Orientador: Ana Paula Girol / Resumo: A poluição do ar e o uso de cigarro são as principais fontes de inalação e exposição a agentes carcinógenos, como os hidrocarbonetos aromáticos policíclicos (HAP) resultantes da combustão incompleta de matéria orgânica e distribuídos amplamente no ambiente. O benzopireno é um dos principais HAP presentes no ambiente e com alta capacidade carcinogênica, sendo, portanto, usado em modelos experimentais in vivo. Investigações têm mostrado que os fármacos anti-inflamatórios podem reduzir a incidência de câncer de pulmão. Os compostos bioativos naturais (CBN) como os terpenos e flavonoides apresentam muitas propriedades, entre elas, redução da inflamação, estimulação do sistema imune e modulação de enzimas detoxificantes. Entre os CBNs destacamos a piperlongumina (PL), um alcaloide da Piper longum, que pode representar uma possibilidade de tratamento para o câncer de pulmão. Para o desenvolvimento do trabalho foram usados camundongos Balb/c divididos em 3 grupos (n=10/grupo): controle (sham), induzido por benzopireno (100 mg/kg, diluído em DMSO e administrado intraperitonealmente, i.p.) não tratado (BaP) e induzido por benzopireno e tratado com PL (2 mg/kg em DMSO a 10%, i.p.) a partir da oitava semana pós-indução (BaP/PL). Os animais foram pesados diariamente. A pletsmografia para verificação de volume, frequência e ventilação pulmonares foi realizada na última semana do protocolo (12ª semana). Após, os animais foram eutanasiados para coleta de sangue, lavado broncoalveolar e frag... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

abstract: Extended crystal defects often play a critical role in determining semiconductor device performance. This dissertation describes the application of transmission electron microscopy (TEM) and aberration-corrected scanning TEM (AC-STEM) to study defect clusters and the atomic-scale structure of defects in compound semiconductors. An extensive effort was made to identify specific locations of crystal defects in epitaxial CdTe that might contribute to degraded light-conversion efficiency. Electroluminescence (EL) mapping and the creation of surface etch pits through chemical treatment were combined in attempts to identify specific structural defects for subsequent TEM examination. Observations of these specimens revealed only surface etch pits, without any visible indication of extended defects near their base. While chemical etch pits could be helpful for precisely locating extended defects that intersect with the treated surface, this study concluded that surface roughness surrounding etch pits would likely mitigate against their usefulness. Defect locations in GaAs solar-cell devices were identified using combinations of EL, photoluminescence, and Raman scattering, and then studied more closely using TEM. Observations showed that device degradation was invariably associated with a cluster of extended defects, rather than a single defect, as previously assumed. AC-STEM observations revealed that individual defects within each cluster consisted primarily of intrinsic stacking faults terminated by 30° and 90° partial dislocations, although other defect structures were also identified. Lomer dislocations were identified near locations where two lines of strain contrast intersected in a large cluster, and a comparatively shallow cluster, largely constrained to the GaAs emitter layer, contained 60° perfect dislocations associated with localized strain contrast. In another study, misfit dislocations at II-VI/III-V heterovalent interfaces were investigated and characterized using AC-STEM. Misfit strain at ZnTe/GaAs interfaces, which have relatively high lattice mismatch (7.38%), was relieved primarily through Lomer dislocations, while ZnTe/InP interfaces, with only 3.85% lattice mismatch, were relaxed by a mixture of 60° perfect dislocations, 30° partial dislocations, and Lomer dislocations. These results were consistent with the previous findings that misfit strain was relaxed primarily through 60° perfect dislocations that had either dissociated into partial dislocations or interacted to form Lomer dislocations as the amount of misfit strain increased. / Dissertation/Thesis / Doctoral Dissertation Physics 2020

