Conjunctive input processing drives feature selectivity in hippocampal CA1 neurons

Feature-selective firing allows networks to produce representations of the external and internal environments. Despite its importance, the mechanisms generating neuronal feature selectivity are incompletely understood. In many cortical microcircuits the integration of two functionally distinct inputs occurs nonlinearly through generation of active dendritic signals that drive burst firing and robust plasticity. To examine the role of this processing in feature selectivity, we recorded CA1 pyramidal neuron membrane potential and local field potential in mice running on a linear treadmill. We found that dendritic plateau potentials were produced by an interaction between properly timed input from entorhinal cortex and hippocampal CA3. These conjunctive signals positively modulated the firing of previously established place fields and rapidly induced new place field formation to produce feature selectivity in CA1 that is a function of both entorhinal cortex and CA3 input. Such selectivity could allow mixed network level representations that support context-dependent spatial maps.Howard Hughes Medical InstituteRikagaku Kenkyūjo (Japan

QCD and strongly coupled gauge theories : challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference

Influência do resfriamento dinâmico na medição da tensão limite de escoamento

Non-Newtonian fluids may present several complex characteristics, such as viscoelasticity, plasticity and thixotropy. Understanding the behaviour of these materials is essential to facilitate its applicability, since many of them are present in daily life, such as gels, chocolate, and mayonnaise. The material studied on the present work was an waxy crude oil. The oil, present in reservoirs located in deep water, when subjected to low temperatures during production shutdowns, precipitates its paraffin, creating a structure which may be very resistant to flow. Thus, the formed material may represent a great difficulty to production restart. The design of pumps and compressors used in these systems depend on a rheological property called yield stress and therefore, it is essential to obtain reliable values of this rheological parameter. However, the complex behaviour, and the dependence of the crude oil characteristics on the shearing and temperature history make this a challenging task. Besides these, other factors may influence the measurement of yield stress, as the effect of wall slip and if the cooling is static or dynamic. This work shows the variation of yield stress for tests with dynamic cooling. The imposition of a stress during cooling caused the reduction in yield stress 0. Increasing the imposed stress, 0 decreased until it reached a minimum. Next, it was noticed an increase in yield stress with increasing imposed stress. The experiments carried out in this work were made in a commercial stress control rheometer. The effect of wall slip was tested by comparing smooth and rough geometries and it was verified signs of its presence, with the reduction of yield stress for smooth geometries. The equation of Weissenberg-Rabinowitsch, used for correction of the inhomogeneity of the shear stress along the radius geometry, seemed to be not necessary for the demonstrated results.Fluidos não newtonianos podem apresentar diversas características complexas, como a viscoelasticidade, plasticidade e tixotropia. Entender o comportamento de materiais tão complexos é fundamental para facilitar sua aplicabilidade, já que muitos estão presentes no cotidiano das pessoas, como géis, chocolate e maionese. O material estudado no presente trabalho foi um petróleo parafínico. O petróleo, presente em bacias localizadas em águas profundas, quando submetido a baixas temperaturas durante paradas de produção, precipita suas parafinas dando origem a uma estrutura que pode ser muito resistente ao escoamento. Dessa forma, o material formado pode representar uma grande dificuldade para o reinício da produção. O dimensionamento das bombas e compressores utilizados para retomada da produção depende de uma propriedade reológica denominada tensão limite de escoamento e, por isso, é fundamental obter valores confiáveis desse parâmetro reológico. No entanto, o comportamento complexo, e a dependência das características do petróleo com o histórico de cisalhamento e temperatura tornam a tarefa desafiadora. Outros fatores podem influenciar na medição da tensão limite de escoamento, como o efeito do escorregamento na parede do sensor da geometria e se o resfriamento é estático ou dinâmico. Este trabalho mostra a variação da tensão limite de escoamento para ensaios com resfriamento dinâmico. A imposição de tensão durante o resfriamento causou a redução da tensão limite de escoamento 0. Elevando-se a tensão imposta, 0 reduziu até atingir um valor mínimo. Em seguida, percebeu-se um aumento da tensão limite de escoamento com o aumento da tensão imposta. Os experimentos realizados neste trabalho foram feitos em um reômetro comercial do tipo tensão controlada (“stress controlled”). O efeito de escorregamento da amostra foi testado comparando geometrias com superfícies lisas e ranhuradas e foi possível verificar sinais de sua presença, com a redução da tensão limite de escoamento para geometrias lisas. A equação de Weissenberg-Rabinowitsch, utilizada para correção da não homogeneidade da tensão de cisalhamento ao longo do raio da geometria, mostrou-se não necessária para os resultados demonstrados