Taxation and tax evasion is an observable fact that occurs in all societies. In South Africa, tax evasion is one of the most sinister forms of crime and millions of rands are sidetracked by tax criminals. Studies from various countries indicate that it is not unusual for about half of the possible tax revenues to remain uncollected. Tax evasion is not something that is restricted to poor third world countries, it is a global phenomenon that has been there from the time tax was invented and will in all likelihood be with us until the end of time. Tax evasion is an intricate and overall hidden behaviour, but it has significant social and economic consequences. Taking this into consideration almost anything could influence the taxpayer’s decision to evade tax or not. The decision to comply with tax laws or to evade tax depends on various internal and external factors with regard to the taxpayer and this may differ from person to person. This study discusses the various factors influencing the taxpayer’s decision to comply with tax legislation, and whether these factors differ or correlate in developed and developing countries. Firstly, the factors influencing tax evasion in the United States of America and Switzerland were determined, after which the factors influencing tax evasion in South Africa and Brazil were determined. Secondly, the factors in the developed countries were compared to those in developing countries. Lastly these comparisons were analysed and they determined whether there were any major differences between the factors influencing tax evasion in developed and developing countries. AFRIKAANS : Belasting en belastingontduiking is ‘n waarneembare feit wat in alle samelewings voorkom. Belastingontduiking is een van die mees ernstige vorme van misdaad in Suid-Afrika en miljoene rande word deur belastingontduikers gesteel. Studies vanuit verskillende lande dui daarop dat dit nie ongewoon is dat omtrent die helfte van die moontlike belasting- inkomste nie ingevorder word nie. Belastingontduiking is nie beperk tot arm derdewêreldlande nie, dit is 'n wêreldwye verskynsel, en was daar van die tyd dat belasting uitgevind is en sal in alle waarskynlikheid met ons wees tot aan die einde van tyd. Belastingontduiking is 'n ingewikkelde en grootliks verborge gedrag, maar dit het belangrike sosiale en ekonomiese gevolge. Met dit ingedagte kan byna enigiets die belastingbetaler se besluit beïnvloed om belasting te ontduik of nie. Die besluit om aan belastingwetgewing te voldoen of om belasting te ontduik hang af van verskeie interne en eksterne faktore met betrekking tot die belastingbetaler en verskil waarskynlik van persoon tot persoon. Hierdie studie bespreek die verskillende faktore wat die belastingbetaler se besluit om aan belastingwetgewing te voldoen beïnvloed, en of hierdie faktore verskil of korreleer tussen ontwikkelde en ontwikkelende lande. Eerstens was die doel van die studie om die faktore wat belastingontduiking in die Verenigde State van Amerika en Switserland beïnvloed te bepaal, gevolg deur die bepaling van die faktore wat belastingontduiking in Suid-Afrika en Brasilië beïnvloed. Tweedens is die faktore in ontwikkelde lande met dié in ontwikkelende lande vergelyk. Laastens is hierdie vergelykings ontleed om te bepaal of daar groot verskille is tussen die faktore wat belastingontduiking beïnvloed in ontwikkelde lande in vergelyking met ontwikkelende lande. Copyright 2011, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Venter, JH 2011, Factors influencing tax evasion, MCom dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-03062012-153138 / > F12/4/149/gm / Dissertation (MCom)--University of Pretoria, 2012. / Taxation / unrestricted

No description available.

