256 research outputs found

    Effect of a mixture of caffeine and nicotinamide on the solubility of vitamin (B2) in aqueous solution

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    The effect of caffeine (CAF) and nicotinamide (NMD) on the solubility of a vitamin B2 derivative (FMN) has been evaluated for mixtures containing either a single hydrotrope (CAF or NMD) or the two hydrotropes simultaneously. A model for analysis of ternary systems, which takes into account all possible complexes between the molecules, has been developed and tested with experimental NMR data on the three-component mixture FMN–CAF–NMD. The results indicate that special attention should be given to the concentration of a hydrotropic agent used to enhance the solubility of a particular drug. A decrease in the efficacy of solubility of the vitamin on addition of large amounts of hydrotropic agent is expected in the two-component systems due to the increased proportion of self-association of the hydrotrope. It is found that a mixture of two hydrotropic agents leads to an increase in the solubility of the vitamin in three-component compared to the two-component system. Rather than using just one hydrotropic agent, it is proposed that a strategy for optimising the solubility of aromatic drugs is to use a mixture of hydrotropic agents

    Quantum Mirrors and Crossing Symmetry as Heart of Ghost Imaging

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    In this paper it is proved that the key to understanding the ghost imaging mystery are the crossing symmetric photon reactions in the nonlinear media. Hence, the laws of the plane quantum mirror (QM) and that of spherical quantum mirror, observed in the ghost imaging experiments, are obtained as natural consequences of the energy-momentum conservation laws. So, it is shown that the ghost imaging laws depend only on the energy-momentum conservation and not on the photons entanglement. The extension of these results to the ghost imaging with other kind of light is discussed. Some fundamental experiments for a decisive tests of the [SPDC-DFG]-quantum mirror are suggested.Comment: 11 pages, 9 figure

    Trabalho, terra e geração de renda em três décadas de reflorestamentos no alto Jequitinhonha.

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    A partir dos anos 1970, as chapadas do Alto Jequitinhonha, localizadas no nordeste de Minas Gerais, até então áreas de uso comum de agricultores familiares, foram plantadas com eucaliptos. O objetivo deste artigo é comparar os efeitos do reflorestamento sobre a estrutura fundiária, valor da produção agrícola e ocupação rural com os efeitos da produção agrícola familiar sobre essas mesmas variáveis na microrregião homogênea de Capelinha, no Alto Jequitinhonha. Tal microrregião foi escolhida para o estudo por ser a área de maior concentração de eucaliptais da região. Foram utilizados dados secundários dos Censos do IBGE para os anos de 1970, 1980, 1985 e 1996, além de dados secundários de pesquisas realizadas sobre a região em questão, incluindo entrevistas com dirigentes de empresas e lideranças sindicais. O artigo conclui que, em trinta anos, o reflorestamento concentrou terras e criou um número reduzido de empregos; a agricultura familiar, ao contrário, teve suas áreas de terras comprimidas e super-exploradas em decorrência da perda das chapadas, mas continuou sendo a principal responsável pela geração de ocupações e rendas na região

    Destruction of diagonal and off-diagonal long range order by disorder in two-dimensional hard core boson systems

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    We use quantum Monte Carlo simulations to study the effect of disorder, in the form of a disordered chemical potential, on the phase diagram of the hard core bosonic Hubbard model in two dimensions. We find numerical evidence that in two dimensions, no matter how weak the disorder, it will always destroy the long range density wave order (checkerboard solid) present at half filling and strong nearest neighbor repulsion and replace it with a bose glass phase. We study the properties of this glassy phase including the superfluid density, energy gaps and the full Green's function. We also study the possibility of other localized phases at weak nearest neighbor repulsion, i.e. Anderson localization. We find that such a phase does not truly exist: The disorder must exceed a threshold before the bosons (at weak nn repulsion) are localized. The phase diagram for hard core bosons with disorder cannot be obtained easily from the soft core phase diagram discussed in the literature.Comment: 7 pages, 10 eps figures include

    The Psychedelic State Induced By Ayahuasca Modulates The Activity And Connectivity Of The Default Mode Network

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    The experiences induced by psychedelics share a wide variety of subjective features, related to the complex changes in perception and cognition induced by this class of drugs. A remarkable increase in introspection is at the core of these altered states of consciousness. Self-oriented mental activity has been consistently linked to the Default Mode Network (DMN), a set of brain regionsmore active during rest than during the execution of a goal-directed task. Here we used fMRI technique to inspect the DMN during the psychedelic state induced by Ayahuasca in ten experienced subjects. Ayahuasca is a potion traditionally used by Amazonian Amerindians composed by a mixture of compounds that increase monoaminergic transmission. In particular, we examined whether Ayahuasca changes the activity and connectivity of the DMN and the connection between the DMN and the task-positive network (TPN). Ayahuasca caused a significant decrease in activity throughmost parts of the DMN, including its most consistent hubs: the Posterior Cingulate Cortex (PCC)/Precuneus and the medial Prefrontal Cortex (mPFC). Functional connectivity within the PCC/Precuneus decreased after Ayahuasca intake. No significant change was observed in the DMN-TPN orthogonality. 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