Investment in Human Capital in a Macrodynamic Framework: Redistributive Taxation, Public Debt and Welfare

Efficient investment in human capital is a subject of great concern among economists. By means of an overlapping-generations macrodynamic model with credit constraints, imperfect insurance and exogenous labor supply, we appraise inefficiencies related to misinvestment in human capital and propose a simple scheme of redistributive taxation to mitigate them. A numerical simulation is calibrated in order to match stylized facts of Brazilian economy and shows that, in steady-state, with a flat-tax mechanism and lump-sum transfers, government intervention is beneficial to the extent it maximizes our utilitarian measure of welfare and reduces both inefficiency associated with misdirected investment in human capital and standard inequality indexes. After considering the possibility of decomposing our utilitarian measure of welfare and of allowing for public debt, we show that reduced inequality is the driving force which accounts for welfare improvement and that public debt plays no role. Robustness analysis shows that endogenizing labor supply does not lead to substantial changes in previous resultsinvestment in human capital; idiosyncratic risk; efficiency; overaccumulation of capital; redistributive taxation; public debt; welfare measures; social insurance

A WELFARE ANALYSIS OF ECONOMIC FLUCTUATIONS IN SOUTH AMERICA

How large are welfare costs associated with economic aggregate fluctuations is a topic of great concern among economists at least since Robert Lucas' well-known and thought-provoking exercise in the late 1980s. Our analysis assesses the magnitude of such costs for nine countries in South America by means of three alternative trend-cycle decomposition methods. The results suggest South American countries have welfare costs of economic fluctuations notably higher than the U. S. economy.

Spin g-factor due to electronic interactions in graphene

The gyromagnetic factor is an important physical quantity relating the magnetic-dipole moment of a particle to its spin. The electron spin g-factor in vacuo is one of the best model-based theoretical predictions ever made, showing agreement with the measured value up to ten parts per trillion. However, for electrons in a material the g-factor is modified with respect to its value in vacuo because of environment interactions. Here, we show how interaction effects lead to the spin g-factor correction in graphene by considering the full electromagnetic interaction in the framework of pseudo-QED. We compare our theoretical prediction with experiments performed on graphene deposited on SiO2 and SiC, and we find a very good agreement between them.Comment: Improved version of the manuscript; valley g-factor part has been remove

Ecoacoustic Methods for Multi-Taxa Animal Surveys in the Amazon

Tropical regions host most of the biodiversity found on Earth, but these species-rich areas are constantly threatened by human development and other disturbances that put this diversity of life forms at risk. To avoid extirpations of animal and plant species, scientists and managers rely on accurate monitoring techniques to retrieve information about population trends. This task is not easy, especially in the tropics, where there is often a lack of personnel to conduct surveys, a lack of funding, and the areas are so extensive that many countries need to be involved in monitoring (e.g., Amazon biome). For this reason, scientists are trying to take advantage of technological advancements to develop more cost-effective alternatives for multi-taxa surveys. While satellite imagery provides a richness of information about vegetation, it fails to provide direct measurement of the fauna. In this dissertation conducted in the Brazilian Amazon, I used passive acoustic recorders as a technique to collect reliable and verifiable information about the fauna. I show that the data collected with passive acoustic sensors is able to provide information about how the biodiversity of the Amazon changes with human disturbances, time of the day, and in different environments

Unitarity of theories containing fractional powers of the d'Alembertian operator

We examine the unitarity of a class of generalized Maxwell U(1) gauge theories in (2+1) D containing the pseudodifferential operator $\Box^{1-\alpha}$, for $\alpha \in [0,1)$. We show that only Quantum Electrodynamics (QED$_3$) and its generalization known as Pseudo Quantum Electrodynamics (PQED), for which $\alpha =0$ and $\alpha = 1/2$, respectively, satisfy unitarity. The latter plays an important role in the description of the electromagnetic interactions of charged particles confined to a plane, such as in graphene or in hetero-junctions displaying the quantum Hall effect.Comment: 6 pages, no figure

