Atividade da reductase do nitrato em milho (Zea mays L.) var. Piranão em níveis crescentes de nitrogênio.

O objetivo deste trabalho foi estudar a atividade da reductase do nitrato em milho (Zea mays L. var. "Piranao") cultivado em solucao nutritiva e sob doses crescentes de nitrogenio, na forma de NO3. A atividade da enzima foi analisada aos 56 dias de idade, em rodelas de folhas do terco medio da folha +4, seguindo-se a metodologia proposta por MULDER et alii (15), adaptada por MALAVOLTA (13). Os resultados permitiram concluir que o aumento do teor de NO3 no meio favoreceu a atividade da reductase do nitrato ate o nivel maximo de 40,51 ug de N-NO-2/g de materia verde, correspondente a um nivel de 296,19 mg de N/litro de solucao nutritiva. Os resultados obtidos nas condicoes experimentais em que foi realizado o trabalho correspondem, provavelmente, ao maximo da capacidade genetica da variedade estudada. Os teores de N encontrados nas folhas inferiores foram mais baixos do que os das folhas superiores, em funcao da alta mobilizacao do elemento para as partes mais novas da planta. Houve tambem correlacao positiva entre a atividade da reductase do nitrato, o teor de N total da folha e a producao de materia seca

Asymptotic statistics of the n-sided planar Poisson-Voronoi cell. I. Exact results

We achieve a detailed understanding of the $n$-sided planar Poisson-Voronoi cell in the limit of large $n$. Let ${p}\_n$ be the probability for a cell to have $n$ sides. We construct the asymptotic expansion of $\log {p}\_n$ up to terms that vanish as $n\to\infty$. We obtain the statistics of the lengths of the perimeter segments and of the angles between adjoining segments: to leading order as $n\to\infty$, and after appropriate scaling, these become independent random variables whose laws we determine; and to next order in $1/n$ they have nontrivial long range correlations whose expressions we provide. The $n$-sided cell tends towards a circle of radius (n/4\pi\lambda)^{\half}, where $\lambda$ is the cell density; hence Lewis' law for the average area $A\_n$ of the $n$-sided cell behaves as $A\_n \simeq cn/\lambda$ with $c=1/4$. For $n\to\infty$ the cell perimeter, expressed as a function $R(\phi)$ of the polar angle $\phi$, satisfies $d^2 R/d\phi^2 = F(\phi)$, where $F$ is known Gaussian noise; we deduce from it the probability law for the perimeter's long wavelength deviations from circularity. Many other quantities related to the asymptotic cell shape become accessible to calculation.Comment: 54 pages, 3 figure

Development of a Bayesian network-based early warning system for storm-driven coastal erosion

Coastal hazards such as flooding and erosion can cause large economic and human losses. Under this threat, early warning systems can be very cost-effective solutions for disaster preparation. The goal of this study was to develop, test, and implement an operational coastal erosion early warning system supported by a particular method of machine learning. Thus, the system combines Bayesian Networks, and state-of-the-art numerical models, such as XBeach and SWAN, to predict storm erosion impacts in urbanized areas. This system was developed in two phases. In the development phase, all information required to apply the machine learning method was generated including the definition of hundreds of oceanic synthetic storms, modeling of the erosion caused by these storms, and characterization of the impact levels according to a newly defined eerosion iimpact index. This adimensional index relates the distance from the edge of the dune/beach scarp to buildings and the height of that scarp. Finally, a Bayesian Network that acted as a surrogate of the previously generated information was built. After the training of the network, the conditional probability tables were created. These tables constituted the ground knowledge to make the predictions in the second phase. This methodology was validated (1) by comparing 6-h predictions obtained with the Bayesian Network and with process-based models, the latest considered as the benchmark, and (2) by assessing the predictive skills of the Bayesian Network through the unbiased iterative k-fold cross-validation procedure. Regarding the first comparison, the analysis considered the entire duration of three large storms whose return periods were 10, 16, and 25 years, and it was observed that the Bayesian Network correctly predicted between 64% and 72% of the impacts during the course of the storms, depending on the area analyzed. Importantly, this method was also able to identify when the hazardous conditions disappeared after predicting potential consequences. Regarding the Regarding the second validation approach, second validation approach, the k-fold cross-validation procedure was applied to the peak of a set of varying storms and it demonstrated that the predictive skills were maximized (63%–72%) when including three nodes as input conditions of the Bayesian Network. In the operational phase, the system was integrated into the architecture of a forecast and early warning system that predicts emergencies in coastal and port zones in Portugal, and the alerts are issued to authorities every day. This study demonstrated that the two-phase approach developed here can provide fast and high-accuracy predictions of erosion impacts. Also, this methodology can be easily implemented on other sandy beaches constituting a powerful tool for disaster management

Asymmetries in e+e−→ffˉe^+e^-\to f\bar{f} processes at ILC for models with an extra neutral vector boson Z′Z^\prime

Many extensions of the standard model predict the existence of extra neutral vector bosons, generically referred as $Z^\prime$. This boson may be discovered at the LHC but in this case it will be necessary to study the respective parameters in order to discriminate to which model it belongs to. This is a task for a much clean lepton linear collider as the future ILC. In this paper we develop an exemplary study of the capability of several asymmetries on and off $Z^\prime$ peak in discriminating among those extensions with (almost) no ambiguities.Comment: 27 pages, 9 figures. Version to be published in PRD. Title changed in the journa

Interaction of eukaryotic translation initiation factor 4G with the nuclear cap-binding complex provides a link between nuclear and cytoplasmic functions of the m7 guanosine cap

