Avaliação geral, resultados e perspectivas do uso de agricultura de precisão em culturas perenes.

O Projeto Componente 4 da Rede de Agricultura de Precisão, intitulado ?Caracterização, manejo e monitoramento de atributos do solo e da planta em sistemas de produção de plantas perenes e semi-perenes? constitui-se de 7 planos de ação que contam com a participação interativa de várias unidades da Embrapa, instituições de pesquisa, universidades e parceiros da setor produtivo agrícola. A estratégia de trabalho baseia-se na implantação de unidades pilotos (UPs) de pesquisa em agricultura de precisão em diferentes regiões do Brasil, onde deverão ser analisadas diversas possibilidades de uso de procedimentos e ferramentas inerentes à agricultura de precisão (AP) em cultivos de videira, macieira, pessegueiro, citrus, espécies florestais, cana de açúcar e pastagem. A análise da variabilidade espacial e temporal de atributos do solo e da planta deverá ser utilizada na definição de zonas homogêneas, para um manejo mais eficiente dos sistemas de produção, quanto ao uso de espécies vegetais, água, solo, fertilizantes e defensivos agrícolas. Pretende-se também auxiliar o produtor quanto ao gerenciamento das informações do campo por meio de ferramentas e procedimentos utilizados em AP. Ainda, haverá a incorporação de profissionais à prática de AP, bem como a realização de pesquisas em sistemas de produção não abordados anteriormente quanto à AP no Brasil. Os impactos potenciais são o fornecimento, disseminação e transferência de procedimentos e ferramentas analíticas para adoção da agricultura de precisão em sistemas de produção de espécies perenes e semi-perenes, sendo que muitos deles poderão ser diretamente aplicados ou adaptados para outros sistemas de produção de culturas não contemplados nesse projeto componente

Avaliação geral, resultados e perspectivas do uso de agricultura de precisão em culturas perenes.

O Projeto Componente 4 da Rede de Agricultura de Precisão, intitulado ?Caracterização, manejo e monitoramento de atributos do solo e da planta em sistemas de produção de plantas perenes e semi-perenes? constitui-se de 7 planos de ação que contam com a participação interativa de várias unidades da Embrapa, instituições de pesquisa, universidades e parceiros da setor produtivo agrícola. A estratégia de trabalho baseia-se na implantação de unidades pilotos (UPs) de pesquisa em agricultura de precisão em diferentes regiões do Brasil, onde deverão ser analisadas diversas possibilidades de uso de procedimentos e ferramentas inerentes à agricultura de precisão (AP) em cultivos de videira, macieira, pessegueiro, citrus, espécies florestais, cana de açúcar e pastagem. A análise da variabilidade espacial e temporal de atributos do solo e da planta deverá ser utilizada na definição de zonas homogêneas, para um manejo mais eficiente dos sistemas de produção, quanto ao uso de espécies vegetais, águ a, solo, fertilizantes e defensivos agrícolas. Pretende-se também auxiliar o produtor quanto ao gerenciamento das informações do campo por meio de ferramentas e procedimentos utilizados em AP. Ainda, haverá a incorporação de profissionais à prática de AP, bem como a realização de pesquisas em sistemas de produção não abordados anteriormente quanto à AP no Brasil. Os impactos potenciais são o fornecimento, disseminação e transferência de procedimentos e ferramentas analíticas para adoção da agricultura de precisão em sistemas de produção de espécies perenes e semi-perenes, sendo que muitos deles poderão ser diretamente aplicados ou adaptados para outros sistemas de produção de culturas não contemplados nesse projeto componente

Langevin dynamics with a tilted periodic potential

We study a Langevin equation for a particle moving in a periodic potential in the presence of viscosity $\gamma$ and subject to a further external field $\alpha$. For a suitable choice of the parameters $\alpha$ and $\gamma$ the related deterministic dynamics yields heteroclinic orbits. In such a regime, in absence of stochastic noise both confined and unbounded orbits coexist. We prove that, with the inclusion of an arbitrarly small noise only the confined orbits survive in a sub-exponential time scale.Comment: 38 pages, 6 figure

A Born-Infeld-like f(R) gravity

Several features of an $f(R)$ theory in which there is a maximum value for the curvature are analyzed. The theory admits the vaccuum solutions of GR, and also the radiation evolution for the scale factor of the standard cosmological model. Working in the Jordan frame, a complete analysis of the phase space is performed, and its results supported with examples obtainted by numerical integration. In particular, we showed that theory has nonsingular cosmological solutions which after the bounce enter a phase of de Sitter expansion and subsequently relax to a GR-like radiation-dominated evolution.Comment: Latex file, 14 pages, 7 figures (jpg format), including more detailed discussions than previous version, accepted for publication in Physical Review

Shapes and Positions of Black Hole Shadows in Accretion Disks and Spin Parameters of Black Holes