Neste trabalho, apresentamos estudos sobre o transporte eletrônico de cargas e diagramas de fase no plano ns-B em bicamadas eletrônicas ou poços quânticos duplos, formados de ligas semiconductoras de AlxGa1-xAs e GaAs, assim como também em poços quânticos triplos de GaAs. Para esta finalidade, amostras de poços duplos com diferentes concentrações de Al (x) dentro de cada poço e triplos de GaAs foram crescidas. Inicialmente, se apresenta um estudo teórico, o qual mostrou que, em poços quânticos duplos em que em cada poço a concetração de Al é diferente, a aplicação de tensões de porta permite a modulação do fator g de Landé dos elétrons confinados nesses poços. Em especial, estudou-se o caso de concentrações de Al que correspondem a valores do fator g com sinal oposto, em cada poço. Posteriormente se faz um estudo teórico da estrutura eletrônica das amostras de poços duplos e triplos, em seguida apresenta-se os fundamentos teóricos que serão de base para a interpretação de nosso resultados experimentais. Na primeira parte de nosso trabalho, medidas de magnetotransporte (Shubnikov-de Haas (SdH) e Hall), foram realizadas em todas as amostras de estudo. Na amostra de poço duplo 3242, com fator g de Landé de sinais opostos foi encontrado o colapso do gap de spin nas oscilações SdH com o incremento do campo magnético, ou seja, a soma da energia de Zeeman mais a energia de troca e correlação é igual ao potencial de desordem. Este colapso é atribuido à competição entre as energias de troca, intracamadas e intercamadas. Foi realizada uma análise das oscilações SdH através da transformada de Fourier (FFT), para mostrar que as propriedades eletrônicas tais como a concentração e mobilidade dos elétrons, nas amostras de poços duplos, decrescem à medida que aumenta a concentracão de Al. As propriedades eletrônicas nas amostras de poços triplos dependem dos parâmetros de crescimento, tal como a largura dos poços e barreira. Na segunda parte, são apresentados diagramas de fase ns-B, obtidos através da justaposição dos espectros de magnetorresistência, em amostras de poços duplos e triplos em campo magnético perpendicular e certos valores de campo inclinado. Mostra-se que, em campo magnético perpendicular, o modelo de uma partícula sem interações descreve com boa aproximação o aparecimento dos anéis no diagrama de fase para a amostra de poço duplo com g = -0,44. No entanto, na amostra com g ~ 0 o modelo não descreve em boa aproximação os diagramas de fase em campo magnético perpendicular e inclinado, precisando de um modelo que inclua termos de interação de muitos corpos para uma possível explicação. Também se prediz a existência de um estado canted antiferromagnético. O modelo também mostrará que os diagramas de fase das amostras de poços triplos têm um comportamento semelhante ao das amostras de poços duplos, quando a densidade de elétrons do poço central é baixa comparada com a densidade dos poços laterais. / In this work, we present studies about the electronic transport of charges and phase diagrams in the ns-B plane in electronic bilayers or double quantum wells formed of both AlxGa1-xAs and GaAs semiconductor alloys, also in GaAs triple quantum wells. For this purpose, double quantum wells with different aluminium compositions (Al(x)) in each well and triple quantum wells samples were growth. Firstly, a theoretical study was presented, which showed that in double quantum wells with different Al compositions, the aplication of gate voltages allow the modulation of the Landé g factor of the electrons confined within each well. In particular, the case where the quantum wells have different Al compositions was studied, which lead to the opposite signs of the electronic g-factor in each well. After this, a theoretical study of the electronic structure has been presented of both double and triple quantum wells, then, a basic theory has been presented, which will be the base for the interpretation of our experimental results. At the frst part of our work, magnetotransport measurements (Shubnikov-de Haas (SdH) and Hall) were performed in all the studied samples. In the double quantum well sample (3242), wich has Landé g-factor with opposite signs in each well, was found the spin gap collapse at the Shubnikov-de Haas oscillations with an increase in the magnetic field, that is, the sum of the bare Zeeman energy and exchange potencial energy has the same magnitude of the disorder potencial. This collapse was attributed to the competition between the interlayer and intralayer exchange energies. Fast Fourier transform (FFT) of the Shubnikov-de Haas oscillations was performed in the double and triple quantum well samples to show that the electronic properties, such as electron density and mobility decrease with the increase of the Al compositions. On the other hand, the electronic properties on the triple quantum well samples depend on growth parameters, such as width and heigh barriers of the wells. At the second part ns- B phase diagrams were determined through the superposed longitudinal magnetoresistance, in the double and triple quantum wells samples at the perpendicular magnetic field and certain values of tilted magnetic fields. It has been shown that in a perpendicular magnetic field a single particle model describes in a good aproximation the appearance of ring structures in the phase diagram of the double quantum well with g = -0:44. Meanwhile, at the sample with vanishing Landé g-factor (g ~ 0) the single particle model can not describe in a good approximation the phase diagram, being a requirement a many particle model for an possivel explanation. It has also been predicted the existence of a canted antiferromagnetic state. Finally, the model will also showed the phase diagram of triple quantum wells are similar to double quantum wells, when the electron density of the middle well is low compared to the side wells.

