Consumo De Álcool Por Acadêmicos De Uma Instituição Comunitária No Período De Isolamento Social

Sabe-se que houve um aumento do consumo de álcool por parte dos jovens durante o período de isolamento social provocado pela pandemia de COVID-19, podendo aumentar a incidência de transtornos alimentares. Neste contexto, utilizou-se de um estudo transversal para avaliar o consumo de álcool por acadêmicos da área da saúde de uma universidade do norte do estado Rio Grande do Sul. Os dados foram coletados utilizando formulário eletrônico, com questões sobre o uso de álcool e risco para transtornos alimentares. Um total de 125 acadêmicos responderam ao questionário, sendo a maioria do sexo feminino (90,4%). No estudo, observou-se maior prevalência de uso de álcool de risco entre os acadêmicos com risco de desenvolvimento para transtorno alimentares (23,7%). Portanto, o consumo abusivo de álcool, o qual pode ter sido modificado pela pandemia, esteve presente no público avaliado, possuindo associação com distúrbios alimentares

Développement du modèle d’ion polarisable pour la modélisation de BaTiO3

Ferroelectric based compounds present a wide range of properties which are from great fundamental and industrial interest on nanoscale. Ferroelectric based compounds possesses strong coupling between polarization, stress, electric field and temperature and are nowadays already used in capacitors, memories, sensors, and actuators. In order to understand the relationship between microstructure and the outstanding properties, numerical methods able to simulate at nanoscale are disired. For this propose, the Polarizable Ion Model (PIM) is employed that treats the ions as polarizable species with nominal charge. In comparison to current modelisation techniques, the use of nominal charges should facilitate the inclusion of various materials composition and the study of defect and surface effects. The pametrization of the model is derived by a fit on ab initio DFT reference calculations. For a first step towards ferroelectric modelling with PIM, the focus lies on the developpment of an interaction potential for the prototyp ferroelectric BaTiO3. BaTiO3 presents a complex phase transition sequence (rhombohedral, orthorhombic, tetragonal, cubic) that is related to small energy differences of the order of some meV/formula unit. Thus, the development of a reliable interaction potential requires high precision and a correct description of the balance between short range and long range interactions. It has been demonstrated during this work that for an accurate representation of the short range forces asymmetric size effects of the electron cloud with respect to the nucleus would be necessary. As such size effects are not included in the PIM, compensation errors in the fitting procedure between short range and long range interactions are allowed in order to obtain the best global fit. The developed PIM model reproduces several zero temperature properties of BaTiO3. At finite temperature the PIM predicts the rhombohedral phase to be stable up to 160K. In the temperature range between 160K and 210K strong fluctuations in polarization and cell parameters are observed and no well-defined phase can be distinguished. From 210K on, the average paraelectric cubic phase is reached.Les composés à base de matériaux ferroélectriques présentent un large éventail de propriétés d'un grand intérêt fondamental et industriel. Ils possèdent un couplage entre la polarisation, la contrainte, le champ électrique et la température et trouvent application dans les dispositifs à l'échelle nanométrique. Les ferroélectriques sont aujourd'hui par exemple déjà utilisés dans les condensateurs, les mémoires, les capteurs et les actionneurs. Afin de comprendre la relation entre leurs propriétés physiques exceptionnelles et leur structure, des méthodes numériques capables de simuler à l'échelle nanométrique sont souhaitées. Pour ce faire, le modèle d'ions polarisables (PIM) est appliqué, modèle dans lequel les ions sont considérés comme des espèces polarisables possédant des charges nominales. En regard des techniques de modélisation actuelles, l'utilisation de charges nominales devrait faciliter l'inclusion de diverses compositions et l'étude des défauts et des effets de surface. Les paramètres du PIM sont dérivés par une procédure d'ajustement sur des données de références obtenues par des calculs avec la théorie de la fonctionnelle de la densité (DFT). Pour une première étape vers la modélisation ferroélectrique avec PIM, l'accent est mis sur le développement d'un potentiel d'interaction pour le prototype ferroélectrique BaTiO3. BaTiO3 présente une séquence complexe de transition de phase (rhomboédrique, orthorhombique, tétragonale, cubique) qui est liée à de petites différences d'énergie de l'ordre de quelques meV/unité de formule. Pour cette raison, le développement d'un potentiel d'interaction pour BaTiO3 nécessite une grande précision pour décrire correctement l’équilibre entre les interactions à courte et à longue portée. Il a été démontré au cours de ce travail que des effets asymétriques du nuage d'électrons par rapport au noyau seraient nécessaires pour une représentation précise des forces à courte portée. Puisque de tels effets ne sont pas inclus dans le PIM, des erreurs de compensation dans la procédure d'ajustement entre les interactions à courte et à longue portée sont permises afin d'obtenir le meilleur ajustement global. Le PIM développé pour BaTiO3 reproduit plusieurs propriétés à température nulle. À température finie, le PIM prédit que la phase rhomboédrique sera stable jusqu'à 160K. Dans la plage de température comprise entre 160K et 210K, de fortes fluctuations de la polarisation et des paramètres de maille sont observées et aucune phase bien définie ne peut être distinguée. A partir de 210K, la phase cubique paraélectrique est atteinte. Le modèle PIM développé dans cette thèse peut être appliqué à des études à basse température dans la phase ferroélectrique rhomboédrique. Il peut donc être utilisé pour étudier les effets de surface ou des lacunes d'oxygène dans la phase rhomboédrique de BaTiO3