Can we determine a spin parameter of a black hole by observation of a black hole shadow in an accretion disk? In order to answer this question, we make a qualitative analysis and a quantitative analysis of a shape and a position of a black hole shadow casted by a rotating black hole on an optically thick accretion disk and its dependence on an angular momentum of a black hole. We have found black hole shadows with a quite similar size and a shape for largely different black hole spin parameters and a same black hole mass. Thus, it is practically difficult to determine a spin parameter of a black hole from a size and a shape of a black hole shadow in an accretion disk. We newly introduce a bisector axis of a black hole shadow named a shadow axis. For a rotating black hole a shape and a position of a black hole shadow are not symmetric with respect to a rotation axis of a black hole shadow. So, in this case the minimum interval between a mass center of a black hole and a shadow axis is finite. An extent of this minimum interval is roughly proportional to a spin parameter of a black hole for a fixed inclination angle between a rotation axis of a black hole and a direction of an observer. In order to measure a spin parameter of a black hole, if a shadow axis is determined observationally, it is crucially important to determine a position of a mass center of a black hole in a region of a black hole shadow.Comment: 13 pages, 6 figures, accepted for publication in Ap

Structural dynamics and transient lipid binding of synaptobrevin-2 tune SNARE assembly and membrane fusion.

Intrinsically disordered proteins (IDPs) and their conformational transitions play an important role in neurotransmitter release at the neuronal synapse. Here, the SNARE proteins are essential by forming the SNARE complex that drives vesicular membrane fusion. While it is widely accepted that the SNARE proteins are intrinsically disordered in their monomeric prefusion form, important mechanistic aspects of this prefusion conformation and its lipid interactions, before forming the SNARE complex, are not fully understood at the molecular level and remain controversial. Here, by a combination of NMR and fluorescence spectroscopy methods, we find that vesicular synaptobrevin-2 (syb-2) in its monomeric prefusion conformation shows high flexibility, characteristic for an IDP, but also a high dynamic range and increasing rigidity from the N to C terminus. The gradual increase in rigidity correlates with an increase in lipid binding affinity from the N to C terminus. It could also explain the increased rate for C-terminal SNARE zippering, known to be faster than N-terminal SNARE zippering. Also, the syb-2 SNARE motif and, in particular, the linker domain show transient and weak membrane binding, characterized by a high off-rate and low (millimolar) affinity. The transient membrane binding of syb-2 may compensate for the repulsive forces between the two membranes and/or the SNARE motifs and the membranes, helping to destabilize the hydrophilic-hydrophobic boundary in the bilayer. Therefore, we propose that optimum flexibility and membrane binding of syb-2 regulate SNARE assembly and minimize repulsive forces during membrane fusion

Single-Cell RNA-seq Reveals Profound Alterations in Mechanosensitive Dorsal Root Ganglion Neurons with Vitamin E Deficiency.

Ninety percent of Americans consume less than the estimated average requirements of dietary vitamin E (vitE). Severe vitE deficiency due to genetic mutations in the tocopherol transfer protein (TTPA) in humans results in ataxia with vitE deficiency (AVED), with proprioceptive deficits and somatosensory degeneration arising from dorsal root ganglia neurons (DRGNs). Single-cell RNA-sequencing of DRGNs was performed in Ttpa-/- mice, an established model of AVED. In stark contrast to expected changes in proprioceptive neurons, Ttpa-/- DRGNs showed marked upregulation of voltage-gated Ca2+ and K+ channels in mechanosensitive, tyrosine-hydroxylase positive (TH+) DRGNs. The ensuing significant conductance changes resulted in reduced excitability in mechanosensitive Ttpa-/- DRGNs. A highly supplemented vitE diet (600 mg dl-α-tocopheryl acetate/kg diet) prevented the cellular and molecular alterations and improved mechanosensation. VitE deficiency profoundly alters the molecular signature and functional properties of mechanosensitive TH+ DRGN, representing an intriguing shift of the prevailing paradigm from proprioception to mechanical sensation

Constraints on DD Dimensional Warped Spaces

In order to investigate the phenomenological implications of allowing gauge fields to propagate in warped spaces of more than five dimensions, we consider a toy model of a space warped by the presence of a anisotropic bulk cosmological constant. After solving the Einstein equation, three classes of solutions are found, those in which the additional ($D>5$) dimensions are growing, shrinking or remaining constant. It is found that gauge fields propagating in these spaces have a significantly different Kaluza Klein (KK) mass spectrum and couplings from that of the Randall and Sundrum model. This leads to a greatly reduced lower bound on the KK scale, arising from electroweak constraints, for spaces growing towards the IR brane.Comment: 6 pages, 5 figures PASCOS2010 International Symposium proceedin

Decoherence from internal degrees of freedom for cluster of mesoparticles : a hierarchy of master equations

A mesoscopic evolution equation for an ensemble of mesoparticles follows after the elimination of internal degrees of freedom. If the system is composed of a hierarchy of scales, the reduction procedure could be worked repeatedly and the characterization of this iterating method is carried out. Namely, a prescription describing a discrete hierarchy of master equations for the density operator is obtained. Decoherence follows from the irreversible coupling of the systems, defined by mesoscopic variables, to internal degrees of freedom. We discuss briefly the existence of systems with the same dynamics laws at different scales. We made an explicit calculation for an ensemble of particles with internal harmonic interaction in an external anharmonic field. New conditions related to the semiclassical limit for mesoscopic systems (Wigner-function) are conjectured.Comment: 19 pages, 0 figures, late