Efeito da temperatura no perfil de ácidos graxos do óleo de girassol.

Neste trabalho são apresentados resultados de composição de óleos extraídos de girassóis, convencionais e alto oleico, semeados na safra e na safrinha, com o objetivo de investigar o efeito da temperatura na produção de óleo e na proporção dos principais ácidos graxos em sua composiçã

Step-induced unusual magnetic properties of ultrathin Co/Cu films: ab initio study

We have performed ab initio studies to elucidate the unusual magnetic behavior recently observed in epitaxial Co films upon absorption of submonolayers of Cu and other materials. We find that a submonolayer amount of Cu on a stepped Co/Cu (100) film changes dramatically the electronic and magnetic structure of the system. The effect is mainly due to hybridization of Co and Cu $d$-electrons when copper forms a ``wire'' next to a Co step at the surface. As a result, a non-collinear arrangement of magnetic moments (switching of the easy axis) is promoted. [PACS 75.70.Ak,75.70.-i]Comment: 10 pages, RevTeX 3.0, 4 PostScript figures available on request from A. Bratkovsky at [email protected]

Ab initio study of the vapour-liquid critical point of a symmetrical binary fluid mixture

A microscopic approach to the investigation of the behaviour of a symmetrical binary fluid mixture in the vicinity of the vapour-liquid critical point is proposed. It is shown that the problem can be reduced to the calculation of the partition function of a 3D Ising model in an external field. For a square-well symmetrical binary mixture we calculate the parameters of the critical point as functions of the microscopic parameter r measuring the relative strength of interactions between the particles of dissimilar and similar species. The calculations are performed at intermediate ($\lambda=1.5$) and moderately long ($\lambda=2.0$) intermolecular potential ranges. The obtained results agree well with the ones of computer simulations.Comment: 14 pages, Latex2e, 5 eps-figures included, submitted to J.Phys:Cond.Ma

Thermal tool for evaluation of essential oils of Eucalyptus spp susceptible and resistant to Glycaspis brimblecombei attack.

Eucalyptus spp genus is economically important to different industry fields. There are pests that damage the development of eucalypts and Glycaspis brimblecombei, a sap-sucking insect, is one of them. Studies about this insect attack to the eucalypts showed preferences. This work aim was to compare the preferences of the insect with thermoanalytical characteristics of different eucalypts (susceptible, less susceptible and resistant to Glycaspis brimblecombei) essential oils. The leaves of six species of Eucalyptus were crushed and the essential oil was extracted using Clevenger apparatus. The Shimadzu DTG-60H was used to analyze the samples. The results showed that the samples from more susceptible eucalypts had total mass loss at about 124ºC to 156ºC, lower than samples from more resistant eucalypts (from 168ºC to 175ºC). Furthermore, the study suggests that the susceptibility or the resistance of eucalypts to the pest may be related to their essential oil composition and concentration of monoterpenes and sesquiterpenes.Disponível online

Avaliação termoanalítica de óleos essenciais de Eucalyptus spp suscetíveis e resistentes ao psilideo-de-concha.

O Glycaspis brimblecombei é uma praga florestal que ataca diversas espécies de eucalipto. Os terpenos e monoterpenos são os principais constituintes dos óleos essenciais do eucalipto. Amostras de óleos essenciais foram extraídas de folhas trituradas de eucaliptos resistentes e suscetíveis a este inseto. Os óleos foram analisados pelas técnicas termoanalíticas e observados comportamentos diferentes para os extraídos de eucaliptos resistentes e suscetíveis. Mais estudos são necessários para determinar as composições.Edição dos Anais do 7º Simpósio de Análise Térmica, 2015, Bauru

Solvent contribution to the stability of a physical gel characterized by quasi-elastic neutron scattering

The dynamics of a physical gel, namely the Low Molecular Mass Organic Gelator {\textit Methyl-4,6-O-benzylidene-$\alpha$ -D-mannopyranoside ($\alpha$-manno)} in water and toluene are probed by neutron scattering. Using high gelator concentrations, we were able to determine, on a timescale from a few ps to 1 ns, the number of solvent molecules that are immobilised by the rigid network formed by the gelators. We found that only few toluene molecules per gelator participate to the network which is formed by hydrogen bonding between the gelators' sugar moieties. In water, however, the interactions leading to the gel formations are weaker, involving dipolar, hydrophobic or $\pi-\pi$ interactions and hydrogen bonds are formed between the gelators and the surrounding water. Therefore, around 10 to 14 water molecules per gelator are immobilised by the presence of the network. This study shows that neutron scattering can give valuable information about the behaviour of solvent confined in a molecular gel.Comment: Langmuir (2015