Interaction Induced Quantum Valley Hall Effect in Graphene

We use Pseudo Quantum Electrodynamics (PQED) in order to describe the full electromagnetic interaction of the p-electrons of graphene in a consistent 2D formulation. We first consider the effect of this interaction in the vacuum polarization tensor or, equivalently, in the current correlator. This allows us to obtain the dc conductivity after a smooth zero-frequency limit is taken in Kubo's formula.Thereby, we obtain the usual expression for the minimal conductivity plus corrections due to the interaction that bring it closer to the experimental value. We then predict the onset of an interaction-driven spontaneous Quantum Valley Hall effect (QVHE) below a critical temperature of the order of $0.05$ K. The transverse (Hall) valley conductivity is evaluated exactly and shown to coincide with the one in the usual Quantum Hall effect. Finally, by considering the effects of PQED, we show that the electron self-energy is such that a set of P- and T- symmetric gapped electron energy eigenstates are dynamically generated, in association with the QVHE.Comment: 5 pages + supplemental materia

A Class of Incomplete and Ambiguity Averse Preferences

This paper characterizes ambiguity averse preferences in the absence of the completeness axiom. We axiomatize multiple selves versions of some of the most important examples of complete and ambiguity averse preferences, and characterize when those incomplete preferences are ambiguity averse.

Investment in Human Capital in a Macrodynamic Framework: Redistributive Taxation, Public Debt and Welfare

Efficient investment in human capital is a subject of great concern among economists. By means of an overlapping-generations macrodynamic model with credit constraints, imperfect insurance and exogenous labor supply, we appraise inefficiencies related to misinvestment in human capital and propose a simple scheme of redistributive taxation to mitigate them. A numerical simulation is calibrated in order to match stylized facts of the quite unequal Brazilian economy and shows that, in steady-state, with a flat-tax mechanism and lump-sum transfers, government intervention is beneficial to the extent it maximizes our utilitarian measure of welfare and reduces both inefficiency associated with misdirected investment in human capital and standard inequality indexes. After considering the possibility of decomposing our utilitarian measure of welfare and of allowing for public debt, we show that reduced inequality is the driving force which accounts for welfare improvement and that public debt plays no role. Robustness analysis shows that endogenizing labor supply does not lead to substantial changes in previous resultsinvestment in human capital; idiosyncratic risk; efficiency; overaccumulation of capital; redistributive taxation; public debt; welfare measures; social insurance.

Juxta-apical radiolucency : evaluation using panoramic radiography and cone beam computed tomography images