In the pursuit of lower cost intumescent flame retardant (IFR) systems, the compound expandable graphite (EG) was identified. This compound delivers high flame retardant performance but provides non-uniform thermal shielding when exposed to open flame from below due to negative gravitational effects. It was theorised that this may be remedied either through ion exchange of the interstratified ions with low glass transition ions or through use in binary systems with other compounds. Two classes of commercial EG were identified, namely a low and a high expansion onset temperature EG compound. Extensive characterisation of each EG compound was undertaken to assess its composition, expansion mechanisms and onset temperatures in order to identify compatible compounds for binary use. The susceptibility of each compound to ion exchange was also assessed. An industrial IFR ethylenediamine phosphate (EDAP) and a novel flame retardant were synthesised for assessment in binary use with EG. Coupled with the above study, this project developed two novel fire testing techniques as low cost alternatives to well-established fire testing methods such as cone calorimetry. The first technique involved an open flame fire testing method which allowed vertical or horizontal testing. Digital and infrared (IR) video recording during operation facilitated comparison of multiple performance indicators further strengthening this method. The second technique allowed assessment of the mass loss resistance of each compound during laser pyrolysis. Characterisation of the EG compounds allowed development of structural models to describe each compound and explain the mechanisms of their expansion and gaseous release. Exhaustive ion exchange testing did not deliver favourable results, necessitating the pursuit of compounds for binary use with EG. A novel IFR was synthesised by neutralising 3,5-diaminobenzoic acid hydrochloride salt with ammonium dihydrogen phosphate. This compound, which melts at 257 °C, decomposes concurrently to release carbon dioxide gas which promotes intumescent charring. The flame retardant performance of this compound and EDAP as primary flame retardants and in combination with expandable graphite was evaluated. As a proof of concept, the novel compound was tested as a primary flame retardant using cone calorimetry after which its utility in binary systems with low temperature expandable graphite was tested. Substantial decreases in peak heat release rate (pHRR) and flame out time were achieved for all binary systems. This success led to testing of a number of combinations of low and high expansion onset EG and the other IFRs to identify the highest performing combination, which proved to be the 10-10 EDAP-EG system. Combinations of EG and the novel compound also showed excellent results. The novel fire testing techniques proved effective in identifying high performance combinations and showed comparable trends to those measured in cone calorimetry, at a greatly reduced cost and material requirement. IR analysis of open flame fire testing indicated increases in the temperatures required for ignition and burn through of the substrate. Observations, corroborated by optical video, showed that cohesive and uniform thermal shielding was achieved in all binary systems tested. This study illustrates that systems of 10% EG combined with either 10% DABAP or 10% EDAP are both the most economical binary systems tested but are extremely high performance systems as well. Both of these systems delivered excellent results while being more economic than the widely used industrial system with a 25-30% EDAP loading. It is recommended that these compounds be considered for industrial use. Furthermore, the effective fire testing techniques developed in this study may be utilised in future fire testing to identify high performance compounds at a lower cost prior to further assessment through methods such as cone calorimetry. / Thesis (PhD)--University of Pretoria, 2017. / Chemical Engineering / PhD / Unrestricted

Warren Buffet started an investment partnership of $100 in 1956 and has gone on to accumulate a personal net worth of over $60 billion. He started primarily as a value investor, and gradually changed over time to a strategy which uses the PEG ratio as its main tool. Peter Lynch, one of the most successful fund managers in history and had a compound annual growth rate of 29% for 13 years, was the man to first introduce the world to the PEG ratio. With such prominence, however, widespread use of previously successful strategies tend to render them ineffective due to everyone using them, and today the PEG ratio’s effectiveness as a valuation tool remains a topical debate between market commentators.This study sets out to determine if the PEG ratio adds value using JSE Main Board data from 2002 to 2012. Returns from five portfolios constructed directly from share quintiles based on PEG ratio magnitude are compared to returns of a portfolio constructed from the optimum quintile of value shares. The PEG ratio portfolio returns are examined based on 3 rebalancing period strategies, and on relative performance between the quintiles within each strategy.It is found that a 24 monthly rebalancing strategy provides superior returns to that of 3 or 12 monthly rebalancing for PEG quintiles of selected stocks. Furthermore, the lowest PEG ratio quintile in this strategy outperforms the value portfolio by a compound annual growth rate of 4.3%. The second lowest PEG ratio quintile portfolio performs slightly better to ensure that 40% of stocks selected based on the PEG ratio produced sustained superior returns to the optimum quintile value portfolio. / Dissertation (MBA)--University of Pretoria, 2012. / Gordon Institute of Business Science (GIBS) / unrestricted

