Signatures of fractal clustering of aerosols advected under gravity

Aerosols under chaotic advection often approach a strange attractor. They move chaotically on this fractal set but, in the presence of gravity, they have a net vertical motion downwards. In practical situations, observational data may be available only at a given level, for example at the ground level. We uncover two fractal signatures of chaotic advection of aerosols under the action of gravity. Each one enables the computation of the fractal dimension $D_{0}$ of the strange attractor governing the advection dynamics from data obtained solely at a given level. We illustrate our theoretical findings with a numerical experiment and discuss their possible relevance to meteorology.Comment: Accepted for publication in Phys. Rev. E (Rapid Communications

Büchwald-Hartwig reaction applied to synthesis of new luminescent liquid crystal triarylamines derived from isoxazoles

© 2015 Taylor & Francis Group, LLC. The present work describes the synthesis and characterization of novel series of triarylamines isoxazoles (TAA) addressed to the organic photovoltaic materials. Diarylisoxazoles were synthesized by sequential [3+2] 1,3-dipolar cycloaddition reaction between arylnitrile oxides and selected arylalkenes followed by MnO2-oxidation. Isoxazoles were coupled to diarylamines by Büchwald-Hartwig reaction to afford desired compounds 6a-k. Some TAA display liquid-crystalline behaviour and UV-Vis absorption and fluorescence emission were analysed for all samples of TAA 6a-k

Geometry, stochastic calculus and quantum fields in a non-commutative space-time

The algebras of non-relativistic and of classical mechanics are unstable algebraic structures. Their deformation towards stable structures leads, respectively, to relativity and to quantum mechanics. Likewise, the combined relativistic quantum mechanics algebra is also unstable. Its stabilization requires the non-commutativity of the space-time coordinates and the existence of a fundamental length constant. The new relativistic quantum mechanics algebra has important consequences on the geometry of space-time, on quantum stochastic calculus and on the construction of quantum fields. Some of these effects are studied in this paper.Comment: 36 pages Latex, 1 eps figur

Evolução do número de pessoas ocupadas na agropecuária brasileira no período de 1990 a 2004.

O mercado de trabalho rural eliminou muitos postos de trabalho nos últimos 14 anos, principalmente em razão da ampliação do uso de tecnologia pelo setor. No caso do Brasil, o aumento das exportações e o crescimento da produção destinada ao mercado interno contribuíram positivamente para a geração de novos empregos, mas tais fatores foram insuficientes para compensar as vagas fechadas pela mudança tecnológica e pelas importações de produtos agrícolas. Na agropecuária, as importações tiveram impacto relativamente pequeno (235,7 mil postos de trabalho eliminados), apesar de terem afetado fortemente o emprego em alguns setores, tais como os do trigo, do arroz e do leite. Já o aumento das exportações, esse foi responsável por 30,2% do total de empregos gerados pelo setor, com o restante (69,8%) ficando a cargo do crescimento promovido pela demanda doméstica. Embora o processo de ajuste no mercado de trabalho da agropecuária nacional tenha, em decorrência da variável “mudança tecnológica”, aprofundado-se nos últimos anos, ainda assim o número de pessoas ocupadas no setor vem crescendo desde 2002, o que reforça a hipótese de que o aumento nas vendas internas e, sobretudo, das externas, gerou mais postos de trabalho que os eliminados pela adoção de novas tecnologias

Sex-related dietary changes of Portuguese university students after migration to London, UK

Aim: To assess the changes in eating habits and food choice motives of Portuguese university students after migration to London, according to sex. Methods: Fifty-five Portuguese university students (52.7% female) from 12 randomly selected London universities underwent a face-to-face interview. Trained interviewers administered a structured questionnaire comprising questions on socio-demographic characteristics, the frequency of consumption of selected food and beverage items, and the motives underlying food choices regarding Portugal and London practices. Results: Some dietary changes occurred in both male and female Portuguese students such as a decrease in the intake of red meat, fish, pastries and vegetable soup, and an increase in the intake of hamburger and tea with milk. Men also reported a decrease in the intake of cheese, dairy desserts, eggs, smoked sausages, ham, sweet spreads, potatoes, rice and fresh fruit, and an increase in the intake of bacon. For women, the consumption frequency of chips and chocolate increased and of vegetables decreased. Regarding food choice, the motives related to food purchasing and preparation became more important after migration to London for both sexes. The importance of nutritional information for women and weight control for men also increased after migration. Conclusions: A shift from a Mediterranean diet towards a more Western diet was observed after migration. Men were more likely to change their dietary habits whereas women were more likely to maintain. Food choice in London was greatly influenced by food purchasing and preparation