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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Caracterización de polvos de fundición de cobre y establecimiento de rutas de procesado

Morales Soto, Alejandro 25 October 2006 (has links)
DOCTORAL:Se ha caracterizado tres muestras de fundiciones de cobre chilenas con diversas técnicas de caracterización, además se han analizado sus comportamientos ante la lixiviación con agua y con diferentes disoluciones lixiviantes ácidas y alcalinas. También se estudió la respuesta de estos polvos en operaciones de separación magnética y granulométrica y la inertización de las fracciones de material con mayor contenido de As.Se ha determinado que los polvos son materiales complejos muy solubles en agua y algo menos en ácido. Se propone dos rutas de procesado de estos materiales, las cuales contemplan etapas de lixiviación, cementación del cobre en las disoluciones y separación granulométrica para inertizar la fracción más fina; el material grueso recircula a la fundición y las disoluciones recirculan a la lixiviación de polvos frescos. / "Characterization of powders of copper foundry and establishment of routes of having processed"TEXT:It has been characterized three samples of Chilean copper foundries with diverse caracterization techniques. It has been analyzed their behaviors before the leaching with water and with different acid and alkaline solutions. The answer of these powders was also studied in operations of magnetic separation and granulometric separation and the inertization of the material fractions with more content of As.It has been determined that the powders are material complex very soluble in water and something less in acid. It intends two routes of having processed of these materials. Which contemplate leaching stages, cementation of the copper in the solutions and granulometric separation for the inertization the finest fraction. The thick material recycles to the foundry and the solutions recycle to the leaching of fresh powders.
2

Improved analytical methods for perfluoroalkyl acids (PFAAs) and their precursors – a focus on human dietary exposure

Ullah, Shahid January 2013 (has links)
Per- and polyfluoroalkyl substances are a large group of global environmental contaminants. They can be divided into two sub-groups, 1) perfluoroalkyl acids (PFAAs) and 2) so called precursors, i.e. compounds that can potentially be transformed to form PFAAs. PFAAs are today ubiquitous in wildlife and humans. Food and drinking water are assumed to be the dominant human exposure pathways for PFAAs. The main aim of this doctoral thesis was to develop highly sensitive and fully validated analytical methods for the determination of a range of PFAAs and selected precursors in dietary samples. The methods were based on liquid chromatography coupled to mass spectrometry. Samples were extracted by solvent extraction followed by a cleanup step employing solid phase extraction. The cleanup step could at the same time be used as a fractionation of ionic PFAAs and neutral precursors. Paper I and II describe the development of methods for simultaneous analysis of three groups of PFAAs including perfluoroalkyl phosphonic acids (PFPAs) in drinking water and food. Methyl piperidine was used as ion pairing agent, leading to highly sensitive analysis of PFPAs. A first screening of tap water samples and different food items revealed that human dietary exposure to PFPAs in Europe is currently not of concern. A novel method for simultaneous analysis of perfluoroalkyl carboxylic acids (PFCAs) and polyfluoroalkyl phosphate esters (PAPs) in food and packaging materials is described in paper III. Targeted food samples and their packaging were analyzed. The results showed that PAPs may contribute to human exposure to PFCAs. In paper IV temporal trends (1991-2011) of perfluorooctane sulfonic acid (PFOS) and its precursors in herring were investigated. Rapidly decreasing trends were found for precursors, whereas PFOS did not show a significant change over time. Precursors in fish may have played an important role for human exposure to PFOS in the 1990s but are probably negligible today. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p> / PERFOOD project (KBBE-227525)
3

Human Impact on Space Use, Activity Patterns, and Prey Abundance of Madagascar's Largest Natural Predator, Cryptoprocta ferox

Wyza, Eileen M. 20 September 2017 (has links)
No description available.

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