Tato práce je zaměřená na studium magnetických vlastností tří r·zných sloučenin na bázi uranu obsahujících 5f elektrony (U4Ru7Ge6, UAu2Si2 a UIrGe). V rámci této práce byly, za pomoci r·zných metod, připraveny vysoce kvalitní krystaly těchto sloučenin. Vlastnosti těchto systém· byly studovány r·znými objemovými meto- dami (magnetizace, měrné teplo, teplotní roztažnost, elektrický transport) a také neu- tronovým a rentgenovým rozptylem při širokém spektru vnějších podmínek (nízká teplota, vysoké magnetické pole, vysoký tlak). Kombinace těchto metod odhalila komplexní chování těchto systém· a pomohla sestrojit jejich magnetické fázové diagramy. První studovanou sloučeninou je feromagnet U4Ru7Ge6vykazující velmi nízkou mag- netokrystalovou anizotropii, která je neočekávaná pro sloučeninu na bázi uranu. To se promítá do izotropní závislosti téměř všech měřených fyzikálních vlastností. Bylo zjištěno, že osa snadné magnetizace se mění v uspořádaném stavu a tento jev je spojen s anomáliemi v teplotní roztažnosti ukazující na možnou rhomboedrickou distorzi. Ta vede k vytvoření dvou odlišných pozic uranu s odlišným magnetickým momentem. Tato před- pově¤ byla potvrzena teoretickými výpočty a pomocí polarizované neutronové difrakce. Rozdíl magnetických moment· na dvou odlišných uranových pozicích je zp·soben...

The protection of privacy related information of the individual is receiving increasing attention. Particular focus is on the protection of user interaction with other users or service providers. Protection of this interaction centres on anonymising the user’s actions, or protecting “what we do”. An equally important aspect is protecting the information related to a user that is stored in some electronic way (or protecting “who we are”). This may be profile information on a social networking site, or personal information in a bank’s database. A typical approach to protecting the user (data owner) in this case is to tag their data with the “purpose” the collecting entity (data controller) has for the data. These purposes are in most cases singular in nature (there is “one” purpose – no combinations of purposes – of the data), and provide little in the way of flexibility when specifying a privacy policy. Moreover, in all cases the user accessing the data (data user) does little to state their intent with the data. New types of purposes called compound purposes, which are combinations of singular or other compound purposes, are proposed and examined in this text. In addition to presenting the notion of compound purposes, compound reasons are also presented. Compound reasons represent the intent of the entity using the data (the data user) with the data. Also considered are the benefits of having the data user specifying their intent with data explicitly, the verification of compound reasons (the data user’s statement of intent) against compound purposes, the integration of compound statements in existing technologies such as SQL by providing a model for using compound purposes and reasons in a relational database management system for protecting privacy, and the use of compounds (purposes and reasons) as a method for managing privacy agreements. / Thesis (PhD)--University of Pretoria, 2011. / Computer Science / unrestricted

This corpus-based study investigates the most frequent occurring prepositional verbs collocated with the Japanese syntactic compound verb -kiru and aims to establish how the prepositional verb affects the semantic meaning of the verb-kiru construct. The study uses sketchengine’s online database, “Japanese Web2011”, which contains around 8 billion Japanese terms collected from the internet from various online sources from 2011 and onwards. From my results I was able to establish the most frequent occurring prepositional verbs in a -kiru construct from the database, and through a concordance analysis I was able to identify three semantic meanings incurred by the syntactic compound verb -kiru: the semantic meaning of completion, the dual semantic meaning of completion and extremity and the semantic meaning of extremity. Further analysis showed that the semantic meaning of extremity exists in the deep structure of the sentence and when transformed to the surface structure the semantic meaning shifts to that of completion.