Development of a polarizable ion model for barium titanate (BaTiO3 )

Les composés à base de matériaux ferroélectriques présentent un large éventail de propriétés d'un grand intérêt fondamental et industriel. Ils possèdent un couplage entre la polarisation, la contrainte, le champ électrique et la température et trouvent application dans les dispositifs à l'échelle nanométrique. Les ferroélectriques sont aujourd'hui par exemple déjà utilisés dans les condensateurs, les mémoires, les capteurs et les actionneurs. Afin de comprendre la relation entre leurs propriétés physiques exceptionnelles et leur structure, des méthodes numériques capables de simuler à l'échelle nanométrique sont souhaitées. Pour ce faire, le modèle d'ions polarisables (PIM) est appliqué, modèle dans lequel les ions sont considérés comme des espèces polarisables possédant des charges nominales. En regard des techniques de modélisation actuelles, l'utilisation de charges nominales devrait faciliter l'inclusion de diverses compositions et l'étude des défauts et des effets de surface. Les paramètres du PIM sont dérivés par une procédure d'ajustement sur des données de références obtenues par des calculs avec la théorie de la fonctionnelle de la densité (DFT). Pour une première étape vers la modélisation ferroélectrique avec PIM, l'accent est mis sur le développement d'un potentiel d'interaction pour le prototype ferroélectrique BaTiO3. BaTiO3 présente une séquence complexe de transition de phase (rhomboédrique, orthorhombique, tétragonale, cubique) qui est liée à de petites différences d'énergie de l'ordre de quelques meV/unité de formule. Pour cette raison, le développement d'un potentiel d'interaction pour BaTiO3 nécessite une grande précision pour décrire correctement l’équilibre entre les interactions à courte et à longue portée. Il a été démontré au cours de ce travail que des effets asymétriques du nuage d'électrons par rapport au noyau seraient nécessaires pour une représentation précise des forces à courte portée. Puisque de tels effets ne sont pas inclus dans le PIM, des erreurs de compensation dans la procédure d'ajustement entre les interactions à courte et à longue portée sont permises afin d'obtenir le meilleur ajustement global. Le PIM développé pour BaTiO3 reproduit plusieurs propriétés à température nulle. À température finie, le PIM prédit que la phase rhomboédrique sera stable jusqu'à 160K. Dans la plage de température comprise entre 160K et 210K, de fortes fluctuations de la polarisation et des paramètres de maille sont observées et aucune phase bien définie ne peut être distinguée. A partir de 210K, la phase cubique paraélectrique est atteinte. Le modèle PIM développé dans cette thèse peut être appliqué à des études à basse température dans la phase ferroélectrique rhomboédrique. Il peut donc être utilisé pour étudier les effets de surface ou des lacunes d'oxygène dans la phase rhomboédrique de BaTiO3 .Ferroelectric based compounds present a wide range of properties which are from great fundamental and industrial interest on nanoscale. Ferroelectric based compounds possesses strong coupling between polarization, stress, electric field and temperature and are nowadays already used in capacitors, memories, sensors, and actuators. In order to understand the relationship between microstructure and the outstanding properties, numerical methods able to simulate at nanoscale are disired. For this propose, the Polarizable Ion Model (PIM) is employed that treats the ions as polarizable species with nominal charge. In comparison to current modelisation techniques, the use of nominal charges should facilitate the inclusion of various materials composition and the study of defect and surface effects. The pametrization of the model is derived by a fit on ab initio DFT reference calculations. For a first step towards ferroelectric modelling with PIM, the focus lies on the developpment of an interaction potential for the prototyp ferroelectric BaTiO3. BaTiO3 presents a complex phase transition sequence (rhombohedral, orthorhombic, tetragonal, cubic) that is related to small energy differences of the order of some meV/formula unit. Thus, the development of a reliable interaction potential requires high precision and a correct description of the balance between short range and long range interactions. It has been demonstrated during this work that for an accurate representation of the short range forces asymmetric size effects of the electron cloud with respect to the nucleus would be necessary. As such size effects are not included in the PIM, compensation errors in the fitting procedure between short range and long range interactions are allowed in order to obtain the best global fit. The developed PIM model reproduces several zero temperature properties of BaTiO3. At finite temperature the PIM predicts the rhombohedral phase to be stable up to 160K. In the temperature range between 160K and 210K strong fluctuations in polarization and cell parameters are observed and no well-defined phase can be distinguished. From 210K on, the average paraelectric cubic phase is reached

