11,233 research outputs found
p190 Rho-GTPase activating protein associates with plexins and it is required for semaphorin signalling
Plexins are transmembrane receptors for semaphorins, guiding cell migration and axon extension. Plexin activation leads to the disassembly of integrin-based focal adhesive structures and to actin cytoskeleton remodelling and inhibition of cell migration; however, the underlying molecular mechanisms are unclear. We consistently observe a transient decrease of cellular RhoA-GTP levels upon plexin activation in adherent cells. One of the main effectors of RhoA downregulation is p190, a ubiquitously expressed GTPase activating protein (GAP). We show that, in p190-deficient fibroblasts, the typical functional activities mediated by plexins (such as cell collapse and inhibition of integrin-based adhesion) are blocked or greatly impaired. Notably, the functional response can be rescued in these cells by re-expressing exogenous p190, but not a mutant form specifically lacking RhoGAP activity. We furthermore demonstrate that semaphorin function is blocked in epithelial cells, primary endothelial cells and neuroblasts upon treatment with small interfering RNAs that knockdown p190 expression. Finally, we show that p190 transiently associates with plexins, and its RhoGAP activity is increased in response to semaphorin stimulation. We conclude that p190-RhoGAP is crucially involved in semaphorin signalling to the actin cytoskeleton, via interaction with plexins
Efeito de herbicidas sobre a taxa de transporte de elĂ©trons e o acĂșmulo de matĂ©ria seca em tomateiro.
Objetivou-se com este trabalho avaliar o efeito dos herbicidas metribuzin e carfentrazone sobre a taxa de transporte de elĂ©trons (ETR) do fotossistema II (FSII) e o acĂșmulo de matĂ©ria seca em tomateiro.CD-ROM. Suplemento. Trabalho apresentado no 51. Congresso Brasileiro de Olericultura, Viçosa, MG
Conditional control of quantum beats in a cavity QED system
We probe a ground-state superposition that produces a quantum beat in the
intensity correlation of a two-mode cavity QED system. We mix drive with
scattered light from an atomic beam traversing the cavity, and effectively
measure the interference between the drive and the light from the atom. When a
photon escapes the cavity, and upon detection, it triggers our feedback which
modulates the drive at the same beat frequency but opposite phase for a given
time window. This results in a partial interruption of the beat oscillation in
the correlation function, that then returns to oscillate.Comment: 9 pages, 5 figures, XVII Reuni\'on Iberoamericana de \'Optica, X
Encuentro de \'Optica, L\'aseres y Aplicaciones (RIAO-OPTILAS-2010
From START to FINISH : the influence of osmotic stress on the cell cycle
Peer reviewedPublisher PD
CaracterizaciĂłn del lixiviado de un relleno sanitario de Jujuy (Argentina)
Se determinaron las caracterĂsticas de los lĂquidos de lixiviado extraĂdos de mi vertedero de residuos sĂłlidos domiciliarios de la provincia de Jujuy, a travĂ©s de dos muĂ©streos realizados en dos estaciones del aflo diferentes. Los anĂĄlisis efectuados fueron: pH, oxĂgeno consumido del permanganato, sĂłlidos sedimentables en 10 minutos, demanda bioquĂmica de oxĂgeno a los 5 dĂas , sulfuros, plomo, mercurio, arsĂ©nico, fenoles, detergentes, oxĂgeno disuelto, hierro, alcalinidad total, demanda quĂmica de oxĂgeno total.
Los resultados hallados se apartan, en su mayorĂa, de los valores exigidos por la reglamentaciĂłn local, y corresponden, segĂșn comparaciones con la bibliografĂa existente sobre el tema, a un lixiviado evolucionado.Tema: Tratamiento de efluentes. Biomasa.AsociaciĂłn Argentina de EnergĂa Sola
Dynamic modeling of mean-reverting spreads for statistical arbitrage
Statistical arbitrage strategies, such as pairs trading and its
generalizations, rely on the construction of mean-reverting spreads enjoying a
certain degree of predictability. Gaussian linear state-space processes have
recently been proposed as a model for such spreads under the assumption that
the observed process is a noisy realization of some hidden states. Real-time
estimation of the unobserved spread process can reveal temporary market
inefficiencies which can then be exploited to generate excess returns. Building
on previous work, we embrace the state-space framework for modeling spread
processes and extend this methodology along three different directions. First,
we introduce time-dependency in the model parameters, which allows for quick
adaptation to changes in the data generating process. Second, we provide an
on-line estimation algorithm that can be constantly run in real-time. Being
computationally fast, the algorithm is particularly suitable for building
aggressive trading strategies based on high-frequency data and may be used as a
monitoring device for mean-reversion. Finally, our framework naturally provides
informative uncertainty measures of all the estimated parameters. Experimental
results based on Monte Carlo simulations and historical equity data are
discussed, including a co-integration relationship involving two
exchange-traded funds.Comment: 34 pages, 6 figures. Submitte
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