Adubação nitrogenada em milho e capim-xaraés sob plantio direto e preparo convencional em sistema agrossilvipastoril.

O objetivo deste trabalho foi avaliar o desempenho agronômico das culturas do milho e do capim-xaraés (Urochloa brizantha 'Xaraés') em consórcio, cultivadas em plantio direto e convencional, em sistema agrossilvipastoril, com a aplicação de diferentes doses de nitrogênio em cobertura. O experimento foi conduzido em área de cultivo de milho com a espécie florestal mulateiro (Calycophyllum spruceanum). Utilizou-se o delineamento experimental de blocos ao acaso, com arranjo em parcelas subdivididas, com dois sistemas de manejo do solo (plantio direto e convencional com grade pesada) alocados nas parcelas e com cinco doses de adubação nitrogenada em cobertura (0, 50, 100, 150 e 200 kg ha-1 de N), nas subparcelas, o que totalizou dez tratamentos. A produtividade de grãos de milho respondeu linearmente à aplicação de N em área de plantio convencional. Em área de plantio direto, a dose de 165 kg ha-1 de N em cobertura foi necessária para a obtenção de produtividades satisfatórias. A adubação nitrogenada em cobertura na cultura do milho, até a dose de 200 kg ha-1 de N, não influencia o rendimento do capim-xaraés em consórcio nas entrelinhas, após a colheita do milho

On possible lower bounds for the direct detection rate of SUSY Dark Matter

One can expect accessible lower bounds for dark matter detection rate due to restrictions on masses of the SUSY-partners. To explore this correlation one needs a new-generation large-mass detector. The absolute lower bound for detection rate can naturally be due to spin-dependent interaction. Aimed at detecting dark matter with sensitivity higher than $10^{-5}$ event/day/kg an experiment should have a non-zero-spin target. Perhaps, the best is to create a GENIUS-like detector with both Ge-73 (high spin) and Ge-76 nuclei.Comment: latex, 5 pages, 3 figures. Talk given at the III International Conference on Non-accelerator New Physics (NANP'01), Dubna, 19--23 June, 200

Root-induced alterations of copper speciation in solution in the rhizosphere of crop species

As a prerequisite to establish trace metal phytoavailability, it is essential to determine trace metal speciation in the solution of the rhizosphere, where substantial alterations of physicalchemical properties (e.g. pH, Eh, organic matters) are induced by root activities. Investigations in the past decades were mainly dedicated to studying illustrative cases of how each individual rhizosphere process is able to influence trace metal speciation in solution. On a more integrative perspective, the present study aimed at investigating (i) the diversity of chemical modifications occurring in the solution of the rhizosphere of crop species cultivated on soils exhibiting a very wide range of physical-chemical properties and (ii) their consequent impact on copper (Cu) speciation in solution. Three plant species from three distinct botanical families, i.e. one graminaceous species, red fescue (Festuca rubra), two dicotyledonous species, tomato (Lycopersicon esculentum) and cabbage (Brassica oleracea), and 55 soils exhibiting a wide variety of physico-chemical properties (e.g. pH 4.4-8.2, 1-126 g Corg kg-1 , 6-1077 mg Cutotal kg-1 ) were selected for this study. Plants were grown using the RHIZOtest experimental design. This biotest consists in growing plants for two weeks in hydroponics, then for 8 days in contact with soil. Soils harvested from planted and unplanted devices are considered to be representative of rhizosphere and bulk soil, respectively. The solution of each rhizosphere and bulk soil was extracted with an unbuffered salt solution, and pH, concentrations of major ions and trace elements, dissolved organic matter (DOM), as well as the free Cu2+ activity were measured. The reactivity of DOM towards Cu was also estimated by modeling of Cu speciation, using the Humic Ion-Binding Model VII. Root activities induced variation in pH and in DOM concentration and its reactivity, thereby inducing substantial alterations of Cu speciation in solution. Fescue induced an overall alkalization of the rhizosphere that tended to be stronger as the bulk soil was more acidic. Conversely, tomato and cabbage induced an acidification or alkalisation of the rhizosphere depending on soil type. Surprisingly, the concentration of DOM tended to decrease in the rhizosphere, especially for soils initially exhibiting the highest DOM concentrations. This result could be explained by an increase in microbial activity in the rhizosphere leading to a higher rate of DOM mineralization. The reactivity of DOM varied in a complex pattern the rhizosphere , either increasing or decreasing compared to the bulk soil depending on soil properties and plant species. As a result of the drastic alteration of chemical properties in the solution of the rhizosphere and of Cu uptake by roots, the free Cu2+ activity was changed by up to three orders of magnitude in the rhizosphere compared to the bulk soil. Free Cu2+ activity tended to decrease in the rhizosphere for soil exhibiting the highest free Cu2+ activities in the bulk soil. Conversely, free Cu2+ activity increased up to 1 to 2 orders of magnitude in the rhizosphere for soil exhibiting the lowest free Cu2+ activities. In such soils, the decrease in DOM reactivity could explain the increase in free Cu2+ activity in the rhizosphere. Our results show a consistent picture of how root activities can substantially alter trace metal speciation in the rhizosphere in a wide range of soils and plant species. Among the rhizosphere properties relevant for trace metal biogeochemistry and phytoavailability, the characterization of DOM reactivity should deserve further attention. (Texte intégral