Avaliação de um efluente industrial através de ensaios ecotoxicilógicos e análises físicas e químicas

Análises ecotoxicológicas vêm sendo empregadas no monitoramento de efluentes industriais com o intuito de minimizar o impacto ambiental, avaliar a eficiência de estações de tratamento, bem como requisito para a obtenção e manutenção de licenças junto aos órgãos ambientais. Com o objetivo de avaliar a toxicidade de um efluente industrial de origem petroquímica, foram realizados ensaios de toxicidade crônica com espécies de três diferentes níveis tróficos (Selenastrum capricornutum, Ceriodaphnia dubia e Pimephales promelas). As amostras do efluente foram também analisadas quanto aos valores de cianeto, DBO5, DQO, fenol, fósforo solúvel, fósforo total, nitrogênio amoniacal, nitrogênio total, óleos e graxas minerais, óleos e graxas totais, óleos e graxas vegetal/animal, oxigênio dissolvido, pH, sólidos suspensos totais, sulfeto, surfactantes e metais (mercúrio, cádmio, cobre, cromo, manganês, chumbo, zinco e níquel). As coletas ocorreram mensalmente, de agosto de 2002 a julho de 2003, na saída da estação de tratamento. Os resultados das análises físicas e químicas foram comparados com os limites de emissão disponíveis na Resolução nº 20/86 do CONAMA e Portaria Estadual nº 05/89 da Secretaria da Saúde e do Meio Ambiente (RS) A maioria dos parâmetros (85,7%) estava de acordo com a legislação vigente, exceto o fósforo total, o nitrogênio total e o nitrogênio amoniacal. No entanto, todas as amostras apresentaram toxicidade para pelo menos um dos organismos utilizados nos ensaios. Apesar de um maior número de amostras ter apresentado toxicidade para S. capricornutum, o efluente foi tóxico para P. promelas em concentrações mais baixas, se comparado com os outros dois organismos. Foi possível identificar correlação estatisticamente significativa (p≤0,05) entre a toxicidade para S. capricornutum e os valores de manganês (r=0,44), toxicidade para C. dubia e os valores de nitrogênio total e DQO (r=0,40) e toxicidade para P.promelas e os valores de sólidos suspensos totais, sulfeto, nitrogênio total e cianeto (r=0,71)