Orientadores: Deborah Queiroz de Freitas França, Anne Caroline Costa OenningDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: A radiolucência justa-apical (RJA) representa uma variação do aspecto normal do osso trabecular na região de terceiros molares inferiores, cuja identificação em exames de imagem tem sido apontada como preditora de injúrias nervosas. Os objetivos no presente estudo foram: determinar a prevalência da radiolucência justa-apical, investigar sua associação com o terceiro molar inferior, descrever suas principais características imaginológicas e avaliar sua relação com o canal mandibular e as corticais ósseas. Para os três primeiros objetivos, foram utilizadas radiografias panorâmicas e, para o último, exames de tomografia computadorizada de feixe cônico (TCFC). Hum mil e cinquenta radiografias panorâmicas (1830 terceiros molares) foram analisadas quanto a presença da RJA. Um grupo RJA e um grupo controle foram formados e classificados de acordo com o posicionamento, profundidade de impactação e desenvolvimento radicular dos terceiros molares. Adicionalmente, a presença de sinais radiográficos de proximidade entre o terceiro molar e o canal mandibular e as principais características imaginológicas da RJA, como corticalização, presença de cortical alveolar e relação espacial com o canal mandibular, foram registradas. Para a análise estatística, os testes de qui-quadrado e regressão logística múltipla foram realizados. A RJA foi identificada em 116 (11%) pacientes e 130 (7,1%) terceiros molares, e sua presença foi significativamente associada ao sexo feminino (p=0,0061) e à 2ª e 3ª décadas de vida (p<0,0001). A presença da RJA demonstrou associação significativa com dentes em posição vertical (p=0.0003) e com formação radicular completa (p=0.0011). Não foi observada associação entre a profundidade de impactação dentária e a presença ou ausência da RJA (p=0,1849). Os sinais radiográficos de proximidade estiveram ausentes em 66,2% dos casos de RJA (p=0,0233). Quanto às suas características radiográficas, houve presença de cortical alveolar na região da RJA e ela esteve corticalizada e radiograficamente sobreposta ao canal mandibular na maioria dos casos. Para a análise das imagens de TCFC, 47 casos de RJA foram avaliados de acordo com sua posição em relação ao terceiro molar e classificados segundo sua relação anatômica com o canal mandibular e com as corticais ósseas da mandíbula. A posição do canal mandibular na região dos terceiros molares também foi registrada e comparada com um grupo controle. Análises descritivas e testes de qui-quadrado foram realizados. Houve uma associação significativa entre a presença da RJA e a posição do canal mandibular (p=0,0193), que esteve por lingual em 59,6% dos casos. Na maioria dos casos, a RJA estava localizada por distal em relação ao dente (66%) e em contato com o canal mandibular, sendo em 53,2% com cortical entre as estruturas e 40,4% sem a detecção da mesma. Em 22 (46,82%) casos, a RJA causou afinamento das corticais ósseas, não sendo encontradas diferenças estatisticamente significativas entre as corticais vestibular e lingual (p=0,5728). Foi possível concluir que a RJA não representa um achado radiográfico raro. A descrição de suas principais características imaginológicas e da sua relação com o canal mandibular são importantes para alertar os profissionais e contribuir para o seu correto diagnósticoAbstract: Justa-apical radiolucency (JAR) represents a variation of the normal aspect of the trabecular bone in the region of mandibular third molars whose identification on imaging exams has been appointed as a predictor of nerve injuries. The aims of this study were: to determine the prevalence of the juxta-apical radiolucency, to investigate its association with third molars status, to describe its main radiologic features and to assess its relationship with mandibular canal and with cortical plates. Panoramic radiographs were used for the first three objectives, and cone beam computed tomography (CBCT) were used for the latter. One thousand and fifty panoramic images (1830 third molars) were evaluated for the presence of JAR. A JAR group and a control group were classified according to positioning, depth of impaction and root development of the third molar. In addition, the presence of radiographic signs of proximity between the mandibular canal and the third molar and the main imaging features of the JAR, as corticalization, presence or absence of lamina dura and radiographic relationship with the mandibular canal were recorded. Chi-square test and multiple logistic regression were performed for data analysis. The JAR was visualized in 116 (11%) patients and in 130 (7.1%) mandibular third molars, and its presence was significantly associated with female (p=0.0061) and with the 2nd and 3rd decade of life (p<0.0001). The presence of JAR demonstrated a significant association with teeth in vertical position (p=0.0003) and with complete root formation (p=0.0011). No association was observed between depth of impaction and presence or absence of the JAR (p=0.1849). The proximity radiographic signs were absent in 66.2% of cases JAR (p=0.0233). Regarding its image features, there was dental lamina dura in the JAR area and it was corticalized and overlapped to the mandibular canal in most cases. For the CBCT analyses, 47 cases of JAR were assessed according to its position relative to the third molar and classified according to its relationship with the mandibular canal and the cortical plates of the mandible. The position of the mandibular canal in the third molar region was also recorded and compared with a control group. Descriptive statistics and chi-square tests were performed. There was a statistically significant association between the presence of JAR and the position of the mandibular canal (p=0.0193), which was positioned lingually in 59.6% of JAR cases. In most cases, the JAR was located distal to the tooth (66%) and was in contact with the mandibular canal, being in 53.2% with cortical and 40.4% without cortical. In 22 (46.82%) cases, the JAR caused thinning of the cortical plates, but no statistically significant differences were found among the buccal and lingual cortical plates (p=0.5728). It was concluded that JAR is not a rare image finding. The description of its imaging features and of its relationship with mandibular canal is important to call attention of professionals and contribute to its correct diagnosisMestradoRadiologia OdontologicaMestra em Radiologia Odontológic