Luminosity measurements at LEP

Fast luminosity measurements are vital for the optimisation of the machine conditions needed for physics. At LEP this has been achieved since the startup by means of 16 small tungsen-silicon calorimeters measuring the rate of Bhabba scattering events. To increase the counting rate the detectors are placed close to the beams and mounted on collimator jaws. The rate of Bhabba scattering is calculated using the rate of coincidental detections of e- and e+ at both sides of the interaction point. The correction term arising from accidental off-momentum particle coincidence is calculated from the background rates. This technique could be successfully used at beam energies around 45 GeV since the correction term was small.Starting in '95 however, the energy of LEP has been increased up to 91.5 GeV per beam. In these conditions the background event rate almost doubles while the Bhabba cross section adopted and presented in this paper consists of checking the collinearity in the vertical plane of the particle tracks. This is obtained by measuring the vertical centre position of the showers inside the calorimeters using silicon strip detectors

The effect of copper toxicity on synergisms and antagonisms between nutrients in grapevine plants

Copper (Cu) accumulation in soils can induce toxicity and nutrient imbalances in several plant species. The aim of this work was thus to evaluate the effect of Cu toxicity on two grapevine rootstocks, Fercal and 196.17, and to elucidate if intercropping with oat can alleviate grapevine Cu toxicity using hydroponic trials and rhizobox experiments. The hydroponic trial revealed that Cu-induced root exudation was correlated with genes expression (VvPEZlike); furthermore the ionome analysis revealed that both mono- and intercropped L96.t7 rootstocks display a synergistic effect on Zn and Mn in the root tissues at high Cu concentrations. An increase of Zn and Mn in roots was also reported for the intercropped FercaJ rootstock at high Cu concentrations while an antagonistic relation was observed for root Zn in the monocropped Fercal rootstock. The rhizobox experiments further confirmed these results showing a different nutrient concentration depending on the rootstock and on the soil characteristics. lndeed, Cu availability is shaped by rhizosphere processes, which depend on soil properties and/or the co-cultivation of different plant species. The soil-based experiments revealed that nutrient availability and dissolved organic carbon including root exudates differ depending on soil properties and the rootstock rather than on the cultivation system, ln particular, we did not observe any apparent competition between the two plant species in the alkaline soil; on the other hand, in the acid soil, the intercropping revealed a beneficial etfect reducing the available Cu in the rhizosphere. Our results revealed that Fercal rootstock is able to take advantage from oat, while 196.17 seems disadvantaged by the intercropping system. Yet, even though the intercropping system seems to be a valuable tool to counteract grapevine Cu toxicity, the application of this agricultural practice has shown to be species and mostly soil type dependent and should be evaluated for each rootstock

Rendimento de milho e braquiaria com diferentes doses de nitrogênio em cobertura em sistema agrossilvipastoril no Acre.