Avaliação de um efluente industrial através de ensaios ecotoxicilógicos e análises físicas e químicas

Análises ecotoxicológicas vêm sendo empregadas no monitoramento de efluentes industriais com o intuito de minimizar o impacto ambiental, avaliar a eficiência de estações de tratamento, bem como requisito para a obtenção e manutenção de licenças junto aos órgãos ambientais. Com o objetivo de avaliar a toxicidade de um efluente industrial de origem petroquímica, foram realizados ensaios de toxicidade crônica com espécies de três diferentes níveis tróficos (Selenastrum capricornutum, Ceriodaphnia dubia e Pimephales promelas). As amostras do efluente foram também analisadas quanto aos valores de cianeto, DBO5, DQO, fenol, fósforo solúvel, fósforo total, nitrogênio amoniacal, nitrogênio total, óleos e graxas minerais, óleos e graxas totais, óleos e graxas vegetal/animal, oxigênio dissolvido, pH, sólidos suspensos totais, sulfeto, surfactantes e metais (mercúrio, cádmio, cobre, cromo, manganês, chumbo, zinco e níquel). As coletas ocorreram mensalmente, de agosto de 2002 a julho de 2003, na saída da estação de tratamento. Os resultados das análises físicas e químicas foram comparados com os limites de emissão disponíveis na Resolução nº 20/86 do CONAMA e Portaria Estadual nº 05/89 da Secretaria da Saúde e do Meio Ambiente (RS) A maioria dos parâmetros (85,7%) estava de acordo com a legislação vigente, exceto o fósforo total, o nitrogênio total e o nitrogênio amoniacal. No entanto, todas as amostras apresentaram toxicidade para pelo menos um dos organismos utilizados nos ensaios. Apesar de um maior número de amostras ter apresentado toxicidade para S. capricornutum, o efluente foi tóxico para P. promelas em concentrações mais baixas, se comparado com os outros dois organismos. Foi possível identificar correlação estatisticamente significativa (p≤0,05) entre a toxicidade para S. capricornutum e os valores de manganês (r=0,44), toxicidade para C. dubia e os valores de nitrogênio total e DQO (r=0,40) e toxicidade para P.promelas e os valores de sólidos suspensos totais, sulfeto, nitrogênio total e cianeto (r=0,71)

Hole polarons in LaFeO 3 and La1−x_{1−x}Srx_xFeO3−δ_{3−δ} : Stability, trapping, mobility, effect of Sr concentration, and oxygen vacancies

International audienceThe stability, trapping and mobility of electron holes are investigated in lanthanum ferrite LaFeO$_3$ , and in La$_{1−x}$Sr$_x$FeO$_{3−δ}$ ($x$ ≈ 0.1, 0.4 and 0.6) by hybrid-density-functional and densityfunctional-theory $+ U$ calculations. In pure LaFeO$_3$ , the electron hole is more stable under a localized (polaronic) form than under a delocalized form, the energy difference (self-trapping energy) lie between ≈-0.3 and-0.4 eV. This self-trapped hole polaron is not strictly localized on a single Fe atom: instead, it occupies a quantum state made of a 3d orbital of a Fe atom, strongly hybridized with 2$p$ orbitals of four neighboring oxygens. The hole polaron is thus localized on five atoms (among which one single Fe), which can be described as the Fe$^{3+}$ oxidation into Fe$^{4+}$. Electron hole transport results from the combination of onsite reorientations and hoppings, with energy barriers estimated at ≈0.01–0.20 eV and 0.3–0.4 eV, respectively. The aliovalent substitution of lanthanum by strontium in LaFeO$_3$ induces the presence of localized electron holes, preserving the insulating character of La$_{1−x}$Sr$_x$FeO$_3$, regardless of the studied Sr concentration. The formation energy of the oxygen vacancy in La$_{1−x}$Sr$_x$FeO$_3$ (x ≈ 0.1 and 0.4) is estimated at ≈ +0.8 eV. This value is here successfully use to quantify the evolution of defect concentration as a function of the oxygen partial pressur

