Polychlorinated biphenyls in the Brazilian breast milk : development of analytical methodology and evaluation of the contamination

Orientadores: Helena Teixeira Godoy, Fabio AugustoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de AlimentosResumo: Um estudo sobre a contaminação do leite materno com bifenilas policloradas (PCB) foi desenvolvido objetivando um conhecimento mais amplo dessa problemática no nosso país. Para isso, amostras de leite foram coletadas em nove estados brasileiros e questionários contendo perguntas sobre hábitos alimentares, condições sócio-econômicas, locais de habitação entre outras foram aplicados às mães doadoras. A determinação dos PCB foi feita por Microextração em Fase Sólida no modo headspace (HS-SPME) combinada com Cromatografia Gasosa e Detector de Captura de Elétrons (GC-ECD). As etapas da SPME foram otimizadas univariadamente e através de planejamento experimental Doehlert. A análise de variância mostrou que a temperatura de extração e a força iônica do meio (estudada através da adição de NaCl) foram as variáveis que mais influenciaram nas quantidades de PCB extraídas. Em seguida, refinaram-se as condições experimentais através de uma abordagem neuro-genética (rede neural Bayesiana aliada a algoritmos genéticos) que identificou como o ponto experimental ótimo a seguinte condição: concentração de NaCl de 0,36 g mL-1, temperatura de extração de 95,0 °C, tempo de extração de 60 minutos e adição de 210 µL de metanol. Após a otimização, o método foi validado através do estudo das figuras de mérito e apresentou-se linear na faixa estudada (1 a 16 µg L-1) com r > 0,9884, além de boa precisão (RSD 0.9884, besides good precision (RSD < 12 %, n = 5), acceptable recuperation (71 to 127 %) and limits of quantization between 0.45 µg L-1 and 2.42 µg L-1. In order to establish correlations between the results of the samples (expressed as chromatographic areas) and the results obtained in the questionnaires, Kohonen neural network had been used. Thus, it was possible to check that in the metropolitan cities the accumulation of PCB in the milk is more expressive than in other regions. For example, in Sao Paulo state, 58 % of the samples were contaminated by some PCB, mainly the congener 180 and 153. Another result produced by the net was that the samples of hindmilk (higher fat percentage) were the most contaminated. The number of gestations also was an important factor to be considered, since the study showed that the first son normally receives a higher dosage of PCB compared to the others. Also higher levels of contamination was found in the milk of mothers who lived in the proximities of industries and/or polluted rivers, corroborating with the fact that these compounds are easily spread in the environment and consequently in the human beingsDoutoradoDoutor em Ciência de Alimento

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements