Simulation of Entangled Polymer Solutions

We present a computer simulation of entangled polymer solutions at equilibrium. The chains repel each other via a soft Gaussian potential, appropriate for semi-dilute solutions at the scale of a correlation blob. The key innovation to suppress chain crossings is to use a pseudo-continuous model of a backbone which effectively leaves no gaps between consecutive points on the chain, unlike the usual bead-and-spring model. Our algorithm is sufficiently fast to observe the entangled regime using a standard desktop computer. The simulated structural and mechanical correlations are in fair agreement with the expected predictions for a semi-dilute solution of entangled chains

Polymer brush collapse under shear flow

Shear responsive surfaces offer potential advances in a number of applications. Surface functionalisation using polymer brushes is one route to such properties, particularly in the case of entangled polymers. We report on neutron reflectometry measurements of polymer brushes in entangled polymer solutions performed under controlled shear, as well as coarse-grained computer simulations corresponding to these interfaces. Here we show a reversible and reproducible collapse of the brushes, increasing with the shear rate. Using two brushes of greatly different chain lengths and grafting densities, we demonstrate that the dynamics responsible for the structural change of the brush are governed by the free chains in solution rather than the brush itself, within the range of parameters examined. The phenomenon of the brush collapse could find applications in the tailoring of nanosensors, and as a way to dynamically control surface friction and adhesion

Falsificação de medicamentos no Brasil

OBJETIVO: Identificar os principais medicamentos falsificados apreendidos pela Polícia Federal brasileira e os estados em que houve a apreensão. MÉTODOS: Estudo retrospectivo descritivo dos laudos periciais elaborados por Peritos Criminais da Polícia Federal sobre medicamentos contrafeitos entre janeiro de 2007 e setembro de 2010. RESULTADOS: Os medicamentos com maior número de apreensões foram inibidores seletivos da fosfodiesterase 5, utilizados para tratar a disfunção erétil masculina (Cialis® e Viagra®, em média 66%), seguidos por esteróides anabolizantes (Durateston® e Hemogenin®, 8,9% e 5,7%, respectivamente). A maior parte dos medicamentos falsos foi apreendida nos estados do Paraná, São Paulo e Santa Catarina, com incremento superior a 200% no número de medicamentos inautênticos encaminhados à perícia no período. Houve aumento nas apreensões de medicamentos contrabandeados arrecadados em conjunto com os falsos; 67% das apreensões incluíram no mínimo um medicamento contrabandeado. CONCLUSÕES: A falsificação de medicamentos é um grave problema de saúde pública. A identificação das classes de medicamentos falsos no País e os principais estados brasileiros com essa problemática podem facilitar ações futuras de prevenção e repressão pelos órgãos brasileiros responsáveis.OBJECTIVE: To identify the main counterfeit drugs seized by the Brazilian Federal Police and the states where seizures have been made. METHODS: A retrospective descriptive study on expert reports produced by criminal investigators of the Federal Police between January 2007 and September 2010, in relation to counterfeit drugs, was carried out. RESULTS: The drugs with greatest numbers of seizures were selective phosphodiesterase-5 inhibitors that are used for treating male erectile dysfunction (Cialis® and Viagra®, mean = 66% ), followed by anabolic steroids (Durateston® and Hemogenin®: 8.9% and 5.7%, respectively). The greatest proportions of the counterfeit drugs were seized in the states of Paraná, Santa Catarina (both Southeastern Brazil) and São Paulo (Southeastern), and the number of non-authentic drugs sent for investigation increased by more than 200% over the study period. There were increases in seizures of smuggled drugs found together with counterfeit drugs: 67% of the seizures included at least one smuggled drug. CONCLUSIONS: Counterfeiting of drugs is a severe public health problem. Identification of the classes of counterfeit drugs present in Brazil and the main Brazilian states with this problem may facilitate future preventive and suppressive actions by the Brazilian bodies responsible for such actions.OBJETIVO: Identificar los principales medicamentos falsificados incautados por la Policía Federal Brasileña y los estados donde hubo incautación. MÉTODOS: Estudio retrospectivo descriptivo de los laudos periciales elaborados por Peritos Criminales de la Policía Federal brasileña sobre medicamentos falsos entre enero de 2007 y septiembre de 2010. RESULTADOS: Los medicamentos con mayor número de incautaciones fueron los inhibidores selectivos de la fosfodiesterasa 5, utilizados para tratar la disfunción eréctil masculina (Ciallis® y Viagra®, en medio 66%), seguidos por esteroides anabolizantes (Durateston® y Hemogenin®, 8,9% y 5,7%, respectivamente). La mayor parte de los medicamentos falsos fue incautada en los estados Paraná, Sao Paulo y Santa Catarina, con incremento superior a 200% en el número de medicamentos inauténticos encaminados a la pericia en el período. Hubo aumento en las incautaciones de medicamentos contrabandeados arrecadados en conjunto con los falsos, 67% de las incautaciones incluyeron al menos un medicamento contrabandeado. CONCLUSIONES: La falsificación de medicamentos es un grave problema de salud pública. La identificación de las clases de medicamentos falsos en Brasil y los principales estados brasileños con esta problemática pueden facilitar acciones futuras de prevención y represión por los órganos brasileños responsables

Essential of Molecular Pharmacology

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