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Estudo teórico de ácidos aminobenzóicos usando técnicas de mecânica quântica e simulação computacional / Theoretical study of aminobenzoic acid using technique of quantum mechanics and computational simulationValverde, Danillo Pires 01 March 2016 (has links)
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Previous issue date: 2016-03-01 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / In this work we realize a study of the aminobenzoic acid family (Abz) in neutral,
anionic and cationic conformations combining a Sequential QM/MM method with mean
field approximation (ASEC) with Free Energy Gradient method (FEG), for the solvents:
cyclohexane, acetonitrile and water. In all cases, the Abz molecules type present a
conformation in aqueous solution has greater geometry distortion compared to the gas
phase. According to our results, there is just one cationic conformation in aqueous solution
for ortho. For para and meta, anionic molecules the geometry is more stable planar
conformation, which is a saddle point in gas phase. For neutral ortho, the rotamer I is the
more energetically stable structure. In anionic conformations it is found the largest number
of hydrogen bonds in aqueous solution. In acetonitrile and water, the energy stability of
conformations can be explained by hydrogen bonds and solute molecule dipole moment.
In all cases, the peak of the first absorption band is in good agreement with experimental
results. Our results turn out to be more close to experimental result if explicit solvent
molecules are included. The theoretical absorption spectra has similar behaviour to those
obtained experimentally and the absorption band shifts are well described with ASEC,
mainly those involving the neutral, anionic and cationic conformations in water. / Neste trabalho é realizado o estudo da família de ácidos aminobenzóicos (Abz)
nas conformações neutra, aniônica e catiônica combinando o uso do método QM/MM
sequencial com a aproximação de um campo eletrostático médio (ASEC) juntamente
com o método de gradiente de energia Livre (FEG) para os solventes: ciclohexano,
acetonitrila e água. Em todas as moléculas estudadas, a conformação em solução aquosa
é a que apresenta maiores mudanças geométricas com respeito a fase gasosa. De acordo
com os nossos resultados, existe apenas uma conformação catiônica em solução aquosa
para o caso do orto. Nas moléculas aniônicas do p-Abz e do m-Abz a geometria mais
estável é a conformação planar, que em fase gasosa corresponde a um ponto de sela.
No caso do orto neutro, o rotâmero I é a estrutura mais favorável energeticamente.
As conformações aniônicas em geral efetuam mais ligações de hidrogênios LH em meio
aquoso. Em acetonitrila e água, a estabilidade energética é bem explicada pelas ligações
de hidrogênio e pelo momento de dipolo da molécula do soluto. O pico da 1ª banda de
absorção em todas as moléculas estudadas utilizando o ASEC se encontra em bom acordo
com o experimental, mas com a inclusão de algumas moléculas explícitas do solvente
os resultados obtidos se aproximam ainda mais do valor experimental. Os espectros de
absorção teóricos possuem comportamento similar aos obtidos experimentalmente e os
deslocamentos da banda de absorção são bem descrito com ASEC, principalmente os que
envolvem as conformações neutra, aniônica e catiônica em água.
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Efeitos do meio na estrutura conformacional e eletrônica de moléculas com grupos aceitador-doador / The effects of the medium in the electronic structure and configuration of molecules with acceptor-donor groupsFranco, Leandro Rezende Franco 29 February 2016 (has links)
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Previous issue date: 2016-02-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The combined use of the Sequential QM/MM method with the ASEC mean field
approximation [1] and the Free Energy Gradient method [2] has been very successful in
describing the electronic structure of molecules in solution [3]. The advantage of this
combination is that it permits the usage of an atomic- level modeling of the whole
system, in contrast to continuum models, and, at the same time, it is less computationally
expensive than ab initio or QM/MM simulations, even allowing the employment of more
sophisticated electronic structure methods. In this context, the present work deals with
the study of conformational and electronic structure, in solvent medium, of two organic
compounds, DMACA and Phenol Blue, which have in common the characteristic of having
acceptor-donor groups. The study is conducted in the presence of nonpolar, polar protic
and polar aprotic solvents. It is adopted as basic methodology the ASEC-FEG, but also it
is made a study with a continuum method, namely PCM. The results show that the solvent
effect causes a significant geometric distortion of the molecules of interest while causing
an internal charge displacement from donor group to acceptor group. Both effects are
more pronounced in protic and aprotic solvents but mainly in protic solvents, in which
hydrogen bonds lead to a greater solute polarization. The absorption spectra of these
molecules, calculated by TD-DFT (CAM-B3LYP), directly reflect these changes. For all
solvents, the absolute values of electronic transitions and their respective solvatochromic
shifts are in good agreement with the experimental results. / O uso combinado de métodos QM/MM sequencial com uma aproximação de
campo médio (ASEC) [1] e o método do Gradiente de Energia Livre [2] tem tido sucesso
na descrição da estrutura eletrônica de moléculas em solução [3]. Uma das vantagens
dessa combinação é que ela permite o tratamento do sistema soluto-solvente em um
nível atomístico, em contraste com modelos contínuos, e tem a vantagem de, ao mesmo
tempo, ser uma metodologia menos cara computacionalmente do que simulações QM/MM
ab initio [4]. Nesse contexto, o presente trabalho versa sobre o estudo da estrutura
conformacional e eletrônica, em meio, de dois compostos orgânicos, DMACA e Phenol
Blue, que tem em comum a característica de possuir grupos aceitador e doador de elétrons.
