829 research outputs found
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In the last years many populations of anurans have declined and extinctions have been recorded. They were related to environmental pollution, changes of land use and emerging diseases. The main objective of this study was to determine copper sensitivity of the anuran of the Amazon Rhinella granulosa and Scinax ruber tadpoles at stage 25 and Scinax ruber eggs exposed for 96 h to copper concentrations ranging from 15 ”g Cu L-1 to 94 ”g Cu L-1. LC50 at 96 h of Rhinella granulosa Gosner 25, Scinax ruber Gosner 25 and Scinax ruber eggs in black water of the Amazon were 23.48, 36.37 and 50.02 ”g Cu L-1, respectively. The Biotic Ligand Model was used to predict the LC50 values for these species and it can be considered a promising tool for these tropical species and water conditions. Copper toxicity depends on water physical-chemical composition and on the larval stage of the tadpoles. The Gosner stage 19-21 (related to the appearance of external gills) is the most vulnerable and the egg stage is the most resistant. In case of contamination by copper, the natural streams must have special attention, since copper is more bioavailable.Nos Ășltimos anos foram registrados muitas extinçÔes e declĂnios de populaçÔes de anuros. Eles estavam relacionados com a poluição do ambiente, a mudanças no uso da terra e ao surgimento de doenças. O principal objetivo deste estudo foi determinar a sensibilidade dos anuros amazĂŽnicos ao cobre. Os girinos de Scinax ruber e Rhinella granulosa no estadio 25 e os ovos de Scinax ruber foram expostos por 96 horas a concentraçÔes de cobre entre 15 ”g Cu L-1 a 94 ”g Cu L-1. A CL50 -96 h dos girinos de Rhinella granulosa, dos girinos de Scinax ruber e dos ovos de Scinax ruber em ĂĄguas pretas da AmazĂŽnia foram 23,48; 36,37 e 50,02 ”g Cu L-1, respectivamente. O modelo do ligante biĂłtico foi usado para prever os valores de CL50 para essas duas espĂ©cies e pode ser considerado uma ferramenta promissora para essas espĂ©cies tropicais e para essas condiçÔes de ĂĄgua. A Toxicidade de cobre depende da composição fĂsico-quĂmica da ĂĄgua e do estagio larval dos girinos. O estadio 19-21 de Gosner (relacionados ao aparecimento das brĂąnquias externas) sĂŁo os mais vulnerĂĄvel e o estagio de ovo Ă© o mais resistente. Em caso de contaminação por cobre, os igarapĂ©s naturais devem ter uma atenção especial, uma vez que o cobre Ă© mais biodisponĂvel nesse ambiente
Avaliação agronÎmica de genótipos de bananeiras em condiçÔes subtropicais, Vale do Ribeira, São Paulo - Brasil
Microhabitats occupied by Myxomycetes in the Brazilian Atlantic Forest: Heliconiaceae inflorescences
Avaliação das cultivares de bananeira Prata-Anã, Thap Maeo e Caipira em diferentes sistemas de plantio no norte de Minas Gerais
EficiĂȘncia de fungos micorrĂzicos arbusculares isolados de solos sob diferentes sistemas de uso na regiĂŁo do Alto SolimĂ”es na AmazĂŽnia
AMIDO E HIPOCLORITO DE SĂDIO NO ENRAIZAMENTO IN VITRO DO ABACAXIZEIRO âGOLDâ E SEUS EFEITOS NA ACLIMATIZAĂĂO
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging
We present a measurement of the top quark pair () production cross
section () in collisions at TeV
using 230 pb of data collected by the D0 experiment at the Fermilab
Tevatron Collider. We select events with one charged lepton (electron or muon),
missing transverse energy, and jets in the final state. We employ
lifetime-based b-jet identification techniques to further enhance the
purity of the selected sample. For a top quark mass of 175 GeV, we
measure pb, in
agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let
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