No description available.

More efficient and cheaper solar cells are necessary if photovoltaics are to play a major rolein the field of sustainable power generation. Copper indium gallium selenide (CIGSe) is one of the best suited materials for thin film solar cell absorbers. One production method for thin film manufacturing is sputtering, a fast, high-yield, all-dry process that can be performed in an unbroken vacuum chain. The sputter target, which provides the raw material for this process, is an important link to obtain high quality films. Furthermore, the targets stands for the single largest cost in solar cells produced through the method. Hence, driving down the target production costs while maintaining or increasing quality is a vital route towards competitive photovoltaic power generation. In this project, compound CIGSe sputter target material was produced via mechanical alloying of elemental raw materials, followed by hot pressing. The resulting material obtained a relative density above 90% in all samples, with close compositional matching and grain sizes between 20-50 µm. Electrical characterization indicated predominantly p-type majority carriers, and the resistivity was within the range of industrially produced targets. Suitable process parameters are suggested as follows: for ball milling; 600rpm rotational speed, a ball-to-powder ratio of 5:1, and a milling time of 60-120 min. For pressing: 650-750˚C peak temperature, maintained for 1-2 h under 25-60 MPa pressure. 30 min dwell time at peak temperature before pressure application was found to reduce porosity. An initial composition of 23.2/20/6.5/50 at% of Cu, In, Ga, and Se, respectively, was found appropriate to obtain a final composition close to 22.8/20/7/50.2 at%. The project has proven that mechanical alloying combined with hot pressing provides a promising route towards efficient sputter target manufacturing, where the reduction of process operations compared to conventional manufacturing methods entails an optimistic economic outlook.

<p>The lack of a thorough understanding of the solidification behaviors of the proeutectic Al₃Sc and the Al-Al₃Sc eutectic in a hypereutectic Al-Sc alloy stimulates the present dissertation. The major findings for the single-phase growth of the proeutectic Al₃Sc is summarized as follows: At a low cooling rate (~1 ºC·s^-1), the proeutectic Al₃Sc phase’s formation was governed by the lateral growth, exposing six flat {100} facets. At an intermediate cooling rate (~400 ºC·s^-1), the proeutectic Al₃Sc grew in a dendritic manner, with well-defined backbones extending in eight <111> directions and paraboloidal dendrite tips, although the dendrite tips and side-branches turned into faceted steps at a late growth stage,when the lateral growth prevailed. At a high cooling rate (~1000 ºC·s^-1), the proeutectic Al₃Sc primarily crystallized into an entirely seaweed-structured particle, which was composed of interior compact seaweeds and exterior fractal seaweeds. In order to verify the proposed dendritic and seaweed growth mechanisms for the proeutectic Al₃Sc, various morphological stability criteria were used, and fair agreement between the observed and the estimated characteristic length scales was reached.</p><p>On the Al-Al₃Sc eutectic side, it was found that a rod-typed Al₃Sc eutectic phase prevalently existed in an as-cast hypereutectic Al-Sc alloy that solidified via both slow cooling in air (~1 ºC·s⁻¹) and rapid cooling in a wedge-shaped copper mold (up to ~3000 ºC·s⁻¹). Al-Al₃Sc eutectic dendrites were identified within a narrow region near the edge of the wedge. The eutectic dendrites had an equiaxed dendritic contour and a rod eutectic structure inside. Quantitative assessments revealed that an interface undercooling of 48.2 ºC was required to form the eutectic dendrites, or in other words, to enter the coupled zone of the Al-Al₃Sc phase diagram. Furthermore, a phenomenon of scientific interest was discussed: When crystallizing under a near-equilibrium condition, the eutectic Al₃Sc phase formed a non-faceted morphology, in contradiction to its faceted nature. Based on the competitive growth criterion, it was deduced that the non-faceting of the eutectic Al₃Sc phase essentially reduced the interface undercooling for the resultant regular eutectic, in comparison to an otherwise irregular eutectic that would contain a faceted eutectic Al₃Sc phase.</p>