O estudo é realizado na presença de solventes apolares, polares apróticos e polares próticos.
Adota-se como metodologia básica o método QM/MM sequencial utilizando o ASEC, mas
faz-se também um estudo com um método contínuo conhecido, o PCM. Os resultados
mostram que o efeito de solvente provoca uma signifativa reestruturação geométrica
das moléculas de interesse, ao mesmo tempo em que causa um deslocamento interno
de carga do grupo doador para o grupo aceitador. Os dois efeitos são mais pronuciados
em solventes apróticos e próticos, mas principalmente nos solventes próticos, em que
as ligações de hidrogênio levam a uma maior polarização do soluto. Essas mudanças
refletem diretamente no espectro de absorção, calculado por TD-DFT (CAM-B3LYP),
dessas moléculas. Dos meios apolares, passando pelos polares apróticos, indo até os polares
próticos, os valores absolutos das transições eletrônicas e seus respectivos deslocamentos
solvatocrômicos encontram-se em bom acordo com os resultados experimentais.
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The Impact of Women Health Issues on Agricultural Production in FondwaBeauvais, Junior 26 June 2018 (has links)
Agriculture is the backbone of the Haitian economy and provides employment 80% employment to the Haitian population (Lundahl, 1992). Also 85% of people in rural areas generate money from agricultural activities (IFAD, 2008). In the rural areas, men and women participate in agricultural production. However, the women play a vital role in the whole process starting from land preparation to crop sale (Gaspard, 2013). The Haitian women, despite of their function in crop productions (Dor, 2016), face different health issues, which have influence over Haitian agricultural system. Therefore, the research purposed was to investigate the impact of women heath issues on agricultural production Fondwa. A qualitative case study was used to investigate ten women farmers in the community of Fondwa, which is a small farming area in southwest part of Haiti. An interview questionnaire was used for data collection. Findings of the study showed that the women's contribution to farming is vital for promoting agricultural production, and they face different health issues that are linked to the environment and water pollution. Lastly, the women health problems influence agricultural production in the Fondwa area by preventing them from doing their daily agricultural activities, which have a direct impact over family and country's income. / MSLFS / Fondwa is a small mountainous community village in the Southwest department of Haiti with a population of approximately 10,000 people. Corn, beans, and vegetables are the dominant crops in the area of Fondwa. In Fondwa, women play an important role in crop production and agricultural sale. However, these women, despite of their role in farming, face many health issues due to the lack of health infrastructure. The purpose of this study was to investigate the impact of women’s health issues on agricultural production in Fondwa. For this study, a sample of ten women from nine areas were selected for this study and these participants live in Fondwa. A qualitative method was used to conduct the research and interview questionnaire was used to gather information from the participants. The interview process was done via Skype meetings with the women. Results of the study showed that the 1) Fondwa women farmers play an important role in crop production in the community of Fondwa because they plant, harvest, and sale crops, which helps take care of their family. 2) The women have difficulty to receive healthcare service due to infrastructure problems in the community. 3) The women’s health issues are related to water and environmental issues. 4) The agricultural production in Fondwa will slow down without the women’s presence. The participants showed passion and dedication for agriculture despite of their health problems.
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