DFT study on elementary reaction pathways for La1−x_{1-x}Srx_xCo1−y_{1-y}Fey_yO3_3 electrode material

International audienceThanks to their high electrochemical activity combined with a good ionic and electronic conductivity, La$_{1-x}$Sr$_x$Co$_{1-y}$Fe$_y$O$_3$ (LSCF) based materials are commonly used as oxygen electrode in Solid Oxide Cells (SOCs) . The reaction mechanisms for the oxygen reduction/oxidation in LSCF play a key role not only on the cell performances but also on its durability. Indeed, LSCF is subjected to a decomposition in operation that can significantly affect degradation effects occurring at the LSCF electrode contribute to the overall cell lifetime . However, despite their importance, the reaction pathways taking place in the electrode are still not precisely understood especially in electrolysis mode. The mechanism for the oxygen reaction are based on fast kinetics associated to the dioxygen adsorption/desorption at the surface, incorporation/ex-corporation into the bulk, diffusion of adsorbed species on the surface and diffusion of oxygen ions towards the electrolyte. To better unravel these intricate phenomena, the reaction mechanisms in the bulk and at the LSCF surface have been studied at atomic scale via Density Functional Theory (DFT). First, the bulk properties of the parent material, La$_{1-x}$Sr$_x$FeO$_3$, have been investigated and coupled to a thermodynamic model able to predict accurately the oxygen vacancy concentration as a function of pressure and temperature . Then a slab model of LSCF has been built to explore the different possible reaction scenarios for the oxygen reaction in LSCF. The results of the DFT simulations have been discussed and used to better validate the reaction pathways implemented in an original elementary kinetic model developed for the LSCF electrode . After this first study, the coupling of the two models has been undertaken. For this purpose, the calculated activation energies with DFT are used to estimate the kinetic rate constants along with the diffusion coefficients trough Kinetic Monte Carlo (KMC) simulations. The multiscale approach will be finally integrated in a modeling package able to simulate the cell performance and its degradation upon operatio

Hole polarons in LaFeO 3 and La1−x_{1−x}Srx_xFeO3−δ_{3−δ} : Stability, trapping, mobility, effect of Sr concentration, and oxygen vacancies

International audienceThe stability, trapping and mobility of electron holes are investigated in lanthanum ferrite LaFeO$_3$ , and in La$_{1−x}$Sr$_x$FeO$_{3−δ}$ ($x$ ≈ 0.1, 0.4 and 0.6) by hybrid-density-functional and densityfunctional-theory $+ U$ calculations. In pure LaFeO$_3$ , the electron hole is more stable under a localized (polaronic) form than under a delocalized form, the energy difference (self-trapping energy) lie between ≈-0.3 and-0.4 eV. This self-trapped hole polaron is not strictly localized on a single Fe atom: instead, it occupies a quantum state made of a 3d orbital of a Fe atom, strongly hybridized with 2$p$ orbitals of four neighboring oxygens. The hole polaron is thus localized on five atoms (among which one single Fe), which can be described as the Fe$^{3+}$ oxidation into Fe$^{4+}$. Electron hole transport results from the combination of onsite reorientations and hoppings, with energy barriers estimated at ≈0.01–0.20 eV and 0.3–0.4 eV, respectively. The aliovalent substitution of lanthanum by strontium in LaFeO$_3$ induces the presence of localized electron holes, preserving the insulating character of La$_{1−x}$Sr$_x$FeO$_3$, regardless of the studied Sr concentration. The formation energy of the oxygen vacancy in La$_{1−x}$Sr$_x$FeO$_3$ (x ≈ 0.1 and 0.4) is estimated at ≈ +0.8 eV. This value is here successfully use to quantify the evolution of defect concentration as a function of the oxygen partial pressur