagonistic readings of Carnap's Aufbau and suggests a Kantian reading with phenomenological features. (ii) A central difficulty of the Aufbau is identified when the instantaneous feature of the elementary experiences is demanded. (iii) A possibility of minimizing this difficulty is presented using some suggestions proposed by Husserl.
Effect of Surface Treatment on Elemental Composition of Recast NiCr Alloy  [PDF]
Tevfik Yavuz, Asl? Acar, Serhan Akman, Atiye Nilgun Ozturk
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.33025
Abstract: Objective: The aim of this study was to compare the effects of different surface treatments on the elemental composition stability of as-received and recast types of NiCr casting alloys. Material and Methods: Six commercial NiCr dental casting alloys (Kera N, Nodelco, Bellabond, Wiron 99, Metaplus VK, and Tritech D) were used in this study. Seventy-two specimens (12 × 12 × 1.2 mm) were produced using the lost-wax casting process. Three casting protocols were established in relation to the proportion of as-received and recast alloys: Group A (100% as-received metal), Group B (50 wt% new metal, 50 wt% once-recast metal), and Group C (100% once-recast metal). Two specimens in every group received two different surface treatments: sandblasting with 110 μmm Al2O3 or oxidation firing. An elemental analysis was performed with x-ray energy-dispersive spectroscopy. Results were subjected to one-way analysis of variance and Tukey HSD tests. Results: The elemental composition was significantly different in the casting groups and treatment groups (p < 0.05). The lowest mean weight percentage Ni value was recorded for Group C and the highest for Group A. Aluminum-oxide sandblasting of the alloy surface reduced the mean weight percentage for Cr. Conclusion: Recasting metal alloys may adversely affect surface quality.
Assessment Of Beneficiation Routes Of Tantalite Ores From Key Locations In Nigeria  [PDF]
A. R Adetunji, W.O. Siyanbola, I. I Funtua, S. O. O. Olusunle, A.A Afonja, O.O. Adewoye
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2005, DOI: 10.4236/jmmce.2005.42008
Abstract: The beneficiation methods for some tantalite ores from selected deposits in Nigeria have been assessed through mineralogical and compositional analyses of the ores. Tantalite ores obtained from eight different well-known locations of the mineral in the country were analyzed with 109Cd excitation source Energy Dispersive X-ray spectrometry using the emission-transmission method of quantification. The major minerals detected and quantified include TiO2, MnO, Fe2O3, Ta2O5, Nb2O5, WO3, Th and U. Impurity elements such as Hf, Zn, Zr, Co, Pb, Rb, and Y were also observed and evaluated. Our analyses further show that Ta2O5 in the ores ranged from a minimum concentration of about 8% in Otu to about 60% in the Egbe deposits, while the Nb2O5 concentrations in the ores ranged from about 20% to 37.5% with the highest coming from the Ofiki deposit. Based on these results and the work of other authors, we deduced that clean-up operations might be adequate for Ta extraction from most of the tantalite deposits in Nigeria. The consideration of simplicity and cost of process favours the direct dissolution of the ores in HF for the clean-up operations.
Evaluation of Effects of Synthetic Compound and Mineral Admixture on Crystal Structure of Concrete  [PDF]
Samuel Oloruntoba Olugbenga Olusunle, Theresa Chikwuo Ezenwafor, Bidemi Sikirat Jiddah-Kazeem, Akeem Kareem, Ojo Jeremiah Akinribide, Adekunle Taofeek Oyelami
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2015, DOI: 10.4236/jmmce.2015.33016
Abstract: The effects of mineral admixture on the internal morphology of concrete were studied and evaluated in this work. Portland cement with five different additives was used in the complex admixture. These includes: extracted silica from corn hob ash, synthetic calcium carbonate, synthetic calcium hydrogen carbonate, white and dark kaolin, each replacing 10% of cement in the concrete formulation. The additives and the pure cements were subjected to intensive mixing to ensure homogeneity prior to water addition, after which each undergoes casting and curing. Elemental characterizations of the additives indicated the presence of some elemental oxides and crystallography studies were carried out on the pure and reinforced concrete. The obtained result indicated crystallographic adjustments of the indigenous concrete which will definitely contribute to modifying its mechanical properties.
Physicochemical characteristics of ozonated sunflower oils obtained by different procedures
Díaz, M. F.,Sánchez, Y.,Gómez, M.,Hernández, F.