Neste trabalho, apresentamos estudos sobre o transporte eletrônico de cargas e diagramas de fase no plano ns-B em bicamadas eletrônicas ou poços quânticos duplos, formados de ligas semiconductoras de AlxGa1-xAs e GaAs, assim como também em poços quânticos triplos de GaAs. Para esta finalidade, amostras de poços duplos com diferentes concentrações de Al (x) dentro de cada poço e triplos de GaAs foram crescidas. Inicialmente, se apresenta um estudo teórico, o qual mostrou que, em poços quânticos duplos em que em cada poço a concetração de Al é diferente, a aplicação de tensões de porta permite a modulação do fator g de Landé dos elétrons confinados nesses poços. Em especial, estudou-se o caso de concentrações de Al que correspondem a valores do fator g com sinal oposto, em cada poço. Posteriormente se faz um estudo teórico da estrutura eletrônica das amostras de poços duplos e triplos, em seguida apresenta-se os fundamentos teóricos que serão de base para a interpretação de nosso resultados experimentais. Na primeira parte de nosso trabalho, medidas de magnetotransporte (Shubnikov-de Haas (SdH) e Hall), foram realizadas em todas as amostras de estudo. Na amostra de poço duplo 3242, com fator g de Landé de sinais opostos foi encontrado o colapso do gap de spin nas oscilações SdH com o incremento do campo magnético, ou seja, a soma da energia de Zeeman mais a energia de troca e correlação é igual ao potencial de desordem. Este colapso é atribuido à competição entre as energias de troca, intracamadas e intercamadas. Foi realizada uma análise das oscilações SdH através da transformada de Fourier (FFT), para mostrar que as propriedades eletrônicas tais como a concentração e mobilidade dos elétrons, nas amostras de poços duplos, decrescem à medida que aumenta a concentracão de Al. As propriedades eletrônicas nas amostras de poços triplos dependem dos parâmetros de crescimento, tal como a largura dos poços e barreira. Na segunda parte, são apresentados diagramas de fase ns-B, obtidos através da justaposição dos espectros de magnetorresistência, em amostras de poços duplos e triplos em campo magnético perpendicular e certos valores de campo inclinado. Mostra-se que, em campo magnético perpendicular, o modelo de uma partícula sem interações descreve com boa aproximação o aparecimento dos anéis no diagrama de fase para a amostra de poço duplo com g = -0,44. No entanto, na amostra com g ~ 0 o modelo não descreve em boa aproximação os diagramas de fase em campo magnético perpendicular e inclinado, precisando de um modelo que inclua termos de interação de muitos corpos para uma possível explicação. Também se prediz a existência de um estado canted antiferromagnético. O modelo também mostrará que os diagramas de fase das amostras de poços triplos têm um comportamento semelhante ao das amostras de poços duplos, quando a densidade de elétrons do poço central é baixa comparada com a densidade dos poços laterais. / In this work, we present studies about the electronic transport of charges and phase diagrams in the ns-B plane in electronic bilayers or double quantum wells formed of both AlxGa1-xAs and GaAs semiconductor alloys, also in GaAs triple quantum wells. For this purpose, double quantum wells with different aluminium compositions (Al(x)) in each well and triple quantum wells samples were growth. Firstly, a theoretical study was presented, which showed that in double quantum wells with different Al compositions, the aplication of gate voltages allow the modulation of the Landé g factor of the electrons confined within each well. In particular, the case where the quantum wells have different Al compositions was studied, which lead to the opposite signs of the electronic g-factor in each well. After this, a theoretical study of the electronic structure has been presented of both double and triple quantum wells, then, a basic theory has been presented, which will be the base for the interpretation of our experimental results. At the frst part of our work, magnetotransport measurements (Shubnikov-de Haas (SdH) and Hall) were performed in all the studied samples. In the double quantum well sample (3242), wich has Landé g-factor with opposite signs in each well, was found the spin gap collapse at the Shubnikov-de Haas oscillations with