In eukaryotes the majority of mRNAs have an m7G cap that is added cotranscriptionally and that plays an important role in many aspects of mRNA metabolism. The nuclear cap-binding complex (CBC; consisting of CBP20 and CBP80) mediates the stimulatory functions of the cap in pre-mRNA splicing, 3' end formation, and U snRNA export. As little is known about how nuclear CBC mediates the effects of the cap in higher eukaryotes, we have characterized proteins that interact with CBC in HeLa cell nuclear extracts as potential mediators of its function. Using cross-linking and coimmunoprecipitation, we show that eukaryotic translation initiation factor 4G (eIF4G), in addition to its function in the cytoplasm, is a nuclear CBC-interacting protein. We demonstrate that eIF4G interacts with CBC in vitro and that, in addition to its cytoplasmic localization, there is a significant nuclear pool of eIF4G in mammalian cells in vivo. Immunoprecipitation experiments suggest that, in contrast to the cytoplasmic pool, much of the nuclear eIF4G is not associated with eIF4E (translation cap binding protein of eIF4F) but is associated with CBC. While eIF4G stably associates with spliceosomes in vitro and shows close association with spliceosomal snRNPs and splicing factors in vivo, depletion studies show that it does not participate directly in the splicing reaction. Taken together the data indicate that nuclear eIF4G may be recruited to pre-mRNAs via its interaction with CBC and accompanies the mRNA to the cytoplasm, facilitating the switching of CBC for eIF4F. This may provide a mechanism to couple nuclear and cytoplasmic functions of the mRNA cap structure

Advances in the synthesis of Homochiral (-)-1-azafagomine and (+)-5-epi-1-azafagomine. 1-N-phenyl carboxamide derivatives of both enantiomers of 1-azafagomine: leads for the synthesis of active α-Glycosidase inhibitors

- A new expeditious preparation of homochiral (-)-1-azafagomine, and (+)-5-epi-1-azafagomine has been devised. Stoodley´s diastereoselective cycloaddition of dienes bearing a 2,3,4,6-tetraacetyl glucosyl chiral auxiliary to 4-phenyl-1,2,4-triazole-3,5-dione, was merged with Bols protocol for functionalizing alkenes into molecules bearing a glucosyl framework. Homochiral (+)-5-epi-1-azafagomine was synthetized for the first time. Partial reductive cleavage of the phenyltriazolidinone moiety afforded new homochiral 1-N-phenyl carboxamide derivatives of 1-azafagomine. Both enantiomers of these derivatives were synthetized and tested, displaying a very good enzymatic inhibition towards baker´s yeast α-glucosidase. The molecular recognition mechanism of the 1-N-phenyl carboxamide derivative of 1-azafagomine by α-glucosidase from baker´s yeast was studied by molecular modelling. The efficient packing of the aromatic ring of the 1-N-phenyl carboxamide moiety into a hydrophobic sub-site (pocket) in the enzyme´s active site, seems to be responsible for the improved binding affinity in relation to underivatized (-)1-azafagomine and (+)1-azafagomine.We thank FCT for project funding PTDC/QUI/67407/2006 and FCT and FEDER for funding NMR spectrometer Bruker Avance III 400 as part of the National NMR Network. M.N.M. acknowledges the contract research program "Compromisso com a Ciencia" Reference C2008-UMINHO-CQ-03 and access to the Minho University GRIUM cluster

Influência do número de gemas, presença ou ausência de folhas e posição do explante na multiplicação in vitro da batata.

Avaliou-se a posição, presença ou ausência de folhas e número de gemas iniciais do explante na multiplicação in vitro da batata. O meio de cultura foi formado pelos sais e vitaminas de MS, acrescido de 100 mg L-1 de mio-inositol, 30 g L-1 de sacarose e 6 g L-1 de ágar. Utilizaram-se diferentes tipos de segmentos nodais (basais e apicais, com e sem folhas, contendo uma, duas e três gemas axilares). Após a inoculação o material foi mantido em sala de crescimento com temperatura de 25±2ºC, fotoperíodo de 16 horas e 19 ?E m-2 s-1 de irradiância por 32 dias. Para altura e número médio de brotações regeneradas, os melhores resultados foram obtidos com explantes oriundos da posição basal e com três gemas axilares. A taxa de multiplicação do material em cultivo foi maior nos explantes inoculados inicialmente com uma única gema, independentemente da posição do explante ser basal ou apical e, somente nos explantes basais a presença de folhas proporcionou taxa de multiplicação significativamente superior ao apical. Conclui-se que quando se trabalha com material vegetal heterogêneo, sob condições in vitro, as características iniciais dos explantes podem provocar variações na resposta final, causando erros na estimativa da multiplicação

Utilização conjunta de ferramentas neuronais e SIG na avaliação da inundação do porto e baía da Praia da Vitória

O HIDRALERTA é um sistema de previsão, alerta e avaliação do risco de galgamentos/inundação em zonas costeiras e portuárias, partindo da utilização de medições/previsões da agitação marítima para calcular o galgamento/inundação nessas zonas. O cálculo dos caudais médios galgados sobre uma estrutura marítima é efetuado através de ferramentas neuronais e/ou fórmulas empíricas, que não permitem definir a distribuição espacial desse caudal atrás da estrutura. Este artigo apresenta a aplicação ao porto/baía da Praia da Vitória, Açores, de um método expedito para modelar essa distribuição espacial, recorrendo a ferramentas SIG. Foi estabelecida uma relação entre a cota de inundação e o volume galgado de água através da utilização de um modelo digital de terreno. Este trabalho representa um primeiro passo na elaboração de um mapa de risco associado ao galgamento costeiro