Grasas y Aceites , 2012, DOI: 10.3989/gya.073212
Abstract: Two ozonation procedures for sunflower oils at different applied ozone dosages were carried out. Ozone was obtained from medicinal oxygen and from air. Peroxide, acidity, and iodine indexes, along with density, viscosity and antimicrobial activity were determined. The fatty acid compositions of the samples were analyzed using GC. The content of oxygen was determined using an elemental analysis. Electronic Paramagnetic Resonance was used to measure the organic free radicals. The reactions were achieved up to peroxide index values of 658 and 675 mmolequiv kg–1 using medicinal oxygen and air for 5 and 8 hours, respectively. The samples of ozonized sunflower oil did not present organic free radicals, which is a very important issue if these oils are to be used as drugs. The ozonation reaction is more rapid with medicinal oxygen (5 hours) than with air (8 hours). Ozonized sunflower oil with oxygen as an ozone source was obtained with high potential for antimicrobial activity. Se ha aplicado dos procedimientos de ozonización a aceites de girasol a diferentes dosis de ozono, obteniendo el ozono a partir de oxígeno medicinal y de aire. Se han determinado los índices de peróxido, yodo y acidez conjuntamente con la densidad, viscosidad y la actividad antimicrobiana. La composición de ácidos grasos fue analizada mediante CG. El contenido de oxígeno fue determinado mediante Análisis Elemental. Se utilizó la resonancia paramagnética electrónica para medir los radicales libres orgánicos. Las reacciones fueron realizadas hasta valores de índice de peróxidos de 658 y 675 mmol-equiv kg–1 usando oxígeno medicinal y aire durante 5 y 8 horas, respectivamente. Las muestras de aceite de girasol ozonizado no presentaron radicales libres orgánicos, lo cual es muy importante en el caso de que estos aceites sean utilizados en medicina. La reacción de ozonización es más rápida cuando se utiliza oxígeno medicinal (5 horas) que el aire (8 horas). El aceite de girasol ozonizado con oxígeno como fuente de ozono presentó mayor potencial de actividad antimicrobiana.
Oleochemicals I: Studies on the preparation and the structure of lithium soaps.
Shoeb, Zein E.,Hammad, Bayed M.,Yousef, A. A.
Grasas y Aceites , 1999,
Abstract: Lithium stéarate, palmitate, myristate, laurate, caprate and caprylate were prepared by means of fusion method. Elementary analysis and the infrared absorptions spectra of the prepared lithium soaps as well as their X-ray diffractions and the thermogravimetric analyses were carried out. The anhydrous lithium salts of fatty acids with 12 carbon atoms or less showed thermal stability up to ca. 300 ± 78 °C depending on the chain length. On other hand the salts with 14 carbon atoms or more were decomposed at 126 ± 4 °C leading to formation of lithium carbonate. The homologous lithium soaps had very similar crystal structure among them and their metal -to- oxygen bonds were similar for the acyl chains between 8 and 18 carbons. However the angle of inclination of the molecular axes to the basal plane increased with the decreasing of the number of carbon atoms of the fatty acid chain, as determined by X-ray diffraction. In addition, the ionic character of the metal -to- oxygen bond was enhanced with the decrease of the number of carbon atoms as shown by infrared spectroscopy. Se han preparado estearato, palmitato, miristato, laurato, caprato y caprilato de litio por fusión. Se ha realizado el análisis elemental, los espectros de absorción en el infrarrojo y las difracciones de rayos X de los Jabones de litio preparados, además del análisis termogravimétrico de los mismos. Las sales de litio anhidra de los ácidos con 12 átomos de carbono o menos mostraron una estabilidad térmica hasta los 300 ± 78 °C dependiendo de la longitud de la cadena. Por otro lado las sales con 14 átomos de carbono o más se descompusieron a 126 ± 4 °C formándose carbonato de litio. Los jabones homólogos de litio mostraron una estructura cristalina similar, siendo los enlaces metal-oxígeno del mismo tipo para los ácidos grasos de número de átomos de carbono entre 8 y 18. Sin embargo el ángulo de inclinación que forma la molécula con el plano basal aumentó con la disminución del número de átomos de carbono, lo que se observó por difracción de rayos X. Se comprobó por espectroscopia infrarroja la intensificación del carácter iónico del enlace metal-oxígeno al disminuir el número de átomos de carbono.
Recent developments in biomedicine fields for laser induced breakdown spectroscopy  [PDF]
Xian-Yun Liu, Wei-Jun Zhang
Journal of Biomedical Science and Engineering (JBiSE) , 2008, DOI: 10.4236/jbise.2008.13024
Abstract: Laser induced breakdown spectroscopy (LIBS) can be used to determine solid, liquid, colloi-dal, and biological samples. It is a promising technique for analysis and characterization of the composition of a broad variety of objects. This review describes in brief the basic prin-ciples and technological aspects of LIBS, and the most recent progress of the various ap-plications of this technique in biomedicine fields will be reviewed in detail, including bio-aerosols detection and identification, tis-sue analysis, mineral analysis in human body, and detection of zinc in human skin. Finally new approaches and the prospects in bio-medicine fields of LIBS technique are de-scribed.
Characterization and Flotation of Sulfur from Chalcopyrite Concentrate Leaching Residue  [PDF]
H. K. Lin
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2003, DOI: 10.4236/jmmce.2003.21001
Abstract: Elemental sulfur produced by chloride leaching of sulfide ores or concentrates contains selenium and tellurium usually too high to be used in various industrial or agricultural uses. The sulfur in the leaching residue can be upgraded to 90% in grade by froth flotation and the sulfur concentration can be followed by sulfur purification and selenium and tellurium removal. The sulfur in the leaching is in a form of discrete particles with a size range of 5 to 10 microns. The sulfur particles tend to agglomerate in the pulp and hence mechanically entrap gangue minerals. With sodium silicate as the dispersant as well as the depressant for siliceous material, a sulfur concentrate of 90% in grade and 90% in recovery can be obtained with a single-stage froth flotation. The flotation reagent consumptions are minimum. The majority of chalcopyrite remains in the sulfur flotation tailings and can be readily recovered by flotation with different flotation reagents. When amyl xanthate is used, 85% of chalcopyrite can be recovered with a copper grade of 14.5% in a single-stage froth flotation. The chalcopyrite flotation concentrate can be sent back to chloride leaching circuits.
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