O objetivo deste trabalho foi avaliar o rendimento produtivo das culturas do milho e Brachiaria brizantha cv. Xaraés consorciadas, cultivadas a diferentes distâncias de árvores nativas de mulateiro (Calycophyllum spruceanum Benth) e com aplicação de diferentes doses de nitrogênio em cobertura, em um sistema agrossilvipastoril no Acre. O delineamento experimental utilizado foi de blocos ao acaso, arranjado em parcelas subdivididas, com duas posições de amostragem (Perto da Linha e Distante da Linha do mulateiro) nas parcelas e cinco doses de adubação nitrogenada em cobertura (0; 50; 100; 150; 200 kg ha) nas subparcelas, totalizando dez tratamentos. Foram avaliados na cultura do milho a altura de plantas, teor de clorofila foliar e a produtividade de grãos e para forragem o acúmulo de matéria seca. Constatou-se que a produtividade do milho não é afetada pelo mulateiro aos quatro anos de idade e a adubação nitrogenada em cobertura até a dose de 200 Kg ha de N aumenta linearmente a produtividade de grãos. A pastagem formada apresentou acúmulo de matéria seca da forragem estatisticamente igual para todos os tratamentos, aos 90 dias após a colheita do milho

N2_2 and Xe Gas Scintillation Cross-Section, Spectrum, and Lifetime Measurements from 50 MeV to 26 GeV at the CERN PS and Booster

Beam parameters in CERN's Proton Synchrotron (PS) accelerator must be controlled (and measured) with tighter precision than ever before to meet the stringent requirements of the Large Hadron Collider (LHC) programme. A non-destructive beam profile measurement system would be a valuable diagnostic tool. To this end, we measured N2 and Xe gas scintillation absolute cross-sections and lifetimes for proton beam energies from 1.4 to 25 GeV, which should prove valuable in the design and construction of a gas scintillation profile measurement system. We also measured relative cross-sections for proton beam energies between 0.05 and 1.4 GeV

Improved sensitivity at synchrotrons using edge illumination X-ray phase-contrast imaging

The application of the X-ray phase-contrast ‘edge illumination’ principle to the highly coherent beams available at synchrotron radiation facilities is presented here. We show that, in this configuration, the technique allows achieving unprecedented angular sensitivity, of the order of few nanoradians. The results are obtained at beamlines of two different synchrotron radiation facilities, using various experimental conditions. In particular, different detectors and X-ray energies (12 keV and 85 keV) were employed, proving the flexibility of the method and the broad range of conditions over which it can be applied. Furthermore, the quantitative separation of absorption and refraction information, and the application of the edge illumination principle in combination with computed tomography, are also demonstrated. Thanks to its extremely high phase sensitivity and its flexible applicability, this technique will both improve the image quality achievable with X-ray phase contrast imaging and allow tackling areas of application which remain unexplored until now

Status of the HIE-ISOLDE project at CERN

The HIE-ISOLDE project represents a major upgrade of the ISOLDE nuclear facility with a mandate to significantly improve the quality and increase the intensity and energy of radioactive nuclear beams produced at CERN. The project will expand the experimental nuclear physics programme at ISOLDE by focusing on an upgrade of the existing Radioactive ion beam EXperiment (REX) linac with a 40 MV superconducting linac comprising thirty-two niobium-on-copper sputter-coated quarter-wave resonators housed in six cryomodules. The new linac will raise the energy of post-accelerated beams from 3 MeV/u to over 10 MeV/u. The upgrade will be staged to first deliver beam energies of 5.5 MeV/u using two high-$\beta$ cryomodules placed downstream of REX, before the energy variable section of the existing linac is replaced with two low-$\beta$ cryomodules and two additional high-$\beta$ cryomodules are installed to attain over 10 MeV/u with full energy variability above 0.45 MeV/u. An overview of the project including a status summary of the different R&D activities and the schedule will outlined.Comment: 7 pages, 12 figures, submitted to the Heavy Ion Accelerator Technology conference (HIAT) 2012, in Chicag