an increase in the magnetic field, that is, the sum of the bare Zeeman energy and exchange potencial energy has the same magnitude of the disorder potencial. This collapse was attributed to the competition between the interlayer and intralayer exchange energies. Fast Fourier transform (FFT) of the Shubnikov-de Haas oscillations was performed in the double and triple quantum well samples to show that the electronic properties, such as electron density and mobility decrease with the increase of the Al compositions. On the other hand, the electronic properties on the triple quantum well samples depend on growth parameters, such as width and heigh barriers of the wells. At the second part ns- B phase diagrams were determined through the superposed longitudinal magnetoresistance, in the double and triple quantum wells samples at the perpendicular magnetic field and certain values of tilted magnetic fields. It has been shown that in a perpendicular magnetic field a single particle model describes in a good aproximation the appearance of ring structures in the phase diagram of the double quantum well with g = -0:44. Meanwhile, at the sample with vanishing Landé g-factor (g ~ 0) the single particle model can not describe in a good approximation the phase diagram, being a requirement a many particle model for an possivel explanation. It has also been predicted the existence of a canted antiferromagnetic state. Finally, the model will also showed the phase diagram of triple quantum wells are similar to double quantum wells, when the electron density of the middle well is low compared to the side wells.

Background: In South Africa, as in many other developing countries, iron deficiency (the most common micronutrient deficiency) still remains unresolved; while obesity has emerged as a public health challenge causing increases in the incidence and prevalence of cardiovascular diseases (CVDs). Research has shown that certain iron indices are associated with both anthropometric and biological markers of CVDs. Adiposity is thought to modulate the pathway linking iron status to CVDs. Objective: To examine the associations between iron indices, anthropometric and biological markers of CVDs in an African population undergoing transition. Methods: This thesis was based on secondary analysis of data generated during the Transition and Health during Urbanisation of South Africans (THUSA) study; and primary and secondary analysis of the baseline Prospective Urban and Rural Epidemiological (PURE) study. Both studies were cross–sectional in design and were conducted between 1996–1998 and in 2005 respectively in the North West Province of South Africa. The 1854 men and women participants in the THUSA study (>15years) and 1262 women participants in the PURE study (>35years) were included in the analysis. The relationship between iron and anthropometric indicators of CVD risk was examined in the THUSA study while that of iron status, anthropometric and biological markers of CVD risk was examined in the PURE study. Results: In the THUSA study, ferritin was positively associated with body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR), body fat and subscapular skinfold (r=0.141, 0.359, 0.396, 0.308, 0.141 respectively for men and 0.126, 0.232, 0.319, 0.126, 0.105 respectively for women; p<0.01). Only the women showed decreased serum iron concentration with increasing BMI (p<0.05). WC and WHR increased with increasing serum ferritin concentration for both genders (p<0.05). As for the PURE study, associations between iron status parameters and CVD risk factors were generally weak (r<0.3, p<0.01) and were not retained after adjusting for valid confounders. WC and WHR increased with increasing ferritin concentration (p<0.05). Conclusion: Although these results do not indicate any significant association between iron indices and biological markers of CVD, its association with anthropometric indices gives an indication of the possible contribution of iron in the aetiology of CVDs. Thus, it may be necessary to exercise caution on the emphasis placed on iron as a nutrient and iron intervention programmes because of the suggestive role of iron in CVD development. / Thesis (Ph.D. (Nutrition))--North-West University, Potchefstroom Campus, 2011.