Population inversion of a NAHS mixture adsorbed into a cylindrical pore

A cylindrical nanopore immersed in a non-additive hard sphere binary fluid is studied by means of integral equation theories and Monte Carlo simulations. It is found that at low and intermediate values of the bulk total number density the more concentrated bulk species is preferentially absorbed by the pore, as expected. However, further increments of the bulk number density lead to an abrupt population inversion in the confined fluid and an entropy driven prewetting transition at the outside wall of the pore. These phenomena are a function of the pore size, the non-additivity parameter, the bulk number density, and particles relative number fraction. We discuss our results in relation to the phase separation in the bulk.Comment: 7 pages, 8 Figure

Interface depinning versus absorbing-state phase transitions

According to recent numerical results from lattice models, the critical exponents of systems with many absorbing states and an order parameter coupled to a non-diffusive conserved field coincide with those of the linear interface depinning model within computational accuracy. In this paper the connection between absorbing state phase transitions and interface pinning in quenched disordered media is investigated. For that, we present a mapping of the interface dynamics in a disordered medium into a Langevin equation for the active-site density and show that a Reggeon-field-theory like description, coupled to an additional non-diffusive conserved field, appears rather naturally. Reciprocally, we construct a mapping from a discrete model belonging in the absorbing state with-a-conserved-field class to a discrete interface equation, and show how a quenched disorder is originated. We discuss the character of the possible noise terms in both representations, and overview the critical exponent relations. Evidence is provided that, at least for dimensions larger that one, both universality classes are just two different representations of the same underlying physics.Comment: 8 page

Holographic studies of quasi-topological gravity

Quasi-topological gravity is a new gravitational theory including curvature-cubed interactions and for which exact black hole solutions were constructed. In a holographic framework, classical quasi-topological gravity can be thought to be dual to the large $N_c$ limit of some non-supersymmetric but conformal gauge theory. We establish various elements of the AdS/CFT dictionary for this duality. This allows us to infer physical constraints on the couplings in the gravitational theory. Further we use holography to investigate hydrodynamic aspects of the dual gauge theory. In particular, we find that the minimum value of the shear-viscosity-to-entropy-density ratio for this model is $\eta/s \simeq 0.4140/(4\pi)$.Comment: 45 pages, 6 figures. v2: References adde

INVESTIGAÇÃO FITOQUÍMICA E AVALIAÇÃO DA ATIVIDADE ANTIBACTERIANA DA Mikania lanuginosa DC (ASTERACEAE)

O presente trabalho envolveu extração, isolamento, purificação e identificação dos constituintes químicos das partes aéreas da Mikania lanuginosa DC (ASTERACEAE). No processo de extração ocorreu a formação de um precipitado, no qual foi isolado e purificado um composto majoritário, que por análises espectroscópicas de IV, RMN 1H, RMN 13C e por comparação com os dados existentes na literatura, foi identificado como sendo o diterpeno ácido caurenóico. Foram realizados ensaios biológicos para avaliar a ação antimicrobiana com o precipitado, extrato etanólico bruto, as frações hexânica, diclorometano, acetato de etila, butanólica e o diterpeno ácido caurenóico contra as cepas Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228 e Bacillus cereus, pela técnica da difusão em meio sólido por cavidade e posteriormente pelo método de diluição em placa. Os resultados demonstraram que as frações hexânica, diclorometano, acetato de etila, butanólica e o ácido caurenóico obtidos da M. lanuginosa, apresentaram atividade antimicrobiana moderada frente as bactérias Gram positivas e foram inativos contra as bactérias Gram negativas. Phytochemical Investigation and Antimicrobial Activity Evaluation of the Mikania lanuginosa DC (ASTERACEAE) Abstract The present study investigated the extraction, isolation and purification the chemical compounds of the aerial parts of Mikania lanuginosa DC (ASTERACEAE). In the process of extraction it occurred the formation of a precipitate, it which was isolated and purified a ruling compound, and by spectroscopic analysis of the IR, 1H NMR, 13C NMR and comparison with reported data in the literature it was identified as being the diterpene kaurenoic acid. It were performed biological assays to estimate the antimicrobial action with the precipited, crude etanolic extract, hexane, dichoromethane, acetate ethyl, butane fractions and diterpene kaurenoic acid contrasting with strains Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228 e Bacillus cereus, by technique of the diffusion in solid mean by cavity and afterwards by the plaque dilution method. The results showed that the hexane, dichoromethane, acetate ethyl, butane fractions and the kaurenoic acid obtained from the Mikania lanuginosa DC presented a moderate antimicrobial activity face to Gram positives bacteria and got inert against the Gram negatives bacteria