1,114 research outputs found
Distribuição do carbono orgânico em Latossolo sob manejo da adubação fosfatada em plantio direto no Cerrado.
O objetivo deste trabalho foi avaliar a distribuição vertical e horizontal do carbono orgânico do solo (CO) sob cinco manejos da adubação fosfatada, no sistema plantio direto. O experimento foi instalado sob Latossolo Vermelho, cultivado durante oito anos com soja ou milho, com milheto como planta de cobertura na entressafra. As parcelas foram submetidas aos tratamentos: aplicação de superfosfato triplo a lanço e no sulco, fosfato natural reativo a lanço e no sulco, e ausência de adição de fertilizante fosfatado (testemunha). A adição anual dos adubos fosfatados, na dose de 80 kg ha‑1 de P2O5, foi realizada em solo inicialmente com baixo teor de fósforo disponível. Amostras foram coletadas perpendicularmente à linha de plantio, em sete pontos distanciados a 12,5 cm, e cinco camadas: 0?2,5, 2,5?5,0, 5,0?10, 10?20 e 20?30 cm. O conteúdo e a distribuição do CO são afetados pela adubação fosfatada, tanto vertical quanto horizontalmente, com os maiores conteúdos observados nos tratamentos com adubos fosfatados. Em comparação com a testemunha, o superfosfato triplo apresentou maior conteúdo de CO até a camada de 5,0?10 cm, e o fosfato natural reativo até 10?20 cm. A aplicação de fósforo em sulcos proporciona maior volume de solo com teores adequados de CO, em comparação à aplicação a lanço
Noether symmetries for two-dimensional charged particle motion
We find the Noether point symmetries for non-relativistic two-dimensional
charged particle motion. These symmetries are composed of a quasi-invariance
transformation, a time-dependent rotation and a time-dependent spatial
translation. The associated electromagnetic field satisfy a system of
first-order linear partial differential equations. This system is solved
exactly, yielding three classes of electromagnetic fields compatible with
Noether point symmetries. The corresponding Noether invariants are derived and
interpreted
Long-term in vivo imaging of fibrillar tau in the retina of P301S transgenic mice.
Tauopathies are widespread neurodegenerative disorders characterised by the intracellular accumulation of hyperphosphorylated tau. Especially in Alzheimer's disease, pathological alterations in the retina are discussed as potential biomarkers to improve early diagnosis of the disease. Using mice expressing human mutant P301S tau, we demonstrate for the first time a straightforward optical approach for the in vivo detection of fibrillar tau in the retina. Longitudinal examinations of individual animals revealed the fate of single cells containing fibrillar tau and the progression of tau pathology over several months. This technique is most suitable to monitor therapeutic interventions aimed at reducing the accumulation of fibrillar tau. In order to evaluate if this approach can be translated to human diagnosis, we tried to detect fibrillar protein aggregates in the post-mortem retinas of patients that had suffered from Alzheimer's disease or Progressive Supranuclear Palsy. Even though we could detect hyperphosphorylated tau, we did not observe any fibrillar tau or Aß aggregates. In contradiction to previous studies, our observations do not support the notion that Aβ or tau in the retina are of diagnostic value in Alzheimer's disease
On the linearization of the generalized Ermakov systems
A linearization procedure is proposed for Ermakov systems with frequency
depending on dynamic variables. The procedure applies to a wide class of
generalized Ermakov systems which are linearizable in a manner similar to that
applicable to usual Ermakov systems. The Kepler--Ermakov systems belong into
this category but others, more generic, systems are also included
Anisotropic Bose-Einstein condensates and completely integrable dynamical systems
A Gaussian ansatz for the wave function of two-dimensional harmonically
trapped anisotropic Bose-Einstein condensates is shown to lead, via a
variational procedure, to a coupled system of two second-order, nonlinear
ordinary differential equations. This dynamical system is shown to be in the
general class of Ermakov systems. Complete integrability of the resulting
Ermakov system is proven. Using the exact solution, collapse of the condensate
is analyzed in detail. Time-dependence of the trapping potential is allowed
Lie symmetries for two-dimensional charged particle motion
We find the Lie point symmetries for non-relativistic two-dimensional charged
particle motion. These symmetries comprise a quasi-invariance transformation, a
time-dependent rotation, a time-dependent spatial translation and a dilation.
The associated electromagnetic fields satisfy a system of first-order linear
partial differential equations. This system is solved exactly, yielding four
classes of electromagnetic fields compatible with Lie point symmetries
Generalized Hamiltonian structures for Ermakov systems
We construct Poisson structures for Ermakov systems, using the Ermakov
invariant as the Hamiltonian. Two classes of Poisson structures are obtained,
one of them degenerate, in which case we derive the Casimir functions. In some
situations, the existence of Casimir functions can give rise to superintegrable
Ermakov systems. Finally, we characterize the cases where linearization of the
equations of motion is possible
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CCR5AS lncRNA variation differentially regulates CCR5, influencing HIV disease outcome.
Multiple genome-wide studies have identified associations between outcome of human immunodeficiency virus (HIV) infection and polymorphisms in and around the gene encoding the HIV co-receptor CCR5, but the functional basis for the strongest of these associations, rs1015164A/G, is unknown. We found that rs1015164 marks variation in an activating transcription factor 1 binding site that controls expression of the antisense long noncoding RNA (lncRNA) CCR5AS. Knockdown or enhancement of CCR5AS expression resulted in a corresponding change in CCR5 expression on CD4+ T cells. CCR5AS interfered with interactions between the RNA-binding protein Raly and the CCR5 3' untranslated region, protecting CCR5 messenger RNA from Raly-mediated degradation. Reduction in CCR5 expression through inhibition of CCR5AS diminished infection of CD4+ T cells with CCR5-tropic HIV in vitro. These data represent a rare determination of the functional importance of a genome-wide disease association where expression of a lncRNA affects HIV infection and disease progression
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