Background: In South Africa, as in many other developing countries, iron deficiency (the most common micronutrient deficiency) still remains unresolved; while obesity has emerged as a public health challenge causing increases in the incidence and prevalence of cardiovascular diseases (CVDs). Research has shown that certain iron indices are associated with both anthropometric and biological markers of CVDs. Adiposity is thought to modulate the pathway linking iron status to CVDs. Objective: To examine the associations between iron indices, anthropometric and biological markers of CVDs in an African population undergoing transition. Methods: This thesis was based on secondary analysis of data generated during the Transition and Health during Urbanisation of South Africans (THUSA) study; and primary and secondary analysis of the baseline Prospective Urban and Rural Epidemiological (PURE) study. Both studies were cross–sectional in design and were conducted between 1996–1998 and in 2005 respectively in the North West Province of South Africa. The 1854 men and women participants in the THUSA study (>15years) and 1262 women participants in the PURE study (>35years) were included in the analysis. The relationship between iron and anthropometric indicators of CVD risk was examined in the THUSA study while that of iron status, anthropometric and biological markers of CVD risk was examined in the PURE study. Results: In the THUSA study, ferritin was positively associated with body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR), body fat and subscapular skinfold (r=0.141, 0.359, 0.396, 0.308, 0.141 respectively for men and 0.126, 0.232, 0.319, 0.126, 0.105 respectively for women; p<0.01). Only the women showed decreased serum iron concentration with increasing BMI (p<0.05). WC and WHR increased with increasing serum ferritin concentration for both genders (p<0.05). As for the PURE study, associations between iron status parameters and CVD risk factors were generally weak (r<0.3, p<0.01) and were not retained after adjusting for valid confounders. WC and WHR increased with increasing ferritin concentration (p<0.05). Conclusion: Although these results do not indicate any significant association between iron indices and biological markers of CVD, its association with anthropometric indices gives an indication of the possible contribution of iron in the aetiology of CVDs. Thus, it may be necessary to exercise caution on the emphasis placed on iron as a nutrient and iron intervention programmes because of the suggestive role of iron in CVD development. / Thesis (Ph.D. (Nutrition))--North-West University, Potchefstroom Campus, 2011.

L’objectif de la thèse est d'évaluer l’apport des données satellites dans le suivi saisonnier de la végétation forestière (sous-bois et strate arborée). L'étude a été conduite sur la forêt landaise. Elle est basée sur une série de sept ans d'observations satellitaires décadaires d’un indice de végétation (PVI) et de mesures in situ de la surface foliaire (LAI) du sous-bois et des arbres. Tout d’abord, les observations in-situ ont été analysées. Elles montrent que le sous-bois est le déterminant majeur de la trajectoire saisonnière du LAI de l’ensemble du couvert végétal. Puis, ces informations ont été comparées aux données satellitaires. Il apparaît que la phénologie printanière du PVI renseigne sur celle du LAI du sous-bois. Enfin, ces résultats été exploités à l’échelle régionale et une carte régionale des types de landes a pu être produite. Cette étude ouvre des perspectives en matière d'intégration et de spatialisation des bilans d'eau et de carbone des écosystèmes forestiers à l'échelle régionale. / The aim of this thesis is to assess the potential of the remote sensing data to monitor the seasonal dynamic of the forest vegetation (understory and tree canopy). The study has been carried out on the maritime pine forest in the Southwest of France. It is based on a 7-year time-series of the 10-day vegetation index PVI composite derived from satellite and on in situ leaf area measurements (LAI) of understory and tree story.At first, the in situ observations have been analysed. It shows that the understory vegetation is the main driver of the seasonal dynamic of the whole forest LAI (understory+tree story). Then, these informations have been compared with the time-series of remote sensed PVI . It appears that the spring phenology of the PVI informs directly about the LAI understory one.Finally, these results have been used at the regional scale and a regional map of the lande types has been produced. This study opens some new prospects about integration and spatialisation of water and carbon balance of forest ecosystems at regional scale.